With the progress of silicon integration technologies, visual information processing architecture has greatly been changed and eventually it can be integrated into a compact and yet high performance integrated circuits. In other words, the image processor is no longer considered as a desktop size bulky equipment but rather as one chip information processing module where photodetector and processing circuits are integrated, which is the VLSI vision chip. This paper discusses the architecture of the VLSI vision chip and some examples of high-speed image processing application are shown.

When W. Schaaffs developed X-ray flash machines after World War II at Siemens in Germany, he used spark discharges in layers of liquid between solid plates as a nonmilitary test object. W. Schaaffs discovered the so-called compression ring in 1947 during his experiments with spark discharges. This paper discusses the construction of triode X-ray flash tubes, the evolution of the discharge into the vacuum of the tube and the tubes characteristics depending on this mechanism. It will be found, that the special geometry of the tube shows an important influence on the discharge. The electrons will need a long time to reach the anode while positive ions are strongly accelerated near the anode. The duration of the x-ray flash is limited by the size and speed of the evaporated material from the anode. In the second part of this paper the spark discharge in a layer of liquid between solid plates is described. With this spark discharge it is possible to produce a shock wave in the liquid which finally moves to a vortex. Faster waves propagate in the plates at both sides of the layer. The plate waves induce a low pressure region in front of the ring and there it is possible to detect cavitation bubbles. The spatial arrangement of these bubbles in the layer of liquid between the solid plates depends on the excitation strength of the pulse waves in the plates. Their amplitude depends on the distance to the spark. Thus in a single X-ray flash picture it is possible to study the distribution of the cavitation bubbles for different excitation power. The spatial arrangement of the bubbles can show a periodic structure or it might be chaotic. X-ray flash experiments of this phenomenon will be presented. A model for the birth of cavitation bubbles will be shown. It explains how seeds of phase changes can be distributed in space under special conditions. This idea might also be valid for controlling the crystal growth.

AIRIX is an induction linear accelerator which will be used for flash radiography in Commissariat A L'Energie Atomique In France. Designed to produce an X-ray dose of some hundreds Rads at 1 meter with an X-ray focal spot size diameter of less than 2 mm (LANL-CEA DAM definition), this facility consists in a 3,8 MeV/2 kA pulsed electron injector and 15,4 MeV induction accelerator powered by 32 high voltage generators. A prototype of this accelerator, called PIVAIR, has been studied and realized in CEA CESTA near Bordeaux. PIVAIR is a validation step for AIRIX at 8 MeV. It includes an injector (3,6 MeV, 3,2 kA, 60 ns) and 16 induction cells supplied by 8 high voltage generators (250 kV, 70 ns). Two different technologies of induction cells have been tested (Rexolite insulator or ferrite Under Vacuum). We have chosen ferrite under vacuum cells technology after comparison of results on beam transport and reliability tests. A focusing experiment at 7.2 MeV of the electron beam has been achieved during summer 1997. We have begun to produce X-rays in October 1997. A dose level of 50 Rad at 1 meter has been achieved with an X-ray spot size diameter of 3.5 to 4 mm (LANL-CEA DAM definition). Static flash radiography of very dense object have been achieved from November 1997 until February 1998. We have been able to test in situ new kinds of very high sensitive X-ray detectors and to check they had reached our very ambitious goals: quantum efficiency at 5 MeV > 50% instead of 1% for luminous screens and film, sensitivity < 10 (mu) Rad (100 time more sensitive than radiographic luminous screens and films), dynamic range > 100, resolution < 2 mm. The AIRIX accelerator has been built in the CEA-MORONVILLIERS test site near Reims under an industrial collaboration with the THOMSON- CSF Company. It is housed in a reinforced concrete bunker and has an overall length of 60 meters. The 20 MeV electron beam has been focused on a 1 mm thick Tantalum target to produce an X-ray fluence of more than 300 Rads at one meter from the target. The result is a single radiograph of the device explosion under test with the high stopping power detector located in a blast protection set behind the device. In this communication we will present all these techniques which correspond to a significant effort of CEA begun in 1992. AIRIX facility will be available to run detonics experiments before end of 2000.

Presented in this paper is an outline of the R and D activities on high-speed video cameras, which have been done in Kinki University since more than ten years ago, and are currently proceeded as an international cooperative project with University of Applied Sciences Osnabruck and other organizations. Extensive marketing researches have been done, (1) on user's requirements on high-speed multi-framing and video cameras by questionnaires and hearings, and (2) on current availability of the cameras of this sort by search of journals and websites. Both of them support necessity of development of a high-speed video camera of more than 1 million fps. A video camera of 4,500 fps with parallel readout was developed in 1991. A video camera with triple sensors was developed in 1996. The sensor is the same one as developed for the previous camera. The frame rate is 50 million fps for triple-framing and 4,500 fps for triple-light-wave framing, including color image capturing. Idea on a video camera of 1 million fps with an ISIS, In-situ Storage Image Sensor, was proposed in 1993 at first, and has been continuously improved. A test sensor was developed in early 2000, and successfully captured images at 62,500 fps. Currently, design of a prototype ISIS is going on, and, hopefully, will be fabricated in near future. Epoch-making cameras in history of development of high-speed video cameras by other persons are also briefly reviewed.

In pulsed power technology high energy densities are generated either mechanically, electrically, magnetically, chemically or optically. Particularly interesting processes are met if energies are supplied by high power laser radiation. Lasers, however, are not only useful for inducing and controlling target effects, they also provide advanced tools for diagnostics, suited to the study of fast, even explosively developing events. According to present ISL activities, optical components (subject to radiation power densities up to the atmospheric propagation limit) are studied. Experiments, yielding data on thermodynamic parameters, refer to studies of the energy balance and conversion efficiencies from which further information is obtained on phase changes, ionization, etc. Additionally, the visualization of such processes allows to check theoretical models and numerical simulations. The combination of illuminating laser and CCD-cameras provides digital image formats with exciting capabilities of numerical image processing. For the investigation of specific effects, such as those induced by repetitively pulsed lasers, an optical laser sampling technique was developed, which (for quantitative evaluation) allows to convert fast supersonic motion into quasi-stationary slow motion. This was achieved by conventional low-cost videographic equipment. The characterization of laser-ablation-induced optical parameter changes was achieved by determining the modulation transfer function. A comprehensive overview of current coherent optical measurement techniques will be given and trends will be outlined.

In military research and development or testing there are various fast and dangerous events that need to be recorded and analyzed. High-speed cameras allow the capture of movement too fast to be recognized by the human eye, and provide data that is essential for the analysis and evaluation of such events. High-speed photography is often the only type of instrumentation that can be used to record the parameters demanded by our customers. I will show examples where this applied cinematography is used not only to provide a visual record of events, but also as an essential measurement tool.

A number of fundamental research projects devoted to combustion processes have been carried out during the last years in the Department of Heat Technology and Refrigeration of the Technical University of Lodz, Poland. The investigations under various conditions of combustion have been conducted with the following research facilities and equipment: (1) a drop tower with 1.2 sec of microgravity conditions and ca. 1 m³ volume of the experimental package, (2) a test rig with a rotating cylindrical vessel (combustion chamber) up to 6000 rpm, (3) schlieren devices of 300 and 150 mm diameter, including a compact system for experiments in the drop tower, (4) several specialized chambers for combustion of gas- and two-phase mixtures, (5) high speed photography equipment including a 500 fps camera. Some of the experiments and facilities are presented on 27.5 min long video and mentioned in this paper in a form of the editing list of the video. Some examples of abstracts of particular specialized publications are quoted.

Flash-X-ray is mostly used in terminal Ballistic studies. The diagnostics of the reaction and detonation behavior of high explosives are the domain of ultra high speed frame and streak cameras. With tricky arrangements of foils, rods, spheres etc. in and around the charge the detonation front or reaction strength can be also very well observed and analyzed with flash-X-rays. Examples of test setups for the diagnostics with FXRs of high explosive charges to measure the time jitter of detonators alone or with explosive trains in multi initiation systems, the change of the detonation velocity of mild detonation cords by different arrangements or by mechanical treatment, the initiability of boosters with mild detonation cords, the internal reaction behavior of high explosive charges at corner turning test, the flow of reaction products, enhanced by embedded foils, reaction strength around a charge in a corner turning arrangement and the reaction behavior in gap test investigations will be shown and highlighted.

Indoor detonations in buildings with several linked rooms present an important and complex problem. Experimental studies in small-scale models using Nitropenta charges of 0.5-g have been performed to obtain a database for indoor detonations in a multi-chamber system. Floor and ceiling of the model consist of a transparent material. This made it possible to visualize the flow field inside the structure. Pressure gages were installed in all rooms. The paper discusses the influence of the charge position as well as effects of venting holes in the detonation chamber. It also focuses on characteristics of the energy release and the related pressure effects if the system contains an inflammable material and the detonation provides mixing with air and initiates combustion.

Conventional ultra-high speed electronic framing cameras have typically employed either a multiplicity of image intensifiers and CCD cameras aligned on a common optical axis (example -- the Hadland 468). Alternatively, a single photo-cathode and a means of deflecting the resultant 'electron image' to differing areas on a phosphor screen which can then be recorded by a conventional CCD camera (example -- the Ultranac), shuttering being performed by the intensifier. These conventional techniques are powerful but inevitably lead to highly complex camera systems. The techniques described, center upon a new image intensifier construction. The photo- cathode of an otherwise standard generation 2 image intensifier, is fabricated in such a manner that separate portions or areas of the photo-cathode may be gated independently of others, creating in effect a multiplicity of separate 'intensifier' channels. Coupling this technique to a recently developed novel beam splitter plus a single large format CCD camera (covering all 'channels' simultaneously), has resulted in an extremely compact, rugged and flexible ultra high speed camera system. A further advantage of the technique is the simplicity by which advances in solid state camera technology may be exploited. These new techniques offer a new range of camera systems, allowing frame rates of up to 100,000,000 frames per second (fps) or more, of 4 to 136 independent frames with resolutions of up to 1000 X 1000 pixels per image with other user defined spectral filtering and or color options. Characterization of the true optical gating properties of the camera 'intensifier channels' operating in the nanosecond region is also quantified. Finally, example images and sequences are presented plus an overview of some of the new applications that these camera systems make feasible.

An 8 channel parallel readout CCD image sensor for high-speed imaging has been developed. The image area of this sensor is divided into 8 rectangular blocks, and the data of each block is read out through an independent amplifier. In the area where there is not photediode (PD) beside VCCD, the space of VCCDs is narrowed down to a HCCD block that is placed at the end of VCCDs, and amplifiers and their peripheral circuits are placed between the spaces of two HCCD blocks with parallel to makes amplifier properties uniform across channels. For VCCD high-speed transfer, VCCD bus line structure is used and VCCD slant structure is optimized by the computer 3D simulation. The pixel size is designed to be 11.5 micrometers X 11.5 micrometers , and amplifiers are placed close to FDA (Floating Diffusion Amplifier) with VCCD slant structure, which realized high sensitivity and large saturation.

High repetition rate intensified cameras having interframe times in the microsecond(s) range are needed for flow analysis measurements such as Particle Imaging Velocimetry (PIV) or Molecular Tagging Velocimetry (MTV). For these applications, the lower efficiency, fast decay P46 and P47 phosphors must then be used instead of the higher efficiency P20 and P43 phosphors. Previous literature provides only the time-resolved phosphor response. For very short interframe time imaging applications, a significant fraction of the previous frame's intensity can appear as a 'ghost image' in the trailing frame. Fast phosphors minimize this energy transfer into a second frame. Previous data show a dependence of decay time on exposure time for the P46. The P47 has been reported to decay a factor of 3 to 30 faster than the P46. The transferred total intensity as a function of the shutter repetition rate is measured for these two fast phosphors. They are compared with data published in previous papers. Neither phosphor under investigation behaves fully in accordance with these prior characterizations.

The value of high-speed imaging for making subjective assessments is widely recognized, but the inability to acquire useful data from image sequences in a timely fashion has severely limited the use of the technology. 4DVideo has created a foundation for a generic instrument that can capture kinematic data from high-speed images. The new system has been designed to acquire (1) two-dimensional trajectories of points; (2) three-dimensional kinematics of structures or linked rigid-bodies; and (3) morphological reconstructions of boundaries. The system has been designed to work with an unlimited number of cameras configured as nodes in a network, with each camera able to acquire images at 1000 frames per second (fps) or better, with a spatial resolution of 512 X 512 or better, and an 8-bit gray scale. However, less demanding configurations are anticipated. The critical technology is contained in the custom hardware that services the cameras. This hardware optimizes the amount of information stored, and maximizes the available bandwidth. The system identifies targets using an algorithm implemented in hardware. When complete, the system software will provide all of the functionality required to capture and process video data from multiple perspectives. Thereafter it will extract, edit and analyze the motions of finite targets and boundaries.

The old Cranz Schardin (C.S.) concept of multi-exposures high- speed visualization system has been reduced to the size of one CCD sensor. As a result of this concept, that have been called michrocam, integrates the advantages of both the Cranz Schardin systems and the modern numerical camera. Michrocam is a shadowgraph and schlieren visualization device. Thanks to this miniaturization, very high speed shadowgraphs and Schlieren can be performed not only in research laboratories but also in industrial environment. Moreover, the images are obtained through numerical standards directly manageable by any software of image treatment on a personal computer.

Recently, the number of commercially produced digital still cameras has increases rapidly. However, detailed performance of digital still camera had not been evaluated. One of the purposes of this paper is to devise the method of evaluating the performance of a new camera. Another purpose is to show possibility of taking a picture of a scientific high quality photograph with a camera on the market, and taking a picture of a high-speed phenomenon.

High speed Schlieren photography is a reliable means of visualizing small changes of refractive index resulting from density differences within a transparent media. Schlieren techniques are frequently used for investigating the aerodynamics of high velocity projectiles to confirm the formation of shock waves on leading edge surfaces so that optimum design performance can be achieved. Traditionally this type of investigation would have been undertaken using film cameras, however, improvements in image quality provided by the rapid development of intensified silicon based sensors and associated electronics has offered a reliable alternative, without the inherent difficulties in quantitative data extraction. The development of a high resolution sixteen image electronic camera system provides the researcher with versatile recording system that can be used to capture detailed image sequences at framing rates up to two hundred million pictures per second. The number of information points is maintained, irrespective of framing rate, making it ideal for recording the complexity of detail available from these sensitive Schlieren techniques. The high resolution images, which are displayed within twenty seconds of capture, flexibility of operation, and comprehensive analysis software provide fast reliable access to experimental data.

Many fast events are 3-dimensional but the most investigations, using high-speed cinematography, yield only to 2-dimensional explanations. The problem is that for a quantitative analysis of 3-D events, images taken in 2 different planes are necessary. Therefore, in the most test set ups for the investigation of 3-D events 2 cameras are used. To simplify the test set up and to improve the test method, 3-D supplements were developed for use by cinecameras and also by CCD cameras. The problems and the possible solutions for the development of such supplements are demonstrated. The analysis of 3-D pictures is possible with qualified PC programs. For their application, mostly marks have to be attached onto the test object, e.g. in crash tests. Therefore, this problem will also be treated.

A femtosecond synchroscan streak tube has been developed. In order to achieve femtosecond time resolution, followings have been adopted in the tube designing, i.e. high electric field application near the photocathode, plus high voltage application to the focusing electrode to reduce photoelectron transit time spread in the focusing region, and anode electric potential settled as low as possible to obtain very high deflection sensitivity for sweep. The tube has been designed by computer simulation of electron trajectory and the theoretical time resolution has been carried out to be approximately 520 fs. Based on the above designing, a prototype tube has been fabricated and evaluated. Time resolution of approximately 660 fs has been experimentally obtained at the synchroscan frequency of approximately 80 MHz.

We propose a method to improve the shuttering characteristics of an ultra high-speed camera that consists of a proximity focused image intensifier (PFII) with an external transparent electrode (ETE). When the shuttering time of several tens of picoseconds is considered, the time delay by the propagation of the shuttering pulse can not be disregarded, and this time delay causes the problems in the system's simultaneity. First, the time of which the image was recorded is different by the place. Second, the time in which the photoelectron reaches the micro channel plate (MCP) input surface is different. For our research, the second problem mentioned above poses an obstacle. To utilize the nonlinear operation of the MCP for smaller gating time, it is necessary that each electron reaches the MCP in same time. Our proposal is to compensate for this second problem by controlling the electric field between the photocathode and the MCP. This is achieved by optimizing the shape of the electrode of the ETE. We show that the variance of arrival time is reduce from 30 ps to 5 ps using numerical analysis by FDTD method.

This paper describes a network-oriented, long-recording-time high-speed digital video camera system that utilizes an HDD (Hard Disk Drive) as a recording medium. Semiconductor memories (DRAM, etc.) are the most common image data recording media with existing high-speed digital video cameras. They are extensively used because of their advantage of high-speed writing and reading of picture data. The drawback is that their recording time is limited to only several seconds because the data amount is very large. A recording time of several seconds is sufficient for many applications. However, a much longer recording time is required in some applications where an exact prediction of trigger timing is hard to make. In the Late years, the recording density of the HDD has been dramatically improved, which has attracted more attention to its value as a long-recording-time medium. We conceived an idea that we would be able to build a compact system that makes possible a long time recording if the HDD can be used as a memory unit for high-speed digital image recording. However, the data rate of such a system, capable of recording 640 X 480 pixel resolution pictures at 500 frames per second (fps) with 8-bit grayscale is 153.6 Mbyte/sec., and is way beyond the writing speed of the commonly used HDD. So, we developed a dedicated image compression system and verified its capability to lower the data rate from the digital camera to match the HDD writing rate.

In the scanning detector we propose the new system for improving spatial resolution by making sensitivity distribution of a detecting element vary. This can be simply done by only adding the filter with sensitivity distribution in front of a detecting element without requiring the higher density of equipment. In our laboratory, the plasma electron density distribution measurement by the holographic interferometry in far-infrared region has been proceeded. As one of the infrared detection material, we chose HgCdTe, and it was used as a scanning detecting element. As a verification of this system, we added the infrared filter in the front of HgCdTe, and measured the spatial resolution using a knife edge. For the method for calculating Modulation Transfer Function (MTF) from Edge Response Function (ERF), we also propose the new technique that we name the virtual test chart method. In this technique, we simulate the response corresponded to periodic bar patterns from ERF, and calculate the contrast ratio from this response. From the result of measurement that added the infrared ray filter, the validity of this system was shown. By the simulation and the experiment, the optimum sensitivity distribution was obtained in this system.

Two different approaches to image tube computation, numerical optimization and design being developed in GPI (Russia) and BIT (China) are presented and comparatively discussed as applied to a Russian-made streak image tube.

An ultra-high speed and high repetition shutter camera with a unique shutter tube has been studied. The shortest shutter time of 14.5 ps, 480 ps, 84 ps, is experimentally obtained at the shutter repetition rate of 1 kHz, 4 MHz, 80 MHz, respectively. Moreover, the camera can be operated in modulation mode using sinusoidal sweep voltage of a few ten volts. Modulation larger than 17% has been obtained at modulation frequency of 4.2 GHz.

The speed to read out the data of a CCD camera limits applications for high speed videography. If the size of a picture is reduced and if parts of the sensitive area of a CCD are used to store the pictures before reading out, an picture sequence can be stored on a CCD and is available as a standard tv-signal. Cavitation bubbles in an ultrasonic wave have been investigated with a 100 kHz frame rate. Faster frame rates are possible, when a computer is used to separate the lines of agglomerated pictures which are produced by an array of cylinder lenses. An illuminated line is shifted electronically to the neighbored dark field and the next lines can be illuminated. Five pictures in 1 microsecond are realized. An ultrasonic plane wave in a transparent material is an array of cylinder lenses which moves with some mm/microsecond. Four to five pictures with good quality can be taken in a period of the sound wave. A sequence of 200 ns in total is demonstrated with a CCl₄ shutter. With a laser modulator crystal a shutter time of 8 ns for each picture was realized. Ideas for faster shutters are presented.

In this paper, we discuss the required specifications, APS (Active Pixel Sensor) technology, and possible problems to be overcome with next-generation CMOS image sensors for digital high-speed video photography. A custom-designed image sensor with parallel-readout, high-speed-operation and other functions, is needed to develop an advanced high-speed video camera, realizing higher frame rates and producing pictures of proper resolution. The CMOS image sensor can be developed at lower cost than CCD sensors, and its peripheral circuits can be integrated on a single sensor chip. Table 1 describes specification and performance of one of the custom CMOS image sensors currently in use for a digital high-speed video camera. This type of CMOS sensor is also called as 'Passive Pixel Sensor.' The pixel structure of this sensor is very simple, but it requires the Current-to-Voltage Converter (also called as Trans-Impedance amplifier or Pre-Amplifier). This is because the output signal current from the sensor is very small and needs to be amplified.

A streak tube with high dynamic range and with high spatial resolution characteristics over the useful length on the photocathode has been developed. In order to achieve high dynamic range, the electromagnetic focusing method has been adopted. Two coils are applied as magnetic focusing lens to improve peripheral spatial resolution. As a result, the dynamic range is 100,000 at the time resolution of 100 ps. The spatial resolution over the useful output area is better than 201p/mm. The effective length of the photocathode is 20 mm max.

A high dynamic range streak camera, which can handle a larger number of photoelectrons without suffering either time resolution or linear input-output characteristic, has been developed. This streak camera can handle more than 1,000,000 photoelectrons at a time resolution of 100 ps. This camera has a large format photocathode of 17 mm length. The large photocathode allows a larger capacity of information in the spatial domain as well as larger number of channels when multiple-fiber input is used. This streak camera can achieve an ultimate time resolution of better than 3 ps at reduced photoelectron number. The sweep time windows are 500 ps to 1 ms in 20 ranges.

The Paper addresses the general concepts of what we consider as images and how we see them. The way in which the eye and brain see and interpret images is a vital part of the analysis of photonic records. While the eye is a remarkable organ, it does have limitations which have extremely important ramifications on the way images are analyzed and obtained. Also discussed are the ways in which the photographer can attempt to present the analyst with the most useful image by adapting the way in which the image is obtained and presented. It makes the point that the photographer and the sponsor/analyst must work closely together to obtain the best results from each project. Brief mention is made of the ways in which imaging may progress in the future, but emphasizes how ultimately we only appreciate these images, however produced, when they are carried to our brains via the eyes.

A Multi-Point velocity interferometer system for any reflector (VISAR) has been developed which can simultaneously measure velocity versus time histories of two to eight points by double delayed legs or two to sixteen points by single velocity sensitivity on a target or different objects during dynamic compression. A single-frequency laser beam is divided into two to eight or sixteen individual beams that are transmitted into an experimental device by incident fibers to illuminate measured points. Diffusely reflected laser beams from different measured points are separately collected by fiber detectors and guided by signal fibers into a common 'push and pull' interfering cavity with the same delay etalon to interfere. This not only simplifies the system structure and the experimental operation, but also eliminates the system error among measured points and makes the system almost as small in volume as that of a single-point VISAR. The Multi- Point VISAR possesses all the advantages of the traditional single-point VISAR as well as the temporal and the space resolution ability. We have used it to monitor velocity histories of several points on a target in a few explosion experiments, and good experimental results were obtained.

All-optical switching has been demonstrated in bacteriorhodopsin based on excited-state nonlinear absorption. A probe laser beam at 640 nm corresponding to the O-state absorption maximum is switched due to a strong pulsed pump laser beam at 570 nm, that corresponds to the maximum ground state absorption. We have studied the effect of variation in pulse width and in small signal absorption coefficient on the switching characteristics. The switching time decreases as the pulse width of the pump beam decreases and the small signal absorption coefficient increases. The switching contrast depends mainly on the peak pumping intensity.

A new system for making hologram easily and/or rapidly has been developed, by using solvent vapor for automatic development of photo-conductor plastic hologram (PPH) at initial setting place of the photosensitive plate in an open room, and by aligning all optical units on an optical rail base for reducing vibrational effect. The new optical system is compact and easy to operate and can be used as an adequate device for real time holographic interferometry. In experiments, interferometric frames of rapid variation of air density distributions by temperature distributions in flame and the vibration mode of surface of radio-speaker have been taken in the photography as the real time holographic interferometry. It is recognized that the new system for making hologram easily and rapidly can be used effectively in the real time interferometric measurement.

For detailed investigations of processes and phenomena in the flow of compressible fluids, it is sometimes necessary to apply more than just one flow visualization technique as each method has its own characteristic strengths and weaknesses. In the case of flows with a low degree of repeatability, it may become mandatory to perform these multiple visualizations simultaneously, i.e., within the same experiment at identical or at least almost identical instants. This contribution describes how two interferometry methods can be coupled with a color schlieren technique in order to obtain simultaneously the density distribution and the density gradients within a flow field. The resulting systems are slightly more complex than a single visualization apparatus, but they can provide an unprecedented wealth of information about the flow field.

In order to study the metal target surface in-place deformation induced by the laser beam or other ones effecting upon, three kinds of measuring dynamic in-plane deformation techniques by means of a laser speckle, which are the speckle field time sequence processing (that is the optical flow analysis of speckle pattern), the digital speckle pattern processing (in fact, it is a kind of pattern or picture enhancement technique), and the digital speckle pattern correlation metrology, have been studded and developed. The latter, the correlation metrology, has been made a big progress: better precision and higher processing speed.

For analyzing combustion and melting phenomena, it is necessary not only to measure the deformation and its acceleration of the applied object which is being deformed at a high speed and under high temperature, but to detect the temperature of the object and to know the temperature distribution over the object. By the recent development in electronics, including new solid-state image sensors such as area CCD and C-MOS sensors, and the progress of image processing techniques, new imaging radiometers have been developed which two-dimensionally acquire objects in motion at a high speed and under high temperature, and present the temperature distribution over the object immediately. The popular pseudo-color thermal imager only indicates the relative differences of radiance from the measured object by assigning different colors, but does not show the correct temperature, because their calculated temperature is radiance temperature whose radiation is measured at a single wavelength. In this paper, we present the concept of ratio temperature measurement which measures radiance from the object at two wavelengths and presents 'truer' true temperature than radiance temperature. We have developed a new high speed imaging/ratio temperature radiometer by using the Photocam-RGB high-speed video camera readily available on the market. Here we present the outline of our experiments.

The experimental system measuring the X-ray spot size for the 12 MeV LIA is given in this paper. By means of one-time discharge, the system adopts the sharpness-edge and big-hole imaging simultaneously, thereby acquiring the size of the X- ray spot and the shape of the spot. Using the density distribution of the image and combining with numerical calculating, the space distribution of spot intensity is simulated. At the same time, the modulation transfer function for the 12 MeV LIA X-ray imaging can be obtained with the system.

Tentative study on high-photon-energy quasi-x-ray-laser generator by forming plasma x-ray source is described. The generator employs a high-voltage power supply, a low-impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash x-ray tube. The high-voltage main condenser is charged up to 60 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The flash x-rays are then produced. The x-ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As the electron flows from the cathode electrode are roughly converged to the copper target by the electric field in the tube, the plasma x- ray source, which consists of metal ions and electrons, forms by the target evaporating. Both the tube voltage and current displayed damped oscillations, and their peak values increased according to increases in the charging voltage. In the present work, the peak tube voltage was much higher than the initial charging voltage of the main condenser, and the peak current was about 25 kA with a charging voltage of 60 kV. When the charging voltage was increased, the plasma x-ray source formed, and the characteristic x-ray intensities of K-series lines increased. When the plate target was employed, we observed high-intensity characteristic x-rays from the axial direction of the linear plasma x-ray source. In the case where the rod target was employed, we detected higher-intensity characteristic x-rays.

Ultra-fast x-ray imaging is of great importance for diagnosing laser-driven inertial confinement fusion (ICF) plasmas. Typical required spatial and temporal resolutions are 10 micrometer and 10 ps, respectively. We have developed variety of one- (1D) and two-dimensional (2D) image sampling technique for ultrafast time-resolved x-ray imaging with x-ray streak cameras. Moire imaging of an x-ray-backlit target has been developed as 1D image sampling of an objective with 1D repetitive structure with a spatial resolution of 5 micrometer for use in experiments on hydrodynamic instabilities in laser- accelerated targets. With 1D sampling of repetitive 2D images, a multi-imaging x-ray streak camera (MIXS) with temporal- and spatial-resolutions of 10 ps and 15 micrometer, respectively, has been developed and successfully utilized for diagnosing uniformity and heating process of the imploded core plasmas. Two types of spectroscopic applications of the MIXS have been developed. One is multi-channel MIXS (McMIXS) which has three MIXS channels with various spectral responses for time- resolved 2D temperature measurement. Another is monochromatic MIXS (M-MIXS) for temperature, density and material mixing measurement, in which monochromatic images with Bragg crystals are coupled to MIXS. Finally, 2D image sampling of a 2D image on an x-ray streak camera (2D-SIXS) was also developed.

In this paper, we have analyzed and computed the scattered radiation background and direct radiation on flash radiography. We also have detected the direct radiation to scattered radiation ratio and related factors, such as construction of sample, dimension of collimation hole, distance between sample and X-ray source, distance between sample and film. A few rules have been established. Analytical semi-quantitative formulas on ratio of direct to scattered radiation have been given.

The radiographic characteristics and the applications of an improved high-photon-energy stroboscopic x-ray generator are described. This generator is primarily designed in order to increase the maximum photon energy of the pulse x-rays and is composed of the following essential components: a thyratron pulse generator, a high-voltage transformer having a ferrite core with a maximum output voltage of 300 kV, a sequence controller, a DC power supply for the cathode (filament), and an x-ray tube. The main condenser of about 50 nF in the thyratron pulse generator is charged up to 15 kV, and the electric charges in the condenser are discharged repetitively to the primary coil of the transformer. Because the high- voltage pulses from the secondary coil are then applied to the x-ray tube, repetitive harder x-rays are produced. The x-ray tube is of a triode having a hot-cathode that is primarily driven at the temperature-limited current region. In this triode, because the grid is connected to the cathode, this tube is driven as a diode. The tube voltage roughly increased in proportion to the charging voltage, and the maximum value was about 300 kV. Thus, the maximum photon energy had a value of about 300 keV. The tube current was primarily regulated by the filament temperature and had values of less than 2 A. The x-ray output displayed almost single pulses, and the width of the first pulse was about 300 ns. The maximum repetition rate was about 1 kHz, and the dimension of the x-ray source had values of about 3.5 X 3.5 mm. The high-speed radiography was primarily performed by both the delayed and the multiple- shot radiographies using a new computed radiography (CR) system.

Small amount of iodine contrast material in the small vessels can be efficiently detected by monochromatic synchrotron radiation (x-ray) tuned at just above k-edge of iodine (33 KeV). However, the serious disadvantage of the system is a high cost for the facility to obtain synchrotron radiation (x- ray). We are trying to apply a plasma x-ray source for this purpose. In this system, the high voltage main condenser is charged up to 60 KeV by a power supply. The electric charges in the condenser are discharged to the tube after triggering the cathode electrode. For a cerium plasma target, a highly intensified K(alpha) and K(beta) characteristic x-ray of cerium (34.6 KeV and 38.3 KeV) was produced, as bremsstrahlung x-ray was absorbed and converted into fluorescent x-ray. Plasma x- ray source might be an alternative of monochromatic synchrotron radiation for small vessel radiography.

The tentative experiment for producing low-photon-energy quasi-x-ray laser using a capillary is described. This flash x-ray generator was improved in order to increase the x-ray intensity and to produce high-intensity characteristic x-rays by forming the linear plasma x-ray source. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, a turbo-molecular pump, and a radiation tube with a capillary. A high-voltage condenser of 0.2 (mu) F in the pulse generator is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. In the present work, the chamber is evacuated by the pump with a pressure of about 1 mPa, and the carbon anode and cathode electrodes are employed to produce K(alpha) characteristic x-rays. The diameter and the length of the ferrite capillary are 2.0 and 29 mm, respectively, and both the cathode voltage and the discharge current displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were -9.9 kV and 4.4 kA, respectively. The pulse durations of the x-rays were nearly equivalent to those of the damped oscillations in the voltage and current, and their values were less than 20 microseconds. In the spectrum measurement, we observed the carbon K(alpha) line.

The radiogprahic characteritics of the condenser-discahrge stroboscopic x-ray genrator and its application to high-speed radiogprahy are described.This gnerator employs a coneser- discharge medical x-ray gnerator in conjunctionwith a new grid-control unit and consists of the following major componets: a high -voltage control unit, a condenser unit having a Cockcroft circuit,a grid-control unit, a high- voltage grid-control unit,a nd a rotating-anode x-ray tube unit.The main condesner of about 500 nF in the unit is charged up to 120 kV by the circuit and the electric charges inthe condene are dischargd to the triode by the grid control unit i9n conjunction with a hgih-voltage grid-control unti The highv-otalgd grid-control unit is employed inorder to insulate the negative hgih-voltage grid and acathode electrods from th ehgihs-peed grid control unit with almost the ground potnetial. Inthis gnerator, th anode and cathode lectrodes ar applied tohigh-voltages with maximumvalues of +60 kV and -60 kV, respectively. Although the tube voltrage decased during the discharging for gnerating x-rays, the maximum vlaue was equivlaent to th eitnital charging vortlag eof th emiain condenser. Th3 amsximu values of the tub ecurrent and the repetiton rat3 awer about 0.5 A and 32 kHz, respectively. The pulse widthof the x-rays ranged from 0.01 to 1.0 ms, and the maximumshot number ahd a vlaue of 32. At a constant filament (cathode) tmerpature,the x-ray intensity incrased accordign to incrases in teh charging voltage and toincrases in the duration and the maximum intensity with a duration of 1.0 ms and a charging voltage of 100 kV awas 0.66 (mu) C/kf at 1.0 m from the -ray source.The dimensiosn sof the focal spot had values of about 1 X 1 mm, and both the inner and outer triggering for produicng pulse c-rays acan be employed. The hgih-speed radiogrpahy was primari9ly performed by temultpe- shot radiogprhay using a new computed radiogprhay (CR) system in conjuctiown tiht ehcomuter-dispaly sysem with an operationsyste of Windows NT Workstation 4.0.

The radiographic characteristics of the condenser-discharge stroboscopic x-ray generator and its application to high-speed radiography are described. This generator employs a condenser- discharge medical x-ray generator in conjunction with a new grid-control unit and consists of the following major components: a high-voltage control unit, a condenser unit having a Cockcroft circuit, a grid-control unit, a high- voltage grid-control unit, and a rotating-anode x-ray tube unit. The main condenser of about 500 nF in the unit is charged up to 120 kV by the circuit, and the electric charges in the condenser are discharged to the triode by the grid control unit in conjunction with a high-voltage grid-control unit. The high-voltage grid-control unit is employed in order to insulate the negative high-voltage grid and cathode electrodes from the high-speed grid control unit with almost the ground potential. In this generator the anode and cathode electrodes are applied to high-voltages with maximum values of +60 kV and -60 kV, respectively. Although the tube voltage decreased during the discharging for generating x- rays, the maximum value was equivalent to the initial charging voltage of the main condenser. The maximum values of the tube current and the repetition rate were about 0.5 A and 32 kHz, respectively. The pulse width of the x-rays ranged from 0.01 to 1.0 ms, and the maximum shot number had a value of 32. At a constant filament (cathode) temperature, the x-ray intensity increased according to increases in the charging voltage and to increases in the duration, and the maximum intensity with a duration of 1.0 ms and a charging voltage of 100 kV was 0.66 (mu) C/kg at 1.0 m from the x-ray source. The dimensions of the focal spot had values of about 1 X 1 mm, and both the inner and outer triggering for producing pulse x-rays can be employed. The high-speed radiography was primarily performed by the multiple-shot radiography using a new computed radiography (CR) system in conjunction with the computer- display system with an operation system of Windows NT Workstation 4.0.

Tentative study on the flash ultraviolet generator for high- speed microscopy in the atmosphere is described. The ultraviolet generator for fundamental studies consists of the following essential components: a high-voltage generator, a high-voltage main condenser, a thyratron, and a mercury-xenon lamp. The high-voltage condenser is charged up to about 14 kV, and the electric charges in the condenser are discharged to the lamp by closing the thyratron. The flash ultraviolet rays including visible lights are then produced. The radiation intensity increased according to increases in the electrostatic energy in the condenser by increasing the condenser charging voltage. The cathode voltage (- 1 times the tube voltage) and the discharge current were measured by a high-voltage divider and a current transformer, respectively. The peak cathode voltage increased according to increases in the charging voltage, and the value with a charging voltage 14 kV was about -14 kV. When the charging voltage was increased, the tube current increased, and the peak current had a value of less than 0.35 A. The output of ultraviolet rays including visible lights was detected by a pin diode, and the duration was less than 1 microsecond.

We have in the past used several types of optical probe lenses for delivering and collecting laser light to an experiment for laser velocimetry. When the test surface was in focus, however, the collected light would fill mostly the laser fiber rather than the collection fiber(s). We have designed, developed and used for 8 years nested-lens probe assemblies that solve this problem. Our first version used a commercial AR-coated glass achromat, which we cored to remove the inner fourth of its area. The core was then reinserted with its optical center offset from that of annulus by an amount slightly less than the separation between the laser and collector fibers. The laser and collector fibers are placed in contact with each other behind the lens and have NA values of 0.11 and 0.22, respectively. Because most of the collected light now focused on the collection fiber, this system was far superior to the single lens systems, but was laborious. For the last five years we used injection-molded acrylic aspheric nested lenses, which are inexpensive in quantity and require little labor to install into a probe. Only an azimuthal rotation and positioning of the fiber plane are needed to incorporate the plastic lens into a probe. Special ray-trace codes were written and used to design the lens, and many iterations by the molder were required to develop the injection processing parameters to produce a good lens, since it was thick for its diameter. These probes have real light collection efficiencies of 75% of theoretical, work well over a wide range of distances, with collection depths of field matching theory. The lenses can take 100 watts of pulsed power many times without damage, since the lens is designed so that reflections from the lens surface do not focus within the lens. The collection fiber size is designed to work with our manybeam velocimeter facility reported in a previous Congress, where the collection NA times collection fiber size exceeds the acceptance of the velocimeter. The Doppler-shifted light enters the collection fiber with angles between 0.11 and 0.2, with little light in the 0 to 0.11 NA region. However, the manybeam velocimeter uses just the light in the 0 to 0.11 NA range, except when we link two analyzer tables together. A slight amount of mode scrambling of the Doppler shifted light converts the light into a uniformly filled NA equals 0.2 angular range before entering the velocimeter analyzer table. We have expended seven hundred plastic nested lenses in various experiments. The most recent version of the fiber cable assembly will be shown. Six situations will be discussed where multiple reflected frequencies were observed in experiments, illustrating an advantage of the Fabry-Perot vs. the VISAR method.

For the quantity and quality of data recorded by the use of High-Speed-Photography and Videography, light plays an important role. Beside the basic requirements concerning illuminance, spatial uniformity and light modulation, the efficiency in respect to the sensitivity of the high-speed imaging sensor needs to be considered. On this subject the paper will focus on the effective illumination for the latest technology of high-speed video systems. The application of high-speed imaging at vehicle safety tests goes more and more into details. Seat bracket -- leg room -- steering column -- knee restraint -- safety belt buckle -- headlining -- etc. -- are components and areas that today could be reached by small camera heads. The second part of the paper will concentrate on applicable lighting systems for those 'shady sides.' Today's crash test technology is looking for best correlation to actual accident situations on the road. This leads to various test configurations along with the requirement for adaptable lighting systems. The final part of the paper will show some realized conversions of this task.

In this paper, we report the characterization of self-mode- locking femtosecond Cr:forsterite laser, pumped with Nd:YAG laser, generating 36 fs pulse at 1246 nm with 280 mW output power and also research the influence of the crystal cooling temprature vs. output power.

The composition of residual gases in streak tubes has been measured. The outgassing at supply of electrical voltage to the streak tube, at heating of Cr₂O₃ layer and at glass melting were investigated. The EBI fluctuations at pressure of 2 X 10^-8 Torr and 10^-6 Torr in streak tubes were examined.

A Cook-off test is an experiment to investigate the sensitivity and response of an explosive subtonic to high temperatures. A steel cylindrical Cook-off tube is filled with the explosive material under investigation. During the Cook- off test, the Cook-off tube will be heated up to several hundreds of degrees and, upon explosion, the rate of change of the diameter of the Cook-off tube is monitored to obtain information about the reaction process in the tube. To detect these expansion velocities, TNO has developed a system based on Fiber Optic interferometer. This system includes a Sagnac interferometer and a Mach-Zehnder interferometer. Part of the fiber loop of each interferometer is wrapped around the tube and is indicated as the sensing fiber. The change in the length of the sensing fiber is measured by analyzing the interferometric signals. The phase of the Sagnac interferometric signal is proportional to the rate of change in length of the sensing fiber, while the phase of the Mach- Zehnder interferometric signal is proportional to the absolute length change of the sensing fiber. The simplest method to analyze the interferometric signal is counting the fringes as a function of time. A more dedicated signal-processing scheme is proposed to obtain additional information. This scheme is designed for interferometers with 3 phase shifted output signals. The output signals from both the interferometers were recorded by a Digital Signal Analyzer (DSA). The signal to noise ratio was found to be sufficient. We have carried out several Cook-off experiments with the explosive Comp. B. for different configurations of the Cook-off tube, difference in the reaction process can indeed be observed. One or more oscillations in the expansion velocity of the tube were found at the start of the expansion process. As far as known, the presence of these oscillations has never been reported before. A discrepancy between the results of the two interferometer systems was observed. This is probably caused by the application of two different sensing fibers. A configuration applying a single sensing fiber for both interferometer systems is proposed.

With limited spatial and temporal resolution of video recording camera, it is very difficult task to analyze object motion with higher accuracy. In addition, target object or target points of object in one-frame can be hardly recognized automatically in ordinary two-dimensional video recordings. If correlation or template matching methods is used to detect object position, initial object area or template should be decided manually. So fully automatic detection process is difficult. But with linear scan camera (LSC) utilizing line- image sensor, object position detection can be done easily with much higher accuracy. This article describes this feature of LSC in motion analysis. First d-value is introduced to evaluate correlation of two line images. This d-value is calculated in quarter pixel width for higher accuracy. Object displacement between given two-line image can be decided by monitoring this d-value. Steep drop of d-value means match of lines and higher correlation. Because d-value increases as line separation becomes bigger, this variation should be checked simultaneously for consistency. Typically over about 100-line separation this value increases, so pivoting line (template line) should be changed. Selecting suitable combination of two lines based on d-value will be important for overall accuracy of time-displacement analysis. Two lines should be selected to decide pixel shift where spatial quantum error is minimum. Suitable to line images can be selected by searching less d-value. Prior to that, two-dimensional d-value table should be made. Then one-pass trace of suitable two-line selection is carried out for time-velocity analysis. Fully automatic analysis method of position detection with LSC was proposed. To estimate object displacement, d-value was introduced and its validity was proved experimentally. In addition, by selecting suitably separated two points, resultant velocity at middle point can be much accurate than direct differentiation of time-displacement data.

Most of recording surfaces of rotating mirror cameras is a cylindrical surface with a circular cross section fitted the inherent transcendental image locus, But now, the circular substituted for the transcendental curve is not necessary because of a great deal progress of manufacturing these transcendental curves; therefore, designing the advanced recording surfaces can be put into effect: the fine recording surface on which both the defocus magnitudes and uncertainty of writing speed are minimum, the non-defocus recording surface, and the constant writing speed recording surface.

A new, inter-discipline area of scientific research known as Femtosecond Photoelectronics combines investigations on femtosecond lasers, physics of photoemission, classic and NEA- photocathodes, electron optics and computer modeling, vacuum technology, gas mass-spectrometry, image data readout and acquisition, scientific instrumentation. The main goal of these researches is to create diagnostic techniques and tools for direct recording 1D and 2D images of high-speed events occurring within X-ray to IR spectral range with femtosecond time resolution and with sensitivity capable to detect tens of photons in each spatial resolved element. Investigations provided during last 40 years in tubes/cameras/diffractometers designing and their applications in experimental physics will be presented.

Ablative acceleration properties of laser-driven foil plates (Al, 10 and 18 micrometer-thick and 1 to approximately 2 mm in diameter) have been studied experimentally at laser irradiance from 30 to 400 GW/cm². Push-pull type VISAR (Velocity Interferometer System for Any Reflector) was utilized for the measurement, but an optical recording system was developed to provide sub-nanosecond time resolution. For the 18 micrometer- thick Al foil irradiated at 360 GW/cm², ablative accelerations up to terminal velocity of about 10 km/s within 30 ns has been determined with a velocity uncertainty of approximately 2%. The acceleration rate detected in the experiments is (0.2 to approximately 0.6)X 10¹² m/s², which is about 10¹¹ times of the acceleration by the gravity.

High-speed holographic microscopy is applied to take three successive photographs of rapidly bifurcating cracks. A crack propagates in a PMMA specimen at a speed more than 600 m/s, and bifurcates into two cracks in the observation area at the center of the specimen. The position at which the crack bifurcates is controlled by varying the tensile stress applied to the specimen. When it bifurcates, the fast propagating crack is recorded as three holograms. The holograms reconstruct the real images of the crack, which are photographed through a conventional microscope. From the photographs, crack speed before and after bifurcation is obtained. Crack speed after bifurcation is slightly lower than that before bifurcation. Crack opening displacement (COD) is also measured along a crack both before and after bifurcation. The COD before bifurcation is proportional to square root of the distance from the crack tip. After bifurcation, the COD of a mother crack is proportional to square root of the distance from the nominal tip of the mother crack. However, the CODs of two branch cracks are not always proportional to square root of the distance from each of the crack tips.

This reports documents the baseline development of high-speed laser photography based assessment technique to determine effects of material resistance to puncture or fracture. A series of ballistic experiments were performed to at the Dynamic Event Imaging Laboratory at the Munitions Directorate, Air Force Research Laboratory site at Eglin, AFB, Florida. These experiments were performed to assess the effectiveness of laser photography to document the formation and propagation of cracks in composite materials with and without electromagnetic loading. These experiments were the first fully operational use of a novel and unique experimental capability for high-speed digital laser photography. This paper details the development of the experimental procedures and initial results of this exciting new tool. This report documents the experiments performed and the instrumentation developed along with recommendations for additional research.

The characterization of near nozzle dense sprays and axisymmetric gas jets using X-ray flash techniques is presented. Flash radiography and X-ray induced fluorescence imaging (X.I.F. imaging), using a flash X-ray developed at GREMI, offer two complementary diagnostics particularly efficient in high pressure conditions. In this work, a compact flash X-ray device is used to freeze fluid motions. Single shot radiographs of argon jets and water sprays expanding in ambient air have been performed. Radial density profiles were measured and quantitative density measurements have been extracted for argon, nitrogen-argon mixture and water jets, using flash X-ray radiography. UV fluorescence emissions due to X-ray excitation of the jet species were imaged on a gated intensified CCD camera.

It had been reported that for KCl the B1 - B2 phase transition occurs under shock and static compressions, but, the measured transition points showed large scatter. In this study, the Hugoniot-measurement experiments were performed on KCl single crystals in the pressure range up to 50 GPa to obtain the informations about the phase transitions and equation of state. The Hugoniot parameters were measured by the inclined- mirror method using a mirror-rotating type streak camera and a pulsed dye laser or Xenon flash lamp, combined with a powder gun or two-stage light gas gun. The Hugoniot-elastic limits were found to be very small. The anisotropic phase transition points (2 - 2.5 GPa) were observed.

A streak spectroscopy system was constructed for the measurements of luminescence or absorption spectra of condensed matter under shock compression. This system consisted of a compact long-pulsed dye laser, a spectrometer and an image-converter streak camera with an image intensifier. The laser consisted of a doubled-elliptical pump cavity, two xenon-flash lamps and a high voltage electrical- pulse source. The measurement experiment of luminescence spectra of ruby under shock compression was performed in the pressure range above the Hugoniot-elastic limit.

In this work the dynamics of anisotropic local melting of monocrystalline and implanted silicon at different regimes of light pulse irradiation was investigated. The results of in situ investigation of local melting of monocrystalline silicon were carried out for the first time using special long-focus microscope and high-speed camera. The time dependences of the density and sizes of local molten regions were systematically measured. We explain the increasing of the size of LMRs during short time by the superheating of the semiconductor in the solid state with respect to the equilibrium melting point. Due to superheating conditions are arisen to overcome the barrier for the formation of the liquid phase nuclei. The dynamics of anisotropic local melting of implanted silicon was investigated using several optical methods and special diffraction gratings. The intensity of diffraction picture depends on the contrast of this periodical structure, i.e. from difference of crystalline and amorphous fragments of gratings. The dynamics of diffraction effectivity during and after the power light pulse was registered using high-speed camera. Three qualitative stages: solid-state recrystallization, local melting and liquid-phase recrystallization were observed experimentally.

The propagation of streamers on a surface of a solid insulator (hard glass) vertical or parallel to an electrode axis in a point-plane gap in perfluorocarbon (PFC) liquid, has been observed in detail, by using a high speed schlieren method. Especially, the effects of the point polarity and the existence of the solid insulator on the streamer propagation are investigated and also the creepage discharge in PFC liquid is compared with one in transformer oil.

It is shown that the simulation problems originated in femtosecond photoelectronic imaging in the beginning of 80s resulted in the development of a new aberration approach called 'the tau-variation technique.' The approach proves to be most fruitful for computer electron optics of non- stationary electromagnetic fields, and at the same time allows unifying the aberration theories of narrow and wide beams. The results illustrating new features of 'ELIM/DYNAMICS' Package specially oriented to the problems of femtosecond imaging are considered, and some aspects of the unsolved computer problems closely connected with femtosecond photoelectronic imaging are thereupon outlined.

When the illumination wavelength is comparable to the object size, one is in the Mie scattering regime. In this regime geometrical optics breaks down because of diffraction effects, and image data must be interpreted on the basis electromagnetic wave theory. Mie scattering problems are difficult to solve because the full vector form of Maxwell's equations must be solved subject to the appropriate boundary conditions, without the benefit of the short wavelength approximation. In this paper we present the essentials of Mie scattering theory, introduce algorithms for computing Mie scattering, and show how Mie scattering concepts can be used to image fast-moving microparticles by visible light.

Optical diagnostic techniques including interferometry, electronic streak photography, and transient x-ray diffraction are used to study the dynamic material response to shock loading by direct laser irradiation and impact by laser- launched plates. The Los Alamos Trident laser is one of several lasers that have been used to generate shocks of 10 Kbar to several Mbar in single crystal and polycrystalline materials. Incorporating optical velocity interferometry (line-VISAR and point-VISAR) with transient x-ray diffraction can provide a complete understanding of the dynamic material response to shock compression and release. Laser-launched flyer plates provide an ideal method to generate one- dimensional shocks in materials. The quality of the one- dimensionality of the launch and acceleration of plates is evaluated by line-imaging VISAR. The line-imaging VISAR images the fringes along a line across the diameter of the plate. Each fringe maxima and minima provide acceleration and velocity information at the specific point on the plate. By varying the fringe constant, number of fringes and fringe spacing on the plate, detailed experimental data can be obtained. For our experiments, most plates are 3-mm diameter and accelerated to 0.2 - > 6 km/sec.

An interferometric CT technique is developed to observe three- dimensional phenomena in shock tube experiments, and is applied to investigate three-dimensional features of shock waves and vortices discharged from a square open end. A small duct model is introduced in the test section of the shock tube, and is rotated around its central axis to change the observation angle in order to obtain the finite-fringe interferograms from multi-directions. The CT images of the density distribution are obtained with good quality by carefully selecting the projection data within the limited ranges of the incident shock Mach number M_i and the frontal shock position. The rotation angle is changed from 0 degree to 90 degrees in an interval of 5 degrees. For M_i equals 1.50, the three-dimensional nature of the distortion of vortices and the shape of secondary shock wave are clearly illustrated by pseudo-color images of the density distribution and isopycnic surfaces. The CFD images exhibit a good agreement with the CT images.

This paper describes some applications of image-intensified CCD camera systems to high-speed photography of radiation behind strong shock waves in low-density air to get two- dimensional images of total radiation and spatial-resolved spectra in shock tube experiments. The resultant images of total radiation are shown for incident shock waves and shock reflections on a wedge. Some two-dimensional flow features are clarified for these shock wave phenomena. A couple of CCD camera systems are applied to simultaneous observation of the total radiation and its spatial-resolved spectra along the tube axis, giving us a clear understanding for the spatial relationship between them.

The investigation of attenuation of shock waves propagating over complex geometries is an important and fundamental topic of shock wave research. However, previous studies have been mostly for two-dimensional and relatively simple geometries. In this study, the result of shock wave attenuation over an array of spheres is visualized quantitatively by sequential holographic interferometry in a 60 mm X 150 mm diaphragmless shock tube with very repeatable performance. Interferograms have been re-arranged in time order so as to present an animated display. This dynamic display allows one readily to understand the development of complex shock wave interactions. For comparison two cases were examined: arrayed spheres and arrayed cylinders. It is revealed that for identical initial conditions and blockage ratio, shock waves attenuate more quickly in the case of the arrayed spheres than in arrayed cylinders.

The application of electronic speckle pattern interferometry (ESPI) to the visualization of a typical high-speed compressible flow is investigated. ESPI is an interferometric technique that has established itself as a reliable alternative to holographic interferometry in the measurement of small displacements and of vibrations, and is increasingly being used in flow visualization. It can instantly and in real time produce interferometric images in digital form on a video screen, with no photographic processing being required. In this paper two flows are examined, the one a low speed flow of a thermal plume arising from a hot soldering iron, for which real-time visualization is achievable; and the other single frame imaging of a shockwave emerging from a small round open- ended shock tube. ESPI is shown to be a valuable tool in the visualization of compressible flows, and a good alternative to holographic interferometry in obtaining quantitative density data about a flow field. A method for obtaining interferograms with finite fringe-width is presented. The main benefit of using ESPI for flow visualization is that the interferometric image is immediately accessible for viewing on a monitor, so avoiding the tedious photographic holographic reconstruction process. Advances in camera technology are fast overcoming its disadvantage, low image resolution.

In the present work, interaction of flame kernels with shock waves generated by spark discharge has been studied using a plane or a cylindrical shock wave reflector fixed to a combustion chamber. The ignition unit was designed to produce capacitance sparks whose duration was less than 1 microsecond. Schlieren photographs show that the flame kernel development with the cylindrical reflector is initially suppressed by shock-flame interaction. Afterwards the surface area of the flame kernel with the cylindrical reflector exceeds that without reflector. This result is also confirmed in the experimental results on ignition probabilities obtained from measurement of OH radiation emitted by the flame kernel. As for the plane reflector, flame kernel development is promoted in particular for reflectors placed close to the spark gap. The calculated pressure and temperature profiles explain the shock suppression for the cylindrical reflector.

A varicose-profile, thin layer of heavy gas (SF₆) in lighter gas (air) is impulsively accelerated by a planar, Mach 1.2 shock, producing Richtmyer-Meshkov instability. We present the first measurements of the circulation in the curtain during the vortex-dominated, nonlinear stage of the instability evolution. These measurements, based on particle image velocimetry data, are employed to validate an idealized model of the nonlinear perturbation growth.

The paper reports an experimental study of the interaction of initially disturbed converging and diverging cylindrical shock waves with cylindrical interfaces and the resulting Richtmyer- Meshkov instability. Experiments were conducted in an annular vertical diaphragmless shock tube, in which cylindrical soap bubbles filled with He and SF₆ were placed co-axially in its test section. In order to the clarify effects of initial disturbances, 10 mm dia. pins were installed in the annular section, 92 mm from the shock tube's test section and before the 90 degree smooth bend at the top of the shock tube. The inner ends of the pins were rounded to ensure completel sealing with the inner wall of the low pressure channel. Weak disturbances in the converging cylindrical shock waves were produced by inserting the pins. Double exposure holographic interferometry was used for quantitative visualization of the interfacial instability and the subsequent mixing between the interface gases. It is known that the lower mode numbers of disturbances are dominant near the converging center, therefore experiments with mode eight and mode four disturbed converging shock waves were performed and the effects of weak waves behind the shock wave on the interfacial growth rates were clarified.

The investigation of shock reflection and shock diffraction phenomena upon a wedged concave reflector produced by a planar incident shock wave has been done in the shock tube facility of Institute of Aeronautics and Astronautics, National Cheng- Kung University. The experiment proceeds upon three wedged concave reflectors models the upper and lower wedge angles arrangement of them are (50 degrees, 50 degrees) - 35 degrees, 35 degrees) and (50 degrees, 35 degrees), respectively. They were tested at Mach numbers of 1.2 - 1.65 and 2.0. On the first reflector, following the regular reflection on the 50 degree-wedged surface by the incident shock wave, a Mach shock diffraction behavior has been observed as shock moves outward from the apex of the reflector. On the apex of the reflector, it behaviors as a sector of the blast shock moving on a diverging channel. On the shadowgraph pictures it has been observed there exists a pattern of gas dynamics focus upon the second reflector. The Mach reflection from the 35 degree- wedged surface as being generated by the planar incident shock wave, on which the overlapping of the two triple points from both wedged surface offers the focusing mechanism. The shock interference, which proceeds by the Mach shock reflection and the regular shock diffraction from the reflector, generates a very complicate rolling-up of slip lines system. On the third reflector, the mixed shock interference behavior has been observed of which two diffraction shocks from concave 50 degree-wedged surface and 35 degree-wedged surface interfere with each other. The measurement of the peak pressure along a ray from the model apex parallel to incident shock direction indicates that the measured maximum pressure rising is larger near the apex of the reflector. Considering the measured maximum pressure increment due to the reflection shocks indicate that the wave strength upon large apex angle reflector is greater than it is upon small apex angle reflector. However, as considering the measured maximum pressure increment following the diffraction shocks, the results show that due to the focusing process upon (35 degree, 35 degree) reflector, it is of the largest increment.

In this paper, the recent work on computational flow visualization is reported, which is done by simulating optical flow visualization based on the principle that as light passes through flowfields, its phase and direction are changed due to variations of the refractive index induced by non-uniform density in the flow field. Numerical schlieren and interferogram are constructed for three cases. The research shows that these results can be used to assist high-speed photography in visualizing shock wave phenomena more clearly and validating numerical results more reliably.

It is well known that the transition criterion nearly agrees with the detachment criterion in the case of strong shocks, two-dimensional, and pseudosteady flow. However, when the shock wave diffracts over a wedge whose angle is below the detachment criterion, that is, in the domain of Mach reflection, precursory regular reflection (PRR) appears near the leading edge and as the shock wave propagates, the PRR is swept away by the overtaking corner signal (cs) that forces the transition to Mach reflection. It is clear that viscosity and thermal conductivity influences transition and the triple point trajectory. On the other hand, the reflection over concave and convex wedges is truly unsteady flow, and the effect of viscosity and thermal conductivity on transition and triple point trajectory has not been reported. This paper describes that influence of viscosity over convex and concave corners investigated both experiments and numerical simulations.

In the Shock Wave Research Center, Institute of Fluid Science, Tohoku University, a streak camera system has been used to study high-speed phenomena associated with hypervelocity flow conditions. In the different facilities available, including the expansion tube, different test conditions can be produced for the study of the shock layer around bodies. In certain extreme conditions, the flow is in non-equilibrium and the radiation inside the shock layer is strong enough to be measured by existing spectroscopic techniques. Analysis of the spectra can provide information on the properties of the gas and can be used to validate numerical models. In the present study, time-resolved spectroscopy has been carried out in order to investigate the useful test time of the expansion tube, a very important parameter in the process of calibration of this facility. A spectroscopic system consisting of an Action Research spectrograph of 500 mm focal length, a streak unit (Hamamatsu Photonics) and a CCD camera has been used to measure time-resolved spectra down to microsecond time scales. The system is also equipped with a lens-coupled intensifier of high dynamic range.

This paper reports the results of shock wave loading on two oil droplets positioned in tandem. These oil droplets were suspended one after the other inside the test section of a 60 mm X 150 mm shock tube. They were attached to thin wires that kept their initial position constant. The droplets had an initial diameter of about 1.7 mm, their height was about 3 mm. The droplets shape resembled that of a tear drop. The initial distance between the two wires was 5 mm. A shock wave of Mach number 1.27 in atmospheric air impinged upon the droplets. The corresponding Weber number and Reynolds number were 3,600 and 25,300, respectively. Double exposure holographic interferometry was employed to visualize the flow field around the droplets. Interferograms were taken at various times during the breakup process in order to analyze the interaction between the shock wave and the oil droplets. Due to the high viscosity of the oil droplets their breakup mode was different from that of a water droplet for this Weber number. Stripping type breakup typically occurs for water droplets at this weber number, however the breakup mode of these droplets resembled that of a bag and stamen which usually occurs at much lower Weber number in water droplets.

In this study, unsteady propagation of high-pressure shock waves in PMMA and polyethylene specimens was first observed. Shock velocity decreases with the propagation distance for almost all cases, but the rate of decay process may depend on the material, shock strength and propagation distance. To observe the shock decay process, a high-speed photographic method was developed. The results obtained in this study may be closely related to the shape of the shock Hugoniot compression curve for these materials. Furthermore, stress relaxation occurring behind the wave front and its development with propagation are considered to have a close connection with the above results. Some of the data are presented and discussed compared with the Hugoniot and relaxation structures.

Visualization of the detached shock wave that forms ahead of a blunt body flying at hypersonic Mach number using electrical discharge technique is a simple and convenient technique to measure the stand-off distance experimentally in an hypersonic shock tunnel. In this technique a thin sheet of electrical discharge generated between a point electrode attached to the wall of the test section and a line electrode embedded on the model surface reveals the position of the shock wave around the body in hypersonic flow. In this paper we present the details of this technique and sample results obtained for typical body shapes tested in HST2 shock tunnel at a freestream Mach number of 5.75. The detached shock waves in front of the test models are clearly visualized using this technique. The shock stand-off distance estimated based on the numerical results for a large angle blunt cone obtained using a commercial CFD code match well with the experimentally measured value. These results clearly demonstrate the suitability of the electrical discharge technique for visualizing the flowfields in hypersonic testing facilities having very short test times.

Shock wave interaction with a rotating circular cylinder is numerically and experimentally investigated. It is shown that the transition from regular reflection to Mach reflection on the lower surface of a rotating cylinder where cylinder motion is the same as the incident shock motion, is more quickly promoted than that on the upper surface. Numerical calculations solving the Navier-Stokes equations using extremely fine grids further reveal that the reflected shock transition from RR yields MR is either advanced or postponed depending on whether or not a surface motion favors the incident shock wave.

The investigation of self-ignition dynamics followed by combustion has an essential significance for the organization of working cycle in internal combustion engines. The parameters of the process are influenced by the geometry of reactive volume, specific features of the generation of heat release centers, as well as gas-dynamics consequences of the propagation of chemical reaction fronts (formation of the pressure and/or shock waves in reactive volume). Registration of explosive processes using pressure transducers does not provide sufficient information on the localization and dynamics of self-ignition centers. Also unacceptable are the standard radiation detectors due to distortions connected with scattering. Two variants of visualization of the phenomena accompanying self-ignition hydrogen-containing combustible mixtures now are used: (1) Cranz - Schardin spark chamber and (2) powerful laser light source and projection of the image to a film located inside the rotating mirror chamber. In the present work the results of the application of two above- mentioned variants of visualization for the self-ignition investigation are presented.

The paper describes the temperature measurement system based on the double-wavelength silicon-germanium photodiode. The sensitive element is the Si-Ge photodiode of sandwich structure with silicon layer covering germanium substrate. The photodetector was applied to the emission/temperature measurements in different explosion tests: closed volume gaseous combustion, initiation of detonation due to shock focusing, and burst of solid-state explosives.

In recent years we have devoted our efforts to the studies on the various shock processing techniques using explosives for the objectives of gaining materials with the good properties. Those techniques include the punch of pipes, shock consolidation of metallic and ceramic powders, explosive welding of amorphous ribbon on the steel or copper substrate, explosive engraving for the art objects and explosive forming of shells and spheres, and the improvement of the permeability of wood by shock wave. However, to a specific processing technique, it needs to control the shock wave for meeting the demands of that processing purpose. One important control is how to increase the strength of underwater shock wave. Therefore, we propose the following method to converge the underwater shock wave by putting a piece of detonating cord in a spiral way. First, the assignment of the spiral shape of detonation was determined from the geometrical consideration and the basic features of the detonation cord itself. Second, the converging process of the underwater shock wave from the explosion of such designed shape of detonating cord was photographically observed by using the high speed camera in the framing form. The spiral shape with the 100 mm distance from detonating start point to the center of the spiral (indicated by r₁) was selected. They were amounted together with the electric detonator and the detonating cord. The photographs confirm that the underwater shock wave moves toward the spiral center in a convergence way. Third, the pressure nearing the spiral center was measured experimentally by means of the pressure transducers. The distance, D_h, between the detonating cord and the transducer was set to be 272 mm. Compared to the case that the detonating cord was placed in straight way, the maximum pressure in the case with the spiral shape is verified to be unchanged, but the impulse, however, is much improved. This reason may be due to over- greatly set D_h. When the distance D_h was set to 50 mm, the pressure measurement was made again and as a result, the large pressure value was record. Compared to the straightly placed detonating cord, it is shown that 3 times higher peak pressure is available in the spiral detonation cord. The results demonstrate that in a small range the pressure of underwater shock wave is indeed converged and higher pressure value is obtained.

Previous studies on deflagration-to-detonation transition (DDT) have been carried out in detonation tubes, where the role of the solid wall of the tube is important. It is necessary to eliminate the wall effect for the investigation of three-dimensional DDT. Small explosive charges with charge masses of a few milligrams are useful for ignition purposes to generate spherical shock waves without wall effects. However, it was observed in our experiments that the shape of the shock waves is not always spherical. In a detonable mixture, the shape of the wave fronts often has many conical shock protrusions behind which the main wave front expands more rapidly. The conical waves are generated by fragments, which penetrate the main spherical shock wave. Regions of high turbulence are built up behind the fragments. From the results it can be inferred that DDT occurs in these turbulence regions, inducing locally a higher velocity of the following portion of the main wave front. In this study, we conducted tests of spherical detonation waves to investigate three- dimensional DDT. Time-resolved shadowgraphs and holographic interferograms were taken for visualization.

In this paper, a 1-D and a 2-D axially symmetrical hydrodynamics codes are used to numerically simulate the various characteristics produced by the explosions of spherical Tetral charges with a radius of 3.27 cm exploding at 4000 m underwater and near the water surface (at 10 cm underwater) respectively. Different figures obtained from deep-water explosion or from near-water-surface explosion such as the law of shock wave travelling in water, the explosion product-water interface time history, the effect of discontinuity of water and the height of water column are all presented here. The full physical process of shaped charge metallic jet penetrating water and separated metal targets is also shown in this paper. The velocity decrease of the metal jet travelling in water and the scales of the penetrated holes in targets made by metal jet given by numerical simulations have good agreement with experimental ones. Therefore, it's a very effective to use numerical simulation method to investigate on the problem of underwater explosion, and it can give some figures, which are very difficult to obtain from experiment.

On the common circumstances the detonation of explosives has a steady propagation rate and can be satisfactorily explained by Chapman-Jouguet's theory on this phenomenon. Hence, this type of detonation is more frequently called the Chapman- Jouguet (C-J) detonation. The detonation properties such as pressure, density, and temperature, of the detonation products are often characterized as the C-J values of the explosive that represent the corresponding maximums of the variables in the detonation products. However, when an explosive is initiated in some special ways, for instance, high velocity impact of a flyer plate, a strong detonation with properties higher than C-J values will be induced in the explosive. This strong detonation is what we called the overdriven detonation of explosive. The use of overdriven detonation expects to provide much more work to the surrounding matter than does the common C-J detonation. In order to have a basic knowledge of this detonation phenomenon, we designate an experimental set- up for the purpose of acquiring the overdriven detonation in high explosive. The set-up uses a circular metal plate accelerated by a piece of cylinder explosive (donor) to impact another cylinder explosive (acceptor), inducing a detonation wave in the acceptor explosive. The donor explosive used is PBX (85%wt HMX and 15%wt binder) explosive cylinder that has the detonation velocity of 7.84 km/s and the detonation pressure of 25.24 GPa and the acceptor explosive cylinder is SEP (65%wt PETN and 35%wt paraffin) with the detonation velocity of 6.97 km/s and the detonation pressure of 15.9 GPa. The impactor is the copper disc with the same diameter of the donor explosive and 1 mm and 2 mm thicknesses respectively. The detonations occurred in the acceptor explosive from the impact of copper flyer were recorded by the high-speed camera (IMACON 790). The photographs make us possible to estimate the detonation velocities from the distance and time data on them. In addition, we also make a numerical visualization on this phenomenon using a 2-D Lagrangian hydrodynamic code. The calculation, to somewhat extent, reproduces the consequences of the current experimental results.

Examining the X-Ray radiographs of the linear collapse and the jet formation processes it can be seen that the space between the end of the straight and continuous jet and the slug is usually filled with small particles that do not look like an integral part of the jet. This section of the jet is named the Appendix. This is the transition zone between the jet and the slug. The experimental evidences as well as the numerical simulation results are presented. It was found that the Appendix is a stand-alone section of the jet, as it can be characterized by a specific collapse angle and velocity gradient. In addition, the Appendix breaks up time is much shorter than that of the main jet and the average velocity difference between each two particles in the Appendix is much higher than that of the main stream of jet droplets. By conducting a detailed 2D numerical simulation it was found that there is a way to define this transition zone. By defining this zone the tail of the jet is also well defined. As the tail of the jet is well defined it is easier to design more efficient shaped charges. Once the lowest jet velocity needed for a given penetration is known the tail of the jet can be designed to meet this speed.

Fiber Optic sensors are found to be very suitable for explosion and shock wave measurements because they are immune to Electromagnetic Interference (EMI). In the past few years, TNO has developed a number of sensor systems for explosion and shock wave measurements in which the optical fiber is a vital component. This paper presents a survey of these optical measurement systems using fiber optics. The basic design of these systems, the test configurations and the experimental results are presented.

Spark discharge in water generates a spherical shock wave and a bubble that contains water vapor, with each center at a gap between electrodes. The bubble repeats the movement of the expansion and contraction. An impulsive pressure wave also arises at each transition from the contraction to the expansion of the bubble. In case that a rigid wall exists near the bubble, the bubble moves toward it keeping the expansion and contraction and then a water jet is formed toward the wall. The jet exerts the impulsive pressure on the wall. In case that the bubble is near the surface of water, it moves as if a rigid wall existed just below it and then the downward water jet is also formed. We are interested in the relationship of the movement of the bubble to the effect of the pressure caused by the under-water discharge near the surface of water. We are also interested in whether there are some differences between the following two cases as to the effect of pressure; one case is that the bubble exists near the surface of water and its movement is affected by the surface, another case the movement of the bubble is not affected by the surface of water for the sake of enough large distance between the bubble and the surface. In this study, impulsive pressure waves caused by the under-water discharge in above two cases are observed by means of a transducer or their schlieren photographs are taken with an image converter camera, and observations are examined.

The donor and the acceptor charges are arranged into the water with the interval. The donor charge has a cylindrical geometry with 30 mm diameter and 50 mm long. The acceptor has a disk form with 100 mm diameter and 10 or 5 mm thickness. Composition B is used for both of the donor and acceptor charges. The propagation processes of underwater shock waves from the top end of acceptor charge along the axis of charges are taken by the image converter camera under the intervals of 10, 15, 20 and 25 mm. In the case of 10 mm thick acceptor charge, the velocities of the underwater shock wave are the almost the same up to the interval of 20 mm. However, in the case of 25 mm the underwater shock wave has remarkable low velocity compared to the other cases. In the case of 20 mm interval, the velocity of the underwater shock wave in the case of the 5 mm thick acceptor is slower than that of 10 mm. Furthermore, the numerical simulations are conducted. The reaction rate law of the high explosive is a phenomenological model that is proposed by Lee and Tarver. The results of the optical measurement and numerical simulation demonstrate a good agreement.

This paper presents the study on the application of explosive welding technique to the field of the urgent repair of the gas and water pipe networks. The essential parameters related to the explosive welding are scrutinized from the point of view of the minimizing the damage to the steel pipe after welded explosively with a flyer plate. The emulsion explosive is contained in a rectangular hard-paper box whose bottom is the flyer plate with 100 mm length, 25 mm width and 1.5 mm thickness. The flyer motions of the flyer plates accelerated by emulsion explosive are observed by high-speed photography from the side and front view of the flyer plate. The damage to the pipe by the flyer plate is discussed with the results of the observation of flyer motion and explosive welding test under various experimental conditions. Moreover, one way to control the motion of the flyer plate is proposed. We put a PMMA buffer block into the explosive. The flying process of flyer plate is calculated by the finite different scheme based on the ALE method. The effectiveness of this method is demonstrated by the experimental and numerical studies.

Deflagration to detonation transition (DDT) is a phenomenon that is difficult to observe experimentally because of the inherent stochastic nature of shock and flame acceleration processes that produce the thermodynamic and gasdynamic conditions required for DDT. The shock tube however provides an attractive means of establishing or modifying these conditions independently of chemical reactivity parameters. In the present paper results are presented from an experimental study of turbulent flame acceleration and eventual transition to detonation following the perturbation of a curved reaction front (spheroidal flame bubble) by a shock wave. Of particular interest is how an initial flame kernel, propagating with a laminar burning velocity of few meters per second or less, can be enhanced by shock processes to the point where a transition to detonation occurs, without the influence of turbulence producing obstacles. This is compared with a more conventional flow, but again generated by a shock wave, through a grid scenario where the flame propagated into a pre-established turbulent field. The events were recorded using spark Schlieren photography as the primary diagnostic technique.

Micro air blasts are generated over planar and corrugated surfaces, at stand-off distances of 4 and 11 mm, by focusing a 1.38J, 18 ns Nd:Glass laser pulse in a tiny spot of 300 micrometer diameter, under ambient conditions. This triggers the breakdown of air at optical frequencies with subsequent formation of laser plasma, which generates an outward propagating spherical micro-blast wave. The velocity of this wave decreases as time elapses, since the energy deposition is finite, with reference to both space and time. The evolution, propagation and subsequent reflection of the spherical micro- blast wave, from planar and corrugated surfaces are experimentally investigated, using double exposure holographic interferometry. One planar surface and four surfaces with varying degree of surface corrugations are used in this study. Mach reflection of the blast wave is observed at a stand-off distance of 4 mm over a planar obstacle while only regular reflection is visualized at an 11 mm stand-off distance. However only regular reflection is observed at both stand-off distances, in the case of corrugated surfaces.

In order to verify the predictions of the 2D high Atwood number potential flow model for the evolution of the shock wave induced Richtmyer-Meshkov instability, shock-tube experiments were performed with a single-mode perturbation and two competing bubbles as the initial conditions. The experimental results were compared to theoretical model and to numerical simulation. In the present work the dependence of the instability on the Atwood number and the dimensionality of the instability were investigated in a shock tube apparatus. A high speed schlieren photography system were used to monitor the evolution of the unstable contact surface. Different Atwood numbers were achieved by using different gases. The results of those experiments were found to be in very good agreement with the predictions of theoretical model and numerical simulation. These results verify the key elements of the Atwood number scaling of the bubble-merger model used for the prediction of the multi-mode bubble and spike front evolution at all Atwood numbers. The dimensionality investigation of the instability evolution was done using a pyramid like initial perturbation. The results reveal the same two key elements of the bubble-merger model to describe the bubble and spike front evolution as in the 2D case except for different scaling constants.

Temperature-sensitive fluorescence imaging was performed to visualize the fin bow shock, separation shock, viscous shear layer and recirculation region of the flowfield at the junction of a blunt fin and a flat plate. The fluorescence technique was also used as the basis for a flow-tagging technique, making it possible to measure a velocity component and to demonstrate the reverse flow character of the separated region. From flow visualization images produced for the plane of symmetry, the point of boundary layer separation, the angle of the separation shock and the bow shock standoff distance were determined. These parameters were compared with predictions made by computational fluid dynamic simulations of the flowfield.

New method is presented to observe the nanosecond pressure pulse field developed by the pulse laser energy deposition into the water. The present method is based on the pressure dependence of the refractive index of water, and the change in pressure can be visualized by the change in the reflectivity of the optical prism-water interface. Two procedures are tested to record the pulse laser induced high-pressure shock wave front in water, that is, (1) monitoring the time evolution of the laser intensity by a photomultiplier reflected from a point on the interface, and (2) taking an instantaneous photograph of the interface. They will give the pressure-time profile by the procedure, and to give the pressure distribution at that instant. Experimental results shows the feasibility of the method.

For the purpose of constructing the design rules of air- breathing laser launcher, the expansion of plasma, which was produced from air by focusing pulse laser, was investigated. A 10-J-pulse TEA CO₂ laser was used for these experiments. First, plasma was formed in a quiescent atmospheric air. Photographs and shadowgraphs were taken using an ICCD camera with high-speed gating. From the photographs, the propagation velocity along the laser axis was measured. The velocity was found around 10⁴ m/s much higher than that of a detonation wave calculated using LSD model. Since laser intensity at the plasma front was below the threshold for LSD regime, absorption/expansion mechanism other than LSD might predominate under the experimental condition. Shadowgraphs were taken to measure the expansion velocity of plasma and that of shock wave around plasma. The flow facility, in which plasma is formed in Mach 2 stream, was presented.

Time-resolved spectroscopy using a combination of a monochromator, streak camera, image intensifier and CCD camera is conducted to investigate the radiative flow field generated in the in-tube laser propulsion configuration. A 5-J CO2 TEA laser beam is focused through a specially-designed, double- reflection optical system in atmospheric air. Radiation emission in the wavelength range of 320 to 850 nm is observed during a typical period of 10 microseconds.

High-speed liquid jets have been widely used to cut or penetrate material. It has been recently conjectured that the characteristics of high-speed fuel jets may also be of benefit to engines requiring direct fuel injection into the combustion chamber. Important factors are combustion efficiency and emission control enhancement for better atomization. Fundamental studies of very high velocity liquid jets are therefore very important. The characteristics and behavior of supersonic liquid jets have been studied with the aid of a shadowgraph technique. The high-speed liquid jet (in the supersonic range) is generated by the use of a vertical, single stage powder gun. The performance of the launcher and its relation to the jet exit velocity, with a range of nozzle shapes, has been examined. This paper presents the visual evidence of supersonic diesel fuel jets (velocity around 2000 m/s) investigated by the shadowgraph method. An Argon jet has been used as a light source. With a rise time of 0.07 microseconds, light duration of 0.2 microseconds and the use of high speed Polaroid film, the shadowgraph method can effectively capture the hypersonic diesel fuel jet and its strong leading edge shock waves. This provides a clearer picture of each stage of the generation of hypersonic diesel fuel jets and makes the study of supersonic diesel fuel jet characteristics and the potential for auto-ignition possible. Also, in the experiment, a pressure relief section has been used to minimize the compressed air or blast wave ahead of the projectile. However, the benefit of using a pressure relief section in the design is not clearly known. To investigate this effect, additional experiments have been performed with the use of the shadowgraph method, showing the projectile leaving and traveling inside the nozzle at a velocity around 1100 m/s.

A high-speed video camera captures bursting phenomena of a bubble at water surface under various surface tension and kinematic viscosity conditions. Surface tension and viscosity of water are changed by adding ethanol which dissolves into water and changes the surface tension, density and kinematic viscosity of water. A technique is proposed in order to separately evaluate effects of viscosity and surface tension on the water particle generation from bubble eruptions by utilizing the peculiar characteristics of the solution.

A novel technique for visualizing the gas temperature layer around bodies flying at hypersonic speeds is presented. The high temperature zone is visualized by photographing the light emitted from the electric discharge generated over a model exposed to hypersonic flow in a shock tunnel. The technique is based on electrical discharge phenomena, where the frequency of radiation emitted by the discharge path passing through the flow field varies with the temperature of the gas medium in the discharge path. The experiments are carried out in the Indian Institute of Science (IISc), Bangalore, India, hypersonic shock tunnel HST-1 at a nominal Mach number of 5.75 using helium as the driver gas, with free stream velocity of 1.38 km/s and free stream molecular density of 2.3396 X 10¹⁶ molecules/cm³. The electric discharge is generated across a line electrode embedded in the model surface and a point electrode suspended in the free stream. A high voltage discharge device (1.6 kV and 1 A) along with a micro-controller based pulse delay control module is integrated with the shock tunnel for generating and controlling electric discharge which lasts for approximately 2 microseconds. The gas temperature layer at zero angle of incidence around a flat plate and slightly blunted (5 mm bluntness radius) 20 degree apex angle slender cone model are visualized in this study. The visualized thickness of the high temperature layer around the flat plate is approximately 2 mm, which agrees well with numerical simulation, carried out using 2-D Navier-Stokes equations.

Visualization of the flow field around the base line model under the flight condition is one of the most valuable and basic steps on the high-speed airplane development. Now we consider a sharp focusing schlieren system that gives a means for observing any cross section of a flow field of perpendicular to the test beam axis of the optical system. This system can be used to examine a complex three-dimensional flow field. As a preliminary study, a sharp focusing schlieren system is designed with referring to the Weinstein's system. And visualization of steady transonic airfoil shock tube flow is performed with this system to investigate the effect of side-wall interference to the shock wave locations on an airfoil surface. The results show that the instrument has a capability for visualizing any cross section in the shock tub airfoil flow. Also, it is pointed out that the main steady shock wave profile focused at the center of the channel is different from the profile focused near the side-wall.

One of the authors developed a new spray drying nozzle (special quadruplet fluid spray nozzle) for drug manufacturing and it has succeeded in manufacturing fine particles of 2 micrometer diameter of 1/15 ratios to those currently in use. The flow visualization results show that the two air jets become under-expanded on both edge sides of the nozzle, generate shock and expansion waves alternately on each side and reach the edge tip, where they collide, unite, and spout out while shock and expansion waves are again formed in the mixed jet. When the edge surfaces are supplied with water, the water is extended into thin film by the air jet and intensely disturbed. At the nozzle tip it is torn into droplets, which are further atomized afterwards in shock waves. At the spray tip, the friction with ambient air shears the droplets furthermore, and they decrease further in size.

Pseudo high speed photography has been developed to observe intermittent, periodic and high speed phenomena like diesel spray. Main device of this photography consists of Automatic Variable Retarder (AVR) which delays gradually timing between diesel injection and strobe spark with the micrometer. This technique enables us to observe diesel spray development just like images taken by a high speed video camera. This paper describes a principle of pseudo high speed photography, experimental results of adaptation to diesel spray and analysis of the diesel atomization mechanism.

This paper describes a flow visualization of high-speed liquid jets ranging from 20 m/s to 200 m/s, which were generated from two different methods. The first method is that the jet (200 m/s) is generated by using a high-speed projectile to impact a rectangular nozzle where water is contained. For the 200 m/s liquid jets, flow visualization was conducted using a Xenon flash unit. The second method is that the jet (20 m/s) is generated by using compressed gas to push liquid flowing through a tube. For the 20 m/s liquid jets, flow visualization was conducted using a strobe light unit. A number of interesting phenomena have been newly found.

Optical breakdown of air is explored by using high-speed photography for the realization of laser propulsion system in aerospace engineering. The multiple ionization and subsequent pear-shaped emission by laser pulse through a convex lens are recorded and analyzed by image converter camera. The improved pulsed-laser shadowgraphy employed in this system successfully enables us to visualize the transient structures of complicated shock waves more clearly than ever. The ionization just above the surface of an aluminum target is also examined in comparison with the case of no target, which may be the major mechanism of Myrabo's demonstration of a small flyer launching by a pulsed carbon dioxide laser. Not only the high- enthalpy states of the ionized atmosphere are calculated but also the precise history of breakdown initiation in the nanosecond laser pulse is obtained.

We developed a two-dimensional space resolved high speed UV sampling camera (2D-HISAC) to study energy transport in laser produced plasmas. The HISAC is composed of an optical bundle fiber coupled to a streak camera to get a two dimensional spatial resolution. The temporal resolution of a few 10 ps was obtained with the 2D-HISAC using multi mode fibers. This 2D- HISAC was applied to the experiments to investigate laser- produced plasmas. Nonlocal heating by high-density relativistic electrons in ultra-intense laser interactions was temporally and 2-D spatially resolved. Observed were filament of the relativistic electron heating in solid targets. The 2D- HISAC was also used in the experiment to estimate uniformity of laser-ablation pressures at an oblique incidence of laser light with a large spot area. Two-dimensional shock heating was temporally resolved, resulting in the distribution of the ablation pressure.

The paper deals with the flow control and measurement of liquids that form droplets. An experimental investigation on the mass of the falling droplet from capillary tubes was carried out. Examples where the present study is considered useful are in the measurement of injection flow rates of fuel in a diesel engine and for flow measurement of drops from capillary tubes in medicine. In this investigation the capillary tubes used were made of brass and Bakelite material. The inner diameter of each tubes was kept constant at 1 mm and outer diameter tubes were changed from 2 mm to 5 mm in accordance with the variation in the liquid surface tension. Experiments on falling droplet of distilled water and methyl alcohol were also carried out, as the surface tension of these liquids are so very different. The experiments were performed using a visualization technique. The present paper discusses the effect of tube diameter, droplet size and physical property of liquid on the phenomena of a falling droplet.

An experiment of inert gas injection into a high enthalpy hypersonic air flow is described. Gaseous helium at room temperature was injected transversely through four (phi) 1.5 mm circular sonic injectors at a spacing of 20 mm, which was located 28 mm downstream from a backward-facing step of 4 mm height. The experiment was carried out in the high enthalpy shock tunnel HIEST under the free stream test condition at Mach number of 6.5 and at the velocity of 4 km/s. The purpose of the experiment was to examine transient behavior of the helium jet mixing with the test air flow. Sequential Schlieren flow visualization with high-speed CCD camera of 1 (mu) sec exposure time have been used. Pitot pressure profile in the helium jet was measured at three stream-wise location. The measurements showed that the helium jet reached to the steady state in less than 2 msec, which was within HIEST test duration.

The videostroboscopy of the larynx has become a powerful tool for the study of vocal physiology, assessment of the fold abnormalities, motion impairments and functional disorders, as well as for the early diagnosis of diseases like cancer and pathologies like nodules, carcinoma, polyps and cysts. Since the vocal folds vibrate in the range of 100 Hz up to 1 kHz, the video stroboscope allows physicians to find otherwise undetectable problems. The color information is essential for the physician by the diagnosis e.g., of the early cancer stage. A previously presented 'general purpose' monochrome high-speed video stroboscope has been tested also for the inspection of the human larynx. Good results have encouraged the authors to develop a medical color version. In contrast to the conventional stroboscopes the system does not utilize pulsed light for the object illumination. Instead, a special asynchronously shuttered video camera triggered by the oscillating object has been used. The apparatus including a specially developed digital phase shifter provides a stop phase and slow-motion observation in real time with simultaneous recording of the periodically moving objects. The desired position of the vocal folds or their virtual slowed down vibration speed does not depend of the voice pitch changes. Sequences of hundreds of high resolution color frames can be stored on the hard disk in the standard graphic formats. Afterwards they can be played back frame-by-frame or as a video clip, evaluated, exported, printed out and transmitted via computer networks.

Shadowgraphy of gall bladder stone, which is held by a basket and immersed in a civete is performed. The exposure time is determined by the time of a N-Dye laser pulse used as a lightening source for photography. The shadowgram is projected in the objective of a camera which is connected to a microscope. The light coming from the laser, illuminates the civete collecting optical information of the stone and physical phenomena appearing above the stone. On top of the stone a tip of optical fiber is fixed, which is used for transmitting Ho:Yag laser power to the stone. Using a computer and time delay the laser pulses used for destruction and illumination are synchronized. Since the N-Dye laser pulse is pico-second range and the Ho:Yag laser pulse is in the range of micro-second, many image frames are obtained within the time of one pulse applied during the destruction. It is known that in the process of stone destruction several phenomena like plume, plasma, shock wave and bubble formation take place. However, the physical mechanism of the stone destruction is not yet completely understood. From the obtained results the above phenomena are studied which gives new information and clue for understanding some of the mentioned phenomena. The laser power which is guided by an optical fiber into the gall bladder or kidney of the human body can damage the living tissue and cause some serious health problems. For this reason the fiber needs to be oriented properly during the action of the laser power.

A new optical procedure was proposed to detect the shock wave front sensitively, which makes it possible to measure shock Hugoniot in higher precision than the previous method. The present method is based on the very large pressure dependence of the refractive index of liquids upon compression. This new shock sensor is suitable for the precise measurement of shock Hugoniot states for liquids and bio-related soft materials. Experiments were performed on water, NaCl aqueous solution and gelatine gel in the pressure range of less than 1 GPa. It is found that the method is very effective for the sensitive detection of shock front in these materials. By comparing the data for these materials, precision of the method was discussed.

This paper describes a high-speed imaging system using dual MOS-based solid-state cameras and its biological application. Our dual camera system can capture images synchronously and produce sets of 64 X 64-pixel images at a rate of 0.6 ms/frame. The system is composed of three blocks: the 'camera- drive,' 'memory,' and 'processor' blocks. We developed these block hardware circuits using an FPGA device in the following manner. (1) Camera-drive block: two cameras were synchronized with the Hd (horizontal drive) and Vd (vertical drive) signals using a 16 MHz clock. (2) Memory block: 12-bit track-and-hold A/D converters were used to digitize the output from both cameras in parallel and store it in frame memory. Each camera had a 16-MB memory capacity. (3) Processor block: image data from both cameras was stored in two separate frame memories. This block simultaneously accessed the same memory address for each frame and calculated the difference in the observed values, which was then transferred to a personal computer. This system enables us to observe pure neural activity from images contaminated with heartbeat noise.

We have designed and built a high-speed CCD imaging system for monitoring neural activity in an exposed animal cortex stained with a voltage-sensitive dye. Two types of custom-made CCD sensors were developed for this system. The type I chip has a resolution of 2664 (H) X 1200 (V) pixels and a wide imaging area of 28.1 X 13.8 mm, while the type II chip has 1776 X 1626 pixels and an active imaging area of 20.4 X 18.7 mm. The CCD arrays were constructed with multiple output amplifiers in order to accelerate the readout rate. The two chips were divided into either 24 (I) or 16 (II) distinct areas that were driven in parallel. The parallel CCD outputs were digitized by 12-bit A/D converters and then stored in the frame memory. The frame memory was constructed with synchronous DRAM modules, which provided a capacity of 128 MB per channel. On-chip and on-memory binning methods were incorporated into the system, e.g., this enabled us to capture 444 X 200 pixel-images for periods of 36 seconds at a rate of 500 frames/second. This system was successfully used to visualize neural activity in the cortices of rats, guinea pigs, and monkeys.

Deformation processes of aluminum honeycombs with hexagonal cells subjected to the in-plane impact of a rigid impactor are investigated experimentally and numerically in relation to the dynamical behavior of cellular materials and complex materials under high-speed loadings. Strain waves are measured using strain gauges glued on the cell walls and reaction forces are measured using a load cell at the contact surface between the honeycomb and a fixed wall. A high-speed camera is used to visualize the deformation process. Numerical simulations are partly made for the same configuration as the experiment. Very distinctive deformation mechanisms of individual cells and propagation mechanisms of strain waves in the honeycomb are found out. Also, characteristic two-dimensional behavior is revealed in spite of one-dimensional and uni-directional impact loading.

In this study, the dynamic fracture behavior of a bonded dissimilar material, which had the interfacial crack, was analyzed. The stress intensity factor of the interfacial crack was determined by using method of caustics and the simple type high-speed photography method for the analysis, and dynamic behavior of the interfacial crack, which received the shearing deformation, was observed. The test specimen shape was assumed to be ENF test specimen. The sample material made to epoxy resin and polycarbonate, and used an epoxy system adhesive for joining. As a result, the vibration characteristic was possessed in the interfacial crack as well as the crack in a homogeneous material. And, a dynamic fracture toughness of the interfacial crack reached a different value by a material and joined condition to receive the load. Moreover, the propagation behavior of the interfacial crack became a different result with receiving the load and the phase material. The interfacial crack wound to the upper phase material at the case when the upper phase material was a brittleness material, and the propagating angle of the crack was 70 degrees. The dynamic fracture behavior of the interfacial crack when the upper phase material was ductile material propagated on the interface at high speed. In addition, the time of the propagation of the crack became a result different depending on joined condition, too. When the upper phase material was brittle material, the crack propagation time became a slow result early for ductile materials. The dynamic fracture toughness value and the crack propagation time of the interfacial crack became different results by the difference of the component of the test specimen. Therefore, dynamic fracture toughness and the crack propagating behavior depended on a material and joined condition to receive the load.

It is very important to understand a dynamic fracture behavior under the high temperature environment. However, these researches of polymeric materials is unexpectedly little. In this study, the cracked polycarbonate plate was used for a sample material, and carry out the impact three point bending test in the electric furnace. The caustics method and the simple high-speed photography method was used for the analysis. As experimental results. A different fracture behavior was shown whether by doing the dehydration processing same normal temperature (23.5 degrees Celsius). At the higher temperature, the dynamic stress intensity factor indicated lower value. In addition, it has been understood that there is a tendency to which the fracture toughness value decreases while becoming a high temperature.

An impact test system is developed by incorporating a digital imaging system with a gas-gun type impact machine. By using this system, impact perforation tests by a steel ball projectile traveling at high speed are conducted on polymer and ceramic materials, while, at the same time, consecutive images of the projectile perforating the target material are taken during the tests. Combination of the test results along with the ultra-high speed images leads to analytical modeling for estimating/predicting the perforation characteristics of these materials. It is concluded from the present study that, (1) the impact test system developed here is proven to be a powerful means to the end of this investigation, (2) the ultra-high speed photography allows visualization of such a high-speed mechanical process as an impact perforation of a target material by a projectile, and (3) the digital consecutive images are very helpful with the analytical modeling, from which semi-empirical expressions for estimating/predicting the major perforation characteristics of these materials are successfully obtained.

In the fly-by sample return project of the ISAS, fragments of Asteroid 1998-SF38's surface will be collected upon high speed impingements of steel projectiles onto its surface. The projectiles will be launched from a compact launcher or a projector. The Shock Wave Research Center is collaborating with ISAS in the design of the projector and its performance test. This paper reports the design of the projector that can launch stainless steel projectiles of 100 g in weight at 300 m/s muzzle speed. The production of fragments at impingement was tested on the ground.

In order to study the fracture and deformation in float glass loaded in a shock tube test for analyzing explosion resistance, high-speed photography with holographic interferometry was utilized. Ordinary float glass (soda-lime- silica glass) plate of size 300 mm X 300 mm and in two thickness was used for these specimens for this experiment. By using single and double exposure holographic interferometry, crack propagation and deformation in float glass loaded by a shock tube was photographically observed, and the value of stress generation was measured.

The advent of CCD cameras and computerized data recording has spurred the development of several new cameras and techniques for recording nanosecond images. We have made a side by side comparison of three nanosecond frame cameras, examining them for both performance and operational characteristics. The cameras include; Micro-Channel Plate/CCD. Image Diode/CCD and Image Diode/Film; combinations of gating/data recording. The advantages and disadvantages of each device will be discussed.