In 2006 an approach was developed that used chirped fiber gratings in combination with a high speed read out configuration to measure the velocity and position of shock waves after detonation of energetic materials. The first demonstrations were conducted in 2007. Extensions of this technology were made to measure pressure and temperature as well as velocity and position during burn, deflagration and detonation. This paper reviews a series of improvements that have been made by Columbia Gorge Research, LLC, Lawrence Livermore National Lab and Los Alamos National Lab in developing and improving this technology.
A novel very high speed fiber grating sensor system has been used to support velocity, position, temperature and pressure measurements during burn, deflagration and detonation of energetic materials in Russian DDT tests. For the first time the system has been demonstrated in card gap testing and has allowed real time measurements of the position of the blast front into the card gap and monitoring of pressure at key locations in the card gap test. This paper provides an overview of this technology and examples of its application.
An innovative system that allows the measurement of velocity, position, temperature and pressure during burn,
deflagration and detonation of energetic materials has been developed. An initial demonstration of this system has been
able to measure pressures up to 1,200,000 psi, and temperature changes of 400° C over a period of 25 microseconds.
Both measurements were instrument limited. Improved instrumentation will allow extensions to 4,000,000 psi
measurements and enhanced resolution of over and order of magnitude. This is the first time to our knowledge that
measurements of velocity, position, temperature and pressure have been made interior to highly energetic materials
during burn, deflagration and detonation. The technology is in its very early stages. It has great potential to make
important near term measurements with significant further improvements being made as the technology begins to
mature. Immediate application areas include assessment of the performance of solid rocket motor propellant materials,
insensitive munitions and detailed measurements of high speed, energetic events. Additionally, continuous detonation
wave velocities were measured inside of large explosive charges greater than 200 millimeters in length.
Fiber grating sensors may be used to monitor high-speed events that include catastrophic failure of structures,
ultrasonic testing and detonations. This paper provides insights into the utility of fiber grating sensors to measure
structural changes under extreme conditions. An emphasis is placed on situations where there is a structural
discontinuity. Embedded chirped fiber Bragg grating (CFBG) sensors can track the very high-speed progress of
detonation waves (6-9 km/sec) inside energetic materials. This paper discusses diagnostic instrumentation and
analysis techniques used to measure these high-speed events.
Fiber grating sensors can be used to support a wide variety of high speed measurement applications. This
includes measurements of vibrations on bridges, traffic monitoring on freeways, ultrasonic detection to
support non-destructive tests on metal plates, and providing details of detonation events. This paper
provides a brief overview of some of the techniques that have been used to support high speed
measurements using fiber grating sensors over frequency ranges from 10s of kHz, to MHZ and finally
toward frequencies approaching the GHz regime.
In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation models and detonation models of
high explosives, the ability to continuously measure the detonation velocity within an explosive is required. Progress
on an embedded velocity diagnostic using a 125 micron diameter optical fiber containing a chirped fiber Bragg grating
is reported. As the chirped fiber Bragg grating is consumed by the moving detonation wave, the physical length of the
unconsumed Bragg grating is monitored with a fast InGaAs photodiode. Experimental details of the associated
equipment and data in the form of continuous detonation velocity records within PBX-9502 are presented. This small
diameter fiber sensor has the potential to measure internal detonation velocities on the order of 10 mm/μsec along path
lengths tens of millimeters long.
Femtosecond laser ablation shows promise in machining energetic materials into desired shapes with minimal thermal and mechanical effects to the remaining material. We will discuss the physical effects associated with machining energetic materials and assemblies containing energetic materials, based on experimental results. Interaction of ultra-short laser pulses with matter will produce high temperature plasma at high-pressure which results in the ablation of material. In the case of energetic material, which includes high explosives, propellants and pyrotechnics, this ablation process must be accomplished without coupling energy into the energetic material. Experiments were conducted in order to characterize and better understand the phenomena of femtosecond laser pulse ablation on a variety of explosives and propellants. Experimental data will be presented for laser fluence thresholds, machining rates, cutting depths and surface quality of the cuts.
Spectroscopic techniques are ideal for characterization and process control of electron beam generated beam generated vapor plumes. Absorption based techniques work well for a wide variety of applications, but are difficult to apply to optically dense or opaque vapor plumes. We describe an approach for monitoring optically dense vapor plumes that is based on measuring the group velocity delay of a laser beam near an optical transition to determine the vapor density. This technique has a larger dynamic range than absorption environment. Aluminum as chosen because of its prevalence in high performance aircraft alloys. In these applications, composition control of the alloy constituents is critical to the deposition process. Data is presented demonstrating the superior dynamic range of the measurement. In addition, preliminary data demonstrating aluminum vapor rate control in an electron beam evaporator is presented. Alternative applications where this technique could be useful are discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.