We review a number of instruments employed in a high-intensity J-KAREN-P laser-solid interaction experiment and discuss the applicability of the diagnostics to the best target position determination with a ~10 μm accuracy, while the focal spot size was ~1 μm and peak intensity was up to 7×1021 W/cm2. We discuss both front- and back-side diagnostics, some of them operated in the infrared, visible and ultraviolet ranges, while others in the extreme ultraviolet, soft X-ray and gamma-ray ranges. We found that the applicability of some of the instruments to the best at-focus target position determination depends on the thickness of the target.
A compact undulator-based soft X-ray radiation source furnishing the laser wakefield electron acceleration concept is currently being developed at ELI-Beamlines in the Czech Republic. It will bring to the user community a high-repetition-rate (up to 50 Hz) soft X-ray radiation to enable high-temporal-resolution pump-probe experiments, combined with XANES spectroscopy, high-resolution microscopy, investigations of biological molecules and chemical reactions, evaluation of soft X-ray multilayer optics, as well as with coherent radiation applications like ptychography or coherent diffraction imaging, at later development stages. Now the first stage called LUIS is under development, which will result in production of uncoherent radiation in the ‘water window’ spectral range. The next stages will enable coherent extreme ultraviolet and soft X-ray radiation. We present suggestions on the user-oriented program to the community.
We have measured the spectral quantum efficiency of several digital detectors in two spectral ranges, namely vacuum ultraviolet (VUV, 115-310 nm) and extreme ultraviolet (EUV, 10-58 nm) wavebands. We used monochromatic synchrotron radiation from the VEPP-4M storage ring (INP, Novosibirsk) to investigate the spectral response of GSENSE400BSI-GP CMOS which have been specially designed for optimum VUV sensitivity, as well as the WSO-UV project’s custom deep cooled CCD272-64 sealed within a hermetic contaminant-protective stainless-steel enclosure with a VUV-transparent entrance window. The CMOS GSENSE400BSI-GP sensitive surface has four types of different pretreatment: (i) small boron implantation dose, weak annealing; (ii) small boron implantation dose, strong annealing, (iii) large boron implantation dose, weak annealing; (iv) large boron implantation dose, strong annealing. These VUV optimised CMOS sensors have higher spectral sensitivity and higher quantum efficiency in the 112-180 nm spectral range, compared to a commercial CMOS which is typically optimised for the best performance at visible wavelengths, but at longer wavelengths GSENSE400BSI-GP sensitivity decreases. The measurements have revealed that stronger annealing can slightly increase the CMOS spectral sensitivity, while large boron implantation dose decreases the sensitivity of the CMOS sensors. With relation to quantum efficiency figures, CCD still prevails in the VUV while recent advances in CMOS technology could make CMOS more preferable in the EUV range.
World Space Observatory Ultraviolet (WSO-UV) is a major Russian-led international collaboration to develop a large Space-borne 1.7 m Ritchey-Chrétien telescope and instrumentation to study the Universe in the ultraviolet wavelengths. The WSO-UV WUVS spectrograph consists of three channels: two high resolution channels (R=50000) with spectral ranges of 115-176 nm and 174-310 nm, and a low resolution (R=1000) channel with a spectral range of 115-305 nm. Each of the three channels has an almost identical custom detector consisting of a CCD inside a vacuum Enclosure, and drive electronics with associated cables. The main challenges of the WUVS detectors are to achieve high quantum efficiency in the FUV-NUV range, to provide low readout noise (≤3 e- at 50 kHz) and low dark current (≤ 12 e- /pixel/hour), to operate with integral exposures of up to 10 hours, and to provide good photometric accuracy. Teledyne e2v has designed three variants of a custom CCD272-64 sensor with different UV AR coatings, optimised for each WUVS channel. The custom vacuum Enclosure, also designed by Teledyne e2v, prevents contamination and maintains the CCD at the operating temperature of -100oC, while the temperature of the WUVS optical bench is +20oC. STFC RAL Space has developed the Camera Electronics Box (CEB) which houses the CCD drive electronics. Digital correlated double sampling technology provides extremely low readout noise and also enables flexibility to optimise readout noise against pixel frequency for a number of normal and binned pixel readout modes. This paper presents the general trade-offs of the WUVS detector design, methods for extending the service life of the CCD sensors working with low signals in a Space radiation environment, and a summary of the measured and calculated key parameters of the WUVS detectors.
We present characterization measurements of dark current signal at different temperatures and spectral sensitivity of cooled backside-illuminated EUV CCD matrices intended for future solar space missions, including projects ARKA and KORTES. The measurements have been conducted inside a vacuum chamber in the 125-250 Å spectral range with the use of tungsten laser-driven plasma as a source of EUV radiation. Applications of the EUV CCDs for contemporary and future space investigations of solar physics taking place in solar flares is being overviewed and discussed.
We have numerically optimized several broadband aperiodic normal-incidence multilayer mirrors based on Sb/B4C for the 85 – 125 Å spectral domain for spectroscopy applications below the silicon L-edge (λ = 125 Å). Three multilayer mirrors were then synthesized. The designed multilayer structures were optimized for a maximum uniform reflectivity in the 90 – 100, 95 – 105 and 100 – 120 Å wavebands, respectively. All the Sb/B4C multilayer mirrors were synthesized via magnetron sputtering in argon medium. The multilayers reflection spectra were evaluated with the use of a laboratory XUV spectrograph employing a laser-plasma radiation source, the mirror under study, a transmission diffraction grating and a backside-illuminated CCD matrix. The experimentally recorded spectra were compared with the theoretical ones. Numerical calculations of aperiodic Sb/B4C multilayer structures with different layer densities are presented. Effects of lower densities and small random variations of the individual layer widths on the reflection spectra are discussed.
We present the design, calculations and simulations of high-resolution concave-VLS-grating-based soft X-ray and VUV spectrographs, as well as a plane VLS grating instrument. We have designed a normal-incidence imaging VLS grating spectrograph for a 820 – 1690 Å spectral interval and a series of grazing-incidence VLS spectrographs with imaging capabilities. The experimentally recorded spectral images of laboratory laser plasmas were obtained with the aid of a VLS spectrometer based on a concave aperiodic multilayer mirror and a plane VLS grating. Two modifications of this spectrometer were implemented with two different VLS gratings. These modifications exhibit spectral resolution of 500 and 800 over the 125 – 300 Å spectral waveband. Spatial resolution corresponds to double CCD-detector pixel size.
We present a laboratory high-aperture monochromator-reflectometer employing laser-plasma radiation source and three replaceable Schwarzschild objectives for a certain range of applications in the soft X-ray spectral waveband. Three sets of X-ray multilayer mirrors for the Schwarzschild objectives enable operation of the reflectometer at the wavelengths of 135, 171 and 304 Å, while a goniometer with three degrees of freedom allows different measurement modes. We have used the facility for a laboratory CCD calibration at the wavelengths specified. Combined with the results of the CCD sensitivity measurements conducted in the VUV spectral waveband, the total outcome provides a more comprehensive understanding of the CCD effectivity in a wide spectral range.
Our intention is to develop high-resolution stigmatic spectral imaging in the XUV (2 – 40 nm). We have designed, aligned and tested a broadband stigmatic spectrometer for a range of 12–30 nm, which makes combined use of a normalincidence multilayer mirror (MM) (in particular, a broadband aperiodic MM) and a grazing-incidence plane varied linespace (VLS) reflection grating. The concave MM produces a slightly astigmatic image of the radiation source (for instance, the entrance slit), and the VLS grating produces a set of its dispersed stigmatic spectral images. The multilayer structure determines the spectral width of the operating range, which may amount to more than an octave in wavelength (e.g. 12.5–30 nm for an aperiodic Mo/Si MM), while the VLS grating controls the spectral focal curve. The stigmatism condition is satisfied simultaneously for two wavelengths, 14 and 27 nm. In this case, the condition of non-rigorous stigmatism is fulfilled for the entire wavelength range. A LiF laser plasma spectrum was recorded in one 0.5 J laser shot. A spatial resolution of 26 μm and a spectral resolution of 900 were demonstrated in the 12.5 – 25 nm range. We also report the design of a set of flat-field spectrometers of Harada type with VLS gratings. VLS gratings were made by ebeam and interference lithography. A technique (analytical + numerical) was developed for calculating optical schemes for writing plane and concave VLS gratings with predefined line density variation.
ARKA and KORTES are two upcoming solar space missions in extreme ultraviolet and X-ray wavebands. KORTES is a sun-oriented mission designed for the Russian segment of International Space Station. KORTES consists of several imaging and spectroscopic instruments that will observe the solar corona in a number of wavebands, covering EUV and X-ray ranges. The surveillance strategy of KORTES is to cover a wide range of observations including simultaneous imaging, spectroscopic and polarization measurements. ARKA is a small satellite solar mission intended to take highresolution images of the Sun at the extreme ultraviolet wavelengths. ARKA will be equipped with two high-resolution EUV telescopes designed to collect images of the Sun with approximately 150 km spatial resolution in the field of view of about 10'×10'. The scientific results of the mission may have a significant impact on the theory of coronal heating and may help to clarify the physics of small-scale solar structures and phenomena including oscillations of fine coronal structures and the physics of micro- and nanoflares.
We present measurements of spectral sensitivity of CCD-matrices designed for future space missions. Three wavebands were under investigation: UV-visible range (300-600 nm), UV (250-300 nm) and VUV (110-250 nm). We used a halogen lamp, a deuterium lamp and a tungsten laser-driven plasma as sources of radiation. IRD UV silicon photodiodes and a photomultiplier tube fulfilled the function of calibrated detectors. Using a calibrated CCD, we measured initial spectral effectivity of the tungsten laser-driven plasma radiation source in the 110-250 nm waveband. Afterwards we experimentally evaluated spectral transmittance functions of three VUV multilayer filters for future space telescopes.
We report on the current status of the KORTES project – the first sun-oriented mission for the International Space Station to be launched in 2016-2017. KORTES will comprise several imaging and spectroscopic instruments that will observe solar corona in a number of wavebands, covering EUV and X-Ray ranges. A brief overview of the instrumentation of KORTES, its’ layout, technical parameters and scientific objectives is given. An additional attention is given to the design of multilayer optics and filters to be employed in EUV instruments of KORTES.
We report measurements of the reflection spectra of (i) concave (spherical and parabolic) Mo/Si, Mg/Si, and Al/Zr
multilayer mirrors (MMs) intended for imaging solar spectroscopy in the framework of the TESIS/CORONAS-FOTON
Satellite Project and of (ii) an aperiodic Mo/Si MM optimized for maximum uniform reflectivity in the 125-250 Å range
intended for laboratory applications. The reflection spectra were measured in the configuration of a transmission grating
spectrometer employing the radiation of a tungsten laser-driven plasma as the source. The function of detectors was
fulfilled by backside-illuminated CCDs coated with Al or Zr/Si multilayer absorption filters. High-intensity second-order
interference reflection peaks at wavelengths of about 160 Å were revealed in the reflection spectra of the 304-Å Mo/Si
MMs. By contrast, the second-order reflection peak in the spectra of the new-generation narrow-band (~12 Å FWHM)
304-Å Mg/Si MMs is substantially depressed. Manifestations of the NEXAFS structure of the L2, 3 absorption edges of
Al and Al2O3 were observed in the spectra recorded. The broadband Mo/Si MM was employed as the focusing element
of spectrometers in experiments involving (i) the charge exchange of multiply charged ions with the donor atoms of a
rare-gas jet; (ii) the spectroscopic characterization of a debris-free soft X-ray radiation source excited by Nd laser pulses
in a Xe jet (iii) near-IR-to-soft-X-ray frequency conversion (double Doppler effect) occurring in the retroreflection from
the relativistic electron plasma wake wave (flying mirror) driven by a multiterawatt laser in a pulsed helium jet.
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