A summary of recent developments of modern x-ray sources based on university-scale 1 MA z-pinch generators
is given. Wire array z-pinches are a powerful x-ray source that was found during the last decade to be promising
for inertial confinement fusion and radiation physics. Applications of novel and traditional wire-array
configurations, such as X-pinches, planar and compact cylindrical wire arrays, to high energy density science are
observed and analyzed. After a general introduction to wire array sources, new results are discussed along with
numerous experiments.
Results of the development and study of a table-top z-pinch and laser-plasma x-ray/EUV facility "Sparky" are presented. The goal of development of this facility was to obtain high density and temperature plasmas of high atomic number elements in two different ways: vacuum spark or thin (micron-scale) wires in z-pinch device, and laser-plasma source with a flat target.
The results of theoretical and experimental studies of anisotropic plasma sources are reported. They are based on x-ray line spectropolarimetry, a powerful new tool for investigating anisotropy of high-temperature plasmas. It is based on theoretical modeling of polarization-sensitive x-ray line spectra recorded simultaneously by two spectrometers with different sensitivities to polarization. The difference in these polarization-sensitive spectra is used to diagnose the parameters of anisotropic electron beams in plasmas. Theoretical predictions of polarization which cover a broad spectral range from K- to M-shell line radiation are presented. The results of Ti and Mo x-pinch polarization-sensitive experiments at UNR are overviewed. This diagnostic can be applied not only to x-pinches as demonstrated here but to laser-generated and other laboratory x-ray sources.
Experimental results of complex studies of x-ray/EUV radiation from hot dense x-pinch Ti, Fe, Mo, and W plasmas generated by a pulse-powered z-pinch machine with Imax~0.9 ÷ 1.0 MA and a current rise time of 100 ns are overviewed. Structures and spatial dimensions of 0.9-1.0 MA x-pinch sources in a wide energy range of 0.15 - 0.6 keV, 1-10 keV and 10-100 keV are analyzed. Generation of different types of hot spots in high-current multiburst x-pinches are described and a possible explanation of observed effects based on generation of shockwaves in plasmas are discussed. Hard x-ray x-pinch spectra are analyzed. The analysis of time and energy scaling of 0.9 - 1.0 MA x-pinch x-ray/EUV pulses indicate the possible existence of competing mechanisms of the dissipation of the initial discharge x-pinch energy. The future applications of the high current x-pinch as the sub-keV-10 keV radiation driver and the 50 - 100 keV backlighter are discussed.
Semitransparent HOPG monochromators are being investigated with an emphasis on their potential applications in X-ray imaging systems. HOPG plates and films, 5-100micrometers thick and up to 14 cm2 in area, were tested. Scanning techniques were used to measure the profiles of local reflectivity and transparency at different monochromator thicknesses. Mosaic spread, (Delta) (omega) , down to 3.6' was recorded. HOPG film areas with average (Delta) (omega) =5' and 6' were equivalent to 4.5 and 10 cm2 respectively. The echelon monochromator arrangement produced a sharp increase in reflectivity leading to the possibility of primary beam sweeping. Results to date are very promising for future applications in fields such as medical diagnostics and surgical treatments monitored using digital X-ray cameras.
A multi-channel, fast, hard x-ray diode spectrometer is being developed at the Nevada Terawatt facility. This spectrometer helps facilitate the study of the time evolution of hard x-ray emissions from hot, dense plasma. Each channel in the array can be adjusted individually with shielded view areas, allowing small areas of an x-ray source to be isolated and studied by region. This spatial resolution capability will permit a better understanding of the mechanisms present in hot, dense plasma. Results will be presented of experimental tests, and their interpretation, pertaining to the hard x-ray emissions generated from an x-pinch source in a pulse-power type device.
A new five-channel spectrometer is designed for registration of x-ray spectral line emissions from plasmas with temporal resolution. All channels are independent from each other and include wide variety of dispersing elements (crystals and/or multiplayer mirrors) and detectors (Si-diodes or PCD). Sixth channel is used for device alignments with minimum adjustments can be used as channel for transmission diffraction grating spectrometer or channel for another time resolved detector. The device was used in experiments with different plasma sources in different configurations and showed its reliability and flexibility.
In the study (SPIE 4144, 128 (2000)) we have presented results of the experimental study of a strongly nonuniform spatial distribution of output keV and sub-keV radiation, that transported by different types of glass mono- and policapillary converters from the point x-ray laser plasma and z-pinch plasma sources. In this paper the features of x-ray radiation are analyzed theoretically using the Fresnel-Kirchhoff diffraction theory and the method of images. We show that the wave effects can strongly affect properties of the x-ray capillary optics.
Victor Kantsyrev, Bruno Bauer, Alla Shlyaptseva, Dmitri Fedin, Stephanie Hansen, Radu Presura, Stephan Fuelling, Steve Batie, Andrew Oxner, Harold Faretto, Nick Ouart, Sean Keely, Hank LeBeau, David Chamberlain
The x-ray emission of Ti, Fe, Mo, W and Pt x-pinches are currently bieng studied at the Nevada Terawatt Facility z- pinch machine (0.9-1.0 MA, 100 ns). New x-ray diagnostics for time-resolved spectroscopy and imaging has been developed and used in x-pinch experiments. The total x- ray/EUV yield was more than 10 kJ. The minimum x-ray pulse duration was 1.1 ns (Mo, W, Pt). For Ti, Mo and W pinches x-ray pulses occurred in two or three groups in the narrow time intervals after the start of the current. The most compact emitting region has been observed for a planar-loop Mo x-pinch (the number of hot spots ranging from 1-5 with a minimum size smaller than 30 micrometers at (lambda) <1.5-2 Angstoms). Strong jets were observed (Ti, Fe, Mo) directed toward the discharge axis, perpendicular to the wires. A structure of an x-pinch includes energetic electron beams directed toward the anode and along wires. The total beam energy increases from Ti to W. A pulse of hard x-ray radiation was observed moving upwards along the axial axis with an energy of several hundred keV(Mo). The size of this source was smaller than 1 mm. The measurements of temperature and density of x-pinch plasmas were based on theoretical modeling of K-shell Ti and L-shell Mo spectra (Te=1.5 keV for Ti, 0.8 keV for Mo, Ne up to 2- 3x1022 cm-3 with 1-10% of hot electrons).
A wide variety of x-ray and extreme ultraviolet (EUV) diagnostics are being developed to study z-pinch plasmas at the Nevada Terawatt Facility (NTF) at the University of Nevada, Reno. Time-resolved x-ray/EUV imaging and spectroscopy, polarization spectroscopy, and backlighting will be employed to measure profiles of plasma temperature, density, flow, and charge state and to investigate electron distribution functions and magnetic fields. These diagnostics are used to study the NTF pinch as an x-ray/EUV source for plasma spectroscopy research and to examine the early-time evolution of a current-driven wire, the formation of a plasma sheet from the explosion and merging of wires, etc. The instruments are state-of-the-art applications of glass capillary converters (GCC), multilayer mirrors (MLM), and crystals. Devices include: a novel glass-capillary-based two- dimensional imaging spectrometer, a time-resolved x-ray spectrometer, a 5-channel crystal/MLM spectrometer ('Polychromator') with a transmission grating spectrometer, and two-channel x-ray/EUV polarimeters-spectrometers (to study simultaneously polarization of K- and L-shell radiation). An x-pinch backlighter, yielding point-projection microscopy with ns resolution is under development. X-ray convex-crystal survey spectrometers, and fast filtered x-ray diodes have observed single Ti-, Fe and W-wire z-pinches, and Ti and Fe x- pinches. The NTF x-ray yield and x-ray pulse duration depend sensitively on the wire load. There is evidence of a strong energetic electron beam with a complex spatial structure in x- pinch plasmas. This work is supported by DOE, DOD, SNL, and UNR.
Victor Kantsyrev, Bruno Bauer, Alla Shlyaptseva, Dmitry Fedin, Stephanie Hansen, Radu Presura, Steve Batie, Wade Cline, Harold Faretto, Bruno Le Galloudec, Andrew Oxner, Diana McCrorey, Nick Ouart, Hank LeBeau
Powerful pulsed soft x-ray point sources are being developed, driven by the Zebra z-pinch at the Nevada Terawatt Facility. A wide variety of x-ray and EUV pulses can be generated, depending on the z-pinch load. X-ray and EUV pulses have been produced with duration from 1.5 ns to 40 ns, energy from 30 J to 9 kJ, and effective source size smaller than 100 micrometers . These pulses will be used for the development of plasma diagnostics, for the study of surface physics, and for microscopy.
This research is a continuation of our activity on the development and study of glass-capillary optics devices that started in 1974. We presented new results of the experimental study of a strongly nonuniform spatial distribution of output keV and sub-keV radiation, that transported by different types of glass mono- and polycapillary converters from point x-ray laser plasma and z-pinch plasma sources.
A new multichannel x-ray/extreme ultra violet (EUV) spectrometer is developed for monitoring the time history of x-ray/EUV spectral line intensities from a hot plasma to estimate an electron density and temperature of plasmas. Each independently controlled channel includes a crystal (or multilayer mirror) and a fast x-ray diode. At the same time, an imaging transmission grating is applied to study a spatial distribution of spectral line intensities in a wide spectral region with time gated resolution. The multichannel spectrometer can be applied for measurements of polarization- dependent spectra which will be used for diagnostics of electron beams and measuring a magnetic field in z-pinch plasmas.
The results of the study and application of the prototype of the novel imaging spectrometer with a glass-capillary multiplexer of a 2D x-ray image of Z-pinch plasma are presented. Output channels are used to obtain an array of time-resolved spectra, which covers the full plasma evolution. A spatial resolution of the spectrometer is about 100-250 micrometers for plasma size up to 5 by 20 mm. A spectral resolution is 700-1000. A time-gated resolution is 1-2 ns.
The new calibration x-ray/extreme UV facility for plasma diagnostics and bio-medical x-ray microscopy includes a compact solid state high-repetition laser and a universal, computer controlled target vacuum chamber with calibrated x- ray spectrometers, fast x-ray diodes and time-gated pin-hole cameras. Experimental results are presented.
The Instrumentation Program at Physics Department of the University of Nevada, Reno, USA is based on results of the development and study of one of first glass capillary optics devices in period from 1974 to earlier 90s in USSR/Russia (by V. Kantsyrev, O. Ananyin, Yu. Bykovsky and collaborators). The main direction of our program is the development of several techniques for extreme ultraviolet, soft x-ray and x-ray optical instrumentation, for spectroscopic diagnostics of hot plasmas, spectroscopic studies of interaction of multicharged ion beams with matter, biomedical x-ray microscopy. Our currently-developed instruments include: EUV polarimeter/spectrometer with GCC polarizing and focusing elements; a high resolution, a high-sensitivity EUV and x-ray spectrometer with focusing GCC, that also serves as a high- transmission window for differential vacuum pumping; a prototype of new multiband, two dimensional EUV and x-ray imaging spectrometer for plasma diagnostics; a pinhole camera with GCC using as a hard x-ray filter; a soft x-ray spectrograph with MLM for plasma diagnostics.
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