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International audience; A new compact Z-pinch x-ray hohlraum design with parallel-driven x-ray sources was experimentally demonstrated in a full configuration with a central target and tailored shine shields (to provide a symmetric temperature distribution on the target) at the 1.7 MA Zebra generator. This presentation reports on the joint success of two independent lines of research. One of these was the development of new sources – planar wire arrays (PWAs). PWAs turned out to be a prolific radiator. Another success was the drastic improvement in energy efficiency of pulsed-power systems, such as the Load Current Multiplier (LCM). The Zebra/LCM generator almost doubled the plasma load current to 1.7 MA. The two above-mentioned innovative approaches were used in combination to produce a new compact hohlraum design for ICF, as jointly proposed by SNL and UNR. Good agreement between simulated and measured radiation temperature of the central target is shown. Experimental comparison of PWAs with planar foil liners (PFL) - another viable alternative to wire array loads at multi-MA generators show promising data. Results of research at the University of Nevada Reno allowed for the study of hohlraum coupling physics at University-scale generators. The advantages of new hohlraum design applications for multi-MA facilities with W or Au double PWAs or PFL x-ray sources are discussed.

A study of Na-like satellite structure to Ne-like resonance lines was made in detail for Co, Ni, Cu, Zn ions having intermediate nuclear charge. To record the x-ray spectra, a pulsed laser plasma source was used with various duration and pulse shapes. More than 20 experimental spectral lines were identified belonging to the 2p?3s, 2p?3d, 2s?3p transitions based on comparison with YODA code calculations. To decrease the overlapping of the spectra with lower charge state ions such as O-like ions, the duration and shape of the laser pulse was varied.

Theoretical and experimental investigations were made of the properties of simple glass-capillary converters (GCCs), which can be used to transport soft x-ray (SXR) beams and alter their cross sections. The conditions during propagation of SXR beams in a capillary were considered for an arbitrary position of a compact source, relative to the position of the entry face of the capillary. The characteristics of transport of SXR beams in a close-packed capillary bundle were also studied. An experimental investigation was made of the dependences of the GCC efficiency and transmission, and also of the SXR beam divergence at the exit from GCCs of different types, on the wavelength and on the distance from the source to the entry face of a GCC. A reasonable agreement between the calculated and experimental data was achieved. It was found experimentally that a pinhole camera with a GCC could be used in pinhole photography of dense hot plasmas. This method can deliver plasma images without the distorting influence of hard x rays emitted by a plasma. Simple and inexpensive bundle GCCs are suitable in those cases when the use of multilayer x-ray mirrors of zone plates is undesirable.

We have measured the coefficients of reflection of KrF-laser radiation from a silicon surface, and also from its coating films SiO2, Al, PSG, and their combinations. We have shown that specular reflection from a silicon surface with various films can vary in intensity not only on account of the change of absorption in the material, but also as a result of scattering of the radiation by the surface waves that are rapidly produced after the silicon melting.

The presented research focuses on investigation of Z‐pinch plasma formation, implosion, and radiation characteristics as a function of the load configuration. The single planar and multi‐planar wire arrays as well as compact cylindrical wire arrays were studied on the 1.3 MA UNR Zebra and 1 MA Cornell COBRA generators. The largest yields and powers were found for W and Mo double planar and compact wire arrays. A possibility of radiation pulse shaping was demonstrated. Two types of bright spots were observed in plasmas. A comparison of Mo double planar and compact wire array data indicates the possibility that the same heating mechanism operates during the final implosion and stagnation stages.

The implosion dynamics of wire array loads of complex geometry, such as nested cylindrical and planar wire arrays, is significantly affected by the uneven current distribution between the array wires, which was considered previously in the Wire Dynamics Model (WDM) simulations. The novel Wire Ablation Dynamics Model (WADM) extends the formalism of the original WDM by including the dynamics of wire ablation. The WADM simulations demonstrate that the implosions of the arrays with higher masses are more ablation dominated. The WADM simulations of the implosions dynamics of nested wire arrays have been performed for the short pulse (100 ns) and long pulse (220 ns) regimes at COBRA generator. Another factor that affects the result of the trade between the ablation and implosion time scales is the form of the current pulse, which can be very different from the classical sine‐square shape. The predictions of the array implosion times by the WADM are in very good agreement with the recent experiments at the COBRA...

Planar wire arrays are studied at 3–6 MA on the Saturn pulsed power generator as potential drivers of compact hohlraums for inertial confinement fusion studies. Comparison with zero‐dimensional modeling suggests that there is significant trailing mass. The modeled energy coupled from the generator cannot generally explain the energy in the main x‐ray pulse. Preliminary comparison at 1–6 MA indicates sub‐quadratic scaling of x‐ray power in a manner similar to compact cylindrical wire arrays. Time‐resolved pinhole images are used to study the implosion dynamics.

Analysis is presented on scaling of radiated x‐ray power, energy and implosion timing of single planar wire arrays (SPWA), double planar wire array (DPWA), and compact cylindrical wire array (CCWA) loads (diameter is 3 and 6 mm) of Mo and W with respect to current peak (0.8–1.4 MA), mass and array dimensions at 100 ns current pulse. Such scaling investigations are important for understanding the potential of these loads as an ICF radiation source7. These data are used to identify promising directions to pursue with regard to highest x‐ray output, smallest load size, and most consistent shot‐to‐shot performance. It is shown that W SPWA and DPWA total energy yield and peak power increased near‐quadratically with current. DPWA scans of inter‐planar gaps from 1.5 mm to 9 mm show an output maximum at 1.5 mm with decreasing output for 6 mm and 9 mm. A DPWA width scan shows that radiation yields decrease slowly as the width is decreased, which may allow for more compact loads without significant sacrifice to the...

Implosions from compact cylindrical wire arrays (CCWA) with mid‐Z and low‐Z wires were carried out on the 1‐MA COBRA generator at Cornell University. In particular, the CCWA used either Brass 310 (70% Cu, 30% Zn) wires or a combination of Brass 310 and Al 5056 (95% Al, 5% Mg) wires arranged in an alternating pattern. A total of 16 wires were used on either a 6 or 4 mm diameter array. The diagnostic suite included a bolometer, fast x‐ray detectors, a time‐integrated spectrometer, and a streak camera. A higher energy output was observed from bolometer measurements when alternating the brass and Al wires compared to using only the brass wires. This study will focus mainly on the spectroscopy of the brass and alternating brass and Al CCWA by applying the non‐LTE kinetic models of Cu and Zn to account for the L‐shell radiation. The resulting plasma parameters, electron density and electron temperature, will be discussed and compared for the CCWA with only brass wires and alternating brass and Al wires. The sim...

University‐scale Z‐pinch generators are able to produce plasmas with a broad range of temperatures, densities, and opacity properties depending on the type, size, and mass of wire‐array loads and wire materials. Experiments with very different Z‐pinch loads were performed on the 1 MA Zebra generator at UNR and analyzed during the last five years including Single and Nested Cylindrical, Conical, and various types of Planar Wire Arrays. It is shown that such wire arrays are good sources of x‐rays and that they produce significant radiation yield (up to 25 kJ) on a ns time scale, and generate bright spots of sub‐mm size. They can be used for studying radiative properties of moderate density (between 1018 cm−3 and 5×1021 cm−3) and temperature (⩽1.5 keV) plasmas. In addition, X‐pinches generated higher density (>1022 cm−3) and temperature (>2 keV) plasmas on scales as small as a few μm to several mm in size. Wire materials with a broad range of nuclear charge Z were used, ranging from low‐Z, such as alloyed Al wires with varying concentrations of Mg, to mid‐Z, such as Stainless steel, Cu, Brass, and Mo. Uniform (made from one wire material) as well as combined (made from two wire materials with almost equal wire masses) wire arrays were considered. Uniform, combined, symmetric and asymmetric X‐pinches (some of which included a small fraction of tracer Al wires) were also considered. Non‐LTE kinetic models to account for K‐ and L‐shell radiation were employed to understand radiative properties of Z‐pinch and X‐pinch plasmas. Implosion characteristics of such loads are discussed using the wire dynamics and MHD models. Opacity effects of Z‐pinch plasmas are studied and benefits of using alloyed and tracer wires are highlighted.

K‐shell radiation of Al and Mg and L‐shell radiation of Mo from implosions of compact cylindrical wire arrays (CCWA) on the 1 MA UNR Zebra generator was studied. Specifically, radiation from implosions of 3 and 6 mm CCWA with (16–24) Al‐5052 (95% Al and 5% Mg) and Al‐5052 (97.5% Al and 2.5% Mg) and Mo wires was analyzed using the full set of diagnostics: PCD and current signals, and X‐ray pinhole images and spectra. Previously developed non‐LTE models were applied to model spatially resolved time integrated as well as time‐gated spatially integrated spectra from Al, Mg, and Mo plasmas. Derived electron temperature and density spatial gradients as well as percentage of radiating mass were studied and compared. In addition, the novel Wire Dynamics Model (WDM) was used to analyze the implosion dynamics of compact wire array loads.

The Load Current Multiplier concept (LCM) was validated for the first time on a high‐voltage nanosecond pulse‐power generator. The designed new device allowed to increase the load current from the nominal 0.8–0.9 MA up to 1.6 MA in static loads with constant inductance and up to 1.4 MA in a planar wire‐array plasma loads. These results were achieved without modifying the generator energetic or architecture. LCM allowed both the load magnetic energy increase and the increase of soft X‐ray radiation from z‐pinch plasmas.

Experiments with different stainless steel (SS) wire loads were performed on the 1 MA Zebra Z‐pinch generator at University of Nevada, Reno. The wire array loads consisted of 7.6 μm SS wires and had 10 wires for the planar wire array with an interwire gap of 1 mm and 8 wires for the cylindrical wire array of a 16 mm diameter. In addition, a single‐wire experiment with a 25 μm SS wire was carried out. The different wire loads were used to provide a broader spectrum of plasma conditions. Time‐integrated and time‐gated x‐ray images, as well as time‐integrated, spatially‐resolved and spatially‐integrated x‐ray spectra, were collected and analyzed. Both K‐shell and L‐shell radiation were recorded using LiF and KAP crystal spectrometers, respectively. Non‐LTE kinetic models of Fe and Ni are employed to derive plasma parameters. For axially resolved L‐shell spectra, the resulting electron temperatures are between 230 and 300 eV (higher near the cathode) and electron densities vary from 1019 to 1020 cm−3 dependen...

Experiments with cylindrical copper wire arrays at the 1-MA Zebra facility show that high temperatures exist in the precursor plasmas formed when ablated wire array material accretes on the axis prior to the stagnation of a z pinch. In these experiments, the precursor radiated approximately 20% of the1000 eV x-ray output, and time-resolved spectra show substantial emission from Cu L-shell lines. Modeling of the spectra shows an increase in temperature as the precursor forms, up to approximately 450 eV, after which the temperature decreases to approximately 220-320 eV until the main implosion.

Summary form only given. It is well known that implosions of X-pinches and wire arrays produce the powerful laboratory X-ray sources. X-ray spectroscopy is a very useful tool for diagnostics of X-and Z-pinch plasmas at stagnation while EUV spectroscopy seems to be an appropriate tool of diagnosing the plasma before and after the stagnation. Though X-ray spectra that characterize the stagnating plasmas are intensively used for X-and Z-pinch plasma diagnostics the EUV spectra are not vet studied in detail. In the present work a collection of EUV spectra from implosions of very different X-and Z-pinch loads on the 1 MA Zebra generator at UNR is presented for the first time. Specifically, the loads were Al X-pinches with 2 and 4 wires, cylindrical wire arrays (with and without a small portion of NaF coating), and planar wire arrays. The Al wires were from Al 5056 (95% Al and 5% Mg) and Al 1100 (99% Al) alloys. Non-LTE kinetic models of Al as well as Mg that were recently used to model X-ray K-shell Al and Mg spectra from the same loads were applied here to calibrate and identity the EUV spectra. Preliminary plasma parameters were computed. Similar and different features of the EUV spectra as well as corresponding plasma parameters from the above-mentioned loads were identified and analyzed. Modification of the existing models for the best fit of EUV spectra is discussed.

Experiments to study the implosion dynamics and radiation characteristics of copper z‐pinches have been fielded at the 1 MA Zebra facility and the 20 MA Z facility. The impact of initial load mass, initial load diameter, and nesting of wire arrays on the precursor and the stagnated plasma has been evaluated through spectroscopy, shadowgraphy, and fluence measurements. Plasma parameters extracted from modeling of the time‐integrated L‐shell spectra indicate the presence of more than one plasma source contributing to the radiation, likely due to non‐uniform hot spot x‐ray emission or temporal gradients.

Theoretical and experimental investigations were made of the properties of glass-capillary concentrators of soft x-ray radiation designed to transport and focus this radiation from sources with a small emitting region. The transmission coefficients of the capillaries operating in the range 0.6 < λ < 5.1 nm were calculated for glasses of different chemical compositions and a fixed angle of bending of the capillary. The efficiency ν of concentration of the 0.3 < λ < 5.1 nm radiation and the optimal radiation entry angle Ψ, ensuring maximum ν, were also calculated. The values of ν for a concentrator of x-rays from a plasma source, determined experimentally in the range 0.4 < λ < 1.0 nm, were in satisfactory agreement with the theoretical predictions. A strong dependence of the parameters of glass-capillary concentrators on the chemical composition of the glass was observed even at impurity concentrations as low as 3%—4%.

This paper presents a detailed investigation of the temporal, spatial, and spectroscopic properties of L-shell radiation from 0.8 to 1.0 MA Mo x pinches. Time-resolved measurements of x-ray radiation and both time-gated and time-integrated spectra and pinhole images are presented and analyzed. High-current x pinches are found to have complex spatial and temporal structures. A collisional-radiative kinetic model has been developed and used to interpret L-shell Mo spectra. The model includes the ground state of every ionization stage of Mo and detailed structure for the O-, F-, Ne-, Na-, and Mg-like ionization stages. Hot electron beams generated by current-carrying electrons in the x pinch are modeled by a non-Maxwellian electron distribution function and have significant influence on L-shell spectra. The results of 20 Mo x-pinch shots with wire diameters from 24 to 62 microm have been modeled. Overall, the modeled spectra fit the experimental spectra well and indicate for time-integrated spectra electron densities between 2 x 10(21) and 2 x 10(22) cm(-3), electron temperatures between 700 and 850 eV, and hot electron fractions between 3% and 7%. Time-gated spectra exhibit wide variations in temperature and density of plasma hot spots during the same discharge.

It is shown by using the scalar diffraction theory and the method of images that the arbitrary field confined by the optical waveguide can be generated in free space by the appropriate light source. The correspondence between the guided and free-space waves is illustrated using several particular fields, such as the diffraction-free, self-imaging, ultra-short, solitonlike, partially coherent waves and laser fractals. In opposition to the eigenmode theory of waveguides, the field at the guide entrance can satisfy neither the guide wave-equation nor the boundary conditions.

The results are presented dealing with the study of the SXR compact source of the new type based on the typical “gas‐puff ” one. The source has the value of the conversion coefficient of initial energy supply into SXR minus; η =(1−2);·10−2 and averaged effective size of emission region‐ d = 2–3 mm, what is better the traditional ones of “gas‐puff ” have. The new one has also greater resource (in two‐three orders greater) comparing with widely‐used low‐inductance vacuum spark.An improvement of the source characteristics was achieved as result of realization of mixed regime of micropinching of heavy ‐ current discharge when plasma points are appeared both in plasma of compressed gas liner and plasma of anode vapor.

The results are presented dealing with the working out and study of the plasma source of soft X‐ray (SXR) of the new type.Experimental set up included compact low‐inductance vacuum spark (LIVS) with initial energy supply equal up to 2.5 kJ and glass‐capillary concentrator (GCC) of SXR. The characteristics of SXR of vacuum spark and properties of SXR were studied using diagnostic complex. The coefficient of conversion of initial energy supply into SXR (η) amounted to 0.01 in range 1.2nm. Value η had peak dependence on atomic number of anode Za. The spectra were recorded belonging to Ne‐like, F‐like ions of Fe, Cu ions and He‐like, H‐like ions of Al, Ti, Fe.Glass capillary concentrator consists of about several hundreds glass capillaries Flux density of SXR in focusing spot was up to 105–106 Wt/cm, density of energy is up to 20–30 mJ/cm2 at diameter of SXR focusing spot equal to about 2–3mm in the range 0.7–1.0 nm.The plasma source of the new type is intended for X‐ray microscopy, study of influence of SXR ...

Results are presented of investigations of the characteristics of the soft x-ray emission from a plasma formed using lasers having parameters similar to those available commercially. An investigation was made of the dependences of the soft x-ray emission characteristics on the laser power, atomic number of the target, target configuration, diameter of the laser radiation focusing spot on the target, and laser radiation wavelength. A method of measuring the electron temperature of a laser plasma is proposed.

The results are reported of an investigation of soft x rays emitted from a laser plasma. The aim was to study the physics of the phenomenon and to develop a source of soft x rays for practical applications. Some parameters of the laser plasma were determined, including the efficiency of conversion of the laser energy into soft x rays, spectral and spatial distributions of the radiation emitted by the laser plasma, and size of the region emitting this radiation. It was found that, within a certain range, it was possible to control the size of the radiating part of the laser plasma. A comparison was made of the resolution of x-ray photographic films in the wavelength range corresponding to soft x rays and in the visible range. A neodymium glass laser was used. Soft x rays were recorded by means of films sensitive to x rays. Potential applications of the laser plasma as a pulse source of soft x rays are considered and some requirements to be satisfied by such a source are formulated.

The paper analyses and illustrates experimentally the possibilities of using the method of microroentgenography for the analysis of the structure and element composition of thin sections of biological tissues. Soft roentgen radiation of laser plasma formed by focusing of a sufficiently powerful laser impulse on the surface of a solid-body target is used. The method requires no preliminary treatment of the specimens.