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Talbot–Lau x-ray interferometry is a refraction-based diagnostic that can map electron density gradients through phase-contrast methods. The Talbot–Lau x-ray deflectometry (TXD) diagnostics have been deployed in several high energy density experiments. To improve diagnostic performance, a monochromatic TXD was implemented on the Multi-Tera Watt (MTW) laser using 8 keV multilayer mirrors (Δθ/θ = 4.5%-5.6%). Copper foil and wire targets were irradiated at 1014–1015 W/cm2. Laser pulse length (∼10 to 80 ps) and backlighter target configurations were explored in the context of Moiré fringe contrast and spatial resolution. Foil and wire targets delivered increased contrast

Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High Energy Density Physics (HEDP) experiments. X-ray backlighter targets have been evaluated for Talbot-Lau X-ray Deflectometry (TXD). Cu foils, wires, and sphere targets have been irradiated by 10–150 J, 8–30 ps laser pulses, while two pulsed-power generators (∼350 kA, 350 ns and ∼200 kA, 150 ns) have driven Cu wire, hybrid, and laser-cut x-pinches. A plasma ablation front generated by the Omega EP laser was imaged for the first time through TXD for densities >1023 cm−3. Backlighter optimization in combination with x-ray CCD, image plates, and x-ray film has been assessed in terms of spatial resolution and interferometer contrast for accurate plasma characterization through TXD in pulsed-power and high-intensity laser environments. The results obtained thus far demonstrate the potential of TXD as a powerful diagnostic for HEDP.

Talbot–Lau x-ray interferometry is a grating-based phase-contrast technique, which enables measurement of refractive index changes in matter with micrometric spatial resolution. The technique has been established using a variety of hard x-ray sources, including synchrotron, free-electron lasers, and x-ray tubes, and could be used in the optical range for low-density plasmas. The tremendous development of table-top high-power lasers makes the use of high-intensity, laser-driven K-alpha sources appealing for Talbot–Lau interferometer applications in both high-energy-density plasma experiments and biological imaging. To this end, we present the first, to the best of our knowledge, feasibility study of Talbot–Lau phase-contrast imaging using a high-repetition-rate laser of moderate energy (100 mJ at a repetition rate of 10 Hz) to irradiate a copper backlighter foil. The results from up to 900 laser pulses were integrated to form interferometric images. A constant fringe contrast of 20% is demonstrated over 100 accumulations, while the signal-to-noise ratio continued to increase with the number of shots. Phase retrieval is demonstrated without prior ex-situ phase stepping. Instead, correlation matrices are used to compensate for the displacement between reference acquisition and the probing of a PMMA target rod. The steps for improved measurements with more energetic laser systems are discussed. The final results are in good agreement with the theoretically predicted outcomes, demonstrating the applicability of this diagnostic to a range of laser facilities for use across several disciplines.

Interferometry is one of the most sensitive and successful diagnostic methods for plasmas. However, owing to the design of most common interferometric systems, the wavelengths of operation and, therefore, the range of densities and temperatures that can be probed are severely limited. Talbot–Lau interferometry offers the possibility of extending interferometry measurements to x-ray wavelengths by means of the Talbot effect. While there have been several proof-of-concept experiments showing the efficacy of this method, it is only recently that experiments to probe High Energy Density (HED) plasmas using Talbot–Lau interferometry are starting to take place. To improve these experimental designs, we present here the Talbot-Interferometry Analyzer (TIA) tool, a forward model for generating and postprocessing synthetic x-ray interferometry images from a Talbot–Lau interferometer. Although TIA can work with any two-dimensional hydrodynamic code to study plasma conditions as close to reality as possible, this software has been designed to work by default with output files from the hydrodynamic code FLASH, making the tool user-friendly and accessible to the general plasma physics community. The model has been built into a standalone app, which can be installed by anyone with access to the MATLAB runtime installer and is available upon request to the authors.

Talbot–Lau x-ray deflectometry (TXD) enables refraction-based imaging for high-energy-density physics experiments, and thus, it has been studied and developed with the goal of diagnosing plasmas relevant to inertial confinement and magnetic liner inertial fusion. X-pinches, known for reliably generating fast (∼1 ns), small (∼1 µm) x-ray sources, were driven on the compact current driver generator for ablation structure and implosion studies (∼200 kA, 150 ns) as a potential backlighter source for TXD. Considering that different X-pinch configurations have characteristic advantages and drawbacks as x-ray generating loads, three distinct copper X-pinch configurations were studied: the wire X-pinch, the hybrid X-pinch, and the laser-cut X-pinch. The Cu K-shell emission from each configuration was characterized and analyzed regarding the specific backlighter requirements for an 8 keV TXD system: spatial and temporal resolution, number of sources, time of emission, spectrum, and reproducibility. Recommendations for future experimental improvements and applications are presented. The electron density of static objects was retrieved from Moiré images obtained through TXD. This allowed to calculate the mass density of static samples within 4% of the expected value for laser-cut X-pinches, which were found to be the optimal X-pinch configuration for TXD due to their high reproducibility, small source size (⩽5 µm), short duration (∼1 ns), and up to 106 W peak power near 8 keV photon energy. Plasma loads were imaged through TXD for the first-time using laser-cut X-pinch backlighting. Experimental images were compared with simulations from the x-ray wave-front propagation code, demonstrating that TXD can be a powerful x-ray refraction-based diagnostic for dense Z-pinch loads. Future plans for Talbot–Lau interferometry diagnostics in the pulsed-power environment are described.

A Talbot-Lau X-ray Deflectometer (TXD) was implemented in the OMEGA EP laser facility to characterize the evolution of an irradiated foil ablation front by mapping electron densities >1022 cm-3 by means of Moire deflectometry. The experiment used a short-pulse laser (30-100 J, 10 ps) and a foil copper target as an x-ray backlighter source. In the first experimental tests performed to benchmark the diagnostic platform, grating survival was demonstrated and x-ray backlighter laser parameters that deliver Moire images were described. The necessary modifications to accurately probe the ablation front through TXD using the EP-TXD diagnostic platform are discussed.

International audience; We describe a platform developed on the LULI2000 laser facility to investigate the evolution of Rayleigh-Taylor instability (RTI) in scaled conditions relevant to young Supernovae Remnant (SNR) up to 200 years. An RT unstable interface is imaged with a short-pulse laser-driven (PICO2000) x-ray source, providing an unprecedented simultaneous high spatial (24 µm) and temporal (10 ps) resolution. This experiment provides relevant data to compare with astrophysical codes, as observational data on the development of RTI at the early stage of the SNR expansion are missing. A comparison is also performed with FLASH radiative magneto-hydrodynamic simulations.

We present the development and advancement of the Talbot–Lau X-ray deflectometry (TXD) single-image phase-retrieval technique, for high-energy density (HED) plasma diagnostics. The Talbot–Lau interferometer has been benchmarked as an electron density diagnostic for low- $Z$ objects ( $Z ) at the X-ray energies of 8 and 17 keV. A laser driven X-ray backlighter was used at the multi-tera watt laser facility in order to obtain electron density measurements. We measured X-ray refraction and retrieved sharp and smooth density gradients with source-limited spatial resolution. Since TXD can use extended, incoherent, line, or continuum X-ray sources, a wide range of X-ray backlighters can be used, driven from laser or pulsed power systems. Laboratory results indicate potential for simultaneous retrieval of: electron density maps through refraction and attenuation, material mixing through elemental composition, and instabilities through scatter images. Experiments using a 17-keV backlighter to characterize a planar shock are planned to test the TXD technique on an HED plasma environment.

Wire X-pinches (WXPs) have been studied comprehensively as fast ( ∼ 1 ns pulse width), small ( ∼ 1 μm) x-ray sources, created by twisting two or more fine wires into an “X” to produce a localized region of extreme magnetic pressure at the cross-point. Recently, two alternatives to the traditional WXP have arisen: the hybrid X-pinch (HXP), composed of two conical electrodes bridged by a thin wire or capillary, and the laser-cut foil X-pinch (LCXP), cut from a thin foil using a laser. We present a comparison of copper wire, hybrid, and laser-cut foil X-pinches on a single experimental platform: UC San Diego’s ∼ 200 kA, 150 ns rise time GenASIS driver. All configurations produced 1–2 ns pulse width, ≤ 5 μm soft x-ray (Cu L-shell, ∼ 1 keV) sources (resolutions diagnostically limited) with comparable fluxes. WXP results varied with linear mass and wire count, but consistently showed separate pinch and electron-beam-driven sources. LCXPs produced the brightest ( ∼ 1 MW), smallest ( ≤ 5 μm) Cu K-shell sources, and spectroscopic data showed both H-like Cu K α lines indicative of source temperatures ≥ 2 keV, and cold K α ( ∼ 8050 eV) characteristic of electron beam generated sources, which were not separately resolved on other diagnostics (within 1–2 ns and ≤ 200 μm). HXPs produced minimal K-shell emission and reliably single, bright, and small L-shell sources after modifications to shape the early current pulse through them. Benefits and drawbacks for each configuration are discussed to provide potential X-pinch users with the information required to choose the configuration best suited to their needs.

A Talbot–Lau x-ray deflectometer can map electron density gradients in high energy density plasmas, as well as provide information about plasma elemental composition through single-image x-ray refraction and attenuation measurements. A new adaptation to a pulsed power environment used backlighting from copper X-pinches, allowing for electron density mapping of a low-Z object. Even though the X-pinch backlighter is not properly optimized for emitting x-rays in terms of source size and photon fluence, Moire fringe patterns with contrast up to 14% and fringe shift due to refraction on a beryllium object are obtained. Due to the proximity of the deflectometer with the X-pinch (∼6 cm), it is shown that a protective filter is required to avoid damage in the closest (i.e., source) grating due to both plasma debris and mechanical shock. Regarding grating survival, these did not show any damage due to the intense magnetic field or heating induced by plasma radiation. Electron density on beryllium was measured with a difference lower than 16%. The areal electron density mapping of the sample was limited by source size characteristics, in similarity to transmission radiography. These results show the potential of plasma electron density as well as material mapping through Talbot–Lau x-ray deflectometry in a pulsed power environment.

Talbot-Lau X-ray Deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The diagnostic delivers refraction, attenuation, elemental composition, and scatter information from a single-shot Moire image. A Talbot-Lau interferometer was benchmarked using laser-target and X-pinch x-ray backlighters. Grating survival and electron density mapping were demonstrated for: a) 25–60 J, 8–30 ps laser pulses using copper targets and b) X-pinches driven by a ~350kA/350ns generator. X -ray backlighter quality was assessed in order to optimize areal electron density gradient retrieval and electron density mapping. TXD enabled accurate areal electron density detection with high contrast (>25%) and spatial resolution of $\sim 50\mu \mathrm{m}$ in the high-power laser experiments, while a higher spatial resolution $ and lower contrast (

Electron beams produced by the hollow cathode effect are studied in a compact gas filled 24-kV, 5-kA capillary discharge. The characteristics and role of electron beams on X-ray production are studied in order to better understand their impact on X-ray production. X-ray plasma emission is analyzed with a spectrometer, while wideband diodes and Faraday cup probe both electron beams and X-rays. Electron beams of >5 keV are observed early on the discharge and two types of electron beams are identified: a first beam of high energy and low current (with a speed of $\sim 5 \times 10^{7}$ m/s and a current density of $\sim 4\times 10^{\mathrm {-2}}$ A/cm $^{2})$ enhanced by larger cathode apertures, and a second beam of low energy and high current enhanced by smaller cathode apertures. The use of a simple configuration of external magnets prevents X-ray fluorescence production, caused by electron beams, from reaching electronic detectors hence confusion when evaluating X-ray yield from the plasma source is avoided. This is particularly important in extreme ultraviolet lithography and soft X-ray production applications. Furthermore, the presence of the external magnets does not modify line emission, which is detected by means of spectrometry. Therefore, the use of external magnets provides a way to discriminate X-ray diode signals produced by source emitted X-rays and X-ray fluorescence from electron beams.

Talbot-Lau x-ray interferometry uses incoherent x-ray sources to measure refraction index changes in matter. These measurements can provide accurate electron density mapping through phase retrieval. An adaptation of the interferometer has been developed in order to meet the specific requirements of high-energy density experiments. This adaptation is known as a moire deflectometer, which allows for single-shot capabilities in the form of interferometric fringe patterns. The moire x-ray deflectometry technique requires a set of object and reference images in order to provide electron density maps, which can be costly in the high-energy density environment. In particular, synthetic reference phase images obtained ex situ through a phase-scan procedure, can provide a feasible solution. To test this procedure, an object phase map was retrieved from a single-shot moire image obtained from a plasma-produced x-ray source. A reference phase map was then obtained from phase-stepping measurements using a continuous x-ray tube source in a small laboratory setting. The two phase maps were used to retrieve an electron density map. A comparison of the moire and phase-stepping phase-retrieval methods was performed to evaluate single-exposure plasma electron density mapping for high-energy density and other transient plasma experiments. It was found that a combination of phase-retrieval methods can deliver accurate refraction angle mapping. Once x-ray backlighter quality is optimized, the ex situ method is expected to deliver electron density mapping with improved resolution. The steps necessary for improved diagnostic performance are discussed.

Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moire image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moire pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, ∼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

X-ray phase-contrast techniques can measure electron density gradients in high-energy-density plasmas through refraction induced phase shifts. An 8 keV Talbot-Lau interferometer consisting of free standing ultrathin gratings was deployed at an ultra-short, high-intensity laser system using K-shell emission from a 1-30 J, 8 ps laser pulse focused on thin Cu foil targets. Grating survival was demonstrated for 30 J, 8 ps laser pulses. The first x-ray deflectometry images obtained under laser backlighting showed up to 25% image contrast and thus enabled detection of electron areal density gradients with a maximum value of 8.1 ± 0.5 × 10(23) cm(-3) in a low-Z millimeter sized sample. An electron density profile was obtained from refraction measurements with an error of8%. The 50 ± 15 μm spatial resolution achieved across the full field of view was found to be limited by the x-ray source-size, similar to conventional radiography.

Phase-contrast x-ray diagnostics can detect density gradients in low-Z matter with the sensitivity and spatial resolution required in High Energy Density (HED) plasma experiments. Talbot-Lau interferometry measures x-ray beam deviations due to refraction index gradients in its path. It can simultaneously provide x-ray attenuation, refraction, elemental composition, and scatter images of a low-Z object. We have developed the Talbot-Lau Moire X-ray Deflectometry (TXD) single image technique based on phase-retrieval. The results obtained at 8 and 17 keV with high magnification using low-Z test objects suggest a clear advantage of TXD as HED electron density diagnostic over conventional radiography. The Moire technique can detect sharp and smooth density gradients with source-limited spatial resolution. Also, TXD can use extended, incoherent, line or continuum x-ray sources, allowing for a wide range of backlighters.

For the first time an x-ray Talbot-Lau moire deflectometer is being developed that will use a flash tube source and fast detector for dynamic density gradient measurements. In Talbot-Lau moire deflectometry, an x-ray grating makes an image of itself on a second grating (the Talbot effect) to produce a moire pattern on a detector. The test object is placed between these gratings, with variations in index of refraction changing the pattern. A third grating in front of an incoherent x-ray source produces an array of coherent sources. With a 150 kV x-ray flash tube as the source, the gratings are placed in a glancing angle setup for performance at ∼60 keV. The detector is a gated CCD with a fast scintillator for x-ray conversion. This diagnostic, designed for the Dual-Axis Radiographic Hydrodynamic Test facility (DARHT) at Los Alamos National Laboratory, measures the density profile of dense plasma plumes ejected from beam-target interactions. DARHT has two high-current, pulsed, inductive linear electron accelerators with bremsstrahlung targets at the end of each beam line to create 2-D radiographic images of hydrodynamic tests. One multi-pulse accelerator has up to four beam pulses striking the same target within 2 μβ. Computer simulations that model target evolution and ejected material between pulses are used to design these targets for optimal radiographic performance; the x-ray deflectometer will directly measure density gradients in the ejected plumes and provide the first experimental constraints to these models. During the first year, currently underway, the diagnostic systems are being designed. In year two, the flash tube and fast detector will be deployed at DARHT for radiographic imaging while the deflectometer is built and tested on the bench with a continuous source. In year three, the fast deflectometer will be installed on DARHT and density measurements will be performed.

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moire deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moire fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

Phase-contrast x-ray diagnostics can detect density gradients in low-Z matter with the sensitivity and spatial resolution necessary to characterize High Energy Density Plasma (HEDP) experiments. Talbot-Lau interferometry measures x-ray beam angular deviations due to refraction index gradients along its path and can simultaneously provide x-ray attenuation, refraction, and scatter images of an object. We have extended the Talbot-Lau method from the low magnification and high energy (30–100 keV) setup used in medical applications, to the high magnification and low energy (8–20 keV) setup HEDLP experiments require. We also developed single image based phase-retrieval techniques such as Talbot-Lau Moire deflectometry. The results obtained using low-Z test objects suggest a clear advantage of Talbot-Lau Moire deflectometry over conventional radiography for density diagnostic in HEDP. The Moire technique can detect with good spatial resolution both sharp and smooth density gradients, and can use incoherent, extended x-ray sources emitting either lines or continuum, thus allowing for a wide range of backlighters.

Summary form only given. We present results examining the dynamics of low current (25kA), long rise-time (400 ns) X-pinches. These are the lowest parameters yet used for X-pinch experiments. The X-pinches comprised either 2 or 4 wires of 5μm tungsten. We analyze coronal and axial plasma dynamics, cross-point evolution, X-ray emission, and post-pinching dissipation of the structure. Data shows that the pinch dynamics produced here is akin to those in X-pinches driven by 0.1-1 MA and at rise-rates from 0.25-10kA/ns. Silicon PIN diodes detected X-rays (~1-2keV range) emitted from the cross point in both the two-wire and four-wire configurations near peak current. These results suggest that compact pulsed power drivers consisting of 2-4 small capacitors in a simple capacitive discharge circuit can produce good quality pinches for a variety of possible applications including point-projection radiography, Thompson X-ray scattering, and laboratory astrophysical modeling. Additionally, we will present a model for determining the emission time of harder x-rays due to the onset of anomalous resistivity.

Phase-contrast x-ray imaging techniques can detect density gradients in low-Z matter with the sensitivity and spatial resolution necessary to characterize High Energy Density Laboratory Plasma (HEDLP) experiments. The Talbot-Lau interferometer measures x-ray beam angular deviations due to refraction index gradients along its path, thus making it an attractive plasma diagnostic. The Talbot-Lau interferometer can simultaneously provide x-ray attenuation, refraction, and scatter images which may offer a simple diagnostic for micro instabilities. We extend the Talbot-Lau method used for medical applications to lower x-ray energies, high magnification and high spatial resolution HEDLP experiments require. We study and develop single image based phase-retrieval techniques. The experimental and simulated results obtained show a clear advantage of the Talbot-Lau Moire technique over the attenuation and propagation methods. The Moire technique can detect both sharp and smooth density gradients, using extended, polychromatic, incoherent, line and continuum x-ray sources, thus allowing for less demanding backlighters than those typically used in HEDLP radiography.

We report on experimental observations of pulsed capillary discharges aimed at soft x-ray production within the water-window range. Through systematical studies of capillary tube characteristics and discharge conditions, radiation emission was analysed. Plasma properties were studied by means of spectrometry, wide-band PIN diode signals and plasma micro-channel plate imaging. Surface and bulk material analyses were performed using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) in order to characterize the capillary inner surface after discharges. We report on hollow cathode effect enhancement by modification of cathode electrode aperture, as well as pressure conditions along the capillary, which were found to have an important effect over plasma and x-ray yields due to the modification of local electrical field and gas density. Capillary tube material and inner diameter also modified the interaction of the plasma channel with the capillary surface, thus modifying the plasma source characteristics. It was found that emission of the NVI line at 28.8 A can be enhanced within the conditions studied, from no significant emission to sources delivering an average brightness of over 70.0 mW mm−2 per 2π sr. This demonstrates that hollow cathode electrons and plasma–wall interaction and ablation have a direct impact on emission quality.

Summary form only given. A series of observations using soft X-rays and optical techniques diagnose key plasma parameters in a low inductance large aspect ratio fast capillary discharge. The capillary discharge is operated with less than 1 Joule of stored electrical energy and is designed for fast repetition rate operation. Peak current is between 5 and 8 kA with a quarter period between 8 and 11 ns. The energy storage capacitor is directly charged during 1µs. Gas is fed into the hollow cathode volume and extracted at the anode, establishing a pressure gradient, which is found to be essential. The pre-breakdown phase is characterized by transient hollow cathode physics, where optical emission from the hollow cathode and measurements of the electron beams that propagate through the cathode orifice and are collimated along the capillary axis to emerge at the anode. The discharges are performed in Xe, Ar, N with admixtures of He. The capillary is of 1.6 mm diameter, either a smooth bore or is segmented with a length of 21 or 16 mm respectively.

Summary form only given. Soft x-ray emission characteristics from a compact pulsed capillary ns discharge are described for a hollow cathode discharge operating in N/He gas mixtures. Different configurations with alumina and nitride capillaries of 21 and 36 mm in length and inner diameters of 1.6 and 3.2 mm were studied. Fast charging from an IGBT based pulsed power circuit stores ~0.5 J and allows operation from 17 to 600 Hz at peak current of ~5 kA for voltages of 10-35 kV. Time-evolution measurements of line emission in the visible range aid in the characterization of plasma dynamics. Time-integrated spectra from 20-200 A show emission of He-like Nitrogen at 28.8 A, representing a possible source for water window soft x-ray microscopy. Spectral contrast with 10-20 eV plasma spectra reveals the influence of axial electron beams, generated by hollow cathode dynamics, in plasma ionization and consequent x-ray emission. Time-of-flight measurements determine fast electrons of ~5 keV are produced in the hollow cathode and filtered diode emission measurements deliver energy output at 28.8 A for the different configurations analyzed. Plasma source size was obtained by MCP images of a filtered slit-wire system, evidencing full wall detachment and good spatial stability. The optimal discharge conditions and system configuration for soft x-ray generation and its enhancement by e-beams production are discussed, as well as the feasibility of this plasma discharge as a table-top soft x-ray source for microscopy applications.

We present the experimental details and results from a low energy but high repetition rate compact plasma capillary source for extreme ultraviolet and soft x-ray research and applications. Two lengths of capillary are mounted in two versions of a closely related design. The discharge operates in 1.6 and 3.2 mm inner diameter alumina capillaries of lengths 21 and 36 mm. The use of water both as dielectric and as coolant simplifies the compact low inductance design with nanosecond discharge periods. The stored electrical energy of the discharge is approximately 0.5 J and is provided by directly charging the capacitor plates from an inexpensive insulated-gate bipolar transistor in 1 μs or less. We present characteristic argon spectra from plasma between 30 and 300 A as well as temporally resolved x-ray energy fluence in discrete bands on axis. The spectra also allow the level of ablated wall material to be gauged and associated with useful capillary lifetime according to the chosen configuration and energy storage. The connection between the electron beams associated with the transient hollow cathode mechanism, soft x-ray output, capillary geometry, and capillary lifetime is reported. The role of these e-beams and the plasma as measured on-axis is discussed. The relation of the electron temperature and the ionization stages observed is discussed in the context of some model results of ionization in a non-Maxwellian plasma.

Moiré fringe deflectometry with grating interferometers is a technique that enables refraction-based x-ray imaging using a single exposure of an object. To obtain the refraction image, the method requires a reference fringe pattern (without the object). Our study shows that, in order to avoid artifacts, the reference pattern must be exactly matched in phase with the object fringe pattern. In experiments, however, it is difficult to produce a perfectly matched reference pattern due to unavoidable interferometer drifts. We present a simple method to obtain matched reference patterns using a phase-scan procedure to generate synthetic Moiré images. The method will enable deflectometric diagnostics of transient phenomena such as laser-produced plasmas and could improve the sensitivity and accuracy of medical phase-contrast imaging.

The Talbot-Lau x-ray moiré deflectometer is a powerful plasma diagnostic capable of delivering simultaneous refraction and attenuation information through the accurate detection of x-ray phase shift and intensity. The diagnostic can provide the index of refraction n=1-δ+iβ of an object (dense plasma, for example) placed in the x-ray beam by independently measuring both δ and β, which are directly related to the electron density n(e) and the attenuation coefficient μ, respectively. Since δ and β depend on the effective atomic number Z(eff), a map can be obtained from the ratio between phase and absorption images acquired in a single shot. The Talbot-Lau x-ray moiré deflectometer and its corresponding data acquisition and processing are briefly described to illustrate how the above is achieved; Z(eff) values of test objects within the 4-12 range were obtained experimentally through simultaneous refraction and attenuation measurements. We show that Z(eff) mapping of objects does not require previous knowledge of sample length or shape. The determination of Z(eff) from refraction and attenuation measurements with moiré deflectometry could be of high interest to various domains of high energy density research, such as shocked materials and inertial confinement fusion experiments, as well as material science and nondestructive testing.

We report on results from experiments using laser-cut X shaped foils (or foil X-pinches) driven by the 250 kA, 150 ns rise-time GenASIS Linear Transformer Driver. Optical probing of the laser-cut foil X-pinches shows considerable dynamic and qualitative similarity with the more traditional wire X-pinches. Results demonstrate excellent quality X-ray emission flux, timing, and source size. The foil X-pinches offer advantages such as improved, reproducible cross-point symmetry, and the opportunity for rep-rated operation, which is not possible with conventional X-pinches using wires.

We present results from a pulsed capillary ns discharge source, operated in Nitrogen and N/He mixtures, in an alumina capillary 2.1mm long with outer diameter of 6.3mm and inner diameter of 1.6mm. The electrical energy stored is 0.5J with peak current of 6kA. Fast charging from an IGBT based pulsed power circuit allows operation at 35-600 Hz with voltages in the range of 18-24kV. Characteristic time-integrated N/He spectra were recorded and analyzed for values of 20-200 A, with clear evidence of He-like Nitrogen emission at 28.8A, which represents a possible source for water window soft x-ray microscopy. Filtered diode measurements reveal the influence of axial electron beams, generated by hollow cathode dynamics, on the x-ray emission in the range of 300-450 eV. We discuss optimal voltage applied and pressure conditions for soft x-ray generation. Time-integrated MCP images of a filtered slit-wire system delivered clear evidence of full wall detachment with ~500μm in radial size for the entire emission range and ~200μm for the emission in the 300-450 eV range.

A fast nanosecond capillary discharge for fast repetition rate operation has been designed and tested. Operated in Ar and Ar/He mixtures X-ray emission from ionization stages from Ar VIII to XII have been observed according to capillary dimensions and operating voltages. Intense electron beams are formed as a result of the transient hollow cathode effect. The emission characteristics are presented for capillaries of two lengths, 21 and 26 mm, and at three diameters, 0.8, 1.6 and 3.2 mm. In addition, time resolved observations allow comparison of theory and experiment of the emission in relation to the current and applied voltage. We find from the spectra a strong dependence on the capillary dimensions, capillary operating conditions such as voltage, gas mix and pressure, diameter and length with clear evidence of wall ablation under some conditions. This has important consequences on the long term reliability of the discharge. The energy output at 4.9 nm (Ar IX emission) and the in-band (13.5 nm 1%) is also presented.

X-ray phase-contrast radiography could better characterize highly localized density gradients expected in High Energy Density (HED) plasma experiments than conventional attenuation radiography. In particular, the Talbot-Lau (TL) grating interferometer, which works with extended and polychromatic x-ray sources, is a potentially attractive HED diagnostic due to its high sensitivity. For HED characterization the TL setup and imaging techniques must be changed from the recently studied medical system. The object magnification must be increased greatly in order to resolve μm scale gradients while the Talbot magnification must be increased in order to keep the gratings away from the plasma. Additionally, techniques for retrieving the density profile from a single plasma image must be developed. We thus study the performance of high magnification TL interferometers, in conjunction with Moire fringe deflectometry for single image phase retrieval. The results show a very good interferometer contrast (≤30%) at high magnification. The Moire technique enables measuring both sharp and mild density gradients with good accuracy and spatial resolution. Both the laboratory and simulation studies indicate that the TL based Moire deflectometry is more sensitive than the propagation phase-contrast method when utilizing an extended x-ray source (∼80 μm). In HED experiments this would allow for less demanding X-ray backlighters than those used at present.

We report on experiments examining the dynamics of low current (25 kA), long rise-time (400 ns) X-pinches. The experiments used two- and four-wire 5 μm tungsten X-pinches. We discuss coronal plasma dynamics, X-ray emission, cross-point evolution, and axial column dynamics. We show that the pinch dynamics are akin to those in X-pinches driven by 0.1–1 MA and at rise-rates from 0.25 to 10 kA/ns. We observe soft X-rays (∼1–2 keV range) emitted from the cross point in both two-wire and four-wire X-pinches at about peak current. These results show that compact current generators consisting of 2–4 small capacitors in a simple capacitive discharge circuit can produce good quality pinches for applications in Thomson X-ray scattering and backlighting among others.

We present observations of the emission characteristics of the plasma processes of a low inductance, sub Joule, compact capillary discharge, when operated in nitrogen at up to 600 Hz. A quarter period of under 10 ns is achieved allowing currents of order 5 kA. Four geometries are explored: two lengths, 21 and 36 mm, and two internal diameters, 1.6 and 3.2 mm. Transient hollow cathode fast electrons are associated with enhanced soft x-ray emission at shorter wavelengths with measured output energies of N VI at 28.8 A as compared with a Maxwellian plasma. Time-integrated spectroscopy together with filtered diode signals, and with spatial resolution, reveals a small axial emitting plasma close to the anode. Optical time-resolved spectroscopy gives larger scale plasma parameters both of the anode and the cathode plasmas. This volume plasma covers the range 2–8 eV, while the x-ray emitting plasma covers 10–20 eV, according to geometry. Nitrogen metastable emission is also observed in the hollow cathode volume prior to breakdown. Both internal wall diameter and capillary length affect both the spectrum and the x-ray emitting volume as does the axial pressure gradient. Electron beams from the transient hollow cathode are associated in model spectra with the observed N VI, O VI and Al VII–X ionization stages. Operating conditions that affect the spectral purity and discharge characteristics include the internal pressure gradient and nitrogen to helium mix ratio. We discuss the suitability of the capillary geometries as a soft x-ray source and in the context of available computer models.