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A very large area (7.5 mm²) laser-driven x-ray backlighter, termed the Big Area BackLighter (BABL) has been developed for the National Ignition Facility (NIF) to support high energy density experiments. The BABL provides an alternative to Pinhole-Apertured point-projection Backlighting (PABL) for a large field of view. This bypasses the challenges for PABL in the equatorial plane of the NIF target chamber where space is limited because of the unconverted laser light that threatens the diagnostic aperture, the backlighter foil, and the pinhole substrate. A transmission experiment using 132 kJ of NIF laser energy at a maximum intensity of 8.52 x 1014 W/cm² illuminating the BABL demonstrated good conversion efficiency of >3.5% into K-shell emission producing ~4.6 kJ of high energy x rays, while yielding high contrast images with a highly uniform background that agree well with 2D simulated spectra and spatial profiles. [ABSTRACT FROM AUTHOR]

We present the calculations and preliminary results from experiments on the Omega laser facility using d-3He filled plastic capsule implosions in gold Hohlraums. These experiments aim to develop a technique to measure shell ρr and capsule unablated mass with proton spectroscopy and will be applied to future National Ignition Facility (NIF) experiments with ignition scale capsules. The Omega Hohlraums are 1900 μm length×1200 μm diameter and have a 70% laser entrance hole. This is approximately a 0.2 NIF scale ignition Hohlraum and reaches temperatures of 265–275 eV similar to those during the peak of the NIF drive. These capsules can be used as a diagnostic of shell ρr, since the d-3He gas fill produces 14.7 MeV protons in the implosion, which escape through the shell and produce a proton spectrum that depends on the integrated ρr of the remaining shell mass. The neutron yield, proton yield, and spectra change with capsule shell thickness as the unablated mass or remaining capsule ρr changes. Proton stopping models are used to infer shell unablated mass and shell ρr from the proton spectra measured with different filter thicknesses. The experiment is well modeled with respect to Hohlraum energetics, neutron yields, and x-ray imploded core image size, but there are discrepancies between the observed and simulated proton spectra. [ABSTRACT FROM AUTHOR]

Filtered x-ray diodes, sensitive in different spectral regions, are used to measure the emission spectrum of laser-driven hohlraums at the Omega laser facility in Rochester, NY. Here we present two new methods to reconstruct the emission spectra from the response of the x-ray diodes and compare them to the method currently used to extract a spectrum and a temperature in the hohlraum. We also use simulated spectra to characterize the different methods with respect to uncertainty, emission temperature, and the ability to reconstruct the input spectrum as closely as possible. [ABSTRACT FROM AUTHOR]

Some applications of gated x-ray imagers, pulsed x-ray spectroscopy, for example, benefit if image capture is simultaneous and gain is uniform over the frame. Simultaneity and uniformity are both improved when the voltage gate pulse propagation distance is as short as practical across the micro-channel-plate. This article describes a micro-channel-plate intensifier that captures a 40×100 mm2 image in <300 ps. A simple transmission line loss model is proposed to explain voltage loss across the micro-channel-plate. The voltage loss exponent was measured to be 0.05/cm±20%, and used to predict spatial and temporal gain dependence. The spatial and temporal gain profile was measured in detail by capturing images of ∼1 ps x-ray bursts created with a short pulse laser. The measured profile is consistent with that predicted using the loss model. [ABSTRACT FROM AUTHOR]

A high contrast 12.6 keV Kr Kα source has been demonstrated on the petawatt-class Titan laser facility using strongly clustering Kr gas jet targets. The contrast ratio (Kα to continuum) is 65, with a competitive ultrashort pulse laser to x-ray conversion efficiency of 10-5. Filtered shadowgraphy indicates that the Kr Kα and Kβ x rays are emitted from a roughly 1×2 mm2 emission volume, making this source suitable for area backlighting and scattering. Spectral calculations indicate a typical bulk electron temperature of 50–70 eV (i.e., mean ionization state 13–16), based on the observed ratio of Kα to Kβ. Kr gas jets provide a debris-free high energy Kα source for time-resolved diagnosis of dense matter. [ABSTRACT FROM AUTHOR]

A diagnostic currently being used for ultrashort pulse laser matter interactions at the Lawrence Livemore National Laboratory is presented. Two cylindrical curved crystals are used as collection optics and diffractive elements in the von Hámos geometry. The dispersed x rays are focused onto the slit of an ultrafast x-ray streak camera. The small nature of the streak camera allows the diagnostic to be positioned close to the target, maximizing the solid angle. Using the geometric layout, the spectral resolution is estimated at E/ΔE∼1000. [ABSTRACT FROM AUTHOR]