Supersonic heat wave propagation in laser-produced underdense plasma for efficient x-ray generation

Tanabe, Minoru; Nishimura, Hiroaki; Fujioka, Shinsuke; Nagai, Kotobu; Iwamae, Atsushi; Ohnishi, Naofumi; Fournier, K. B.; Girard, Frédéric; Primout, M.; Villette, B.; Tobin, M.; Mima, K.

doi:10.1088/1742-6596/112/2/022076

Cited by 7 publications

(6 citation statements)

References 8 publications

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“…The CEs from these hohlraums are compared to those obtained with thick foils, 3,5,7,8 thin pre-exploded foils, 19-21 gas targets, 11,12 aerogels, 13,14 and nanofiber-cotton targets. 35,36 Figure 17 is a summary of published CEs for nanosecond laser-produced plasmas and a large variety of target materials. As titanium emitters at 4.7 keV, lined hohlraums are the most efficient solid targets and these data are close to gas targets, which are considered as an upper limit for x-ray yields since their low density allows good laser absorption and small kinetic losses.…”

Section: Discussionmentioning

confidence: 99%

Titanium and germanium lined hohlraums and halfraums as multi-keV x-ray radiators

et al. 2009

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As multi-keV x-ray radiators, hohlraums and halfraums with inner walls coated with metallic materials (called liner) have been tested for the first time with laser as the energy drive. For titanium, conversion efficiencies (CEs) are up to ∼14% for emission into 4π, integrating between 4.6 and 6.5 keV when a large diameter hohlraum is used. Germanium CE is ∼0.8% into 4π between 9 and 13 keV. The highest CEs have been obtained with a 1 ns squared pulse and phase plates giving laser absorption near 99%. These high CEs are due to long-lasting, good plasma conditions for multi-keV x-ray production maintained by plasma confinement inside the plastic cylinder and plasma collision leading to a burst of x rays at a time that depends on target size. As photon emitters at 4.7 keV, titanium-lined hohlraums are the most efficient solid targets and data are close to CEs for gas targets, which are considered as the upper limit for x-ray yields since their low density allows good laser absorption and low kinetics losses. As 10.3 keV x-ray emitters, exploded germanium foils give best results one order of magnitude more efficient than thick targets; doped aerogels and lined hohlraums give similar yields, about three times lower than those from exploded foils.

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Section: Discussionmentioning

confidence: 99%

Titanium and germanium lined hohlraums and halfraums as multi-keV x-ray radiators

et al. 2009

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“…At sub-critical densities, the ionization wave and heating wave travel faster than the plasma sonic velocity [3]. Thus, the laser beam supersonically and volumetrically heats the low-density material on a time scale shorter than the time scale for the rarefaction wave to decompress and cool the plasma, providing much higher x-ray conversion efficiency (XRCE) in the non-LTE plasma than is obtained by simply irradiating solid targets [4,5,6]. Under-dense high-Z radiators have been confined in the past mainly to high-Z noble gases (Ar, Kr, and Xe) [7,8,9], but some efficient Ti x-ray sources (K-shell emission ~ 4 keV) have also been created with nano-fiber targets [10]; with pre-pulsed Ti, Cu, and Ge foils (K-shell emission ~ 4 keV, ~8 keV, and ~10 keV respectively) [11,12]; and by irradiating the inside surface of Ti-and Ge-lined cans [13,14].…”

Section: Introductionmentioning

confidence: 99%

A computational study of x-ray emission from high-Z x-ray sources on the National Ignition Facility laser

Colvin

Fournier

Kane

et al. 2011

High Energy Density Physics

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We have begun to use 350-500 kJ of 1/3-micron laser light from the National Ignition Facility (NIF) laser to create millimeter-scale, bright multi-keV x-ray sources. In the first set of shots we achieved 15% -18% x-ray conversion efficiency into Xe M-shell (~1.5-2.5 keV), Ar K-shell (~3 keV) and Xe L-shell (~4-5.5 keV) emission (Fournier et al., Phys. Plasmas 17, 082701, 2010), in good agreement with the emission modeled using a 2D radiation-hydrodynamics code incorporating a modern Detailed Configuration Accounting atomic model in non-LTE (Colvin et al., Phys. Plasmas, 17, 073111, 2010). In this paper we first briefly review details of the computational model and comparisons of the simulations with the Ar/Xe NIF data. We then discuss a computational study showing sensitivity of the x-ray emission to various beam illumination details (beam configuration, pointing, peak power, pulse shape, etc.) and target parameters (size, initial density, etc.), and finally make some predictions of how the x-ray conversion efficiency expected from NIF shots scales with atomic number of the emitting plasma.

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“…In the work in Refs. [44][45][46] the targets were all solid at room temperature, unlike the gaseous targets of the present work. The targets were all doped SiO 2 aerogels in the few mg/cm 3 density range.…”

Section: A Supersonic Energy Depositionmentioning

confidence: 96%

Multi-keV x-ray source development experiments on the National Ignition Facility

et al. 2010

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We report results from a five shot campaign carried out with Ar-Xe gas-filled targets at the National Ignition Facility (NIF). The targets were shot with ≈ 350 kJ of 3ω laser energy delivered with a 5 ns trapezoidal laser pulse. We report measured x-ray output from the target in different spectral bands both below and above 1.5 keV photon energies: we find yields of ≈20.5 kJ/sr with peak x-ray power approaching 4 TW/sr over all energies, as measured for the unique viewing angle of our detector, and ≈3.6 kJ/sr with peak x-ray power of 1 TW/sr for x rays with energies >3 keV. This is a laser-to-x-ray conversion efficiency of 13±1.3 % for isotropic x rays with energies >3 keV. Laser energy reflected by the target plasma for both inner and outer-cone beams is measured and found to be small, between 1-4% of the drive energy. The energy emitted in hard x rays (with energies >25 keV) is measured and found to be ≈1 J/sr. Two-dimensional imaging of the target plasma during the laser pulse confirms a fast, volumetric heating of the entire target, resulting in efficient laser-to-x-ray conversion. Post-shot simulations with a two-dimensional radiation-hydrodynamics code reproduce well the observed x-ray flux and fluence, backscattered light, and bulk target motion.

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Supersonic heat wave propagation in laser-produced underdense plasma for efficient x-ray generation

Cited by 7 publications

References 8 publications

Titanium and germanium lined hohlraums and halfraums as multi-keV x-ray radiators

Titanium and germanium lined hohlraums and halfraums as multi-keV x-ray radiators

A computational study of x-ray emission from high-Z x-ray sources on the National Ignition Facility laser

Multi-keV x-ray source development experiments on the National Ignition Facility

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