http://www.prism-cs.com/Software/Spect3D/SPECT3D_RPHDMpaper_2007.pdf

SPECT3D - A Multi-Dimensional Collisional-Radiative Code for Generating Diagnostic Signatures Based on Hydrodynamics and PIC Simulation Output

Reaching ignition in direct-drive (DD) inertial confinement fusion implosions requires achieving central pressures in excess of 100 Gbar. The OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] is used to study the physics of implosions that are hydrodynamically equivalent to the ignition designs on the National Ignition Facility (NIF) [J. A. Paisner et al., Laser Focus World 30, 75 (1994)]. It is shown that the highest hot-spot pressures (up to 40 Gbar) are achieved in target designs with a fuel adiabat of α ≃ 4, an implosion velocity of 3.8 × 107 cm/s, and a laser intensity of ∼1015 W/cm2. These moderate-adiabat implosions are well understood using two-dimensional hydrocode simulations. The performance of lower-adiabat implosions is significantly degraded relative to code predictions, a common feature between DD implosions on OMEGA and indirect-drive cryogenic implosions on the NIF. Simplified theoretical models are developed to gain physical understanding of the implosion dynamics that dictate the target performance. These models indicate that degradations in the shell density and integrity (caused by hydrodynamic instabilities during the target acceleration) coupled with hydrodynamics at stagnation are the main failure mechanisms in low-adiabat designs. To demonstrate ignition hydrodynamic equivalence in cryogenic implosions on OMEGA, the target-design robustness to hydrodynamic instability growth must be improved by reducing laser-coupling losses caused by cross beam energy transfer.

Improving the hot-spot pressure and demonstrating ignition hydrodynamic equivalence in cryogenic deuterium–tritium implosions on OMEGAa)

Three recent developments in direct-drive target design have enhanced the possibility of achieving high target gain on the National Ignition Facility (NIF): (1) Laser absorption was increased by almost 50% using wetted-foam targets. (2) Adiabat shaping significantly increased the hydrodynamic stability of the target during the acceleration phase of the implosion without sacrificing target gain. (3) Techniques to reduce laser imprint using pulse shaping and radiation preheat were developed. These design features can be employed for direct-drive-ignition experiments while the NIF is in the x-ray-drive configuration. This involves repointing some of the beams toward the equator of the target to improve uniformity of target drive. This approach, known as polar direct drive (PDD), will enhance the capability of the NIF to explore ignition conditions. PDD will couple more energy to the fuel than x-ray drive. The compressed fuel core can be more easily accessed for high-ρR diagnostic development and for fast-ign...

/pdf/polar-direct-drive-on-the-national-ignition-facility-2s5ptml1n7.pdf

Polar Direct Drive on the National Ignition Facility

Direct-drive-implosion experiments on the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have showed discrepancies between simulations of the scattered (non-absorbed) light levels and measured ones that indicate the presence of a mechanism that reduces laser coupling efficiency by 10%-20%. This appears to be due to crossed-beam energy transfer (CBET) that involves electromagnetic-seeded, low-gain stimulated Brillouin scattering. CBET scatters energy from the central portion of the incoming light beam to outgoing light, reducing the laser absorption and hydrodynamic efficiency of implosions. One-dimensional hydrodynamic simulations including CBET show good agreement with all observables in implosion experiments on OMEGA. Three strategies to mitigate CBET and improve laser coupling are considered: the use of narrow beams, multicolor lasers, and higher-Z ablators. Experiments on OMEGA using narrow beams have demonstrated improvements in implosion performance.

/pdf/crossed-beam-energy-transfer-in-direct-drive-implosionsa-12o94a89al.pdf

Crossed-beam energy transfer in direct-drive implosionsa)

Theoretical opacities are required for calculating energy transport in plasmas. In particular, understanding stellar interiors, inertial fusion, and Z pinches depends on the opacities of mid-atomic-number elements over a wide range of temperatures. The 150–300 eV temperature range is particularly interesting. The opacity models are complex and experimental validation is crucial. For example, solar models presently disagree with helioseismology and one possible explanation is inadequate theoretical opacities. Testing these opacities requires well-characterized plasmas at temperatures high enough to produce the ion charge states that exist in the sun. Typical opacity experiments heat a sample using x rays and measure the spectrally resolved transmission with a backlight. The difficulty grows as the temperature increases because the heating x-ray source must supply more energy and the backlight must be bright enough to overwhelm the plasma self-emission. These problems can be overcome with the new generation...

Experimental investigation of opacity models for stellar interior, inertial fusion, and high energy density plasmas

Simulation of X-ray scattering diagnostics in multi-dimensional plasma

Extreme ultraviolet lithography (EUVL) is a leading candidate for use in next-g eneration high volume manufacturing of semiconductor chips that require feature sizes less than 32 nm. The essential requirement for enabling this technology is to have a reliable, clean and powerful EUV source which efficiently emits light at a wavelength of 13 .5 nm. Laser-produced plasma EUV sources are strong candidates for use in EUVL light source systems. The development and optimization of high-efficiency EUV sources requires not only well-diagnosed experiments, but also a good understanding of the physical processes affecting the emitting plasma, which can be achieved with the help of accurate numerical simulation tools. Here, we investigate the radia tive properties of tin and tin-doped foam plasmas heated by 1.06 µm laser beams with 10 ns pulse widths. Results from simulations are compared with experimental conversion efficiencies and emission spectra. Keywords: Atomic physics, radiation-hydrodynamics, EUV lithog raphy, atomic spectroscopy, laser-produced plasmas, spectral analysis, radiation transport.

https://engineering.purdue.edu/CMUXE/Publications/Harilal/2008-SPIE-Hari.pdf

Modeling of EUV Emission and Conversion Efficiency from Laser-Produced Tin Plasmas for Nanolithography

Tin-based laser-produced plasmas are attractive candidates as extreme ultraviolet light (EUV) sources for
lithography. The accurate simulation of the dynamics and spectral properties of plasmas used in radiation source
experiments plays a crucial role in analyzing and interpreting experimental measurements, and in optimizing the 13.5
nm radiation from the plasma source. We use HELIOS-CR, a 1-D radiation-magnetohydrodynamics code, along with a
detailed and comprehensive atomic database for tin, to simulate the properties and EUV emission from a plasma
produced by the interaction of 1.06 μm laser light and a tin-doped water droplet. Simulated spectra are shown to be in
good agreement with experimental results at a variety of laser intensities. Simulation results are also presented to
examine the ionization distribution for tin at the simulated temperatures and densities.

Simulation of EUV spectral emission from laser-produced tin-doped water plasmas

http://absimage.aps.org/image/DPP05/MWS_DPP05-2005-000801.pdf

P. R. Woodruff

Papers

SPECT3D - A Multi-Dimensional Collisional-Radiative Code for Generating Diagnostic Signatures Based on Hydrodynamics and PIC Simulation Output

Simulation of X-ray scattering diagnostics in multi-dimensional plasma

Modeling of EUV Emission and Conversion Efficiency from Laser-Produced Tin Plasmas for Nanolithography

Simulation of EUV spectral emission from laser-produced tin-doped water plasmas

Modeling of Dopant Spectral Emission in Z-Pinch Dynamic Hohlraum Experiments