Oxford Centre for High Energy Density Science (OxCHEDS)

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Electron–positron pair creation in burning thermonuclear plasmas

High Energy Density Physics Elsevier 9:3 (2013) 480-483

25aKC-4 超高速その場X線回折による鉄の超高圧相転移観察(非平衡極限プラズマ,領域2(プラズマ基礎?プラズマ科学?核融合プラズマ?プラズマ宇宙物理))

(2013) 177

Authors:

近藤 良彦, 尾崎 典雅, Alessandra Bennuzzi-Mounaix, Adrien Denound, Alessandra Ravasio, Erik Brambrink, Gianluca Gregori, Gael Huser, 浦西 宏幸, 宮西 宏併, 中塚 和樹, 喜田 美佳, Michel Koenig, 池谷 正太郎, 小川 剛, 佐野 孝好, Tommaso Vinci, Tsung-Han Yang, 坂和 洋一, 浅海 雄人, 佐藤 友哉, 兒玉 了介

Prediction of Debye-Scherrer diffraction patterns in arbitrarily strained samples

ArXiv 1308.4958 (2013)

Authors:

Andrew Higginbotham, David McGonegle

Abstract:

The prediction of Debye-Scherrer diffraction patterns from strained samples is typically conducted in the small strain limit. Although valid for small deviations from the hydrostat (such as the conditions of finite strength typically observed in diamond anvil cells) this assertion is likely to fail for the large strain anisotropies (often of order 10% in normal strain) such as those found in uniaixally loaded dynamic compression experiments. In this paper we derive a general form for the (θ_B, φ) dependence of the diffraction for an arbitrarily deformed sample in arbitrary geometry. We show that this formula is consistent with ray traced diffraction for highly strained computationally generated polycrystals, and that the formula shows deviations from the small strain solutions previously reported.

Measuring fast electron spectra and laser absorption in relativistic laser-solid interactions using differential bremsstrahlung photon detectors.

Rev Sci Instrum 84:8 (2013) 083505

Authors:

RHH Scott, EL Clark, F Pérez, MJV Streeter, JR Davies, H-P Schlenvoigt, JJ Santos, S Hulin, KL Lancaster, SD Baton, SJ Rose, PA Norreys

Abstract:

A photon detector suitable for the measurement of bremsstrahlung spectra generated in relativistically intense laser-solid interactions is described. The Monte Carlo techniques used to extract the fast electron spectrum and laser energy absorbed into forward-going fast electrons are detailed. A relativistically intense laser-solid experiment using frequency doubled laser light is used to demonstrate the effective operation of the detector. The experimental data were interpreted using the 3-spatial-dimension Monte Carlo code MCNPX [D. Pelowitz, MCNPX User's Manual Version 2.6.0, Los Alamos National Laboratory, 2008], and the fast electron temperature found to be 125 keV.

Ultrafast three-dimensional imaging of lattice dynamics in individual gold nanocrystals.

Science 341:6141 (2013) 56-59

Authors:

JN Clark, L Beitra, G Xiong, A Higginbotham, DM Fritz, HT Lemke, D Zhu, M Chollet, GJ Williams, M Messerschmidt, B Abbey, RJ Harder, AM Korsunsky, JS Wark, IK Robinson

Abstract:

Key insights into the behavior of materials can be gained by observing their structure as they undergo lattice distortion. Laser pulses on the femtosecond time scale can be used to induce disorder in a "pump-probe" experiment with the ensuing transients being probed stroboscopically with femtosecond pulses of visible light, x-rays, or electrons. Here we report three-dimensional imaging of the generation and subsequent evolution of coherent acoustic phonons on the picosecond time scale within a single gold nanocrystal by means of an x-ray free-electron laser, providing insights into the physics of this phenomenon. Our results allow comparison and confirmation of predictive models based on continuum elasticity theory and molecular dynamics simulations.