Prospects for achieving high dynamic compression with low energy

Abstract

Laser driven dynamic compression experiments may, in materials with picosecond equilibration times, be possible with orders of magnitude less drive energy than currently used. As we show, the compression energy for geometrically similar experiments varies as the third power of the time scale of compression. For materials which equilibrate and can be characterized on picosecond time scales, the compression energy can be orders of magnitude smaller than the 1–100 ns scale time scale of many current experiments. The use of substantially lower compression energy is a great practical advantage in such experiments, potentially enabling the observation of extreme states of matter with table top scale laser systems.

Ultrafast Laser Diagnostics for Energetic-Material Ignition Mechanisms: Tools for Physics-Based Model Development.

“…The 500-J critical drive pulse energy identified here is significantly larger than observed in previous picosecond laser-drive experiments [2][3][4][5][6][7][8][9][10][11][12], where drive energies of only 50-100 J were sufficient to achieve plastic shock breakout in bare aluminum layers. At this time, we believe the reason for this is the stretcher design employed, which lacks a Fourier plane where the spectral elements are in focus.…”

“…6 [2], where the deformation of the laser-driven ablator forms a "piston interface" behind an expanding shock front. For the conditions of a "typical" UTDI experiment described here, Armstrong [4] has shown that the radius of curvature of the shock front is large compared to the sample thickness, so that 1-D shock conditions exist locally within the film. We note that our experiment measures the piston speed, not the particle speed just behind shock front, but it has been shown in previous work [6] that, by assuming the particle speed is the same as the measured piston speed, the measured shockwave speed will correspond to the known Hugoniot to better than 2% accuracy [6,11].…”

“…A fast time-domain rise is added to the pulse by clipping the dispersed spectrum within the compressor. Previous work [2][3][4][5][6][7][8][9][10] using an external stretcher, produced 10-to 20-ps rise shock waves in aluminum films. In the "overcompressed" pulse-shaper design used here, lack of a true Fourier plane in our external compressor may result in a more gradual rise to the clipped spectrum and time-domain pulse.…”

Observation of Fundamental Mechanisms in Compression-Induced Phase Transformations Using Ultrafast X-ray Diffraction

“…Such experiments have been used to observe a wide range of anomalous behavior under ultrafast compression, including extreme elastic deformation [19,21,22] (related to a lack of plastic deformation on this time scale [21,[23][24][25]), simultaneous phase transformation and plasticity [26], with high throughput. [27] * While these experiments have provided information about the bulk With the advent of femtosecond time resolution x-ray diffraction at the Linac Coherent Light Source (LCLS), it has now become feasible to explore the transient states of materials under extremely rapid compression with nm/ps resolution. [24,[28][29][30][31] By combining the 100 ps laser drive available at the MEC beamline of LCLS with the 100 fs x-ray capability, we can begin to address some the of fundamental questions concerning phase transformations: Are intermediate states ordered or disordered at the atomic scale?…”

Extreme dynamic compression with a low energy laser pulse

“…In particular, if a compression time of 1 ns is required to obtain a given final state, 1000x more energy than necessary would be required to compress to the same state over 10 ns. Typically, ~Mbar pressures can be obtained with <mJ pulse energy applied over some hundreds of picoseconds [1][2][3][4][5][6][7] . This pulse energy is readily available from common commercial chirped pulse amplification systems operating well into kHz repetition rates.…”