Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session V2: Experimental Developments IX: Ultrafast Compression |
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Chair: Norimasa Ozaki, Osaka University, Nicholas Glumac, University of Illinois at Urbana-Champaign Room: Grand F |
Thursday, June 18, 2015 3:45PM - 4:15PM |
V2.00001: Ultrafast compression: past, present, and future Invited Speaker: Michael Armstrong In the nearly 20 years since the first sub-ps time resolution compression wave measurements, ultrafast compression experiments have progressed from simple demonstrations to robust discoveries of extreme phenomena spanning material plasticity, solid-solid phase transitions, and shock induced chemistry. At strain rates above 10$^{9}$ s$^{-1}$, many usual assumptions about material response no longer apply -- virtually every system investigated on sub-ns time scales exhibits phenomena which are unfamiliar to conventional intuition about compression waves. This diverse of range of phenomena reflects the fundamental complexity of dynamic material behavior, but it has also been a significant impediment to a full understanding of material compression. Nonetheless, ultrafast experiments afford a number of practical advantages, primarily related to scale. Using an inexpensive table-top laser, it is possible to obtain information on materials at extreme conditions with a low laser pulse energy and a high data rate. In this talk, I will briefly review the history of ultrafast compression, significant results, and future opportunities. [Preview Abstract] |
Thursday, June 18, 2015 4:15PM - 4:30PM |
V2.00002: Extreme dynamic compression with a low energy laser pulse Michael Armstrong, Jonathan Crowhurst, Joseph Zaug, Harry Radousky Recently, it was shown that the energy required for laser driven dynamic compression experiments varies as the third power of the compression time, where the compression time must be larger than the equilibration time in the sample. Traditional dynamic compression experiments typically have drive times greater than 10 ns, but a wide range of materials equilibrate on substantially faster time scales, which should enable such materials to be compressed on much shorter time scales. So, for materials which equilibrate on a sub-nanosecond time scale, ultrafast dynamic compression has the potential to substantially reduce the laser energy required to obtain highly compressed states of matter. This has been demonstrated for sub-Mbar pressures with \textless 100 $\mu $J energy laser drive pulses, where the laser drive energy per unit density change is as much as 10$^{9}$ smaller than longer time scale experiments. Although these results are promising, extreme pressures (up to 10 Mbar) have not yet been observed with table-top scale laser systems. Here we present results for ultrafast laser driven shock experiments using up to 500x more drive intensity than our previous work, which, by conventional scaling, should result in dynamic pressures previously only accessible to facility scale instruments. [Preview Abstract] |
Thursday, June 18, 2015 4:30PM - 4:45PM |
V2.00003: Monitoring heat energy transfer in condensed phases using ultrafast transient spectroscopies Nhan Dang, Jennifer Gottfried The primary motivation for this work is the desire to observe the initial evolution of temperature transfer into a solid explosive on the picosecond timescale following indirect ultrafast flash heating, which may provide insight the role of temperature in the shock-induced initiation mechanism in explosives. In this presentation, we describe the methods of indirect flash heating on glass-gold-sample substrates using femtosecond laser pulses; and the methods of monitoring the sample response under the influence of the heat transferred from the heated gold layer through the sample using time-resolved visible transient absorption (TA) spectroscopy and coherent Raman spectroscopies. Data presented here are the evolution of heat energy transfer in a drop-cast thin film of unreacted cyclotrimethylene trinitramine (RDX) monitored using visible TA and surface-enhanced coherent anti-Stokes Raman spectroscopy. The method of nonequilibrium temperature measurement using femtosecond-stimulated Raman spectroscopy reported in [Phys. Rev. Lett., 2011, 107, 043001; J. Raman Spectrosc., 2013; 44 (3) 433-439.] will be also discussed here for the application of monitoring and measuring temperature in real-time. [Preview Abstract] |
Thursday, June 18, 2015 4:45PM - 5:00PM |
V2.00004: Ultrafast phase contrast imaging of laser driven shocks using betatron X-rays D.J. Chapman, M.E. Rutherford, T.G. White, D.E. Eakins, J.C. Wood, K. Poder, N.C. Lopes, J.S.J. Bryant, S.P.D. Mangles, Z. Najmudin, J.S. Cole, F. Albert, B.B. Pollack, K.T. Behm, Z. Zhao, A.G.R. Thomas, K. Krushelnick, W. Schumaker, S. Glenzer Bright, high-energy photon sources, such as synchrotrons and more recently the new generation of X-ray free-electron lasers, offer the attractive combination of high brilliance, short pulse duration and high-energy X-rays. Betatron X-rays produced within a laser-plasma wakefield accelerator provide an exciting complementary energetic photon source to these large scale facilities. We describe the first proof-of-principle experiments imaging shock-front evolution in laser driven targets using wakefield betatron X-rays. These pioneering experiments were performed on the 400TW Gemini laser at the Rutherford Appleton Laboratory, UK. Shock waves were driven into silicon wafers along the [100] direction, and stroboscopically imaged perpendicular to the shock propagation direction using a $\approx40$ fs betatron X-ray pulse. These initial results showcase a promising, potentially table top sized X-ray source suitable for probing the response of materials under extreme condition. [Preview Abstract] |
Thursday, June 18, 2015 5:00PM - 5:15PM |
V2.00005: Study on the dynamic behavior of matters using laser-driven shock waves in the water confinement Hyeonju Yu, Jack J. Yoh The strain rates achievable in laser-driven shock experiments overlap with gas gun and can reach much higher values. The laser-based method also has advantages in terms of system size, cost, repeatability, and controllability. In this research, we aim to measure equation of state, Hugoniot elastic limit, strain rate, and compressive yield strength of target samples by making use of the velocity interferometer or the VISAR. High pressure shock wave is generated by a Q-switched Nd:YAG laser operating at 1.064 $\mu m$ wavelength with pulse energy up to 3 joules and 9 ns pulse duration. All the experiments are conducted in the water confinement to increase the peak stresses to an order of GPa. Furthermore, quantitative comparisons are made to the existing shock data in order to emphasize the novelty of the proposed setup which is relatively simple and reliable. [Preview Abstract] |
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