Physics – Plasma Physics
Scientific paper
Nov 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aps..dpp4ifa04m&link_type=abstract
American Physical Society, Division of Plasma Physics Meeting, November 10-15, 1996, abstract #4IFA.04
Physics
Plasma Physics
Scientific paper
Inertial confinement fusion (ICF) aims at compressing hydrogen (DT) more than 1000 times; this requires low-entropy compression and may be achieved e.g. with laser pulses shaped in time. This talk discusses options to generate 1-100 Mbar, ρ/ρ0 = 1-100 matter at 1-10 eV temperature and much below, using the ICF expertise for basic research. Probes will have 1-10 μm sizes and 1-10 ns lifetime, long enough for equilibration and optical/x-ray diagnostics. A host of ionisation transitions and abundant transport structure is predicted for this region, so far unchecked by experiment. A brief survey will be given. Metallization of hydrogen is of fundamental importance in the astrophysics of planets and brown dwarfs. The conducting state, recently detected at 1.4 Mbar using gas guns (Weir, Mitchell, Nellis, PRL 76, 1860 (1996)), still refers to the molecular phase, while genuine atomic metallic hydrogen, predicted to appear at 3 Mbar and tenfold compression, still waits for laboratory detection. The (non)existence of plasma phase transitions predicted for dense fluids at some eV needs to be clarified. Pycnonuclear reactions may become detectable at ρ/ρ_0~= 100 (S. Ichimaru, J.Phys.Soc.Jpn 60, 1437 (1991)). Traditional high-pressure techniques (diamond anvils, shock compression using explosives or gas guns) reach inherent limits at a few Mbar, while 10-1000 Mbar shocks are reported from recent laser experiments. Essential progress has been made concerning drive uniformity and preheat suppression. The future challenge is in precision pulse shaping. Ten-fold compression of a plane liquid hydrogen layer with 0.1 eV final temperature requires a sequence of 11 shocks with precise time and intensity control. Reveberating shocks beween two impacting flyer plates may also generate the sequence. Corresponding simulations are presented. Relatively small lasers in the 1-10 kJ class may do the job, provided they meet the precision requirements.
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