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Time-resolved X-ray spectroscopy of deeply buried tracer layers as a density and temperature diagnostic for the fast ignitor

Published online by Cambridge University Press:  16 October 2009

J. A. Koch
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
C. A. Back
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
C. Brown
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
K. Estabrook
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
B. A. Hammel
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
S. P. Hatchett
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
M. H. Key
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
J. D. Kilkenny
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
O. L. Landen
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
R. W. Lee
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
J. D. Moody
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
A. A. Offenberger
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
D. Pennington
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
M. D. Perry
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
M. Tabak
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
V. Yanovsky
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
R. J. Wallace
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
K. B. Wharton
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550
S. C. Wilks
Affiliation:
Lawrence Livermore National Laboratory, P.O. Box 808, L-473, Livermore CA 94550

Abstract

The fast ignitor concept for inertial confinement fusion relies on the generation of hot electrons, produced by a short-pulse ultrahigh intensity laser, which propagate through high-density plasma to deposit their energy in the compressed fuel core and heat it to ignition. In preliminary experiments designed to investigate deep heating of high-density matter, we used a 20 joule, 0.5–30 ps laser to heat solid targets, and used emission spectroscopy to measure plasma temperatures and densities achieved at large depths (2–20 microns) away from the initial target surface. The targets consisted of an Al tracer layer buried within a massive CH slab; H-like and He-like line emission was then used to diagnose plasma conditions. We observe spectra from tracer layers buried up to 20 microns deep, measure emission durations of up to 200 ps, measure plasma temperatures up to Te=650 eV, and measure electron densities above 1023 cm−3. Analysis is in progress, but the data are in reasonable agreement with heating simulations when space-charge induced inhibition is included in hot-electron transport, and this supports the conclusion that the deep heating is initiated by hot electrons.

Type
Regular Papers
Copyright
Copyright © Cambridge University Press 1998

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