Collection of solid and gaseous samples to diagnose inertial confinement fusion implosions.
Collection of representative samples of debris following inertial confinement fusion implosions in order to diagnose implosion conditions and efficacy is a challenging endeavor because of the unique conditions within the target chamber such as unconverted laser light, intense pulse of x-rays, physical chunks of debris, and other ablative effects. We present collection of gas samples following an implosion for the first time. High collection fractions for noble gases were achieved. We also present collection of solid debris samples on flat plate collectors. Geometrical collection efficiencies for Au hohlraum material were achieved and collection of capsule debris (Be and Cu) was also observed. Asymmetric debris distributions were observed for Au and Be samples. Collection of Be capsule debris was higher for solid collectors viewing the capsule through the laser entrance hole in the hohlraum than for solid collectors viewing the capsule around the waist of the hohlraum. Collection of Au hohlraum material showed the opposite pattern: more Au debris was collected around the waist than through the laser entrance hole. The solid debris collectors were not optimized for minimal Cu backgrounds, which limited the conclusions about the symmetry of the Cu debris. The quality of the data limited conclusions on chemical fractionation effects within the burning, expanding, and then cooling plasma.
Use of a radioactive tracer to determine the fraction of fusion target debris collected
In order to obtain the pusher attenuation length (ρΔR) of inertial confinement fusion targets by neutron activation, it is necessary to know what fraction of the target debris is counted. One method of measuring this quantity experimentally is by means of a radioactive tracer. We demonstrate the usefulness of this technique by experiments utilizing a 24Na tracer.
Direct Measurement of Compression of Laser-Imploded Targets Using X-Ray Spectroscopy
Compression of neon-filled glass microballoons irradiated by a four-beam laser system has been measured directly by Stark broadening, opacity broadening, and spatial profiles of ${\mathrm{Ne}}^{+9}$ x-ray lines. For an 8.6-atm fill pressure and a 0.2-TW, 40-psec laser pulse, the measured compressed neon density was 0.26 g/${\mathrm{cm}}^{3}$ and the product $\ensuremath{\rho}R$ was 2.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ ${\mathrm{g}/\mathrm{c}\mathrm{m}}^{2}$.