Observation of implosion dynamics by line emissions from direct-drive fusion capsules

Line emissions from Ar-doped fusion capsules were observed to investigate i nfluence of drive uniformity on implosion behavior. To manipulate the drive non-uniformity, in particular of the mode number 6, the laser focus positi on was set in two representative cases. A fusion capsule was directly irrad iated with 12 beams of partially-coherent green light. Imploded core plasma s were diagnosed by observing spatial distribution and time history of the Ar line emissions. Clear differences were obtained between the two irradiat ion cases despite the calculated irradiation uniformities for the two cases being identical. The experimental result was compared with two-dimensional fluid simulations post-processed with an X-ray spectrum analysis code. Dri ve uniformity and associated perturbation growth at the pusher-fuel boundar y are discussed as a plausible reason for the observed differences. (C) 199 9 Elsevier Science S.A. All rights reserved.