Spherical shock development near laser‐heated microshell targets

Spherical expansion of the luminous front around a laser‐heated microshell target in 20 Torr of helium is compared with theory in the mass‐dependent region. Microshell targets from 74‐ to 7970‐ng initial mass irradiated with up to 0.13 TW (Terawatt) of 1.06‐μm light were studied. Effects of the initial mass and changing γ on the front history are discussed. It is concluded that extraction of expansion energy from the front motion is not easily accomplished in this close‐in region.