Experimental investigation of the interaction of 100 TW laser with solid targets (abstract)

Abstract

We report on the first plasma experiments with the 100 TW laser at LLNL. We have experimentally investigated the interaction of 1 μm, 40 J, 400 fs, 5×1019 W/cm2 laser pulses with multilayer solid targets. Various diagnostics were used to characterize this interaction. An x-ray pinhole camera monitored laser spot size and plasma location on target. Part of the laser beam was split off to probe the density scale length of the preformed plasma. An optical system for Schlieren photography was designed to record the images of plasma with electron density gradients as low as 1021 cm−4 with characteristic scale length of 10 μm. The range of electron densities was 1018–2020 cm−3. CR-39 plastic track detectors were employed to measure the fast ion blowoff from the plasma. Using a foil-filter technique the proton energy spectrum up to 6 MeV was measured. It was found that the high energy tail usually had a narrow (FWHM ∼10°) cone of expansion. Energy conversion to the fast ions (above 0.5 MeV) was estimated to be ∼0.3%–1% of laser energy. In addition, charge-coupled devices were used for detecting characteristic K α emission caused by fast (>1 MeV) electrons. (See article by K. Wharton for further discussion of the fast electron measurements.) Estimated fast electron yield ∼3%.