A technique to study Rayleigh–Taylor instability by α-particle backlighting

Abstract

A novel α-particle backlighting technique has been developed to diagnose laser plasmas, enabling small changes in the thickness modulation to be measured, down to ~0.1 μm. In this technique, a laser-driven implosion of a D–T target produces a bright pulse of α-particles that is used to shadow a separately driven foil. Each α-particle loses range in the foil, and each such measurement forms an individual local determination of the foil thickness at the time of passage of the particles. A shadow image of the driven foil can also be produced, of spatial resolution limited by source size and multiple Coulomb scattering in the driven plasma. The technique is illustrated here with a preliminary study of fluid instabilities in laser-accelerated planar foils. Foils were accelerated using both unsmoothed and smoothed laser drive beams. Foils driven by beams smoothed by random-phase plates showed a much reduced modulation.