Study of plasma heating induced by fast electrons
Résumé
We studied the induced plasma heating in three different kinds of targets: mass limited, foam targets, and large mass targets. The experiment was performed at Ali? Laser Facility of CEA/CESTA. The laser system emitted a ?1 ps pulse with ?10 J energy at a wavelength of ?1 ?m. Mass limited targets had three layers with thicknesses of 10 ?m C8 H 8, 1 ?m C8 H7 Cl, and 10 ?m C8 H8 with size of 100×100 ? m2. Detailed spectroscopic analysis of x rays emitted from the Cl tracer showed that it was possible to heat up the plasma from mass limited targets to a temperature of ?250 eV with density of ? 1021 cm-3. The plasma heating is only produced by fast electron transport in the target, being the 10 ?m C8 H8 overcoating thick enough to prevent any possible direct irradiation of the tracer layer even taking into account mass-ablation due to the prepulse. These results demonstrate that with mass limited targets, it is possible to generate a plasma heated up to several hundreds eV. It is also very important for research concerning high energy density phenomena and for fast ignition (in particular for the study of fast electrons transport and induced heating). © 2009 American Institute of Physics.