Study of target heating induced by fast electrons in mass limited targets

We studied the induced plasma heating in three different kind of targets: mass limited, foam targets and large mass targets. The experiment was performed at Alisé laser facility of CEA/CESTA. The laser system emitted a ∼1-ps pulse with ∼10J energy at a wavelength of ∼1 μm. Mass limited targets had three layers with thickness 10 μm C₈H ₈, 1 μm C₈H₇Cl, 10 um C₈H ₈ with size 100 μm × 100 μm. Detailed spectroscopic analysis of X-rays emitted from the Cl tracer showed that it was possible to heat up the plasma mass limited targets to a temperature ∼250 eV with density ∼ 10²¹ cm^-3. The plasma heating is only produced by fast electron transport in the target, being the 10 μm C ₈H₈ overcoating thick enough to prevent any possible direct irradiation of the tracer layer even taking into account mass-ablation due to the pre-pulse. These results demonstrate that with mass limited targets 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).