X-RAY-EMISSION BY THE REAR SIDE OF LASER-IRRADIATED GOLD TARGETS

We present results of X-ray emission by the rear side of gold thin targets irradiated by the Phebus laser at lambda = 0.35-mu-m, tau = 0.7 and 1.3 ns, and E(L) = 1.5 kJ. A streak camera coupled with a transmission grating gave the time-resolved X-ray emission of the rear side. Also, a streak camera coupled with a slit allowed us to obtain information about the space and time evolution of the plasma. Some other diagnostics gave information about the energy balance and the X-ray conversion efficiency. The results are in good agreement with previous ones obtained with the Octal laser, particularly on optimum thickness for X-ray conversion efficiencies. Values of the thermal flux limiter are deduced. Simulations with FCI 1 code with multigroup radiative transfer and non-LTE ionization reproduce the experimental results only about some points. A number of reasons, such as 2-D effects and problems of opacity, are invoked.