Experimental study of laser beam transmission and power accounting in a large scale length laser plasma

It is shown that the measured laser power transmission through a large scal e length, high temperature plasma (which emulates an indirect drive ignitio n-scale plasma) is in approximate agreement with the simulated transmission provided the simulations account for the power loss due to scattering from laser-plasma instabilities. Detailed accounting of the incident, transmitt ed, scattered, and absorbed powers is used to infer the likely location in the target where most of the scattering occurs along the incident beam traj ectory. This location is near the incident laser side of the target at peak electron temperatures for a range of laser intensities. As a result, the b ackscattered light measurements at peak electron temperature do not require significant adjustment to account for attenuation of the backscattered lig ht as it propagates out through the plasma. (C) 2000 American Institute of Physics. [S1070-664X(00)01507-X].