High efficiency radiation accumulator for powerful lasers with low beam quality

Experimental studies of the concept of an efficient radiation trap based on the adiabatic photon confinement between curved mirrors is presented in the paper. Such a trap is free from restrictions typical to the Fabry-Perot cells, relating to the confined radiation quality, accuracy and stabilization of optical elements. Experiments have demonstrated the high efficiency of confinement, which mainly depends on the reflectivity of mirrors and their surface defects.