Experimental study of various shaped-hohlraums in low gas-filled hohlraums indirect drive implosion on the Laser MegaJoule (LMJ) facility

On the way to its complete configuration, the LMJ facility has currently the capability of delivering up to 270 kJ of UV energy on target with 80 beams (20 quads) in a symmetrical irradiation scheme. Over the past few years, we have performed warm low-filled holhraums indirect drive D2 plastic capsule implosions in a ablative compression regime with rugby, elliptical and cylindrical-shaped hohlraums. The goal was to find out the hohlraum shape which presents the best laser coupling optimization and the best symmetric capsule implosion. In this context, various laser pulse shapes have been tested. With this series of experiments, we were able to validate different ways to reduce backscatter energy level which was higher for rugby shaped-hohlraums compared to other hohlraums shapes. We also could optimize capsule irradiation symmetry which was more challenging for cylindrical-shaped hohlraum. Experimental results will be compared with radiation-hydrodynamics code TROLL simulations.