Indirect drive implosion in the compressive regime with elliptical and cylindrical-shaped gas-filled hohlraums on the Laser MegaJoule (LMJ) facility.

On the way to its complete configuration, the LMJ facility currently has the capability of delivering up to 270 kJ of UV energy on target with 80 beams (20 quads) in a symmetrical indirect drive irradiation scheme using a subset of its 30 available quadruplets.

As a follow on of our ICF program, we have recently performed indirect drive D2 filled plastic capsule implosions in the ablative compression regime in elliptical (rugby) and cylindrical-shaped warm low gas-filled holhraums. This series of experiments has been carried out for increasing ablator thicknesses to go towards more convergent implosions up to a convergence ratio greater than 15.

The laser cone fraction and beam pointing were successfully adjusted so as to tune the implosion symmetry while keeping a low level of backscattering.

The laser energy coupling to the capsule and implosion performances were mainly characterized with measurements of the time-resolved back and side-scattering, the radiative temperature, the laser beams energy deposition at the hohlraum thin-wall, and the hot spot x-ray emission. The novelty this year mainly lies in the two-dimensionnal X-Ray radiography platform developped for the measurement of the in-flight dynamics of imploding capsules taking advantage of an additional pair of quads dedicated to radiography sources on LMJ. A suite of ablator performance parameters, such as radius, velocity, and low-mode shape have been determined throughout the implosion history.

We will report on this complete set of experimental results for the whole range of explored parameters.