First direct-drive implosions and produced neutrons for development of a particle source platform on the laser megajoule

A first series of direct-drive implosions was performed on LMJ by the end of 2019, producing for the first time DD fusion neutrons and yield. This experiment, consisting of two laser shots on glass (SiO2) gas-filled spherical capsules, was aimed at commissioning the time-of-flight neutron diagnostic. The experimental results are presented in detail and compared to 3D calculations. A non-dedicated beam geometry was employed due to the limited number of laser beams available at this time, creating very strong irradiation asymmetries. An exploding pusher implosion regime was chosen to guarantee a sufficient number of neutrons. Yields of approximately 51010 were achieved, allowing the diagnostic commissioning. Discrepancies between experimental results and 3D calculations are observed and probably originate from strong distortions of the shell during the implosion, limiting the experimental yield compared to the simulated one.