Neutron diagnostics in Fast Ignition experiments with GEKKO-XII and LFEX lasers

The fast ignition integrated experiment was conducted on GEKKO-XII laser facility by using LFEX laser with the energy up to 1.4 kJ in a 1.2 ps pulse in 2010. Neutron yield enhancement was observed by a developed liquid scintillation detector [1]. DD fusion neutron signal was correctly separated from intense background signals originated from 1) $\gamma $ rays from the targets and scattered by experimental bay wall, and 2) neutrons by ($\gamma $-n) reaction in the target vacuum chamber or diagnostics instruments. The DD fusion neutron yield up to (3.5$\pm $1.3)$\times $10$^{7}$ was obtained with 300J of the additional heating laser energy, whereas 1$\times $10$^{6}$ was obtained in without heating case. The neutron yield was higher than that reported in the previous work [2]. \\[4pt] [1] T. Nagai, et. al., Japanese Journals of Applied Physics, (to be published) \\[0pt] [2] R. Kodama, et. al., Nature, \textbf{418}, 933-934 (2002)