Exploration of the yield-ratio method at Shenguang II laser facility.

In inertial confinement fusion implosion experiments with the primary-neutron yield as low as 10⁷, the method of yield ratio is proposed to diagnose the areal density <ρR> at Shenguang II laser facility. Considering the detection efficiency and the time response, a new detector for detecting the secondary-neutron signal is developed, which locates 50 cm away from the target. According to Monte Carlo N-particle simulation, 5-cm-thick lead shield was placed in front of the detector to shield x rays. In the 2004 experiments, the highest primary-neutron yield is 3.18×10⁶, which is an order lower than expected. Inspite of this fact, a secondary-neutron signal is measured for the first time at the Shenguang II laser facility, which proves the method’s feasibility. The method will be used in the experiments at the prototype of Shenguang III laser facility. [ABSTRACT FROM AUTHOR]