Diagnostic Technique of Neutron Doppler Broadening for Indirectly-Driven Implosions

摘要

The neutron Doppler broadening in inertial confinement fusion has been acquired from the time of flight for the neutron, from which the fuel ion temperature can be derived. An ultrafast-quenched plastic scintillation detector was used to measure the time of flight for the neutron at a low-imploded DT neutron yield (5 x 10~7 ～ 1 x 10~8) in the experiment performed on the Shenguang II laser facility. The typical temperatures of ablating targets for indirect drive were around 2.8 keV and the uncertainties were +- 30% ～ +- 40%. The detection efficiency of the detector for DT neutrons was calibrated at a K-400 accelerator. The time response function of the detection system was calibrated by imploded neutrons from a DT-filled capsule, which can be regarded as a S function pulsed neutron source due to its much narrower pulse width than that of the measured neutron time-of-flight spectrum.