Fusion fuel ion temperature diagnostic for directly driven implosions

An ultrafast quenched plastic scintillation detector was used to measure the fusion fuel ion temperature at low implosion (DT) neutron yield $(5×108–3×109)$ in the initial experiment performed at the Shenguang II laser facility. The typical temperatures of exploding pusher targets for direct drive were around 4 keV and the uncertainties were ±15–23%. The detection efficiency of the detector to DT neutrons was calibrated at a K-400 accelerator. The time response function of the detection system was calibrated by implosion neutrons from a DT-filled capsule, which can be regarded as a δ function pulsed neutron source due to its much narrower pulse width than that of the measured neutron time-of-flight spectrum.