Abstract
Two neutron time-of-flight (nToF) detectors have been employed to measure the neutron time-of-flight spectrum in different lines-of-sight, i.e., at the equator plane and the south pole, on Shenguang-III (SG-III) laser facility. The contribution of scattered neutrons has been calculated with the Monte Carlo code JMCT for each nToF detector. The results show that the scattered neutron spectrum is dominated by neutrons scattered on materials in the experiment hall, including the vacuum chamber. The shape of the scattered neutron spectrum depends on the view line, which has been observed with nToF detectors located in the experiment hall of the SG-III laser facility. A method based on the convolution of the calculated neutron time-of-flight spectrum and the instrument response function has been developed for the ion temperature determination. The calculated neutron spectra with the contribution of scattered neutrons can fit the measured results. No obvious ion temperature anisotropy has been observed on the SG-III laser facility at present.
Highlights
The Shenguang-III (SG-III) laser facility is a 48-beam laser system
A neutron timeof-flight (nToF) system has been installed in the experiment hall to measure the ion temperature in the first low-convergence ratio implosion experiments on the SG-III laser facility in 2015.5 It was located at the equator plane with the flight length of 4.00 m for DD capsules and 9.44 m for DT capsules
A numerical model of the SG-III laser facility has been developed based on the neutron transport code JMCT
Summary
The Shenguang-III (SG-III) laser facility is a 48-beam laser system It was operated with the full energy since 2015.1 The SG-III laser facility was dedicatedly designed to perform indirect-drive implosion experiments for studying the inertial confinement fusion (ICF). beams enter the hohlraum, which is a high-Z cylinder, through the laser entrance holes (LEHs). Soft x-rays are emitted from the laser heated interior surface of the hohlraum and ablate the capsule surface. The inward compression force generated by the outwardmoving ablation materials drives the capsule to achieve highperformance implosion with high temperature and density conditions. Diagnostic systems, including the neutron timeof-flight (nToF) system, for the implosion performance assessment have been developed and installed on the SG-III laser facility. The burn-averaged ion temperatures of ICF implosions have been measured by the nToF systems on NOVA, OMEGA, NIF8–10 and SG-III5 laser facilities. The ion temperature Ti can be determined by the full width of half maximum (FWHMTOF) of the temporal spread of neutrons’ flight time at nToF detectors with the formula given by Brysk as FWHMTOF
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