Characterization of Liquid Scintillator-Based CNES for Deuterium–Deuterium Neutron Emission Spectroscopy in the LHD

The compact neutron emission spectrometers (CNES) based on conventional liquid (EJ-301) scintillation detectors were characterized in this work. The CNESs were employed for deuterium-deuterium neutron emission spectroscopy in the Large Helical Device (LHD). Prior to the installation, the EJ-301 scintillation detectors were characterized at the Fast Neutron Laboratory of Tohoku University. In order to discriminate the neutron and γ-ray signals, the charge comparison method was used. The neutron energy spectrum was successfully unfolded from the measured recoil proton energy spectrum of the EJ-301 scintillation detector using the derivative unfolding technique. The detector's energy resolution was examined. In the LHD, EJ-301 based CNESs with both tangential and perpendicular line-of-sight were employed to characterization. Furthermore, the characterization of the CNES was performed in the deuterium-deuterium experiment campaign. The operational capabilities of CNESs in the LHD were examined. Deuterium-deuterium neutron emission spectroscopy in various approaches of neutral beam (NB)-heated plasmas was conducted using CNES. Because of the high energy of the injected fast-ions from tangential NB injection, an investigation of the Doppler effect on deuterium-deuterium neutron energy was conducted. The upper and lower shifted deuterium-deuterium neutron energies were observed when the fast-ions moved towards and away from the tangential CNES, respectively. As expected, no notable energy shift was observed from fast-ions injected by the perpendicular NB injection. Additionally, the five-dimensional orbit following code DELTA5D, which takes into account Larmor motion effects and the detector's energy resolution, was utilized to compute the expected deuterium-deuterium neutron energy spectrum that would be measured by the CNES. There was a concurrence between the calculations and experimental results.