Response of LaBr3(Ce) scintillators to 2.5 MeV fusion neutrons

First spatially resolved measurements of the D-3He α-particle source with the upgraded JET gamma-ray camera

The Joint European Torus (JET) gamma-ray camera has been recently upgraded with the installation of new gamma-ray detectors, based on LaBr₃(Ce) scintillation crystals, which add spectroscopic capability to the existing system allowing measurements with good energy resolution (5% at 0.622 MeV), a dynamic range from hundreds of keV up to about 30 MeV, and high counting rate capabilities of MCps. First gamma-ray measurements during the C38 campaign of the JET have been successfully carried out, in particular, in D-³He plasmas from three-ion ion cyclotron resonance heating experiments, where the detection of 16.4 MeV γ-rays from D + ³He → γ + ⁵Li reactions with the gamma-ray camera upgrade allowed determining the spatial profile of alpha particles born in D + ³He fusion reactions.

Gamma-ray spectroscopy at MHz counting rates with a compact LaBr3 detector and silicon photomultipliers for fusion plasma applications

Gamma-ray spectroscopy measurements at MHz counting rates have been carried out, for the first time, with a compact spectrometer based on a LaBr₃ scintillator and silicon photomultipliers. The instrument, which is also insensitive to magnetic fields, has been developed in view of the upgrade of the gamma-ray camera diagnostic for α particle measurements in deuterium-tritium plasmas of the Joint European Torus. Spectra were measured up to 2.9 MHz with a projected energy resolution of 3%-4% in the 3-5 MeV range, of interest for fast ion physics studies in fusion plasmas. The results reported here pave the way to first time measurements of the confined α particle profile in high power plasmas of the next deuterium-tritium campaign at the Joint European Torus.

Feasibility study on signal separation for spontaneous alpha decay in LaBr3: Ce scintillator by signal peak-to-charge discrimination

A novel analysis method named peak-to-charge ratio (V(p)/Q(total)) discrimination, aiming at background rejection especially for alpha decay self-activity in LaBr3: Ce scintillators has been developed. This method is based on a waveform analysis using the peak-to-charge ratio in the output waveform of a photomultiplier tube. The discrimination of alpha-induced events was achieved by using a threshold function based on the error propagation of the V(p)/Q(total) value. The accidental rejection ratio of gamma-induced events was evaluated to be 0.17%. Furthermore, a total absorption peak spectrum processed with the V(p)/Q(total) discrimination method for (68)Ga 1.883 MeV gamma rays, where the energy was overlapped with background alpha events, reproduced exactly the same result as that of the background subtraction method. The difference in measured peak counts of both methods was 0.716%, and the statistical error in the V(p)/Q(total) discrimination method and background subtraction was 4.81% and 8.70%, respectively. Thus a higher-accuracy measurement could be achieved using the V(p)/Q(total) discrimination method. The present study demonstrates that the V(p)/Q(total) discrimination method is a promising method for background rejection of the spontaneous alpha decay in LaBr3:Ce scintillators.