Characterization of the response and the intrinsic efficiency of a 4He scintillation detector to fast mono-energetic neutrons

The general features of a ⁴He gas scintillator prototype detector were characterized, as an alternative to liquid and plastic scintillators for a potential integration into the Radial Neutron Camera (RNC) in ITER. Two measurement campaigns were conducted at the Physikalisch-Technische Bundesanstalt (PTB) Ion Accelerator Facility (PIAF) in Germany using fast mono-energetic neutrons. Results from the first measurement campaign showed a light output response of the detector linear with the incident neutron energy, at least up to 14.8 MeV. A complete discrimination between neutrons and gammas was achieved by applying a 0.30 MeV threshold in terms of deposited neutron energy. The response function and the intrinsic efficiency of the detector were characterized in a second measurement campaign using collimated-beam conditions, similar to those expected in the RNC at ITER, to test the suitability of the detector in such a diagnostic system. The response function to 2.5 MeV and 14.8 MeV mono-energetic neutrons was measured and validated by Monte Carlo simulations. Some changes to the present prototype may be considered in the future to make it suitable as a neutron detector for the RNC at ITER.