Contribution of random noise in the ITER RNC diamond neutron detectors pulses to the counting rate uncertainty

Abstract

The main goal of the ITER Radial Neutron Camera (RNC) is to provide the plasma neutron emission profile (neutron emissivity) through measurement of the uncollided 14 MeV and 2.5 MeV neutrons from deuterium-tritium (DT) and deuterium-deuterium (DD) fusion reactions. The system is based on an array of detectors (diamonds are among the candidate detectors) located in collimated lines of sight (LOS) viewing the plasma through the ITER Equatorial Port Plug #1. Tomographic reconstruction techniques are used to calculate the neutron emissivity.The contribution of random noise on diamond detector pulses to the count rate uncertainty is investigated in this paper. The energy spectrum of the neutrons impinging on the detector has been calculated by means of MCNP calculations for one line of sight of the RNC In-Port system. The spectrum has been convoluted with the diamond detector response functions and the Pulse Height Spectrum (PHS) has been obtained. Experiments have been carried out with the CAEN™ 5810D detector emulator, that is able to produce arbitrary pulse height distributions as those expected in the ITER RNC. Random noise has been added on each detector pulse of the distribution using the detector emulator. The resulting uncertainty produced on the count rate has been evaluated as a function of the random noise level.