Velocity-space sensitivity of the neutron camera on MAST

Abstract

The Neutron Camera installed at the Mega Ampere Spherical Tokamak (MAST) provided fundamental information regarding the neutron emission and the behavior of fast ions. The signal measured by the Neutron Camera depended on its observation direction relative to the plasma region. Furthermore, only a certain part of the energy-pitch region contributed to the measured signal. This region is determined by the fast ion Weight Functions. In this paper, the Weight Functions of the Neutron Camera are calculated using DRESS. The results show that the instrument is most sensitive to neutrons created in fusion reactions involving a thermal ion and an ion in the beam energy region. Synthetic spectra are also calculated and, after folding with the detector's response function, compared with experimental pulse height spectra for three selected plasma discharges. Also, Weight Functions for the Neutron Camera Upgrade on MAST-U are calculated and discussed. The results can be applied for future fast ion studies at MAST-U, combining Neutron Camera Upgrade data with those of other fast ion diagnostics, such as Fast Ion Deuterium Alpha and the Neutral Particle Analyzer diagnostics.