ANTS: A simulation package for gas scintillation Anger camera in thermal neutron imaging

A gas scintillation Anger camera for thermal neutron imaging is being developed in the frame of the NMI3 FP7 Project 226507 collaboration. The detection medium is a high pressure gas mixture of ³He and CF4. An array of photomultiplier tubes (PMTs) registers photons of the CF4the PMTs. Several secondary scintillation generated in the electron avalanches at the MSGC (MicroStrip Gas Chamber) plate. The detector is expected to have sub-millimeter spatial resolution, high counting rate (up to 1 MHz) and good (>50%) detection efficiency. A custom and fully interactive Monte Carlo simulation package (ANTS: Anger camera Neutron detector Toolkit for Simulations) was developed to optimize the design of the detector in order to reach the highest possible spatial resolution. The simulation code accounts for all relevant physical processes in the gas: neutron capture, energy deposition, electron drift, electron multiplication and secondary scintillation. Individual photons are tracked through the gas and the output window (wavelength-resolved refraction and transmission are implemented). Photo-detection accounts for the angular response, active area non-uniformity, gain and single-photon spectra of the PMTs. Several PMT read-out patterns and localization algorithms are implemented in the package. The results of simulations reproduce well the preliminary results obtained with small-scale detector prototypes.