Identifying charged particle background events in X-ray imaging detectors with novel machine learning algorithms

D. R. Wilkins, S. W. Allen, E. D. Miller, M. Bautz, T. Chattopadhyay, S. Fort, C. E. Grant, S. Herrmann, R. Kraft, R. G. Morris and P. Nulsen, 2020, Proc. SPIE "Space Telescopes and Instrumentation 202020: Ultraviolet to Gamma Ray", 11444, 308

Space-based X-ray detectors are subject to significant fluxes of charged particles in orbit, notably energetic cosmic ray protons, contributing a significant background. We develop novel machine learning algorithms to detect charged particle events in next-generation X-ray CCDs and DEPFET detectors, with initial studies focusing on the Athena Wide Field Imager (WFI) DEPFET detector. We train and test a prototype convolutional neural network algorithm and find that charged particle and X-ray events are identified with a high degree of accuracy, exploiting correlations between pixels to improve performance over existing event detection algorithms. 99 per cent of frames containing a cosmic ray are identified and the neural network is able to correctly identify up to 40 per cent of the cosmic rays that are missed by current event classification criteria, showing potential to significantly reduce the instrumental background, and unlock the full scientific potential of future X-ray missions such as Athena, Lynx and AXIS.