Optimisation of the spatial linearity in backgammon-type multi-wire gas proportional counters—The relevance of charge cloud distribution

The backgammon-type multi-wire gas proportional counter (MWPC) enables the detection of X-ray photons in two dimensions with a high degree of spatial linearity. An accurate simulation of the detector geometry is developed to further optimise the spatial linearity achievable, by modelling the ideal linear output and through mapping of the experimental residual signature. Three models are presented, each achieving considerable improvements on key linearity measures over previous work, and providing strong evidence for the dependence on charge cloud distribution. Linearity to micron levels across 24 mm are demonstrated for MWPCs.