LAUSR

The GEMPix is a small gaseous detector with a highly pixelated readout, consisting of a drift region, three Gas Electron Multipliers (GEMs) for signal amplification, and four Timepix ASICs with 55 μm pixel pitch and a total of 262,144 pixels (512×512 pixels). A continuous flow of a gas mixture (here propane-based tissue equivalent gas) is supplied externally at a rate of 5 L/h. By placing a sealed 241Am source outside of the detector and varying the source-detector distance, the residual energy of alpha particles entering the sensitive volume of the GEMPix through a thin Mylar window is varied. An alpha spectrometry measurement was performed to determine the emission spectrum of the source, and this spectrum was then used as an input to a FLUKA Monte Carlo simulation to obtain the residual energy of the alpha particles. Thus, a calibration curve from 5.9 keV (from an 55Fe source) up to more than 2 MeV was obtained, which is needed for future applications of the detector, in particular for microdosimetry.