Construction, test and operation of a proton range radiography system

We describe a Proton Range Radiography system with an imaging area of 10×10 cm2, deploying a pair of Gas Electron Multiplier position-sensitive detectors and a scintillator stack to measure the residual proton range after crossing a target. The detector has been tested in the laboratory and in beam exposures at the Paul Scherrer Institute; images recorded with several phantoms of variable thickness and composition confirm the sub-millimetre accuracy and few percent energy resolution of the instrument. A new device with identical design and larger acceptance, 30×30 cm2, is in construction.