A Real-Time Beam Monitor for Hadrontherapy Applications Based on Thin Foil Secondary Electron Emission and a Back-Thinned Monolithic Pixel Sensor

A novel, non-disruptivebeam profile monitor for low intensity light-ion beams has been constructed and tested. The system is designed for use in medical hadrontherapy centers where real-time monitoring of the beam intensity profile is of great importance for optimization of the accelerator operation, patient safety and dose delivery. The beam monitor is based on the detection of secondary electrons emitted from a submicron thick Al2O3 foil placed in the beam at an angle of 45 degrees. The present paper reports the latest results achieved with a customized backthinned monolithic active pixel array, which provides the beam intensity and position with a precision of better than 1 mm at a 10 kHz frame rate. The monitorperformancehas been tested with a patterned beam, produced with a multihole collimator, with the results indicating that the system performs according to its design specifications.