Secondary emission monitor for low-interception monitoring (SLIM): an innovative nondestructive beam monitor for the extraction lines of a hadrontherapy center

Real-time monitoring of hadrontherapy beam intensities and profiles is a critical issue for the optimization of the dose delivery to the patient tumour tissue, the patient safety, and the operation of the accelerator complex. For this purpose, an innovative beam monitor, based on the secondary emission of electrons by a nonperturbative, submicrometer-thick Al target placed directly in the extracted beam path, is being proposed. The secondary electrons, accelerated by an electrostatic focusing system, are detected by a monolithic silicon position sensitive sensor, which provides the beam intensity and position with a precision of 1 mm at a 10-kHz frame rate. The conceptual design and the engineering study optimized for hadrontherapy are presented together with the results of the laboratory tests with thermoionic electrons and the first measurements in a hadron beam.