Development of a novel solid state detector for beam monitoring in proton therapy

Proton therapy is a very attractive and promising modality in cancer treatment that relies on the depth dose distribution property known as Bragg peak. This localized and bettercontrolled dose distribution in comparison to X-rays, improves the therapeutic ratio while sparing the healthy tissue surrounding the tumors. The beam energy is one of the key parameters in proton therapy that defines the depth inside the patient (up to 30 cm) at which the radiation is deposited with the required clinical range accuracy of 1 mm. Range deviations alter the dose distribution, leading to under-dosage of the distal edge of the tumor or normal structure over-dosage. The beam range verification is mainly performed by measuring the integrated depth-dose profiles in water phantoms and using multi layers ionization chambers and just in the routine quality control checks. This thesis is focused on the development and the use of the Ultra-Fast Silicon Detector (UFSD), chosen as innovative proton beam monitor. UFSDs are thin silicon sensors based on the Low Gain Avalanche Diode technology (LGAD), which should overcome the limitations of ionization chambers. They can be used for the energy check during the irradiation, and for the development of new beam monitors for future delivery schemes employing fast energy modulation systems. The prototype consists of two thin UFSDs, aligned along the clinical proton beam direction in a telescope configuration that allows to measure the time-of-flight (TOF) of proton to determine the beam energy .