1st Workshop - Trento Proton Beam Line Facility

MoVeIT detectors characterization at Trento Proton Beam Line Facility

9 Nov 2020, 13:50

10m

Medical Physics Applications

Speaker

Anna Vignati (TO)

Description

Within the MoVeIT project of the National Institute for Nuclear Physics (INFN), the University of Torino and the INFN are investigating Ultra-Fast Silicon Detectors (UFSD) for proton beam monitoring in order to replace ionization chambers currently in use in Hadrontherapy.
Two devices are being developed based on UFSD: one for measuring the beam energy using Time-of-Flight (ToF) techniques, and the other aiming at counting single particles up to 100 MHz/$c{m}^2$. Strip sensors of two geometries {20 strips of 2.25 $m{m}^2$ (150 $\mu$m width x 15000 $\mu$m length, 216 $\mu$m pitch); 30 strips of 2.40 $m{m}^2$ (80 $\mu$m width x 30000 $\mu$m length, 146 $\mu$m pitch)} produced by FBK (Fondazione Bruno Kessler, Trento, Italy) were used for counting, while pads (80 $\mu$m active thickness, 3x3 $m{m}^2$ sensitive area) produced by HPK (Hamamatsu Photonics K.K., Japan), and strip sensors (600 $\mu$m pitch, 50 $\mu$m active thickness, 2.2 $m{m}^2$ sensitive area) produced by FBK were used for energy measurement. Tests for preliminary characterization were performed in the experimental room of the Trento Proton Therapy Center (Azienda Provinciale per i Servizi Sanitari, APSS), with 60-250 MeV clinical proton beams at ${10}^6$ − ${10}^9$ p/s fluxes. Varying the flux at different energies, the particle rate was measured and compared with the one estimated by a pin-hole ionization chamber. The energy was obtained using ToF measurements from the telescope of two UFSDs sensors placed at a specific distance between each other and aligned along the beam direction.
The achieved efficiency of the counter prototype was greater than 98 % up to ${10}^8$ p/s*$c{m}^2$ and few hundreds of keV deviations from nominal energies were achieved for all beam energies at 67 and 97 cm distance between the sensors corresponding to < 1 mm range.
These promising results demonstrate that UFSD could be a viable option to improve the conventional monitors and further improvements are therefore being developed. Among them, a new detector geometry is being produced by FBK to cover a sensitive area of 2.74 x 2.74 $c{m}^2$ and will be tested in the coming months, it features 146 strips of 114 $\mu$m width x 26214 $\mu$m length, 180 $\mu$m pitch.