• dosimetry
• flash effect
• ionizing radiations
• organic scintillators
• radiotherapy

FLASH radiotherapy shows a higher healthy tissues sparing compared to the conventional radiotherapy. To obtain the so-called FLASH effect the dose rate must be higher than 40 Gy/s and a dose of at least 10 Gy must be delivered in less than 200 ms. For electron LINAC pulsed beams, the high dose rate required causes saturation in standard ion chambers. Thanks to their fast decay times (ns) and water equivalence, plastic scintillators can be used as online dosimeters for FLASH beams. In this thesis I developed and experimentally characterized FLASH dosimeter prototypes based on two scintillating fibers of different volumes and emission spectra: a blue one with emission peak at 450 nm and a green one with peak at 530 nm. The measures were made using the ElectronFlash LINAC located at the Centro Pisano per la Flash Radiotherapy (CPFR) in Santa Chiara University Hospital. The signal emitted by the prototypes was read with a CCD.
The measured performed were the linearity of the response of the scintillators incrementing the dose per pulse (DPP), the capability to measure the percentage dose curve in solid water (PDD). The contribution of spurious light due to Cerenkov radiation in the fibers was also estimated. A five dosimeters array was tested to measure the beam profile in the transversal plane. The time structure of a single beam pulse was measured using a photodiode.
The absence of saturation makes plastic scintillating fibers good candidate for dosimetry at FLASH regime.