A real time scintillating fiber dosimeter for gamma and neutron monitoring on radiotherapy accelerators

The quality of the radiotherapic treatment depends strongly on the capability to measure the dose released in the treated volume and the one absorbed by the surrounding volumes, which is mainly due to the scattered radiation produced by the primary beam interaction with the accelerator collimating system. Radiotherapy linear accelerators produce electron (6-20 MeV) and photon (6, 18 MV) irradiating fields up to 40 × 40 cm2. Photons with energies greater than 8 MeV generate neutrons via photoproduction which are being studied for possible BNCT applications. We have developed a prototype of a real time dosimeter with 1 mm diameter scintillating and clear fibers readout by multianode photomultipliers. For neutron applications, the fibers have been coupled with boron loaded scintillator. We will describe the dosimeter and the results of the tests comparing them to the ones obtained with the standard dosimeters.