Complementary dosimetry for a 6 MeV electron beam

Abstract

Two methods for inferring the dose of the electron beam (EB) provided by the ALID-7 linear accelerator (LINAC) are compared. The main parameters of the electron beam are: energy 6MeV, pulse duration 4μs and frequency 53Hz. The reference dosimeter is a graphite calorimeter built in-house, whose measured dose depends on the irradiation time. In order to modify the dose for a given irradiation time, the voltage applied on the filament of the electron gun is varied in the range 8–12 V. The calorimeter can provide reliable measurements (doses above 0.48kGy) for irradiation times sufficiently long (above 10 s) and for filament voltages where stable operation of the LINAC is achieved (above 9 V). The measured dose is compared with that deduced from measurements of the beam fluence given by a Faraday cup (FC), by taking into account the stopping power features of the electron beam into graphite. The electron beam charge per pulse measured at the exit of the LINAC is between 3.7 × 10−9 C at 8 V, and 2.4 × 10−7 C at 12 V. A good match is obtained particularly at 12 V, which is the typical operating filament voltage. Keywords: Electron beam, Dosimetry, Calorimetry, Faraday cup, Thermistor