Proton irradiation facility for radiobiological studies at a 7 MV Van de Graaff accelerator

Abstract

This paper describes the proton irradiation facility built up at the 7 MV Van de Graaff accelerator of the INFN-Laboratori Nazionali di Legnaro for radiobiological studies. The system mainly consists of two vacuum chambers, a fast tantalum shutter for intercepting the beam and a beam line containing the beam collimator arrangement and ending with a thin window for the beam extraction in air. Each chamber houses a Ta beam collimator, an Au scatterer foil for the broadening and uniformization of the proton beam over the cell samples and a solicon surface barrier detector for beam monitoring purposes. The test of the facility performance is discussed. With the double scattering system a counting rate in air as low as hundreds of protons per second and a fluence heterogeneity less than 5% within a circular field of 15 mm diameter were obtained. The first results of survival studies of Chinese hamster lung cells (V79-753B) irradiated with a 1.1 MeV proton beam are presented. For comparison, results obtained irradiating the cells with 200 kV X-rays are reported, too.