On the comparison of three methods of assessing beam quality for broad beam in vitro cell irradiation

The interaction of charged particles with living matter has recently attracted increasing interest in the field of biomedical applications such as hadron therapy, radioprotection and space radiation biology. Particle accelerators are particularly useful in this area.In vitro radiobiological studies with a broad beam configuration require beam homogeneity. The goal is to produce a dose distribution given to a cell population that is as close to uniform as possible.In this paper, we compare the results of three devices used to assess the beam quality for broad beam irradiation: a passivated implanted planar silicon (PIPS) particle detector, a position-sensitive solid state detector, which is camera-like, and a solid state nuclear track detector (CR39).The first device is a PIPS detector of 300 μm nominal depletion depth and an entrance window with a thickness of about 500 Å. It is collimated with a 0.5 mm aperture and mounted in air on an XY moving table as close as possible to the exit window of the beam line.The second device is a CMOS position-sensitive detector (technological process 0.6 μm AMS CUA), 112 × 112 pixels, with 153 × 153 μm² pixel size. It allows the user to rapidly obtain dose uniformity over a surface of 1 × 1 cm². During uniformity and dose rate assessment it is placed in air at the PIPS location.For both detectors, beam profile was obtained for various proton fluxes (from ∼5 × 10⁴ to 10⁶ particles cm⁻² s⁻¹). Preliminary tests were made with CR39 using 4 MeV He⁺⁺ ions.Results are analysed using Poisson distribution and cell hit probability.