An irradiation facility with a vertical beam for radiobiological studies

A vertical beam facility for radiobiological experiments was designed and constructed at the Munich Tandem-Accelerator Laboratory. The main part of the facility is a 90° dipole magnet bending the beam of protons or heavy particles into a vertical upward direction, which is advantageous for wet-cell irradiation. After collimation the beam is spread out passively by thin scattering foils and dynamically by magnetic coils. A homogeneity of the radiation field better than ±5% has been achieved over the diameter of the exit window of 60mm. The dose rate can be widely adjusted from single particles to more than 1010 particles (i.e. hundreds of Grays) per second. The dose measurement is based on single-particle counting and on standard dosimeters. The detector system for dosimetry and irradiation control is described. In a first radiobiological experiment the cell survival of chinese hamster cells was measured after irradiation with 22.7MeV protons and compared with the X-ray result.