Open fire on tumours

At the treatment stations of the Centre for Proton Therapy at PSI (shown here, Gantry 3), tumours can be irradiated from any direction. Therefore the gantry or its irradiation head must be rotated around the patient. The enormous rotating body (3) of the gantry weighs 220 tons and is up to 10.5 metres wide. This mass is due to a rotating steel framework, nine magnets for directing the proton beam, the vacuum tube in which the protons are bundled, devices for radiation diagnostics, and a 1.5-metre-wide cable carrier, among other things. The rotation itself is accomplished by two electric motors with ten hp each.