Physical characterization ofHe ion beams for radiotherapy and comparison withHe.

There is increasing interest in using helium ions for radiotherapy, complementary to protons and carbon ions. A large number of patients were treated withHe ions in the US heavy ion therapy project and novelHe ion treatment programs are under preparation, for instance in Germany and Japan.He ions have been proposed as an alternative toHe ions because the acceleration ofHe is technically less difficult thanHe. In particular, beam contaminations have been pointed out as a potential safety issue forHe ion beams. This motivated a series of experiments withHe ion beams at Gesellschaft für Schwerionenforschung (GSI), Darmstadt. MeasuredHe Bragg curves and fragmentation data in water are presented in this work. Those experimental data are compared with FLUKA Monte Carlo simulations. The physical characteristics ofHe ion beams are compared to those ofHe, for which a large set of data became available in recent years from the preparation work at the Heidelberger Ionenstrahl-Therapiezentrum (HIT). The dose distributions (spread out Bragg peaks, lateral profiles) that can be achieved withHe ions are found to be competitive toHe dose distributions. The effect of beam contaminations onHe depth dose distribution is also addressed. It is concluded thatHe ions can be a viable alternative toHe, especially for future compact therapy accelerator designs and upgrades of existing ion therapy facilities.