Reduction of recombination effects in large plane parallel beam monitors for FLASH radiotherapy with scanned ion beams.

Purpose: Radiotherapy escalating dose rates above 50Gys, might offer a great potential in treating tumours while further sparing healthy tissue. However, these ultra-high intensities of FLASH-RT lead to new challenges with regard to dosimetry and beam monitoring. FLASH experiments at HIT (Heidelberg Ion Beam Therapy Center) and at GSI (GSI Helmholtz Centre for Heavy Ion Research) have shown a significant loss of signal in the beam monitoring system due to recombination effects.