Oxygen gas-sheet beam profile monitor for the synchrotron and storage ring

A fast, non-destructive beam-profile monitor was developed using an oxygen gas-sheet target in the Heavy Ion Medical Accelerator in Chiba synchrotron. The size of the gas-sheet target was 85 mm in width and 1.3 mm in thickness, of which the density was 1 x 10(-4) Pa. The base vacuum in the ring was not deteriorated by this gas-sheet target, and was on the order of 10(-8) Pa. In typical cases, carbon ion beams are accelerated from 6 to 290-430 MeV/n for cancer therapy, in which the intensity is 2.5 x 10(8) particles/bunch. For these beams, two-dimensional beam profiles were successfully measured within the time (similar to100 ns) of the bunch separation. This article describes both the technical and physical aspects of the monitor together with some results. (C) 2004 Elsevier B.V. All rights reserved.