The particle tracking code BBCNI for negative ion beams and its application to BATMAN upgrade

Abstract

For the continued improvement and development of large negative hydrogen ion sources for NBI applications, beam characterisation is of critical importance for understanding and predicting the interaction of a large beam with, for example, a gas neutraliser system. As large ion beams are comprised of collections of individual beamlets, the relationship between the results of beam diagnostics and the physical properties of the beam is not a trivial one. Measured quantities come from the mixing of information from different beamlets, and the extraction of beamlet level data may not be possible. To establish the links between diagnostic results and beamlet behaviour, the particle tracking code BBCNI has been designed to forward calculate simulated diagnostics from particle level data, including beam emission spectroscopy (BES) and calorimeter measurements. Full traceability of these synthetic diagnostics allows features to be linked to specific particle populations and areas of the beam, providing a much-needed understanding of experimental results. In order to demonstrate the capability of the code, the first experimental BES results from the BATMAN Upgrade test facility are also presented. Measurements of beam divergence as calculated from real and synthetic data are shown to be in good agreement, and it is demonstrated how the code can give details of individual beamlet properties and how these build into synthetic diagnostic data.