Towards quantitative simulations of high power proton cyclotrons

Abstract

We describe a large scale simulation effort using Object Oriented Parallel Accelerator Library, that leads to a better quantitative understanding of the existing Paul Scherrer Institut high power proton cyclotron facility. The 1.3 MW of beam power on target poses stringent constraints on the controlled and uncontrolled beam losses. We present initial conditions for the Ring simulation, obtained from the new time-structure measurement and the many profile monitors of the 72 MeV transfer line. A trim coil model is developed, including trim coil TC15, which is needed to avoid the dangerous ${\ensuremath{\nu}}_{r}=2{\ensuremath{\nu}}_{z}$ resonance. By properly selecting the injection position and angle (eccentric injection), the flattop voltage, and phase, very good agreement between simulations and measurements at the radial probe RRE4 is obtained. We report on $3--4$ orders of magnitude in dynamic range when comparing simulations with measurements. The relation between beam intensity, rms beam size, and accelerating voltage is studied and compared with measurement. The demonstrated capabilities are mandatory in the design and operation of the next generation high power proton drivers. In an outlook we discuss our future plans to include more physics into the model, which eventually leads to an even larger dynamic range in the simulation.