PSI operates a cyclotron based high intensity proton accelerator routinely at
an average beam power of 1.3MW. With this power the facility is at the
worldwide forefront of high intensity proton accelerators. The beam current is
practically limited by losses at extraction and the resulting activation of
accelerator components. Further intensity upgrades and new projects aiming at
an even higher average beam power, are only possible if the relative losses can
be lowered in proportion, thus keeping absolute losses at a constant level.
Maintaining beam losses at levels allowing hands-on maintenance is a primary
challenge in any high power proton machine design and operation. In
consequence, predicting beam halo at these levels is a great challenge and will
be addressed in this paper. High power hadron driver have being used in many
disciplines of science and, a growing interest in the cyclotron technology for
high power hadron drivers are being observed very recently. This report will
briefly introduce OPAL, a tool for precise beam dynamics simulations including
3D space charge. One of OPAL's flavors (OPAL-cycl) is dedicated to high power
cyclotron modeling and is explained in greater detail. We then explain how to
obtain initial conditions for our PSI Ring cyclotron which still delivers the
world record in beam power of 1.3 MW continuous wave (cw). Several crucial
steps are explained necessary to be able to predict tails at the level of
3\sigma ... 4\sigma in the PSI Ring cyclotron. We compare our results at the
extraction with measurements, obtained with a 1.18 MW cw production beam. Based
on measurement data, we develop a simple linear model to predict beam sizes of
the extracted beam as a function of intensities and confirm the model with
simulations.Comment: Corrections and new figur
