PSI, Villigen
The longitudinal-horizontal 2-dimensional (2D) density distribution of a bunched 2.2 mA beam of ~72 MeV protons has been measured at the last turns of the Injector 2 cyclotron, in the middle of the transfer line to and at the first turns of the Ring cyclotron. Protons scattered by a thin carbon-fibre target are stopped in a scintillator-photomultiplier detector. The longitudinal bunch shape is given by the distribution of arrival times measured with respect to the 50 MHz reference signal from the acceleration cavities. More probes are foreseen at 72 and 590 MeV which will use additional fibres to also determine the longitudinal-vertical and two longitudinal-diagonal 2D density distributions. These measurements together with more detailed beam transport calculations will support the matching of beam core and halo and the quest for a reduction of beam losses. The achievable dynamic range in the given environment of the cyclotrons and the connecting beam line is discussed.
Tsinghua University, Beijing
PSI, Villigen
TUB, Beijing
CIAE, Beijing
The 1.3 MW of beam power delivered by the PSI 590 MeV Ring Cyclotron together with stringent requirements regarding the controlled and uncontrolled beam losses poses great challenges with respect to predictive simulations. A new particle matter interaction model in OPAL is taking into account energy loss, multiple Coulomb scattering and large angle Rutherford scattering. This model together with the 3D space charge will significantly increase the predictive capabilities of OPAL. We describe a large scale simulation effort, which leads to a better quantitative understanding of the existing PSI high power proton cyclotron facility. The initial condition for the PSI Ring simulations is obtained from a new time structure measurements and the many profile monitors available in the 72 MeV injection line. A large turn separation and narrow beam size at the extraction turn is obtained. We show that OPAL can precise predict the radial beam pattern at extraction with large dynamic range (3-4 orders of magnitude). The described capabilities are mandatory in the design and operation of the next generation high power proton drivers.
