Beam Dynamics in High Intensity Cyclotrons Including Neighboring Bunch Effects: Model, Implementation and Application

Space charge effects, being one of the most significant collective effects, play an important role in high intensity cyclotrons. However, for cyclotrons with small turn separation, other existing effects are of equal importance. Interactions of radially neighboring bunches are also present, but their combined effects has not yet been investigated in any great detail. In this paper, a new particle in cell based self-consistent numerical simulation model is presented for the first time. The model covers neighboring bunch effects and is implemented in the three-dimensional object-oriented parallel code OPAL-cycl, a flavor of the OPAL framework. We discuss this model together with its implementation and validation. Simulation results are presented from the PSI 590 MeV Ring Cyclotron in the context of the ongoing high intensity upgrade program, which aims to provide a beam power of 1.8 MW (CW) at the target destination

Charge state breeding with an ECRIS for ISAC at TRIUMF

For the acceleration of radioactive ions the usable mass range is limited by the A/q acceptance of the first accelerator stage. Since an efficient primary ion source normally produces singly charged ions, charge state breeding is necessary if higher masses are to be accelerated. At TRIUMF an ECR source has been chosen as a breeder due to its potential high efficiency in producing intermediate A/q values. To minimize the necessity for further stripping an A/q around 6 is desirable. A 14 GHz "PHOENIX" booster from Pantechnik has been set up on a test bench. The singly charged ions are produced from different ion sources, wihich can be mounted in a standard ISAC target-ion-source set-up. For the first tests an ECR source to produce noble gas beams has been chosen. The aim of the measurements at the test bench is to find the optimum operation conditions of the charge state booster and the injection and extraction ion optics. Working with radioactive ions always means that the system should aim for high efficiency, as the production of such species is limited. Therefore, special emphasis has to be put on the highest yield for the production of the desired charge state. A second point is the analysis of the extracted beam quality in order to optimize mass separation and transport efficiency. The paper shows the status of the set-up and reports on first results of the charge breeding of Ar, Ne and Xe. With Xe a total efficiency of 22.5% has been achieved

Two-neutron transfer reaction mechanisms in 12^{12}C(6^6He,4^{4}He)14^{14}C using a realistic three-body 6^{6}He model

The reaction mechanisms of the two-neutron transfer reaction $^{12}$C($^6$He,$^4$He) have been studied at 30 MeV at the TRIUMF ISAC-II facility using the SHARC charged-particle detector array. Optical potential parameters have been extracted from the analysis of the elastic scattering angular distribution. The new potential has been applied to the study of the transfer angular distribution to the 2$^+_2$ 8.32 MeV state in $^{14}$C, using a realistic 3-body $^6$He model and advanced shell model calculations for the carbon structure, allowing to calculate the relative contributions of the simultaneous and sequential two-neutron transfer. The reaction model provides a good description of the 30 MeV data set and shows that the simultaneous process is the dominant transfer mechanism. Sensitivity tests of optical potential parameters show that the final results can be considerably affected by the choice of optical potentials. A reanalysis of data measured previously at 18 MeV however, is not as well described by the same reaction model, suggesting that one needs to include higher order effects in the reaction mechanism.Comment: 9 pages, 9 figure