Self-Consistent Potential In High Intensity Deuteron Beams Simulations And Measurements

The space charge compensation process is important in order to transport ion beams with high perveance from the source to the RFQ. In particular, not fully compensated beams may develop halo and emittance growth at the entrance of the RFQ. The signal of incomplete compensation is the presence of a significant residual potential (in the range of 5% or 10% of the uncompensated potential). In order to investigate these phenomena, we performed CPU-time-demanding simulations with self consistent programs from which we could extract the information about the space charge and the potential along the transfer line (consisting of three drift spaces and two solenoid), especially at the entrance and at the exit of the solenoids, with a typical D+ beam current of 135 mA, a 0.25 mm mrad rms normalized emittance at a 100 keV input energy. We also compared the results with the FGA (four grid analyzer) measurements performed at the prototype accelerator of the IFMIF/EVEDA stage. Simulations were parallelized through message passing interface python compiled code, via the PIC code WARP. Particularly we compare the results obtained in the rz (cylindrical symmetry) and in the 3d xyz implementations, to verify whether the former approach (much faster) is accurate enough.