Analysis of the Deuteron Distribution Emerging from the FMIT RFQ

Knowledge of the properties of the input beam is necessary for evaluating losses in a drift-tube linac (DTL). The FMIT (Fusion Materials Irradiation Test Facility) accelerator will use a Radio-Frequency Quadrupole (RFQ) structure as the first accelerator stage that feeds a drift-tube section. As the first step in evaluating beam spill in the drift-tube section and output transport, we studied the properties of the beam exiting the RFQ. An RFQ, because of its electric-field focusing, allows particles of any energy to pass through its structure. Thus, its output is essentially different from the output of an accelerator that uses strong focusing magnets. The study presents surfaces giving the number of particles as a function of position in various planes of phase space. Two PARMILA codes were used: a standard longitudinal position dependent code, and a time dependent code. The codes give slightly different answers.