A dc and pulsed-mode 75 keV proton injector has been developed and is used in characterization of a continuous-wave 6.7 MeV, 100 mA radio-frequency quadrupole (RFQ). The injector is used frequently at the full RFQ design power (100 mA, 6.7 MeV) where the RFQ admittance (1 rms, normalized) is 0.23 (π mm mrad). The injector includes a 2.45 GHz microwave proton source and a beam space-charge-neutralized, two magnetic-solenoid, low-energy beam-transport system. The design RFQ beam transmission of 95% has been demonstrated at 100 mA RFQ output current.
The ion source for the Spallation Neutron Source is a radio-frequency (rf) multi-cusp, volume-type H− source that is coupled to a rf quadrupole accelerator through a low energy beam transport (LEBT) system consisting of five electrostatic elements. To gain a deeper understanding of the operation of this system and to continue to refine the design, we have performed ion extraction and transport simulations using the computer code PBGUNS. A comparison is presented between simulation and the measured phase space of the beam for various values of LEBT electrode potentials. Both the emittance magnitude and orientation in phase space were found to be in reasonable agreement with measurement. A design study is also presented where the angle of the source outlet electrode has been optimized with the aid of PBGUNS simulations, resulting in a substantial reduction of the emittance.
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