The investigation of injection timing for the IPNS RCS

The Rapid Cycling Synchrotron (RCS) of the Intense Pulsed Neutron Source (IPNS) at ANL accelerates > 3.0 times 10¹² protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During each acceleration cycle, the RF varies from 2.21 MHz to 5.14 MHz. In order to improve capture efficiency, we varied the injection timing and the early RF voltage profiles. The experimental results are compared with simulation results obtained with the 1-D tracking code, CAPTURE. This allowed us to optimize injection time and the RF voltage profile for better capture efficiency. An optimized injection time and RF voltage profile was found that resulted in raising the capture efficiency from 85.1% to 88.6%. These studies have now also been expanded to include second harmonic RF during the capture and initial acceleration cycle in the RCS.