Beam pulse stacking with a low energy storage ring at the Indiana University Cyclotron Facility (IUCF)

An isochronous storage ring for the DC beams from the 0.62 MV external ion source ('pre-injector') was installed in the beam line to the Indiana University k=15(k=AE/q2 MeV) cyclotron ('injector') to provide a variable reduction of the duty factor of the accelerated beams while also increasing the peak beam brightness. Ions are injected into the ring via electron removal which allows the beam to accumulate. The stored beam is ejected from the ring by a pulsed electrostatic deflector after an arbitrarily selected integer multiple of the cyclotron RF period. The peak intensity is enhanced by the accumulation between extracted pulses. Recent development tests using a 615 keV H2+ beam have demonstrated the capability of the device to provide cyclotron beams with pulse periods ranging from 1.1 to 100 μS. Peak beam intensities increase in proportion to accumulation time up to 3 μS and have reached 5 times the best intensity without using the ring. The design of the ring and the results of recent operating experiences are reported. (orig.)