Oric Beam Energy Increase

The detection of and solution to a beam interference problem in the Oak Ridge Isochronous Cyclotron (ORIC) extraction system has yielded a 20% increase in the proton beam energy. The beam from ORIC was designed to be extracted before the vr= 1 resonance. Most cyclotrons extract after the vr= 1 resonance, thus getting more usage of the magnetic field for energy acceleration. Attempts to increase the ORIC extraction radius over the past 40 years have failed. We determined that the electrostatic deflector septum in ORIC interferes with the last accelerated orbit, with the highest extraction efficiency being obtained near the maximum vr. This vrprovides a rotation in the betatron oscillation amplitude that is equal to the same length as the electrostatic septum thus allowing the beam to jump over an interference problem with the septum. With a thinned septum we were able to tune the beam to the vr= 1 resonance and achieve a 20% increase in beam energy. However, the method of extraction with vr> 1 may be useful for very high field cyclotrons since it provides greater clearance at extraction than that obtained from dee voltage gain, thus allowing the possibility of utilizing a magnetic extractor.