CERN Accelerating science

Article
Title	ORIC Beam Energy Increase
Author(s)	Mallory, Merrit L ; Ball, Jim ; Dowling, Darryl ; Hudson, Ed ; Lord, Dick ; Tatum, Alan
Affiliation	(ORNL, Oak Ridge, Tennessee)
Publication	2005
In:	21st IEEE Particle Accelerator Conference, Knoxville, TN, USA, 16 - 20 May 2005, pp.2257
Subject category	Accelerators and Storage Rings
Abstract	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 nu r equal one resonance. Most cyclotrons extract after the nu r equal one resonance, thus getting more usage of the magnetic field for energy acceleration. We have now determined that the electrostatic deflector septum interferes with the last accelerated orbit in ORIC, with the highest extraction efficiency obtained near the maximum nu r value. This nu r provides a rotation in the betatron oscillation amplitude that is about the same length as the electrostatic septum thus allowing the beam to jump over the interference problem with the septum. With a thinned septum we were able to tune the beam through the nu r equal one resonance and achieve a 20% increase in beam energy. This nu r greater than one extraction method may be desirable for very high field cyclotrons since it provides ten times the clearance at extraction compared to dee voltage gain, thus allowing the possibility of utilizing a magnetic extractor.