NSCL, East Lansing, Michigan, USA
Intense heavy ion beam acceleration by superconducting compact cyclotrons presents significant challenges since surfaces impacted by lost beam are subject to high thermal loads and consequent damage. High transmission efficiencies allow 0.7-1.0 kW beams to be routinely delivered for experiment at the NSCL, with minimal negative impact on reliability. Net beam transmission measured from just before the K500 to extracted beam from the K1200 can be about 30% depending on the ion used (factoring out the unavoidable loss due to the charge stripping foil in the K1200). Techniques and examples are discussed.
NSCL, East Lansing, Michigan, USA
The Coupled Cyclotrons Facility (CCF) at NSCL/MSU includes an injector cyclotron (K500) and a booster cyclotron (K1200). The beam from the K500 is injected radially into the K1200 and stripped at approximately one third of the radius at energies of approximately 10 MeV/u. Stripping is done with a carbon foil. The lifetime of the foil is very short when stripping heavy ions and does not agree with the estimates from formulas that work quite well for light ions. We will present in this paper the studies performed to understand the limitations and improve the lifetime of the foils. A foil test chamber with an electron gun has been built as part of the R&D for the Facility for Rare Isotope Beams (FRIB) project. It has been used to study different ways of supporting the carbon foils and effects of high temperature operation. Different foil materials (diamond-like carbon, graphene, etc) have been tested in the cyclotron.