Nevis Synchrocyclotron Beam Status Report

The full energy beam with vertical width 0.25 in. and projected intensity 12 W.A is a major step toward fulfilling the design goals (20 W.A) of the accelerator. We anticipate that an increase in intensity by a factor of 2 will be obtained by extending our injection time from 10 W±s (at present) to 25 ?s. By varying the timing of the source trigger, we have verified that this time window is indeed available for injection. This injection time extension will require modifying the ion source pulser. We also expect to be able to extract higher ion currents by modifying the source tip to bring the plasma closer to the extraction hole. Calculations on the operation of the extraction system indicate that we should be able to exceed 75% extraction efficiency with the vertical and radial widths measured. The adiabatic turn-off of the RF voltage, with concurrent compression of energy spread, has not yet been tested, but we expect that it will improve the extraction efficiency. We are presently installing the extraction system, and anticipate extracting beam in April 1975.