Extraction Studies for the Modified Nevis Synchrocyclotron

Computer studies of a regenerative beam extraction system using magnetic peeler-regenerator have been performed. We have also investigated the use of a time varying first harmonic magnetic bump as a beam stretcher. The results indicate, that we can expect a turn separation of the order of 0.8 in. at the mouth of the magnetic channel. The time varying bump makes it possible to stretch the external beam over most of the RF-off time of the acceleration cycle. For the, magnetic channel, a current configuration has been found which does not perturb the main cyclotron field outside itself and reduces the field by 4 kG inside the channel. The step from no field to full field is only 0.2 in. This 4 kG field extending over a distance of 20-in. is sufficient to lead the beam out of the machine.