Central orbit program for a variable energy multi-particle cyclotron

Abstract

In a variable energy multi-particle cyclotron, programming the beam on the first turns faces the difficulty that large readjustments of source, puller and defining slit positions may be necessary when the operating conditions are changed. Two distinct solutions of a central orbit program, constant dee-voltage and constant orbit geometry, are discussed with respect to ion capture efficiency, feasibility of readjustments and applicability of the similarity theorems. Theoretical analysis shows that the range of acceptable starting phases depends essentially on transit time and space charge effects in the first accelerating gap and may change considerably when turning from first to higher harmonic acceleration. As a result of calculations, several diagrams are presented as a guide to accomplish necessary readjustments of central geometry.