Orbit Properties Relevant to Phase Selection in the MSU K500 Cyclotron

In cyclotrons the traditional method of removing undesired starting phases from the beam is a pair of slits located at the same angle but at different radii. The compact nature of the K500 cyclotron and the small turn separation makes such a system unpractical so instead we are currently constructing a system which uses two thin blades located 120° apart but at the same radius. In this system the blades act as the inverse of a slit with each blade affecting the turns on both sides of it; thus with a ¿r close to 1.0 the effect on the two turns together is the same as a slit acting on a single turn. In this paper we will present the orbit conditions which will allow this system to select starting phases.