Space charge dominated beam dynamics in a spiral inflector for a compact cyclotron

Beam optical properties of a spiral inflector in the presence of space charge effects have been studied for a high-current compact proton cyclotron. The space charge effect has been incorporated in the paraxial ion trajectory calculations considering the beam as a uniform ellipsoidal bunch. The increase in the current in the bunch due to bunching as the beam passes through the inflector has been included in the beam dynamics. The initial conditions of the beam have been optimized to reduce the emittance growth at the exit of the inflector. The four-dimensional transverse acceptance of the spiral inflector as a function of beam current has been estimated. We have also used the infinitesimal transfer matrix technique to estimate the beam envelope and compared the results with those obtained by paraxial ray tracing.