Dynamics of the off axis intense beam propagation in a spiral inflector

In this paper the dynamics of space charge dominated beam in a spiral inflector is discussed by developing equations of motion for centroid and beam envelope for the off axis beam propagation. Evolution of the beam centroid and beam envelope is studied as a function of the beam current for various input beam parameters. The transmission of beam through the inflector is also estimated as a function of the beam current for an on axis and off axis beam by tracking a large number of particles. Simulation studies show that shift of the centroid from the axis at the inflector entrance affects the centroid location at the exit of the inflector and causes reduction in the beam transmission. The centroid shift at the entrance in the horizontal plane (h plane) is more critical as it affects the centroid shift in the vertical plane (u plane) by a large amount near the inflector exit where the available aperture is small. The beam transmission is found to reduce with increase in the centroid shift as well as with the beam current.