Parametric studies of image-charge effects on an intense beam in a small-aperture alternating-gradient focusing system

The image-charge effects on an intense charged-particle beam propagating through an alternating-gradient focusing channel with a small aperture, circular, perfectly conducting pipe are studied using a test-particle model. For a well-matched elliptical beam with the Kapchinskij–Vladimirskij (KV) distribution, it is found that halo formation and beam loss are induced by nonlinear fields due to image charges on the wall. The halo formation and chaotic particle motion is found to depend sensitively on the system parameters: the occupancy of the quadrupole focusing field, the vacuum phase advance, the beam perveance, and the ratio of the beam size to the aperture. Furthermore, the percentage of beam loss to the conductor wall is calculated as a function of propagating distance and aperture.