Chaotic particle motion and beam halo formation induced by image-charge effects in a small-aperture alternating-gradient focusing system

It is shown with a test-particle model that image-charge effects induce a new mechanism for chaotic particle motion and halo formation in an intense charged-particle beam propagating through an alternating-gradient focusing channel with a small aperture, circular, perfectly conducting pipe. This mechanism occurs for a well-matched beam with the Kapchinskij–Vladimirskij distribution. The percentage of beam loss to the conductor wall is calculated as a function of propagating distance and aperture size.