Simulation results of bent crystal extraction in the Tevatron

Abstract

We present simulation results describing parasitic extraction of a high energy proton beam from the Tevatron via a bent Silicon crystal — demonstrated recently by E853 experiment at Fermilab. In a spirit of parasitic extraction the transverse phase-space of the beam is initially prepared, so that only high amplitude particles from the beam halo interact with the Silicon crystal (inserted into the beam), without affecting the ‘core’ of the beam. As a result of the beam halo-crystal interaction (multiple scattering and wide angle nuclear interaction), some fraction of the beam halo channels into the crystal — a multi-turn extraction occurs. The ultra strong focusing environment of a crystal channel combined with the externally imposed curvature (vertically bent crystal) provide excellent guiding features of an efficient extraction line. Here, we use a realistic model of the Tevatron lattice to describe the beam optics of the machine. Presented phase-space simulation describes a ‘kick’ mode of the E853 experiment. To enhance the beam halo interaction with the crystal, the proton beam is initially excited by firing a transverse kicker, which induces horizontal oscillations of the beam centroid on the subsequent turns. A realistic phase-space tracking yields turn-by-turn channeling efficiency, which sheds light on multi-turn extraction mechanisms. It also allows us to optimize experimental configuration parameters for maximum extraction efficiency.