WAKE-FIELD COMPENSATION IN ENERGY RECOVERY LINACS

Problems created by the correlated energy spread that wake elds can produce are strongly enhanced in Energy Recovery Linacs (ERLs), as compared to conventional linacs. This is due to the fact that in ERLs the spent beam is decelerated by a potentially large factor, which increases the relative energy spread proportionally. We show how severe this problem is for the impedance budget of the x- ray ERL that Cornell plans to build, and we analyze sev- eral different possibilities to compensate the correlated en- ergy spread involving de-phasing linac components, linear and nonlinear time-of-ight terms in different accelerator sections, or high frequency accelerating cavities. Because of the particular design, which has a turn-around loop be- tween two sections of the linac, there are many options for these techniques, which we compare and evaluate.