Search Results (2 total)

In this paper, we discuss the optics effects of the realistic detector solenoid field on beam size at the interaction point (IP) of a future linear collider and their compensation. It is shown that most of the adverse effects on the IP beam size arise only from the part of the solenoid field which overlaps and extends beyond the final focusing quadrupoles. It is demonstrated that the most efficient and local compensation can be achieved using the novel method of weak antisolenoids near the IP, while a correction scheme which employs only skew quadrupoles is less efficient, and compensation with strong antisolenoids is not appropriate. One of the advantages of the proposed antisolenoid scheme is that this compensation works well over a large range of the beam energy.

BL11, the most recently installed wiggler in the SPEAR storage ring at the Stanford Synchrotron Radiation Laboratory, produces a large nonlinear perturbation of the electron beam dynamics, which was not directly evident in the integrated magnetic field measurements. Measurements of tune shifts with betatron oscillation amplitude and closed orbit shifts were used to characterize the nonlinear fields. Because of the narrow pole width in BL11, the nonlinear fields seen along the wiggling electron trajectory are dramatically different from the magnetic measurements made along a straight line with a stretched wire. This difference explains the tune shift measurements and the observed degradation in dynamic aperture. Because of the relatively large dispersion (1.2 m) at BL11, the nonlinearities particularly reduced the off-energy dynamic aperture. Because of the nature of these nonlinear fields, it is impossible, even theoretically, to cancel them completely with short multipole correctors. Magic finger corrector magnets were built, however, that partially correct the nonlinear perturbation, greatly improving the storage ring performance.