Wakefields in the LCLS Undulator Transitions

Bane, Karl L.F. ; /SLAC ; Zagorodnov, Igor A. ; /DESY

Stanford Linear Accelerator Center

关键词: Wiggler Magnets Accelerators,Accphy;    Collimators;    43 Particle Accelerators;    Shape;    Accelerators,Accphy;   

DOI  :  10.2172/878788
RP-ID  :  SLAC-PUB-11388
RP-ID  :  AC02-76SF00515
RP-ID  :  878788

美国|英语

来源: UNT Digital Library

【 摘 要 】

We have studied longitudinal wakefields of very short bunches in non-cylindrically symmetric (3D) vacuum chamber transitions using analytical models and the computer program ECHO. The wake (for pairs of well-separated, non-smooth transitions) invariably is resistive, with its shape proportional to the bunch distribution. For the example of an elliptical collimator in a round beam pipe we have demonstrated that--as in the cylindrically symmetric (2D) case--the wake can be obtained from the static primary field of the beam alone. We have obtained the wakes of the LCLS rectangular-to-round transitions using indirect (numerical) field integration combined with a primary beam field calculation. For the LCLS 1 nC bunch charge configuration we find that the total variation in wake-induced energy change is small (0.03% in the core of the beam, 0.15% in the horns of the distribution) compared to that due to the resistive wall wakes of the undulator beam pipe (0.6%).