Title :
Shift Dependent Skew Quadrupole in Advanced Light Source Elliptically Polarizing Undulators, Cause and Corrections
Author :
Marks, S. ; Prestemon, S. ; Schlueter, R.D. ; Steier, C. ; Wolski, A. ; Jung, J.Y. ; Chubar, O.
Author_Institution :
Lawrence Berkeley Lab., Berkeley, CA
fDate :
6/1/2006 12:00:00 AM
Abstract :
Three elliptically polarizing undulators (EPU) are installed and operational at the Advanced Light Source (ALS); the most recent was installed in April ´05. Operational experience has shown a variation in electron beam size which correlates with the EPU´s magnetic quadrant shifts used to vary polarization. Storage ring electron dynamics studies pointed to the existence of a shift dependent skew quadrupole (SQ) component generated within the EPU´s. Detailed magnetic and mechanical measurements demonstrated that the field errors were the result of systematic individual magnetic block displacements which vary with quadrant shift. This paper will discuss the results of electron dynamics studies, magnetic and mechanical measurements, design modifications planned for future EPU´s to eliminate the SQ source, and the design and implementation of SQ compensation coils
Keywords :
coils; electron beams; magnetic field measurement; particle beam dynamics; permanent magnets; storage rings; wigglers; Advanced Light Source; electron beam size; elliptically polarizing undulators; magnetic block displacements; magnetic measurement; magnetic quadrant shifts; mechanical measurement; permanent magnets; quadrant shift; shift dependent skew quadrupole component; skew quadrupole compensation coils; storage ring electron dynamics; Coils; Displacement measurement; Electron beams; Light sources; Magnetic field measurement; Magnetic variables measurement; Mechanical variables measurement; Optical polarization; Shape; Undulators; Elliptically polarizing undulator; permanent magnets; skew quadrupole;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2005.869665
