Accession Number DE2012-1045200
Title Intensity Effects of the Facet Beam in the SLAC Linac.
Publication Date Jul 2012
Media Count 3p
Personal Author F. J. Decker G. Yocky G. R. White J. Sheppard M. Woodley N. Lipkowitz U. Wienands
Abstract The beam for FACET (Facility for Advanced aCcelerator Experimental Tests) at SLAC requires an energy-time correlation ('chirp') along the linac, so it can be compressed in two chicanes, one at the midpoint in sector 10 and one W-shaped chicane just before the FACET experimental area. The induced correlation has the opposite sign to the typical used for BNS damping, and therefore any orbit variations away from the center kick the tail of the beam more than the head, causing a shear in the beam and emittance growth. Any dispersion created along the linac has similar effects due to the high (>1.2% rms) energy spread necessary for compression. The initial huge emittances could be reduced by a factor of 10, but were still bigger than expected by a factor of 2-3. Normalized emittance of 3 (micro)m-rad in Sector 2 blew up to 150 (micro)m-rad in Sector 11 but could be reduced to about 6-12 (micro)m-rad, for the vertical plane although the results were not very stable. Investigating possible root causes for this, we found locations where up to 10 mm dispersion was created along the linac, which were finally verified with strong steering and up to 7 mm settling of the linac accelerator at these locations.
Keywords Beam emiitance
Compression
Correlations
Damping
Linac accelerators
Shear
Stanford Linear Accelerator Center

 
Source Agency Technical Information Center Oak Ridge Tennessee
NTIS Subject Category 46 - Physics
Corporate Author Stanford Research Inst., Menlo Park, CA.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1303
Contract Number DE-AC02-76SF00515

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