[SLAC] [SLAC Pubs and Reports]

SLAC-AP-122
Narrow-Band Impedance of the PEP-II Collimators

Abstract

Collimators in the PEP-II High Energy Ring (HER) and Low Energy Ring (LER) may contribute large impedance to the rings because of its close proximity to the beam. The collimators, which normally intrude into the vacuum chamber, surprisingly, support a novel type of localized modes that can generate large transverse narrow-band impedance. Numerical simulations show that the transverse impedance can be substantially reduced by appropriate choice of the collimator geometry. Another possibility is the excitation of trapped modes between two closely spaced collimators. The leakage of these modes through the collimator apertures into the beampipe are evaluated to determine their possible effects on the beam instability. The analysis presented here can be applied to other beamline components intruding into the vacuum chamber such as masks and insertion devices.

Full Text

PDF

Compressed PostScript

Notes

1)The present version of SLAC-AP-122 was revised on April 20, 1999 from the original version posted at SLAC on April 13, 1999.

2)The PDF version of this document was distilled from a PostScript file most likely created from LaTeX source which used Type 3 fonts. The resultant PDF may be unreadable on the screen at the default viewing magnification (fonts will appear bitmapped, jagged), though the type will be legible at higher magnifications.

Despite the cosmetic problems resulting from the use Type 3 fonts in the original source file, such PDF files print without problems; likewise, the onscreen text is searchable and selectable.

More Information

Full bibliographic data for this document, including its complete author list, is (or soon will be) available from SLAC's SPIRES-HEP Database.
Please report problems with this file to posting@slac.stanford.edu. The SLAC preprint inventory is provided by the SLAC Technical Publications Department.
Page generated 05 Apr 2001 @ 11:07 PDT by htmlme.pl