Narrow-band Impedance of the PEP-II Collimators

Technical Report · Mon Apr 12 04:00:00 EDT 1999

DOI:https://doi.org/10.2172/9894· OSTI ID:9894

Heifets, Samuel A ^[1]

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1. SLAC

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.

• Research Organization: Stanford Linear Accelerator Center, Menlo Park, CA (US)
• Sponsoring Organization: USDOE Office of Energy Research (ER) (US)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 9894
• Report Number(s): SLAC-AP-122
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
BEAM DYNAMICS
COLLIMATORS
COMPUTERIZED SIMULATION
DESIGN
EXCITATION
IMPEDANCE
PEP STORAGE RINGS