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Title: The PEP-II Movable Collimators

Abstract

Three movable collimators have been manufactured for installation in the PEP-II LER and HER beamlines upstream of BaBar to improve backgrounds in BaBar by a factor of 2. Each collimator has a pair of horizontally opposed, water cooled jaws with RF finger seals all around the edge of the jaws, these seals are the only sliding parts inside the vacuum chamber. Each jaw travels independently through a distance of 16.5 mm (LER) or 21mm (HER) and is supported above the collimator from motorized slideways with position feedback. The larger HER collimator has a titanium sublimation pump incorporated into the underside of the collimator, pumping through RF screens in the bottom of the chamber. Water cooled fixed ramps protect the leading and trailing edges of the jaws.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
877438
Report Number(s):
SLAC-PUB-11752
TRN: US0601468
DOE Contract Number:
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Prepared for 18th International Conference on High-Energy Accelerators (HEACC 2001), Tsukuba, Japan, 26-30 Mar 2001
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; COLLIMATORS; FEEDBACK; FINGERS; PUMPING; SCREENS; SUBLIMATION; TITANIUM; WATER; Accelerators,ACCPHY

Citation Formats

DeBarger, S., Metcalfe, S., Ng, C., Porter, T.G., Seeman, J., Sullivan, M., Wienands, U., and /SLAC. The PEP-II Movable Collimators. United States: N. p., 2006. Web.
DeBarger, S., Metcalfe, S., Ng, C., Porter, T.G., Seeman, J., Sullivan, M., Wienands, U., & /SLAC. The PEP-II Movable Collimators. United States.
DeBarger, S., Metcalfe, S., Ng, C., Porter, T.G., Seeman, J., Sullivan, M., Wienands, U., and /SLAC. Mon . "The PEP-II Movable Collimators". United States. doi:. https://www.osti.gov/servlets/purl/877438.
@article{osti_877438,
title = {The PEP-II Movable Collimators},
author = {DeBarger, S. and Metcalfe, S. and Ng, C. and Porter, T.G. and Seeman, J. and Sullivan, M. and Wienands, U. and /SLAC},
abstractNote = {Three movable collimators have been manufactured for installation in the PEP-II LER and HER beamlines upstream of BaBar to improve backgrounds in BaBar by a factor of 2. Each collimator has a pair of horizontally opposed, water cooled jaws with RF finger seals all around the edge of the jaws, these seals are the only sliding parts inside the vacuum chamber. Each jaw travels independently through a distance of 16.5 mm (LER) or 21mm (HER) and is supported above the collimator from motorized slideways with position feedback. The larger HER collimator has a titanium sublimation pump incorporated into the underside of the collimator, pumping through RF screens in the bottom of the chamber. Water cooled fixed ramps protect the leading and trailing edges of the jaws.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Mar 13 00:00:00 EST 2006},
month = {Mon Mar 13 00:00:00 EST 2006}
}

Conference:
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  • A 10 cm diameter by 5 cm travel plunger tuner was developed for the PEP-II RF copper cavity system. The single cell cavity including the tuner is designed to operate up to 150 kW of dissipated RF power are specially placed 8.5 cm away from the inside wall of the cavity to avoid fundamental and higher order mode resonances. The spring fingers are made of dispersion-strengthened copper to accommodate relatively high heating. The design, alignment, testing and performance of the tuner is described.
  • A 10 cm diameter by 5 cm travel plunger tuner was developed for the PEP-II RF copper cavity system. The single cell cavity including the tuner is designed to operate up to 150 kW of dissipated RF power. Spring finger contacts to protect the bellows from RF power are specially placed 8.5 cm away from the inside wall of the cavity to avoid fundamental and higher order mode resonances. The spring fingers are made of dispersion-strengthened copper to accommodate relatively high heating. The design, alignment, testing and performance of the tuner is described.
  • A new class of collimators has been designed and built for the PEP-II collider which has opposing movable jaws. These collimators are designed to reduce backgrounds in the BaBar detector. They can support several kW of synchrotron radiation power striking the jaws or the impedance matching ramps. There are no longitudinal nor transverse higher-order-modes. The jaws and collimator body are made of Glidcop.
  • 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 theirmore » 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.« less
  • An asymmetric B Factory to be installed in the PEP tunnel has been under study at SLAC, LBL, and LLNL for several years [1-4]. A mature design for a 9 GeV x 3.1 GeV electron-positron collider with a design luminosity of 3 x 10{sup 33} cm{sup -2}s{sup -1} is presented. Solutions now exist for all the technical problems, including issues related to high currents (e.g., beam instabilities, feedback systems, vacuum chamber design, lifetime degradation, and radiation power dissipation in the interaction region) and those related to different energies of the beams (e.g., beam separation, beam-beam interaction, and detector requirements). Themore » status of this project, which is being proposed for funding in FY 1993, is discussed.« less