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in creator/contributor: "DeBarger, S."

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Measuring micron size beams in the SLC final focus

A pair of high resolution wire scanners have been built and installed in the SLC final focus. The final focus optics uses a set of de-magnifying telescopes, and an ideal location for a beam size monitor is at one of the magnified image points of the interaction point. The image point chosen for these scanners is in the middle of a large bend magnet. The design beam spots here are about 2 microns in the vertical and 20 microns in the horizontal plane. The scanners presented a number of design ch… more

Date: October 1, 1994

Creator: McCormick, D.; Ross, M. & DeBarger, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Dipole magnets for the SLAC 50 GeV A-Line upgrade

The SLAC A-Line is a transport system originally designed to deliver electron beams of up to 25 GeV to fixed target experiments in End Station A. To raise the beam energy capability of the A-Line to 52 GeV, the eight original bending magnets, plus four more of the same type, have been modified by reducing their gaps and adding trim windings to compensate for energy loss due to synchrotron radiation. In this paper the authors describe the modifications that have been completed, and they compare … more

Date: May 1, 1995

Creator: Erickson, R.; DeBarger, S.; Spencer, C.M. & Wolf, Z.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The PEP-II Lower Pressure HER Vacuum Chamber

This new vacuum chamber has been installed from 12 to 21 meters upstream of the BaBar detector in the PEP-II High Energy Ring (HER) to reduce lost particle backgrounds. The backgrounds from HER now dominate the backgrounds in the BaBar detector and the present vacuum pressure is 1 x 10{sup -9} Torr. The new chamber will increase the pumping significantly by adding 18 x 2000 l/s titanium sublimation pumps to the existing 5 x 440 l/s ion pumps, and is expected to reduce the pressure by about a fa… more

Date: March 13, 2006

Creator: DeBarger, S.; Metcalfe, S.; Seeman, J.; Sullivan, M.; Wienands, U. & Wright, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The PEP-II Movable Collimators

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 slide… more

Date: March 13, 2006

Creator: DeBarger, S.; Metcalfe, S.; Ng, C.; Porter, T. G.; Seeman, J.; Sullivan, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High-Current Effects in The PEP-II Storage Rings

High beam currents in PEP-II have been a challenge for vacuum system and ring components. For the {approx} 1 cm long bunches peak currents exceed 100 A and modest impedance can give rise to voltage spikes and discharges. During the last two runs, difficulties arose from rf seals at the 'flex flanges' in the HER. High temperatures were seen and the seals turned out to be severely damaged by discharges. In the LER, the horizontal stripline kickers of the bunch-by-bunch feedback system experiences… more

Date: June 19, 2009

Creator: Wienands, U.; Sullivan, M. K.; Akre, R.; Cheng, W.; Colocho, W.; DeBarger, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Tracking Down a Fast Instability in the PEP-II LER

During Run 5, the beam in the PEP-II Low Energy Ring (LER) became affected by a predominantly vertical instability with very fast growth rate of 10...60/ms and varying threshold. The coherent amplitude of the oscillation was limited to approx. 1 mm peak and would damp down over a few tens of turns, however, beam loss set in even as the amplitude signal damped, causing a beam abort. This led to the conclusion that the bunches were actually blowing up. The appearance of a 2{nu}{sub S} line in the… more

Date: May 18, 2007

Creator: Wienands, U.; Akre, R.; Curry, S.; DeBarger, S.; Decker, F. J.; Ecklund, S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ideas for a Future PEP-X Light Source

SLAC is developing a long-range plan to transfer the evolving scientific programs at SSRL from the SPEAR3 light source to a much higher performing synchrotron source -- PEP-X -- a new storage ring that would occupy the existing PEP-II tunnel and support two experimental halls, each containing 16 x-ray beam lines. Operating at 4.5 GeV and 1.5 A with a horizontal emittance of 0.14 nm-rad, reached using 90 m of damping wigglers, PEP-X would have an order of magnitude higher average brightness and … more

Date: November 2, 2011

Creator: Hettel, R.O.; Bane, K.L.F.; Bentson, L.D.; Bertsche, Kirk J.; Brennan, S.M.; Cai, Y. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department