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Wittmer, W.

Paper Title Page
MOPAS058 A Parallel Controls Software Approach for PEP II: AIDA & Matlab Middle Layer 566
 
  • W. Wittmer, W. S. Colocho, G. R. White
    SLAC, Menlo Park, California
 
  Funding: US-DOE

The controls software in use at PEP II had originally been developed in the eighties. The functionality and maturity of the applications in that system have made it very successful in routine operation, but this same longevity and orientation toward fixed requirements, make it largely unsuitable for rapid machine development and ad-hoc online experimentation. A successful recent trend at light sources has been to use the so called MATLAB Middle Layer (MML). This package abstracts each underlying control system framework to which it is connected, such as Channel Access. We describe the middle layer implementation for PEP II and LCLS based on AIDA (described elsewhere in these proceedings), which is unusual in that it provides access to the high level functionality of the legacy control system, as well as to a very large assortment of useful data in addition to channel access read and control. The MML had to be adapted for the implementation at PEP II since colliders differ significantly from light sources by scale and symmetry of the lattice, and PEP II is the first collider at which such an implementation is being done.

 
TUPMS002 Successful Completion of the Femtosecond Slicing Upgrade at the ALS 1194
 
  • C. Steier, P. A. Heimann, S. Marks, D. Robin, R. W. Schoenlein, W. Wan
    LBNL, Berkeley, California
  • W. Wittmer
    SLAC, Menlo Park, California
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.

An upgraded femtosecond slicing facility has been commissioned successfully at the Advanced Light Source. In contrast to the original facility at the ALS which pioneered the concept, the new beamline uses an undulator (the first in-vacuum undulator at the ALS) as the radiator producing the user photon beam. To spatially separate the femtosecond slices in the radiator, a local vertical dispersion bump produced with 12 skew quadrupoles is used. The facility was successfully commissioned during the last 1.5 years and is now used in routine operation.

 
TUPAS068 A Transverse Beam Instability in the PEP-II HER Induced by Discharges in the Vacuum System 1811
 
  • U. Wienands, W. S. Colocho, S. DeBarger, F.-J. Decker, S. Ecklund, A. S. Fisher, J. D. Fox, A. Kulikov, A. Novokhatski, M. Stanek, M. K. Sullivan, W. Wittmer, D. Wright, G. Yocky
    SLAC, Menlo Park, California
 
  Funding: Work supported by US Dept. of Energy

During Run 5, PEP-II has been plagued by beam instabilities causing beam aborts due to radiation in the BaBar detector or due to fast beam loss triggering the dI/dt interlock. The latest of such instabilities occurred in the High Energy Ring (HER), severely curtailing the maximum beam current achievable during physics running. Techniques used in tracking down this instability included fast monitoring of background radiation, temperatures and vacuum pressure. In this way, the origin of the instability was localized and inspection of the vacuum system revealed several damaged bellows shields. Replacing these units significantly reduced the incident rate but did not eliminate it fully. After the end of the run, a number of damaged rf seals were found, possibly having caused the remaining incidents of instability. In this paper we will outline the steps taken to diagnose and remedy the issue and also compare the different signatures of vacuum-induced instabilities we have seen in both rings of PEP-II during the run.

 
THPAS068 Calculating IP Tuning Knobs for the PEP II High Energy Ring using Singular Value Decomposition, Response Matrices and an Adapted Moore Penrose Method 3642
 
  • W. Wittmer
    SLAC, Menlo Park, California
 
  Funding: US-DOE

The PEP II lattices are unique in their detector solenoid field compensation scheme by utilizing a set of skew quadrupoles in the IR region and the adjacent arcs left and right from the IP. Additionally the design orbit through this region is nonzero. This combined with the strong local coupling wave makes it very difficult to calculate IP tuning knobs which are orthogonal and closed. The usual approach results either in non-closure, not being orthogonal or the change in magnet strength being too big. To find a solution the set of tuning quads had to be extended which resulted having more degrees of freedom than constrains. To find the optimal set of quadrupoles which creates a linear, orthogonal and closed knob and simultaneously minimizing the changes in magnet strength, the method using Singular Value Decomposition, Response Matrices and an Adapted Moore Penrose Method had to be extended. The results of these simulations are discussed below and the results of first implementation in the machine are shown.

 
FRPMS084 Detection of Instumental Drifts in the PEP II LER BPM System 4261
 
  • W. Wittmer, A. S. Fisher, D. J. Martin, J. J. Sebek
    SLAC, Menlo Park, California
 
  Funding: US-DOE

During the last PEP-II run a major goal was to bring the Low-Energy Ring optics as close as possible to the design. Sudden artificial jumps of the orbit, which were regularly observed by a large number of BPMs during routine operation, were interfering with this effort. The source of the majority of these jumps had been traced to the filter-isolator boxes (FIBs) near the BPM buttons. A systematic approach to find and repair the failing units had been developed and implemented. Despite this effort, the instrumental orbit jumps never completely disappeared. To trace the source of this behavior a test setup, using a spare Bergoz MX-BPM processor (kindly provided by SPEAR III at SSRL) was connected in parallel to various PEP-II BPM processors. In the course of these measurements a slow instrumental orbit drift was found which was clearly not induced by a moving positron beam. Based on the size of the system and the limited time before the end of PEP II an accelerator improvement project was initiated to install BERGOZ BPM-MX processors close to all sextupoles.