LANL, Los Alamos, New Mexico
TechSource, Santa Fe, New Mexico
Recent beam studies have focused on understanding the main sources and locations of electron clouds (EC) which drive the observed e-p instability at the PSR. New results using a recently developed electron diagnostic will be reported which demonstrate the important role of EC activity in quadrupole magnets, including definitive evidence that ~80% or more of the drift space EC signal is “seeded” by electrons ejected by ExB drifts from adjacent quadrupole magnets*. Other observations include distinctive brown colored tracking in various dipole and quadrupole vacuum chambers, which we hypothesize is caused by energetic electrons striking the wall during beam-induced multipacting. The tracking observations point to a simple and useful signature for regions of EC activity. Modeling of EC observations using a modified version of the POSINST** code shows general agreement on many features of the observations, given the large uncertainties in the distribution of seed electrons from beam loss which is a key input into the simulations. Progress will be reported on resolving the features not in agreement.
* R. Macek et al, PRSTAB, 11, 010101 (2008).
** M. T. F. Pivi and M. A. Furman, PRSTAB, 6, 034201 (2003).
LANL, Los Alamos, New Mexico
University of Tennessee, Knoxville, Tennessee
TRIUMF, Vancouver
ORNL, Oak Ridge, Tennessee
KEK, Ibaraki
At the 39th ICFA Advanced Beam Dynamics Workshop HB 2006 we reported on first results of a test of nanocrystalline diamond foils developed at ORNL under operational conditions at the Los Alamos Proton Storage Ring (PSR). We have continued these tests during the 2006 and 2007 run cycles and have been able to compare the diamond foils with the foils that are normally in use in PSR, which were originally developed by Sugai at KEK. We have gathered valuable information regarding foil lifetime, foil related beam loss and electron emission at the foil. Additional insight was gained under unusual beam conditions where the foils are subjected to higher temperatures. In the 2007 run cycle we also tested a Diamond-like-Carbon foil developed at TRIUMF. A Hybrid-Boron-Carbon foil, also developed by Sugai, is presently in use with the PSR production beam. We will summarize our experience with these different foil types and offer an outlook for future foil activities at PSR.