M' Sullivan and FJ Decker

1

Beam Current Limits at the end of Run 6

• M. Sullivan and F-J Decker
• for the
• PEP-II Team
• Machine Advisory Committee Review
• November 15-17, 2007

2
HER Beam current

• In the middle of August we developed a vacuum
  leak in the upstream HER beam line from the
  detector. The leak closed when the beam was lost.
• Limited the HER beam to 1775 mA
• Then to 1800 mA
• Gradually pumped out (virtual?) and was not a
  limit near the end of the run

3
HER beam current limit

• About the same time we lost the power supply for
  LER RF station 4-3 and had to take the power
  supply of HER RF station 4-6.
• Lowered the maximum possible HER beam current to
  2 A.
• At the end of August we were now running into
  record breaking territory and decided to not push
  too hard.
• At the very end of the run HER RF station 12-1
  had to be turned off due to vacuum problems and
  arcing
• This limited the HER beam current to 1.8 A

4
LER beam current

• Throughout August the LER beam current stayed at
  about 2.6 A
• We tried to push up the LER current in the latter
  part of August
• Luminosity kept going down as the LER current
  went up (Deckers talk)
• We got up to about 2.75 A
• Only briefly though and when we pushed the HER
  beam current up to 1.9 A
• Tried an RF MD to try for 3 A
• A fairly big jump in total beam current
• RF system needed more tuning and processing