Beam position
(excerpt from SVT working group status report at collaboration meeting 7 March 1997)

BEAM POSITION STABILITY QUESTIONS
(Henryk Piekarz, Paul Derwent as consultant))

• beam size at IP (interaction point)
• expected resolution on impact parameter
• need precise alignment (position and direction) of beam relative to detector.
• CDF studies during last run show:
  store to store variations:
  • horizontal offset typical, up to possible
  • vertical offset typical, up to possible
  • angle variations typical
  change of position during the store:
  • horizontal and vertical typical,
  • angle typically too small to be measurable
• CDF: feedback beam control system, using measured beam position to set dipole corrector magnets so as to stabilize beam position and angle
  • range of variation determined by range of magnet powersupply ( A)
    beam direction: range
    IP position range .
  • tests performed by CDF and accelerator division in June 1995 showed:
    with 5 minute updates, beam position could be kept stable to within , and beam angle to within
  • test in Feb. 1996: beam moved vertically, horizontally without change elsewhere around ring
    can control beam position at DØ and BØ independently
• initial alignment at installation:
  Using BPM's and flying wires installed temporarily for this purpose, CDF plans to measure absolute beam location in collision hall very precisely during commissioning period at beginning of run
  goal: install track detector with axis aligned to better than , center to better than
  motorized support to allow position adjustment.