Hall C Beamline Upgrade

1
Hall C Beamline Upgrade

• Dave Gaskell
• Hall C Users Meeting
• January 19, 2008

2
Beamline upgrade motivation

• Short term motivation for Hall C beamline upgrade
  is the addition of a Compton polarimeter for
  QWeak (1 polarimetry!)
• Longer term goals
• 12 GeV experiments also desire Compton
  polarimeter (i.e. DIS Parity, 0.5 polarimetry)
  ? Compton must be 12 GeV compatible
• Beamline will also require modification for 12
  GeV operation
• ?Møller polarimeter as-is will only work up to
  6-7 GeV
• ?Fast/slow rasters also require some upgrades for
  12 GeV

3
Compton Chicane and Beamline Layout Constraints

• Compton requires insertion of 10-11 m dipole
  chicane
• Hall C Beamline must be overhauled
• Constraints/Requirements
• Fast raster must be at least 14.5 m from the Hall
  C pivot
• No quadrupoles between raster and target
• Polarized target chicane still useable
• Compton must work for QWeak (1.165 GeV) AND at 11
  GeV
• Compton must accommodate coincidence
  electronphoton detection ? chicane must be
  easily reconfigurable for 11 GeV operation
  (middle 2 dipoles closer to beamline)

4
Cartoon of Hall C Beamline
Old needs update
5
Beamline Features

• Dipoles increased from 1 m to 1.25 m to avoid
  high fields at 11 GeV
• Moller quads are part of the beamline
• Quadruplet before Compton chicane is used to
  prepare the beam for the interaction region
  (3C16, 3C17, 3C18, 3C19)
• Quadruplet after the Compton chicane used to
  prepare beam for target (3C20, 3C21, MQ1, MQ2)
• No combined optics
• Møller quads cannot be at measurement values
  while beam is on target
• Allowed combinations
• Compton target
• Compton Møller (high current questionable)

6
Beamline upgrade status

• Detailed design of Compton dipoles underway
  (Ernie Ihloff, MIT-Bates)
• CASA optics design concept complete
• Detailed layout by MEG group 95 complete (some
  iteration underway)
• To-do
• Complete layout (input from physics, survey and
  alignment)
• Begin procurement of pieces and parts (MIT-Bates
  and JLAB)
• Refurbish another big quad for Møller
• Identify power supplies for new magnets

7
Dipole Design