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 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 electron+photon 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