Hall C Beamline Upgrade Dave Gaskell Hall C Users Meeting January 19, 2008

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

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 electron+photon detection  chicane must be easily reconfigurable for 11 GeV operation (middle 2 dipoles closer to beamline)

Cartoon of Hall C Beamline Old – needs update

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)

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

Dipole Design