1. The present CEBAF Wien Spin Manipulator: Designed for 100kV beam and max rotation +/- 110 degrees Adaptation of SLAC design (how different?) X turn coil wrapped around iron pole pieces, field mapped to max current 10Amps Electrode power supplies+/- 15kV, max field gradient X MV/m Nickel field clamps at entrance and exit, with 1cm aperture Beam grows in X-dimension at angles > 50 degrees. Significant loss at A1/A2 “peanut” quads intended to focus beam in X-dimension, installed during G0 to improve transmission through A1/A2. Behavior of quads not so good. Namely, empirical determination of “good” quad settings, does not provide a meaningful relationship between Current and Wien Angle. Said differently: First quad doesn’t seem to do much, Second quad operates at same value regardless of (large) Wien angle. Note, despite focusing issues, we have operated at large Wien angles many times, and for extended periods of time. But obtaining good transmission takes tweaking. Emittance vs Wien angle constant (good) M. Poelker, J. Grames, Y. Wang, HAPPEx Collaboration Mtg., 7/23/08

2. HAPPEx needs another “slow sign flip”, to complement the insertable halfwave plate. OK The Wien filter approach seems reasonable, provided beam optics does not change considerably between the two states Does the present Wien Spin Manipulator meet our requirements? NO HAPPEx needs spin angles +45degrees and -135degrees. -135 degrees outside present Wien’s range (not enough B, magnet would run too hot), and… We suspect we would have very different beam optics for these two angles. The Wien quads do not adequately correct beam “blow up” at large angles (>+/- 50degrees).

3. Related: Space is tight in the 100kV beamline Beamline must be baked when vented: a difficult task We need a new Wien angle for our 200kV gun. Install summer 2009? We have a spare identical Wien at the Source Lab: Magnet has been mapped, need to shape the electrodes to match the B field

6. Solution#1 Extend the range of the present Wien Spin Manipulator More B: increase current from 10Amps to 13.5Amps (pick a value). Cooling issue? New magnet with more turns? More E: need 24kV differential. Our +/- 15kV power supplies are adequate. But have we operated at this high voltage? Do we suffer field emission or breakdown? Build better quad magnets, to ensure good transmission through apertures A1 and A2 at large Wien angle (i.e., same beam envelope) Beam should be centered in quads – not the case right now Pros/Cons/Issues Cheapest, quickest, easiest fix. Beamline stays the same. Must answer quad question: what’s wrong with our quads, can we make and mount new ones that actually focus in X at large angle? Modeling, would be nice to appreciate nature of today’s problems Use spare Wien to check operation at new E and B values, e.g., 13.5Amps, 30kV differential. Can install at Test Cave

7. Solution#2 Design/Build new and better Wien Spin Manipulator, +/-180 degree rotation at 100kV beam energy More B: longer Wien, more turns More E: longer Wien, electropolish and high pressure rinse our electrodes, to operate reliably at higher gradient Build better quad magnets, to ensure good transmission through apertures A1 and A2 at large Wien angle (i.e., same beam envelope across entire Wien operating range) Include appropriate space on beamline for these new quad magnets (i.e., not viewer crosses). Want quads centered on beam. The new Wien should also provide +/- 90 degree rotation at 200kV beam energy (i.e., our intended new gun voltage) Pros/Cons/Issues An essential part of 200kV gun program Need modeling expertise: new Wien, new quads and new beamline Takes a long time to design and build, need a long downtime to install

8. Solution#3 (Joe’s idea) Two Wien Spin Manipulators of present design, in series First Wien operates at 90 degrees, with a downstream counterwound solenoid pair to provide 180 degree flip. Solenoid pair rotates spin but provides the same focusing for the two states, therefore we should maintain same optics Second Wien provides additional rotation as dictated by machine energy conditions, for example HAPPEx needs +45 degree rotation. The slow flip requires only the First Wein be changed between +/-90, the Second Wein stays the same Still need new quads… Pros/Cons/Issues A clever idea, we have two Wien filters in-house Designing new solenoids likely easier than designing new Wien filter but still need modeling expertise: compare/contrast performance using one Wien, and to build new beamline. Is there enough room between gun and chopper for extra Wien? Not as much stuff to build, but need a long downtime to install