Notes and Action Items from Hall C Compton meeting: 4/28/2009 Attendees: Ron, Katherine, Butch, Ernie, Chris, and Dave Disclaimer: Since the tree pollen had my allergies in an uproar this week, these notes may be less accurate than usual. Please let me know if anything I say below is wrong or incomplete. 0. Although not explicitly discussed, I assume we will meet by phone again next Tuesday (May) at 1:30 pm. 1. Chris had issues with link to step file generated from Joyce's model. Dave needs to resend (done). 2. Some discussion of part numbers - where to put hyphens, etc. I believe the conclusion was that Ron will just handle whatever Chris generates (correct me if I'm wrong). 3. Chris is running out of drawing numbers - Ron will send email denoting different series of drawing numbers for 1. dipoles, 2. stands, 3. vacuum vessels. 4. Ernie asks about drop dead date for dipoles at JLab. We conclude that September 15 is acceptable, although may be tight for magnet measurement. 5. We spent most of the time looking at latest iteration of Chris' latest layout, which included supports for beam pipe as well as pump ports and a "keep out" for the interaction region. Comments during the meeting: a. It appears that the electron detector is on the wrong side of the chicane if the pumps shown in the figure are supposed to be on wall side. Chris and Ernie will hasj it out. In addition - Chris will add an arrow indicating beam direction on subsequent drawings. b. Region between dipoles 1 and 2 (and 3 and 4) now has 2 inch BPMs, valves, and horizontal correctors. In this layout, the 2 inch BPMs are closer to dipoles 1 and 4. From the point of view of the electron detector acceptance, it would be best to have any "small" aperture devices closer to dipole 3. About 70 cm beyond the edge of dipole 3, the maximum deflection of the scattered electron will be about 1 cm. This leaves about 7 mm clearance on one side at the exit of the 2 inch BPM. If that BPM is closer to the electron detector, the deflection grows to like 1 inch and will definitely conflict. c. New version has added BPMs to interaction region - valves are left outside interaction region. Dave note: Despite Ernie's concerns, it would be really nice to have the valves between dipoles 2 and 3. Because of the scattered electron deflection issues noted above, it would be best to keep the small aperture stuff to a minimum between dipoles 3 and 4. Alternatively, we could use larger valves in that region - but then the expense grows. d. New version has pumps at "beam pipe level" supported on stands off to the wall side of the beamline. Butch comments that the pumps can be closer to the beamline: near dipoles 2 and 3 thought there is some constraint due to the magnets themselves (and my desire to avoid possible conflict with laser table). e. Dave never sent the photon detector dimensions. The detector + photoube and base, with some room for HV and signal cable connections at the back should take up something like 27 inches of space (in the beam direction). The transverse size of the detector is 10 cm square. 6. Dave reviewed the global status (mostly so I'm clear on where we stand). a. Dipoles will be awarded shortly. b. Vacumm channel and magnet stand designs complete. c. Overall chicane design converging - nearly complete. To-do: a. Fabricate vacuum channels and magnet stands. b. Fabricate Joyce's optical cavity design. c. Design (or translate French design) for laser transport into and out of vacuum pipe. d. Complete electron detector design. -- ------------------------------------------------------ Dave Gaskell Jefferson Lab Suite 6 gaskelld@jlab.org 12000 Jefferson Ave. OFFICE:(757) 269-6092 Newport News, VA 23606 PAGER: (757) 584-6092