1. Mac Mestayer DC12 Status: as of Feb., 2008 Decide on endplate, feedthrough, wire material –guidance from small prototype chambers mainly electrical stand-off and noise issues Decide on frame designs –guidance from Reg. 2 prototype –constructability and accuracy of pre-bowed endplates Large prototype tests –improve procedures, look for unknown problems Proceed with drawings, vendor qualification, … Feb. 21, 2008CLAS12 Drift Chambers: Status Report

2. Mac Mestayer Prototype tests Wire-test chamber at ODU, Idaho St. –smaller diameter field wire ok; no extra noise –metal-tipped feedthroughs less noisy than all plastic Full-scale Reg. 1 prototype –long wires ok; small electrostatic deflections –large temperature variation of wire tensions –many procedures to fine-tune –small modifications to electronics boards –no new problems May. 29, 2008CLAS12 Drift Chambers: Status Report

3. Mac Mestayer Decide on endplate, feedthrough and wires Endplate material  aluminum (reg. 1): minimize dead area  G10 (reg. 2): no eddy current if torus quenches  steel-foam (reg. 3): very stiff structure Feedthrough material  glass-loaded Noryl with metal “trumpet” inserts Wire choices  30  m W, 80  m Cu-Be, 140  m Cu-Be for s, g, g  less wire tension, thinner endplates May 29, 2008CLAS12 Drift Chambers: Status Report

4. Mac Mestayer Decide on frame designs  pre-bowed endplate-in-a-frame May. 29, 2008CLAS12 Drift Chambers: Status Report

5. Mac Mestayer Status: drawings, vendor qualifications drawings for Reg. 2 ~ 90% done Reg. 2 endplate prototype – this summer procurement strategy: –feedthroughs: main vendor can help choose “inserts” –wire: specifications known, ready for procurement –endplates/frames: reg. 1&2 – ready at end of summer –assembly fixtures: ready at end of summer –Reg. 3: stay with standard “steel/foam” design? (or go to a “reg2-type” design?) May. 29, 2008CLAS12 Drift Chambers: Status Report