1. BigBite Wire-Chamber Status Report Brandon Craver University of Virginia Hall A Collaboration Meeting June 23, 2005

2. What do we build? Three drift chambers: –1 st and 3 rd chambers 2u,2v,2x planes Resolution ~ 200 m –Middle chamber u, v and x planes Resolution ~1cm: to increase high rate and multi-track capabilities Active area: –1 st 140 cm x 35 cm –2 nd and 3 rd 200 x 50 cm Sensitive wire spacing: 1 cm Anode to Cathode spacing: 3 mm Cathode foil: 12 m Cu-plated mylar Plans to operate the chamber with Argon based or He based gas mixtures

5. Status of the Project Chamber construction is complete: Chambers 1 and 2: –At Jefferson lab now mounted on the BigBite stack –Have been tested extensively: Works very well; Holds HV well, very stable Dark current levels are very low Healthy signals around 1.6 kV. No dead wires or noisy wires. –Igor Rachek worked on electronics configuration: reduced noise pickup considerably. –Cabling in the final configuration underway: expect to finish soon. –Expect to move into the hall next week. –Parasitic high rate data taking during HAPPEX experiment

7. Status of the Project: Chamber 3 Being tested at UVa now: works well, with several noisy wires. Plan to fix next week Will be moved to Jefferson lab in July

8. Chamber tracking software Under development –Seamus Riordan with Bodo Reitz Has been tested with simulated data and cosmic data from the first chamber –Works well Beam data with two chambers will be extremely valuable for testing and refining tracking routines The chamber simulation, first developed at UVa is also being refined/tested

10. Summary and Outlook Chamber construction is almost complete Chambers work well Expect to finish the installation by the end of the summer Collect beam and cosmic data over the next months –Optimize operating parameters –Improve tracking routines

11. Measurement accuracy of about 25 microns For wire spacing measurements a random uncertainty of about 50 microns (on difference) Motor resolution 0.5 microns