BigBite Wire-Chamber Status Report

Brandon Craver

University of Virginia

Hall A Collaboration Meeting

June 23, 2005

What do we build?• Three drift chambers:

– 1st and 3rd 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:

– 1st 140 cm x 35 cm– 2nd and 3rd 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

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

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

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

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

Measurement accuracy of about 25 microns

For wire spacing measurements a random uncertainty of about 50 microns (on difference)

Motor resolution 0.5 microns