The second comissioning run of CLAS has finally yielded some recorded events of electrons scattering with tracks in the drift chambers. The picture shown is a real event with a clear track in Sector 6 (7 o'clock) of Region 2 and Region 3, matched with a Cerenkov hit and a Shower Counter response. The CLAS torus was energized; the cross indicates the target position.
During the past 2 weeks, the 7 o'clock sector was installed, and tension transferred on both this and the 5 o'clock sectors. No broken wires have been found. The 5 o'clock sector has been cabled up and is ready for the December test run.
After 4 1/2 years of work, the last of 6 Region 2 Drift Chambers was delivered to TJNAF yesterday and will be moved into Hall B today. A small ceremony will be held to celebrate this event, which will be attended by the director of Jefferson Lab, Dr. Hermann Grunder, and the president of ODU, Dr. Jim Koch. Installation of this chamber in the 7 o'clock sector will commence right after this ceremony.
See a more detailed coverage of this event .
The Region 2 wire chamber project has reached its half-way mark in terms of installed wire chambers. Three out ot six sectors (at 3 o'clock, 1 o'clock and 11 o'clock looking downstream) have been installed (including tension transfer) and tested. The fourth sector is being installed this week, and the last two will follow shortly.
One of the six Region 2 Sectors is the first Drift Chamber to be permanently installed in the CLAS detector. This sector was built at ODU, strung at CEBAF, and all electronics and HV boards were attached by ODU scientists. It was inserted in the 3 o'clock position in CLAS, attached to the cryostat, and tension was transferred from the exoskeleton to the spring attachments. (Before final installation, a few broken wires had to be removed which probably were weakened during stringing). Tension measurements show that all wire tensions are within specs, and all wires hold voltage (indicating no more broken wires or shorts). The next sector (Sector 1, strung at ODU) is ready for installation during the coming week, and the remaining sectors are on schedule for installation before fall.
During January 1996, the installation cart for the Region 2 Drift chambers was completed and tested in a first installation attempt with Prototype Sector 0. The picture shows the cart (yellow beams) and the chamber, which slides into CLAS on 2 rails. (Initially, the installation could not be completed because some design tolerances had been chosen too tight.) The design has meanwhile been modified and installation was completed. During this month, tension was transferred from the cross bars (exo-skeleton) to the attachment springs and several tension tests were conducted. The result is that the tension transfer scheme works and that the wire tensions stay within tolerances under varying load conditions (e.g., today the cryostat was let up to atmospheric pressure). The picture below shows a beam eye's view of the nearly installed chamber.
(Meanwhile, Sector 0 has been removed and returned to ODU, where it was disassembled, cleaned and rebuilt to serve as Sector 6).
The very first permanent wire for the Region 2 Drift Chambers was just strung at Old Dominion University. The first drift chamber sector (Sector 1) to be permanently installed in CLAS has been assembled (complete with trumpets and feedthrus), moved into the ODU clean room, and pretensioned. Stringing of the stereo superlayer has begun and will continue throughout the next weeks (with 2 shifts of stringers). Sector 1 is the second sector to be assembled at ODU; Sector 0, a full size prototype with about 1000 wires, has been moved out of the clean room and is being prepared for test insertion in the CLAS. The Region 2 Drift Chambers will be comprised of 6 sectors to be installed between the coils of the CLAS detector.