Revision as of 10:22, 20 July 2012

July 19, 2012 FDC meeting

Agenda

1. Production Construction Tracking (Dave)
   • Fourth package status and spare wire frames (Lubomir, Vlad)
   • Third package preparation
   • Grounding scheme (Vlad)
2. Engineering [1], [2], [3], [4], [5] (Bill)
3. Electronics (Chris, Nick)
4. Gas system (Beni, Bill)
   • Pipe outgassing, gas detector aiging
   • Gas mixture (Lubomir)
5. Test set-up in 126 (Beni)
6. Other

Minutes

Participants: Bill, Dave, Eugene, Nick, Chris, Simon, Beni, Vlad, and Lubomir

Production

- The wire frames that are not installed yet are listed in the Construction Tracking (page 1) linked above. We need two wire frames to finish package #4. Frame #2 is ok but has been deadened with 6cm diameter which is for the first two packages. #28 can be used, initially the dark current was higher but went down to 350nA. #3 could be the other candidate but the current increased after two days of testing, will continue with the tests over the weekend.

- All these chambers show elevated dark current, maybe due to the same reason. On one of them (#6), on one HV sector (#1) we removed the current limiting resistors connected to the sense wires on the HV board: the dark current remain almost the same. We concluded that the current leakage is on the HV board, and more precisely on the positive HV trace. This trace has a section running on the back side which we suspect is causing the problem due to proximity to the Rohacell and the gold plated area on the back of the board. End of October 2011 we found that these traces are causing noise on the strips and we started coating them with conformal coating.

- Several options were considered: 1) to put #28 and #3 in the fourth package and finish it, 2)To try to fix two of the boards and use them in the fourth package, 3) to wait for the spare parts to build four new wire frames and use two of them in the fourth package. So far we excluded option #1. Since 2) and 3) will take time we decided to close the fourth package with four cells, take it out of the installation fixture and put there the first package for refurbishment (we did all this right after the meeting).

- One way to fix the trace (Bill) is to cut the wire frame from the back in the Rohacell region ( Casey has done this once), another way (Dave) is to bypass the trace on the back side and make cable connection on the top. We decided to go with the later, but for that we have to mill a niche below at the O-ring place for the wire and glue it there. Bill will work on the tooling for that.

- Third package: labels are put on the pre-amps and installed on the package. Vlad is working on the grounding positions. He marked the places for the grounding on several cells. At some places one ground strip will connect two or three cells. At one location per cell the grounding has to be split, at one place the big clip will be put and at another place, close to that, the other clip. Vlad is working on a measuring tool to record the angles of the grounding places, to be used by the techs.

Engineering update

- Bill submitted a PR for the four extra g10 wire frames. He got also an estimate for four thick (35mm) spacer rings (model drawings linked above), each $730, the only parts needed to proof the principle of the helium drift chamber. Since some engineering/drafting work is needed to submit the drawings, Eugene said we will do it later in the year when we start testing the spare package.

- Bill once more explained the cooling system using the schematics and model drawing also link above. Answering Beni's question, Bill: we have an interlock system using the flow switches and RTDs through the slow control. In the heat exchanger the pressure of the water will be less than the pressure of the Fluorinert; if the latter leaks it will be detected looking at the level of the Fluorinert tank.

Electronics update

- Contract for the four sets of PCBs was awarded to another company, Accurate Circuit Engineering, with a delivery date of 08/02.

Gas system update