Difference between revisions of "Minutes-7-19-2012"

From GlueXWiki
Jump to: navigation, search
(→‎Agenda)
Line 18: Line 18:
 
= Minutes =
 
= Minutes =
  
−
Participants: Bill, Dave, Eugene, Mark, Nick, Simon, Vlad, and Lubomir
+
Participants: Bill, Dave, Eugene, Nick, Chris, Simon, Beni, Vlad, and Lubomir
  
 
== Production ==
 
== Production ==
  
−
- Results of the tests of the last three cells of the fourth package: top cell #1 (wire frame #18) working fine, cell #2 (wire frame #28) and cell #3 (wire frame #27) had a problem, high dark currents, about 400-500nA for frame #28 and 1100-1300nA for #27. Both cells held HV for a long time (3-4 days) and all channels are OK.
+
- 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.
−
Still, we were not comfortable with that and disassembled the three cells on Monday. It turned out that the HV caps on all wire frames were indeed replaced, just Anatoly didn't have record for #28. We can't find what was different in the production of the last two wire frames. On Wednesday we installed back the third cell but with the working wire frame #18, that was before on the top.
+
  
−
- From Monday till Wednesday we were testing #27 separately between the two Lexan sheets: the high current didn't change even after cleaning, or removing HV cap on the HV PCBs. There's no current through the field HV and looks like the current goes on the HV PCBs to ground. Most likely humidity plays a role here. We used a lamp for several hours to heat/dry the PCB; the current goes up by a factor of two almost immediately after turning it on. On Wednesday we gave up with #27 and started testing wire frame #28, the current there is much lower, ~400nA. The plan is to try to clean it and if it's stable we will use it in the second cell. As for #27, the plan for now is to leave it as a spare and use one of the spare frames (#6) in the fourth package.
+
- 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.  
  
−
- Spare wire frame #6: Anatoly was able to remove the HV caps and clean the Humiseal (without using aceton); there's die in the Humiseal which makes it very easy to see it with UV light. Next, we will test the wire frame between the Lexan sheets, first, without HV caps. Since we are not sure if we can fix #27, Bill will ask "Vision Machine" for quotation of four g10 wire frames. If we need them, we have to submit PR before the end of July.
+
- 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 natch
  
 
- Third package: 10 ground clips (first article) finally arrived and we tested them on the package. They have a bite of ~12.5mm and we asked for 11mm, that's why we have to bend them a little, but other than that they worked fine. Casey put already them on one cell and is looking for a way to bend them in a standard way, using a press. This is not a big deal and we decided to go ahead with the production of the rest of the clips, instead of waiting another month. Tina and Dave put the labels on all the pre-amps for the third package.  
 
- Third package: 10 ground clips (first article) finally arrived and we tested them on the package. They have a bite of ~12.5mm and we asked for 11mm, that's why we have to bend them a little, but other than that they worked fine. Casey put already them on one cell and is looking for a way to bend them in a standard way, using a press. This is not a big deal and we decided to go ahead with the production of the rest of the clips, instead of waiting another month. Tina and Dave put the labels on all the pre-amps for the third package.  

Revision as of 18:50, 19 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)
  5. Test set-up in 126 (Beni)
  6. Other


Retrieved from "https://halldweb.jlab.org/wiki/index.php?title=Minutes-7-19-2012&oldid=38828"