Minutes-9-17-2009
From GlueXWiki
FDC Weekly Meeting
Date: September 17, 2009
Participants: Daniel, Bill, Stephen, Mark I., Simon, Fernando, Beni, Eugene, Brian, Roger, Glenn
Next Meeting: September 24, 2009 @ 1:30 p.m.
Contents
Manpower Update
- Manpower will be thinning out soon. Stephen Burnett is going back to Hall B at the end of this week. His support is very much appreciated. Brian Kross will be off the project for the month of October. We will have to rally available manpower to finish stack construction. Stay tuned.
General Construction Updates
- The assembly jig for detector stack construction has been put together and a frame was dry fitted onto the pins. The frame did not go onto the pins until they were reamed out, but the fit was still a bit tight. We will investigate going to fewer pins or even taking a few mils off the pins if necessary. It was decided that we would wait until stack assembly before making the final decision. Bill does not believe there are any issues here. - Bill has been working on the FDC stack assembly document. He has made a draft availale at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. Folks should look it over and provide feedback. The document will be fleshed out during the assembly procedure for the full-scale prototype. - Brian will check into whether we can get a sample size order of indium (lower temperature) solder paste for the rigid-flex assemblies. If we cannot, we will proceed with using convention tungsten solder.
Wire Frame Update I
- Wire frame P1 status: * Nominal test configuration: connect all grounds together and apply 1 kV to the bus under investigation. * P1 is the best frame with the worst bus (a sense bus) drawing below 200 nA of current. The other 11 busses are well below 50 nA. * We have inspected the surface of P1 on the top of the HVTB and STB and on the back side of the STB to look for evidence of solder flux or other problems. The board looked very clean under the microscope. * The leakage is between sense and ground and the problem has been localized to the STB. Disconnecting the ground on the STB causes the current to drop by a factor of 3 to 4. * After letting the frame sit in the dry room for several days, the current on the problematic bus dropped to below 50 nA. The other busses were below 20 nA. So, humidity is an issue or at least is making the problem worse. * We coated the blocking capacitors on the STB with Humaseal and took P1 out of the dry tent. The current were back to their original values. Applying hot air on the HVTB did not change the currents. Applying hot air to the STB side caused the currents to creep up by 20 to 30% after 1 minute. When the hot air was removed, the currents came back down. - Wire frame P3 status: * P3 has the worse current draw problems, with several sense busses about 1 microA in the nominal room environment (~45% humidity). After several days in the dry tent, all currents were below 50 to 60 nA. * The components on P3 were fully sealed with Humaseal (HVTB filters and STB blocking capacitors) when the frame was dry. Upon bringing the frame back into the room and letting it sit overnight, all currents had returned to their original values. * The two highest current draw busses were allowed to sit at voltage and quickly came down from levels about 1 microA to several hundred nA and then leveled off. * The leakage was always from sense to ground. All field bus currents were fine. The leakage issue was always on the STB side. When disconnecting the STB ground, the currents dropped by a factor of 3 to 4. On reconnecting the ground we would trip the supply off regardless of the trip scale and there was a spark in one instance. Something is charging up. - Wire frame P4 status: * P4 has current draw problems similar to P3, maybe a slight bit better. We only have current draw information at normal room humidity and we have let the board sit in the dry tent for a while. We will inspect the board and make current measurements this week. - Our next test is to make the active area gas tight and leave the rim of the frame in air and study the current draws again.
Wire Frame Update II
- Rich's work from this summer on the wire frames has been prepared as a GlueX document (#1327) entitled "Procedures for Inspecting and Troubleshooting of the Wire Frames for the Full-Scale FDC Prototype". - In the full-scale prototype, there was a design problem with the circuit boards so the wire frames will be laminated to their neighboring cathode planes to give a gas seal. We will move forward with this work as we certify each wire frame as ready. - We need to have a dedicated meeting to design what the schedule for work on the Phase 3 wire winding will be. The highest priority for work scheduling will be doing work on upgrades of the wire winding facility. This includes a better strongback design, the design and construction of precision combs, modification to the wire winding table, and a list of other items with the system. Stay tuned, more to come. - The wire frame construction document is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. He will include the information on the wire electroplating process as well. - The parts of the jig to use for the wire electroplating operation are in our hands. They will be assembled as we find time. - Brian received the SEM scans for our wire from the W&M folks. He will generate a final QA report with photos and test results for all wires when he gets a chance.
Cathode Update
- Progress updates: * The mechanical work on all cathodes is complete. The last thing to do is to connect the grounds on the individual panels on each cathode. * Stephen has been working on the rigid-flex assembly QA checkout. There appear to be problems with connectivity on about 20 boards. * Mark S. has been working with Roger, Fernando, and Bill to finalize the rigid-flex assembly soldering procedure. This is converging but we still have a few more tests to complete before considering solder work on the "real" cathodes. - The current draft of the cathode construction document is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. - Roger is pressing the Japanese company that has agreed to provide our board material. They have agreed to manufacture the material but are being non-committal on when it can be ready. Procurement is involved in trying to get this order completed. - Roger needs to prepare a document for QA/stuffing/cleaning for the cathode boards and a similar document for the cathode daughter boards and ground boards.
Cooling System Tests
- Fernando is in the process of writing up the results from his cooling system studies. Stay tuned for the GlueX note. He indicated that he is back to work on this document and it should be done shortly.
Cosmic Ray Test Stand
- Beni is continuing work to setup the cosmic ray telescope and test system in EEL 126. He is making progress on reducing the noise and is working to reproduce the data from the small-scale prototype that Simon had last year. The latest plots are in the FDC electronic logbook at: http://www.jlab.org/Hall-D/detector/fdclog/ - We still have some mysterious behavior with the small-scale prototype response with wiggles in the X vs. Y distributions that need to be understood. Beni has reproduced this problem qualitatively and we discussed some possible causes, but more work needs to be done. Beni has yet to complete a pulser calibration run. - Beni has started a bench test plan for the full-scale prototype and is presently working on it after incorporating feedback. The current information is contained on the FDC wiki page under the heading "FDC test cosmic ray test stand". - The parts for the support/rotation of the full-scale prototype in the cosmic ray stand will be assembled as we have time.
Work List
- The FDC short-term work list has been posted on the FDC web site. This is continually being updated and DSC welcomes any feedback or comments from the group.
Minutes prepared by Daniel. Send any comments or corrections along.