FDC Weekly Meeting
Date: October 29, 2009
Participants: Daniel, Beni, Simon, Fernando, Mark I., Stephen, Eugene
Next Meeting: November 5, 2009 @ 1:30 a.m.
General Construction Updates
- The single layer prototype assembly was completed and was studied in a 90/10 Ar/CO2 environment. Initially the chamber was laying in a horizontal position. We were expecting the chamber to plateau with a S-F voltage difference of 2000 to 2100 V. - The chamber was grounded in its nominal configuration using a series of temporary cathode grounding boards provided by Fernando. - We could not get above 1300 to 1800 V without sparking and large current draws. - We were concerned about gravitational sags of the cathodes, so we rotated the chamber to its nominal vertical orientation and rechecked. No changes were seen. - The chamber was opened up and tests of the wire frame with attached cathode were performed. We found two design problems of field bus vias arcing to sense solder pads. We potted with Hysol epoxy and were able to get the associated busses close to nominal voltage before the next problem revealed itself. - At still higher voltages we found HV breakdown between the sense wire HV resistors and the field wire solder pads. Recall that the resistors were mounted in Phase 1 stuffing before winding and were placed between the solder pads. Some are clearly too close. They were potted using Hysol epoxy. Gas is now flowing and HV checking will start later today. - We plan this week to start looking at signals from the wires and cathodes of the single layer configuration. If we don't get to it this week, this will certainly happen early next week. Stay tuned for news and developments. We would also like to look for HV breakdown and current draw problems with the 40/60 Ar-CO2 mixture before continuing on stack construction. - Fernando will add the problems discovered to the work list for Kim. - Single layer studies will continue for about a week before we return to stack construction. More news coming soon. - The preliminary FDC stack assembly document draft is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. The document will be fleshed out during the assembly procedure for the full-scale prototype.
Wire Frame Update
- Wire frame P1 is now under test in the single layer prototype. - Wire frame P4 has undergone a preliminary electrical QA check and has a few problems that need to be addressed. Wire frame P3 will then follow. - 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. We will include the information on the wire electroplating process shortly. - The parts of the jig to use for the wire electroplating operation are in our hands. They will be assembled as we find time.
- Progress updates: * All rigid-flex assemblies have gone through QA and been delivered for attachment to our cathodes. * Roger got the new rigid-flex order of a couple dozen pieces and has turned them over for soldering and then testing. They will be ready for us when we are ready for them. * Casey has been working on soldering rigid-flex assemblies to the first of our two cathode sandwiches. The soldering on one cathode is complete (electrical checks still to be done) and he has completed about half the soldering on the mated cathode. The soldering work will be completed on this cathode when we are done with the single layer checks. - The current draft of the cathode construction document is located at: /u/group/halld/Engineering/PRELIMINARY DOCUMENTS. - 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.
- Fernando has certified the lastest ASIC preamplifiers as meeting our design specifications. See GlueX-doc-1364 (The Gas-II/GPC-II GlueX Preamp Card Preliminary Test Results) for details and results. Fernando has one anode board and one cathode board available for the single layer tests.
- Bill raised an intriguing idea for simplified the rigid-flex and cathode design. We agreed it might be something that will simplify the design, reduce costs, and make the soldering work easier. As there were some issue to hash out, we decided to take this offline and continue the discussions. The basic idea Bill had was to fold the cathode board through the slot on the frame and to solder the flex assembly to it on the back side. This would eliminate cutting pockets into the back of the wire frame and allow us to increase the trace spacing on the cathode for soldering to the rigid-flex assembly. More to come.
Cosmic Ray Test Stand
- Beni has been investigating the wiggles seen in the reconstructed wire position from the cathodes. We focussed on log entry 419 in the FDC logbook. We believe that the periodicity seen is due to the algorithm Beni is using to determine the U and V centroids. He will talk to Simon and get his parametric form to see if this addresses the problems. No new news as of yet. Stay tuned.
- 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.