FDC Weekly Meeting
Date: May 29, 2008
Participants: Daniel, Simon, Brian, Fernando, Kim, Chuck, Roger, Bill, Mark, Micah
Next Meeting: June 5, 2008 @ 1:30 p.m.
- Allflex has identified a distributor for the 5 micron Cu boards. Roger is beginning preparation of the cathode board PR. He still has some work to complete with laying out the gas holes defined by Bill. In doing this hole layout, he is making some minor modifications to the trace routing to improve clearances. Presently there are 24 gas holes located between the through holes. - Chuck has to include the gas holes in the G10 skin onto which the cathodes are mounted. He will begin this work over the next week. - Before the cathode board PR is submitted to Allflex, Fernando will be responsible for "blessing" the board layout (electrical issues) and Bill will be responsible for "blessing" the gas hole layout. - Our present design for the cathode includes a single grounding point through the 10th cathode daughter board. Recently Fernando has indicated that he is worried that a single connection might not be optimal and that we might want to add more connections about the perimeter of the cathode to keep all ground paths as short as possible. We are working to include a way to add ground connection points, possibly through copper tabs mounted in cut-outs beneath the cathode board. In this regard DSC questioned whether the 10th cathode daughter board was required. Fernando convinced us that for the prototype, we want to leave the 10th cathode daughter board in place as it may ultimately prove to be sufficient and he wants the flexibility to check this out. - Allflex indicated that they will not be able to provide a precision edge on the delivered boards. We decided then that we will request all boards be delivered in 19.5-in wide sheets (i.e. the full width of the board material possible from the material supplier) and we will trim the excess here. Obviously we must now come up with a process to cut the boards to provide a precision edge. This is highly desireable as our present construction technique butts the individual cathode board pieces up against each other. We then rely on this butt joint and the included sighting fiducials to ensure proper board-to-board alignment. If we do not have a precision edge and a butt joint, it makes the cathode construction procedure more complicated. Bill will look into procuring appropriate precision Starrett steel tooling for cutting the boards. - The board house will not pre-cut the holes for the through bolts or the gas holes. These holes will be added by us after the cathode boards are assembled and the frames included. We still have to finalize the tooling for this. Bill and Brian will work together to make a decision. We will have Allflex cut the center hole (for the prototype, we will request roughly an 8-mm diameter hole. For now, we will specify only a loose tolerance of 0.5 mm on this hole. This was felt to be good enough for the prototype boards. - We discussed how many sets of boards we should order. This depends on if there will be any potential problems with the boards upon arrival that would cause us to reject them, what we can expect in terms of problems in assembly that would lead to waste, how many boards we must set aside for testing (electrical and mechanical tests will be needed), and what the available budget for the cathode order is. Our initial guess is that we would require a minimum of 4 sets of boards of each type (2 micron Cu and 5 micron Cu). We will continue to ponder on this over the next week. DSC contacted Elke after the meeting to get her input on the available budget for this order. - Roger believes that the cathode board PR should be on Elke's desk by the end of next week. - Note from last week: The new cathode board material will be Espanex and not be Kapton. Both materials are polyimides, but we need to understand the different mechanical and electrical properties of the new materials. - Additional solder tests of the rigid-flex assembly to the cathode board mock up will proceed after Roger gets the hot air pencil from Fernando. This work will wait until the cathode board PR is completed. - Due to the height of the solder connection between the cathode board and the rigid flex assembly, we will have to revisit the design from the standpoint of adding clearance pockets on the surfaces that mate up against this solder region. Chuck will look into this and will make a report at our next meeting. - Bill completed the procurement requisition for the cathode board shipping/storage container and it was signed by Elke. We need to make a final decision on if the box should be shipped here or directly to Allflex. - Brian will modify his Lucite box design for storage of the completed cathode planes. The cathode planes can stack upon one another (unlike the strung wire frames). He will make some minor modifications to the existing box drawings and prepare the PR.
- Before the construction of the wire frames begins, we decided to have Greg Arnold's group solder on the HV capacitors (that just arrived) to the STBs and HVTBs. This work is in progress and will be completed by early next week. - The PR for the 5 ft x 5 ft granite table has been completed and submitted to Elke for signature. Note for now that we decided to order only one table although we will eventually need two of these tables. - Brian is working with Kim to complete the drawings for the aluminum jig plate to allow for clearance of the resistors and capacitors. This work is nearly done and then immediately submitted to Casey. Once this is submitted to the machine shop, they will modify the existing tooling plate and make a second plate for our second construction station. We discussed the need to update our frame construction process to allow this jig plate to have some guides to align it in proper position to ensure that it does not damage our frames or our circuit boards when it is lowered in place. Brian will begin to ponder this and believes that this is a solvable issue. - Brian has moved a storage cabinet into the clean tent in the EEL clean room. He will also shortly move in a work table. The granite table should be delivered in 2 to 3 weeks. The question is whether we want to put this table in the clean room tent or in EEL 126. We will figure this out shortly. - Brian and Bill will work to update our wire frame construction sequence document. Brian will provide a first draft to Bill who will work to polish it up. We would like to provide this to Casey so his group (and of course ours) can full understand the procedures. This work has not yet gotten underway. - Until the aluminum jig plate is ready and the granite table is delivered, Brian can still begin the wire frame construction process. We have hope that the frame construction will actually begin before the next FDC meeting.
- The first tensioned cathode was completed last week and it was noticed that it was pulling apart slightly at the seams between the cathode board pieces. As of today, no further changes have taken place and the board seems stable. Certainly the seam problems and the stretching of the Kapton that was noted indicated that the applied tension was too high. Brian will be working to purchase bare Kapton and then to develop a tensioning system that will allow for repeatable assembly parameters. Ultimately we would like the cathode construction procedure to be based on dialing in a specific tension into the cathode board during the frame mounting process. Brian will begin by ordering a roll of 48-in wide Kapton for this. The ultimate tension that we choose for the cathodes will be based on the allowable sagging (aka beer gut) on the cathode, the allowable distortion or stretching, and the stress on the seams. More to come on this as we make progress. - We will try to develop a cathode tension measuring system using our laser measurement head. The procedure will be to direct a puff of air at the center of the cathode and measure the amplitude fluctuation vs. time through the laser measurement system. Fitting this amplitude distribution will give us (hopefully) the fundamental frequency that we should be able to convert into the membrane tension. - We discussed again the need for providing additional ground connections to the cathode board. Brian indicated that he will be studying possible ideas when he makes connections to the ground plane that he will be attaching to the cathode prototype. This idea could be developed for the cathode ground attachment. - Our 12-GeV safety watchperson, Cindy Saban, has been documenting the cathode construction procedure and can provide a first draft of a procedures document. Bill and Brian can flesh this out and help to finalize the write up.
Test Frame Wire Winding
- IUCF provided a report of the results of the Phase 1 wire winding. Several of us are going over this report to generate a list of talking point for a phone conference with IUCF next week. Hopefully as a result of this phone meeting, IUCF will move to prepare a budget and schedule for the Phase 2 wire winding. DSC has prepared a discussion list for this meeting and circulated it to the relevant folks. He will pass on this list to IUCF. They indicated that they will continue to work on performing additional measurements on the two wire planes that they have to continue to try to resolve remaining issues with their wire winding system to ensure that they can meet our position and tension specifications. - DSC is working with Steve Christo to prepare a wire specification document for the tungsten and CuBe wires leading up to procurement. Steve is preparing a document for the Hall B chambers and we will most likely adopt this document for Hall D. DSC reviewed the existing Hall B documents to give folks a flavor of how these documents have been prepared in the past. We need to make decisions on what is required for the FDCs.
Stack Assembly Procedures
- DSC, Brian, Tim, and Bill will work to finalize the stack assembly construction document that has been prepared. This document should be in place before we get too far in the construction process.
Cathode Flatness Measurements
- Denny is continuing to study the flatness of our prototype cathodes. He is scanning the first Rohacell-backed prototype performing measurements at different angles to understand how the bulging depends on rotation angle. He has also gotten our second Rohacell-backed prototype and is now performing measurements. We would like to see how reproducible the cathode bulging is from cathode to cathode with our current construction process. Shortly Denny will get the tensioned cathode and perform some scans on its flatness. Results coming shortly. - We are planning on continued upgrades of the flatness measuring system to enable this to perform automated 2-D scans of the completed cathodes. Denny will be gathering some additional parts and pieces, including limit switches, etc. to start this upgrade. The summer student that Dave Lawrence had found to take this project over fell through, so he rounded up a master's student from CNU (Micah). This student will work to take the system over from Denny before he disappears on June 8 (Denny, not the student).
Cooling System Tests
- Denny reassembled the preamplifier cooling system in F117 and set the flow and temperature. After letting the system come to equilibrium, Fernando took over the system for the cooling tests of the preamplifier daughter boards. He will install temperature readout on the upstream and downstream sides of the coolant line feeding the preamplifier card. Results of these studies coming soon.
Gas System Design
- Vladislav (Slava) Razmyslovich is working on a preliminary layout of the gas handling system for the CDC and FDC in preparation for the upcoming systems review. We will sit down with him in a specialized meeting to review the design concepts when we get a chance.
- Kim needs to provide an instructional writeup for the Phase 1 and Phase 2 wire frame PCB component attachment. This is on her to-do list, but is not a high priority for now.
Cathode Board Discussion
- 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.
- Work continues on characterizing the preamp daughter boards to specify the ASIC dynamic range for both the FDC cathodes and wires. Simon is extracting from the data the amplitude distributions. He is making progress in acquiring spectra where noise-related events are not included (so that we do not bias our results). Once he has acquired the spectra for minimum ionizing particles, we need to convert this into the numbers required for the more heavily ionizing particles of interest. - Fernando has characterized the gain of the preamp/shaper/cable in GlueX-doc-1065. Simon will need to account for this gain in determining the dynamic range of the FDC anode and cathode ASICs. - Simon, Fernando, and DSC will prepare a write-up of the analysis results and assumptions that went into specifying the dynamic range numbers for the anodes and cathodes. - Brian will perform an optical scan of the cathode strip edges in one of our spare 2 micron Cu cathode planes. We want to make sure that there are no obvious systematic problems with the construction. He has found a x50 microscope to do this work.
- DSC has collected all of the available FDC subsystem design drawings and placed them on the FDC website. The URL is: http://www.jlab.org/Hall-D/detector/fdc/drawings.html. Folks should go through the drawings and let DSC know what drawings and/or categories are missing for a complete design set. - Also folks should send DSC the latest design drawings where there have been changes to keep this web site up-to-date through the review season.
- The FDC short-term work list has been posted on the FDC web site (see http://www.jlab.org/Hall-D/detector/fdc/). 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.