Minutes-5-22-2008
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FDC Weekly Meeting
Date: May 22, 2008
Participants: Daniel, Simon, Brian, Fernando, Roger, Bill, Mark
Next Meeting: May 29, 2008 @ 1:30 p.m. (tentative)
Contents
- 1 Cathode Planning
- 2 Full-Scale Prototype
- 3 Cathode Prototyping
- 4 Test Frame Wire Winding
- 5 Stack Assembly Procedures
- 6 Cathode Flatness Measurements
- 7 Cooling System Tests
- 8 Gas System Design
- 9 Gas Volume Definition
- 10 STB/HVTB Discussion
- 11 Cathode Board Discussion
- 12 Small-Scale Prototype
- 13 Drawings
- 14 Work List
Cathode Planning
- Roger and the designers found that the cathode boards in the 3D model had all been included mirror reversed from reality. As the 3D model was used to define the placement of the daughter boards and external connections, a bit of scrambling had to be done to make updates to the cathode design. This took Roger a good chunk of time in the past week. In the future we should label all circuit board drawings with labels such as "viewed from the front" to avoid confusion and convention issues. - We still have not received word, either from Allflex or from the other distributor that Roger has found, on the availability of the 5 micron Cu/1 mil Kapton board material. We would like to figure this out soon so that it does not hold up the preparation and submission of the purchase requisition. - Roger has all of the information he needs to now begin preparation of the cathode board PR. We still need to make a final decision on how many sets of boards we will order. This decision will be based on how many cathodes we will be making for the full-scale prototype (nominally 6 cathodes), but also how many boards are needed for cathode R&D and how many are needed for electrical and mechanical tests. - Fernando pointed out that the new cathode board material will not be Kapton, but rather Espanex. Both materials are polyimides, but we need to understand the different mechanical properties of the new materials. - No progress has been made during the past week on additional solder tests of the rigid-flex assembly to the cathode board mock up. Roger will get the hot air pencil from Fernando and pass it on to Greg Arnold's group to complete the next phase of solder tests. - 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. As Roger announced last week, there is a new option for the preparation of the ends of the rigid-flex assemblies. The company can actually leave the last portion of the assembly without Kapton backing so the copper traces stick out past the end of the flex piece (like little fingers). This will enable easier soldering. We will have to investigate this further, but in any case, we will still have to modify the design to allow for proper clearance for the connection between the rigid-flex assembly and the cathode board. - Bill looked into ordering a storage box (called a pelican box) for the long-term cathode storage (before mounting). He could not find any large enough. He did find other similar boxes that are plenty large enough. The cost is about $1300. DSC will talk to Elke about this procurement. - Brian will modify his Lucite box design for storage of the completed cathode planes. This cathode planes can stack up on top of one another (unlike the strung wire frames). He will make some minor modifications to the existing box drawings and prepare the PR. - We discussed the holes in the cathodes. One question is whether to have the board house add the holes or try to do this ourselves after tensioning. We all felt that we should have the board house add the holes. Also, we questioned whether there will be a problem of having a center hole in the cathodes during the tensioning. As this is our nominal design, we will proceed with this approach until we find information that this won't work.
Full-Scale Prototype
- Kim reported that the HV capacitors for the STBs and HVTBs have arrived. She will find out how quickly Greg's group can solder these onto the circuit boards. If this work can happen quickly enough, we will hold up construction of the wire frames for the prototype. Keep in mind that nominally the HV capacitors are soldered onto the PCBs during Phase 1 stuffing. This work is better done now before any wire winding is done. - Outstanding procurements for the full-scale prototype: * The 2nd construction station PR has not been started. Brian has gotten a quote for a 5 ft by 5 ft granite table of about $4k. We would like to purchase two of these. One for the clean room and one for the frame preparation/assembly area. DSC will check with Elke on this procurement. * The rail attachment assembly drawings are now done and they have been passed off to FSU for construction. DSC has posted Bill's assembly drawings on the FDC web page. - The clean tent in the EEL clean room is now ready for us to move in. Brian will start by moving in a table and a cabinet. - Brian needs to provide Casey with a drawing for the modifications to the aluminum tooling plate used for our wire plane and cathode construction. Once he does, it will probably be at least 2 weeks before we get the plate back. The cost of a second plate will be on the order of $2 to 3k. - 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.
Cathode Prototyping
- Brian has completed a new cathode prototype. This time the cathode was prepared using the tensioning system. The cathode was tensioned until all wrinkles were pulled out. In performing this work, Brian measured that the cathode was stretched roughly uniformly in all directions by about 80 mil!. This version has a surface that is drum tight. - Many questions are still floating out there for our cathode design. * When the cathode is in its vertical position, what degree of bulging is acceptable? This feeds in to defining what tension is necessary to apply. * The cathode that Brian prepared was not exactly handled with kid gloves. It was wrinkled to all heck and had defects from the manufacturer. We all suspect that the cathodes from Allflex will not have the same defects as the dummy board cathodes from CCT. This coupled with better handling procedures on our part, will most certainly mean that less tension is necessary to pull out all of the wrinkles. * We all felt that we need to develop a tensioning system that is full reproducible. We need to be able to make all cathodes with the same applied tension. Therefore we would like to continue to develop the tensioning system to allow it to have this capability. One important piece of information that is not known is the tension in the cathode. Brian will try to setup the flatness system laser to measure the tension by blowing a puff of air at the surface and then reading back the frequency of oscillation. To this end, DSC suggested that we purchase a role of blank Kapton to act as a cathode dummy that will enable us to perform many quick tests without having to laminate the 3-piece dummy boards to make the cathodes. This will enable much more rapid turn-around times. * We need to have Denny measure the flatness of the new tensioned cathode. * We discussed modifications of the cathode artwork to include strain gauges in the side areas (at least for the prototype boards). This seemed like a pretty neat idea raised by Bill. We may be going too far with our cleverness as pointed out by Mark. * After only about 24 hours, it looks like the Kapton tape on the cathode seams is not keeping the cathode pieces locked in relative to each other (this is the so-called creep test). The applied tension is obviously very high. * If we can apply a fixed tension to the cathodes to fix the bulging and remove the wrinkles, and if this leads to a fixed and uniform stretching of the cathodes, we can always have the board house shrink the boards by a given magnification factor. - 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. DSC was wondering if the 10th cathode daughter board (for grounding the cathodes) is still required if we are still needing to make other ground connections to the cathodes. DSC will discuss this with Roger and Fernando. - 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
- The Phase 1 wire winding contract ended officially on Friday May 2. DSC has received a preliminary report on the status of the work, and this report will be improved by IUCF and updated over the next week. Basically they gave us what they had to fulfill the contract requirements, but it is not complete. - IUCF provided us with results from the tension measurements of the third plane that was wound. These results indicate that IUCF can meet our tension specification of 5%. Still awaiting final word on the tolerances for the wire placement accuracy. - 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 has provided measurements for the flatness of one of our cathode prototypes backed by 2-mm of Rohacell. The beer gut has been quantified at a 4-mm excursion. DSC thought that the beer gut was likely due to gravitational sag. Other thought differently. Mark suggested that we simply rotate the board by 180 deg and remeasure. This will be passed on to Denny. - Denny has now completed modifications of our 1D flatness measuring station into a 2D flatness measuring station. Some programming would be required (by some clever young person) to allow for an automated measurement system. This could happen this summer if manpower is available.
Cooling System Tests
- DSC and Denny moved the cooling system test equipment into F117. Denny will set it back up in there on Tuesday. Fernando will take over the measurements and study the cooling properties with a fully loaded preamp daughter board in place.
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.
Gas Volume Definition
- Bill has put some time into moving the design forward and the main points are given earlier in the minutes. Basically as the gas fills the volume like a liquid, he wants to include a series of holes in the cathode about the full perimeter of the board. This will require modification of the support frame (the G10 skin onto which the cathode is mounted) to allow for the gas to go through the G10 and the foam core. Note that any foam exposed to the gas must be sealed.
STB/HVTB Discussion
- 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.
Small-Scale Prototype
- 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. Simon will need to account for this gain in determining the required dynamic range of the FDC ASICs. - Simon, Fernando, and DSC will prepare a write-up of the analysis results and our analysis of the required dynamic range of the anodes and cathodes. Fernando will be in contact with Mitch Newcomer on our progress and plans. Our goal is to have a first draft of a report on this work by the end of next week. After the systems review, we will spend a few days to polish up the report and circulate it to a wider group for comments before passing the information on to Mitch. - 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 will work to find a x50 microscope to do this work.
Drawings
- 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.
Work List
- 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.