FDC Weekly Meeting
Date: October 2, 2008
Participants: Daniel, Simon, Mark I., Roger, Eugene, Bill, Micah, Herun, Jim, Beni, Elke
Next Meeting: October 9, 2008 @ 1:30 p.m.
Full-Scale Prototype Updates
- Clean Room: * In order to move out of the shop into our own space, we have been doing work on the wire frame construction using the granite table in the clean room. Hence this space is not so clean at the moment. - Procurements: * Roger has not finished the design work for the cathode rigid-flex assemblies. The final number of these boards to be ordered (roughly 70) has yet to be finalized. * Elke asked us to prepare a spreadsheet listing all expenditures for the full-scale prototype. Kim has prepared a draft of this, but she still needs input from Brian, Roger, Lorelei, Simon, and anyone else who has ordered parts n' pieces. Please take a look at the existing document and provide feedback to Kim with your questions or comments. * Brian was working on the procurement of the sense and field wires for the full-scale prototype. DSC prepared two documents for our wires: Wire Specifications Document and Wire Testing Document. These documents have been passed on to the wire suppliers. More discussion on this when Brian returns. As of today, Elke received and signed the PR for the sense wire and it was not clear if the PR for the field wire has been passed on to her. - Storage: Kim has been amassing various and sundry FDC-related components in her area. She will bring them over to Simon for storage in F117 when she gets a chance. DSC will talk to her about creating and maintaining a database for the FDC components to try to keep ourselves organized. - Bill is working to put the local HV connectors selected by Fernando into the 3D CAD model and to detail how they will be attached (as they are quite massive). Bill will get back to this work when he has a chance. - It turns out the Greg Arnold's group will be able to acquire a programmable solder station that will allow temperature vs. time profiles to be set. This will be perfect for the Phase 2 component stuffing on the FDC circuit boards. DSC will talk to Kim about finalizing the assembly/cleaning document to include this information (Fernando will be able to provide Kim with the information that she needs).
- Mark got the nitrogen flowing through our cathode box using the dewar that Brian ordered. We should have just a trickle of gas going through and the box has been purged of air. - The W&M SEM group did some study of a small piece of our sample cathode board from Allflex. This sample was one that was stained with some sort of surface contamination. Their mass spectrometer analysis revealed only copper. This is at odds with what Fernando found, which is that this contamination appears to be non-conducting. Fernando is now working to do some additional measurements to resolve this apparent discrepancy. More soon. - DSC wants to delay the ordering of the remainder of the cathodes for at least a few months. We should work our way through the cathode R&D plan and work out all of the mechanical issues and final tension settings. If the required tension ultimately causes any distortions (i.e. stretching) of the cathodes, they we might want to scale the artwork in the next batch. We discussed this again and everyone is in agreement. Roger will contact our Allflex representative to touch base and give them full details on our plans. - Bill has not done any more work on the system to cut the cathode edges. More to come when he gets back to this. - Holes, holes, holes: * We are still pondering deeply whether we will include the central Kapton beam hole in the cathode boards and whether we will include the side gas holes. Bill is convinced that the perimeter gas holes in the frame are sufficient. * Eugene's preliminary FCAL rate studies show only a modest improvement if the Kapton in the central beam region is removed (of course in all scenarios there is no Cu in the beam area). These calculations are being followed up by Sasha (Eugene has been in contact with Sasha since the end of the Collaboration meeting). * Bill and Mark will do a series of test cuts with our cathode prototypes. Bill used a punch to make a roughly 1-in diameter hole in one of our cathodes (a picture of this cut can be seen on one of the slides in Simon's Collaboration Meeting talk for those interested). The cut looks good and the edges look good. A larger size punch (about 8 cm in diameter) has arrived from Allflex. Bill is already worried about how to apply the large forces needed to punch through the material. We will work on details when he gets back. * The nominal plan as of now is to set the cathode tension on the boards and then to add the central hole. - Please consult regularly the cathode R&D plan to better understand the order and the time assignments. Contact DSC with questions. - Cathode flatness measuring system: * The system assembly is now complete and Micah has hooked up the motors. He is running through system checks now and has identified a problematic limit switch on the vertical motion. A dry fit of one of our cathodes prototypes has been completed. We should not be too far away from doing a series of flatness measurements on our cathodes. - Brian and Bill should begin to layout a detailed outline for the cathode construction steps and circulate for feedback.
Wire Frame Construction
- We have run into a problem when making the G10/foam laminates for our wire boards. We had planned on using low-density 31HF Rohacell, and based on the R&D work completed by Brian, it seemed that this material would be satisfactory. It turns out that its thickness is not well enough controlled and it is far too soft and floppy to make it through the manufacturing process without compressing. Bill gave us an update talk on what he and Mark have learned over the past week or so. It is clear that 31HF will not work. There are other higher density, stiffer versions of Rohacell out there that could work (e.g. 110HF), but Bill will do some digging to find out more. Simon will also do some radiation length computations to understand what we can afford in terms of materials. Bill suggested using a solid 5-mm annular region behind the wire boards as a precision spacer. This could be too much of an impact for photon conversions. - The working specification on wire frame thickness is 5 mm +/- 2 mils (how's that for mixing units). This spec will not be achievable with a foam core. But given that our specification on the cathode flatness is about 4 mils, it makes so sense to have a much tighter tolerance on the wire frame thickness. Our short term hope for a solution is that by changing from 31HF Rohacell to 110HF Rohacell (or something like this) along with relaxing the thickness control specification, we may be able to produce a wire frame that will work for the FDC. - All wire frame circuit boards have had their modifications completed and are now back in our possession and ready for frame construction. - We are presently planning on borrowing an A-frame for EEL 126 for the wire frame construction (that Tim arranged). No other frames could be found in storage that we could claim. - The most recent modifications to our aluminum jig plates has been completed by the machine shop. - DSC will arrange for the wooden shipping box now at IUCF to be shipped back to us so we can use it for the full-scale prototype frames. - PCB updates: * Kim has finished the moving of the decoupling capacitors on the back side of the STBs. Fernando is now looking over the design drawings to make sure all is well. * The updated PCB drawings will be given over to Bill so that they can be put into the 3D model. * The PCBs for the FDC will need to be handled by all folks involved with more care. Many of the boards have sustained damage to the fragile lap ends. The damage is not severe enough to cause any construction worries, but handling procedures do need to be established and followed.
Full-Scale Prototype Wire Winding
- The Phase 2 winding paperwork has now been signed by the 12 GeV folks and passed on to our contracts people. The contract should be in place in the next 2 weeks. - IUCF will need us to make another one or two Moire pattern masks. Keith has provided details on what he would like. We will have Roger prepare the new drawing and take charge of putting together the PR.
- Bill has not yet finalized a choice of material. It looks like the best choice may be polypropylene. He would prefer nylon-6 due to its superior mechanical properties, but nylon-6 absorbs water like a sponge. One problem with polypropylene is that it is very difficult to epoxy to it. If this ring has o-rings on both sides, there is no problem here, but Bill needs to be able to attach the gas inlet and outlet tubings. He described a number of potential work arounds. Bill has also inquired about Noryl plastic. This has been blessed by the Hall B folks as fully chamber safe. - We will be working to make a mechanical prototype as soon as the design is finalized. - Bill has completed some studies of gas flow given his gas port design. He has tested the ability to move gas through the chamber given a worst case hurricane scenario. He has assumed a pressure change of 300 mb/hr, which is the worst ever pressure change seen at JLab. His design worked well under this condition.
Stack Assembly Procedures
- DSC, Brian, 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. - Bill has found some plastic threaded rods that could be used to compress the stack. We will be receiving some samples shortly and will carry out some loading tests.
Cooling System Tests
- Fernando is in the process of writing up the results from his cooling system studies. Stay tuned for the GlueX note.
Gas System Design
- Slava is working on a preliminary layout of the gas handling system for the CDC and FDC. He provided two options for the FDC system design that were essentially a basic version and a fancier version. Slava's design work was based on the original concept that Brian came up with long ago. Slava provided some drawings that DSC will review. We will then continue the design work as we have time.
- 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. - Kim has provided a draft of a procedures document for the Phase 1 and Phase 2 wire frame PCB component attachment. She has merged this document with Fernando's cleaning and handling document. The document is being finalized with some additional language on soldering iron temperature vs. time profiles.
- Simon and Fernando have completed their studies of the dynamic range for the anode and cathode ASIC dynamic range. The study results are posted as GlueX-doc-1070. Simon and Fernando are now working with the CDC folks to help them finish their studies. No word yet on when they will be done and ready for sending things off to Mitch. Stay tuned. - We still have the lingering issue of the problematic x-y plots from the 2-micron Cu cathodes. Simon will revisit this problem by taking some new pulser calibration data to see if this makes the apparent problem go away.
- Elke wants signed engineering drawings for the FDC prototype. These drawings will be finalized and signed for each component when we have completed the design and moved through the construction phase of the component for the full-scale prototype. Tim has a number system in place and can help oversee the completion and review of the drawings as we make progress.
- 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.