FDC Weekly Meeting
Date: September 25, 2008
Participants: Daniel, Simon, Kim, Eugene, Micah, Herun, Jim, Beni, Chuck
Next Meeting: October 2, 2008 @ 1:30 p.m.
- Simon has posted his FDC talk (GlueX-doc-1102) from the GlueX Collaboration meeting last week. He reported that there were no additional questions that came up that we did not hear during his talk. - The FDC DOE report on the wire frame fabrication has been completed and sent off to DOE after review by the JLab 12 GeV folks. - We discussed briefly the issuing of prepared signed engineering drawings. DSC will talk more about this with Elke and Tim shortly.
Full-Scale Prototype Updates
- Clean Room: * We all met out at the clean room recently and went over the procedures for entering into and leaving the tent. The procedures have also been posted on the tent. Brian is still working to gather a few items (sticky mats, shoe covers). * We spent a day cleaning the heck out of the area that our clean tent hovers over. The clean tent was blessed as ready for operation before we looked at the cathode order. The clean is up and will remained under power for the foreseeable future (unless someone unplugs us again and doesn't tell us). - Procurements: * Roger has not finished the design work for the cathode rigid-flex assemblies. He is now back at work and he will have to update us on progress. 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 started to prepare this including all of her procurements (including those through Fernando) and those of Bill. She still needs input from Brian, Roger, Lorelei, Simon, and anyone else who has order parts n' pieces. We will post a draft of this spreadsheet in an accessible place shortly. * Brian is working on the procurement of the sense and field wires for the full-scale prototype. DSC has 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. These documents are posted on the FDC procedures web page. As of today, Elke has 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. - 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). As Bill is away this week, no progress has been made on this. - 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. DSC will talk things over with Fernando who is home sick.
- Our first order of 2 full sets of 2 micron Cu boards and 2 full sets of 5 micron Cu boards arrived just after our last FDC meeting. The boards arrived in Bill's delivery case and looked qualitatively better compared to the first sample board received. The packaging was excellent and we put the boards onto the granite table in our clean tent and did a visual inspection. See Simon's collaboration meeting talk for some photos and some data results. Simon, Herun, and Fernando completed our full suite of electrical checkout and no problems were found with any of the boards. We were impressed. Kim contact the Allflex representative with the news. After testing, the boards were put back into the storage box. Brian had already modified the box with gas fittings and a bubbler and was awaiting the nitrogen dewar. No work yet on if this has been hooked up. DSC will follow up. - 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. Stay tuned. - 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: * All order parts n' pieces have arrived. Assembly of the measurement station is essentially done and Micah has already started hooking things up. Be warned, the granite table used as backing for the cathodes is fragile (see FDC logbook) (haha). Anyway, Micah will dry fit a cathode board onto this system and do some basic electrical and control checks and then work his way into the measurements. Results to come soon. - Eugene has posted GlueX-doc-1090 containing all details regarding his studies on the cathode tension measurements and the allowed flatness variations. He believes that if we can keep the flatness within 200 microns, we will be in good shape. - Brian and Bill should begin to layout a detailed outline for the cathode construction steps and circulate for feedback.
Wire Frame Construction
- The frame that was used for our wire tension load test (which is discussed in the FDC TDR) has been modified to include the pockets for the rigid-flex assemblies and the bolt holes. It was machined to the nominal I.D. and O.D. of our wire frames. The foam core and the G10 skin were removed to an I.D. of 1032 mm to account for the problem with the HV decoupling capacitor placement. The load tests have been redone (see Simon's Collaboration Meeting talk for data) and the frame passed with beautiful results that agree with the limited FEA calculations that Bill completed. Thumbs up for wire frame construction. - A preliminary version of our wire frame construction plan by Bill has been placed on the FDC web page. It will be updated as we work through the assembly procedure. - Brian and Mark are now working on completing construction of the G10/foam laminates that will form the wire frames. We will be winding four frames and will use the solder sample PC boards to make a fifth frame to test out our procedures and to do dry fits of pieces and parts. So far three laminates have been made and machined and a fourth will be ready for machining shortly. It appears that the compression force used on the first laminate to hold the machining jig in place actually squashed the foam (see FDC logbook). Mark and the JLab shop folks are currently doing a series of measurements to figure out by how much. Bill also raised the worry that he suspects the variability of the thickness on our 3.4-mm thick foam sheets might be more than we want. As this thickness is crucial to define one of the half-gaps in each drift chamber layer, we have to worry about this. It may be that we can measure the foam thickness and only select those sheets that in spec. Stay tuned. Anyway, the shop folks noticed the compression issue and decreased the compression force holding down the machining jig and the next two wire frame laminates do not have as big of an apparent problem as the first. Mark will measure the thickness of these frame pieces as well. - During the machinining on the first laminate, there was a problem with some local delamination of the G10 from the foam as the first cut-out for the rigid-flex assembly was being made. This had to do will too slow of a speed on the mill. An optimal setting was quickly determined after this. - After the meeting the JLab shop folks did some precision measurements on the foam thickness and it is easily within 2 mils, in fact it looks to be within 1 mil. The G10 skin material thickness is also accurate to better than a mil. However, the laminate thickness varies by up to 20 mils around the circumference. Thus the issue is with controlling the epoxy layer thickness. We will deal with the problem on Monday when Bill returns. - The wire frame laminate construction has been going on in the JLab machine shop. This work will be move to the clean tent to occupy the space that we have clamored for but is now sitting vacant! - Bill has worked with the JLab machine shop to complete the through-hole enlargement in all of our circuit boards. The boards have been passed off to Greg Arnold's group for two changes: 1). the bleed resistors on the STBs will be changed from 10k to 1M, and 2). remove the capacitors on the solder sample HVTBs. - 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 next step in the process of making the wire frames is to machine some additional holes in our aluminum jig plate to allow for clearance of the assembly pins. This work should be submitted to the machine shop early next week. If all goes according to plan, we should be laminating the circuit boards next week into rings, followed by lamination of the PCBs to the G10/foam laminates shortly thereafter. We expect to be done with the wire frame construction for the full-scale prototype by the end of the second week in October. - 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
- We had a teleconference with IUCF before the Collaboration meeting and agreed on the basic parameters (time scale and budget) for the Phase 2 wire winding. DSC and Elke have completed the sole source document and the statement of work document. They have been passed onto the 12 GeV management for signature and then they will be passed on to our contracts folks. - IUCF will need us to make another one or two Moire pattern masks. DSC has contacted IUCF to have them tell us the details on what they want.
- 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.
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. - 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.
- We discussed a bit about making sure all relevant design features of the FDC are in the full CAD model. Tim will have Slava work to put in the capacitors and resistors on the wire frame PCBs into the model.
- 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.