FDC Weekly Meeting
Date: August 28, 2008
Participants: Daniel, Simon, Brian, Fernando, Eugene, Bill, Micah, Herun, Jim, Beni
Next Meeting: September 4, 2008 @ 1:30 p.m.
- 1 Readiness Review
- 2 Full-Scale Prototype Updates
- 3 Cathode Planning
- 4 Cathode R&D
- 5 Machine Shop Work
- 6 Wire Frame Construction
- 7 Test Frame Wire Winding
- 8 Spacer Design
- 9 Stack Assembly Procedures
- 10 Cooling System Tests
- 11 Gas System Design
- 12 Documentation
- 13 Small-Scale Prototype
- 14 CAD Model
- 15 Work List
- Feedback from the readiness review: - The presentations were very well prepared and a valuable exercise. Here are the notes that I took during the presentation yesterday. At what point are all the drawings going to be signed off? - Dan: - Main purpose of large scale prototype 1. mechanical issues, including physical test of handling, tolerances 2. signal/noise in electronics (esp. increased lengths of cathodes) 3. edge effects 4. beam test/magnetic field study - Schedule for wire planes and integration with cathode construction? work on impact for construction schedule - Bill: 1. verify that frames remain in their elastic region all during fabrication and assembly. Develop tolerances based on prototype. 2. major cost is the machining of o-rings 1 day/plane. 3. eliminate o-ring on one side of cathodes? 4. tolerances on thickness needs to be reviewed. In particular nominal thickness of CH2 is 3/16 = 0.48 cm (instead of 0.5 cm) - How is this going to work for the prototype? 5. Gas flow - check procedures for leaks; calculations for variation of atmospheric pressure (overpressure in chamber); check use of bubblers. 6. size of inner hole - Brian: 1. test cutting center hole in cathode planes 2. check requirements for size of hole required; possible need to strengthen area around hole 3. check alignment of ring over cathode board after tensioning 4. Fernando: develop (backup) cleaning procedures for cathodes; soldering tests using samples - Bill: 1. testing layer by layer during assembly? 2. check gas tightness one layer at a time 3. precision of pins during assembly to prevent jamming?; one precision pin + elliptical? 4. check alignment procedure, especially relative to stretched cathode planes. 5. external fiducials - need a third one? 6. survey prototype? 7. gas pressure during hurricanes; can the chamber gas get out fast enough
Full-Scale Prototype Updates
- Brian is working to put our clean room/tent together. He has gathered sticky mats, gowns, hats, gloves, shoe covers, cleaning equipment, trash cans, etc.. He has ordered a few things such as sticky rollers to clean the area that will arrive soon. He will get a bench and a storage closet soon. Brian is now laying out a procedure for entering into and leaving the clean space that we will all have to follow. After this procedure is finalized, we will all meet at the clean tent have a walkthrough of everything. As of now, we will be following full clean room procedures in the tent. - There have been a series of recent procurements for the FDC that were not fully expected. Please, if you are aware of procurements needed for this system, please pass these on to DSC and Elke so that there are as few surprises as possible given the current funding situation. This is worth spending a few minutes thinking about. What will need to be bought before now and the end of the year? - Roger is still working to finish the design work for the cathode rigid-flex assemblies. He still has several days of design work to do and hopes to put the order together in the next several weeks. We will be ordering enough of these assemblies to outfit the entire full-scale prototype. - Kim has completed the PR for the signal cable connectors and for the manufacture of the LV cables. Elke has already signed the PR. - 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. - Fernando is considering now how we will make the connections from the HVTBs to the power supplies. He has identified a connector that will connect to the baby cables soldered to the HVTB and the cables that go to the power supply. Bill will look into where this connector can be placed on the outside of the FDC packages. If the connectors are too large, we can follow up on other options. More to come. - Brian identified a group that can do our SEM wire studies. Brian will bring them our already prepared sample from our earlier SEM tests and see if they are content with our slide. This group also has a super high power optical microscope that we can use that might allow us to bypass some of the planned SEM studies. More to come. Note that our new SEM contact can be used to study a sample of the cathode board that we received from Allflex.
- Allflex started to work to prepare our boards. They made one board with 2 microns of Cu and immediately had some questions. They sent us the board and we inspected it in the clean tent with all hands on deck. We were reasonably pleased with the quality and appearance of the board, but it could have been better. The entire board seemed to have some sort of texture and there were a number of black discolorations on the board surface. The textured pattern mostly pulled out with minimal tension. The black discolorations were some non-conducting material, probably solution from the lithography process. Fernando and Simon did a complete QA checkout on the board (resistance and capacitance measurements and short checking). The board met all of our specifications. Good news. - After the board inspection, we had a conference call with Allflex and relayed to them our findings and what we would like to see improved. Allflex indicated that they have some steps that will try to improve the board quality. It is not clear when the board order will arrive. However, we did communicate with the some new instructions. First, no hole in the center of the middle cathode board (this was good news for Allflex); second, instructions on where to place the side board artwork on the Kapton piece. - Fernando will arrange to take a sample of the discolored section of the board to do an SEM test on it to find out more about what the substance is composed of. - We have not yet devised methods for handling the boards when they arrive from Allflex. This will have to be developed once the boards arrive. Presently we are planning on doing a battery of QA checks on all boards in the first order. - Bill has not done any more work on the system to cut the cathode edges. More to come when he gets back to this. - We have not gotten any further in devising a test to cut the central hole out of the cathode boards or deciding when to do the cutting, i.e. before or after tensioning. Elke did a stab test with a thumbtack on one of our cathode prototypes and the board did not explode or tear. Eugene reported that he had updated some numbers from his tension calculations with and without the central hole. See GlueX-doc-1090 for more details on Eugene's work.
- DSC and Chuck have completed work (for now) on preparing the R&D schedule for the cathodes. Copies of the plan have been circulated to all folks involved. Please consult this regularly as you plan your work to understand better the order and the time assignments. Contact DSC with questions. - Cathode flatness measuring system: * It looks like all parts n' pieces have arrived, although Bill was not sure about the FSU pieces. * The system will employ an old granite table that is now in the Physics Storage Building and is ready to be moved to EEL 126. This table (4 ft (w) x 6 ft (h) x 1 ft (d)) will be used to support and to define the flatness of the cathode support ring. Bill will ensure that all relevant safety issues are dealt with in the design. Mark is doing the work to include the stabilization pieces on the table. * Bill is planning on overseeing the assembly of the system once everything shows up. * Micah reported on work that he has been doing to generate contour plots of the surface flatness from the 2D data. He has sent around some sample plots for folks to look at, but he still has some work to do. * We will have to work out a time-sharing plan for the laser measurement head for the flatness measurements and the tension measurements. - 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.
Machine Shop Work
- The modification to our aluminum assembly jig is complete and it is now sitting in EEL 126. The new aluminum assembly jig is also complete and is now in the EEL clean room. Brian has test fitted the STBs and HVTBs onto the jig plates and has reported that everything fits properly and the clearances are adequate for all components.
Wire Frame Construction
- The frame that was used for our wire tension load test (which is discussed in the FDC TDR) will be modified to include the pockets for the rigid-flex assembly and the bolt holes. It will be machined to the nominal I.D. and O.D. of our wire frames. The foam core and the G10 skin will be removed to an I.D. of 1032 mm to account for the problem with the HV decoupling capacitor placement. The frame should be done in the shop before the end of next week. The plan is to redo our loading tests and measure the in-plane and out-of-plane distortions of the wire frame up to a load of roughly 50 lbs (the full wire load is about 35 lbs). We still have some details to work out on the test plan specifics. Bill will talk to Tim about completing a series of FEA calculations. - The nominal wire frame construction plan devised by Brian will be our starting point for construction. Folks should look this plan over in some detail and we will step through it before the start of construction to make sure that no steps are left out. The plan is posted on the FDC web page under the procedures link. - 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. - Simon and Herun have completed the HV checkout of the STBs. Some details are included in the FDC logbook entry #377. Two suspect capacitors were found and replaced. - The HVTB electrical checkout has also been completed. As there are no capacitors on these boards, the 1M resistors were checked as O.K.. No problems were found. As reported in the last meeting, there were some filter capacitors soldered to the face of the HVTBs that should not have been put on until the phase 2 stuffing. These were removed and the boards cleaned before the HVTB checkout began. - 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. - DSC has prepared two documents for our wires. One for the specifications for the sense and field. A second focusses on what tests we will do with the wires. These documents have been prepared based on the CLAS specifications and have been updated after recent discussions with Steve Christo. Brian will send these to CFW and Little Falls with our procurements for the full-scale prototype. When these documents are finalized, they will be posted to the FDC web page. - DSC and Fernando met with Kim about redoing the capacitor placement on the STBs. All capacitors must be moved radially inward of 1020 mm diameter to allow sufficient room for the wire frame o-ring on the G10 skin. It looks like there is sufficient room to do this. Kim and Fernando will meet one more time before Kim fully embarks on this task. - We talked about appropriate containers for storing the wire frame PCBs. We will revisit this issue before the final detector procurement. For now, Fernando has purchased some containers from Target that will do the job. It might be that we ultimately want to supply the PCB company with shipping containers as even inserting the boards into static bags can cause unexpected damage.
Test Frame Wire Winding
- IUCF has supplied the official report from the Phase 1 wire winding continuation. As Elke and I have some questions with the document, we will have a phone conference with them next week. - We are awaiting an official budget for Phase 2 and we will also review this in our conference with IUCF. If the budget comes out too high, we will begin more serious dicussions with IUCF on bring their wire winding facility to JLab.
- Since our last meeting we have done more thinking about the design of our spacer ring. It was to be composed of a composite design with an o-ring groove on each side and a gas port through the middle. We decided at our last meeting that the design would be greatly simplified if we could replace the composite with a solid material and we began focussing on CH2. In the mean time, we have come to the realization that there are better materials (from a structural standpoint) than CH2, e.g. nylon-6. Bill is looking into this and will let us know what he finds. We do need to ensure that what we use has a density close to that of CH2 (or the composite) and is chamber friendly. - We are also strongly considering epoxying the spacer ring directly to the face of the cathode. There seem to be no compromises here. We eliminate an o-ring and give Bill more room for his gas feedthroughs. - 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 use 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 needs to merge this document with Fernando's cleaning and handling document.
- Simon and Fernando are in the home stretch on completing the specification of the cathode and anode ASIC dynamic range. All required measurements have been completed and work is ongoing to finalize the test results in the document. What we have so far is posted as GlueX-doc-1070. - 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 (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.