FDC Weekly Meeting
Date: August 7, 2008
Participants: Daniel, Simon, Chuck, Brian, Fernando, Roger, Eugene, Bill, Micah, Herun, Mark, Jim, Slava, Elke
Next Meeting: August 14, 2008 @ 1:30 p.m.
- After the FDC meeting, there was some high-level discussion about the recent issues that have come up with the FDC design that have not been fully studied through calculations or prototypes (see below). We are all quite nervous about diving into construction of the FDC without giving full consideration to the design changes. What is at stake is completing the construction of the full-scale prototype and completing a prototype detector that will have the same mechanical and operational properties as the final FDC detector. Elke would like to schedule an interal FDC readiness review to go over the design and construction to make sure that we are on course and all necessary things are being considered and looked at. - Elke's email: Dear Dan et al., I have been thinking more about what I heard today in the FDC meeting and I also had a discussion with Elton and Simon and with Tim. I think it would be good we do a readiness review for the prototype construction. The idea is that we internally go through the latest updated drawings and planned procedures to construct the wire and cathode frames and how we are planning to put things together. I have quite some questions on what are the tolerances on the thickness of the composite frames (wire and cathode). How do these influence the glueing of wire and cathode frames? Is it realistic to mill out a 0.2mm pocket of the frames, what are the tolerances needed? I don't want to have a review with a lot of reviewers, but I want that we sit together for an afternoon and go through things with drawings in front of us and every person responsible describes the procedures and people can ask questions. I also think we need to have a mechanical mockup of the wire frames, the cathode frames put them together. How does all this change influence that we have used different frames for the test winding, how much more do the wire frames pringle because of the changes? How do we plan to put 2 pringled planes (wire and cathode) together? I hope you understand I don't want to be difficult, but there seem to be too many things which are not 100% clear which might influence how we want to do things. So we should discuss it.
- We got official word from Allflex that the cathodes will not be shipped until Aug. 14. Shipping and Receiving has gotten instructions not to open the transportation box. This will be done in the clean room. The cathodes will not be removed from the box until we have our own definite handling instructions in place. All relevant folks will be on hand for this event. - The shipping box will be modified after its arrival to include gas fittings so that we can flow nitrogen through the environment. The addition of the gas fittings must be carefully planned out to ensure that no damage is done to the cathodes and no dust gets into the transport/storage box. - We are working to get ready for the full QA checkout of the cathodes immediately on their arrival. This work will be done in our clean tent in the EEL building. Fernando has gotten nearly all of the test equipment and supplies ready. He has posted GlueX-doc-1082 detailing the electrical QA test plan for the cathode boards. Once we complete the QA checkout on the boards, we will want to communicate this information to Allflex and if everything is acceptable to us, move to complete the order for the remainder of the cathode boards for the full-scale prototype. - The new granite table is now fully assembled in the clean tent. It will have to be thoroughly cleaned with alcohol prior to use. - Bill has been working on other things for the project and has not made any progress this past week on designing the system for the cutting of the cathode edges. He will return to this work when he has time. - Roger plans on preparing an order for the new cathode rigid flex assemblies with the copper fingers (cathode boards and cathode ground boards). This procurement will be completed by the end of August after Roger completes some additional design work. It was finally clarified during the meeting that even though we will only have a finite number of cathode daughter boards (boards with the ASICs), we have to fully outfit all of the cathode boards for the full-scale prototype with the rigid flex assemblies as they are soldered to the cathodes. Thus we will need a minimum of 9x2x3=54 rigid flex assemblies for the full-scale prototype. We will get a quote for these as part of the ordering process, but we are looking at a charge of roughly $5k (including board stuffing) for this order. - Lucite box: DSC raised the possibility of storing all wire frames and completed cathode boards in a single Lucite box for the full-scale prototype in an effort to save some money. We shall have to think a bit about schedules as the Lucite box will have to be used for transport of the full-scale prototype wire frames from IUCF and we do not want the completed cathodes sitting out in the air for too long to keep them from oxidizing and from being exposed to dust and humans. - We did not have time in this meeting to talk about cutting holes in the cathodes (gas holes and central beam hole). This is an important issue that we will have to seriously consider. The worry is about losing tension in the cathodes if the holes (especially the big central hole) is cut after the cathode is tensioned. This work is an important part of our upcoming R&D planning for the cathodes.
- There was some question about the thickness of the cathode plane foam core thickness. In the model is it 3.4 mm and Bill and Chuck have verified that the cathode daughter boards mounted on the frames are not in the same azimuthal region from layer to layer so that there is no conflict. Thus the 3.4 mm foam core for the cathodes is indeed the nominal design value. - DSC is working with Chuck to put the cathode R&D work into an official project schedule. We have a preliminary time line laid out and are now working on finalizing the required ordering of the tasks and the manpower assignments. This work is required so that we respect the FTE assignments of various folks to the project and that there are nominally 8 hours in a work day. We will work to post this schedule very soon so that we can use it as our official project guide and tracker. - Cathode flatness measuring system: * Bill has finished the design drawings for the upgraded measurement system and has completed the PRs and sent them to Elke who has signed them. The parts will take about 2 weeks to arrive. * The system will employ an old granite table (now being worked on in the Physics Storage Building) that belongs to Hall B. This table will be used to support and to define the flatness of the cathode support ring. The table is 4 ft (w) x 6 ft (h) x 1 ft (d) and weighs several tons. Bill will ensure that all relevant safety issues are dealt with in the design. Bill reported that some holes have been drilled into the table and it will soon be moved over to EEL 126. The table will not be mounted on wheels, but will be moved about with a 5-T pallet jack located in the EEL building. * Bill is planning on putting the system together once everything shows up. * Bill has a number of smaller parts for the project that have been submitted to the FSU machine shop. These parts should be ready before the end of August. * Micah is continuing to work on the laser head control software for the measurement system and things are coming together. Micah has gathered some limit switches for the system that is in place now, but these will be replaced with new ones that Bill will order. * We will have to work out a time-sharing plan for the laser measurement head for the flatness measurements and the tension measurements. - Cathode tension updates: * Eugene has prepared a 1-page write-up detailing how to measure the cathode tension for 3 different measurement techniques (measuring the fundamental resonance frequency, using a weight placed on the cathode surface to measure displacement, and using gas overpressure on one side of the cathode and measuring the displacement). We have not yet converged on a final technique. Which one we employ may ultimately depend on when the holes are added to the cathode planes. * Eugene is working to define the allowable surface flatness variations for the cathodes. What can we tolerate and still deliver a system that can meet the resolution requirements for the cathodes and the wire plane? Eugene stated that he still is several weeks away from providing an answer. - Brian and Bill should begin to layout a detailed outline for the cathode construction steps and circulate for feedback.
- Fernando and Kim will work to put together the PR for the manufacture of the LV cables needed for the small-scale prototype and the connectors for the signal cables. We have the signal cable material and the tool for crimping on the connectors. The plan is to have the LV cables made by an outside company and to make the signal cables ourselves.
Machine Shop Work
- The work on the assembly jigs has been started in the JLab machine shop. These pieces are slated to be completed on August 15. We will do dry fits of our circuit boards on the jigs to make sure that there are no problems with the design and that the components fit into the recesses in the jigs. - Bill is working to put together the request for JLab machine shop work for the work on our wire frames. The relevant upcoming projects include: 1). Drill in bolt holes on 4 FDC wire frames, 2). Cut out annular pocket for the amplifier boards on the back of the wire frame.
Wire Frame Construction
- This week we found an important design problem with the STBs. The placement of the HV blocking capacitors on the back side of the board was not compatible with the placement of the foam and backing G10 skin that was to contain the o-ring. In fact the location of where the o-ring was supposed to go basically overlapped with the positioning of the capacitors! We had an impromptu meeting on Wed. to come up with a preliminary work around. What we plan to do is to reduce the I.D. of the foam core and to not include the o-ring groove in the backing G10 skin. For construction of the prototype, we will laminate the wire frame to the cathode board in order to provide a gas seal. We will ultimately have to modify the STB design in this respect, but there probably will be other design changes as a result of what we learn with the prototype anyway. Before this work-around is finalized, Bill (or perhaps someone more familiar with this type of modeling) will carry out some FEA to be sure the solution works. - We have also been discussing the plan to allow for the required clearance in the back of the G10 wire frame skin for the rigid flex assemblies. The plan was originally to cut out pockets of the appropriate shape for each assembly. However, the machine shop does not have an efficient system to carry out this work. It was discussed that a simpler and more cost effective solution is to cut out a 10-mil deep annular pocket. The design solution needs to be modeled with FEA to study the impact on the mechanical design. This pocket was not part of the wire frame that we did the load test on. - Brian circulated a construction plan outline for the wire frames. As there was no additional feedback since the report was circulated and reviewed last week, this plan is our baseline construction approach. Our goal is to have the 4 wire frames for Phase 2 winding done by the third week of September. - Tim has indicated that we can get the A-frame for the frame construction at any point now. Brian will get this and move it into EEL 126 once some additional details are worked out (like how long we can have the A-frame for, etc). - Simon is putting together a test plan for the HV check out of the STBs and HVTBs. A draft has been circulated and will be finalized in the next few days. Herun has already begun to carry out the testing with Simon. All PCBs will need to be checked before construction begins. Simon has estimated that as the process of checkout is rather slow, it will take about half a day to complete checkout of each STB board. - Note: we are essentially out of wire and will have to order another spool of both tungsten and CuBe wire. DSC thinks that we should move to Little Falls Alloys for the next spool of CuBe (given the problems that we saw with the first spool). Brian will put together the PR so the wire arrives in time for Phase 2 winding of the prototype.
Test Frame Wire Winding
- IUCF has completed the wire winding of an additional frame and has completed the wire position measurements. Things look much better than the last attempt, although it still appears that there is an offset in the positioning of the field wires on the table relative to the sense wires of about 40 microns. DSC will go over this with Keith when he gets back from vacation. We will try to work out a plan to rectify this problem. The IUCF folks are now measuring the wire tensions. The tension data should be in our hands before the end of the week. - 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. - As the time to complete Phase 1 and Phase 2 winding before the end of the fiscal year will be super tight, DSC will work with Elke to complete as much of the required Phase 2 paperwork as we can in the next few weeks so that we can move quickly to getting Phase 2 in place before time runs out.
- To allow better clearance for the cathode board rigid flex assemblies on the cathode that faces the wire, Chuck needed to shrink the radial extent of the spacer ring. The design has put the edge of this spacer too close to the bolt holes for Bill's comfort. He raised the issue of possibly changing the design of the spacer from a composite design back to solid polyethylene (CH2). He stated that this would make the worries about its mechanical strength moot while making it much easier to include the gas inlet and outlet ports. As the radiation length of CH2 is comparable to the composite, we took this suggestion seriously. - Bill would like to do some test o-ring cuts in a sample of CH2 to inspect the edges for precision. There are several options to potentially improve the machineability of CH2. The first is to use liquid nitrogen to freeze the material before the measurement head comes in contact with the material. The second is to order CH2 impregnated with fiberglass. - One aspect of the discussion on CH2 vs. composite is the different thermal expansion coefficients for the different materials. Bill will do some calculations in this area to understand the issues that could arise.
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
- Bill and Fernando completed the planned cooling system measurements for the daughter boards. Fernando is working to put together a document of the test results. He indicated that no further cooling system tests are planned until we have more cards and can test a bigger portion of the system. So far, things are working according to expectations.
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. He reviewed with us his approach to this work. 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. 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 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.
- 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.
- 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.