FDC Weekly Meeting
Date: July 10, 2008
Participants: Daniel, Simon, Brian, Fernando, Mark, Eugene, Bill, Micah, Kim, Roger
Next Meeting: July 17, 2008 @ 1:30 p.m.
- Cathode delivery date is expected in roughly 2 weeks. - Roger will contact Allflex to have them let us know when the transport and storage box has arrived. We will modify this box upon arrival at JLab to include the ability to flow nitrogen or dry air to prevent oxidation of the copper traces. - Fernando has been thinking about the electrical QA checkout procedures for the cathodes. He has ordered some probes for this work. He will prepare a procedures document and circulate in the next week or so. We expect that this work will be carryed out in the clean tent using the new granite table that should arrive on August 1. - We discussed a plan for precision edge cutting of the cathodes. Bill and Brian will sketch out a plan for how to proceed. Once we are all satisfied, we will do some test cuts on pieces of the dummy cathode boards and pieces of blank Kapton. - Roger plans on ordering a set of 3 to 5 of the new cathode daughter boards that we plan to use with the full-scale prototype. We expect that with the copper fingers extending off the flex cable, that soldering to the cathode surface will be a very straightforward procedure. - Roger is working with the Allflex representative to find whatever information is available from Nippon on the raw material specifications. He has gotten some information through Allflex and will circulate this shortly. - 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. Chuck is responsible for looking into this and letting us know. He will get on this after his committments for the CD-3 review are done with. - Brian will modify his Lucite box design for storage of the completed cathode planes. The cathode planes can stack upon one another (unlike the strung wire frames). As this box is not needed for at least several months, this work is not super high priority.
- The work on the assembly jigs is in queue in the JLab machine shop. The work should be completed by the 3rd week of July. Once the jigs are ready, we will move to begin construction of the full-scale prototype wire frames. At some point in the near future, we will need a crane (A-frame) for lifting of the tooling plate. DSC will talk to Elke about this. - The electrical work to connect the clean tent to power has been completed. Another group will be using the space for about a week during the last week of July. However, given that our granite table does not arrive until August 1, there should not be a conflict. - 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. This work has not yet gotten underway.
- DSC circulated a cathode R&D planning document to the group for feedback. Brian and Simon are now going over this document to ensure that the task list is necessary and sufficient to complete our design work on the cathode construction procedure. Once we have a complete task list, DSC will prepare a time line so that we can understand the impact on FDC design completion and the start of construction. - Brian has been in discussion with some outside companies about our technique of joining the three separate cathode boards together. There are some important points that are coming to light: > The use of 2-in wide Kapton tape is certainly not be best joining material that we can use as there are much better adhesives out there. We would be much better served to use Hysol adhesive on blank Kapton strips. Brian is still digging up information on whether the improved strength is against peeling or sheer forces. > The strength of the bond of neighboring boards will be improved if we use a wider strip of tape. We may ultimately need to consider this. > The 20-in wide Kapton rolls that Allflex receives are sliced from 60-in wide rolls made by the material vendor. Apparently it is the case that the tensile strength of the middle pieces have a different profile that the outer pieces. Once the 60-in roll is slices up, they do not keep track of inner and outer pieces. This is problematic if we require a large tension to be applied to our 3-piece cathode. The distortion of the electrodes would be different for the different pieces! This would demand that we want the tension to be as low as possible. This also could be a problem if we want to use a fixed weight to define the cathode tension. With different tensile strengths in the different pieces, we could not guarantee a fixed tension. Anyway, some things to consider as we move forward. > The key in all of this is how flat the cathode pieces from Allflex are. In the past, our technique has been to apply enough tension to remove the wrinkles. If the delivered cathode pieces are very flat, we are certainly in a much more advantageous position. We also eliminate the worry about stretching the cathodes if we can employ a low enough tension and also eliminate worries about the joints between boards pulling apart. - From the flatness measurements that have been made on our prototype cathodes to date, the version with the 2-mm thick foam backing will not work. The bulging profile is too large. This is presumably due to gravitation sag of the foam. We are doing measurements now that will address this. The apparent bulging that we have seen in the unbacked (tensioned) cathode may not be full real in that the measurement system could not force the cathode to flat. The bulging is like associated with a potato-chipping of the support frame under the tension load. - Brian has ordered a roll of Kapton 48-in wide. We will use this to test various cathode construction techniques and to study methods of attaching the cathode to the frame. Brian will work to develop a system to measure the cathode membrane tension while on the tensioning fixture. This system will use the laser measurement head that we have for the flatness measurement system.
Test Frame Wire Winding
- The paperwork for the continuation of the Phase 1 wire winding contract with IUCF should be completed this week. DSC and Keith are finalizing the work plans. Work should continue next week. - We need to make a decision on whether to purchase new Cu-Be wire given the defects that we saw under the SEM. DSC will talk to Elke about budgets on this. - 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
- Micah will continue making measurements of the surface profile of our backed and unbacked cathode prototypes as a function of rotation angle. He will also disturb the cathode surface and study repeatability of the measurements. - We need to work 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? - Bill has looked at our cathode flatness system and is not satisfied that it can deliver anywhere near the accuracy that we require. He will work to re-engineer the system using existing pieces, pieces that we can dig up at JLab, and new pieces. - Micah and David put together a list of parts 'n pieces for the measurement system upgrade. DSC has worked with Lorelei to order the parts. They should arrive in a week or two and then the upgrade work on the system will continue.
Cooling System Tests
- Bill installed the flow valve in the cooling system in F117. - Fernando has completed a series of tests of the cooling system as a function of the temperature setting of the water reservior for fixed flow rate. A flow control valve has just arrived an will be installed next week. The plan is to perform more cooling studies as a function of flow rate for fixed temperature. Fernando will prepare a GlueX note when the studies are finished.
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.
- 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.
- Simon is continuing his work to specify the ASIC dynamic range. He has taken lots of data with the small scale prototype and has completed a series of simulations using GARFIELD to connect the cosmic ray and X-ray source data to what we expect with pions and protons. So far he has been able to use GARFIELD to reproduce the chamber data with cosmics and X-rays. He will now work to specify the dynamic range for cathode and anode and update the draft of the associated report. This work is posted as GlueX-doc-1070. - Fernando has suggested taking some data with a 90-10 Ar/CO2 mixture to ensure that we fully understand the 55-Fe data and to allow an easier connection with the CDC data. The 90/10 gas mixture is now flowing in the prototype and Simon is beginning to take some data. - 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.
- 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.
- 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.