FDC Weekly Meeting
Date: June 5, 2008
Participants: Daniel, Simon, Brian, Fernando, Kim, Roger, Mark
Next Meeting: June 12, 2008 @ 1:30 p.m.
- Roger has distributed board files to Chuck and Bill to look over the gas hole placement. He will also distribute board files to Fernando to look over the circuit layout. At the same time, Roger is preparing a draft of the PR and is working on finalizing the fabrication notes. He will circulate a copy of these notes this week for review. - DSC spoke with Elke about the total cathode board costs. The quote is expected in the next few working days from Allflex. We have about $20k in the budget and we will decide what we can purchase when we have the quote in our hands. - Additional solder tests of the rigid-flex assembly to the cathode board mock up will proceed after Roger gets the hot air pencil from Fernando. This work will wait until the cathode board PR is completed. - 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. - Bill arranged to have the cathode transportation box sent directly to Allflex. - 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). He will make some minor modifications to the existing box drawings and prepare the PR.
- Greg Arnold's group is nearly done with the soldering of the HV capacitors to the STBs and HVTBs. Two completed sets of boards have already been delivered to Simon. Kim has asked Greg's group to complete 5 complete board sets (including putting resistors on at least one more set). This will enable us to prepare up to five wire frames for winding for the Phase 2 phase. - The order for the 5 ft x 5 ft granite table got held up to a snafu on shipping costs. The table will take 4 to 6 weeks to arrive once the paperwork is finalized. - Brian and Kim are making progress on finalizing the drawing for the aluminum tooling plate for the cathode frame and anode frame construction. This should be done very shortly and turned over to Casey in the machine shop. Once he gets this he will modify the existing tooling plate and make a second plate. - Brian has moved a storage cabinet into the clean tent in the EEL clean room. He will also shortly move in a work table. Dennis Skopik has been asking when we plan to start to do work in there. As Brian will be gone for most of the remainder of the month, it appears that work will not take place in the tent for some time. - 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.
- Brian has attached a ground plane to the back of our tensioned cathode plane. This work was done to develop a way to ground both sides of the ground plane. The technique employed is to use a piece of copper tape and stick it into a pocket machined into the edge of the G10 skin. Silver epoxy is used to make a conducting connection to the top side of the ground plane. The external ground connection can then be made to that portion of the copper that sticks out. After a bit of discussion, we are worried that the copper tabs will be too fragile and will eventually tear off. DSC suggested to use a piece of flex board (copper coated Kapton). The Kapton will be much less susceptible to tearing. We will work to develop this method. This method can also be used to make additional ground connections to the cathode boards. - One thing that Brian noted was that the ground plane that is attached is actually a second attempt. The epoxy did not cure on their first attempt. What is a concern is that the epoxy in the sample cup did harden completely, but the thin film under the ground plane did not cure. Brian believes that this was due to unusually cold temperature in the machine shop. The curing time of the epoxy is temperature dependent. This is something that we will monitor carefully. The cooler the temperature, the longer the epoxy curing time. - We will try to develop a cathode tension measuring system using our laser measurement head. The procedure will be to direct a puff of air at the center of the cathode and measure the amplitude fluctuation vs. time through the laser measurement system. Fitting this amplitude distribution will give us (hopefully) the fundamental frequency that we should be able to convert into the membrane tension.
Test Frame Wire Winding
- After the regular FDC meeting, we had a teleconference with the folks at IUCF on the phase 1 wire winding. While much progress has been made, the facility is still not yet able to meet our wire position and tension specifications. We decided to pursue extending the phase 1 contract to allow for up to two additional planes to be wound. Brian and Simon will gather the two additional wire planes that we have made for shipment to IUCF. The bottom line is that we will put off discussion of phase 2 with IUCF for the time being. The plan is for IUCF to provide a rough cost estimate for the extension work before we move on this end. We will plan to have a meeting with the IUCF management during the middle of next 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. - Note that Brian completed inspection of the wire frame that he transported from IUCF to here. The final report is that there were no broken wires. Good news.
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
- Denny is continuing to study the flatness of our prototype cathodes. Presently he is moving the system to EEL 126 to get it ready for our summer student Micah to take it over and complete the existing measurements and to upgrade the system to automate the 2D scans. Friday June 6 is Denny's last day with us and DSC will meet with him to go over where we are.
Cooling System Tests
- Denny reassembled the preamplifier cooling system in F117 and set the flow and temperature. Fernando is getting ready to perform the cooling system measurements. Bill has ordered a flow control valve that will arrive shortly and be installed in the system.
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.
- Work continues on characterizing the preamp daughter boards to specify the ASIC dynamic range for both the FDC cathodes and wires. Simon is extracting from the data the amplitude distributions. He is making progress in acquiring spectra where noise-related events are not included (so that we do not bias our results). Once he has acquired the spectra for minimum ionizing particles, we need to convert this into the numbers required for the more heavily ionizing particles of interest. - Simon, Fernando, and DSC will prepare a write-up of the analysis results and assumptions that went into specifying the dynamic range numbers for the anodes and cathodes. - Brian performed an optical scan of the edges of the 2 micron Cu cathode boards in the small-scale prototype (actually he scanned one of our spare planes). He used a x50 microscope for this. He found that the edges were pristine with no evidence of any wavy-ness. This rules this source out as a potential explanation for the wavy wire position reconstructions with the current prototype. This leaves possibilities of gain miscalibrations (Simon will take more data in the near future). Another possible source that was discussed in the meeting was a surface wave in the cathode. Brian indicated that these cathodes were not a tensioned as previous versions. We will perform a visual inspection when we have time.
- 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.