Difference between revisions of "Minutes-4-17-2008"
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the measurements from the minimum ionizing muons to the more heavily | the measurements from the minimum ionizing muons to the more heavily | ||
ionizing hadrons that will be in the FDC. | ionizing hadrons that will be in the FDC. | ||
− | - In FDC log book entry #357, Simon posted an [http://www.jlab.org/htbin/PHYSICS/halld/enote112.pl?nb=notebook&action=view&page=357| X vs. Y plot] from the small-scale prototype | + | - In FDC log book entry #357, Simon posted an [http://www.jlab.org/htbin/PHYSICS/halld/enote112.pl?nb=notebook&action=view&page=357| X vs. Y plot] from the |
− | + | small-scale prototype measurements with the 2 micron cathodes. He saw | |
− | + | evidence of waves in the reconstructed wire positions. We need to | |
− | + | understand if this is an issue with the pulser calibration. Simon believes | |
− | could be part of the problem. Fernando also measured the resistance | + | that this could be part of the problem. Fernando also measured the resistance |
across strips with a sample of the 2 micron cathode boards. Here the | across strips with a sample of the 2 micron cathode boards. Here the | ||
strips were all about 5 inches long. He found resistance values | strips were all about 5 inches long. He found resistance values |
Revision as of 16:26, 17 April 2008
FDC Weekly Meeting
Date: April 17, 2008
Participants: Daniel, Simon, Fernando, Roger, Mark, Kim
Next Meeting: April 24, 2008 @ 1:30 p.m.
Contents
- 1 Cathode Planning
- 2 Full-Scale Prototype
- 3 Test Frame Wire Winding
- 4 Stack Assembly Procedures
- 5 Composite Cathode Updates
- 6 Grounding Issues
- 7 Cooling System Tests
- 8 Gas System Design
- 9 Gas Volume Definition
- 10 STB/HVTB Discussion
- 11 Cathode Board Discussion
- 12 Small-Scale Prototype
- 13 Drawings
- 14 Work List
Cathode Planning
- Roger has received a quote from Allflex for the cathode boards for the full-scale prototype. This quote was for roughly $10k for 5 sets of boards. Allflex is in contact with Nippon Steel Chemical Co (the board material supplier) about availability and delivery of the 1 mil Kapton/2 micron Cu board material. Roger is expecting to hear back from his contact at Allflex within the next several days. - Fernando needs to prepare a the electrical specifications (board tests) for the cathodes to be built into the order. This should be completed within about a week or so (if possible). - Once we are assured that Allflex can make the boards, Roger will hash out how we should specify the flatness/handling/defect specifications in the order. - Roger has heard back from Multek and they stated that they would not enter a bid because they cannot handle our board widths. Roger will continue to look for material suppliers and board houses for our cathodes. - Greg Arnold's group made a first attempt at soldering the rigid flex assembly to a semi-realistic cathode board. The process used a standard soldering iron, and the results were somewhat mixed in that the solder region was a bit wavy/uneven. They have purchased an air pencil system and will use this on their next attempt. Fernando will also look into obtaining conducting epoxy for Greg's group to use. Roger ordered a total of five sets of test boards and it seems clear that by the time Greg's group is done, we will have finalized the rigid flex soldering procedure and specifications. - Note that 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.
Full-Scale Prototype
- The G10 for the frames has arrived. The only remaining frame component that is missing is a portion of the Rohacell order that should be in soon. This is the 2-mm thick Rohacell for the cathode backing. - The rail order has arrived. Bill still needs to provide drawings on the attachment brackets to the FSU shop where they will be made. This is not a super critical item for us at the moment. - Brian spoke with Dennis Skopik about clean room space and it is clear that this will be an issue. Dennis is trying to work something out to satisfy the short term needs of all groups, but the FDC assembly needs to be in the clean space for essentially all work, so sharing the clean tent with other groups does not seem like a viable solution. DSC will follow up with Brian and Dennis on our requirements. Dennis did ask that we not purchase the second construction station if the only place that we can store it is in the clean room, i.e. wait for him to give us the green light. We need to keep applying pressure to him to have the best chance of giving us a move-in date that is compatible with our schedule. - Roger has communicated with Greg Arnold about our need for his group's services for the cathodes and cathode assemblies in the next few months. - Brian talked to Casey in the machine shop about completing the modifications on our aluminum tooling plate for the wire frame construction. Casey thought it best to do this until just before construction. DSC has suggested that this work is completed first thing after Brian returns from IUCF (April 28-30) so that it is ready after Brian gets back to JLab from vacation on May 6.
Test Frame Wire Winding
- IUCF has now blessed the entire wire winding facility and Brian is scheduled to leave for IUCF on Saturday April 19. Once there he will enjoy a week of fun and relaxation. Keith Solberg at IUCF believes that by Friday April 25, all of the Phase I winding will be completed with all measurements carried out. - DSC will arrange for several teleconferences with IUCF during the week that Brian is visiting so that we can keep up to speed on progress and issues throughout the Phase 1 winding process. - 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.
Composite Cathode Updates
- Brian and Denny have made another backed cathode using our standard construction procedure. Brian incorporated the grounding tabs for the ground plane using Fernando's suggestion of add small copper strips around the perimeter of the back of the G10 cathode frame. The faston tabs will be attached (via solder or conductive epoxy) to the copper tabs. - Fernando has gotten the laser measurement system from Acquity Laser fully working and is now ready to hand this over to Brian to measure the level of bulging on one of our prototype cathodes. We are concerned that the plane is too "floppy" and has too much gravitational sag (the old beer gut problem). The measurement should quantify this problem and give us feedback into the need for increased tensioning of our cathodes. It might be that Denny could take this on next week's in Brian's absence. - Brian will also work to make a "tensioned" cathode plane without the Rohacell backing. So far he has put together the 3 cathode board pieces and set them aside until the tensioning apparatus is set up again. We need to quantify how much tension we can put on the planes without distorting the electrodes (or only distorting them within allowed tolerances)? Is the Rohacell (only 2-mm thick) actually worsening the problem due to its weight and flimsiness? Of course, if we can successfully design a cathode plane without the Rohacell backing, the issue of sealing the Rohacell becomes moot.
Grounding Issues
- Fernando has nearly completed preparations of an overall grounding specification document. This is needed for pre-brief material for the upcoming system review. It should be ready in the first part of next week.
Cooling System Tests
- Denny has nearly completed the set up of the cooling system. He still has to include the thermistors for reading out the coolant temperature local to the preamplifier board. DSC will contact Bill Crahen to get the aluminum and copper brackets for these tests.
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 after the review is over.
Gas Volume Definition
- No progress on new calculations during the past week. We will revisit the issue of modeling the gas in the drift cell region if the input is in the wire frame or spacer after the systems review.
STB/HVTB Discussion
- Kim raised an issue with the design of the wire frame circuit boards. She stated that she believed the overlap regions on neighboring boards (the half-lap regions) are too flimsy and not mechanically strong enough. She would prefer if we moved to a butt joint design. DSC talked to Tim after the meeting and he stated that the overlap is absolutely crucial for the mechanical strength. His suggestion was to make the thickness of the overlap portion closer to 13 to 14 mils instead of 10. Perhaps we are leaving too much room for epoxy clearance. - 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. - Roger was planning to do some test soldering for the rigid flex cables to a sample cathode board. No update was given during the meeting.
Small-Scale Prototype
- Simon has collected data with a 40/60 gas mixture and measured the resolution of the cathodes using the Hall B SIPs and charge integrating ADC (the standard picket fence measurement). The results are fully comparable with the 90/10 mixture. - Simon has measured the gas gain of the chamber with the 40/60 mixture and found a value of about 5x104, which is compatible with our calculated vale of about 1x105. - Simon has reconfigured the readout now using the ASICs, shaper, and FADCs to move on to the next step in the ASIC characterization. So far he has the readout working with the ASICs/shaper/FADC working on a set of anode wires (using a 100-MHz FADC). He is trying to get the FADC readout working for a set of cathode strips, but is having some minor technical difficulties getting the second 100-MHz FADC to readout. This will be a solvable problem in the near term. - We discussed how we need to quantify/measure the dynamic range on the cathodes and anodes. The procedure will be to measure the FADC spectrum amplitude distribution for all peaks in the spectrum above a baseline-subtracted threshold of 20 mV. Simon has posted some FADC spectra in the FDC logbook for the anode wires. These distributions typically have 3 to 5 peaks in them due to the arrival of the clusters on the wires. These plots will be posted in the logbook once they are made. To determine the FDC dynamic range, we then need to understand the amplification/attenuation in the system with the GAS-1 ASICS, shapers, attenuators and then scale the measurements from the minimum ionizing muons to the more heavily ionizing hadrons that will be in the FDC. - In FDC log book entry #357, Simon posted an X vs. Y plot from the small-scale prototype measurements with the 2 micron cathodes. He saw evidence of waves in the reconstructed wire positions. We need to understand if this is an issue with the pulser calibration. Simon believes that this could be part of the problem. Fernando also measured the resistance across strips with a sample of the 2 micron cathode boards. Here the strips were all about 5 inches long. He found resistance values typically below 3 to 4 Ohms. However, there were several strips with values above 10 Ohms, and one measured 100 Ohms. We need to understand if this is due to an inherent problem with the board.
Drawings
- 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.
Work List
- 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.