Difference between revisions of "Minutes 3-28-2007"
From GlueXWiki
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- Elke stated that it makes sense to get this MOU in place as soon as | - Elke stated that it makes sense to get this MOU in place as soon as | ||
we can. | we can. | ||
+ | |||
+ | 8). Small-Scale Prototype Work: | ||
+ | - Given that we expect the +/-75 degree cathodes to be available within | ||
+ | about 2 months, it may be that we will not need to worry about employing | ||
+ | the 90 degree cathodes. They are available to install, but installing | ||
+ | them will be put on hold for now. It may be that we will install them | ||
+ | at some point to get some more information to check Simon's calculations. | ||
+ | - Simon has been studying a modified argon-CO2 mixture in the small-scale | ||
+ | prototype consisting of a 40-60 mixture to understand the impacts on | ||
+ | chamber performance on the cathodes. He also needs to be able to very | ||
+ | soon quantify the impact on the time-to-distance calibrations and the | ||
+ | impact on the resolution in the wire plane. | ||
Minutes prepared by Daniel. Send any comments or corrections along. | Minutes prepared by Daniel. Send any comments or corrections along. |
Revision as of 11:52, 29 March 2007
FDC Weekly Meeting
Date: March 28, 2007
Participants: Daniel, Tim, Kim, Simon, Brian, Chuck
Next Meeting: Wednesday, April 4, 2007 @ 1:30 p.m.
1). FDC Budget:
- Work continues to update the budget for the nominal FDC system design. This update of our Dec. 15, 2006 version (GlueX-doc 735-v1) is needed for the CD-2 review. It is due to Elke and Elton early next week. - The remaining issues for the budget justification document for the nominal design are as follows: > Brian Kross is working to provide an estimate for the CH2 spacers and associated machining. > Brian Kross is working to provide a more ``official" version of the JLab shop estimate for the G10 frames. > Brian Kross needs to provide a cost estimate for the stainless steel gas ports (inlet and outlet). > Brian Kross needs to provide a cost estimate for the plastic wire frame storage containers (to be shipped to FNAL). > Tim Whitlatch needs to provide a cost estimate for a shipping bed for the chambers in their drive back from FNAL to JLab. > Joe Beaufait needs to provide a cost estimate for the updated LV system. - Note that cost estimates should include emails from vendors, quotes, or the basis for the cost estimates. - In preparing the FDC budget, we are concerned their there may be some cost items whose price may be significantly more than we are assuming. This is the case because we are working on the design to minimize the amount of material in the active and inactive portions of the chambers. In our budget there are two such items. (i). Redesign of the cathode flex boards, (ii). Redesign of the chamber frames. The current status of each item is as follows: (i). Cathode flex boards: We are working to consider a design of the cathodes that replaces the copper with aluminum to reduce the material thickness. This is a tricky item to price out as PC board manufacturers will not touch aluminum and we are trying to get pricing information from lithography sources. Brian Kross is working to come up with some contacts so that we can make a pricing guess. (ii). Chamber frames: We are working to replace the 5-mm thick G10 frames with a composite design (fiberglass, carbon fiber, and Rohacell). The average thickness decrease is roughly a factor of 3. Tim Whitlatch and Brian Kross have requests out to separate manufacturers and they will come back to us in the next few days. It is already clear that the costs will be significantly higher compared to G10. - Strategy: Even though we are pricing our nominal FDC design, we will assign a higher contingency for these two items, as it seems clear that our nominal design is most likely going to change. We will also discuss with Elke about whether we should replace our current design with the new modifications.
2). Magnetic Field Issues:
- Brian has heard back from his contact at BNL regarding a magnet. They have a candidate and will look to see if the power supply still works. Brian indicated after the meeting that the magnet is the 48D48 dipole in the AGS. More to come. - Brian will follow up with Elke regarding her contacts in Hamburg. He did give all of the relevant information to her. - Simon has been working on literature searches to find out what gas mixtures are being used in the cathode chambers at ATLAS, CMS, PHENIX, LASS, etc. He has been performing GARFIELD studies of the Lorentz angle. His primary area of investigation so far has focussed on argon/CO2 mixtures with roughly 50% of each gas. For these mixtures, the Lorentz angle maximum in our drift cell is about 20 deg. This is a factor of 3 reduction from that computed for the 90-10 mixture. More work to come. - We are planning to have a phone conference with Andrey Korytov from the University of Florida (CMS CSC expert) on Tuesday of next week. Simon will circulate details of the meeting. This meeting will primarily focus on magnetic field issues in our cathode chambers. DSC has prepared an agenda/talking points for this meeting and will circulate them shortly.
3). FDC Design:
- Both Tim and Chuck produced CAD drawings (real CAD and ``foot CAD") for us to discuss. Tim focussed on a picture of the connector placement with the 5-mm half gap. Here the preamp daughter board connectors on the wire plane are mounted on the STB with no cut-outs on the G10 support frame. For the cathodes, the connectors are placed on the back side of the cathodes (where the Rohacell used to live). Chuck produced a new version of the 3-D picture showning all four FDC packages focussing on the placement of the connectors around the perimeter of the FDC with the new +/- 75 degree cathode strips. The connectors now are also placed between the rails on the under-side of the FDCs. This is still a work in progress and he is optimizing the placement. - Note that we are presently investigating splitting the central cathode strips in half (with readout on the ends) to reduce the rate issues on these chambers. - We still need insight from David about the size of the beam hole in each FDC package that we will deaden to provide coverage down to 1 degree. Once this is determined, we need to revisit the rates on the strips and the wires as a function of z-location of the packages. - We still need input from Fernando on how to get the cathode signals to the back side of the cathode planes. We want a robust connection from the front to the back. An important issue may be the quality of the vias with very thin conductive layers. - We discussed the cathode design option with no Rohacell backing. An important issue is the electrostatic deflection of the cathodes without backing. We have to keep the tension on these planes to a minimum to reduce the effect of lateral distortions of the strips. However, the lower the tension, the bigger the distortions. Simon has done some calculations of the deflection as a function of tension, but we have no clear idea of what the tensions on the cathode surface will be. Tim and Brian brought up the idea of performing measurements with strain gauges to connect to the calculations that Simon has done. This all seems possible, but because there needs to be a definitive answer, Brian will provide a write-up of a test plan to complete the measurements. Of course we need input from Simon on the maximum possible deflection to ensure the cathode and wire plane measurements are well within our tolerances. More to come. Tim will also consider performing some simulations with IDEAS. - We discussed possible approaches to mitigate the effect of the cathode distortions due to electrostatics. One idea is to bias the ground planes. We need to talk to Fernando and Gerard about the impacts of this possibility. We could also rely on maintaining a certain differential gas pressure across the cathodes to balance the electrostatic deflections. This seemed like a more dicey solution.
4). Cathode Mechanical Mockups:
- New dummy cathode frames have arrived. Brian has performed some initial QA checks. He noticed 3 ``stripes" in the cathode surface that appeared on the boards. These could have arisen due to the rolling procedure or the manufacture procedure. Brian is in contact with the company to learn more about this. However for the majority of the board surface, Brian was quite pleased with the quality. - Simon will get a sample of these cathodes and will perform measurements of the strip-to-strip capacitance. He will talk to Gerard about what other measurements would be useful to perform. - Simon will also talk to Joe about getting his capacitance measuring instrument. As Gerard is in town for the Collaboration meeting, he should take the opportunity to talk to him directly. - Brian has begun work on the next cathode sandwich mockup. He will begin with the design without the Rohacell backing. Before tensioning the cathodes, he will arrange to get them measured so that we can compare these numbers to the post-tensioning measurements to quantify the distortions. - After Brian completes the cathode sandwich without the backing, he will then construct a second cathode sandwich with the Rohacell. Of course he will employ the techniques developed during the first cathode sandwich construction, but there still are some issues that need to be worked out. This may lead to some modification of the tools and equipment.
5). Circuit Board Design:
- DSC asked Kim to provide a rough layout of the HVTB design for the full-scale prototype. Kim asked a number of questions to make sure that she understood the requirements. Simon will provide Kim with a part number for the HV Reynolds-type connectors. - Although Roger was not present at the meeting, we asked Kim to talk to him about the status of the design of the +/-75 degree cathode boards for the small-scale prototype. We also need to investigate if we need new G10 support frames (although we have 4 of the current design in stock). We would like these designs for initial review in about 2 weeks.
6). Summer Student:
- It looks like there are no more college students available to work on the FDC project. We are still looking into this. Kim suggested that we pursue a summer hire. This will be investigated.
7). FNAL MOU:
- DSC sent the current draft of the FNAL MOU to Karen Kephart at FNAL for initial (non-official) review. The two of us need to iterate on this before we start walking it through the JLab process. - Elke stated that it makes sense to get this MOU in place as soon as we can.
8). Small-Scale Prototype Work:
- Given that we expect the +/-75 degree cathodes to be available within about 2 months, it may be that we will not need to worry about employing the 90 degree cathodes. They are available to install, but installing them will be put on hold for now. It may be that we will install them at some point to get some more information to check Simon's calculations. - Simon has been studying a modified argon-CO2 mixture in the small-scale prototype consisting of a 40-60 mixture to understand the impacts on chamber performance on the cathodes. He also needs to be able to very soon quantify the impact on the time-to-distance calibrations and the impact on the resolution in the wire plane.
Minutes prepared by Daniel. Send any comments or corrections along.