Difference between revisions of "Minutes-1-27-2011"

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January 27, 2011 FDC meeting
 
January 27, 2011 FDC meeting
  
= Tentative Agenda =
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= Agenda =
  
 
# Production (David)
 
# Production (David)
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#* Further tests of top/bottom cathode signals [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, page 550] (Lubomir)
 
#* Further tests of top/bottom cathode signals [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, page 550] (Lubomir)
 
# Other
 
# Other
 
<!--
 
  
 
= Minutes =
 
= Minutes =
  
Participants: Dave, Chris, Simon, Beni, Fernando, Glenn, and Lubomir.
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Participants: Bill, Dave, Chris, Simon, Beni, Fernando, Glenn, Roger, Eugene, and Lubomir
  
 
== Production ==
 
== Production ==
  
- Dave: there was a walk trough the clean room yesterday with the vendor. The emergency exit door must be sealed better. Glass on the dark room door must be covered. The move in date is postponed to Jan 31. Dave has prepared conduct of operation documents for the clean room.
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- Dave showed recent pictures from the clean room that can be found on the M-drive: M:\facilities\Projects\Projects_100K+\Hall D FDC - Blue Crab Road Warehouse\Clean room\Construction\Photos\Construction. We will start moving in on Monday.
  
- New ETC schedule: the full package testing is postponed and squeezed. Fernando: even with the new schedule we may not have the electronics needed for the tests, so we need to have  alternative testing procedure.
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- Dave prepared an initial version of the FDC QA plan linked above. Pansophy data base will be used for the travelers: https://pansophy.jlab.org/pansophy/help.cfm.  
  
 
== Electronics ==
 
== Electronics ==
  
- Chris sent the first article signal cables back to the company to fix the cable problem.
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- Fernando: the first article cables were fixed and will be sent back to us.
  
- We discussed two issues with the rigid-flex assemblies. The thickness of the board is 18-18.5 mils, while it is specified to be 14+/-3 mils. Assuming before a thickness of 22 mils, Bill found this will cause a problem in a region where the connectors from two neighboring cathodes overlap. Bill will have the final word if this will still be a problem with 18.5 mils. The second issue is if we want to have the flex contacts tinned. It is related to the soldering procedure we want to use: conventional soldering, or using conductive tape. Fernando explained to us that the tinning can be done later during the board stuffing, although the tin layer will have different shape. This will give us time to investigate both options. Therefore, everybody agreed to approve the rigid-flex production as it is, i.e. with bare gold contacts. We discussed again the two soldering options. All they require more tests that we will do in the coming weeks.
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- Rigid-flex: once more we discussed the thickness of the rigid board (18.5 mil). Bill suggested reducing this thickness, but only if it's easy and can be done in time, otherwise it is acceptable and we are not going to reject the first article. Roger will communicate with the vendor. The parts needed to test the 3M conductive tape for soldering to the cathodes have not come yet. In any case we will continue with the mass production of the rigid-flexes with bare gold contacts that later can be tinned during the stuffing.  
  
- Fernando: thanks to Glenn the PR for the ASICs is now out and we expect all the ASICs by the end of May.
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- Roger: still waiting for the written response from Allflex to our report about the first article cathode foils.
  
 
== Engineering ==
 
== Engineering ==
  
- Working with the new stringing system is so far successful. Wires for one full chamber were strung. The wire positions were measured by Beni (page 549): the resolution is about 10-15 microns which is acceptable. The main issue is the flatness of the frame on the strongback. Right now the frame has a conical shape with the outer diameter sticking up (up to 1-2mm at some places) that makes problematic putting the wires on the pads. Bill proposed to add clamps (like a comb) between the wires too press the frame down to the strongback. These clamps may interfere with the wires during the stringing and so far the proposal is to cover the whole frame during the stringing with a flat sheet. It might be a problem to take it out since there's not enough clearance between the wires and the frame when it is at the lowest position. Another option was investigated by Casey: to tape down the wires close to the pads. He used the height gage to put the tape vertically; it moved by about 25 microns.
+
- Bill is working on some additional parts for the stringing system. The techs have been working with it last couple of weeks exercising different techniques. We discussed again the main issue so far, the flatness of the wire frame. Bill suggested using clamps that will be inserted between the G10 frame and the Rochacell ring. Fernando suggested a possible way to push the wire frame down from a supporting frame on the top. The way it works now is by taping the wires down to the board close to the soldering pads. This was proven to work: increase of the wire position deviations from ~10 microns to ~15 microns (sigma). Taping of all the wires is almost done and soon we will continue with gluing and soldering the wires.  
  
- Larry from Cross Computing was at JLab once more at the end of last week. He made few low level programs that were actually used for the position measurements. This automated procedure was checked by visually looking at the laser spot. Apart from a systematic offset (few tens of microns) different for the sense and field wires, the procedure gives consistent results.
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- The testing of the "cheap" conductive epoxy was not very successful so far, it has high resistivity. Eugene: it might be better instead of spending time on improving the gluing technology, to use the "expensive" epoxy. Bill: the expensive epoxy has high viscosity and increases the thickness of the connections.    
  
 
== Full-scale prototype tests ==
 
== Full-scale prototype tests ==
  
- Lubomir re-visited the unsolved problem that wires are not in the middle w.r.t. top and bottom cathodes. This time the long wires were scanned along their lengths. One sees (page 550) systematically that the wires are closer to the middle at the beginning of the wire going up at the middle of the chamber by up to 1.5mm. This may indicate that the cathodes are sagging. It could be due to pressure difference, gravitation, or electrostatic forces. The last two effects normally must be small. The holes on the cathode frames must eliminate the differential pressure on the cathode, but it could be that the ground plane sags and couples to the cathodes strongly in the middle. The plan is to investigate the pressure effects by changing the gas flow. The next step would be to turn the chamber upside down, but most likely at this position the chamber will not be operational. Therefore, before doing this any other ideas of what needs to be checked, are welcome.
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- Lubomir showed a new plot (page 550) demonstrating how the ratio top/bottom strip signals changes over the plane of the top chamber. One possible explanation is deformation of the cathode/ground planes due to pressure difference in the different volumes. We discussed if it will be an advantage to have the volumes of all the chambers in a package connected together, i.e. to have holes in the ground planes that are now separating the chamber volumes. Now we are testing the bottom chamber.  
 
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== Others ==
 
== Others ==
  
For the next collaboration meeting (Feb 2-3) Beni and Lubomir will decide about the FDC talks in the tracking session. Simon will talk about the tracking analyses in the off-line session.
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NO MEETING next week due to the collaboration meeting (Feb 2-3) Beni, Lubomir and Simon will have talks on the collaboration meeting.
 
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-->
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Latest revision as of 19:54, 27 January 2011

January 27, 2011 FDC meeting

Agenda

  1. Production (David)
    • Blue Crab status
    • FDC QA docs QA doc
  2. Electronics (Fernando, Chris, Roger)
    • Rigid-flex assemblies
    • Foil production status
    • Other
  3. Engineering (Bill, David)
    • Wire stringing
    • Other
  4. Full-scale prototype studies
  5. Other

Minutes

Participants: Bill, Dave, Chris, Simon, Beni, Fernando, Glenn, Roger, Eugene, and Lubomir

Production

- Dave showed recent pictures from the clean room that can be found on the M-drive: M:\facilities\Projects\Projects_100K+\Hall D FDC - Blue Crab Road Warehouse\Clean room\Construction\Photos\Construction. We will start moving in on Monday.

- Dave prepared an initial version of the FDC QA plan linked above. Pansophy data base will be used for the travelers: https://pansophy.jlab.org/pansophy/help.cfm.

Electronics

- Fernando: the first article cables were fixed and will be sent back to us.

- Rigid-flex: once more we discussed the thickness of the rigid board (18.5 mil). Bill suggested reducing this thickness, but only if it's easy and can be done in time, otherwise it is acceptable and we are not going to reject the first article. Roger will communicate with the vendor. The parts needed to test the 3M conductive tape for soldering to the cathodes have not come yet. In any case we will continue with the mass production of the rigid-flexes with bare gold contacts that later can be tinned during the stuffing.

- Roger: still waiting for the written response from Allflex to our report about the first article cathode foils.

Engineering

- Bill is working on some additional parts for the stringing system. The techs have been working with it last couple of weeks exercising different techniques. We discussed again the main issue so far, the flatness of the wire frame. Bill suggested using clamps that will be inserted between the G10 frame and the Rochacell ring. Fernando suggested a possible way to push the wire frame down from a supporting frame on the top. The way it works now is by taping the wires down to the board close to the soldering pads. This was proven to work: increase of the wire position deviations from ~10 microns to ~15 microns (sigma). Taping of all the wires is almost done and soon we will continue with gluing and soldering the wires.

- The testing of the "cheap" conductive epoxy was not very successful so far, it has high resistivity. Eugene: it might be better instead of spending time on improving the gluing technology, to use the "expensive" epoxy. Bill: the expensive epoxy has high viscosity and increases the thickness of the connections.

Full-scale prototype tests

- Lubomir showed a new plot (page 550) demonstrating how the ratio top/bottom strip signals changes over the plane of the top chamber. One possible explanation is deformation of the cathode/ground planes due to pressure difference in the different volumes. We discussed if it will be an advantage to have the volumes of all the chambers in a package connected together, i.e. to have holes in the ground planes that are now separating the chamber volumes. Now we are testing the bottom chamber.


Others

NO MEETING next week due to the collaboration meeting (Feb 2-3) Beni, Lubomir and Simon will have talks on the collaboration meeting.