Difference between revisions of "Minutes-6-9-2011"

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June 2, 2011 FDC meeting
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June 9, 2011 FDC meeting
  
 
= Agenda =
 
= Agenda =
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#* Other
 
#* Other
 
# Electronics (Fernando, Chris)
 
# Electronics (Fernando, Chris)
−
#* PCB schematic update
+
#* PCB schematics update
 
#* Other
 
#* Other
 
# Chamber testing
 
# Chamber testing
 
#* Wire Position Measurements
 
#* Wire Position Measurements
 
# Other
 
# Other
−
 
−
<!--
 
  
 
= Minutes =
 
= Minutes =
  
−
Participants: Bill, Dave, Chris, Beni, Glenn, and Lubomir.
+
Participants: Eugene, Bill, Dave, Chris, Caleb, Beni, Simon, and Lubomir.
−
 
+
−
Short meeting since most of the people are at Blue Crab every day and know what's going on; still we discussed some issues in more detail. For the outside people I added more info about the current status. After the meeting we finished the assembly of the first chamber layer, important milestone.
+
 
   
 
   
 
== Production ==
 
== Production ==
  
−
- The first production chamber is being assembled right now. We have, from bottom to top on the assembly fixture: 9 empty cathode frames, end window (1mil mylar) with O-ring, cathode type 3 (0.5mil mylar with holes on the bottom and cathode foil on the top). Casey is putting now the O-ring on the wire plane that will be installed in the package right after the meeting. Then we will put the spacer ring (also ready except for O-rings) and then will put on the top the transparent lexan sheet. Later we will replace it with the second cathode (ready) and the second end window.
+
- End of last week we assembled the first production chamber, run gas over the weekend, on Monday applied HV and was tripping (1uA threshold) at very low voltages: ~20-30V for sense wires and somewhat higher (~30V, one sector was at -500V for short time) for field wires. Then we found ~1-10MOhm between HV and ground and practically all the pads on the PCBs, even between opposite PCBs on the wire frame that have no electrical connection. The conclusion was: the wire frame got wet (most likely the Rohacell) when it was cleaned in the ultrasonic bath. We tried to dry it with a lamp and then with a heat gun; didn't work. Then today we put it a big vacuum chamber at the Test Lab to take the moisture out. The person servicing the vacuum chamber mentioned that it went down to 10^-4 torrs for ~2hours, much slower than usual (~20min) which indicates there was a lot of moisture there. We will keep it there by tomorrow morning when we expect 10^-7 torrs. Bill: such under pressure will not damage the Rohacell.
  
−
- Cathodes: we have the third (type 3) and fourth (type 1) cathodes mechanically ready, waiting for the rigid-flexes; on the fifth cathode (type 3) the mylar will be tensioned today. By tomorrow  we will have also the second end window (2mil mylar) ready.  
+
- The good news is that the gas leakage of the first package was very low (undetectable) except at one place: one of the tube on the spacer ring. Mark Stevens was yesterday at Blue Crab explaining the procedure for gluing the gas tubing on a new spacer ring; the first one will be fixed too.  
  
−
- Wire frames: the second wire frame is being prepared now for stringing. We have also the third wire frame laminated. On the test wire plane and on the first production wire plane we tried the new procedure, ultrasonic cleaning, and it worked fine. First the planes were cleaned with Vigon, then put in the ultrasonic tank filled with distilled water where they were rotated manually.
+
- We are working now on the second chamber set. The second wire frame was strung, glued, positions measured, then the wires were soldered. (After the meeting also the tensions were measured). Tomorrow the wires will be cut and the PCBs populated. Cathodes #3 and #4 are type 3 (as #1 and #2) and ready mechanically. After testing the modified tool we will glue the rigid-flexes.
  
 +
- Starting the beginning of this week, the AC of the bay area was set to higher temperature (85 F) only over the night. Ron Bartek monitors the work of the clean room AC (settings unchanged). Eugene was concerned also about the procedures and materials that are outside of the clean room. So far the humidity there was not so high (45%) but we should monitor it constantly. To be on the safe side we decided to bring all wire frames inside the clean room to prevent the absorption of moisture in the Rohacell
 +
 
== Engineering ==
 
== Engineering ==
  
−
- Rigid-flex pressing tool: today Bill and Casey did tests using pressure indicator paper. It showed that the issues we had with the un-tinned  flexes are due to pressure not being equally applied on all the contacts. With the tinned contacts, due to increased thickness, the pressure was OK for all the test configurations. For the un-tinned contacts they tried several configurations: kapton tape only at one side of the connector (first two cathodes were done in such configuration), kapton tape over the connector, and without kapton tape. The best results were obtained with the kapton tape over the connector. In addition they tested the flatness of the shoe and turned out there's a gap in the middle. Bill will take the tool and will modify it in couple of days. In addition to make it flat, he will also reduce the width of the shoe that is now ~6mm; the first tool had 4mm shoe.  
+
- We decided not to use ultrasonic cleaning for the second wire frame. If the vacuuming will work to take out the moisture from the first chamber we may try to use the ultrasonic cleaning for the third chamber, but making sure all the holes are reliably sealed. In fact before the first production chamber, we put a testing frame (old design) in the ultrasonic bath and this frame doesn't show measurable conductivity through the Rohacell; most likely it was sealed better.  
  
−
- Wire sensing problem: at the end of last week we found by turning off all potentially vibrating devices, that the vibration is not causing this problem. As suspected before, the field wires are the problem: they are not seen by the sensor at some places. We have no problems with the old field wires. Caleb made several samples with wires marked in the problematic regions. It turned out Hall B is using exactly the same field wires but we are not aware if they had any problems with them. Important finding was that our field wires are only 2% of theirs, so if we need spare (since we have a little only) we may borrow from them.  
+
- Rigid-flex pressing tool: it's back from the machine shop and today Casey will check the flatness. The shoe was narrowed down to 4.5mm.
  
−
- After the stringing of the second chamber Bill will make some improvements in the stringing table: the new encoder and monuments will be installed. The tooling for rotating the wire frames in the ultrasonic cleaner will be ready by that time, as well.
+
- Bill is designing the end gussets that hold the package together. His proposal is to make one piece out of aluminum angle (1x1' 2mm thick). We discussed also the possibility to use Be. Eugene: it will be very expensive (1m diameter) because it's toxic when machined, but it has factor of 4 bigger radiation length. Simon will add the Al ring in the simulation to investigate the effects on the calorimeter photon registration efficiency.  
 
   
 
   
 
== Electronics ==
 
== Electronics ==
  
−
- Chris wanted to know if we have decided about the type of the rigid-flex connectors: tinned or un-tinned? As discussed above now the origin of the difference between the two is clear: just difference in the height of the contacts. After modifying the shoe of the tool we can claim for sure we understand the problem and will make a decision. As Chris pointed out in may take weeks to start the production, so we should decide soon. So far we have enough rigid-flexes for another two cathodes.
+
- Chris made the new testing card with LEDs on the top; still need a cable to use it.  
  
−
- Chris is working on the new testing card with LEDs on the top; he will have the parts next week.
+
- There was confusion when populating the PCBs: the bill of materials was in contradiction with the schematics. We populated the boards according the the bill, but it turned out the schematics is the correct one. The HV PCBs were corrected (but as it turned out we had bigger problems with the HV), so later we will correct the signal side as well. Kim created a new version of the material list and Fernando will create a traveler with the correct documentation.  
  
 
== Chamber testing ==
 
== Chamber testing ==
  
−
- Beni will come tomorrow at Blue Crab to install the gas system and start testing the first chamber there. He has all the parts/tools needed for the test.
+
- Caleb started working on the position measurement problem. His plan is to create software (Visual Basic) to track down the problem and also to improve the procedure.
  
−
-->
+
- The position measurements for the second wire frame showed sigma of ~25 microns. Few of the wires exceeded 100 even 200 microns offsets but were corrected by re-taping the wires. This is the first wire frame after the pin rail was fixed: now it doesn't show the step in the middle but some kink (change in the slope) is visible. Maybe due to the use of the stepper motor. After finishing the second wire frame Bill install the new encoder and hopefully this will fix the problem.

Latest revision as of 17:49, 15 June 2011

June 9, 2011 FDC meeting

Agenda

  1. Production (Dave)
    • First chamber assembly: HV problem
    • Spacer ring: gas leakage
    • Second set wire frame and cathodes
    • Other
  2. Engineering (Bill)
    • Vacuum chamber
    • Ultrasonic cleaning
    • Rigid-flex gluing tool
    • Other
  3. Electronics (Fernando, Chris)
    • PCB schematics update
    • Other
  4. Chamber testing
    • Wire Position Measurements
  5. Other

Minutes

Participants: Eugene, Bill, Dave, Chris, Caleb, Beni, Simon, and Lubomir.

Production

- End of last week we assembled the first production chamber, run gas over the weekend, on Monday applied HV and was tripping (1uA threshold) at very low voltages: ~20-30V for sense wires and somewhat higher (~30V, one sector was at -500V for short time) for field wires. Then we found ~1-10MOhm between HV and ground and practically all the pads on the PCBs, even between opposite PCBs on the wire frame that have no electrical connection. The conclusion was: the wire frame got wet (most likely the Rohacell) when it was cleaned in the ultrasonic bath. We tried to dry it with a lamp and then with a heat gun; didn't work. Then today we put it a big vacuum chamber at the Test Lab to take the moisture out. The person servicing the vacuum chamber mentioned that it went down to 10^-4 torrs for ~2hours, much slower than usual (~20min) which indicates there was a lot of moisture there. We will keep it there by tomorrow morning when we expect 10^-7 torrs. Bill: such under pressure will not damage the Rohacell.

- The good news is that the gas leakage of the first package was very low (undetectable) except at one place: one of the tube on the spacer ring. Mark Stevens was yesterday at Blue Crab explaining the procedure for gluing the gas tubing on a new spacer ring; the first one will be fixed too.

- We are working now on the second chamber set. The second wire frame was strung, glued, positions measured, then the wires were soldered. (After the meeting also the tensions were measured). Tomorrow the wires will be cut and the PCBs populated. Cathodes #3 and #4 are type 3 (as #1 and #2) and ready mechanically. After testing the modified tool we will glue the rigid-flexes.

- Starting the beginning of this week, the AC of the bay area was set to higher temperature (85 F) only over the night. Ron Bartek monitors the work of the clean room AC (settings unchanged). Eugene was concerned also about the procedures and materials that are outside of the clean room. So far the humidity there was not so high (45%) but we should monitor it constantly. To be on the safe side we decided to bring all wire frames inside the clean room to prevent the absorption of moisture in the Rohacell

Engineering

- We decided not to use ultrasonic cleaning for the second wire frame. If the vacuuming will work to take out the moisture from the first chamber we may try to use the ultrasonic cleaning for the third chamber, but making sure all the holes are reliably sealed. In fact before the first production chamber, we put a testing frame (old design) in the ultrasonic bath and this frame doesn't show measurable conductivity through the Rohacell; most likely it was sealed better.

- Rigid-flex pressing tool: it's back from the machine shop and today Casey will check the flatness. The shoe was narrowed down to 4.5mm.

- Bill is designing the end gussets that hold the package together. His proposal is to make one piece out of aluminum angle (1x1' 2mm thick). We discussed also the possibility to use Be. Eugene: it will be very expensive (1m diameter) because it's toxic when machined, but it has factor of 4 bigger radiation length. Simon will add the Al ring in the simulation to investigate the effects on the calorimeter photon registration efficiency.

Electronics

- Chris made the new testing card with LEDs on the top; still need a cable to use it.

- There was confusion when populating the PCBs: the bill of materials was in contradiction with the schematics. We populated the boards according the the bill, but it turned out the schematics is the correct one. The HV PCBs were corrected (but as it turned out we had bigger problems with the HV), so later we will correct the signal side as well. Kim created a new version of the material list and Fernando will create a traveler with the correct documentation.

Chamber testing

- Caleb started working on the position measurement problem. His plan is to create software (Visual Basic) to track down the problem and also to improve the procedure.

- The position measurements for the second wire frame showed sigma of ~25 microns. Few of the wires exceeded 100 even 200 microns offsets but were corrected by re-taping the wires. This is the first wire frame after the pin rail was fixed: now it doesn't show the step in the middle but some kink (change in the slope) is visible. Maybe due to the use of the stepper motor. After finishing the second wire frame Bill install the new encoder and hopefully this will fix the problem.

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