Difference between revisions of "Minutes-4-12-2012"

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# Electronics update (Chris)
 
# Electronics update (Chris)
 
# Other
 
# Other
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= Minutes =
 
= Minutes =
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== Production ==
 
== Production ==
  
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- Dave: Chris put components on two wire planes for package #3, they remain to be deadened. Anatoly is gluing daughter cards on cathodes for package #4. One end window for package #4 that was recently made has a wavy mylar surface. We suspect the surface of the transfer ring was slippery, since before it was used to tension clear mylar for the gusset ring. The rule will be always to sand the transfer ring before using for the end windows. We will have to redo the end window: first sand the old mylar and tension it again. Tomorrow, after the first cell of package #3 is assembled, we will resume stringing wire boards; stringing was suspended for several weeks due to the oxygen problem.
+
- Dave: working on cathodes #44 and #45 for the fourth package, tension measurements today on wire plane #25 (second for fourth package), three wire planes waiting for deadening. The foil of the end window #10 (that was wavy) was removed: it turned out, by unknown reasons, the epoxy didn't cure after many days and the surface was still tacky. New foil will be tensioned.
−
 
+
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-  On Monday we disassembled the third package. The old O-rings of the two end windows and the wire frame for the first cell were removed using aceton to clean the super glue. Casey invented a cover for the wires to prevent aceton spills. Then the grooves were double coated with Hysol, Viton O-rings were installed today and we assembled the first cell right after the meeting. Dave wrote the procedures for the replacement of the O-rings, waiting now for signatures. The depth of the groove after coating: according to Bill the depth should not be reduced by more than 10 mils; Dave measured it: 1-5 mils.  
+
−
 
+
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- Two or three type-1 frames have to be "converted" into type-2. Bill explained how to do this: put Scotchweld in the groove, use razor blade to level it and after curing possibly sand it.  
+
  
 
== Results from the oxygen studies ==
 
== Results from the oxygen studies ==
  
−
- Lubomir started working on a document describing the oxygen tests. The most important table with the measurements using the testing chamber is linked above. Important step from configuration #7 to #8: only the G10 groove was coated resulting in oxygen change from 1400 ppm to 280 ppm. To estimate the change factor we have to subtract the oxygen in the supply line. Beni measured it before using T-connector right at the chamber inlet: 200ppm. Lubomir measured it again by directly plugging the supply line into the sensor using the same tubing: 50ppm. The difference might be due to contamination from the chamber itself when using T-connector, or due to the higher pressure that is created when you plug directly the supply.
+
- Starting from configuration 12 in the table linked above, we are performing oxygen measurements at Blue Crab; Brooks gas system with two flow controllers and the oxygen sensor were moved there. Before looking into the results there was a long discussion about the way the measurements are done. We estimate the relative uncertainties of the measurements to be ~200 ppm, in addition we may have an overall factor of up to 30%.
  
−
- Eugene: what's the acceptable oxygen level; must be <0.05%, but in the prototype we had ~0.1% and was still operational. Assuming we will have ~300ppm per cell at 200cc/min then we will have 1800ppm for the whole package, but if operating at 400cc/min for the whole package it will be 900ppm or 0.09%. However, for this estimation we have to subtract the contribution from the oxygen in the supply gas. More realistic estimation can be done at Blue Crab with the real package.
+
- The first production cell with new Viton O-rings was installed and oxygen was measured (it took 4 days) 500-600 ppm at 330 ccpm gas flow and 900-1000 ppm at 220 ccpm. For comparison, the four cells with the original EPDM O-rings had ~7,000 ppm at 330 ccpm gas flow, so the new results show an improvement of more than a factor of 3, but a factor of ~2 worse than in the testing chamber. There was a significant leak, that later turned out to be caused by a small piece of Kapton tape on the top of the O-ring. Since yesterday, we replaced the top end window and cathode type-3 with a cathode type-1 and Lexan sheet. This is to investigate to role of the flatness and possible frame deformation.  
  
−
- Results of the oxygen studies: contamination is an effect of a combination of the O-ring type and the surfaces around the O-ring. When g10 groove coated there was no difference which O-ring used, but with the plastic spacer EPDM showed higher oxygen. Viton and Buna-N showed no difference; Viton was chosen for the production due to reports of outgassing for Buna-N. We want to continue the studies to understand the mechanism of the oxygen permeation, but later when we have time.
+
- Due to the difficulties to maintain clean and flat surfaces needed for the Viton O-rings, we started looking again at the possibilities to use EPDM. We set up at Blue Crab a second oxygen testing place. There we started with the simplest configuration: spacer ring with EPDM O-rings between two Lexan plates: 220 ppm oxygen (to be compared to 400 ppm we measured before). As a next step, yesterday we added to the same configuration cathode type-1 with EPDM O-ring, expecting to have the final results tomorrow.
  
−
- Oxygen sensor system was moved to Blue Crab and the four cells of the package #3 were tested at about the same flow of 200cc/min (measured with rotarmeter): ~7000ppm, which is in agreement with ~10000ppm for the whole package #1. Bill proposed and Beni agreed to move the new gas system (Brooks)
+
- Even we had a factor of 3 improvement, we expect ~0.5% oxygen for the whole package at 220ccpm. We would need a factor of 5 higher flow to have the oxygen below 0.1% what we had in the prototype. Another way to reduce the effect of the oxygen is to use less CO2, either going to 90/10 gas mixture or using methane instead of (some part of) CO2. Eugene: using organic gases may cause aging, but in Hall A where the rates are much higher they have used ethane. In any case, Eugene, Bill, Beni insisted that we don't want to be constrained by the gas and we should continue to fight for lower oxygen. Bill proposed to investigate the use of Apiezon  (vacuum grease) on the O-rings. We will try it tomorrow with the EPDM O-rings on the spacer ring.
−
to Blue Crab to better control the flow, while using the old MKS at JLab.
+
  
 
== Engineering ==
 
== Engineering ==
  
−
- Bill is finalizing the fiducial scheme: will have 4 fiducial holders on each package visible at all times. Difficulties finding non-magnetic low-mass materials. Eugene and Beni had different suggestions especially concerning the z-position determination. Bill will coordinate his plan with the survey group. Bill is working also on the spacer between the packages, decided to have 3 supporting rods instead of 4, related to the fiducial scheme and other issues.  
+
- Bill did Ansys analyses of the frame deformations with Viton O-rings (see plots attached above). The maximum frame deformation is less than 3mils, this is to be compared to 10 mils compression. It means in case of flat surfaces it will always seal the gas, however the compression will vary 30% or more in case of uneven surfaces.  
 +
 
 +
- Bill is preparing a presentation for the fiducial scheme.
  
 
== Electronics ==
 
== Electronics ==
  
−
- Chris: there's a plan how to do the grounding of the packages. It's time now to work on this: Chris and Fernando will start testing the grounding on Monday. The first package which will be available for testing in 126 till the third package is moved there, in about a month and a half.
+
- Chris is ready to start installing the grounding on the first package. After the meeting we were at 126 looking into this. The parts for the ground cable connections have come and Beni will try them on the first package.
−
 
+
−
== Possibilities for cluster counting ==
+
−
 
+
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- There will be a workshop on the GlueX detector upgrade, especially on PID detectors. Lubomir presented an idea to use cluster counting technique for PID with an FDC-like detector filled with He-based gas mixture (slides are attached above). He gas is needed for low cluster density and low drift velocity to match the fADC125 and fADC250 bandwidths. On the other hand, to have enough statistics a wide (4cm) cell  with ~3cm homogeneous filed is proposed. Full simulations of the signals taking into account also the electronics response functions, were performed using Garfield code (v.9). Assuming two packages, each with 8 cells (placed in between FDC1, FDC2, and FDC3 packages), one can separate pi from K in the relativistic rise with ~2 sigmas if using fADC125 and ~2.5 sigmas  with fADC250. Advantages discussed: higher angular acceptance due to proximity to the target, lower mass (?) and additional tracking may improve momentum resolution, can be built using FDC design and materials with some modifications. Disadvantages: lower separating power than Cherenkov or TOF (can be used complementary to them), requires single electron sensitivity, He leakage (Eugene: can be blown away from the TOF and FCAL), additional cables (Bill: will be a big problem). Beni: huge drift times up to 6-7 microsec; Lubomir: that's why we have strips that will see the same specific cluster pattern and will disentangle events overlapping on the same wire. Eugene pointed to several experiments that have used cluster counting technique.
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--->
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Latest revision as of 18:45, 12 April 2012

April 12, 2012 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Production status
  2. Results from the oxygen studies (Lubomir)
    • First production cell with Viton O-rings
    • New tests with EPDM
  3. Engineering update (Bill)
  4. Electronics update (Chris)
  5. Other

Minutes

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

Production

- Dave: working on cathodes #44 and #45 for the fourth package, tension measurements today on wire plane #25 (second for fourth package), three wire planes waiting for deadening. The foil of the end window #10 (that was wavy) was removed: it turned out, by unknown reasons, the epoxy didn't cure after many days and the surface was still tacky. New foil will be tensioned.

Results from the oxygen studies

- Starting from configuration 12 in the table linked above, we are performing oxygen measurements at Blue Crab; Brooks gas system with two flow controllers and the oxygen sensor were moved there. Before looking into the results there was a long discussion about the way the measurements are done. We estimate the relative uncertainties of the measurements to be ~200 ppm, in addition we may have an overall factor of up to 30%.

- The first production cell with new Viton O-rings was installed and oxygen was measured (it took 4 days) 500-600 ppm at 330 ccpm gas flow and 900-1000 ppm at 220 ccpm. For comparison, the four cells with the original EPDM O-rings had ~7,000 ppm at 330 ccpm gas flow, so the new results show an improvement of more than a factor of 3, but a factor of ~2 worse than in the testing chamber. There was a significant leak, that later turned out to be caused by a small piece of Kapton tape on the top of the O-ring. Since yesterday, we replaced the top end window and cathode type-3 with a cathode type-1 and Lexan sheet. This is to investigate to role of the flatness and possible frame deformation.

- Due to the difficulties to maintain clean and flat surfaces needed for the Viton O-rings, we started looking again at the possibilities to use EPDM. We set up at Blue Crab a second oxygen testing place. There we started with the simplest configuration: spacer ring with EPDM O-rings between two Lexan plates: 220 ppm oxygen (to be compared to 400 ppm we measured before). As a next step, yesterday we added to the same configuration cathode type-1 with EPDM O-ring, expecting to have the final results tomorrow.

- Even we had a factor of 3 improvement, we expect ~0.5% oxygen for the whole package at 220ccpm. We would need a factor of 5 higher flow to have the oxygen below 0.1% what we had in the prototype. Another way to reduce the effect of the oxygen is to use less CO2, either going to 90/10 gas mixture or using methane instead of (some part of) CO2. Eugene: using organic gases may cause aging, but in Hall A where the rates are much higher they have used ethane. In any case, Eugene, Bill, Beni insisted that we don't want to be constrained by the gas and we should continue to fight for lower oxygen. Bill proposed to investigate the use of Apiezon (vacuum grease) on the O-rings. We will try it tomorrow with the EPDM O-rings on the spacer ring.

Engineering

- Bill did Ansys analyses of the frame deformations with Viton O-rings (see plots attached above). The maximum frame deformation is less than 3mils, this is to be compared to 10 mils compression. It means in case of flat surfaces it will always seal the gas, however the compression will vary 30% or more in case of uneven surfaces.

- Bill is preparing a presentation for the fiducial scheme.

Electronics

- Chris is ready to start installing the grounding on the first package. After the meeting we were at 126 looking into this. The parts for the ground cable connections have come and Beni will try them on the first package.

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