Difference between revisions of "Minutes-9-15-2011"

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# Electronics update  
 
# Electronics update  
 
# Chamber testing at EEL126 (Beni)
 
# Chamber testing at EEL126 (Beni)
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# Other
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# Other: [http://www.jlab.org/Hall-D/detector/fdc/production_pictures/ latest pictures of the package]
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+
−
<!--
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= Minutes =
 
= Minutes =
  
−
Participants: Bill, Dave, Simon, Beni, Elton, Mark, and Lubomir.  
+
Participants: Eugene, Bill, Dave, Mark, Simon, Beni, Glenn, and Lubomir.  
  
 
== Production ==
 
== Production ==
  
−
- Dave: The capacitors were changed on all wire frames needed for the first production package. Wires frame #6 was populated, wires deadened and will be put in package today or tomorrow. Wire frame #7 is out of the stringing table and Chris will put the elements on it tomorrow. The last two cathodes for the first package: started putting the rigid-flexes on type-1; on type-2 the frame was glued and on Monday the Mylar foil will be glued.  
+
- Started stacking again the package; we have already installed the first cell and the first cathode of cell#2. The second cathode of cell#2 and the second wire plane are also ready for installation after replacing two wires (see explanations below). Cell#3: the wire plane is ready except that four broken resistors need to be replaced. The two cathodes for cell#3 were checked with a generator and a problem in one connector was found: attenuation of the signal on several channels; the conductive tape on that connector will be re-heated. On all the frames in this stack (except the bottom end window and wire frame) we put new O-rings, because we observed some gas leakage. All the cathodes for the first package are ready except one; it has been tensioned and the next operation is to cut the flaps.  
  
 +
- Beni asked if the problems with the conductive tape show up at the same place on the connector due to uneven pressure. No, but Bill proposed to install a manometer at the cylinder to monitor that the pressure that comes from the compressor outside. Regarding resistor breaking, we decided not to use lead bricks during the gluing of the PCB ring.
  
−
- After testing the first cell of the production package we found the following problems:
+
- Testing the first two cells in the package. The first cell that was fixed before it was tested again and all the channels were OK. Two problems on the second cell: one wire broken between the pad and the epoxy and a point source of noise inside the chamber was found. Not clear how did the wire broke since that place was covered with epoxy and then the wire was checked by the tension measurements. The noise showed up on one wire and on both cathodes, pointing to a fixed position; that's how it was identified. Both wires were replaced. It was difficult to conclude what was the source of the noise: Casey saw several kinks in that area. After the wire was removed we looked with a microscope and found a small fiber-like piece looped over the wire, but we were not sure if that was at the same place. To bubble to the two cells we had to increase the flow to 100 ccpm (compared to 20 for the first cell before) meaning some increased gas leakage.  
−
*One wire was broken at the standard place, between the pad and the epoxy. Casey fixed it already. Beni asked if this is a "standard place", how we can mitigate the problem. Dave: before soldering we started putting additional epoxy at that place that reduced the number of broken wires, so after that this is the first wire that we found broken. Beni and Bill discussed  if this was caused by a frame deformation.  
+
−
*One cathode channel didn't have a good contact; it passed the test with the diode testing card, but when we checked it with a generator the signals were attenuated. Re-heating the conductive tape for 30 sec solved the problem. However, after finding this we checked all the channels with a generator and found another bad channel. In this case re-heating for 30 sec didn't help. Casey decided to try  re-heating for 60 sec and this time it helped.
+
- There was a power outage at Blue Crab on Monday that affected mostly the AC unit for several hours.
−
*On the two wire frames that will go in the first package we found several broken resistors, some at the signal and some at the HV side. These are 1MOhm current limiting resistors. Most likely they were broken during the ring lamination when putting lead bricks on the top to make the ring flat. We were using cork pads bellow them, but Bill suggested another (polyethylene based) material. Also for the future we should avoid putting the bricks on the elements.  
+
  
−
 
+
- 55Fe source: the actual activity of the source when it arrived was 28 micro-Ci according to the manufacturer. RadCon informed us about this yesterday and they said we should wait several months till we can use it at Blue Crab. RadCon will look if there's another source available for us. Eugene proposed to attenuate the source with some material, but after the meeting RadCon clarified that the limit is on the activity not on the intensity.
−
- All the above findings suggested that we need to do more tests before stringing and before stacking the wire frames and the cathodes:
+
−
*testing the resistors on the wire frames (with an ohmmeter) before stringing.
+
−
*testing the wire channels by applying step function with a generator on the +HV and looking with a scope at the individual channels at the connector
+
−
*testing of the cathode channels can be done with a generator (suggested by Anatoly) but it will require applying the signal on the other side of the strip which is not possible for the short strips in the middle. Another way is to induce the signals on all the strips by laying a cable from the generator on the top of the cathode. This method was used now to check all the cathodes for the stack. Probably the easiest way to do it is just to measure the resistance of the contacts.
+
−
 
+
−
- The first cell (with wire frame #5) was operational for almost a week. It was conditioned in 24 hours up to +2200/-500V (~500 nA total) and never tripped. On this wire frame the capacitors were not changed but covered with Humi-seal. The question is whether we want to change the capacitors on such wire frames that are working fine. Bill: we want to change them because the solder balls could move and cause problems in the future. The problem is that there's high probability one can damage the wires especially on boards with Humi-seal on the capacitors. We should try it on an old frames (or the first cell) before making decisions. Also on four of these frames we used Epon epoxy which may turn out to be unacceptable in any case, and that we can't replace. 
+
−
 
+
−
 
+
−
- Beni and Elton stated that the priority now should be building the first package and later to decide about the capacitors. Beni also insisted we should move the second cell back to Blue Crab asap in order to understand the short between field and sense wires.  
+
  
 
== Engineering ==
 
== Engineering ==
  
−
- The modified fixture for the wire deadening will come on Monday. Other parts/tooling for the package assembly will come next week, as well.  
+
- Bill proposed a new design for the rods/pins used to assemble the package. The idea is to make their height adjustable depending on the number of cells that are in the stack. Everybody agreed that this will save effort and possible damage during assembly since the holes on the frames are very tight.  The third gusset ring will be ready by the end of next week.
  
 
== Electronics ==
 
== Electronics ==
  
−
- Information from Chris before the meeting: all rigid-flexes were tested and found 5 (out ~500) that can't be easily fixed and will be shipped back for repair. In any case we have enough for the production.
+
- Chris is in vacation; will work on the board that will bring the signals from the daughter cards outside for testing. While testing the resistors on the PCB's, Anatoly found that some percentage (~5-10%) of the resistors have lower values by 10-30%. These are current limiting resistor, but still Lubomir will discuss with Fernando if these need to be replaced.
  
−
- As discussed for the tests above we need to look at the wire and strip signals (or measure resistance) at the daughter card connectors. For that we need a card similar to the cathode testing card, same connectors on both sides but just with straight through traces to bring the signals outside of the frame. Chris will make such cards.
 
−
 
 
 
== Chamber testing at 126  ==
 
== Chamber testing at 126  ==
  
−
- Beni: done with the tests of cell #2. We should start preparing for the first package tests. Need to reorganize that space in 126, most importantly to find better place for the electronic racks. It will require re-cabling and again fight with the noise but has to be done.  
+
- Beni started rearranging the space at 126. He swapped the electronics and the gas racks and added another rack with a second VXS crate. Now there's enough space around the racks.
−
Valdimir will help.
+
 
 +
== Other ==
  
−
-->
+
- For the Lehman review next month Eugene needs new results from the production chambers. Beni explained his results about the chamber efficiency for the second cell. Lubomir will also prepare some plots from the test of the second cell using fAD125. As for the first production package, the plan is to have it ready before the review but most likely by that time still there will be no results from the tests with the DAQ.

Latest revision as of 20:06, 17 September 2011

September 15, 2011 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Status
    • First package tests (Lubomir)
  2. Engineering update (Bill)
  3. Electronics update
  4. Chamber testing at EEL126 (Beni)
  5. Other: latest pictures of the package

Minutes

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

Production

- Started stacking again the package; we have already installed the first cell and the first cathode of cell#2. The second cathode of cell#2 and the second wire plane are also ready for installation after replacing two wires (see explanations below). Cell#3: the wire plane is ready except that four broken resistors need to be replaced. The two cathodes for cell#3 were checked with a generator and a problem in one connector was found: attenuation of the signal on several channels; the conductive tape on that connector will be re-heated. On all the frames in this stack (except the bottom end window and wire frame) we put new O-rings, because we observed some gas leakage. All the cathodes for the first package are ready except one; it has been tensioned and the next operation is to cut the flaps.

- Beni asked if the problems with the conductive tape show up at the same place on the connector due to uneven pressure. No, but Bill proposed to install a manometer at the cylinder to monitor that the pressure that comes from the compressor outside. Regarding resistor breaking, we decided not to use lead bricks during the gluing of the PCB ring.

- Testing the first two cells in the package. The first cell that was fixed before it was tested again and all the channels were OK. Two problems on the second cell: one wire broken between the pad and the epoxy and a point source of noise inside the chamber was found. Not clear how did the wire broke since that place was covered with epoxy and then the wire was checked by the tension measurements. The noise showed up on one wire and on both cathodes, pointing to a fixed position; that's how it was identified. Both wires were replaced. It was difficult to conclude what was the source of the noise: Casey saw several kinks in that area. After the wire was removed we looked with a microscope and found a small fiber-like piece looped over the wire, but we were not sure if that was at the same place. To bubble to the two cells we had to increase the flow to 100 ccpm (compared to 20 for the first cell before) meaning some increased gas leakage.

- There was a power outage at Blue Crab on Monday that affected mostly the AC unit for several hours.

- 55Fe source: the actual activity of the source when it arrived was 28 micro-Ci according to the manufacturer. RadCon informed us about this yesterday and they said we should wait several months till we can use it at Blue Crab. RadCon will look if there's another source available for us. Eugene proposed to attenuate the source with some material, but after the meeting RadCon clarified that the limit is on the activity not on the intensity.

Engineering

- Bill proposed a new design for the rods/pins used to assemble the package. The idea is to make their height adjustable depending on the number of cells that are in the stack. Everybody agreed that this will save effort and possible damage during assembly since the holes on the frames are very tight. The third gusset ring will be ready by the end of next week.

Electronics

- Chris is in vacation; will work on the board that will bring the signals from the daughter cards outside for testing. While testing the resistors on the PCB's, Anatoly found that some percentage (~5-10%) of the resistors have lower values by 10-30%. These are current limiting resistor, but still Lubomir will discuss with Fernando if these need to be replaced.

Chamber testing at 126

- Beni started rearranging the space at 126. He swapped the electronics and the gas racks and added another rack with a second VXS crate. Now there's enough space around the racks.

Other

- For the Lehman review next month Eugene needs new results from the production chambers. Beni explained his results about the chamber efficiency for the second cell. Lubomir will also prepare some plots from the test of the second cell using fAD125. As for the first production package, the plan is to have it ready before the review but most likely by that time still there will be no results from the tests with the DAQ.

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