Difference between revisions of "Minutes-7-21-2011"

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July 14, 2011 FDC meeting
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July 21, 2011 FDC meeting
  
 
= Agenda =
 
= Agenda =
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# Other
 
# Other
  
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<!--
 
  
 
= Minutes =
 
= Minutes =
  
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Participants: Bill, Dave, Chris, Elton, Beni, Simon, Glenn, Caleb, and Lubomir.
+
Participants: Eugene, Bill, Dave, Chris, Beni, Simon, and Lubomir.
  
 
== Production ==
 
== Production ==
  
−
- Dave (see  the construction tracking): Cell#3 is almost ready, just second phase elements has to be put on the wire frame. The cathodes on cell#4 are ready except the flaps on the type-2 cathode. Now the techs are working on the cathodes for cell#5 using the two tensioning tools. We decided to postpone the wire frame production till we make a decision how to solve the HV problem, discussed later.  
+
- Dave (see  the construction tracking): Continued with stringing wire frame#4. Wire frame#3 is waiting for soldering second phase component (Chris will do it together with Tina). Cell#5: one cathode ready, working on the second (type 2) cathode. Cell#6: working on the first cathode.  
  
−
- Wire deadening: waiting for the chemicals needed. We will use the square lexan plate for tooling, but Bill will order another plate to be used for this procedure. Bill talking to Brian learned that the chemicals have to be neutralized at the end of the procedure and that was not always done before when experimenting on a testing wire frame. We will try the deadening first on several testing frames before using a production one. Dave with Al's help is finishing the micro-controller and also working on a way to bypass the 1M resistors on each wire channel.
+
- Waiting for the chemicals for the wire deadening; probably will start testing the procedure beginning of next week. Bill: what is the wire diameter needed to deaden the wire? Lubomir: according to Garfield if we make sense wires 40um signal drops by factor of 40, for 60um - factor of 400, and for 80um -factor of 2,700. After some discussions, Bill will look what is the sagging effect of thickening the wires and Lubomir will estimate the suppression factor that we need.
  
−
== Engineering ==
+
- The PR for the iron source was submitted waiting for the RadCon signature, probably at the beginning of the next week.
  
−
- Bill ordered the strong-back for the packages. One option would be to attach it to the package after it is assembled, and the other is just to assemble the package on the top of the strong-back in which case we need several of them. We want to have flatness on the chambers better than 200 microns, but Bill says with the material budget we have it is hardly possible. Measurements on the gusset ring only show deviation from flat up to 150 microns. The biggest deviation correlates with some scratches made in the production and Bill wants to re-enforce that place with epoxied fiber.  
+
- Investigating the sources of the high leakage currents; applied HV on the signal side of a wire frame without wires. In some of the measurements we found the current is too high because of the bad connection between the Cu tape (on which HV is applied) and the wire pads. The lowest current we got is ~10nA for one board when the capacitors are covered with Humiseal, and close to 0nA when capacitors were removed cleaned and then soldered without flux, latter done by Anatoly who put solder on the capacitors and pads, cleaned the flux and then solder the capacitors just by heating. According to Chris this is not a certified way for soldering because of possible oxyde layer.
  
−
- While the stringing table is not used for now, Bill will modify the strong-back to correct for the flatness deviations. Additional holes needed for the frame ejection plate have to be drilled, as well.
+
- Conclusions for the HV problem: the capacitors itself are not the source of the leakage. Some small amount of flux found below some of the capacitors indicate that this might be a problem but this effect is reduced by covering it with humiseal that actually penetrates also below the capacitors. The humiseal helps also to cover possible sharp places on the capacitor plates that otherwise in gas would produce sparks. Lubomir proposed a procedure for testing the wire frames just before stringing. If all the leakage current of the caps is less than few tens nA the caps will be covered with humiseal, otherwise the caps showing big currents will be removed, the place cleaned and then the caps will be soldered back.
  
−
== Electronics ==
+
- Eugene: we can't continue with the wire frame production until it is proven the chamber can hold HV for several weeks. Also, using humiseal is allowed only if it has been used already in drift chambers. If not, we have to do our own tests including irradiation. According to Fernando humiseal has been used in Hall B chambers but outside of the gas volume. Our prototype has a lot of humiseal inside but it has not been tested with radiation. Humiseal is also rated by NASA as low outgassing.
  
−
- Lubomir and Anatoly did some tests to study the currents through the HV capacitors. At Blue Crab, one wire frame without wires was put in a gas volume (same 40/60 Ar/CO2) and HV was applied on the signal boards between the wire pads (connected with Cu tape) and the ground. The conditioning of this "wireless" chamber turned out to be very similar to the behavior of the second cell and maybe even worse. After almost a week we could reach only ~1.5kV while limiting the current below 1uA for the whole chamber. This indicates that the HV problems we had with cell#2 could be related to the capacitors on the signal boards.
+
- We decided first to investigate if there are examples of using humiseal in drift chambers. If not, we will have to do our own tests irradiating the chamber but unfortunately the accelerator is now down. We will look also for other ways to solve the HV problem. For that we will use different wire frames that we have now: some are covered with humiseal, some were cleaned and then soldered without flux.
  
−
- Fernando and Chris did similar tests with one signal board in 117. Initially the current was huge, few hundred uA at 1kV. Then Fernando suggested to cover the capacitors with humiseal and that helped. Initially the current was also high but on the next day it went down to ~13uA at 2kV for the whole board.
+
== Engineering ==
  
−
- Beni: these currents are much bigger than on the prototype and we should replace the HV capacitors with better ones and see if this will help. Elton: there were problems with the HV capacitors for the FCAL bases and they had to change them. We discussed how to proceed, certainly we need to know the origin of the currents. These measurements depend on the humidity, but the capacitors on the signal board are covered with humiseal. So, Chris will measure the current on each capacitor and depending on the results will replace those with high current with capacitors rated for higher voltage. We will do similar tests with the frame at Blue Crab: will cover it with humiseal and then, after conditioning, will identify the capacitors with highest current and eventually replace them.  
+
- Bill will be working on the spacer between packages, but nos is busy with the tagger. Bill made the wire frame strong-back flatter: from +/-35/1000" now it's down to +/-11/1000".  
  
−
== Chamber testing ==
+
== Electronics ==
  
−
- Lubomir showed results (page 569 FDC logbook) for the strip resolution on cell#1 using fADC: it is below 200 microns and similar to the resolution obtained with the prototype.
+
- Chris: within two weeks we will have all the signal cables. Chris is constantly testing them: so far only one failure.  
  
−
- Beni is testing now the cell#1 with external tracking and using discriminator cards with F1TDC and CAEN ADC for the cathodes. His first results about the strip resolution are similar to the above. 
+
== Chamber testing ==
−
 
+
−
- To estimate the wire resolution on the prototype we used the angle reconstructed from the external chamber (even with poor coordinate resolution the base is big enough to have good angular resolution) and also used two wire frames with parallel wires. Simon will work on the code to estimate the resolution when the wires are not parallel to test the whole package.
+
−
 
+
−
== Other ==
+
−
 
+
−
- We looked again at the FDC naming convention (see link above) that we discussed already a year ago and was used for labeling the PCBs and foils. We agreed on it. Simon will implement it also in the off-line code, where appropriate.
+
  
−
-->
+
- Beni showed some preliminary results (pgae 570 in the FDC logbook) from testing the first cell using external tracking. The drift time distribution doesn't look like the one for 90/10 Ar/CO2 gas mxiture but most like 80/20 and this is due to the very low CO2 rate that can't be controlled accurately. Therefore,  Beni will do tests now with 40/60.

Latest revision as of 15:39, 22 July 2011

July 21, 2011 FDC meeting

Agenda

  1. Production Construction Tracking (Dave)
    • Status
    • HV tests: results, testing procedures (Lubomir)
    • Other: wire deadening, iron source
  2. Engineering update (Bill)
  3. Electronics update (Chris)
  4. Chamber testing at EEL126
    • Tests with external tracking (Beni)
  5. Other


Minutes

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

Production

- Dave (see the construction tracking): Continued with stringing wire frame#4. Wire frame#3 is waiting for soldering second phase component (Chris will do it together with Tina). Cell#5: one cathode ready, working on the second (type 2) cathode. Cell#6: working on the first cathode.

- Waiting for the chemicals for the wire deadening; probably will start testing the procedure beginning of next week. Bill: what is the wire diameter needed to deaden the wire? Lubomir: according to Garfield if we make sense wires 40um signal drops by factor of 40, for 60um - factor of 400, and for 80um -factor of 2,700. After some discussions, Bill will look what is the sagging effect of thickening the wires and Lubomir will estimate the suppression factor that we need.

- The PR for the iron source was submitted waiting for the RadCon signature, probably at the beginning of the next week.

- Investigating the sources of the high leakage currents; applied HV on the signal side of a wire frame without wires. In some of the measurements we found the current is too high because of the bad connection between the Cu tape (on which HV is applied) and the wire pads. The lowest current we got is ~10nA for one board when the capacitors are covered with Humiseal, and close to 0nA when capacitors were removed cleaned and then soldered without flux, latter done by Anatoly who put solder on the capacitors and pads, cleaned the flux and then solder the capacitors just by heating. According to Chris this is not a certified way for soldering because of possible oxyde layer.

- Conclusions for the HV problem: the capacitors itself are not the source of the leakage. Some small amount of flux found below some of the capacitors indicate that this might be a problem but this effect is reduced by covering it with humiseal that actually penetrates also below the capacitors. The humiseal helps also to cover possible sharp places on the capacitor plates that otherwise in gas would produce sparks. Lubomir proposed a procedure for testing the wire frames just before stringing. If all the leakage current of the caps is less than few tens nA the caps will be covered with humiseal, otherwise the caps showing big currents will be removed, the place cleaned and then the caps will be soldered back.

- Eugene: we can't continue with the wire frame production until it is proven the chamber can hold HV for several weeks. Also, using humiseal is allowed only if it has been used already in drift chambers. If not, we have to do our own tests including irradiation. According to Fernando humiseal has been used in Hall B chambers but outside of the gas volume. Our prototype has a lot of humiseal inside but it has not been tested with radiation. Humiseal is also rated by NASA as low outgassing.

- We decided first to investigate if there are examples of using humiseal in drift chambers. If not, we will have to do our own tests irradiating the chamber but unfortunately the accelerator is now down. We will look also for other ways to solve the HV problem. For that we will use different wire frames that we have now: some are covered with humiseal, some were cleaned and then soldered without flux.

Engineering

- Bill will be working on the spacer between packages, but nos is busy with the tagger. Bill made the wire frame strong-back flatter: from +/-35/1000" now it's down to +/-11/1000".

Electronics

- Chris: within two weeks we will have all the signal cables. Chris is constantly testing them: so far only one failure.

Chamber testing

- Beni showed some preliminary results (pgae 570 in the FDC logbook) from testing the first cell using external tracking. The drift time distribution doesn't look like the one for 90/10 Ar/CO2 gas mxiture but most like 80/20 and this is due to the very low CO2 rate that can't be controlled accurately. Therefore, Beni will do tests now with 40/60.

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