Difference between revisions of "Minutes-7-1-2010"

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#* tests with fADC [http://www.jlab.org/Hall-D/detector/fdc/tests_full_scale_prototype/DTvsMeanMaxPlusGarfieldOxygen0.1pc.pdf evidence for O2 contamination], [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, page 503] (Lubomir)
 
#* tests with fADC [http://www.jlab.org/Hall-D/detector/fdc/tests_full_scale_prototype/DTvsMeanMaxPlusGarfieldOxygen0.1pc.pdf evidence for O2 contamination], [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, page 503] (Lubomir)
 
#* oxygen contamination measurements  [http://www.jlab.org/Hall-D/software/wiki/index.php/Image:Halld_gas_systemB_v2.gif Beni's scheme]
 
#* oxygen contamination measurements  [http://www.jlab.org/Hall-D/software/wiki/index.php/Image:Halld_gas_systemB_v2.gif Beni's scheme]
−
#* cosmic tests [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, pages 501 - 502]
+
#* cosmic tests (Lubomir for Beni) [http://www.jlab.org/Hall-D/detector/fdclog/ FDC Log Book, pages 501 - 502]
 
# Other
 
# Other
  
−
<!--
+
 
−
+
 
= Minutes =
 
= Minutes =
−
Participants: Bill, Glenn, Casey, Roger, Mark, Fernando, Beni, Simon, and Lubomir.
+
Participants: Bill, Roger, Mark, Simon, Casey, Bob, and Lubomir
 +
 
 +
(A relatively short meeting with some of the key players in vacations, still there were some important and useful discussions) 
  
 
== Production ==         
 
== Production ==         
  
−
- Bill: the PR for the clean room is in place but not for the ACs. We will need the AC, the one for the whole bay area, to start moving there some stuff and do some dirty work that doesn't require clean environment. Teresa Danforth is the person to be contacted and Glenn will help us in that.
+
- Bill: the PR for the clean room is awaiting Teresa Danforth's signature (it's a vacation time). Bill placed a PR (that is signed already) for two granite tables with wheels to be delivered directly in 727 B.C. We will need also in total 11 formica tables for the production. Bill looked already to find some surplus tables. We could take one or two from 126. Before purchasing the rest ($500 each) we will look around to find some. On some of the tables we must be able to put 700-800lb.  
−
 
+
−
- Bill: the cathode production plan is in a good shape: Fast Track procedure will be posted soon. The wire production planing will require more information since we have not done the stringing. Therefore, first we need to start setting up the fixtures from UVA and exercising and then clarify the procedure.
+
−
 
+
−
- We will set up the stringing initially in the tent in 126. The other option, F117, is no longer an option since there's not enough space. We decided to use the granite table in 126 for stringing. We are going to put wheels on that table. For the cathode production we will need another two granite tables. Lubomir: According to Eugene there are money for equipment so that we can buy two granite table right now. Glenn confirmed that and said that he could sign for Eugene, who is away from JLab till July 7. The plan is to put the tables directly in 727 B.C.  
+
−
 
+
−
== Electronics ==
+
−
 
+
−
- fADC125: Lubomir did further studies of the cutoff seen in the spectra from the wires. As suggested by Gerard on the last meeting now a quadratic interpolation is used to find the maximum from the fADC samples. At page 498 in the FDC logbook, shown are the maximum signal distributions separately for all the channels. The cutoff position varies from channel to channel somehow  and probably this is the reason we don't see a good peak at the saturation region. Fernando asked if there's a peak in the spectra for the individual channels. Lubomir: there's not enough statistics to see clearly the peaks channel by channel. The spectra from the strips look OK, the signals extend up to 16000 fADC units, the 14bit limit of the fADC. Lubomir will use the new scope and the differential probe to histogram the signals from the wire cards directly and see if there's a saturation.
+
  
−
- Bill proposed a modification of the cathode production procedure: cutting the foil from the transfer ring will be done not at the transfer ring I.D. position but at a larger (by several inches) radius. This will allow to flap the copper foil over the whole periphery of the cathode ring to improve the grounding connections. Thus, no modifications of the cathode g10 ring are needed. Everybody is happy with the new design. The back of the cards will be glued on the copper foil with conductive epoxy. The aluminum ground foil will be glued at one side to the cathode copper foil and Bill proposed to use conductive ink to connect the other side of the aluminum foil to the cathode. Fernando: conductive ink may not be the right choice, we will think about other options.
+
- Bill placed a PR for the g10 wire frames (30 pieces); the goal is to have them by middle of September. The template for the rochacell rings will be ready next week. The plan is to have two students (working now with Mark) working on the rochacell. Mark asked where to store the rings. Bill prefers to store them on a flat surface, maybe table. We will look to find some space for storage. Lubomir: today we got 6 more feet in EEL 126 from Hall C. After coordinating with Dave Mack, we rearranged their tables. We will use the extra space also for a new rack for the new gas equipment.
  
−
- Fernando will be in vacations next week; the extra ground cards we need to put the cathodes of the second layer on ground, will be ready on Friday.  
+
- Bill started working on the wire stringing fixtures. We agree that this work has highest priority right now. Bill discussed the way the wires will be pushed down locally, close to the soldering pads. His idea is to use a diffraction plate with grooves: 50 grooves/mm with about 10 microns depth. The grooves will keep the wires at the same spacing while pushing them down.
  
 
== Cathode redesign ==
 
== Cathode redesign ==
  
−
- Roger has prepared the drawings of the cathode foils according to the Bill's modifications from the last week, but with the change of the procedure the flaps at the periphery are not needed. Instead, Bill asked  for marks to be placed at the periphery to cut the foil. Some of the cutting positions are fixed by the cards, the other positions are not so important. Roger also showed his modifications at the connector region to make sure they are OK. He showed also the modified daughter card with a ground on the back of the card so that it can be glued to the cathode copper foil. Roger will work on the modifications that were proposed today by Bill.  
+
- Roger prepared the drawings according to the modifications from the last week: increased O.D. with flaps to improve the grounding. Except for few minor modifications (extra flaps in the areas without cards) the design is ready to go, hopefully next week. Roger will send the design to the vendor. We discussed what our requirements will be. Bill suggested to ask for prices: 1) for 60 cathode foils and also 2) if we use the whole material for about 120 foils. We will have 4 foils in the first article and then 4-6 weeks time to check them and start the rest. We discussed how to transport and store the foils. Bill suggested to have them stored in rolls. Mark had suggestions about the material to separate the foils in the rolls.
 
    
 
    
 
== Full-scale prototype test results  ==
 
== Full-scale prototype test results  ==
  
−
- Lubomir is analyzing the FADC data from the last week. Ther results are posted at the FDC logbook, pages 494-500. Shown are the areas that were covered by the test, by overlapping the three cards (for the wires, top strips, and bottom strips) at different positions. While the resolutions from the strips are OK, there are several problems with the results. The wire position as reconstructed from the ratio of the total top to bottom charge is shown at page 499. The wires are closer to the top at the middle of the chamber and closer to the middle between to two cathodes, at the shortest wire side. The wire position variations are up to 1mm. There are no visible variations along the wires within the +/-12cm covered by these tests. People asked if we can turn the chamber other way around to see if there are any gravitational effects. Lubomir: the chamber will not work after such a procedure because of the dust inside; can try this only at the end of the tests. Other possibilities, like frame deformation during the wire winding, were also discussed. The easiest test to be done is probably to scan the wires over their entire length, but requires many different positions of the cathode cards. At page 500, shown is the mean maximum signal from the wires, as a function of the position on the chamber. There's some inhomogeneity in the distribution, representing the gas gain, that has to be further studied. The speculation is that it is caused by the gas leakage. Bill asked if we can study this with an oxygen sensor. Beni: we got one but we need a pump at the output of the chamber because of the high impedance of that device.  
+
- Lubomir showed a [http://www.jlab.org/Hall-D/detector/fdc/tests_full_scale_prototype/DTvsMeanMaxPlusGarfieldOxygen0.1pc.pdf plot]: the mean signal vs drift time. One can see that the signal drops with the drift time. Normally this shouldn't happen: the electrons drift and, close to the sense wire, they are multiplied, so that the gain doesn't depend on the drift time. A possible explanation: the electrons while drifting can be attached to electronegative gas molecules. To check this, Garfield simulations were done adding small percentages of oxygen contamination in the gas mixture. The red dots in the plot represent the Garfield results with 0.1% oxygen contamination. The good agreement suggest that probably we have some oxygen in the chamber. Without oxygen, the Garfield simulations show that the signals do not change with the drift time, except for very small drift times.
  
−
- Beni: working now with two layers and two wire cards; need more ground cards to put the cathodes of the two layers on ground. The plan is to test also an old wire card that will go to CMU for their studies. Previous results, posted at page 492 of the logbook, show that the signals on the top strips are bigger than on the bottom for the middle layer too. Beni swapped the top/bottom cards to eliminate the gain differences in the electronics. Beni did also gain calibrations channel by channel using test pulses at the front of the cards. He needed 10V (actually ~3V because of signal splitting) test pulses to see reasonable signals (~50mV) out of the cards. Fernando will look into that after the meeting. Including the gain calibration in the data analysis doesn't improve the results so far.
+
- We want to measure the oxygen contamination in the full scale prototype to make sure we understand the problem. Then, the plan is to measure the oxygen from the new design mechanical prototype, to be sure there's no oxygen there. If the problem really is in the oxygen contamination, then without it, we can expect to reach the plateau at about 75-100V ( a factor of ~2 in the gain) lower voltage. This will make also the dynamic range of the signals narrower. To test this we can use the new oxygen sensor, but before that we will try with the old one. We have to pump the gas because of the high impedance of the sensors, but the problem is how to regulate the flow through the sensor so that it doesn't disturb the flow through the chamber. We will go with the Beni's scheme, linked above, in which instead of the rotameter in front of the sensor we will use the current mass flow controller. The latter being used now in the gas system will be replaced by our new mass flow controller. The plan is to install the new gas equipment in a separate rack so that it can go altogether eventually to the shed in the hall. Brian Cross gave us a small pump that can be used in the above scheme.  
  
−
-->
+
- Beni prepared several plots, linked above, showing the drift time resolution. Two layers were used with the wires parallel. In one case the drift time in the two layers were compared but for tracks within a plane perpendicular to the layers and parallel to the wires. In the second case Beni included one of the layers in the track reconstruction and look at the predicted hit in the other layer. In both cases he got a resolution of about 200 microns which is encouraging.

Latest revision as of 18:44, 1 July 2010

July 1, 2010 FDC meeting

Tentative Agenda

  1. Production
    • 727 B.C. status
    • wire frame production plans
    • plans for wire stringing in 126
  2. Cathode redesign: finalizing (Roger, Bill)
  3. Full-scale prototype tests
  4. Other


Minutes

Participants: Bill, Roger, Mark, Simon, Casey, Bob, and Lubomir

(A relatively short meeting with some of the key players in vacations, still there were some important and useful discussions)

Production

- Bill: the PR for the clean room is awaiting Teresa Danforth's signature (it's a vacation time). Bill placed a PR (that is signed already) for two granite tables with wheels to be delivered directly in 727 B.C. We will need also in total 11 formica tables for the production. Bill looked already to find some surplus tables. We could take one or two from 126. Before purchasing the rest ($500 each) we will look around to find some. On some of the tables we must be able to put 700-800lb.

- Bill placed a PR for the g10 wire frames (30 pieces); the goal is to have them by middle of September. The template for the rochacell rings will be ready next week. The plan is to have two students (working now with Mark) working on the rochacell. Mark asked where to store the rings. Bill prefers to store them on a flat surface, maybe table. We will look to find some space for storage. Lubomir: today we got 6 more feet in EEL 126 from Hall C. After coordinating with Dave Mack, we rearranged their tables. We will use the extra space also for a new rack for the new gas equipment.

- Bill started working on the wire stringing fixtures. We agree that this work has highest priority right now. Bill discussed the way the wires will be pushed down locally, close to the soldering pads. His idea is to use a diffraction plate with grooves: 50 grooves/mm with about 10 microns depth. The grooves will keep the wires at the same spacing while pushing them down.

Cathode redesign

- Roger prepared the drawings according to the modifications from the last week: increased O.D. with flaps to improve the grounding. Except for few minor modifications (extra flaps in the areas without cards) the design is ready to go, hopefully next week. Roger will send the design to the vendor. We discussed what our requirements will be. Bill suggested to ask for prices: 1) for 60 cathode foils and also 2) if we use the whole material for about 120 foils. We will have 4 foils in the first article and then 4-6 weeks time to check them and start the rest. We discussed how to transport and store the foils. Bill suggested to have them stored in rolls. Mark had suggestions about the material to separate the foils in the rolls.

Full-scale prototype test results

- Lubomir showed a plot: the mean signal vs drift time. One can see that the signal drops with the drift time. Normally this shouldn't happen: the electrons drift and, close to the sense wire, they are multiplied, so that the gain doesn't depend on the drift time. A possible explanation: the electrons while drifting can be attached to electronegative gas molecules. To check this, Garfield simulations were done adding small percentages of oxygen contamination in the gas mixture. The red dots in the plot represent the Garfield results with 0.1% oxygen contamination. The good agreement suggest that probably we have some oxygen in the chamber. Without oxygen, the Garfield simulations show that the signals do not change with the drift time, except for very small drift times.

- We want to measure the oxygen contamination in the full scale prototype to make sure we understand the problem. Then, the plan is to measure the oxygen from the new design mechanical prototype, to be sure there's no oxygen there. If the problem really is in the oxygen contamination, then without it, we can expect to reach the plateau at about 75-100V ( a factor of ~2 in the gain) lower voltage. This will make also the dynamic range of the signals narrower. To test this we can use the new oxygen sensor, but before that we will try with the old one. We have to pump the gas because of the high impedance of the sensors, but the problem is how to regulate the flow through the sensor so that it doesn't disturb the flow through the chamber. We will go with the Beni's scheme, linked above, in which instead of the rotameter in front of the sensor we will use the current mass flow controller. The latter being used now in the gas system will be replaced by our new mass flow controller. The plan is to install the new gas equipment in a separate rack so that it can go altogether eventually to the shed in the hall. Brian Cross gave us a small pump that can be used in the above scheme.

- Beni prepared several plots, linked above, showing the drift time resolution. Two layers were used with the wires parallel. In one case the drift time in the two layers were compared but for tracks within a plane perpendicular to the layers and parallel to the wires. In the second case Beni included one of the layers in the track reconstruction and look at the predicted hit in the other layer. In both cases he got a resolution of about 200 microns which is encouraging.

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