Difference between revisions of "Minutes-10-7-2010"

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- There was a meeting between JLab people and AdvanceTEC that will build the clean room. Completion date: January 7th. AdvanceTEC had two concerns: the power coming to building (from Dominion Power) is close to the expected use and has to be checked. The second is related to the quality of the floor, not good enough for 10K clean room. AdvanceTEC will send a quote to re-seal the floor.  
 
- There was a meeting between JLab people and AdvanceTEC that will build the clean room. Completion date: January 7th. AdvanceTEC had two concerns: the power coming to building (from Dominion Power) is close to the expected use and has to be checked. The second is related to the quality of the floor, not good enough for 10K clean room. AdvanceTEC will send a quote to re-seal the floor.  
  
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- Bill, David and a machinist from our machine shop visited  
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- Bill, David and a machinist from our machine shop visited "Vision machining". The frame production has started. About half of the spacer rings are ready. Two of the wire frames are here at JLab, being laminated in the moment with the Rohacell rings in 126. Five Rohacell rings were made by Casey and David. Tomorrow morning David with techs will be at Blue Crab to turn up two granite tables. The idea is to start using them for the lamination because of the limited space in 126. 
 
    
 
    
 
== Electronics ==
 
== Electronics ==
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- Gerard will use the pulses generated from Garfield to study the timing of the fADC125 and will try different interpolation algorithms. He's working now on the firmware.
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- Chris: all 28x4 boards were shipped to the company for stuffing and will have 2x4 (two of each type) ready within a week.
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- Fernando will finalize the rigid-flex design (Roger is busy the next several weeks) and then submit it to the procurement. In a week (Oct. 14) we must here from the procurement about the cathode foils. 
  
 
- Fernando: the last PCBs were shipped and will have them by Monday and then all will be sent for assembly (the contract is in place already). Chris checked all the boards
 
- Fernando: the last PCBs were shipped and will have them by Monday and then all will be sent for assembly (the contract is in place already). Chris checked all the boards
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on the module so that we can use it for the next tests. Gerard fixed the third fADC125 and soon will have it ready to be sent to CMU. No news concerning the cathode  
 
on the module so that we can use it for the next tests. Gerard fixed the third fADC125 and soon will have it ready to be sent to CMU. No news concerning the cathode  
 
foils.
 
foils.
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- Lubomir updated the document about the FDC electronics requirements, linked above, where you can find more details of the discussions listed below.
 
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- Pre-amps in discriminator mode: GlueX-doc-1364 states: "the discriminator has been optimize for operation
 
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between 2-5fC and has a range of 20fC". While testing the discriminator cards with the full-scale prototype the lowest possible threshold was 10fC. With more chambers connected
 
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and more noise we may need to increase the threshold up to 40-60fC. Fernando: the above numbers correspond to the high gain mode, in case of a low gain these numbers have to be
 
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multiply by ~4.
 
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- Quadratic vs linear interpolation in fADC125: if using fADC125 for drift time measurements, the quadratic interpolation gives a little advantage for 40ns peaking time.
 
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If comparing the timing from the strips and wires (this helps to separate the real from the fake hits) the fADC resolution is of the order of 1ns. In this case the
 
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quadratic interpolation gives ~25% better resolution than the linear.
 
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- fADC vs discriminator for the wires: Eugene asked if we have decided. According to the simulations the discriminator gives much better position resolution for distances
 
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smaller than 3-2mm where good timing resolution is needed. For distances bigger than 4mm fADC gives ~20% better resolution. Gerard: realistically, one has to use also 1ns timing resolution for the discriminator; Lubomir will implement this in the Garfield simulations. Gerard wanted to have the raw and convoluted signals from the Garfield simulations.
 
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Lubomir will send him the program to generate the signals. Nevertheless, the biggest advantage of the discriminator card is that it is
 
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close to the detector and one can lower the threshold, which will improve the resolution. At the same time, one can use the cathode information from the FADC
 
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to reconstruct the drift time in the regions where it gives better precision.
 
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- FDC gas mixture: Eugene asked about the status. As far as the electronics is concerned one should assume 8x10^4 gas gain that we got with 40/60 Ar/CO2 and 2225V/-500V voltage.
 
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Both wire and strip resolutions improve with increasing signal to noise ratio and the signals with 40/60 were sufficiently high to get the design resolution.
 
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The 4-5mm (distance to the wire) region is an exception, where long tails in the drift time distribution significantly deteriorate the resolution.
 
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This is because of the strong drift time vs electric field dependence. The problem can be solved by using 90/10 mixture but then we can't reach the same gas gain
 
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because of the limited quenching properties of CO2.
 
  
 
== Engineering ==
 
== Engineering ==

Revision as of 16:39, 7 October 2010

October 7, 2010 FDC meeting

Tentative Agenda

  1. Production
    • Blue Crab status
    • Frame production
  2. Electronics
    • Update on PCBs, fADC125 and other (Fernando, Chris, Gerard)
  3. Engineering
    • Wire stringing: fixtures, movement system (Bill, David)
    • Update on tension measurements (Lubomir)
    • Wire tension requirements (Lubomir)
    • Other: gas system using methane
  4. Full-scale prototype
  5. Other


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