Difference between revisions of "Minutes-8-13-2015"

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= Agenda =
 
= Agenda =
  
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# Detector performance document [https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=2775 GlueX-doc-2775]
 
# CDC update (Mike, Simon, Beni)
 
# CDC update (Mike, Simon, Beni)
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#* [https://logbooks.jlab.org/entry/3347749 wire offsets vs z (logbook entry)]
 
# FDC update (Luke,Lubomir)
 
# FDC update (Luke,Lubomir)
 
#* Tagger Tests with Fe source: [http://www.jlab.org/Hall-D/detector/fdc/luke/2250_XvsRatio.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/2250_XvsRatioPY.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/Tag_RatioTGraph.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/Tag_XpeakTGraph.pdf]
 
#* Tagger Tests with Fe source: [http://www.jlab.org/Hall-D/detector/fdc/luke/2250_XvsRatio.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/2250_XvsRatioPY.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/Tag_RatioTGraph.pdf][http://www.jlab.org/Hall-D/detector/fdc/luke/Tag_XpeakTGraph.pdf]
 
# Electronics (Fernando, Chris, Nick)
 
# Electronics (Fernando, Chris, Nick)
 +
#* [https://logbooks.jlab.org/entry/3347746 separating broken CDC wire]
 
# Engineering
 
# Engineering
 
# Other
 
# Other
 
<!--
 
  
 
= Minutes =
 
= Minutes =
  
Participants: Curtis, Naomi, Mike (CMU), Fernando, Eugene, Luke, Beni, Dave, Chris, Nick, Simon, Sergey and Lubomir (JLab).
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Participants: Curtis, Naomi, Mike (CMU), Luke, Beni, Dave, Chris, Nick, Simon, Sergey and Lubomir (JLab).
 +
 
 +
== Detector performance document ==
 +
 
 +
- Curtis is working on a document describing the so-far achieved detector parameters compared with the design goals. Lubomir will add a page about the FDC.  
  
 
== CDC update ==
 
== CDC update ==
  
- Simon studied the effect of the wire offset on the drift time using Garfield - see the logbook entry above. An offset of 1mm will make a factor of two difference in the drift time from the two extreme distances. In a good approximation the time-to-distance relation is symmetric w.r.t. wire position.
+
- Simon studied the wire offset as function of z (along wire) using beam data. In the logbook entry linked above, the two plots show the offsets for a straw at 9 o'clock when the track is above/below the wire. The offset variations are consistent with up/down deformation, possibly sagging of the tube or wire. To confirm this, need to look also at straws at 12/6 o'clock. Curtis, Naomi: if supported at the ends only, the tubes will sag by few mm, but after gluing them together there was no sagging.  
  
- Discussion about what might be the cause for such offsets: sagging of the wires not likely, possibly deformation of the tubes. Naomi described the gluing process - the straws were strapped during curing then released on the next day. All the tubes were checked for flatness. Everybody agrees, we need more cosmic data to study the z,phi dependence of the deformations. Simon will look also in the beam data.
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- Cosmic data will be taken over the weekend with mode 7.
  
- One CDC wire (on D6 connector) broke. According to Beni we lost HV on that wire at 4:26am on July 28th, that could be the time it broke. Naomi: about 10 wires broke in the first several weeks after their installation and were replaced.
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== Electronics ==
  
- Nick: separated the broken wire from the HV. 10 channels from HV sector 5 tripped recently. 
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- Nick showed pictures (logbook entry linked above) demonstrating the separation of the CDC broken wire.
 
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- Beni and Nick investigated different grounding configurations - see table above. Connecting the standoffs between two cards reduced the noise by about 4%. The hope is that connecting more cards will further reduce the noise. Fernando: need to consider the resolution/efficiency improvement since this is a lot of work.
+
  
 
== FDC update ==
 
== FDC update ==
  
- Lubomir showed results with microscopic, MC type, Garfield simulations of the avalanche. Last two plots show distributions of the avalanche electrons - as function of distance to the wire (on average very close to the wire), and position along the wire (only ~6 micron spread). The asymmetry in the signals on the two cathodes can be predicted by the microscopic simulations at least qualitatively. The results depend on the exact electronics response function and the ion contribution. The asymmetry in the cathode signals comes from  the asymmetry in the weighting field at the two sides of the wire, demonstrated in the other plots above.  
+
- Luke reported about the studies with 55Fe source with the spare package (plots attached). One can reconstruct the avalanche position in 2D: using up/down cathode charge ratio for position in direction perpendicular to the chamber and for the left/right position w.r.t. wire using the crossing of the centroid positions on the two cathodes. After fine calibration of the cathode channels one can see a hole where the wire is. Luke fitted the maximums at the two sides of the wire, first, in up/down direction and then left/right from the wire. The up/down maximum positions vary with the charge as demonstrated for two gas mixtures, 60/40 and 40/60 Ar/CO2. The left/right maximums are almost constants. The only explanation so far is related to the contributions from the ion tails that somehow vary with the charge.
 
+
== Engineering ==
+
 
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- Finally we have about 50/50 gas mixture in both detectors - see the CO2 sensor results attached above. The measurements were done by switching between FDC (lower CO2) and CDC (higher CO2 percentage).
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-->
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Latest revision as of 17:12, 24 February 2017

August 13, 2015 Drift Chamber meeting

Connection

  1. Instructions for Bluejeans meeting connection
  2. Meeting ID: 290664653
  3. To join via a Web Browser, go to the page [1] https://bluejeans.com/290664653.

Agenda

  1. Detector performance document GlueX-doc-2775
  2. CDC update (Mike, Simon, Beni)
  3. FDC update (Luke,Lubomir)
  4. Electronics (Fernando, Chris, Nick)
  5. Engineering
  6. Other

Minutes

Participants: Curtis, Naomi, Mike (CMU), Luke, Beni, Dave, Chris, Nick, Simon, Sergey and Lubomir (JLab).

Detector performance document

- Curtis is working on a document describing the so-far achieved detector parameters compared with the design goals. Lubomir will add a page about the FDC.

CDC update

- Simon studied the wire offset as function of z (along wire) using beam data. In the logbook entry linked above, the two plots show the offsets for a straw at 9 o'clock when the track is above/below the wire. The offset variations are consistent with up/down deformation, possibly sagging of the tube or wire. To confirm this, need to look also at straws at 12/6 o'clock. Curtis, Naomi: if supported at the ends only, the tubes will sag by few mm, but after gluing them together there was no sagging.

- Cosmic data will be taken over the weekend with mode 7.

Electronics

- Nick showed pictures (logbook entry linked above) demonstrating the separation of the CDC broken wire.

FDC update

- Luke reported about the studies with 55Fe source with the spare package (plots attached). One can reconstruct the avalanche position in 2D: using up/down cathode charge ratio for position in direction perpendicular to the chamber and for the left/right position w.r.t. wire using the crossing of the centroid positions on the two cathodes. After fine calibration of the cathode channels one can see a hole where the wire is. Luke fitted the maximums at the two sides of the wire, first, in up/down direction and then left/right from the wire. The up/down maximum positions vary with the charge as demonstrated for two gas mixtures, 60/40 and 40/60 Ar/CO2. The left/right maximums are almost constants. The only explanation so far is related to the contributions from the ion tails that somehow vary with the charge.