Difference between revisions of "Minutes-3-26-2015"

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= Agenda =
 
= Agenda =
  
−
# Gas issues
+
# Power outage issues
 +
# Gas puzzle
 
#* CO2 monitoring [http://www.jlab.org/Hall-D/detector/fdc/gas_system/DS_PMP_0013_2.pdf CO2 sensor pump]
 
#* CO2 monitoring [http://www.jlab.org/Hall-D/detector/fdc/gas_system/DS_PMP_0013_2.pdf CO2 sensor pump]
 
#* FDC gain measurements [http://www.jlab.org/Hall-D/detector/fdc/gas_system/gain_hv_plot.pdf],  [http://www.jlab.org/Hall-D/detector/fdc/gas_system/old_gas_gain_studies.gif old measurements]
 
#* FDC gain measurements [http://www.jlab.org/Hall-D/detector/fdc/gas_system/gain_hv_plot.pdf],  [http://www.jlab.org/Hall-D/detector/fdc/gas_system/old_gas_gain_studies.gif old measurements]
−
# CDC update (Beni, Mike)
+
# CDC update (Beni, Mike) [[CDC_recent_run_drift_times]]
 
# FDC update (Lubomir)
 
# FDC update (Lubomir)
 
#* Cathode resolution with 55Fe source [http://www.jlab.org/Hall-D/detector/fdc/55Festudies/CathodeRes55Fe.pdf], [http://www.jlab.org/Hall-D/detector/fdc/55Festudies/CathodeRes55Fe_proj.pdf]
 
#* Cathode resolution with 55Fe source [http://www.jlab.org/Hall-D/detector/fdc/55Festudies/CathodeRes55Fe.pdf], [http://www.jlab.org/Hall-D/detector/fdc/55Festudies/CathodeRes55Fe_proj.pdf]
 +
#* [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/HV_4c6_p2.png HV4_c6_2p], [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/HV_4c6_p2_2.png HV4_c6_2p]
 
# Electronics (Fernando, Cody, Chris, Nick)
 
# Electronics (Fernando, Cody, Chris, Nick)
 
# Engineering
 
# Engineering
 
#* Fluorinert leakage [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/IMG_1996.JPG on 03/09],  [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/IMG_2008.JPG on 03/18]
 
#* Fluorinert leakage [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/IMG_1996.JPG on 03/09],  [http://www.jlab.org/Hall-D/detector/fdc/spring2015run/IMG_2008.JPG on 03/18]
 
# Other
 
# Other
−
 
−
<!--
 
  
 
= Minutes =
 
= Minutes =
  
−
Participants: Naomi (CMU), Sean (NU), Fernando, Dave, Chris, Nick, Beni, Sergey, and Lubomir (JLab).
+
Participants: Naomi (CMU), Fernando, Dave, Chris, Nick, Cody, Mike, Beni, Simon, and Lubomir (JLab).
  
−
== Gas issues ==
+
== Power outage issues ==
  
−
- Lubomir presented summary of the FDC gas gain measurements with 55Fe source: first plot shows charge distributions at different HV in the Hall, package 4. Second plot is a summary of all the measurements at 2200/-500V both in the Hall and in the EEL126 with the spare package, as a function of the atmospheric pressure. 1% change of the pressure results in 5-7% change of the gain, as expected from the literature. By some reasons the charge on the upper strips is bigger than on the down ones for both measurements in the EEL and in the Hall; needs further studies. Third plot shows the gain-HV dependence at fixed (+/- 0.2 kPa) atmospheric pressure from the measurements and also from Garfield simulations. Garfield predicts somewhat stronger dependence: Sergey explains it with space charge effects at higher gains when using 55Fe source. Assuming a mixture of 45/55 Ar/CO2 (plus 0.3% alcohol) in the Hall, Garfield predicts higher gains, all this relative to the standard gas mixture 40/60 in the EEL. A simple explanation might be a difference of the gas temperature in the Hall and in the EEL: 6 degC lower temperature in the Hall will explain it, or 1% (absolute) change of the CO2. Conclusion: generally the gain measurements in the EEL and in the Hall are in agreement with  a change of the CO2 from 60% to 55% (+/-1%). Last plot shows previous gain measurements for four gas mixtures using different techniques.  
+
- After restoring the FDC LV, many channels showed "temperature failure". It turned out the fans of the LV crate (U2-2-BOT) were not blowing. After unplugging/plugging the power cord, the fans started operating. Fernando: most likely it is a control issue, also one has to find a way to read the fan speed remotely. The CDC LV crate had no problems.
  
−
- Beni continued  changing different configurations in the gas mixing system trying to identify the source of the disagreement without success so far: the biggest change in the max drift time was 8% but was not repeatable.
+
- After the outage, the chiller was turned on without touching the switch-off box, even the interlock should have prevented the box from turning on. Dave and Hovanes will look into this.
 +
 
 +
- All the elements of the gas system were of UPS and it never stopped for the FDC. Beni turned off the CDC MFCs in the gas room because they were in a continuous mode (temporary), therefore the pressure in the CDC mixing tank went to zero. It would be interesting to measrue the Oxygen contamination in the CDC.
 +
 
 +
== Gas puzzle ==
 +
 
 +
- The new pump for the CO2 sensor will come tomorrow. After calibration the sensor will be installed in the Hall to monitor the adjustment of the CDC gas mixture to 50/50.  
  
 
== CDC update ==
 
== CDC update ==
  
−
- Mike showed a plot with the positions of the noisy channels: most are at ~7 o'clock. The HV filter was installed on the channels at ~9 o'clock and this sector is indeed very clean.
+
- Naomi showed interesting results (linked above) comparing two runs before/after Beni made several modifications of the gas mixing system. They demonstrate change of the drift time in the CDC by ~10%, but most noticeably big change in the gain. By analyzing more runs in between we should figure out what caused the changes.
  
 
== FDC update ==
 
== FDC update ==
  
−
- The chiller is consuming a lot of Fluorinert. After 10 days of operation we had to refill it with ~1.5 galons (see photos attached). Need to sniff the connections and later possibly the chiller inside. As discussed with Eugene and Tim, the plan is to buy another chiller like this and connected it to the FDC right away.  
+
- Lubomir studied the cathode resolution using the runs with 55Fe source, both with the FDC in the Hall and with the spare package. Cathodes can reconstruct the position of the wire (that was used as a trigger) with a surprisingly high precision. First plot shows the residual vs coordinate along the wire, where one see interesting structures with widths of ~100 microns. Even simple projection (second plot) gives a resolution of ~180 microns. These numbers should be divided by ~4 to get the cathode resolution along the wire, so we get 25-50 microns !?! Of course the advantage of the 55Fe source is that it gives a huge signal with a standard shape, which is not the case for the hits from the charged particle. Still this technique can be used to study systematic effects like cathode deformations.  
  
−
- The 8 wire channels with no signals reported on the last meeting were fixed: the connector was not properly connected at the front of the TDC.  
+
- One HV channel (FDC4 cell 6 sector 2p) shows unstable HV, going down from time to time by up to 7-8Volts, and jumping current up to 2-3 uA (two plots attached). By swapping cables, it was found the problem is in the detector. The current can be explained by the detector, but it is not clear why the HV is not stable.
−
 
+
−
- Picture: no corrosion at all on one of the cathodes on the spare package.
+
  
 
== Electronics ==
 
== Electronics ==
  
−
- HV filters will come by the end of the month, so hopefully we will have a good data in April. Nick needs and will take from the Hall the only filter that is now installed on the CDC HV.
+
- Beni answering Cody's question: the flash 125s should stay ON when the DAQ is not running, they don't consume a lot of power.
  
 
== Engineering ==
 
== Engineering ==
  
−
- Dave, Lubomir discussed with Bill possible replacement of the CO2 sensor pump. Bill contacted a company with long lasting pumps however they all work on flows > several liters per minute. We decided to go with a diaphragm pump that has ~1 year life with a variable flow (spec attached): we need 0.1 l/min for FDC and 0.1-0.5 l/min for the CDC. Fernando agreed to install one MPOD in a BCAL crate to vary the voltage of the pump.
+
- Yesterday morning we found a Fluorinert leak/drip at the connection of the return to the chiller. After fixing it one can still sniff leakage at almost all connections to the chiller, but since then the loss of Fluorinert was reduced significantly.
−
 
+
−
-->
+

Latest revision as of 17:06, 2 April 2015

March 26, 2015 FDC+CDC meeting

Connection

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

Agenda

  1. Power outage issues
  2. Gas puzzle
  3. CDC update (Beni, Mike) CDC_recent_run_drift_times
  4. FDC update (Lubomir)
  5. Electronics (Fernando, Cody, Chris, Nick)
  6. Engineering
  7. Other

Minutes

Participants: Naomi (CMU), Fernando, Dave, Chris, Nick, Cody, Mike, Beni, Simon, and Lubomir (JLab).

Power outage issues

- After restoring the FDC LV, many channels showed "temperature failure". It turned out the fans of the LV crate (U2-2-BOT) were not blowing. After unplugging/plugging the power cord, the fans started operating. Fernando: most likely it is a control issue, also one has to find a way to read the fan speed remotely. The CDC LV crate had no problems.

- After the outage, the chiller was turned on without touching the switch-off box, even the interlock should have prevented the box from turning on. Dave and Hovanes will look into this.

- All the elements of the gas system were of UPS and it never stopped for the FDC. Beni turned off the CDC MFCs in the gas room because they were in a continuous mode (temporary), therefore the pressure in the CDC mixing tank went to zero. It would be interesting to measrue the Oxygen contamination in the CDC.

Gas puzzle

- The new pump for the CO2 sensor will come tomorrow. After calibration the sensor will be installed in the Hall to monitor the adjustment of the CDC gas mixture to 50/50.

CDC update

- Naomi showed interesting results (linked above) comparing two runs before/after Beni made several modifications of the gas mixing system. They demonstrate change of the drift time in the CDC by ~10%, but most noticeably big change in the gain. By analyzing more runs in between we should figure out what caused the changes.

FDC update

- Lubomir studied the cathode resolution using the runs with 55Fe source, both with the FDC in the Hall and with the spare package. Cathodes can reconstruct the position of the wire (that was used as a trigger) with a surprisingly high precision. First plot shows the residual vs coordinate along the wire, where one see interesting structures with widths of ~100 microns. Even simple projection (second plot) gives a resolution of ~180 microns. These numbers should be divided by ~4 to get the cathode resolution along the wire, so we get 25-50 microns !?! Of course the advantage of the 55Fe source is that it gives a huge signal with a standard shape, which is not the case for the hits from the charged particle. Still this technique can be used to study systematic effects like cathode deformations.

- One HV channel (FDC4 cell 6 sector 2p) shows unstable HV, going down from time to time by up to 7-8Volts, and jumping current up to 2-3 uA (two plots attached). By swapping cables, it was found the problem is in the detector. The current can be explained by the detector, but it is not clear why the HV is not stable.

Electronics

- Beni answering Cody's question: the flash 125s should stay ON when the DAQ is not running, they don't consume a lot of power.

Engineering

- Yesterday morning we found a Fluorinert leak/drip at the connection of the return to the chiller. After fixing it one can still sniff leakage at almost all connections to the chiller, but since then the loss of Fluorinert was reduced significantly.

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