Difference between revisions of "Minutes-4-2-2015"

From GlueXWiki
Jump to: navigation, search
Line 19: Line 19:
 
# Engineering
 
# Engineering
 
# Other
 
# Other
−
 
−
<!--
 
  
 
= Minutes =
 
= Minutes =
Line 32: Line 30:
 
== Gas puzzle ==
 
== Gas puzzle ==
  
−
- The new pump has been installed  
+
- The new pump has been installed in the EEL and data taken with the spare package using the certified gas mixture. On the attached plot: CO2 measurements (blue), atmospheric pressure (black), corrected measurements (red) using (dp/p)^2.4 pressure correction. This pump has variable flow, Nick and Chris made voltage control for that. Thus the flow was adjusted in this way, keeping the rotameter open completely, so that the pump doesn't create vacuum.
 +
 
 +
- The plan is to monitor the certified gas till Friday afternoon, then move the sensor to the Hall and monitor the CDC for one more day. On Saturday afternoon Beni will change the CO2 gas factor to 1.
  
 
== CDC update ==
 
== 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.
+
- Naomi found in run 2451, some of the pedestals are wobbling by 100+/-3 units on a scale of hours. Could be temperature variations, in any case it is small compared to the thresholds of ~60.
  
 
== FDC update ==
 
== 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.
+
- The HV channel on FDC4 cell 6 sector 2p, developed a constant current of ~3 microamps (at the nominal 2200V) after being unstable for a week (current/voltage plots attached). Most likely the problem is outside of the gas volume and we may attempt to fix it sometimes when the FDC is pulled outside of the magnet.  
−
 
+
−
- 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 ==
 
== 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 ==
 
== 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.
 
−
 
−
-->
 

Revision as of 14:43, 3 April 2015

April 2, 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. Running at half energy
  2. Gas puzzle
    • CO2 monitoring [2]
  3. CDC update (Beni, Mike)
  4. FDC update (Lubomir)
  5. Electronics (Fernando, Cody, Chris, Nick)
  6. Engineering
  7. Other

Minutes

Participants: Curtis, Naomi(CMU), Sean(NU), Eugene, Luke, Mike, Dave, Chris, Nick, Cody, Beni, Simon, and Lubomir (JLab).

Running at half energy

- For the FDC we expect to have about the same e.m. background on the chambers, i.e. we will be limited by the same photon intensity as in the fall run. The number of pion tracks is expected to be about half of that in the fall. We asked for 16 hours beam time assuming we will have 8 hours at each of the two HV settings: 2200V and 2250V. As the HV filter boxes are expected to reduce the noise significantly, we ask for 16h run but only at one setting, 2200V but at a lower discriminator threshold, thus compensating for the smaller number of tracks.

Gas puzzle

- The new pump has been installed in the EEL and data taken with the spare package using the certified gas mixture. On the attached plot: CO2 measurements (blue), atmospheric pressure (black), corrected measurements (red) using (dp/p)^2.4 pressure correction. This pump has variable flow, Nick and Chris made voltage control for that. Thus the flow was adjusted in this way, keeping the rotameter open completely, so that the pump doesn't create vacuum.

- The plan is to monitor the certified gas till Friday afternoon, then move the sensor to the Hall and monitor the CDC for one more day. On Saturday afternoon Beni will change the CO2 gas factor to 1.

CDC update

- Naomi found in run 2451, some of the pedestals are wobbling by 100+/-3 units on a scale of hours. Could be temperature variations, in any case it is small compared to the thresholds of ~60.

FDC update

- The HV channel on FDC4 cell 6 sector 2p, developed a constant current of ~3 microamps (at the nominal 2200V) after being unstable for a week (current/voltage plots attached). Most likely the problem is outside of the gas volume and we may attempt to fix it sometimes when the FDC is pulled outside of the magnet.

-

Electronics

-

Engineering

Retrieved from "https://halldweb.jlab.org/wiki/index.php?title=Minutes-4-2-2015&oldid=65937"