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nmr_probes [2019/10/21 15:41]
pereira [Troubleshooting] 		nmr_probes [2024/01/29 10:51] (current)
swartzj [Error message: "/srv/s3/nmr-logs/spectrograph.log is not accessible"]
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 ====== NMR Control ===== ====== NMR Control =====
-Two digital oscilloscopes are dedicated to NMR readout – one for the analysis line NMRs and one for the spectrograph NMRs. The scopes are located in data-U6, in upper two shelves on the right electronics rack. They are isolated from clean ground because this signals from the NMR probes are on a dirty ground.+Two digital oscilloscopes are dedicated to NMR readout – one for the analysis line NMRs and one for the spectrograph NMRs. The scopes are located in the S3 mezzanine. They are isolated from clean ground because this signals from the NMR probes are on a dirty ground.
  
 ===== Motivation ===== ===== Motivation =====
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 ===== Description ===== ===== Description =====
-The NMR running programs for both the S800 analysis line and spectrograph dipoles can be started from the desktop of computer [[Software#u6pc5 (data U6)|u6pc5]], by clicking in the icons **NMR Analysis** for the analysis line dipoles, and **NMR Spectrograph** for the spectrograph magnets. Alternatively, the NMR control programs can be run from a Linux session by typing ''/usr/bin/wish analysis.tcl'' in directory **/user/s800/Documents/Run/analysis**, for the analysis line, and ''/usr/bin.wish spectrograph_sjw.tcl'' in directory **/user/s800/Documents/Run/spectrograph**, for the spectrograph.+The NMR running programs for both the S800 analysis line and spectrograph dipoles can be started by logging in to exp-s3-nmr.ftc (10.40.230.111) accessible from the EXP network, namely, from any computer connected to the EXP network,
  
-Sometimes the initialization of these applications fail. In that case check section [[nmr probes#troubleshooting|"Troubleshooting"]] below). The picture below shows the NMR panel for the S800 Analysis Line GUI as an example. The top (yellow) panel shows the data relevant to the NMR module, the middle (pink) the digitized signal from the oscilloscope and the bottom (blue) the status and measurements for the dipoles. +  $ ssh [your-user-name-on-EXP]@exp-s3-nmr -Y 
 + 
 +and typing, for the analysis line dipoles  
 + 
 +  $ /usr/bin/wish8.6 /srv/s3-nmr/analysis/analysis.tcl 
 + 
 +and for the spectrograph dipoles 
 + 
 +  $ /usr/bin/wish8.6 /srv/s3-nmr/spectrograph/spectrograph.tcl 
 + 
 +**Note that it is not simply wish anymore but wish8.6.** 
 +Now press start on the GUI, which is shown below, and you should see a field reading. Sometimes the initialization of these applications fail. In that case check section [[nmr probes#troubleshooting|"Troubleshooting"]] below). The picture below shows the NMR panel for the S800 Analysis Line GUI as an example. The top (yellow) panel shows the data relevant to the NMR module, the middle (pink) the digitized signal from the oscilloscope and the bottom (blue) the status and measurements for the dipoles. 
  
 {{:wiki:NMR-control.jpg?350|NMR Control panel for the Analysis line dipoles.}} {{:wiki:NMR-control.jpg?350|NMR Control panel for the Analysis line dipoles.}}
  
 +===== Terminating processes run by another user =====
 +
 +A solution has been implemented for the case where one user needs to run the NMR software via the 'wish8.6' command, but another user is already running it.
 +
 +If a user is running 'wish8.6' (usually 2 processes, one for analysis and one for spectrograph) and another user needs to run it instead, they can do the following:
 +
 +  * Log on to exp-s3-nmr virtual machine (as described above)
 +  * Type 'ps aux | grep wish8.6' to find out the name of the user that is running wish8.6
 +  * Let's suppose user 'alice' is running wish8.6 and user 'bob' needed to run it instead. That being the case, user 'bob' should type the command: 'sudo -u alice pkill wish8.6'
 +  * This will stop both wish8.6 processes that are running as user 'alice' (the important thing to remember is that the username that goes after the -u is the name of the user whose wish8.6 processes you want to stop)
 +  * Now user 'bob' can successfully start wish8.6 processes
 +
 +In short,
  
 +  $ ps aux | grep wish8.6
 +  $ sudo -u usernameRunningWish8.6 pkill wish8.6
 +  
 +and you should be able to run the NMR software.
 ===== Operation ===== ===== Operation =====
 The NMR program constantly checks the status of the various dipoles from the EPICS system and updates the status column. In addition, the program checks the log file at startup for the closest previously measured value. In case no previous measurement can be used the program searches for a signal around the guessed value of the field. This search can take some time if the calibration is off or the hysteresis of the dipole is large. The maximum number of attempts is limited to 200. After that the status is marked as "Failed" and the program gives up on this dipole.  The NMR program constantly checks the status of the various dipoles from the EPICS system and updates the status column. In addition, the program checks the log file at startup for the closest previously measured value. In case no previous measurement can be used the program searches for a signal around the guessed value of the field. This search can take some time if the calibration is off or the hysteresis of the dipole is large. The maximum number of attempts is limited to 200. After that the status is marked as "Failed" and the program gives up on this dipole. 
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   * The terminal server is behind the NMR controllers   * The terminal server is behind the NMR controllers
   * Simply turn it off, wait few seconds, and turn it back on   * Simply turn it off, wait few seconds, and turn it back on
 +
 +==== Error message: "/srv/s3/nmr-logs/spectrograph.log is not accessible" ====
 +
 +  * In a new terminal, ssh to yourname@exp-s3-nmr, then go to /srv/s3/nmr-logs/ and issue: 
 +  * mv spectrograph.log spectrograph-yourname.log 
 +  * Now close the error message window and you should not have this problem anymore. 
 +
 +==== NMR reading sometimes takes too long (> 30 min) ====
 +
 +This is typically caused by one of two possible factors: 
 +
 +1. The signal is weak, and so the NMR "latches" on noise peaks. This is typically the case when the thresholds in the NMR GUI are not set properly. If they are too low, the program may lock in noise. Conversely, if the thresholds are too high, it may miss a weak resonance.
 +  * This can be alleviated by changing the NMR thresholds (it can be done for each magnet in the analysis line, or for both magnets in the spectrograph).
 +  * Stop NMR; enter new threshold (in Volts) and click “Set”; start NMR.
 +  * In general, a threshold 0.15 mV is good for normal NMR signals, whereas 0.10 mV may be necessary if the signals are too weak.
 +
 +2. Initial field where NMR starts scanning is far away from actual value (this has only been seen with Spectrograph)
 +  * Check what field is NMR scanning and compare with field read by neighboring NMR.
 +  * If it is too far, stop NMR; enter field (in T) and click “Set”; start NMR.
 +
 +
 +
  
 ==== Manually setting Dipole Fields  ==== ==== Manually setting Dipole Fields  ====
nmr_probes.1571686869.txt.gz · Last modified: 2019/10/21 15:41 by pereira

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