S800 Documentation

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nmr_probes

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nmr_probes [2013/12/14 16:23]
pereira [Description] 		nmr_probes [2013/12/14 16:27]
pereira [Operation]
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 ===== 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 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. 
  
 In order to reduce the searching time, the program tries to guess the field from the following sources, in priority order:  In order to reduce the searching time, the program tries to guess the field from the following sources, in priority order: 
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   * Calibration if no previous measurement is available    * Calibration if no previous measurement is available 
    
-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.  
- 
 Once a signal is found, the measuring sequence tries to find two resonance positions on either side of 0. Each resonance is calculated as the average between the negative and positive modulation minima (blue and green curves, and corresponding arrows). The final field is interpolated from those measurements, simulating a lock on the NMR signal.  Once a signal is found, the measuring sequence tries to find two resonance positions on either side of 0. Each resonance is calculated as the average between the negative and positive modulation minima (blue and green curves, and corresponding arrows). The final field is interpolated from those measurements, simulating a lock on the NMR signal. 
  
  
-If a dipole is turned off or its field is being changed, the status shows either “Off” or “Unstable” and the program issues a beep. If this happens under running condition in data-taking mode, stop the beam and ask the operator to assist you in investigating the situation of the magnet giving the problem. The operators have the possibility to check on all magnet power supplies and helium fill levels in the control room. A magnet current below the set value, for example, is indicated in Barney as a blue circle on the respective optics element. The S800 Barney page with all magnets operational looks like that:+If a dipole is turned off or its field is being changed, the status shows either "Off" or "Unstable" and the program issues a beep. If this happens under running condition in data-taking mode, stop the beam and ask the operator to assist you in investigating the situation of the magnet giving the problem. The operators have the possibility to check on all magnet power supplies and helium fill levels in the control room. A magnet current below the set value, for example, is indicated in Barney as a blue circle on the respective optics element. The S800 Barney page with all magnets operational looks like that:
  
 {{:wiki:barney_magnets.jpg?700|Barney display for the S800.}} {{:wiki:barney_magnets.jpg?700|Barney display for the S800.}}
  
  
-The magnet currents, measured fields, and deviation from the set value are logged in a file that is soft-linked from the "current run " directory. An example of the log file (analysis.log) for the four dipoles of the analysis line is shown below. +The magnet currents, measured fields, and deviation from the set value are logged in a file that is soft-linked from the "current run" directory. An example of the log file (analysis.log) for the four dipoles of the analysis line is shown below. 
  
  
nmr_probes.txt · Last modified: 2024/06/01 16:35 by swartzj

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