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nmr_probes [2019/01/31 12:27]
pereira [Troubleshooting]
nmr_probes [2019/10/21 15:43] (current)
pereira [NMR GUI does not communicate with NMR controllers]
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 ===== Troubleshooting ===== ===== Troubleshooting =====
 +
 +
 +==== NMR GUI does not start ====
  
 The NMR program is connected to the following devices and systems: ​ The NMR program is connected to the following devices and systems: ​
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   - **logout** ​   - **logout** ​
   - Click again on the starting icon and the program should start. ​   - Click again on the starting icon and the program should start. ​
 +
 +
 +==== NMR GUI does not communicate with NMR controllers ====
 +  * This can be seen, for instance, when the NMR controller finds a resonance, but the NMR GUI keeps trying forever.
 +  * Most likely, you need to reboot the terminal server located in S3
 +  * Go to the mezzanine level, where the NMR controllers are located
 +  * The terminal server is behind the NMR controllers
 +  * Simply turn it off, wait few seconds, and turn it back on
 +
 +
 +
 +==== Spectrograph NMR GUI "​locks"​ in noise or does not see weak resonance====
 +  * 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.
 +  * Threshold for the Spectrograph resonance can be adjusted by hand in the Spectrograph NMR GUI. In general, a threshold 0.15 mV is good for normal NMR signals, whereas 0.10 mV may be necessary if the signal are too weak.
 +
 +
 +==== Manually setting Dipole Fields ​ ====
 +(Based on notes from Mathias Steiner with some extra info included)
 +
 +You will need to get access to the NMR controllers in the mezzanine level of S3 (see picture below). You will also have to connect an oscilloscope to one of the NMR controllers,​ either analysis line (left) or Spectrograph (right). Connect the left BNC connector (field modulation) to CH1 in the oscilloscope and the right BNC connector (NMR signal) in CH2. Select XY display, and AC coupling.
 +
 +
 +
 +Let’s assume that you want to set the dipole I265DS (first dipole (D1) of S800 Spectrograph) to the rigidity (Brho) 3.7965 Tm (this works for any dipole in the S800)
 +
 +
 +**Method 1**
 +  * Divide Brho by the dipole radius 2.8028m (you can see the nominal radius of each dipole in Barney) to determine the desired field (in Tesla). In this case, it will be 1.35454 T (or 13.5454 kG)
 +  * Get access to the NMR controller in the mezzanine level of S3 vault (see figure below). Push the “SEARCH LOCAL” button to take control out of REMOTE mode.
 +  * Select the right probe by turning the “probe knob” (see figure below). Remember, each dipole has two probes: probe 4, covers fields in the range 0.34 – 1.05 T, and probe 5 covers fields in the range 0.7–2.1 T. In this case, we should set the knob of the Spectrograph controller to position B 
 +        * The list of probes that can be selected with the knobs are, for the Spectrograph:​ A = dipole D1, probe 4; B= D1 probe #5; C=D2 #4; D=D2 #5. Analysis line: A = D1 #4 probe; B=D1 #5; C=D2 #4; D=D2 #5; E = D3 #4; F=D3 #5; G=D4 #4; H=D4 #5.
 +  * Use the “coarse” and “fine” knobs to select the field that you want (in T): 1.35454 T. By doing this, you are asking the NMR controller to just look at that field. ​
 +  * If the field of that dipole happens to be close enough to the field that the NMR controller is looking at, Bingo! You’ll most likely see a resonance in the oscilloscope. In the most likely situation, however, your magnet is far away from the NMR search window and you will see only a flat line in the oscilloscope.
 +  * All you need to do now is to vary the magnetic field of your dipole, and drive it towards the value that the NMR controller is looking at. For instance, in the s800 computer **u6pc5**, open the QtKM file BLSetup_A1900.gkm (connected to the "knob box") and use channel I265DS. ​
 +  * As you get close to that value, the oscilloscope will show the NMR resonance. Keep moving until the resonance is well centered. At that point, your dipole is set to the desired field
 +
 +**Method 2**
 +  * Alternatively,​ you can force the dipole to its new field through the calibration in the control system. Note, the EPICS channel **I265DS_MAG.BSVL** [B field, set value] shows the magnetic field that corresponds to the set current -- this way you can always know your approximate field for the current read from, e.g. EPICS channel I265DS.
 +  * Set EPICS channel **I265DS_MAG.BSET** to 13.5454 (note, the default value of this channel is always an (impossible) 9999.1111, which is ignored. Typing 13.5454 will cause the magnet to go to 257.577 A, and **I265DS_MAG.BSET** goes back to 9999.1111. Setting the magnet this way will get you to plus or minus half a percent of where you want to be.
 +  * At that point, the quickest way may be to use the FINE knob in the NMR controller to find the actual field value. Just turn the knob until the resonance is centered in the oscilloscope,​ and then read off the field value in the front panel of the controller.
 +  * Once you know the value of the field, type it (in Tesla) into the EPICS channel **I265DS_MAG.FELD**. Note that this is what Daniel'​s NMR GUI program does whenever it finds  the resonance. ​
 +  * Having done that, you can use the BARNEY '​match'​ button to match the magnet.
 +  * Repeat until satisfied.
 +
 +
 +{{:​wiki:​NMRandOscilloscope.png?​550|NMR Spectrograph controller connected to oscilloscope.}}
 +{{:​wiki:​NMRController.png?​550|NMR Spectrograph controller.}}
 +
  
nmr_probes.1548955626.txt.gz · Last modified: 2019/01/31 12:27 by pereira