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nmr_probes [2013/12/14 16:29]
pereira [Troubleshooting] |
nmr_probes [2015/09/21 14:34]
pereira [Troubleshooting] |
| Due to the location of the NMR probes in the dipoles of both the S800 analysis line and spectrograph, the NMR signals are usually too small for the NMR module to lock on. This has been a long standing problem which required the users to manually search the resonance, a painful and lengthy process (especially at 3:00 AM!), as well as costly in beam time. The improvement made in 2001 was a remote control panel for the NMR modules that prevented the users from having to enter the vault in order to measure the fields and match the dipoles. Although it greatly shortened the amount of time and energy spent in performing those tasks, it still remained laborious compared to a fully autonomous system like the NMR program running on the A1900 for which the signals are strong enough for the module to lock on. | Due to the location of the NMR probes in the dipoles of both the S800 analysis line and spectrograph, the NMR signals are usually too small for the NMR module to lock on. This has been a long standing problem which required the users to manually search the resonance, a painful and lengthy process (especially at 3:00 AM!), as well as costly in beam time. The improvement made in 2001 was a remote control panel for the NMR modules that prevented the users from having to enter the vault in order to measure the fields and match the dipoles. Although it greatly shortened the amount of time and energy spent in performing those tasks, it still remained laborious compared to a fully autonomous system like the NMR program running on the A1900 for which the signals are strong enough for the module to lock on. |
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| The solution presented in this bulletin and now implemented on the S800 uses digital oscilloscopes to digitize the NMR signal. The digitized signal is then used in a program that calculates the position of the resonance and deduces the value of the magnetic field. This program (written in Tcl/Tk) is fully autonomous and automatically writes the measured Brho values to the relevant EPICS channels. In addition, it offers the possibility to match the dipoles by pairs and keeps a log file of the measured fields. | The solution implemented on the S800 uses digital oscilloscopes to digitize the NMR signal. The digitized signal is then used in a program that calculates the position of the resonance and deduces the value of the magnetic field. This program (written in Tcl/Tk) is fully autonomous and automatically writes the measured Brho values to the relevant EPICS channels. In addition, it offers the possibility to match the dipoles by pairs and keeps a log file of the measured fields. |
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| ===== Description ===== | ===== Description ===== |
| The NMR running programs for both the S800 analysis line and spectrograph dipoles can be started by selecting the NMR option in the operation applications of the desktop **devop1**. 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. | 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. |
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| | 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. |
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| {{: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.}} |
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| 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. In the figure below, the S800 Barney page with all magnets operational is shown. The grey square in the third dipole of the analysis line indicates that the system is trying to read the current of the magnet. The blue squares in the second dipole of the analysis line and the two dipoles of the spectrograph indicate that the read and desired current values differ by more than 0.1%. |
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| {{:wiki:barney_magnets.jpg?700|Barney display for the S800.}} | {{:wiki:barney_s800_unmatched.jpg?850|Barney display for the S800.}} |
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| In case nothing happens after clicking on the icon, the connection to the NMR module is probably locked and needs to be freed. To free it, type the following from any shell window (actual typing show in this font ): | In case nothing happens after clicking on the icon, the connection to the NMR module is probably locked and needs to be freed. To free it, type the following from any shell window (actual typing show in this font ): |
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| - **telnet 35.8.35.139** | - **telnet 35.9.56.212** |
| - enter any **username** | - Enter any **username** |
| - **su ** | - **set priv ** |
| - **system** | - The system will ask you the password ("system") |
| - **unattach port x** (where x=1 for the analysis line and x=2 for the spectrograph) | - **unattach port x** (where x=1 for the analysis line and x=2 for the spectrograph) |
| - **logout** | - **logout** |
| - Click again on the starting icon and the program should start. | - Click again on the starting icon and the program should start. |
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