This shows you the differences between two versions of the page.
Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
nmr_probes [2013/12/14 16:23] pereira [Description] |
nmr_probes [2014/11/13 12:15] pereira [Description] |
||
---|---|---|---|
Line 5: | Line 5: | ||
Due to the location of the NMR probes in the dipoles of both the S800 analysis line and spectrograph, | Due to the location of the NMR probes in the dipoles of both the S800 analysis line and spectrograph, | ||
- | The solution | + | 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. |
===== 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 by selecting the NMR option in the operation applications of the desktop **u6pc5**. 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. |
Line 16: | Line 16: | ||
===== 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 " |
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: | ||
Line 26: | Line 26: | ||
* 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, | 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, | ||
- | If a dipole is turned off or its field is being changed, the status shows either | + | If a dipole is turned off or its field is being changed, the status shows either |
+ | |||
+ | |||
+ | THIS FIGURE IS OBSOLETE. NEW A NEWER VERSION | ||
{{: | {{: | ||
- | The magnet currents, measured fields, and deviation from the set value are logged in a file that is soft-linked from the " | + | The magnet currents, measured fields, and deviation from the set value are logged in a file that is soft-linked from the " |
Line 47: | Line 48: | ||
===== Matching ===== | ===== Matching ===== | ||
- | {{: | + | The button labeled “Match” opens a new window for matching |
- | + | {{: | |
- | The button labeled “Match” opens a new window for matching | + | |
===== Troubleshooting ===== | ===== Troubleshooting ===== | ||
- | * The NMR program is connected to the following devices and systems: | + | The NMR program is connected to the following devices and systems: |
* The NMR module through a terminal server | * The NMR module through a terminal server | ||
Line 62: | Line 62: | ||
* The EPICS system through the caRepeater process launched by the et_wish shell running the program | * The EPICS system through the caRepeater process launched by the et_wish shell running the program | ||
- | Any of these connections can eventually be broken, and the program tries to catch the failures and report them to the user. However there are cases when the program | + | Any of these connections can eventually be broken, and the program tries to catch the failures and report them to the user. However there are cases when the program |
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 ): | ||
- | - **telnet 35.8.35.139** | + | - **telnet 35.9.56.212** |
- | - enter any **username** | + | - Enter any **username** |
- | - **su ** | + | - **set priv ** |
- | - **system** | + | - The 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. | ||