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| If SLOWDC isn't changing, try changing RC transmission level to 6 for ~10 seconds, then slide back. Sometimes the slow loop code gets bogged down, so moving the transmission level above the ref. cavity transmission level will break the code out of its frozen state since it will think that the mode cleaner isn't locked. |
The FSS has a [[/SLOW PID servo]] which offloads the FAST (PZT) path by feeding back to the NPRO's SLOW input. The FAST has a rough calibration of 5 MHz/V while the SLOW is more like 5000 MHz/V. It has a ~0.1 Hz pole and so that's why its called ''SLOW''. |
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---- == References == * [http://www.ligo.caltech.edu/docs/P/P960008-10.pdf P960008-10]: Improved Multistage Wide Band Laser Frequency Stabilization, by Seiji Kawamura, Alex Abramovici, Mike Zucker (1996). |
The FSS stabilizes the fluctuations in the laser frequency by comparing it to a quiet Reference Cavity. The light is picked off just before it goes into the Pre Mode Cleaner, sent through a EOM and the frequency shifting AOM and then into the RC.
The FSS actuates on the NPRO Piezo (called the FAST path) and on a phase correcting Pockels cell (which is faster than the FAST path).
To lock:
Run the FSSAutolock script from the C1PSL_FSS screen (under the yellow ! button).
The FSS has a /SLOW PID servo which offloads the FAST (PZT) path by feeding back to the NPRO's SLOW input. The FAST has a rough calibration of 5 MHz/V while the SLOW is more like 5000 MHz/V. It has a ~0.1 Hz pole and so that's why its called SLOW.
See also PSL.
attachment:C1PSL_FSS.png
References
[http://www.ligo.caltech.edu/docs/P/P960008-10.pdf P960008-10]: Improved Multistage Wide Band Laser Frequency Stabilization, by Seiji Kawamura, Alex Abramovici, Mike Zucker (1996).