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Entry  Thu May 30 13:15:55 2013, Evan, DailyProgress, Computers, Temporary south refcav autolocker 
    Reply  Fri May 31 13:21:37 2013, tara, DailyProgress, Computers, Temporary south refcav autolocker 
       Reply  Fri May 31 14:23:49 2013, Evan, DailyProgress, Computers, Temporary south refcav autolocker 
    Reply  Mon Jun 3 11:42:03 2013, Evan, DailyProgress, Computers, Temporary south refcav autolocker 
Message ID: 1186     Entry time: Thu May 30 13:15:55 2013     Reply to this: 1187   1189
Author: Evan 
Type: DailyProgress 
Category: Computers 
Subject: Temporary south refcav autolocker 

Again inspired by Zach's bash autolocker, I've written a python autolocker for the south reference cavity. If the cavity loses lock, it turns off the PID loop so that the temperature does not run away to the rails. It then checks that the PMC transmission is high and proceeds to slowly ramp the laser temperature between 7.43 V and 7.50 V.

Note: the aforementioned voltage values only work because the refcav is not heated, and hence the resonance always occurs in roughly the same place (between 7.45 V and 7.48 V, depending on the day). This simple search algorithm is therefore not, not a permanent solution for autolocking the refcav once the heaters are working. For posterity, here are the other values currently hard-coded into the autolocker:

  • darkThreshold: 1 V; this is the value below which the RFPD REFL DC value is taken to indicate that no light is incident on the cavity, and hence the autolocker should turn off the PID loop and then do nothing
  • cavityReflThreshold: 4 V; this is the value above which the RFPD REFL DC value is taken to indicate that light is incident on the cavity, but the cavity is unlocked, and hence the autolocker should try locking
  • pmcThreshold: 150 ADC units; this is the value above which the PMC is considered locked, and hence the refcav autolocker may proceed with its lock procedure. (Note: this is different than the threshold values used in the PMC autolocker.)

The autolocker can be invoked via python srefcavauto.py on controls@fb2.

Since autolocker is coded to do nothing unless the PMC transmission is high, it is best run in conjunction with the PMC autolocker (invoked via python pmcauto.py). It doesn't matter which autolocker you start first.

 

Special bonus settings: the common gain on the TTFSS is 404 clicks, the fast gain is 426 clicks, and the offset is 967 clicks. Tara pointed out that the frequency loop would catch lock easier if the gain settings were around these low values rather that what they were previously (~600).

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