sheila.dwyer@LIGO.ORG - posted 18:43, Monday 09 March 2015 - last comment - 01:56, Tuesday 10 March 2015(17150)
IMC gain increased, prep for power increase
To prepare for power increase durring full lock, we have made a few changes:
- THE IMC ugf is moved from 30 kHz to 50kHz, this increases the gain margin as shown in the attached plots.
- THE IMC guardian now calculates the gain that it should use to keep the ugf the same to within 1 dB, in the locked state.
- We changed the minimum power angle for the rotation stage to -25 from -24. This makes the power you get a bit more similar to the power you request.
Images attached to this report
Comments related to this report
We have changed the INCREASE_POWER state in the ISC_LOCK guardian, it now turns the power up to 10 Watts and adjusts both the power normalization and the gain in the summing junction to keep the CARM ugf around 9 kHz.
This worked several times with the rotation stage going pretty fast ("velocity" set to 100) but we have now slowed the velocity down to 10 so that things are not as exciting.
Once people had tuned up the alingment to improve the recycling gain, it no longer works to increase the power with the high recycling gain.