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Thu Jul 10 14:59:01 2008, rob, Update, Locking, RF common mode at zero offset
Fri Jul 11 23:55:25 2008, alan, Update, Locking, RF common mode at zero offset
Thu Jul 10 14:59:01 2008
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RF common mode at zero offset
rob, john, yoichi
Last night we succeeded in reducing the CARM offset to zero
We handed off control of the common mode servo from PO-DC to POX-I.
We pushed the common mode servo bandwidth to ~19kHz. Without the boosts, it had ~80 degs of phase margin. Didn't measure it after engaging the boosts (Boost + 1 superboost). Trying to engage the second superboost stage broke the lock.
The process is fully scripted, and the script worked all the way through several times.
The DARM ugf was ~200Hz. The RSE peak could clearly be seen. No optical spring, as expected (we're locking in anti-spring mode).
Engaging test mass de-whitening filters did not work (broke the lock).
I'm attaching a lock control sequence diagram and a trend of the arm power during a scripted up-sequence. I think the script can be sped up significantly (especially the long ramp period).
Calibrated DARM spectrum
Noise hunting (start with dewhites)
DC - Readout
Lock to the springy side.