Sheila, Evan

We have been changing the PSL power up and down during CARM offset reduction. Among other things, this changes the optical gain of the IMC PDH loop. So far, we've been compensating for this gain using the IMC servo board as follows:

• For 10 W of PSL power, the input gain on the IMC servo board is 0 dB.
• For 4 W of PSL power, we change the input gain to +6 dB.

Just to make sure that the IMC loop is still OK in the latter configuration, we took an OLTF by driving a 20 mV swept sine into EXC A and monitoring the test points before and after. The result is attached.