Sheila, Evan, Stefan - Reduced the whitening gain on both AS 36 ASC diodes. The new value is 24dB. We increase the input matrix values from 1 to 2 to compensate (for MICH and SRC1, i.e. the SRM loop). - We tried to phase the AS_A_36 quadrants by wiggling SRM in yaw and pitch, maximizing the I signal. Not sure how meaningful that was though, because the actual signal we ended up using was Q. - We switched the the sensor for SRC1_YAW (SRM) to 0.3*AS_A_36_Q + 0.3*AS_B_36I. This signal clearly reacted to our mysterious SRC cavity drifts, and had zero offset at the good locking point. - We increased the power to 23W. This is the maximum power currently available. With this new SRM yaw sensor the 23W was very stable. - The DARM offset was 14pm (or 1e-5 cts). - This gave us a recycling gain of 38. - Measured the open loop gain and verified the calibration. - This configuration was stable for 1h. - We took SRCL noise injections at: 8:46:15UTC and 8:59:40UTC (SRCL cut-off filter off and on) - We took MICH noise injections at: 8:52:15UTC and 8:55:40UTC (SRCL cut-off filter on and off) - Pushed the intent bit at 9:06:30 UTC. - The inspiral range seems quite remarkably flat at 57 Mpc. A stron indication that we are now purley electronics noise limited at low frequencies. To do tomorrow: - Explore DARM offset: the new OMC code is ready to install, and will allow on-the-fly OMC offset tuning. - Add the new ASC INMATRIX to Guardian. - Add the new DARM offset to Guardian. - Generate noise budget.
Attached is a new spectrum, before and after screenshots of the AS A 36 WFS phases, and 3 OLG measurements made at 3 different input powers.
I will take a closer look at the noise budget over the weekend, but it seems (roughly) that above 20 Hz we are currently limited by DAC→ESD noise and quantum noise. As usual, there is some uncertainty in coupling strength of the ESD to DARM, which may explain the discrepancy in the plot from 20 Hz to 100 Hz.
This is fantastic -- perfect timing for the low noise Electro-Static Driver installation next week!