Input power was increased from 12W to 15W on Jan 23. A question is if it had an impact on the mystery 1/sqrt(f) noise, in particular if it made it higher.

Figure 1 compares the sensitivity a few days after the power increase (yellow) and before (red). There is no difference in the 80Hz-130Hz frequency band. At high frequency sensitivity is clearly better by ~10%, which is roughly the improvement that is expected from the input power increase as sqrt(15/12) = 1.12. Also many of the lines (157Hz, 196Hz, 310Hz) got reduced, but that could be just a coincidence. Compared to the situation from the Christmas engineering run (blue), the noise is clearly worse, by ~8%.

Figure 2 shows the spectrum for all the days since the middle of the Christmas run, with 1h of data each time, using a media-mean average spectrum to avoid the spectrum being spoiled by 25min glitches. The sensitivity clearly got worse in a systematic way, but it is hard to say from that figure when it happened.

Figure 3 is the same as figure 2, but with only a few of the times shown. During the run, just after the OMC replacement, and couple of other times after that. There is no clear trend that I can see, and in the last few weeks the level has been moving up and down by a few percent.

/users/mwas/detchar/hCompare_20240116/hHighRes.m