Attached is a noise budget for the DARM spectrum from 2015-06-07 00:00:00Z–02:00:00Z. Notes:

• This spectrum was for 24 W, with SRC WFS retuned and the EX ESD off (LHO#18923 et seq.).
• The quantum noise level is retuned using the null stream (LHO#19077).
• Since the last noise budget, MICH FF was retuned (LHO#18878). SRCL FF is still off.
• MICH, SRCL, and frequency noise coupling TFs were retaken on 2015-06-14 in a similar configuration. Since the interferometer calibration was off, I measured the couplings into OMC sum and then undid the DARM loop and optical gain in order to get a freerunning DARM estimate.
• The intensity noise coupling TF was not retaken. However, from Gabriele's bruco projections around the same time (LHO#18935), it seems like the intensity coupling in the bucket is roughly consistent with what is shown here.
• At high frequencies, I think the frequency noise coupling TF taken on the 14th is somehow underestimating the true coupling on the 7th. The coherence from that time (LHO#18924) seems to support the idea that almost all of the DARM noise above 6 kHz is frequency noise. Either the coupling changed, or perhaps I have not undone the high-frequency response of the OMC sum channel correctly.
• From 10 to 15 Hz, I think the MICH and SRCL projections are suffering from some noise in the coupling TF measurements. From Sheila's entry yesterday (LHO#19139) we can already see that most of the DARM noise here is A2L coupling.

Conclusions:

• In the bucket, we are limited by intensity noise from 120 to 400 Hz. From 60 to 120 Hz, there is still some other broadband noise that is limiting us.
• We are limited by SRCL noise around 50 Hz, but we knew that already and we are already trying feedforward (LHO#19139).
• Above a few kilohertz (and maybe already above 2 kHz), we have a nontrivial amount of frequency noise.