I ran the noise budget injections for frequency noise, input jitter (both pitch and yaw) and PRCL. All injections were run with CARM on one sensor (REFL B). The cable for the frequency injection is still plugged in as of this alog, but I reset the gains and switches so we are back on two CARM sensors and the injection switch is set to OFF.
All injections are saved in the usual /ligo/gitcommon/NoiseBudget/aligoNB/aligoNB/H1/couplings folder under Frequency_excitation.xml, IMC_PZT_[P/Y]_inj.xml, and PRCL_excitation.xml.
I realized an intensity noise injection might be interesting, but when I went to run the template for the ISS excitation, I was unable to see an excitation. I think there's a cable that must be plugged in to do this? I am not sure.
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Ryan S. sent me a message with this alog that has notes about how intensity noise injections should be taken. Through this conversation, I realized that I had misread the instructions in the template. I toggled an excitation switch on the ISS second loop screen, when I should have instead set the excitation gain to 1.
I was allowed another chance to run the intensity injections, and I was able to do so, using the low, middle, and high frequency injection templates in the couplings folder.
Also, the Input jitter injections have in the past been limited to 900 Hz, because the IMC WFS channels are DQed at 2048 Hz. However, the live IMC channels are at 16 kHz, so I edited the IMC injection templates to run up to 7 kHz, and use the live channels instead of the DQ channels. That allowed the measurements to run above 900 Hz. However, the current injections are band-limited to only 1 or 2 kHz. I think we can widen the injection band to measure jitter up to 7 kHz. I was unable to make those changes because we had to go back to observing, so this is future to-do item. I also updated the noise budget code to read in the live traces instead of the DQ traces.
Unfortunately, in my rush to run these injections, I forgot to transition over to one CARM sensor, so both the intensity and jitter measurements that are saved are with CARM on REFL A and B.
I ran an updated noise budget using these new measurements, plus whatever previous measurements were taken by Camilla in this alog. Reminder: the whole noise budget is now being run using median averaging.
I used a sqz time from last night where the range was around 165 Mpc, starting at GPS 1412603869. Camilla and Sheila took a no-sqz data set today starting at 1412607778. Both data sets are 600 seconds long. I created a new entry in gps_reference_times.yml called "LHO_O4b_Oct" with these times.
To run the budget:
>conda activate aligoNB
>python /ligo/gitcommon/NoiseBudget/aligoNB/production_code/H1/lho_darm_noisebudget.py
all plots found in /ligo/gitcommon/NoiseBudget/aligoNB/out/H1/lho_darm_noisebudget/
I made one significant edit to the code, which is that I decided to separate the laser and input jitter traces on the main DARM noise budget. That means that the laser trace is now only a sum of frequency noise and intensity noise. Input beam jitter is now a trace that combines the pitch and yaw measurements from the IMC WFS. Now, due to my changes in the jitter injections detailed above, these jitter injections extend above 900 Hz. To reiterate: the injections are still only band-limited around 2 kHz, which means that there could be unmeasured jitter noise above 2 kHz that was not captured by this measurement.
One reason I wanted to separate these traces is partly because it appears there has been a significant change in the frequency noise. Compared to the last frequency noise measurement, the frequency noise above 1 kHz has dropped by a factor of 10. The last time a frequency noise injection was taken was on July 11, right before the OFI vent, alog 79037. After the OFI vent, Camilla noticed that the noise floor around 10 kHz appeared to have reduced, as well as the HOM peak heights, alog 76794. She posted a follow-up comment on that log today noting that the IFO to OMC mode matching could have an effect on those peaks. This could possibly be related to the decrease in frequency noise. Meanwhile, the frequency noise below 100 Hz seems to be about the same as the July measurement. One significant feature in the high frequency portion of the spectrum is a large peak just above 5 kHz. I have a vague memory that this is approximately where a first order mode peak should be, but I am not sure.
There is no significant change in the intensity noise from July, except that there is also a large peak in the intensity noise just above 5 kHz. Gabriele and I talked about this briefly; we think this might be gain peaking in the ISS, but its hard to tell from alog measurements if that's possible. We think that peak is unlikely to be from the CARM loop. We mentioned the ISS theory to Ryan S. on the off-chance it is related to the current PSL struggles.
The other significant change in the noise budget is the change in the LSC noise. The LSC noise has reduced relative to the last noise budget measurement, alog 80215, which was expected from the PRCL feedforward implementation. Looking directly at the LSC subbudget, PRCL has been reduced by a factor of 10, just as predicted from the FF performance. Now, the overall LSC noise contribution is dominated by noise from MICH. Between 10-20 Hz, we might be able to win a little more with a better MICH feedforward, however that is a very difficult region to fit because of various high Q features (reminder alog).
Just as in the previous noise budget, there is a large amount of unaccounted-for noise. The noise budget code uses a quantum model that Sheila and Vicky have been working on extensively, but I am not sure of the status, and how much of that noise could be affected by adjustments to the model. Many of the noisy low frequency peaks also appear very broad on the timescale of the noise budget plot. We could try running over a longer period of time to better resolve those peaks.
Between 100-500 Hz there are regions where the sum of known noises is actually larger than the measured noise. I think this is because the input jitter projections are made using CAL DELTA L, but the overall noise budget is run on CALIB CLEAN where we are running a jitter subtraction.
I believe these couplings were pushed to aligoNB repo in commit bcdd729e.
I reran the jitter noise injections, trying to increase the excitation about 2 kHz to better see the high frequency jitter noise. The results were moderately successful; we could probably push even harder. The results indicate that jitter noise is with a factor of 2-3 of DARM above 1 kHz.
I have attached the updated DARM noise budget and input jitter budget. I'm also attaching the ASC budget (no change expected) just because I forgot to attach it in the previous post.