Plotted is the location of the arm higher order modes around 10kHz. They have moved so that the central frequency is the same as the spikes around 10.4kHz, this excites the PI's more.

• In the first plot we see that since November and the start of December, the center of the lower HOM peak has drifted down in frequency to be underneath the 10.kHz PI modes: compare black (now) to red and brown.
  • I tried to check more times to see exactly when this change happened in the 4th attached plot but this is tricky as the location and shape of the HOM depends on how warm the IFO is (i.e. was it DOWN a logn time before locking as in ref 7: Cold IFO). It sees like the change started 6th/7th Dec and was done by 10th Dec.
• In the second plot we see what happened in September when we increased the ETMY Ring Heater (as we repeated today 81891), both HOM peaks moved up in frequency, which is the direction we want.

Maybe an unrelated point is that since the start of October, the circulating arm power has drifted down ~4kW (~1%) from 389 to 285kW when thermalized, plot attached. It's hard to know what's caused this, the IM4 TRANS drifted ~2% but was misaligned so would see alignment shifts 81735, the POP also drifted ~1% before it was recentered 81329. Input power measured by IMC_PWR_IN remained constant.

You cannot just use L1's lockloss code for the tagging universally [should work for the 10kHz PI though].

Because of the way LHO changed their readouts for the OMC, digging into the simulink model will reveal the PI is reading in only the first 32kHz band, for the RMS calculations

You simply have no aliasing down of the full band to utilise it in the way we do; and it will never see 80kHz PI.
Also your scaling is using calibrated DARM units by the look of things; while we use a counts scale; so the numbers in the RMS readouts are different many orders of magnitude.

Very quick shot of the 10.4k homs 2 hours into the first lock with the EY ring heater bumped up to 1.2W from 1.1W. This will need to be checked again later, but it's promising so far.

Here's a reference from 2018 of what trigger levels were as a percentage of the locked build ups for DRMI at a time when it was locking well.  44348

I added a comment here, 81885, pointing to Tony's alog.  The main point is that we probably may also need to update the check that tells the guardian to run a PRMI alignment for the higher flashes.

Gabriele, Camilla.

We are not sure if this measurement makes sense. 

Attached is the same spectrum with the CO2X laser turned off to see the dark noise. It appears that measurement is limited to dark noise of the diode above 40Hz. The ITMX_CO2_ISS_IN_AC channel dark noise is actually above the level when the laser is on, this doesn't make sense to me. 

• Is there anything strange happening in models or chassis? No.
  • The filters in the DC _OUT channels include a CountstoVolts gain(0.000610352) and UndoGain gain(0.00196078) which is 1/510 from the PD electronics D1201111 as expected
  • The AC _OUT channel includes a CountstoVolts gain(0.000610352) and de-whiten zpk([20], [0.01], 0.011322, "n").
  • There is nothing else in the h1hsccs model.
  • Looking at the TCS block diagram E1100892, the ISS PD outputs go though the TCS ISS and Interface Chassis D1300649 (D1300015 shows there nothing happening to the signals inside this chassis), before going to the ADC. So the model should see the signals as if they were coming straight from the PD DB9 output + counts to volts gain. 
• Does DC value of 7e-3 V make sense? Yes.
  • In CIT#389 saw saw -1V (DCMON so gain of 255) for 60mW of laser power (can jump ~by a factor of 2 dependent on wavelength/polarization/how the laser is feeling). From this, expect 1mV from diode (before electronics gain) is 15mW of laser power. So that the DC value measured of 7e-3 V would be around 100mW of power on the PD (within a factor of 2 is 50mW to 200mW). This makes sense as we would expect around 250mW on the ISS PD (50W out of laser x 99/1 BS x 50/50 BS).
• Does Dark noise value make sense: Unsure.
  • In CIT#541, Gabriele shows DC dark noise values of 4e-7 /rHz, this is straight out of the diode (DCMON so x gain of 255) so the comparable value to our _OUT channels would be 1.5e-9 /rHz. This is a factor of 3 different from the 5e-9/rHz dark value we measure at LHO on the DC OUT.
  • Debatable math: The power noise of the diode is 1e-8 W/rHz (from Keita's computations attached to CIT#549). So the RIN should be noise-limited to 1e-8 W/rHz / 0.250W = 4e-8 /rHz. We are measuring down to 5e-9/rHz on the DC channel which is a factor of 10 lower than expected possible

Gabriele and I checked that the H1:TCS-ITM{X,Y}_CO2_ISS_{IN/OUT}_AC filter: de-whiten zpk([20], [0.01], 0.011322, "n"), is as expected from the PD electronics D1201111, undoing the gain of 105dB with the turning point around 20Hz, foton bode plot attached.

This means that both the AC and DC outputs should be the voltage out of the photodetector before the electronics, where the PD shunt resistance was measured to be 66 Ohms.

We have been holding 2W with ASC on before powering up, and using the guardian state PR2_SPOT move, which lets us move the sliders on PR3 and moves PR2, IM4 and PRM sliders to follow PR3. 

Moving PR3 by -1.7 urad (slider counts) increased the power on LSC POP, and POPAIR 18, but slightly misaligned the ALS comm beatnote.  We continued moving PR3 to see how wide the plateau is on LSC POP, we moved it another -3urad without seeing power drop on LSC POP, but the ALS paths started to have trouble staying locked so we stopped there.  (POP18 was still improving, but I went to ISCT1 after the OFI vent and adjusted alignment onto that diode 79883 so it isn't a nice reference). I moved PR3 yaw back to 96 urad on the yaw slider (we started at 100urad), a location where we were near the top for POP and POPAIR 18, so in total we started with PR3 yaw at 100 on the slider and ended with 96 on the slider.   

Please see Tony's comment about DRMI lock acquisition times here:  81879

When we moved PR3, we inceased the level of light on the POPAIR B diode.  That does two things, first it means that the LSC controls were triggered at a lower percentage of the full buildups, which could cause difficulty locking DRMI (we want to maintain the trigger thresholds similar to what was documented in 44348.  ). Also, the alignment check that Tony describes won't work well, because we didn't update the threshold the guardian used to decide that the alignment was poor and we needed to do PRMI. 

From Tony's historgrams I'm not sure which of these is the main impact on DRMI locking times, if it's the triggering or the alignment check.  We updated the trigger levels today, but not the threshold for the alignment check.

In the future we should check all these levels again 44348 when we have a change in power on POPAIR.

I'm no longer quite so sure about the conclusion that Pop18 is higher, or at least enough to really matter.

Here are 2 screenshots that I made extremely quickly, so they are not very awesome, but they can be a placeholder until Tony's much more awesome version arrives.  They both have the same data, displayed 2 ways.

The first plot is pop18 and kappaC versus time.  The x-axis is gpstime, but that's hard to interpret, so I made a note on the screenshot that it ranges from about April 20th (before The Big Shift) to today.  Certainly during times when the optical gain was low, Pop18 was also low.  But, Pop18 is sometimes high even before the drop in optical gain.  So, probably it's unrelated to The Big Shift.  That means that the big shift in the output arm is not responsible for the change in PRCL gain (which makes sense, since they should be largely separate).

The second plot is just one value versus the other, to see that there does seem to be a bit of a trend that if kappaC is low, then definitely Pop18 is low.  But the opposite is not true - if pop18 is low kappaC isn't necessarily low.

The last attachment is the jupyter notebook (you'd have to download it and fix up the suffix to remove .txt and make it again a .ipynb), with my hand-typed data and the plots.

I actually didn't load the guardian at the time of this change, so it didn't take effect until today.

So, we'd like histograms of DRMI acquitisiton times from before April 23rd, from April 23rd until today, and for a few weeks from today.

Using the Summary pages I was able to get a quick google sheet to give me before and after Histograms of how long ISC_LOCK was in DRMI 1F.

https://docs.google.com/spreadsheets/d/1xVmvYJdEq8GfKVcSzPj1fyeS95cIWrAkFjI23AxtsAQ/edit?gid=286373047#gid=286373047

First Sheet's data is before Nov 18th 2024, consisting of 100 gpstimes and durations where ISC_LOCK was in AQUIRE_DRMI_1F.
Second Sheet's data is After Nov 18th 2024. Consisting of 100 gpstimes and durations where ISC_LOCK was in AQUIRE_DRMI_1F

Interesting notes about ISC_LOCK.
ISC_Lock will request PRMI or Check MITCH Fringes some where between 180 seconds and 600 seconds, depending on how much light is seen on AS_AIR.
If AS_AIR sees flashes above 80 then ISC_LOCK will not kick us out of DRMI until 600 seconds.

So it looks like one of the changes that happened on or around Nov18th made the Flashes on AS_Air higher but we are still not actually locking DRMI.
We had fewer Aquire DRMI durations, over 180 Seconds before Nov 18th's changes.

Today's readback voltage is at +3.55V.

Today's readback voltage is at +3.116V.

Today's readback voltage is at +1.857V.

Today's readback voltage is at +0.951V.

Today's readback voltage is at -2.511V