[Cheryl, Giacomo]

Last Friday (February 1st), just before I left, Cheryl and I repeated the measurements of the IMC cavity pole using the same setup I had prepared the previous week.

We took the measurement twice, using two slight variations:

- measure the transfer function TF1 between the the ISS PD and the PD on the IOT table, in reflection of the unlocked and misaligned IMC. Then measure the transfer funtion TF2 between the ISS PD and the same PD on the IOT table, but moved in the transmitted path of the locked IMC. The ratio TF2/TF1 should give the IMC TF.

- measure the transfer function TF1 between output of the SR785 and the PD on the IOT table, in reflection of the unlocked and misaligned IMC. Then measure the transfer funtion TF2 between the SR785 and the same PD on the IOT table, but moved in the transmitted path of the locked IMC. TF2/TF1 should give the IMC TF.

The good news is that the two measurements are in very good agreement with each other (as expected and hoped); the bad one is that they are not well fitted by the expected TF.

Attachments:

1)  the magnitude and phase of the IMC TF as measured using the two techniques, and compared with the expected value

2) a fit to the magnitude (in dB) of the TF, between 2.5 and 70 kHz (for comparison with LLO measurement that can be found here, and I believe was fit in this range)

It might be worth repeating the measurement with a different PD and maybe with an instrument that can go higer in frequency.

This report is the work that was preformed yesterday at End Y by the Apollo crew: The dome was removed from BSC 10, o-ring protecters installed on the BSC and dome placed on the piers in preperation for cleaning. We removed various pieces and parts from the termination slab (north side) to be used as a semi final resting place for the ISI from BSC 10 to be removed today.

[Hugo, Rodica, Paul]

Today we were finding it impossible to lock the IMC again. When we looked at the SUS-MC2-M3_LOCK_L_OUT_DQ channel, the signal appeared to be always railing (on both sides). We have seen this before at times, due to very noisy seismic states (see e.g. entry 5145). However, even with what we expected to be a quiet siesmic and ISI state, we still found this signal railing at ±40,000 counts, making it impossible to lock using the length path. In the end, Hugo realised that when the model was recently updated, the limit on the MC2 M3 lock filters had reverted to its initial old value of 40k counts. Apparently at some point this was increased to 400k counts, but not saved in a safe.snap file. Hugo increased the limit back to this value and the mode cleaner began locking again.

We should update the safe.snap file so that any further reboots revert to the 400k counts limit.

Attached are plots of dust counts > .3 microns and > .5 microns in particles per cubic foot requested from 5 PM Feb. 5 to 5 PM Feb 6. Also attached are plots of the modes to show when they were running/acquiring data.

Data was taken from h1nds1.
1440.0 minutes of trend displayed

Transfer function measurements are running overnight on HAM3-ISI.

Active control will be turned back on once it is done.

• Ski: Mid X A/C is off, so is ok if alarm FMCS -> AIRHANDLERS -> mx -> H0:FMC-MX_AH_COOLTEMP_2_DFGF is on.
• Ski: personal of "Control Solution..." will be around.
• LVEA was laser safe.
• Cyrus working on upgrading switches and cables at control room.
• Apollo working at BSC2, BSC1
• Cardboard container was picked up and brought back
• Betsy, et al, looking at suspenstions at LVEA
• Richard went to EY
• Safety meeting at 3PM

Starting Monday the HAM3 HEPI was unlocked for the L4C leveling.  Each corner is relocked during that corner's leveling work.  As the work proceeds there is invariably some position change but the process is done intended not to move things.  It works pretty well with most horizontal changes counteracting one another in the end.

At first unlocking, the HAM HEPI (& presumably the ISI and Optical Table Payload) moved a small amount:
<1mil X or Y and < 1urad Rz.  There was a drop of the platform of 1.1mil(0.0011") the four corners dropping close to the same but different enough to yield a 1.7urad Ry but only 0.5urad Rx.

After the last Corner was completed the total motion from the Monday (unlocked) position was:
<1mil X or Y and -3.5uradRz.  The payload came back up 0.1mil and rotated about the X & Y axes each -1.1urads.  This will presumably be the final floating (no DC HEPI drive) when next released.  Who know what actually having fluid flowing though HEPI will do even though it should be unaffected.

The system was relocked and the motion after this (where it will be for some time) is as follows:
Again, less than a mil X or Y and -1.6urad Rz.  The table is a bit higher, .5mils with -2.2urad Ry & <.1urad Rx.

How the heck does he do it? you ask.  Well, the Inductive Position Sensors are 655cts/mil sensitive, by watching the readings while being locked the position can be held to a few hundred counts at worst, and by careful reconnection of the Actuator so it is not stressed.

Turns out we left cables attached to the TFIN and TFA/B inputs on the PMC field box in the racks, with the MEDM switch enabling the TF path. Removing the cables got rid of the noise, and I disabled the path. There is still some 60 Hz noise but it is nothing like it was before.

This is something we've forgotten since the science run ended...always check the cables when noise hunting!!

MitchR, JimW BSC2 was unlocked and balanced this morning, mostly problem-free (except for a CPS power cable that had come unplugged) requiring only small changes to the BSC's trim mass on both stages. Locked/unlocked shifts are <500 cts for St1 and <1000 for St2. SUS's C3 cover and optic shields were carefully removed and are sitting on the nearby tables if needed (please notify SEI people before re-installing these). The ISI was left floating  for testing, while we have the window.

 For some reasons the big offset that had been observed at ASC_ADC_1_7 [1][2] disappeared at around 11:24 AM this morning and never came back. I think this corresponds to the time when I was unplugging the SCSI cable of the AA board. I was trying to look at the raw voltage coming out from the AA board and so for the reason I was attaching a SCSI break out board. I didn't see any raw offset at the time, put the cable back to place and realized that the offset had been magically gone. This is strange because yesterday it came back after I unplugged and plugged the SCSI. This doesn't mean the issue is solved, but anyway we will keep our eyes on this particular ADC channel and AA board.

After the offset was gone, I checked the signal chain from the inputs of the QPD interface box through the whitening filter and ADC to the digitized numbers by injecting analog excitation signal (0.01 Vpp at 3 Hz with DS345). This was a part of the QPD check. The digitized value agreed with an expected count of +/-550 counts with the whitening off. So I conclude that the ADC and AA board are healthy at this moment.

Note :
 one of the QPD interface box [3] in the ISC R4 rack doesn't have a frequency response. It is documented in [3]. The rest of two guys do have a frequency response as designed.

[1] LHO alog 5371 "offset at ASC_ADC_1_7 seem from the AA board"
[2] LHO alog 5373 "Maintenance summary"
[3] S1102815-v3 "ISC Dual QPD Transimpedance Amplifier Chassis"

Commencing Matlab TFs on the BS.

• Cyrus working on upgrading switches. This took out communication from the medm screens to the frontends for most of the morning, but everything has come back up
• Unifirst on site
• Praxair delivered to CP2
• Paradise water on site
• Kiwamu and Max working on the ALS fiber pick off from the reference cavity
• Dave edited the h1iopseib6 IOP
• Betsy working on the beamsplitter
• Michael L and Apollo removed ETMY optic
• Michael L gave tour in LVEA

Somehow the hypothesis has been that the peak in the MC OLTF is the structure in FSS and we should be able to mitigate that guy if we retune the FSS notch.

That was attempted today, but the problem is that the peaks the FSS notch is notching out are at about 780 kHz, and MC "peak" we're talking about is a rather broad thing at around 710 kHz. We could move the FSS notch to there, but if we do that the FSS structures are almost totally out of the notch. See attached. Note that the MC OLTF was measured without Evans Notch (TM).

It's clear that the "peak" we're talking about is not the FSS peak per se, it's either a simple gain peaking or something that is not there in FSS. Keeping Evans Notch (TM) sounds fine to me, but if somebody feels the need to put move it out on the option board in the common mode board, please feel free.