[Peter, Koji]

Follow up entry for ALOG LHO 41420

Sheila, Jeff K, Hugh, Jamie, Sheila

We did some investigating of why the signs were flipped on the AS centering loops, which was made more difficult by some SDF confusion.

Sign flip

The reason why the sign was flipped for the AS centering loops was explained in 40853, Jeff corrected an error in the sign convention for the tip tilts.  This means that the signs will also be wrong for the refl centering loops and the OMC ASC loop that feedsback to OM3.  This probably also explains part of the difficulties that T Vo had in closing the OMC ASC loops. 

I've flipped the sign of all REFL and AS centering loops, and flipped the sign of the OM3 actuation for the OMC ASC by changing the sign in the output matrix (DOF2TT).  I accepted these in SAFE.snap and observe.snap

SDF confusion

Last night when Terry and I realized that we could only close the AS centering loops by flipping the sign, we looked at the SDF file for the OMs (which are on the SUSOMC model).  We saw that in the observe file (which is the same as the safe file) all the outputs were turned off, which doesn't make sense.  This led to not trusting SDF.  Jeff went back through the autoburt snapshots and realized that some wrong settings were stored in SDF when the OMs were moved to the OMC model (38827).  

Currently when new channels are added to a model, they are not monitored in SDF.  It would be better if the default were to monitor new channels.   

[Aaron Viets, Alex Urban]

I modified the filter generation code to store a transfer function for the pcal correction factor. The name of the numpy array is "y_arm_pcal_corr."  It is an array with 3 rows, the first of which is frequency (0 to 8192 Hz in increments of 0.25 Hz), and the next two of which are the real and imaginary parts of the transfer function at that frequency. So, for example, to get the pcal correction factor at 100 Hz, you would do:

filters['y_arm_pcal_corr'][1][400] + 1j * filters['y_arm_pcal_corr'][2][400]

Unfortunately, we don't know a way to store complex values in the filters files, so this is haw we have to store them (for now, at least).

I made two filters files for LHO, one for GDS and one for DCS. They are in the calibration SVN under aligocalibration/trunk/Runs/O2/GDSFilters/ and the names are:

• H1GDS_highpass_1175954418.npz
• H1DCS_highpass_1173225472.npz

They are valid for the last portion of O2, the same time periods for which the latest filters were used as listed on the O2 calibration configurations wiki.

I did a quick spot check to see that the transfer functions were computed correctly, by just comparing their values at the calibration lines to the values included in the filters for those lines, which we know to be correct.

Sheila, Craig

Since Koji and Peter have replaced the PSL EOM, the phase of IMC PDH error signal is altered.  Shelia and I went out to the PSL racks and looked at the I and Q demodulated IMC error signal.
To get the carrier PDH slope to be along I, we adjusted the error signal delay from 6.4375 ns to 13.4375 ns.  
You can see the rotation of the IMC PDH error signal in plots 1 and 3, which are pictures of the I and Q demodulated error signal in an XY oscope plot.

Adjust the mirror mount before the rotation stage and the one at the base of the IO periscope to
partially bring the beam back to the input modecleaner.  One can certainly see flashes as MC2
swings.  The knobs were moved less than 1/16 of a turn in both axes.

    I limited the power to the input modecleaner to 5 W by using the half waveplate and polariser
combination at the output of the pre-modecleaner.  The output of the photodetector on the table that
monitors the power going into HAM1 did not change appreciably from ~60 mV.

    Since the new EOM is not resonant at 24.1 MHz and because of some changes to the RF signals, the
phase and sign of the error for the input modecleaner may need some adjustment.

Calum, Craig, Luis, Georgia, Peter, Travis, Betsy, Filiberto, Ed, Richard, Rich

We had a hard time tracking down the source of an open circuit in a single wire(Y-axis, negative leg of the differential signal sent from the electrometer out from the vacuum system) of the electrometer cabling.  We spent much time taking every section of the cabling apart (air and vacuum) only to find that we couldn't see any problem.  We are absolutely certain that this pin was not functional at the start of our hunt, but somewhere in the process it fixed itself.  Very disturbing.

We were able to verify the performance of all aspects of the design, but as we hoped, we now have a list of tweaks that we will apply to the electrometer back at CIT. A timeseries of the differential signals coming out of the EFM revealed the background noise in the chamber to be of order 50mV pk-pk.  We were able to easily see people moving around in the chamber, and were able to see the door cover being flapped around by Georgia (when we asked her to flap it).

1.  We feel the gain in the EFM should be increased by up to a factor of 100.  We will add a bit of gain inside the EFM, then add more gain to the in-air part of the system.  This is to ensure the background field noise is above the ADC input noise (whitening).
2.  We will improve the mechanical mounting of the calibration plates such that it is easier to shift them from one axis to another
3.  We will improve the robustness of the serial communications link used to adjust the common-mode rejection ratio (CMRR) as this proved problematic.
4.  We want to limit the high frequency bandwidth of the EFM.
5.  We want to investigate a 1.7MHz oscillation seen when the field meter was swung causing an electrical saturation.  It appears to be phase reversal on one of the amplifiers.  This went away upon power cycling.  

We verified that the CMRR can be adjusted in situ to better than -60dB.  We also concluded that this adjustment should be done in-chamber as the bench results taken in the optics lab were different than the results obtained in the installed environment.

We verified the 'dark' noise of the EFM to be approximately 200nV/rtHz at 100Hz, which is consistent with design

We measured the background differential noise in X and Y to be approximately 5uV/rtHz at 100Hz as measured at the differential output at the rack (plots to follow).  I believe the calibration of this device to be approximately 64mV per volts per meter at 100s of Hz or so, although this needs to be further investigated (I get this from 16mv/v/m times 2 for differential sensitivity, times 2 for the differential driver gain).  As Rai cautioned us, we need to be careful with the plate spacing distance due to irregular features between the plates (copper buttons), but a simplifying view is given by the capacitances between the calibration plate - sense plate - and ground of the EFM body.  The observed ambient spectrum seemed a bit devoid of features to me and was approximately a factor of 10 lower than the field observed in the optics lab.

The following in vacuum cabling was added to ETMx for the Electric Field Meter (EFM). While the EFM is not the final version the cabling installed is the final version.

We added LIGO-D1800089-v2  SN S1800629 and LIGO-D1800090-v1  SN S1800631.

With reference to page 11 of the LHO ETMx in vacuum cable routing drawing, LIGO-D1300007-v2 , these above additions were placed in the existing ISC-QPD (532 NM) path.

It should be noted that a 15-pin cable bracket, LIGO-D1800072-v1 was also added between the 15 pin sections. However, the wrong base was sourced for the required cable bracket, LIGO-D1001347-v3, between the new LIGO-D1800090-v1 and the existing D1000924. So this is pending. Either a new based has to be sourced or 3 cable portion replaces the existing 2 cable portion of D1001347 on the table.

We will update the required SYS drawings to match this (and ICS).

   Added 150ml cooling water to PSL Crystal chiller. Diode chiller water level is good. No change to both filters.    

Aligned beam onto the PDB photodetector in the ISS PD box.  Also realigned the beam onto the quadrant photodiode.
The effect of which can be seen in the attached plot.

    Engaged the first loop power stabilisation this morning without much hassle.  The calculated diffracted power
percentage is off as the coefficients need to be calculated.

    Without doing some loop measurements, the gain slider setting of 18 dB maybe the wrong value.

Due to hardware BIO logic change in the ISS 2nd loop board (D1600298, HIGH/LOW=NO/NC in V2, HIGH/LOW=NC/NO in V3), I removed or added NOT in all relevant BIO control and readback channels in psliss frontend.

I removed  H1:PSL-ISS_SECONDLOOP_REFERENCE_VALUE_CAL filter and H1:PSL-ISS_SECONDLOOP_REFERENCE_VALUE EPICS channel, these were necessary before as the slow offset loop and digital excitation combined had one dedicated analog input, now these are added together with the 3rd loop. This analog input was reassigned to the BNC input on the chassis.

I just saved the model but hasn't compiled yet.

Summary:

We're reviewing the HWS SLED situation.  We have only one spare for the ITMX SLED and no spares for the ITMY SLED.

We're averaging about one SLED every 8 months during intensive usage.

ITMY

• April 2015: replacement [ITMY: QSDM-840-5 12.02.44]: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=18069
• July 2016: replacement [ITMY: QSDM-840-5 07.14.264] https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=28162
• October 2016: replacement [ITMY QSDM-840-5 07.14.265] https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=30257
• May 2017: replacement [ITMY - QSDM-840-5 7.14.266]: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=36174

ITMX (not used as much before in-vac lens fix)

• March 2016: status check [ITMX QSDM-790-5: 12.05.21]: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=25907
• July 2016: replacement [ITMX QSDM-790-5: 07.14.256]: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=28358
• April 2017: replacement [ITMX QSDM-790-5: 07.14.254]: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=35486

In storage cabinets next to BSC3.

• QSDM-790-5: 07.14.255 [should be okay]
• QSDM-790-5: 07.14.256 [dead]
• QSDM-840-5: 07.14.265 [dead]

At the request of the controls engineer, the Yend HEPI platform was unlocked.  No issues other than the usual terrible access in unlocking.

Ran Cartesian Range-of-Motion tests of 0.5mm for DOFs X Y Z RX RY & RZ.  Probably sufficient to do X Y & Z but forgot about that before getting started.

The attached plot shows the X Y Z Range of Motion with the local sensors over laying one another.  This shows no bad actors of local sensor clipping, slope differences or changes.  HEPI is clear to +- 0.5mm.  Will check larger ranges most importantly for Y (tidal) another time but this will get us by for now.

The HEPI and ISI platforms are Isolated.

The TCS chiller pump has been rebuilt and should be ready to act as a back-up now. In the future if the water pump needs to be rebuilt it uses a a type 21 shaft seal, 5/8" shaft size, 1 1/4" seat bore. The replacement o-rings are 4x dash number 012 and 1x dash number 242. It also uses a standard external retaining ring with a 5/8" OD. Use a light grease to seat the shaft seal, or else the rubber will tear (voice of experience here, oops).

 The chiller is currently running in a small closed loop to see if any leaks develop overnight, it is on the mezzanine with its other siblings.