This is a low level sanity check and a part of the recent delay study (e.g. 29259). I have measured a transfer function between DARM2_OUT and SUS-ETMY_L3_ISCINF_IN1 using dtt while the interferometer was locked last night. The measurement agrees with 1 cycle user model delay (=61 usec). See the attached.

WP6220 Inclusion of DBB channels to DAQ to monitor jitter of HPO

Daniel, Dave:

a new h1psldbb model was installed and the DAQ was restarted this afternoon (14:50 PDT). Daniel decided that this version initially write its fast channels to the commissioning frame only while the ECR for science frame inclusion was being processed. Daniel's ECR (E1600301, FRS6386) has been approved and these channels will go into the science frame on the next DAQ restart.

Krishna had noted in a log in the secret SEI logbook that the endstation BSC tilt subtracted sensor correction wasn't performing as well as the corner station sensor correction. This seems to have been due to a high pass added to the tilt subtracted seismometer path. This filter is supposed to help suppress signal from the BRS 8mhz resonance, but it seems to have been distorting the phase of the STS signal too much at 100mhz. The first attached plot is of an older (I think) high pass in red and the "problematic" high pass in blue. I've switched ETMX to the "old" high pass, second plot are the ground STS to St1 T240 tf for each endstation. Red trace is EX, blue is EY. It's subtle, but EX is doing better in the 100-200mhz band, if you squint. I'm going to leave the endstations in this configuration overnight, while people in the seismic group can come up with reasons why this is a bad idea.

Jenne, Evan

We looked again at RFAM on the 9 MHz REFL readout.

The attachment shows REFL9I (and REFL LF) for four different PD powers. Additionally, at the fourth power we locked the ISS outer loop (dc coupled with boosts) just to check that the RFAM does not change. The REFL centering loops were on the whole time.

At no power were we able to see anything that looked shot-noise limited, so we were not able to independently check the transimpedance and demod gain for REFL9I. However, the limit placed by the high-frequency noise already seems to indicate that we are missing some gain in the signal chain. Thus far I have been using 2900 V/W for the PD transimpedance plus demod TF, but this would produce spectra that are below the expected shot noise level.

I double-checked the schematics for the REFL LF path and found that the current digital calbration from counts back into watts seems OK. The PD powers given in the attachment are based on this LF calibration.

Finally, note that the dark noise at several kilohertz is larger than the noise when the PD has power on it. No clue about why.

FAMIS#6491

No water was added to the crystal chiller, the water level was at the Max line. The diode chiller did not have a low water level alarm, so I also did not add any water.

Title:  10/06/2016, Day Shift 15:00 – 23:00 (08:00 - 16:00) All times in UTC (PT)
State of H1: IFO lost lock due to PI ring up. IFO was coming back up when I came in. Was able to damp PIs M2 and M10. IFO relocked at NOMINAL_LOW_NOISE with no problems	   
Outgoing Operator: N/A
 
Activity Log: All Times in UTC (PT)

14:20 (07:30) Chris & Apollo – Going down Y-Arm to work on beam tube sealing near CS
14:30 (07:30) Damped PI modes M2 & M10 – IFO relocked at NOMINAL_LOW_NOISE	
14:50 (07:50) Robert – In LEA doing injections
15:10 (08:10) Peter – Going into PSL to adjust power & install new PD (WP #6219)
15:10 (08:10) Christina – Forklift crate from LSB to Mechanical building
15:12 (08:12) Richard – In MSR to replace batteries (WP #6218)
15:15 (08:15) Karen – Cleaning in Optics Lab
16:00 (09:00) Kiwamu – Going into PSL for PD install (WP #6219)
16:09 (09:09) Karen Out of Optics Lab
16:20 (09:20) Peter & Kiwamu – Out of PSL
17:32 (10:32) Robert – Running injection
21:45 (14:45) Dave – Adding new DBB signals to frames & DAQ restart (WP #6220)


Shift Details: 10/06/2016, Day Shift 15:00 – 23:00 (08:00 –16:00) All times in UTC (PT)
Support: Cheryl,               
Incoming Operator: Travis

Shift Summary:  Broke lock around 14:00 (07:00) due to PI ring up. At around 14:30, damped PI Mode #2 by changing phase from 30 to 80 and PI Mode #10 by changing phase from 30 to 80. Modes responded quickly and we relocked at NOMINAL_LOW_NOISE with no problems. 
PI Modes 2 & 10 rang up again – damped mode 2 buy changing phase from 80 to 30. Damped Mode 10 by changing phase from 80 to 60.
Most of shift spent in commissioning and relocking. 

Following up on entry 30273, I computed the coherence and transfer function between ISS_PDA_REL_OUT (which should be calibrated in RIN units) and CAL-DELTAL_EXTERNAL (including the proper calibration). Coherence is good enough to estimate a transfer function over all the frequencies above 10 Hz. I'm not injecting any additional noise, just using the signals as they are, so the fact that we have coherence doesn't necessarily mean that we really have a coupling of intensity noise to DARM.

However, the transfer function has a very interesting shape (see figure). It's behaving like 1/f^3 up to ~80 Hz, and above that frequency it increases like f. The region below 80 Hz might very well be consistent with radiation pressure coupling of intensaity noise. We'll have to run some numbers to be sure that this makes sense. I have no clear explanation of the increase above 80 Hz.

Addition:

A quick and dirty estimate of the expected coupling of RIN at the ISS PDs to DARM due to radiation pressure

x = 2 deltaP / c / (m * (2*pi*fr)^2) / (fr / fr_pole_doublecav) = 2 P_arm / c / (m * (2*pi*fr)^2) / (fr / fr_pole_doublecav)  * RIN

At 30 Hz the coupling should be about 2e-11 (maybe off by a factor of 2 or so due to the two arms, etc..). This is many orders of magnitude LARGER than what measured in the TF discussed above. So it is unlikely that PDA/PDB see real intensity noise that goes into the IFO.

I ran a BruCo scan for the last night lock, using ten minutes of data when the range was at ~65 MPc. Results are available here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1159774937/

Summary

There is a lot of coherence a bit everywhere:

• at low frequency (<100 Hz) the auxiliary longitudinal d.o.f.s win: MICH, SRCL, PRCL, see figures 1,2 and 3
• below 50 Hz the most significant angular control signal is ASC-AS_B_RF45_Q_YAW (fig. 4)

The "jitter noise" above 100 Hz shows a lot of coherence with many signals, of different origins. Most of the IMC WFS signals are coherent, for example: IMC-WFS_A/B_DC_PIT/YAW_OUT (fig. 5 and 6).

The most interesting coherence is however with the intensity stabilization: PSL-ISS_PDA_REL_OUT and PSL-ISS_PDB_REL_OUT shows quite large coherence, as well as the ISS control signal: PSL-ISS_AOM_DRIVER_MON_OUT. It seems that PDA and PDB (first loop ISS) are completely dominated by what the ISS second loop is doing (as shown by the control signal). The coherence with DARM in the 100-1000 Hz region is very close to one. See fig. 7 and 8.

Note that in the same 100-1000 Hz region, the coherence with PSL lab accelerometers is also significant, but mostly on the peaks (fig. 9)

En passant, a narrow feature at 56.75 Hz and 113.50 Hz are coherent with EX magnetometers (PEM-EX_MAG_EBAY_SEIRACK_X/Y PEM-EX_MAG_VEA_FLOOR_Y/Z)

Multicoherence

I selected the channels with the largest coherence from the BruCo report, and run a multicoherence code.

chnames = {'H1:LSC-MICH_OUT_DQ', 'H1:LSC-SRCL_OUT_DQ', 'H1:LSC-PRCL_OUT_DQ', ...
            'H1:ASC-AS_B_RF45_Q_YAW_OUT_DQ', 'H1:ASC-OMC_B_YAW_OUT_DQ', 'H1:ASC-OMC_B_PIT_OUT_DQ', ...
            'H1:LSC-REFL_A_RF45_I_ERR_DQ', 'H1:LSC-REFL_A_RF9_Q_ERR_DQ', 'H1:IMC-WFS_A_DC_PIT_OUT_DQ', ...
            'H1:IMC-WFS_B_DC_PIT_OUT_DQ', 'H1:IMC-WFS_A_I_YAW_OUT_DQ', 'H1:IMC-WFS_A_Q_YAW_OUT_DQ', ...
            'H1:PSL-ISS_AOM_DRIVER_MON_OUT_DQ', 'H1:PSL-ISS_PDA_REL_OUT_DQ', 'H1:PSL-ISS_PDB_REL_OUT_DQ', ...
            'H1:PSL-ISS_SECONDLOOP_RIN_INNER_OUT_DQ', 'H1:PSL-ISS_SECONDLOOP_RIN_OUTER_OUT_DQ', ...
            'H1:PSL-PMC_HV_MON_OUT_DQ', 'H1:IMC-IM4_TRANS_SUM_OUT_DQ', ...
            'H1:PEM-CS_ACC_PSL_TABLE1_X_DQ', 'H1:PEM-CS_ACC_PSL_TABLE1_Y_DQ', 'H1:PEM-CS_ACC_PSL_TABLE1_Z_DQ', ...
            'H1:PEM-CS_ACC_PSL_PERISCOPE_X_DQ'};

The code take into account the cross-coherences between channels and produce the total coherence and an estimate of the noise projection, base on that coherence. The last figure (10) shows this coherence and the projection into the DCPD signal. A lot of noise can be explained by the coherences.

So, apparently Peter went into the PSL this morning and adjusted the HWP to give us more power incident on the rotation stage.  However, this was not communicated to commissioners / people in the control room, so the ISC_LOCK guardian was still requesting 60W.  With the hardware change, this was actually giving us ~60W into the vacuum.  Something in the ASC didn't like this, and we lost 2 locks after ~1 hour each, with something drifting away. 

EDIT:  I guess some commissioners did know that we were getting 60W and decided to try running with it, we just didn't think it would have such a deleterious effect on the ASC.

The only oplev which is furthest off (approaching -10urad) is the HAM2 oplev (pit & yaw).  This closes out FAMIS#4696.

J. Kissel, S. Karki

As we've done in O1, we're creating a high-frequency ( > 1 kHz ) excitation via PCALX whose frequency is changed over long-duration in order to map out the interferometer's sensing function out to as high as is needed for burst and binary neutron star coalescence searches. For quite some time now (since July! see LHO aLOG 28301), this line has been gathering data at 3501.3 [Hz]. We haven't moved it because the IFO's duty cycle has been low, the power level has been inconsistent, and our person power has been limited.

Today is the day!

I've resumed moving this line, following the schedule posted by Sudarshan in LLO aLOG 28070, which I repeat here for convenience:

Frequency    Planned Amplitude        Planned Duration      Actual Amplitude    Start Time                 Stop Time                    Achieved Duration
(Hz)         (ct)                     (hh:mm)                   (ct)               (UTC)                    (UTC)                         (hh:mm)
---------------------------------------------------------------------------------------------------------------------------------------------------------
1001.3       35k                      02:00      
1501.3       35k                      02:00     
2001.3       35k                      02:00     
2501.3       35k                      05:00      
3001.3       35k                      05:00                   39322.0           Oct 06 2016 18:39:26 UTC
3501.3       35k                      05:00                   39322.0           Jul 06 2016 18:56:13 UTC    Oct 06 2016 18:39:26 UTC      months
4001.3       40k                      10:00
4301.3       40k                      10:00       
4501.3       40k                      10:00
4801.3       40k                      10:00  
5001.3       40k                      10:00

Several things to note: 
- The line frequency was changed in the middle of the lock stretch.
- This lock stretch has been with the PSL power at 58.7W (we hope to run ER10 / O2 at 50 W).
- Alignment of SRC optics is being slowly changed by commissioners
- Robert has also been playing with Intensity Noise coupling, which is currently limiting the sensitivity at these high frequencies, so the SNR of the line may be varying quite wildly.

• The sleds were swapped back and re-swapped to do the same test as alog29956 (I forgot to swap the launchers then). The result was we had no reflection back from ITMY and ITMX had both 790 and 840 nm reflections. So we didn't learn much from this test. The sleds are now swapped back (790nm on X, 840nm on Y)
• The code has been restarted. No new reference has been taken yet. Waiting for a cool IFO.
• The 840nm sled S/N 07.14.264 is dead. I replaced it with 07.14.265.
• The current sled power calibration is again slightly off from alog25806. I don't see a more recent alog of it being re-calibrated so I'm putting the values back to where it was. I tried to measure the power but I had a hard time zeroing my meter so I don't trust my measurement so much (I measured HWSX sled to be outputting 3mW, HWSY sled 5mW). I accepted the changes in the SDF.

Summary:
Repeating the Pcal timing signals measurements made at LHO (aLOG 28942) and LLO (aLOG 27207) with more test point channels in the 65k IOP model, we now have a more complete picture of the Pcal timing signals and where there are time delays.

Bottom line: 61 usec delay from user model (16 kHz) to IOP model (65 kHz); no delay from IOP model to user model; 7.5 usec zero-order-hold delay in the DAC; and 61 usec delay in the DAC or the ADC or a combination of the two. Unfortunately, we cannot determine from these measurements on which of the ADC or DAC has the delay.

Details:
I turned off the nominal high frequency Pcal x-arm excitation and the CW injections for the duration of this measurement. I injected a 960 Hz sine wave, 5000 counts amplitude in H1:CAL-PCALX_SWEPT_SINE_EXC. Then I made transfer function measurements from H1:IOP-ISC_EX_ADC_DT_OUT to H1:CAL-PCALX_DAC_FILT_DTONE_IN1, H1:IOP-ISC_EX_MADC0_TP_CH30 to H1:CAL-PCALX_DAC_NONFILT_DTONE_IN1, and H1:CAL-PCALX_SWEPT_SINE_OUT to H1:CAL-PCALX_TX_PD_VOLTS_IN1, as well as points in between (see attached diagram, and plots)

The measurements match the expectation, except there is one confusing point: the transfer function H1:IOP-ISC_EX_MADC0_TP_CH30 to H1:CAL-PCALX_DAC_NONFILT_DTONE_IN1 does not see the 7.5 usec zero-order-hold DAC delay. Why?

There is a 61 usec delay from just after the digital AI and just before the digital AA (after accounting for the known phase loss by the DAC zero-order-hold, and the analog AI and AA filters). From these measurements, we cannot determine if the delay is in the ADC or DAC or a combination of both. For now, we have timing documentation such as LIGO-G-1501195 to suggest that there are 3 IOP clock cycles delay in the DAC and 1 IOP clock cycle delay at the ADC.

It is important to note that there is no delay in the channels measured in the user model acquired by the ADC. In addition, the measurements show that there is a 61 usec delay when going from the user model to the IOP model.

All this being said, I'm still a little confused from various other timing measurements. See, for example, LLO aLOG 22227 and LHO aLOG 22117. I'll need a little time to digest this and try to reconcile the different results.