We calculated the distribution of carrier Contrast Defect over the lock segments attached in 37560. The contrast defect has been evaluated according to B1p photodiode (upstream wrt OMCs), so including all the HOMs: CD = B1p/(B1p + 10.47 B4). The overall outcome including all the data of C8 is shown in figure 1, with a typical value of CD = 5.7e-4. The fact that no multi-peak distribution is evident means that basically the ITF working point of the ITF at dark fringe does not vary significantly.

In figure 2, one typical lock segment is shown with most occurying value CD = 5.7e-4 (top plot) absolutely comparable with the overall result of figure 1. In the same figure, bottom subplot is the time evolution of theCD for the same segment. Finally, the carrier gain in the recycling cavity has been computed for the latest segment (figure 3), resulting in value ranging from Gcar = 35 to 39 depending on the photodiode used. Those values are in agreement with usual findings, but work is ongoing to better pinpoint this estimation.

Here is a histogram of the durations of the 37 segments in the C8 run.  Most of the segments were >1k seconds in duration.

In correspondance a large glitch can be seen on the PMC transmitted power (see first plot).

Looking to the second plot, we could conclude that the gitch origin is at the level of SIB1 bench (we can see it on the IB_tx, ty and tz dofs).

Consequently this creates a glitch on the power stabilization photodiodes (located on SIB1 bench lower part) which generates a glitch on the correction

sent to the slave laser diode 2 and then a glitch on the PMC transmitted power. More work is needed to better understand the origin of those glitches.

It could be good to give a look around the IB tower to find the origin of the glitch. It might come also from inside the tower but in that case it wiil harder to find.

We added a roll-off filter to the TX (and TZ) control of SDB1.

It seems that the coherence between error signals of SDB1 in TX and DARM has been killed, see figure attached (purple is during C8, blue is after adding a roll-off).

We are not sure the filter used to control SDB1_TX is optimal, let's see how things are with the roll-off, it might be a good idea at some point to inject noise and find a better filter for the control of SDB1 in TX

No, there is no evidence of B7/B8 arches coupling to DARM.

The only coupling I identified is scattered light in LSC_B4_DC also seen in LSC_MICH_ERR.

Here links to bruco tables of a few target channels during C8:

• LSC_DARM_1178172318/
• LSC_DARM_1178172318_ENV/  (DARM coherence with all *ENV* and *Clock* signals, see comments in 37499)
• LSC_B8_DC_1178172318/
• LSC_B7_DC_1178172318/
• LSC_B4_DC_1178172318/

Maybe worth to note how bruco did spot a relevant coherence with SDB1_LC_TX at the 31Hz and all other SDB1 mechanical resonance: see attached Figure 1.

B7, B8, and also B4, DC channels show little coherence with all other channels. This is might be consequence of the fact that these signals are dominated by scattered light. This seems indeed the case for B7_DC and B8_DC.  Actually also B4_DC shows some arches (Figure 2),  to be better checked with Omicron.

Scattered light glitches as seen by Omicron in B8.

In this spectrogram, arches are well resolved. The periodicity is ~1.4 s. The SNR is huge : several hundreds. As noted in the previous post, we see secondary arches and some echo around the ~80 Hz line. All channels processed by Omicron were checked. These arches are only seen in LSC_B8_6MHz_I with a much weaker intensity.

Similar arches were observed in the B7 signal.

This entry comes a bit late, since our crew has already spotted it and is working to reduce frequency noise. However.... as Figure 1 shows, there is significant coherence between DARM and SSFS in the region 20-100Hz.

The rightmost of the 30Hz double-peak structure is associated to frequency noise: this is precisely at 30.8Hz, and matches to a peak in the SIB1 angular signals particularly intense in tz: see Figure 2. This peak is also coherent with ENV accelerometers on IB as indicated by bruco.  This peak seems one of the SIB1 mechanical resonance which was troubling SSFS in January.  Reminder: the leftmost one of the double-peak, at 29.8Hz, is not coherent with SSFS and has been found to come from SDB1. 

A structure similar to the 30.8Hz is present at 62.5Hz, probably another SIB1 tz mode: see Figure 3.

Last to note among SSFS contaminations (look again Figure 1) is the 1Hz comb showing between 40Hz and 50Hz. It is not coherent with *Clocks* but with CEB magnetometers and power line sniffers. The suspected source is the CT heaters. It looks the same which was noted in February and March.

The fluctuations of the sensitivity are dominated by the power fluctuations of B1p, which are due to the fact that the ITF alignment is not yet controlled by the quadrants (fig 1).

When the noise is high a lot of structures grow, which resamble to mechanical resonances (fig 2).

A good candidate to be the source of that noise is the angular control of SDB1. Fig 3 is the transfer function between SDB1_LC_TX_corr and DARM,  when the noise is maximally coupled.

Typical arches are visible in the spectrograms of both B7 and B8_DC, they look uncorrelated between the two. The periodicity of arches looks around 10s.

At WE there is evidence of double arches, and also the scattered light pattern looks modulated by a 78.6Hz line .... which is not in ENV channels.

I had a look at LSC_DARM coherences with ENV* channels.

here the bruco table: 1800s from May 7, 6:05 UTC, https://scientists.virgo-gw.eu/DataAnalysis/bruco/2017-05-07/LSC_DARM_1178172318_ENV/

Figure 1 is the "ENV budget" made projecting coherences, channels are divided by Type of noise (RED are all *ACC* and *SEIS* channels, and so on ... see the plot legend)

• major coherent contribution is seismic, 150-450Hz

Figure 2 shows the SEISMIC "sub-budget", indicating LOCATIONS of most coherent seismic channels:

• small line at 31Hz  (... it is NOT the big structure at 29.8 Hz) and 101Hz line are coherent at IB tower  (Figure 3)
• structures in the 150-450Hz zone look mostly coherent with accelerometers in DT zone (Figure 4)

I extracted the name of max coherent channel at the most prominent spectral peaks:

% freq(Hz) (ASD) maxCOHE channel
f=31.01 (ASD=   2e-07):  0.13 V1:ENV_IB_ACC_X
f=101.07 (ASD= 2.4e-08):  0.52 V1:ENV_IB_BD_ACC_Z
f=206.42 (ASD=   2e-09):  0.30 V1:ENV_EDB_ACC_Z
f=269.41 (ASD= 8.6e-09):  0.29 V1:ENV_NI_CT_ACC_Z
f=336.79 (ASD= 2.7e-09):  0.58 V1:ENV_DT_ACC_Z
f=409.55 (ASD= 3.8e-09):  0.04 V1:ENV_DT_ACC_Z
f=440.19 (ASD= 3.6e-09):  0.09 V1:ENV_DT_ACC_Z
f=456.54 (ASD= 5.7e-09):  0.19 V1:ENV_SPRB_LINK_ACC_Z
f=463.01 (ASD= 4.9e-09):  0.30 V1:ENV_NI_ACC_X
 

Some statistics of the metatron states:

Statistics for ITF_STATUS for period from gps = 1178028018.0 (2017-05-05 14:00:00 UTC)
to gps = 1178262018.0 (2017-05-08 07:00:00 UTC). Total duration 65:00:00 hour
 cnt  min    max   mean  med   pct  idx name
   2  132    303  217.5  217  0.19    0 INIT
  50    2    447  132.8  121  2.84   10 NOT_LOCKED
  50    5    725  318.2  346  6.80   20 LOCKING
  69    1    815  111.0   91  3.27   30 LOCKED
  37    2  19699 5466.2 3359 86.43   40 SCIENCE
   5   51    674  220.2  122  0.47   90 ADJUSTING
   2    2      2    2.0    2  0.00  110 STOP

Statistics for ITF_LOCK for period from gps = 1178028018.0 (2017-05-05 14:00:00 UTC)
to gps = 1178262018.0 (2017-05-08 07:00:00 UTC). Total duration 65:00:00 hour
 cnt  min    max   mean  med   pct  idx name
   2    6     25   15.5   15  0.01    0 INIT
  49   24    448  139.1  123  2.91    1 DOWN
  53    5     98   31.0   28  0.70   40 LOCKING_ARMS
  52    2      2    2.0    2  0.04   41 LOCKED_ARMS
  52    6     18   13.6   14  0.30   60 LOCKING_RECOMBINED
  48    2    467   12.0    2  0.25   61 LOCKED_RECOMBINED
  47    7     10    8.6    9  0.17   70 LOCKING_CARM_DARM
  46    2      2    2.0    2  0.04   71 LOCKED_CARM_DARM
  45    1      3    2.8    3  0.05   80 ACQUIRE_CARM_TO_MC
  44    5     10    8.8    9  0.16   81 LOCKING_CARM_TO_MC
  43    2      2    2.0    2  0.04   82 LOCKED_CARM_TO_MC
  43   18     27   25.5   26  0.47   90 LOCKING_SSFS
  42    6    481   17.9    6  0.32   91 LOCKED_SSFS
  42   10     12   10.1   10  0.18   94 CHECK_QUADRANTS
  43    1      6    4.6    5  0.08  101 ACQUIRE_PRITF
  43   25     30   27.1   27  0.50  102 LOCKING_PRITF
  43    7    160   12.6    8  0.23  103 LOCKED_PRITF
  42    8      9    8.6    9  0.15  106 REDUCING_MICH_OFFSET_0_3
  42    2     11    2.2    2  0.04  107 PRITF_MICH_OFFSET_0_3
  42    2      7    6.5    7  0.12  108 B7B8_PD_SWITCH
  40    4      5    4.5    5  0.08  109 REDUCING_MICH_OFFSET_0_2
  40    2      6    2.1    2  0.04  110 PRITF_MICH_OFFSET_0_2
  40    2     10    9.1    9  0.16  111 REDUCING_MICH_OFFSET_0_1
  39    5     96   32.4   26  0.54  112 PRITF_MICH_OFFSET_0_1
  35   16     19   17.8   18  0.27  119 LOCKING_PRITF_DF
  35    2      2    2.0    2  0.03  120 LOCKED_PRITF_DF
  35    7      9    8.1    8  0.12  121 ACQUIRE_LOW_NOISE_1
  35    8      9    8.1    8  0.12  123 LOW_NOISE_1
  35   77    261  116.1  108  1.74  124 LOCKING_OMC1_B1s2_DC
  36   64  19927 5858.8 3789 90.14  125 LOCKED_OMC1_B1s2_DC

In attached the Science Mode duty cycle of C8 - Run

today, i have found the ITF locked in "LOCKED_OMC1_B1s2_DC" science mode. Successfully achived a 4 hours lock (5.26 UTC - 9.28 UTC) - we reached 3.4 Mpc BNS see the attached plot

ITF events:

- ITF found in Science Mode
- 5.05 UTC ITF unlock for no ubvious reasons;
- 5.13 UTC locked in ITF locked in "LOCKED_OMC1_B1s2_DC"
- 5.26 UTC ITF science mode
- 9.28 UTC ITF Unlock for no ubvious reason
- 9.34 UTC locked in ITF locked in "LOCKED_OMC1_B1s2_DC"
- 9.36 UTC unlock
- 9.42 UTC unlock during locking procedure
- 9.44 UTC performed PR alignment
- 9.54 UTC unlock during locking procedure
- 10.07 UTC locked in ITF locked in "LOCKED_OMC1_B1s2_DC"
- 10.09  UTC ITF science mode
- 10.20 UTC unlock
- 10.30 UTC "LOCKED_OMC1_B1s2_DC"
- 10.33 UTC science mod
- 11.39 UTC unlock maybe caused by earthquake (Earthquake ID us10008qa)
- 11.48 UTC "LOCKED_OMC1_B1s2_DC"
- 11.51UTC science mod

On Call

-8.27 UTC D. Soldani informed about HVAC..WEB_COLD_TE_ERR,60 red flag on DMS. To be fixed in the next maintenance 

Vpm

• 2017-05-07 10h26m45 UTC    sposito process:ParseSeismonProcessing started
• 2017-05-07 10h27m15 UTC    sposito process:FdIOTCS started

Earthquakes :

1 - Current time: GPS = 1178171607, 2017-05-07 05:53:09+00:00 UTC, IFO = V1
Earthquake ID us10008q8u; occurred at GPS 2017-05-07 05:29:05+00:00 (1178170163 UTC,
1444 seconds ago)
at Unknown (18666 km away)
with an estimated magnitude of 5.0 (depth = 33.5 km, azimuth = 322.7)
Latitude = -34.5 degrees, longitude = -179.7 degrees, distance = 18666 km

2 - Current time: GPS = 1178178259, 2017-05-07 07:44:01+00:00 UTC, IFO = V1
Earthquake ID nn00588166; occurred at GPS 2017-05-07 07:39:38+00:00 (1178177996 UTC,
263 seconds ago)
at South Spring Street,Lincoln County,Nevada,United States of America (9456 km away)
with an estimated magnitude of 3.0 (depth = 9.0 km, azimuth = 36.5)
Latitude = 37.4 degrees, longitude = -114.5 degrees, distance = 9456 km

3 - Current time: GPS = 1178180919, 2017-05-07 08:28:21+00:00 UTC, IFO = V1
Earthquake ID us10008q9i; occurred at GPS 2017-05-07 08:08:32+00:00 (1178179730 UTC,
1189 seconds ago)
at Vavaʻu,Tonga (17198 km away)
with an estimated magnitude of 5.0 (depth = 10.0 km, azimuth = 354.9)
Latitude = -18.5 degrees, longitude = -172.6 degrees, distance = 17198 km

4 - Current time: GPS = 1178192805, 2017-05-07 11:46:27+00:00 UTC, IFO = V1
Earthquake ID us10008qak; occurred at GPS 2017-05-07 11:29:19+00:00 (1178191777 UTC,
1028 seconds ago)
at Suak Timah,Aceh,Indonesia (9338 km away)
with an estimated magnitude of 5.0 (depth = 49.7 km, azimuth = 313.4)
Latitude = 3.9 degrees, longitude = 95.9 degrees, distance = 9338 km

The following plots show the different injected lines and their effect on DARM after having increase the amplitude of the 50 Hz lines (reload of CALnoise at 10:39 UTC).

Figure 1: The lnes sent to NE, WE and BS have a snr of ~100 in DARM. The line sent to PR is not seen in DARM around 50 Hz but is seen with SNR ~5 around 350 Hz.

FIgure 2: modulus and phase vs time of the DARM/CAL_MIR_Z_CORR TF at the line frequencies. As expected, the fluctuations of the NE, WE, BS modulus and phase around 50 Hz are lower since the line amplitudes have been increased.