We started at 14:00 UTC and to not interfere with the ITF and risk to unlock, we manually injected the SQZ. 

• System initial status: ITF LOW NOISE 3; SQZ_MAIN @SQZ_Locked_NO_FC

• 14:28:26 AA loop engaged

We performed a first CC phase scan (Fig. 1-2): 

• 14:39 CC scan started DCP = 195 Hz

• 15:02:21 CC scan ended (fast shutter closed), ITF in shot

• 15:26:15 fast shutter opened

• 15:36:22 ITF in SQZ phi0 = 0.65 rad

• 15:39:19 SQB1 TX angle set to 300 (initially at 310)

• 16:42:58 SQB1 X position set to -3200 (original position)

• 16:47:58 ITF in SQZ

After the first CC scan we realized the magnitude was similar to the last shift (entry #64094) even though there should be a higher level of injected SQZ. We decided to try to improve the magnitude by acting on SQB1_TX and SQB1_X DOFs. We worked on this from 15:39:19 to 16:42:58 UTC. Finally we left SQB1_X as it was and we changed the set point of SQB1_TX from 310 to 330 urad. The fluctuations on the magnitude are reduced (Fig. 3).

We then performed another phase scan (Fig. 4-5)

• 17:05 CC scan started DCP = 195 Hz

• 17:28 CC scan ended (fast shutter closed), ITF in shot

After the second CC scan we realized the SQZ angle is actually around 1.05 rad, so we decided to repeat the SQZ mode acquisition.

• 17:39:53 fast shutter opened, ITF in SQZ phi0 = 1.05 rad

• 17:49:08 CC loop engaged, gain=75000 (glitch between 17:54:50 and 17:56:14)

• 17:58:54 ITF in ASQZ phi0 = 2.75 rad

We were able to get another CC phase scan with DCP setpoint at 225 Hz (Fig. 6-7). Fig. 8 reports also the shot SQZ and ASQZ acquisitions made after the scan.

• 18:11 DCP value set to 225 Hz

• 18:44:11 ITF in shot

• 18:46: CC scan started DCP = 225 Hz

• 19:09 CC scan ended

• 19:15:07 ITF in ASQZ phi0 = 2.7 rad

• 19:22:48 ITF in SQZ phi0 = 0.95 rad

• 19:28 DCP value set back to 195 Hz

Errata corridge: the plot of the squeezing level and the BLRMS of the first CC scan (t_start = 16:52 UTC) was erroneously equal to the one of the second CC scan. I attach the correct plot.

I attach the plots for the two CC phase scans performed during the shift of yesterday. I was not able to produce the BNS range plot for the second scan, which is anyway visible in Fig.4.

The second scan started at 18:11 UTC, with the same duration times of shot and CC scan as of the first one.

SHIFT GOAL:

The goal was to perform several CC scan at different SR angle. Nevertheless, due the not optimum condition of the MZ and OPA (waiting for the retuning) we decid to perform a couple of scan without changing the SR angle to check the SQZ alignment-

SHIFT activity:

We started at  16:00 UTC and to not interfere with the ITF and risk to unlock, we manually injected the SQZ. 

• System initial status: ITF LOW NOISE 3; SQZ_MAIN @SQZ_Locked_NO_FC

• 16:10:39 EQB1  fast shutter opened (process: SQZ_ctrl/shutter ‘open’)

After that the CC_loop was engaged and then  the AA (process: SQZ_PLL_AA/ Matrix and Filter ‘AA dither enable’).

• started a CC 4MHz phase scan @ 16:52. 

  • time per point = 6 s

  • - initial phase  = 20 degree

  • - final phase = 230 degree

  • - phase steps = 1 degree

  • - random phase = False

  • - Closed shutter sleep time = 120 s

  • - AA closed on dither = False

  • - cc loop gain   = 75000.0

N.B: No glitch during the scan, it was just before and after (see plot)

In meantime Henning checked the MZ and changed lowered again the offset at 0.035 V due to the humidity  misalignment that spoiled the contrast and induced the set point near the actuator saturation. After the Henning action we redid the scan. 

We stopped at 19.25 after that some data have been collected at the CC phase value corresponding to the SQZ and ASQZ, or better to the minimum and maximum values in the BRMS range @210 MHz and in other ranges.

Further data  and plot in the following comments.

The aim of the today shift was:

• Restarted EQB1_HD_AA and AFC_Ctrl (pending from tuesday)
• Clean up of usless channel and reduction of the data stream
• Switch off of EQB1 Thorlabs Actuator, SQB1 and SQB2 Pico
• Added in the automation the possibility to save again the channels of FC_IR, FC_GR and HD (SQZ_MAIN)
• All the states with IR are no more requestable with the automation (SQZ_FLT)
• Added the computation of the SQZ parametric gain in the automation

Clean up of usless channels and reduction of the data stream

• LFC_Ctrl: removed the channels saved at 100kHz for debugging, removed GR_11MHz channels, Removed GR transmission normalized by SHG transmission
• AFC_Ctrl: moved the set point of the GR actuators in the main config file, removed IR_BPC
• EQB1_HD_AA: rms date of HD_Diff_Audio  saved at 100 Hz instead 10 kHz
• FCIM_LC and FCEM_LC all channel downsampled from 10kHz to 500Hz
• SQB1_LC and SQB2_LC: PSD channels downsampled at from 10 kHz to two kHz and saved in the Dash Storage

In the process SQZ_DDS_Demod we added three flags,when they are equal to 0 the data ar not saved in the raw data, equal to 1 the data are saved in the raw data. These data remains always in the rds and in the trend data.

• IR_DATA_STATE: remove the data with the following prefix V1:EQB2_IR_* -V1:AFC_IR*
• GR_DATA_STATE: emove the data with the following prefix V1:EQB1_GR_QD* -V1:AFC_FC* -V1:AFC_GR_M*
• HD_DATA_STATE: remove the data with the following prefix V1:EQB1_HD

We can change the sttatus of these flag by changing in the SQZ_MAIN.ini file, section SAVE_DATA the following flags: 

• hd_save_data (False not save, True save)
• flt_ir_save_data (False not save, True save)
• flt_gr_save_data (False not save, True save)

During this process we also restarted AFC_Ctrl and EQB1_HD_AA that were not restarted on Tuesday. Now all QNR processes have the new ACL version

Switch off not needed hardware

• SQB2 pico: switched off with the FLT locked only on green. GR followed the transient. IR no probably we need to realign IR again on the FLT or re switch on the pico of SQB2 before working with IR and filter cavity
• SQB1 Pico: switched off at 21:00 UTC with ITF in LN3_SQZ in order to follow the transient that stopped at about 23:00 UTC
• With EQB1_PDU1 and PDU2 I could remotely switch off the following hardware below EQB1: the three Thorlabs HUBs with all the PZT Mirrors, The GR, LO and SC shutters, ApuSqueeze1 PC, and the USB hub below SQB1. Still on because on PDU3 and 4 not reacheble we have the delay line, the telescope, the HD filter and the PD for SC AA

To do this I commented in SQZ_FLT in DOWN the command to close SC shutter. Before switch off all I left the following config of shutters: GR open, SC closed, IR Open, LO Closed, HD filter IN

I also removed from requestable state in SQZ_FLT all the states with IR that needs the SC shutter Open

SQZ_MAIN changes:

I added a delay of 5 seconds between the opening of fast shutter in SQZ_INJECTING and when the CC loop is closed. In this 5 minutes we are computing the OPA parametric gain from the B1_4MHz_mag signal. We are saving this value in the variable SQZ_PARAM_GAIN from the process SQZ_PLL_AA.

We stopped at 21:00 UTC with the ITF in LN3_SQZ in science mode.

This entry is related to the shift of yesterday 13 March

Preparation to the shift:

In the morning Henning set the Mach Zehnder offset at 0.05V. With this the parametric gain increased from 2.7 to 3.03 i.e. the squeezing level generated by the OPA increased from 8.5 to 9.5 dB

After that we checked the clipping in the SQB1 FI and we found about 1% of clipping that was solved moving the RR by -60 steps in horizontal and +30 steps in vertical

We also checked the tuning of SQB1 HWP1 and HWP2 looking the beatnote between the LO and ITF beam on the HD detector and we mimized it. With a precision of 20 steps of the rotators

We measured the level of SQZ and ASQZ on the HD detector and we foundrespectively 5.8 dB and 9 dB. 

Shift:

The interferometer reached Low noise 3 at 13:51:33 and we measured only 1.9 mV of B1 4MHz mag. We expected to see something around 2.14mV  so we started to align.

We easily reached this walue using SQB1 pico and the AA loop. Then we tried to see if we could improve again by moving SQB1 Bench, the retroreflector and the Z direction of the matching telescope +/- 5000 for M33z and M34z.

Once we reached that state 2.12mV of B1_4MHz_mag we did not improve anymore. So we are probably on a local or on the global maximum. (fig1)

After the alignment we performed a CC phase scan:

• 15:39 Shot noise
• 15:48 Shot noise but we noticed an improvement of hrec
• 15:58 we started the scan (shot noise reference 2 min) 1394380724. The real scan started at 1394380849 (fig 2)
• We took 10 minutes of antisqueezing (phase 2.7 rad) at 16:39 and squeezing beetween 16:57 and 17:11  UTC (phase 1rad). (fig 3) 

From the phase scan we can see that we improved the range by about 3 Mpc starting from 51.7 Mpc. We worsened the range with Antisqueezing by about 4.7 Mpc

Tuning of the AA dithering loop

• We started to commissiong the AA dithering loop with M1_X, M1_Y, M2_X, M2_Y dither lines respectively at 20, 25, 30, 35, 40 Hz
• To do it we open the loop, we reset the correction and we start to scan each DOF with a ramp around the working point with 2 V of amplitude and frequency 0.2 Hz
• M1_X phase changed from 0.28 rad to 0.6 rad. Amplitude increased from 1mV to 10 mV
• M1_Y phase changed from 0.28 to 0.75 rad. Dither line ampolitude increased from 1mV to 3 mV
• M2_X phase changed from 0.36 to 0.8 rad. Dither line ampolitude increased from 1mV to 3 mV
• M2_Y phase changed from 0.3` to 0.75 rad. 

After this work the loop was more stable.

Injections and phase scan

• Squeezing injection at 19:16:50
• Shot noise at 19:33 with dither lines on
• Shot noise at 19:44 with dither lines off
• Shot noise at 19:57 with fdither lines on
•  Phase scan at 1394395672 in 1200 s

Fig 3 brms hrec during the on off of the dither line. No particular evidence except the fact that the noise was changing with the evoulution of the frequency noise.

In figure 4 you can see also that the range is increased from 50 to 54 MPc during the phase noise reference (the maximum was reached with dither lines on). 

Figure 5 shows also Hrec with dither lines on and off

Fig 6 you can see the effect of the squeezing in the pahse scan. Unfortunatelly we had a glitch during the maximum ASQZ and the minimum of the range. The SQZ injection increased again the range about 3.5 Mpc starting from 53.2 Mpc

After the scan Nicola left the system in LOW_NOISE_3_SQZ. I checked the stability of the system during the hour of injection. I saw a small degradation of the mag that seems be correlated to the improvement of CMRF. I don't know if it is due to some clipping created by the relative alignment between ITF and SQZ, in any case the range was increasing and the fluctuation was only 1% show it could be also due to a fluctuation of the Squeezer parametric gain

Here thr list of actions performed during the shift:

• The ITF Locked at 14:45 UTC and we took a shot noise reference with the shutter closed ~55 Mpc in the sensitivity
• At 15:20 we open the SQB1 shutter and we measure ~53 Mpc after 
• We work with alignment using SQB1 picomotors and the SQZ to  OMC AA closed we stopped the work at 17:28:50 UTC
• We close the Fast shutter (shot noise) at 17:29 UTC
• We injected SQZ (angle 1.3 rad) at 17:45:30 UTC
• At 17:52:30 UTC we open the AA and we removed the dither line
• We started moving the SQB1 position in particular SQB1 X from -2950 to -2750 um and SQB1 TX from 290 to 300 urad. At the end of the process we had a B1_4MHz_mag 2.03 mV. The initial magnitude was 1.95 mV i.e 4% of increase. The power increased of about 8%. (fig 1)
• We stopped with the clipping removal at 18:30 and we switched of the AA dither lines at 18:30.

Then we checked the CC loop:

• Clean data: 21:26 UTC 2 min (gain 75000 in SQZ phase 1.3 rad)
• Noise Injection 21:39 UTC 2 min with amplitude of 5uV. We measure an UGF og 4.1 kHz
• We saw lines in the CC loop at 3.088kHz and 6.129 kHz
• We open the CC at 21:46:09 UTC
• We close the shutter and we measure the sensing noise at 21:44 UTC
• The CC is limited by sensing noise and the SNR is about 200 (fig 2 and 3)

Then we checked the results of the alignment performing a CC phase scan:

• Shot Noise at 21:56 UTC
• Phase scan 1394230253 (fig 4)
• Phase scan shot 1394230253
• ASQZ 22:38:41 UTC
• SQZ 22:51:00 UTC (fig 5)

The goals of the shift were:

• to improve the alignment between SQZ and ITF removing clipping 
• tune the SDB1 FI HWP to reduce the amount of light sent from ITF to QNR
• measure the CC loop transfer function
• perform a CC phase scan

We left the ITF with SQZ injected in autorelock failsafe details will follow tomorrow

Check of the mismatch in CARM_NULL_1f

When the shift started the ITF was unlocked thus we started checking the matching in CARM_NULL_1F.

Once the ITF arrived in CARM_NULL_1f we open the DET Shutter, then I moved the OMC temperature at 22.617 C and I started to SCAN the SC frequency to see TEM00, TEM10 and TEM20. The Scan that I used is between 28200 and 27500 in 60 sec or in 5 sec. 

We measured the Matching with SR aligned and we found

@20: UTC TEM00 1.72e-3mW, TEM10: 0.281e-3 mW, TEM02: 0.336e-3 mW => 14.5% of mismatch

@20:41 UTC we misaligned the SR by +1.7urad in TY 

@20:55 UTC we measured again the matching and we obtained TEM00 0.912e-3mW,  TEM10 = 0.756 e-3 mW TEM20 = 0.337 e-3 mW about 17% of mismatch but a very high 17%.

LN2 SR alined and phase scan

We arrived in LN2 then we acquired the shot noise reference at 22:06 UTC. We saw that the 4MHz magnitude on B1 was only 0.5mV (in LOW_NOISE_3 usually is 2mV). 

We performed a phase scan of the CC loop: Shot: 1294143858, SCAN: 1394143983. With this scan the amount of losses is very high and we did not see the usual level of SQZ in the sensitivity of the past phase scans

Then we tried to find if some clippng is present and we started to move the alignment and SQB1 bench:

• SQB1 X from -2950 um to -2400 um
• SQB1 TX from 290 to 0 urad
• SQB1_TZ from 105 to 125 urad

After that we reached about 1.92mV of 4 MHz mag and we measured a parametric gain of 2.7 i.e. 8.6 dB of SQZ generated

• We performed again a phase scan: Shot 1394149579 (8min) and Scan: 1394149704
• Shot noise again at 00:10 UTC 
• ASQZ phase 2.48 rad at 00:21:30 UTC
• SQZ phase at 0.7 rad at 00:35:12 UTC
• Stop SQZ ath 00:45 UTC

Then we asked low noise 3 and we misaligned the SR. Now the magnitude was again 0.2mV so we had to reput SQB1 in its original positon except SQB1_TX that we left at 320 urad instead 290 urad.

The 4MHz mag was 1.9mV but during the process we saw it around at 2.05mV.

We saw that the sensitivity was spoiled by some peaks and we have the impression that some clipping caused some excess of stray light in the sensitivity and some instability of the 4 MHz mag on B1. 

We closed the SQB1 shutter and in a couple of hours the sensitivity improves by ~2-3 Mpc. To be ckecked.

The goal of the shift was:

1) Measure the mode matching with SR aligned and Misaligned and hot ITF. In both the cases 15% of mismatch 

2) Measure the losses in LN2 with SR aligned: about 50% of losses

3) Receck of the system in LN3 and SR misaligned

All the details will follow

We left the ITF in LN3 and the SQB1 shutter closed

The attached plot compares the Hrec sensitivity with (purple) and without (blue) squeezing injected, the main difference is below 250 Hz, as expected from the extra losses above the DCP frequency due to SR misalignment.

The shift was dedicated at the study of the effect of SQZ injection to the range in different SR confiurations

The shift started after the ITF Lock recovery. Relock in LN2 at 17:59 UTC.

• Once in LN2 I tried to do a Phase scan of the CC loop with SR aligned. I relized that the CC mag was about 0.7mV i.e. 1/3 of the maximum mag of the previous shift
• I asked LN3 and I saw that during the transient the magniutude increased again see fig 1.
• In LN3 I tried to improve the matching in ASQZ with SQZ Injected looking magnitude and I mooved M34 by 7000 steps forward and M33 by 3000 steos forward. See fig 2
• At 19:10:34 I injected SQZ with CC gain at 75000
• At 19:16:20 I switched off the AA and the dither lines
• At 19:58 I removed the SQZ and I acquired shot noise see fig 3 for the spectra. The gain of SQZ injection is very tiny between 70 and 120 Hz
• At 20:15 SQZ is injected again with AA off
• At 20:36 SQZ removed. In fig 4 you see the effect of the squeezing on off. A couple of Mpc should be gained by the SQZ injection. We touched 59.5 Mpc
• After that I performed a CC phase scan at 1393879698 for the shot and 1393879823 for the scan
• At 21:20:40 I moved the SR TY moving the set point of DCP from 170 to 190 with a 150s ramp. The SR arrived at 21:36 UTC during the transient the SQZ was on with AA on
• At 21 36 SR arrived and at 21:37 I acquired a shot noise reference
• I performed a CC scan also in this configuration shot at 1393883180 and scan at 1393883310
• At 22:38:33 I moved again SR changing the DCP set point from 190 to 180 with a ramp of 150s with SQZ on and AA engaged
• At 22:47 and 20 the SR arrived
• At 22:48:15 Shot noise reference started
• New phase scan at 1393887428 shot and 1693887553

Results of phase scan:

Fig 5 DCP @ 170Hz: 

We leave the system with SQZ engaged (LN3_SQZ) and DCP at 180 Hz

The night between 06 and 07 March 2024 we injected Squeezing. Some observation.

Figure 1: the suqeezing phase was left at 1.3 rad without slow CC. The level of the B1_4MHz_mag was stable during all the lock and also the hrec BRMS at 100 and 300 Hz were stable. The SQZ AA actuators moved a lot during the night probably to follow SDB1 bench and the SR alignment

Figure2: at the end of the night the Fiodor and Nicola performed a phase scan of the CC and this confirmed that the SQZ phase was still optimal 

Moreover the injection was stable and without unlocks of the squeezer. Thus the injection was succsesful without any major problem

We changed the logic of SQZ_MAIN and SQZ_FLT for the run. In particular:

• SQZ_FLT relocks the cavity only on GR and is no more managed by SQZ_MAIN
• In SQZ_MAIN all the states that manange the filter cavity are no more requestable
• In SQZ_MAIN the states for the injection of FIS back reflected from the filter cavity or FDS are called SQZ_INJECTING_FC, SQZ_LOCKING_FC, SQZ_LOCKED_FC,  and SQZ_INJECTED _FC these states are not requestable
• In SQZ_MAIN the states for injection of FIS from retroreflector (no filter cavity) are added and are requestable. SQZ_LOCKING_NO_FC, SQZ_LOCKED_NO_FC, SQZ_INJECTING_NO_FC, SQZ_INJECTED_NO_FC. These two states are connected to the state LOCKED_PLL_SC
• In SQZ_MAIN the flags fis_injection and sqz_flt are added in the group AUTOMATION_NODES
• In SQZ_FLT the flag itf_fis_rr is added in the group Options

Moving the flags you can obtain different working modes:

• sqz_flt on SQZ_MAIN if false you esclude the filter cavity
• fis_injection in SQZ_MAIN: when sqz_flt is True you can decide to do FIS injection or FDS injection. If you want perform FDS injection please put itf_fis_rr equal to false
• itf_fis_rr: is in SQZ_FLT you should put this flag equal to True when you want to lock directly the FC with only green (no IR) and excluding the lock on the laser 

Configuration for the run O4 (first line of the table)

• In DOWN the squeezer is unlocked and the fast shutter closed. 
• PLL_SC_LOCKED is the ground state for the FIS_INJECTION: Squeezer unlocked, Fast shutter closed, all the loops are open
• SQZ_LOCKED_NO_FC: squeezer locked,  Fast shutter closed, all the loops are open
• SQZ_INJECTED_NO_FC:  squeezer locked,  Fast shutter open, all the loops are closed FIS injected into the ITF

If you want run a phase scan of the CC you should go in SQZ_LOCKED_NO_FC

In addition we changed the decorator INJ_UP now we don't look anymore the RFC but only the state of INJ_MAIN

The aim of the shift is to estimate and possibly improve the MM of the squeezed beam to the OMC. To do this, we used the SC beam, which is 99.1% mode matched with the OPO. The SC beam has a frequency offset of 1262 MHz with respect the interferometer beam, thus its TEM00 mode falls in the middle of the OMC Free Spectral range when it is locked on the interferometer beam. Thus to measure the matching we locked the interferometer in CARM_NULL_1F, we open the OMC slow shutter, we changed the OMC temperature in order to move its resonance frequency by about 400MHz. Then we sent the SC toward the ITF and we started to increase Scan the SC laser temperature acting on the SC Laser temperature controller by at least 800MHz i.e. one OMC FSR. The matching between SC and OMC was measured using the B1 PDs, in particular B1_PD3. We performed all the shift with  B1 PD1 and PD2 shutters closed.

More details on the shift  procedure are available here.  

The shift started at about 17:00 UTC as soon as the lock of the interferometer was recovered by the ISC crew.

Preparation and alignment between SQZ beam and ITF

• 17:13 UTC ITF in LN2 
• 17:31:45 UTC start opening the SDB1 shutter (at the end -300000 steps )
• 17:38-17:40 UTC rotated  the SQB1 FI-HWP to send the SQZ beam to ITF stop 
• 17:42  UTC SQZ MAIN in SQZ_INJECTED (this implies that the auto alignment loop is activated)
• 17:45  UTC antisqueezing 2.45 deg
• Others -60000 steps on the SQB1 shutter 
• 17:50 UTC the magnitude of the 4MHz beat note is  about 1.36 mV which is 20-25% lower than usual. Therefore we tried to move the SQB1 bench in X position. However, the best position seems to be the initial one. We then return to the initial position (-3150um).
• 17:57-18:00 to try to recover magnitude we move the M33 H and V picomotors. However, a significant increase in magnitude is not observed.

A possible explanation of this reduction of the magnictude is the fact that on wendesday the matching between ITF and OMC was adjusted and this caused a mismatch between SQZ and OMC

Preparation for MM estimation

• 18:03 UTC we unlocked the ITF and we requested CARM_NULL_1f 
• 18:15 UTC CARM_NULL_1F achieved
• We set the DARM offset at  -0.2 with a ramp of 120s in order to be able to see on B1 CAM and B1_PD3 the ITF TEM00 mode changing the OMC temperature and use this value as a reference for the OMC temperature shift.
• 18:27 UTC OMC slow shutter opened  (ITF_LOCK in SHUTTER_OPEN)
• 18:32 UTC modified  the OMC temperature from 22.4923 C  to 22.5138 C. In this condition the ITF TEM00 is visible. 
• 18:34 UTC OMC temperature moved in steps of 0.02 C.   Target value 22.6188 C (i.e. 5 steps)
• 18:53 UTC in the mean time that the OMC  termalizze (last step) we open the squeezer fast shutter and SC shutter. The SC laser peltier at  30600. From now the SC PLL should be unlocked thus we set the automation SQZ_MAIN in LOCKED_CC_PLL. We also checked that the OPA was locked
• At the end we reduced the DARM offset by a factor 10 i.e. -0.02 in order to mimic the DARM offset that we have when the ITF is in LOW_NOISE_3

SC frequency Scan

• 18:55 UTC First SC scan: laser petier range 30400-30880 ramp time  60 seconds. Peltier rang too small, not visible the SC TEM00 mode 
• 19:01 UTC new ramp 30200-31000. Several peaks at PD3 are observed and one of that was the TEM00
• Now we stopped to perform ramps on SC PLL temperature and we performed temperature steps by 50 bits of the PLL SLOW DAC in order to see mode bu mode
  • peltier 30942, TEM00 , PD3 peak 0.0012 mW (to be multiplied by 4800 fo absolute calibration)
  • peltier 30705, LG01, PD3 peak 0.00057 mW
  • peltier 30463, PD3 peak 0.00036 mW (see fig1)
  • Peltier 30225, PD3 peak 0.00021 mW (see fig 2)
  • Peltier 29982, PD3 peak 0.00005 mW (see Fig 3)
  • Peltier 28182, TEM00 (see Fig 4)
  • Peltier 27930, LG01, PD3 peak 0.00054 mW (see Fig 5)
  • Considering that the distance between 2 TEM00 is 2800 bits, the distance between two LG01 is 2775 and the FSR of the OMC is 813 MHz, each bit of the PLL slow DAC is 0.29MHz
• 19:45 UTC SC sidebands OFF and ON again
• 19:53 UTC  scan of TE00 mode,  28100-28300. Ramp 10 sec.
• During the scan we move pico mothors M33H and M33V in order to maximize the TEM00 peak amplitude on PD3
• 20:15 UTC, after the realignment we tried to open the B1 PD1 shutter. Right after the interferometer unlocked due to excess power on the PD1 photodiode, i.e. the Power of the SC on B1 PD1 was higher than 6 mW. We subsequently realized that we underestimated the amplitude of the peaks in PD3 by about 20-30%. We decide to continue with PD3 only.
• 20:43  UTC we reached the same configuration as before the unlock.
• 20:45 UTC  first SC scan after unlock  peltier scan 28300-28000 10 sec detected on PD3
• 20:49:08 UTC long peltier scan  27000-32000 scanning time 600 sec (i.e. ramp up 300 sec and ramp down 300 sec.). In figure 6 we higlited the misalignment mode HG10 and the mismatch mode LG01. With a rough estimation the Misalignment is in the order of 10% and the Mismatch was about  30%
• 20:13 UTC Fast ramp around the 3 peaks (TEM00, LG01, TEM01) 28300-27600 in 60 sec
• 21:18UTC during the scan we moved M33Z and M34Z to check if we can improve the MM lowering the peak amplitudes  of high order modes with respect   to TEM00. Unfortunately we don't get much improvement. It will be necessary to make a dedicated shift for this purpose
• 22:03 UTC same scan but in 10 sec instead 60 sec. We tried to align and match but at the end the situation was also worse (Fig 7)
• 22:20 UTC Restored the initial condition of the OMC. The acquisition of the LN3 condition is started.
• 22:39 UTC SQB1 shutter closed +510000 steps
• 22:42 UTC SQZ_MAIN automation in “READY_FOR_FIS_INJECTION” and the SQB1 FI HWP is rotated to send the light  toward EQB1

It is aready happened 2 ices that with the BAB and the SQB1 shutter closed we spoiled the sensitivity of the ITF.

As further protection I changed the frequency offset of the SQZ main Laser when the automation is in READY_FOR FIS_INJECTION and I restored it in the state DOWN and SQZ_LOCKING (this state could be accessed only if the ITF is at least in LN2 and in this sate the Fast Shutter is closed)

The standard DAC offset configuration is 0.285 V, whereas in DOWN we put 2.285 V. With this change the beat note between ITF mean Beam and the laser should be above 10 kHz. I don't know if this it is enough to prevent all the effect on the sensitivity. This should be tested.

The switch between 2.285V to 0.285V is performed with a ramp of 5s.

The switch between 0.285V to 2.285V in DOWN is performed only if the system is in BAB mode. 

I could not implement the change only in DOWN because I found problem in the FLT locking with the double loop so I had to go back and forth two ice.

I followed the usal procedure to align the MZ and the OPA ( https://logbook.virgo-gw.eu/virgo/?r=56246)

N.B: No walk off was done on the OPA steering to minimize the 01 and thus to improve the alignment. I just mazimized the ratio betweem 00 and 01 by checking the position of the tilting screws on the last steering before the OPA as done inthe past. And check that correspond to the maximum with the upper screw of the previous steering. In this way was not possible really improve the alignment, that require a little bit of walk of between the steering (to plan, if really needed)

During the last shift with ITF we performed a phase scan of the CC loop measuring SQZ with EQB1 HD detector with the SQB1_Shutter Open. We fitted the data and we find a very good efficiency but about 100 mrad if phase noise (fig1).

Today we decided to repeat the measurement in 4 different configuration:

1. RR oin SQB1 and SQB1 shutter open
2. RR on SQB1 and SQB1 shutter closed
3. RR on SQB1, SQB1 shutter closed, all dither lines in SQZ path off
4. Same of point 3 but better alignment of HD
5. Delay line on EQB1 and all dither lines in SQZ path off.

We found a huge difference in the HD shot noise spectra with shutter open and SQB1 shutter closed (fig2)

When we were moving the shutter we saw also some lines appearing in the Shot noise spectrum (fig 3)

Here the GPS time of all the events:

Config 1 -  RR oin SQB1 and SQB1 shutter open (fig 4)

CC open @12:40 UTC max mag 7.86mV min mag 3.1mV parametric gain 2.535 SQZ generated 8.079dB
ASQZ measured: 7.7 at 0.77 rad
SQZ measured : 5.25 @ 2.25rad
Config Standard Shot @ 12:58
Scan at 13:06:15 UTC from 0 to 3.14 in 1000s
Shot noise again 13:23:11 UTC

Closing shutter at 13:26:25 13:44 UTC with 1.4 million of steps

Config 2 -  RR oin SQB1 and SQB1 shutter closed (fig 5)

Shot noise at 13:45UTC 2 min
Parametric gain measured at 13:48 UTC max 8.03mV min mag 3.08 mV i.e 2.6 parametric gain 8.3 dB of SQZ generated
SQZ level 5.55 at 2.25 rad
ASQZ level7.85 at 0.83 rad
Phase scan at 13:59:23 UTC from 0 to 3.14 in 1000s unlocked
Phase scan at 14:07:59 UTC from 0 to 3.14 in 1000s unlocked
Phase scan at 14:16:15 UTC from 0 to 3.14 in 1000s
Shot noise 14:37:21

Config 3 -  RR on SQB1, SQB1 shutter closed, all dither lines in SQZ path off (fig 6)

Switched off HD M6 lines x 0.002V y 0.0015V
Switched off SQZ_CTRL 2800 Hz dither
New scan at 14:51:38 UTC from 0 to 3.14 in 1000s

Config 4 - Same of point 3 but better alignment of HD (fig 7)

Alignment after measurement phase scan 15:33:47 from 0 to 3.14 in 1000s
 

Config 5 -  Delay line on EQB1 and all dither lines in SQZ path off (fig 8)

With DL SQZ 6.1 dB with 2.2 rad
ASQZ 8dB 0.8rad
Phase Scan 16:19:43
Shot noise 16:37:30
SQZ @2.21rad 16:48:09 UTC CC Coarse Open 6.05 dB
16:50:16 UTC CC coarse on

Note that we still need to cross check the fit formula in particular the phase noise value. it seems too high for us. 

At the end we rotated back the  SQB1 HWP2 to send SQZ beam towar ITF 17:07 UTC

At 23:35 I started a phase scan in LOW_NOISE_3 with SR misaligned.

At the end of the phase scan I left the system in SQZ_INJECTED, LN3 with ITF_STATUS in DQ_STUDIES (00:09UTC)

The planned shift with ITF could not start as planned at 15:30, thus we exploited the time to check the SQZ level with the HD Detector and the retroreflector of SQB1

We measured a parametric gain of 2.77 i.e. 8.85dB of generated SQZ. We measured 8.6 dB of ASQZ and 5.85 dB of SQZ

We performed a phase CC phase scan betweeon 0 and 3.14 rad starting at 17:18:24. We took the shot noise reference at 17:49:00 UTC.

As you can see in fig 1 the normalized channel for is 0.05dB during shot noise, i.e. the true level of ASQZ is 8.55dB and of SQZ is 5.9dB.