ITF found in COMMISSIONING Mode and LOCKING_ARMS_BEAT_DRMI_1F State.
All times are UTC.
At the beginning of the shift the activity on DC read-out locking was ongoing and wnet on up to 20:01 (Mantovani, Bersanetti, Spinicelli, Gouaty, #69857, #69856).
19:57 ITF reached LOCKED_DC_READOUT state.
20:07 - 20:59 Test lock acquisition to LOW_NOISE_2 state, power increased when ITF reached CARM_NULL_1F state, ITF unlocked in ACQUIRE_LOW_NOISE_1 state at 20:59:38. As instructed by the experts after the unlock I manually set INJ power to 12 W and re-initated INJ_MAIN Metatron node.
ITF left in COMMISSIONING Mode and LOCKED_ARMS_IR State.

Guard tours:
17:57, 20:31

At the end of the shift we performed a lock attempt up to LN2. We managed to reach DC readout but then the ITF shortly unlocked (see attached figure).

During this trial, the OMC did not manage to lock at first attempt, because the B1x_DC_DARM_norm_prod signal was not reaching the lock threshold set at 2000. We decreased this threshold to 1500 (done at 20h54 utc) and then the OMC locked successfully.

During the afternoon shift, we updated DET_MAIN.py in order to use the MOVELIMIT command to close or open the OMC. DET_MAIN node was reloaded at 14h05 utc. Unfortunately after this change the OMC shutter was not opening any more. I also tried to open it directly from the VPM intervace with the MOVELIMIT command (in both directions), but the shutter was not opening. I therefore open manually the shutter using the old command. Changes reverted in DET_MAIN.py.

DET_MAIN reloaded at 15h17 utc.

After Romain has locked we tried to make the hand-off to B1 PD3

we have measured the TF DARM_INPUT/B1_DC_INPUT  which was equal to 0.017 (it was 0.0027); the B1_SET was 0.0 

then we increased the offset to get the good powers on PD1 and PD2. the final offset is -7.8

the Hand-off worked without changing the DARM gain (the line 5196 will be left commented as the 5365).

After the TCS step, we proceeded with the recovery of the OMC lock and of the DC readout.

After setting metatron in OMC_SCAN and reducing the DIFFp lines to decrease the overall rms on B1_PD3, we allowed the DET crew to attempt the OMC lock, which was successful.

Trying the hand-off of DARM to B1_DC failed, possibly due to low gain. The hand-off is commented in the automation (lines 5196, 5197), including the population of the relative sensing matrix element (lines 5181, 5182, 5183) in order to manually re-try the hand-off after re-measuring the calibration factor of the new error signal.

This was left for the afternoon to try after the daily meeting.

ITF found in LOCKED_ARMS_IR in COMMISSIONING mode.
Relocked up to CARM_NULL_1F after the usual cross-alignment in ACQUIRE_DRMI at third attempt.

The planned activity on DC read-out locking (Boldrini, Was) started at 07:00 UTC. Still in progress... 

On Friday, a pure differential change was applied (69846), with the goal of changing the ETM RoCs by ±2 m:

RoC_NE: 1669.6 m → 1667.6 m [9.82 W (19.1 V)]
RoC_WE: 1670.5 m → 1672.5 m [9.00 W (18.3 V)]

During the weekend, Michal suggested acting only on the WE RH, decreasing its RoC by 1.5 m in case the dark fringe was bright during the next lock:

RoC_WE: 1672.5 m [9.00 W (18.3 V)] → 1671.0 m [9.6 W (18.9 V)]

During this morning's CARM NULL lock, the dark fringe was quite bright, at around 0.04 mW. Therefore, at 07:23 UTC, the WE RH power was increased to 9.6 W (18.9 V), corresponding to a target RoC of about 1671.0 m.
The effect was as expected, with a reduction in both B1p power and the SSFS-to-DARM coupling (fig.1). 
During the work on the OMC, at 09:13 UTC, the ITF unlocked, and we took the opportunity to follow up on the 10% common DAS increase performed on Friday (69844) by increasing the CH powers by 10% (ITF in CITF).
Thus, now the power injected into the ITF are:

As expected, the local damper of PR mirror vertical mode at 11.6 Hz is noise enough to keep the resonance permanently excited. Turning it off, the resonance disappear from PRCL spectrum. Apparently the locking instability at 11.6 Hz is not there when the ITF is well tuned and PRCL is clean enough. We can try a lock acquisition without the damper, or eventually continue using it up to a certain locking step.  

The following report has been submitted to the On-call interface.

On-call events -> Air Conditioning

Title: Chiamata per regolazione parametri impianto HVAC mensa

Author(s): Pezzimenti Francesco

Details:

Sono stato chiamato Da Soldani per effettuare delle regolazioni all'impianto HVAC della mensa, per l'evento di stasera.. Le regolazioni sono state effettuate in loco, confrontandomi telefonicamente con i tecnici del reparto di riferimento..

* Note that any files attached to this report are available in the On-call interface.

We supported the TCS team during the thermal actuators' adjustments.

After the common RH step and the differential DAS step, we noticed that the ITF was jumping between two metastable states (Fig.1). The ~3 minutes period of these jumps made us think of a correlation with the diagonalizaton routine. We waited for the ITF to jump in the "good" state, the one with the darker fringe and the higher sidebands' power, and disabled the servo to verify the hipothesis. The jumps stopped, giving comfirmation that diagonalization was indeed driving them, but it is unclear what exactly the servo was chasing when it made these changes.

After the common step of RH the interferometer's tuning gradually improved (Fig.2), although the superposition of the thermal transients of the first RH step, the DAS step and of this last RH step makes it complicated to pinpoint the exact cause of this improvement.

During this transient the ITF unlocked due to a WI glitch (Fig.3) and we reduced the power manually to allow the INJ_MAIN node to recover the IMC. This was harder than yesterday: between the movement of the half-lambda plate and the alignment of the bench, the reflected power of the IMC is close to the critical value (0.68 W - 0.79 W, Fig.4) and we had to increase the transmitted power a little to clear this threshold. The INJ servo then adjusted the rotator setpoint without issues.

After the next lock we increased the power again to keep observing the thermal transient, but the lock was killed 15 minutes after the acquisition by another WI glitch (Fig.5)

We have began the development of the power increase automation in carm_null_1f, for the moment offline, to be deployed later. For the moment, ITF_LOCK.py is unmodified and executes as usual.

We leave the ITF with the arms locked.

At the end of the activity  today we moved the etalon loops setpoints up one full fringe, with a ramp of two days:

• NI = 20.207 -> 20.464 degC;
• WI = 19.6 -> 19.857 degC.

As stated at the daily meeting, the automation would have received some modifications during the afternoon. and the actual deployment would have been decided by the people in shift onsite at the end of the activity.

Despite that, and despite the fact that ITF_LOCK doesn't need a reload when the .ini file gets modified, this happened, from offsite, without any communication to the control room and the people in shift. Luckily, most of my changes were not saved yet, but this is not the way to go.

All changes have been reverted, and any kind of development has been aborted for the day, on purpose.

At around 14.00 UTC, some jumps started to appear in the main ITF signals (see fig.1). Assuming that the jumps could be related to some higher-order mode, Michal suggested to change the ETM RH settings to move the cavity away from this critical region. 

Before starting the tuning of the ETM RHs, the configuration was:

NE: V = 18.3 V (9.02 W)
RoC_NE = 1669.6 m

WE: V = 19.1 V (9.80 W)
RoC_WE = 1670.5 m

A pure differential change was therefore applied, with the goal of changing the RoCs by:

RoC_NE: -2 m
RoC_WE: +2 m

At 15:09 UTC, the RH settings were changed to:

NE: 9.02 W (18.3 V) → 9.82 W (19.1 V)

WE: 9.00 W (18.3 V)

Later, Piernicola and Mattia realized that the jumps were actually related to the diagonalization. After disabling it, the jumps disappeared).

At 16:25 UTC, the ITF unlocked due to a glitch.

From this point onward, the ISC team worked on the lock acquisition automation.

The effect of the step will need to be evaluated during the next locks.

This afternoon we have updated the following thresholds on the detection system, in accordance with the increase of the input power from 12 to 18 W:

• we updated the thresholds on SDB2_Photodiodes triggering the fast shutter for B1p_PD1 and B1p_PD2 (B1s was already changed yesterday). All thresholds multiplied by a factor 3/2 in the configuration:

ACL_RELAY_CH    B1p_PD1_DC_saturation        au    SAMP_FREQ    0    2    -2    B1p_PD1_DC    0.82 0.58 >=   #0.55 0.39 #0.82 0.58 #1.65 1.166 #3.4    2.4  #2 0.7
ACL_RELAY_CH    B1p_PD2_DC_saturation        au    SAMP_FREQ    0    2    -2    B1p_PD2_DC    1.17 0.29    >= #0.78 0.19 #1.17 0.29 #2.35 0.588 #4 1
ACL_RELAY_CH    B1s_PD1_DC_saturation        au    SAMP_FREQ    0    2    -2    B1s_PD1_DC    45    22    >=   #30 #45    22 #35 20 #45 22 #90    45 #43 12

• Thresholds in ITF_LOCK.ini for B1p_PD1 have been increased accordingly:
  • in the section SHUTTER: b1p_pd1_thr_lo = 0.3 ; b1p_pd1_thr_hi = 0.5 ; b1p_dc_thr = 0.04
  • in the section ITF_LOCK: b1p_pd1_thr_lo = 1.5 ; b1p_pd1_thr_hi = 3.0

We used the external configuration of SDB2_Photodiodes in order to apply the new threshold on B1p_PD1 (3.0 instead of 2.5) while the ITF was locked in CARM_NULL_1F.

• Thresholds in DET_MAIN.ini have also been increased by the same factor, namely:

max_power_B1p = 0.04, max_power_B1p_PD1 = 0.44, max_power_B1s = 45 (unchanged with respect to yesterday)

Both DET_MAIN and ITF_LOCK were reloaded at 16h34 utc after an ITF unlock.

First, we implemented the lock acquisition procedure performed yesterday evening: it worked reliably again this morning.

At 07:23 UTC, Manuel gradually increased the injected power up to 17.5 W (INJ_IMC_TRA_DC) in CARM_NULL_1F. The ITF unlocked at 07:53 UTC due to a suspension glitch similar to previous events.

We reacquired CARM_NULL_1F at around 08:11 UTC with an injected power of 17.7 W, closer to the nominal 18 W. The ITF unlocked at 08:27 UTC, as MICH and DARM drifted away without a clear trigger.

Finally, at 08:43 UTC, CARM_NULL_1F was acquired again at 17.8 W of injected power.

At this point, we started the thermal tuning; the initial configuration is reported in 69838.

The plan is to explore the effect of the WI DAS IN power and to perform a differential step. We agreed to double the NI DAS IN injected power and evaluate its effect on the ITF.

08:56 UTC STEP 1
WI DAS IN +100%

The SBs responded quite rapidly going down and the dark fringe worsened, indicating that increasing the WI DAS IN power is not the correct direction. So we agreed to close the flip mirror of the WI INner DAS.

09:38 UTC STEP 2
WI DAS IN set to 0 (flip mirror closed)

See Fig. 1 for ITF signals corresponding to these two steps.


Since the DAS differential steps did not seem to have a significant impact, Michal suggested performing a differential ETM RH step. In particular, we decreased the WE RoC by acting on the RH, as the strong PA on the WI is expected to induce additional curvature

10.31 UTC STEP 3
WE RH RoC reduced by 4 m, that is V = 19.1 V → 20.6 V and P = 9.8 W → 11.4 W

This last step rapidly increased the dark fringe brightness (see Fig. 2), so the step was reversed and then continued in the opposite direction of the same amount.

11.03 UTC STEP 4
WE RH RoC increased by 8 m, that is V = 20.6 V → 17.5 V and P = 11.4 W → 8.2 W

The effect of the last step of WE RH seemed good: B1p decreased up to 0.02 mW (around 12.40 UTC), before restarting to rise up (see fig 3).

13:29 UTC STEP 5
NI DAS IN and OUT +10%
WI DAS OUT +10%

The effect of this last step is ongoing.

The configuration of the CO2 actuators, so far, is summarized in the table below:

ITF found in LOCKED_ARMS_IR in COMMISSIONING mode.
At 06:00 UTC I locked ITF up to CARM_NULL_1F at first attempt.

Then the planed activity on "TCS tuning / CARM NULL locking (Pinto, Corubolo, Lumaca)" started. Still in progress...

Following the increase in input beam power, I repeated the analysis of the PAs on the ITMs.

Figures 1 and 2 show the NI maps, while Figures 3 and 4 show the WI maps.

The new analysis confirms the PAs identified in #69827 for both mirrors. The higher input power also allows for a slightly more precise estimation of their thermal signatures compared to the previous analysis.

For the NI, the high-temperature region observed at the center of the mirror appears to have a smaller impact in terms of ΔT with a value below 0.2 °C compared to approximately 0.3 °C in the previous analysis. The stronger PAs, instead, are consistent with the previous analysis in both position and estimated ΔT.

For the WI, the results are overall consistent with the analysis performed at lower input power. The estimated ΔT values of the two main PAs are slightly higher, at approximately 0.9 °C and 0.46 °C for PA1 and PA2, respectively. In addition, at least four other weaker PAs can be identified, with estimated ΔT values of around 0.2 °C, consistent with the features already observed in the previous analysis.

Fig 1 shows that NI and WI inertial control of IP are going through a bad time. The shown period is just the lates 5 days, but the situation has been like this for a long time. This situation is happening more and more often in general indifference, although it is quite simple to spot: the IP rotational dof is quite insensitive to external actions, so a sudden excess motion (up to 100 times more the normal rms) is almost for sure due to a control problem. The direct reason is known: a fast glitch on the accelerometers; a deeper explanation and a permanent solution has never been proposed.

I made a fast quantification of the impact of this situation on locking stability. In the latest 5 days one can count 34 lock losses from locking index larger than 45 (lock acquisition started). Among them, 7 are due to  NI glitches; 3 are due to WI glitches: 30% of the total unlocks. Fig 2 and fig 3 show the dynamic of the unlocks: the rotational event is obviously associated to a large longitudinal motion, which lead the locking correction to saturation. To be noticed that the large IP rotation is never due to the unlock: if NI moves, ITF unlocks and no effect is visible on WI. Viceversa, in WI type unlocks, NI remains quiet.  

Today, we performed two DAS steps to induce differential RoC variations between the ITMs. Specifically, the DAS powers were adjusted to produce an estimated RoC change of +1.5 m on one ITM and -1.5 m on the other, and vice versa.

The initial configuration of the CO2 actuators remains identical to yesterday evening's and is detailed in the table below:

When we arrived in the Control Room, the ITF had been locked at CARM_NULL_1F since 06:50 UTC. Manuel adjusted the alignment around 07:15 UTC, after which we proceeded with the DAS steps as follows:

07:45 UTC STEP 5
NI DAS IN and OUT -4%
WI DAS OUT +4% (DAS IN OFF) 

Just after this step, Manuel adjusted the lines in 69835.

12:16 UTC STEP 6
NI DAS IN and OUT +8%
WI DAS OUT -8%

Before the Daily Meeting, as about an hour was still available, Paolo proposed re-exploring the effect of the beam position on the ITMs via PR alignment. Paolo, Manuel, and Piernicola used the remaining time for this test (a dedicated log entry will follow). We intentionally chose not to restore the TCS settings immediately, as the system was still reasonably close to optimal conditions and another TCS change would have triggered a long thermal transient. 

None of the RoC differential steps yielded significant positive effects (see Fig. 1), so we agreed to restore the initial configuration of the CO2 actuators, but we performed the step just after a test on the SHUTTER_OPEN had been performed (see ISC entry for details, 69839).

14:06 UTC STEP 7 (equivalent to the resulting configuration after the STEP 4).
NI DAS IN and OUT -4%
WI DAS OUT +4%

At 14.10 UTC, the ITF unlocked due to a glitch on one of the ETMs. The CARM_NULL_1F state was acquired again at 14:42 UTC.


Between 15:25 UTC and 15:40 UTC, we began increasing the injected power in the following steps: 11.2 W → 12.6 W → 16.05 W (a total variation of approximately 4.85 W).

Since the power variation was larger than intended, the stability of the lock rapidly degraded, requiring prompt adjustment of the CO2 compensation.

We roughly estimated the power variation in the arms to be approximately +37% and performed a common DAS step of the same magnitude; furthermore, we opened the WI DAS IN flip mirror (at the minimum power value).

15:55 UTC STEP 8
NI DAS IN and OUT +37%
WI DAS OUT +37%
WI DAS IN open at minimum power

The compensation was good enough in CITF, and the SB levels were high enough to attempt going further. We therefore proceeded with the lock acquisition as reported in the ISC entry (69839) and managed to recover CARM_NULL_1F at the higher injected power around 18:45 UTC.

The final TCS power configuration is reported in the following table:

In order to support the TCS tuning of DAS for the final injection power of 18 W we changed online the transmission of the IMC from 11 W to 18 W while keeping a lock in CARM_NULL_1F.

The commands used are:

• to increase the input power:
  • cm_send('EIBAgilisRot', 'MOVEREL', 1, 1, -2000, 50)
• to decrease the input power:
  • cm_send('EIBAgilisRot', 'MOVEREL', 1, 1, 2000, 50)
     

Where the '2000' is the step size not a setpoint. Note that the steps have some hysteresis, and coming back usually requires more step than going up in power.

Overall the DAS tuning is positive, with a well tuned common component that grants adequate sideband power but a less than optimal differential tuning that leaves a bright fringe of ~0.035 mW, against the 0.011 mW observed during O4.

The process of changing the power midlock was surprisingly easy, which gave us the idea of attempting a lock acquisition at low power. After tuning the CH to compensate for the new setpoint of the DAS, and increase again the power at CARM_NULL_1F, we modified the automation to close the flip mirrors of the CH at CARM_NULL_1F (before was at carm step 2/3), re-engaged the final working point with 11 W and then increased the power in steps to 17.3 W, starting when the flip mirrors close to roughly replace the CH with the YAG at the same time.

Against all expecations this worked very well, with the very appreciated advantage of avoiding the recovery of the whole lock acquisition and to ease the further TCS tuning.

This procedure can be stably adopted and be automated at least for the interferometer tuning phase. 

Tomorrow this process will be automated, substituting the manual steps of the rotator on SIB1 with a servo loop.

We leave the ITF with arms locked, after restoring the transmission of the IMC to 11 W.

The origin of the uncorrelated trend observed yesterday in the arm cavity powers has been found to be the consequence of the input power trend.

The figure 1 shows the comparison of B8 DC and the PSTAB_power * a + o, showing a good superposition (for B8>300mW).

We increased the B1s threshold triggering the fast shutter to 45 mW, which is slithgly below the safety threshold of the phododiode (~50 mW).

The change was applied to DET_MAIN.ini and to SDB2_Photodiodes. The external configuration of SDB2_Photodiodes was reloaded at 15h16m18-UTC.

ITF found in COMMISSIONING Mode and LOCKED_ARMS_IR State.
All times are UTC.
06:52 ITF in CARM_NULL_1F.
07:00 Begin of TCS tuning / CARM NULL locking activity (Pinto, Corubolo, Lumaca).
07:13 NI Y offset added (Pinto).
13:59 SDB1 slow shutter has been open.

ITF left in COMMISSIONING Mode and SHUTTER_OPEN State.
 

These modulation are caused by the high amplitude of the DIFFp tx and ty lines used for the UGF servos. The choice of these amplitudes is due to the 'necessity' seen in the past of surviving the initial transient of CARM null in which diffp gains change a lot. Reducing of a factor 2 the amplitudes improves the fluctations on the fringe, keeping enough coherence for the servos, fig.1.

We can simply decide to reduce the amplitude in the automation once we reach the steady state (or checking if we still need such high values of the lines amplitude in the initial transient).