I spent friday afternoon/evening to implement lower blending in the pid for the vertical d.o.f. of the external injection bench.
We blend the LVDTs with the geophones on the bench, and also with the ground geophones. The LVDT measure between bench and ground and we subtract ground noise (LVDT_y is the LVDT signal, LVDT_yb contains added ground monitoring geophone, and GEO_y is the geophones on the bench, etc). The geophones and LVDTs are then blended with an (s+s0)^5 filter. For the horizontal LVDTs, which still show normal noise so below 1 nm/sqrt(Hz) above 3 Hz, we blend at s0 =6 (almost 1Hz), since blending at the resonances of the bench is problematic. For the vertical d.o.f., for which the geophones suffer less from tilt, I changed that first to s0=3 (0.5 Hz); this gives a good improvement but still extra noise from the low-passed LVDTs spoil the optimal resolution at 1-5 Hz; therefore I tried s0=2. From the transfer function between LVDT and geophone (with pid control off, so large excursions) we see that the geophone and LVDT are in agreement above 0.1 Hz (both phase and amplitude; below 0.1Hz the geophone has lots of extra noise and the phase difference becomes problematic.
Filtering at s=2 for the vertical channels seems to work fine; although I am not completely sure if the reconstructed blended displacement peaks at 0.2-0.3 Hz are reliable. Both the LVDT and the geophone give more strength than the blended signal which is damped in the loop, but also the raw Geophone and LVDT signals are damped a lot so I think that the situation is OK.
We do have still a little bit of extra noise, but that is at the 20% level, whereas the LVDT noise in the range 1-100 Hz is about 100x higher than it used to be. When the electronic LVDT noise disappears, we can change back the filters.
plots: oldblending: the low and high blending signals for Tx before change of filters, blending at 1Hz
blending_s3noact - blending at 0.5Hz, no actuators on
blending_s2_viscous - blending with viscous control, at s=2 (0.3 Hz)
blending_s2_pid - blending with the PID loop closed
dof_blended : the geophone, LVDT, and total bench blended signal with the PID loop closed
aug13 : the same plot before the EIB intervention, and before the issue with the noise in the vertical LVDTs.
at 3 Hz we reach nm/nrad per sqrtHz now, just as before.
I keep the loops closed; EIB is ready for science mode again.
This afternoon, we went back to the detection tower to check the position of the motorized counter weight (on which we performed -34000 steps yesterday evening). We observed that the translation stage is about 0.5 mm from its zero position, which we considered reasonable.
Fig.1 shows the values of the angular corrections applied on the marionetta.
We then gave green light to the VAC team for the closing and evacuation of the SDB1 tower. We opened the angular control and the OMC temperature stabilization loop.
While checking with the operator the status of the position loops we realized that we had forgotten to close them in the morning. On Fig.2 we check the evolution of the SDB1 bench position between yesterday morning when we took the alignment reference (around 10h00-11h00 utc) and the position of today. We can see that they are very similar despite the fact that the loops were not closed today.
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Since we could not replug the B5_M1_TX picomotor on SDB1, we have unpluged the cable from the picomotor driver 8742 SN 10592, channel 4. The cable is left free, we have attached a sticker on it with the label "B5_M1_TX".
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The permit to work is now close, lasers are allowed in the SDB1 tower.
The beam dump that was placed on the reference beam path of the B1p PC on August 13th has now been removed. The beam dump is stored inside the rack of the DET lab.
Operation notes: standard floor cleaning; Particles Air Counter removed; N2 blowing system removed; Si-wafers rotated; double o-rings pumped
ITF found in SINGLE_BOUNCE_NI (with PR misaligned about 30 urad in ty), in COMMISSIONING mode.
planned activty:
- SDB1 intervention (Gouaty, Romero). Activity concluded at 14:30 UTC.
- 11:30 UTC Melo in Laser Lab to block the beam in order to allow Bulten to work on the eccess of noise on EIB.
SBE
11:30 UTC - SIB2_SBE loop opened for unknown reason. Properly closed via VPM. Unfortunately the loop opened again after 10 min. I contacted Bulten who fixed it at 12:15 UTC.
Around 11:30h UTC I went to the LL and blocked the beam at the output of LB to allow works on the EIB for the excess noise found since last Friday (see #69600). BPC loop is open and INJ node in metatron is in down and paused.
WE WRITE AND POST THIS ENTRY A SECOND TIME SINCE IT WAS ERASED FROM THE LOGBOOK AFTER OUR FIRST ATTEMPT.
This morning we performed another round of alignment checks after the intervention in SDB1.
Air flux is off, BS-SR valve open to let the NI single bounce beam reach the SDB1 bench, nitrogen blowing on the cryotrap window.
The suspension control of SDB1 were restored by Paolo yesterday night. SDB1 angular control are closed.
Noticing that the height of SBD2 has drifted away during the night, we remove a few temporary weights to adjut the bench height close to 500 um. Then we close SDB2 angular and position loops.
We then check the position of the beam on B1p camera. it is too high. Thefefore we change the SDB1 angular setpoints to recenter it : in TX setpoint changed from 60 to 15 um, in TY setpoints changed from 20 to 27 um. After this adjustment we checked the position of the B1s beam on the silicon beam dump on SBD2 (using an IR card) and it was found well inside the beam dump.
We open the OMC shutter and check that the B1s beam is well centered in its camera (Fig.1). Initially we read a power of about 40 mW on B1s (Fig.2). Then we checked that the B1s beam is still passing through the iris placed at the input of the EDB bench.
We performed an OMC scan and found the following powers per mode:
- TEM00 mode: containing a power of 1uW (see Figs. 3 and 4)
- 1st HOM: containing a power of 2uW (see Fig. 5 and 6)
- 2nd HOM: containing a power of 1.8uW (see Fig. 7 and 8)
- 3rd HOM: containing a power of 2uW (see Fig. 8 and 9)
- 4th HOM: containing a power of 2uW (see Fig. 10 and 11)
- 5th HOM: containing a power of 2uW (see Fig. 12 and 13 )
This makes a total of 10.8uW. Assuming a calibration factor of 4800 on B1_PD3, we get a total power of 52mW, compared to the B1s power of about 70mW.
We check that the B1p, B1s and B5 galvo loops centering is working well (Fig.14). In order to be able to close the B5_QD1 galvo loop we had to perform a little adjustment (order of 1500 counts) with the picomotors B5_M2. REMEMBER TO UPDATE THE NAMES OF THE PICOMOTORS WHICH ARE NOW VERY CONFUSING (B5_M1 for B5_QD2 now on the B1s beam, versus B5_M2 for B5_QD1).
This concluded our alignment check.
We close the OMC shutter, open the SDB2 local controls. Remove SDB2 temporary weights, remove EDB irises.
We close the SDB2 vacuum chamber and starts the pumping around 10h30 utc.
We ask the VAC team to close the BS-SR valve as we do not need the laser hazard in DET tower any more. The air flux in the tower is switched back on. We close the nitrogen bottle.
We inform the Laser Safety Officer that laser hazard it not needed any more inside the DET tower.
After the daily meeting we started the intervention in SDB1.
After switching off the laser; we entered the tower and started by blocking SDB1. Then, we inspected the bench. We did not notice any anomaly. Hence, we proceeded with the closing and reopening of the fast shutter after verifying the blades were ok.
We then removed the waveplates and their corresponding clamp and screw (539g). We did not remove the beam dump placed in reflection of the waveplate. To be noted that we did not replug the cable that was used for the waveplate (as there was not easy access to recable it to the B5_M1_TX picomotor).
We then unplugged the OMC shutter translation stage. We dismounted the translation stage and replaced it with the spare one. We repluged it and tested successfully.
We add 540 g of weight under the bench to compensate for the weight of the withdrawn waveplate.
We recenter the motorized weight manually.
We then rebalanced the bench and left the detection tower.
However, we noticed in the control room that the TX position has drifted away a bit and the loop could not be closed any more. To fix this we performed -34000 steps with the BENCH_TX motorized counter-weight. We could then close the angular loops as shown on the attached Figure. We notice large fluctuations in TX and TY (+/-10 urad). This may be due to the presence of the air flux in the tower and maybe the thunderstorm.
We leave the tower slightly open, with nitrogen off, and air flow blowing.
Tomorrow, after the recovery of the suspension control, we will perform an alignment verification.
ITF found in COMMISSIONING Mode and DOWN state, with MISALIGNED_ALL_BUT_NI state on ARMS_LOCK node (equal to SINGLE_BOUNCE_NI state from ITF_LOCK)
7:30 UTC OB Top Stage loops opened (operator), DAQ reconfiguration (Masserot), Closing of BS-SR valve (Pasqualetti), SDB1 rack cables swapping (Gouaty, Romero)
8:00 UTC Opening of SDB1 tower bottom flange, hood with nitrogen flow installation on cryotrap viewport (Vacuum team)
8:12 UTC SDB2 LC troubleshooting and rebalancing (Gouaty, Romero)
9:30 UTC Opening of SR-BS valve (Pasqualetti)
12:00 UTC INJ troubleshooting on EIB (Gosselin, Melo, Ruggi)
12:30 UTC Closing of SR-BS valve (Pasqualetti)
13:00 UTC entering SDB1 tower to change OMC shutter traslation stage (Gouaty, Romero, Menzione)
At 14:00 LT, we went into the LL to perform a more detailed inspection of the EIB bench. We first put the beam in scan mode and blocked it at the LB output.
We then opened the bench controls and slightly moved the plexiglass tube leading to the SIB1 tower, as it appeared to be in slight contact with the bench. However, a comparison of the FFT signals before and after the intervention showed no significant change, suggesting that the contact was not the cause of the excess noise. No other obvious issues that could explain the increased noise were identified during the inspection.
We then unblocked the beam, re-locked the INJ system, and left the LL at approximately 14:40 LT.
Afterwards, we continued analysing the data. Paolo identified some LVDT signals, particularly the vertical 0 and 2 channels, that are significantly noisier than they were previously (see Fig. 1). A similar issue appears to have occurred in the past (see #57229), where the solution was to implement a low-pass filter to attenuate the excess noise.
It would therefore be useful to investigate whether this filter is still correctly implemented and functioning, or whether another issue is currently responsible for the additional LVDT noise.
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Today, after the venting of the SDB1 tower was completed, the VAC team opened the SDB1 tower around 08h30 utc and installed the nitrogen setup blowing on the cryotrap window.
Meanwhile we performed some actions on the SDB1 rack:
➢ disconnect the SDB1 waveplate that we are going to remove from Agilis driver AG_UC8, channel 3 axis 2.
➢ Replug the cable on the picomotor driver 8742 SN 10592, channel 4 (B5_M1_TX)
The VPM main configuration has been updated accordingly to remove the button related the driving of the Pre-Faraday waveplate under SDB1_Rot process.
Noticing that the height of SDB2 bench had changed during the night, we went inside the DET lab to remove some mass from the bench and we were able to recover the right height, and to close the angular and position loops. However we lost the DAQ box LeftUp shorhtly after. So we had to reopen the control loops.
Paolo recovered the SDB1 bench position and the SDB1 local control could be closed.
We adjust the gain of the OMC Peltier to 20 (instead of 50) in order to be able to control the OMC in air. OMC temperature stabilization closed at 9h33 utc.
SDB2 control restored at 10h14 utc.
Antonio switch off the air flux inside the tower at 10h20 utc.
We take some alignment references with NI single bounce beam:
* SDB1 LC is set to TX = 60 (instead of previous WP at 120) / TY = 20 (instead of previous WP at 60)
* B1p camera is centered, with Pos X = -0.1, Pos Y = +0.15
We open the OMC shutter at 10h42m50 utc. We have 4 mW on the B1s beam. The beam is centered on B1s camera at position X = 0, Y = 0
To be noted that we observe an electronic offset of 31.2 mW on DET_B1p_DC when B1p_PD2 shutter is closed. We read 34 mW when the shutter is opened, which implies a power on B1p beam equal to about 3 mW which is in reasonable agreement with B1s power.
We open B1 PD1 and PD2 photodiodes at 10h52 utc.
We scan the OMC and observe the following modes:
* 0.1 mW on the TEM00
* 0.17 mW on the first order mode
* 0.3 mW on the second order mode
* 0.5 mW on the order 3
* 0.5 mW on the order 4
* 0.21 mW on the order 5
We close the OMC shutter, open the controls. Next step will be to perform the foreseen installation works inside the tower.
Since we could not replug the B5_M1_TX picomotor on SDB1, we have unpluged the cable from the picomotor driver 8742 SN 10592, channel 4. The cable is left free, we have attached a sticker on it with the label "B5_M1_TX".
All the SDB2 DBoxes wer reconfigured but without any improvments .
As trial the output of the B5_QD1 and B5_QD2 demodulation sample data were commented and in these conditions , all the data were correctly received by the SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout servers.
To restore all the SDB2 demodulation sample data, for all the demodulation sample output packets the output frequency is now set to 2kHz instead of 5kHz with 16 words of 32bits.
Labels are in place and the laser hazard can be turned on following the authorized procedure.
No other laser hazard can be turned on and propagated to the SDB1 tower.
The permit to work is now close, lasers are allowed in the SDB1 tower.
We ask to the Laser Safety Officer the authorization to turn on the laser hazard inside the detection tower, by opening the BS-SR valve.
Please confirm that no laser beam hazard (Nd-YAG, CO2, etc.) is present inside the DETECTION tower
Nevertheless, we have some extra noise in the band 1-10 Hz. I checked all raw signals (voice coils, geophones, LVDTs) and they seem all correct. I switched off the MotorSAS process in the vpm, since the driver coils can make electronic noise, but that did not change anything. In the evening when Romain gave the green light, I switched off controls, switched on viscous damping, and switched on the full pid. With the full pid the ground motion is damped well below 1 Hz but there is an extra shoulder between 1-10 Hz. I think it arises in Tx and Tz and is coupled to Ty,x,z via the tilt stabilization but this is just conjecture. Suzanne did not find anything rubbing against the bench, but maybe there is some small detail. I did not see much difference in acoustic noise (such an effect on the bench, bypassing the floor, could maybe cause such a shoulder) and I checked that the actuators and pid have the same transfer functions as last week (plotting the transfer function from actuator current to bench motion) so it is difficult to find the cause of the extra noise now; it seems all sensors and actuators are performing as well as last week,
The only "large" difference is that there is now some 10 times more noise at the secondary microseismic peak (0.3 Hz); this peak is damped well. It should not spoil the pid at 3Hz, but we may hope for improvement on a quieter day.
Included are the files of the d.o.f. and time signals of the actuators with actuation off/only viscous (first attachment), actuation off/pid (second attachment), a comparison to last week (3rd file), and the raw signals/seismic motion for today and last week (4th and 5th file). The excess noise shoulder is obvious, but the damping is good at 0-1 Hz and similar at +10 Hz.
At 14:00 LT, we went into the LL to perform a more detailed inspection of the EIB bench. We first put the beam in scan mode and blocked it at the LB output.
We then opened the bench controls and slightly moved the plexiglass tube leading to the SIB1 tower, as it appeared to be in slight contact with the bench. However, a comparison of the FFT signals before and after the intervention showed no significant change, suggesting that the contact was not the cause of the excess noise. No other obvious issues that could explain the increased noise were identified during the inspection.
We then unblocked the beam, re-locked the INJ system, and left the LL at approximately 14:40 LT.
Afterwards, we continued analysing the data. Paolo identified some LVDT signals, particularly the vertical 0 and 2 channels, that are significantly noisier than they were previously (see Fig. 1). A similar issue appears to have occurred in the past (see #57229), where the solution was to implement a low-pass filter to attenuate the excess noise.
It would therefore be useful to investigate whether this filter is still correctly implemented and functioning, or whether another issue is currently responsible for the additional LVDT noise.
I spent friday afternoon/evening to implement lower blending in the pid for the vertical d.o.f. of the external injection bench.
We blend the LVDTs with the geophones on the bench, and also with the ground geophones. The LVDT measure between bench and ground and we subtract ground noise (LVDT_y is the LVDT signal, LVDT_yb contains added ground monitoring geophone, and GEO_y is the geophones on the bench, etc). The geophones and LVDTs are then blended with an (s+s0)^5 filter. For the horizontal LVDTs, which still show normal noise so below 1 nm/sqrt(Hz) above 3 Hz, we blend at s0 =6 (almost 1Hz), since blending at the resonances of the bench is problematic. For the vertical d.o.f., for which the geophones suffer less from tilt, I changed that first to s0=3 (0.5 Hz); this gives a good improvement but still extra noise from the low-passed LVDTs spoil the optimal resolution at 1-5 Hz; therefore I tried s0=2. From the transfer function between LVDT and geophone (with pid control off, so large excursions) we see that the geophone and LVDT are in agreement above 0.1 Hz (both phase and amplitude; below 0.1Hz the geophone has lots of extra noise and the phase difference becomes problematic.
Filtering at s=2 for the vertical channels seems to work fine; although I am not completely sure if the reconstructed blended displacement peaks at 0.2-0.3 Hz are reliable. Both the LVDT and the geophone give more strength than the blended signal which is damped in the loop, but also the raw Geophone and LVDT signals are damped a lot so I think that the situation is OK.
We do have still a little bit of extra noise, but that is at the 20% level, whereas the LVDT noise in the range 1-100 Hz is about 100x higher than it used to be. When the electronic LVDT noise disappears, we can change back the filters.
plots: oldblending: the low and high blending signals for Tx before change of filters, blending at 1Hz
blending_s3noact - blending at 0.5Hz, no actuators on
blending_s2_viscous - blending with viscous control, at s=2 (0.3 Hz)
blending_s2_pid - blending with the PID loop closed
dof_blended : the geophone, LVDT, and total bench blended signal with the PID loop closed
aug13 : the same plot before the EIB intervention, and before the issue with the noise in the vertical LVDTs.
at 3 Hz we reach nm/nrad per sqrtHz now, just as before.
I keep the loops closed; EIB is ready for science mode again.
Today I reconfigured the 4 DAQ boxes of SDB2 in order to solve timing issues resulting from our intervention on the bench.
The reconfiguration took place between 21h59 and 22h03 utc.
The Timing flag in the DMS is back to green, however, since the reconfiguration the processes SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout seem to be misbehaving. A DAQ expert has been informed;
All the SDB2 DBoxes wer reconfigured but without any improvments .
As trial the output of the B5_QD1 and B5_QD2 demodulation sample data were commented and in these conditions , all the data were correctly received by the SDB2_Photodiodes, SDB2_Quadrants and SDB2_Readout servers.
To restore all the SDB2 demodulation sample data, for all the demodulation sample output packets the output frequency is now set to 2kHz instead of 5kHz with 16 words of 32bits.
As agreed during the daily meeting, we post this entry to inform that we have completed our activities on SDB2, and we do not need the NI single bounce beam any more until the SDB1 tower venting is completed (tomorrow morning).