We aligned PRMI and inspected BS chamber. Last inspection by Jamie and I (see elog #6897) was done when nothing is aligned, so I wanted to see the difference.
Aligning PRMI at low power was difficult for me, because I see no fringe at ASDC PD nor REFLDC PD. I just aligned them by looking at AS/REFL camera. The beam shape at AS looked as bad as when the usual power.
No significant change was found inside the vacuum. We still see clipping at the Faraday, and also, we saw clipping by BS coil holder. Using PZT1, we could make it better, but this might be causing PRC problem -- BS is inside the PRC, too.
We also took some pictures of PR3 and PRM(attached). The arrow pointing HR is correctly pointing inside the PRC. Seeing is believing.
We might have to avoid clipping at BS (and Faraday) by aligning input optics inside the vacuum. If we are going to align them, I think we should start from centering MC beam spot positions and the whole alignment could take more than a week. I don't want to spend too much time on the alignment. Also, we are going to install tip-tilts on the next big vent, so we have to redo the alignment anyway.
So, my plan is as follows;
1. Take lots of photos and close the door on Monday(June 2).
2. Pump on Tuesday(June 3).
3. Restart working on ALS. For example, demonstration of FPMI using ALS.
4. We also can do some characterization of PRC, like measuring power recycling gain for PRMI/PRFPMI, mode scan for PRC using AUX laser from AS port, and so on. We need some calculation for clipping tolerance, too.
Start pumping on Monday before Steve goes home.
I attached clipping/centering checklist for the alignment.
Blue ones are the ones we checked today. Red ones should be checked tomorrow. Circles indicate centering on the optics, rectangles indicate clipping check, and arrows indicate retro-reflecting or bounces.
We found mis-centering on MMT1, PR2 and SR3 tonight (by ~0.5 beam diameter). They are also indicated.
I think we don't want to touch MMT1 and PR2 anymore, because they change input beam pointing.
I'm a little bit concerned about high beam on SR3, because we had PRC flashing in vertical higher order modes. We also see ETMX slider values high in pitch (~ 5.4).
Also, the diameter of ETMX reflected beam on ITMX looked larger and dimmer than ITMX transmitted beam, which doesn't seem reasonable.
Wednesday, Feb 20:
- tweak TT1/TT2 and PRM so PRC flashes
- re-check Yarm/Xarm bounces
- center beam on all AS optics, starting from SR2
- make sure REFL and AS is clear
- check if TRY/TRX are coming out from the ends
- check beam centering on mirrors in IMC/OMC chamber as far as you can reach
- inject green from both ends
- make sure green beams are not clipped by mirrors on BS chamber, IMC/OMC chamber
- re-center all oplevs, with no clipping
- check all OSEM values
- take pictures of flipped PR2 and input TTs (and everything)
- close all heavy doors and put the access connector back
Thursday, Feb 21:
- make sure we can lock PRMI
- start pumping down when Steve arrives
Blue ones are the ones we checked yesterday.
Green ones are the ones we checked today.
Red ones are the ones we couldn't check.
We noticed mis-centering on green optics and partial clipping of higher order modes, but we did not touch any green optics in-vac. This is because green beam from Y end and X end has different spot positions on the green optics after periscopes. We confirmed that direct green beam from ends are not clipped.
I believe we have checked everything important. Any other concerns?
Is the beam going towards the OMC going to cause backscatter because of uncontrolled OMC or can we park that beam somewhere dark?
I'm not sure about the OMC situation at 40m. I think there are no direct beam reflected back into IFO from OMC path. There must be some backscatter, but we have to open OMC chamber again to put a beam dump.
I don't think we want to put one in OMC path for this pump-down, but we can put a beam dump to dump reflected beam from mis-aligned SRM tomorrow, if available.
The input pointing of PRM oplev beam was streered just a touch to remove clipping from it's return.
The spots did not move visibly on these two lenses. The spot diameter on the qpd is ~1.5 mm, 65 micro W and 3440 counts.
I'm not happy with the beam position on that first lens, but since it's so crazy in the BS chamber, and the PRM oplev has something like 5 in-vac steering mirrors, I'm hesitant to suggest that we do anything about it until our next vent. But we should definitely fix it.
[Koji / Kiwamu]
We tried finding a possible clipping in the vertex part.
We couldn't find an obvious location of a clipping but found that the recycling gain depended on the horizontal translation of the input beam.
We need more quantitative examination and should be able to find a sweet spot, where the recycling gain is maximized.
(what we did)
+ locked the carrier-resonant PRMI.
+ with IR viewers we looked at the inside of ITMX, ITMY and BS chambers to find an obvious clipping.
=> found two suspicious bright places and both were in the ITMY chamber.
(1) POY pick off mirror : looked like a small portion of a beam was horizontally clipped by the mirror mount but not 100% sure whether if it is the main beam or a stray beam.
(2) The top of an OSEM cable connectors tower : although this is in the way of the SRC path and nothing to do with PRC.
+ Made a hypothesis that the POY mirror is clipping the main beam.
+ To reject/prove the hypothesis we shifted the translation of the incident beam horizontally such that more beam hits on the suspicious mirror
+ Realigned and relocked PRMI.
=> Indeed the recycling gain went down from 6 to 0.8 or so. This number roughly corresponds to a loss of about 50%.
However the MICH fringe still showed a very nice contrast (i.e. the dark fringe was still very dark).
Therefore our conclusion is that the POY mirror is most likely innocent.
The rubidium clocks are still not quite locked together, though it is clear that the beat frequency has dropped a lot since yesterday.
I checked on the clocks and the 1pps sync light is on. The clocks are really hot again though despite the gap left at the bottom of the igloo. The side of the clocks were hot enough to not be touchable.
I made the executive decision that I would remove the hut just now. We can let the clocks lock together and then put the hut back on just before measuring. This way the hut will isolate from temperature fluctuations during the measurement but it won't be running at the hotter equilibrium temperature. I hope that the temperature won't change too much during the measurement if we put the hut back on.
RA: Attachment deleted because it was in Postscript format. Also not allowed here are the Stone Tablet and Cave Painting formats.
I tried to get the clocks to be closer to 90 deg for the relative phase by adding some cable length to one of the lines, but they are still wandering too much. We need to use the serial interface and up the gain in their 1PPS locking loops.
The shutter before the MC was closed at 3:30 as I started working on the RFAM.
MC REFL (INLOCK): 0.6~0.7
MC REFL (UNLOCK): 6.9
MC TRANS: 50000~52000
Finished the work at 6:30
MC REFL (INLOCK): 0.50-0.52
MC REFL (UNLOCK): 6.9
MC TRANS: 54400~547000
Before the work: -48.5dBm for 1.07VDC (both 50Ohm terminated)
Right after the work: -80dBm for 0.896VDC (both 50Ohm terminated)
10min after: -70dBm
1hour after: -65dBm
3hours after: -62dBm
1day after (Oct 5, 20:00): -62.5dBm
2days after (Oct 6, 23:20): -72.5dBm
3 days after (Oct 7, 21:00): -57.8dBm
MC REFL (INLOCK): 0.6~0.7
MC REFL (UNLOCK): 6.9
MC TRANS: 50000~52000
The door was not locked this morning.
Please do not use this door if you can not close it!
Last person leaving the lab should check that the latch is cut by the strike plate.
This is one of those unsolved door lock acquisition problems. Its been happening for years.
Please ask facilities to increase the strength of the door tensioner so that it closes with more force.
It was requested this morning.
I found the south end emergency doors not latched completely. There was a ~ 3/8" vertical gap from top to bottom.
Please pull or push doors harder if they not catch fully.
The signal observed by the coarse frequency discriminator was actually dominated by the ADC noise above 30 Hz.
It means that once increasing the UGF more than 30 Hz the servo will feed the ADC noise to the test mass and shake it unnecessarily.
I guess this could be one of the reasons of the unstable behavior in the Y end PDH lock (#6071).
(But still it doesn't fully explain the instability).
To improve the situation I am going to do the following actions:
(1) Installation of a whitening filter (probably use of SR560s)
(2) Redesign of the servo filter
Here is a brief noise budget of the coarse sensor.
Gray curve: free running noise when no servo is applied
Green curve : in-loop noise when the ALS loop is closed with the coarse frequency-discriminator. The UGF was at 30 Hz.
Red curve : ADC noise of the coarse discriminator
So far I still kept failing to increase the UGF of the ALS servo for some reason (see #6024).
We succeeded in coarse locking the green beat frequency, using a frequency counter and feeding back the signal to the X-end laser temperature.
beat note -> RF PD -> SHP-25 -> SLP-100 -> ZFL-1000LN -> ZFL-1000LN -> ZFL-500LN -> ZFRSC-42 -> SBP-70 -> ZFRSC-42 -> SR620 -> c1psl(C1:PSL-126MOPA_126MON)
c1auxey(C1:LSC-EX_GREENLASER_TEMP) -> X-end laser temp
The frequency counter SR620 converts the beat frequency to voltage.
We added some filters (SHP-25, SLP-100, SBP-70). Otherwise, SR620 doesn't count the frequency correctly.
What we did:
1. Getting green beat note again
Set PSL laser temp to 31.81 °C and X-end laser temp to 37.89 °C.
Set PPKTP crystal temp to 37.6 °C, which maximizes output green beam power.
2. ADC channel and DAC channel
Disconnected one channel going into VME-3123 (at 1X1) and used c1psl's C1:PSL-126MOPA_126MON as ADC channel for the output from SR-620
Made a new DAC channel on c1auxey named C1:LSC-EX_GREENLASER_TEMP, and disconnected one channel from VME-4116 (at 1X9) to use it as DAC channel for X-end laser temperature control.
3. Coarse lock by ezcaservo
ezcaservo C1:PSL-126MOPA_126MON -s 150 -g -0.0001 C1:LSC-EX_GREENLASER_TEMP
"-s" option is a set value. The command locks C1:PSL-126MOPA_126MON to 150 (in counts), using 0Hz pole integrator.
The beat frequency locked on to ~77MHz. The frequency fluctuation of the beat note during the servo is ~3MHz with ~10sec timescale.
VCO has ~+/-5MHz range, so this coarse locking meets the requirement.
Here's a plot of the error signal and feed back signal;
ezcaservo C1:PSL-126MOPA_126MON -s 150 -g -0.0001 C1:LSC-EX_GREENLASER_TEMP
Wow! Great guys!!
Can I expect to see the spectra of the frequency counter output with and without the servo?
RA: I think the SBP-70 is a bad idea. It limits the capture range. So does the SHP-25. You should instead just use a DC-block; the SR620 should work from 1-200 MHz with no problems.
Also, we have to figure out a better solution for the DAC at the ends: we cannot steal the QPD gain slider in the long run and the 4116 DAC at the ends has all 8 channels used up. Should we get the purple box for testing or should we try to use the fast DAC in the EX IO chassis as the actuator?
I coarsely stabilized Y arm length to off resonance point for IR using ALS.
Currently, ASL servo loop is unstable and oscillates so much that I can't hold the length to the resonance point.
We need more investigation on the servo loop before doing the mode scan.
Below is a snapshot of ALS medm screens and time series data of the error signal for ALS coarse loop (C1:ALS-BEATY_COARSE_I_ERR) and IR transmission for the Y arm (C1:LSC-TRY_OUT) when I turned the servo on.
I took off amplifiers right after the beat PD on PSL table.
Also, I reverted the gain change Jenne made last night (elog #6750), because they no longer show overload lights.
# ipc connections: (from, to, number)
ipcs = [
('c1scx', 'c1lsc', 1),
('c1scy', 'c1lsc', 1),
('c1oaf', 'c1lsc', 8),
('c1scx', 'c1ass', 1),
('c1scy', 'c1ass', 1),
The Zojirushi lid is a two part mechanism:
We still think about the coherence between seismic noise and mode cleaner length. We beleive that
1. Below ~0.1 Hz tilt affects on the seismometers as was simulated http://nodus.ligo.caltech.edu:8080/40m/5777
2. From 0.1 to 1 Hz is an interesting region. We try to figure out why we do not see any coherence here. Tilt does not seem to dominate.
At 1 Hz coherence might be lost because of the sharp resonance. For example, if the mirror is suspended to the platform by wires with f = 1 Hz and Q = 1000, then the coherence between platform motion and mirror motion will be lost as shown on the figure below.
For this reason we tried to "help" to the adaptive filter to guess transfer function between the ground motion and mirror motion by multiplying seimometer signal by the platform -> mirror transfer function. As we do not know exactly eigen frequency and Q of the wires, we did a parametric simulation as shown on the figure below
The maximum coherence that we could achieve with treak was 0.074 compared to 0.056 without. This was achieved at f=1.0011 Hz but with surprisingly high Q = 330. And though this did not help, we should keep in mind the tecnique of "helping" the adaptive filter to guess the transfer function if we partly know it.
Another unexpected thing is that we see come coherence between gur1_x and mode cleaner WFS pitch signal at frequencies 0.1 - 1 Hz
From this we can suggest that either mode MC_F channel does not completely reflect the mc length at low frequencies or WFS2 shows weard signal.
The 'helping' trick is a good one: we should use our best guess for the stackTF and the pendulumTF and put it into the IIR filter bank to pre-filter the seismometer signals before they get to the MC mirrors. Also should remember that the signal we send to suppress the seismic motion is applied to the pendulum as a force, not a displacement.
The 3 Hz fast cutoff in the MC_F signal is a good clue. It means that at low frequencies, perhaps the noise source is going through a digital 3 Hz elliptic or Chebychev filter.
I've looked through the coherence between the MC length and seismometers after the if-statement problem was fixed. Coherence improved for all seismometers but is still not 1. It is possible that contribution from X, Y, Z directions split the coherence between them but at ~0.2-03 Hz we do not see much coherence for all these directions.
I looked at the coherence between MC2 OSEM signal and MC_F when the AUTO LOCKER is ON and OFF. I thought that we'll ses the same coherence for both regimes as laser is locker to the MC length. However, I figured out the coherence is worse when AUTO LOCKER is ON at frequencies 0.2-0.3 Hz.
The first idea that comes to mind is that when feedback to the laser is provided, the pressure to the mirrors from the laser beam is changed.
I used the coh_carpet.m function from the mDV to calculate this plot:
coh_carpet('C1:PEM-ACC_MC1_X','C1:PEM-ACC_MC2_X',gps('now - 3 days'),3600*12,4,10,64)
It shows the coherence v. time of two of our X-direction accelerometers starting around 1AM on Friday and going for 12 hours.
I'm not sure what it means exactly, but it looks like the coherence is relatively steady as a function of time. I will need more RAM than Rosalba or a smarter code to calculate longer time stretches.
We've been talking about increasing the series resistance for the coil driver path for the test masses. One consequence of this will be that we have reduced actuation range.
This may not be a big deal since for almost all of the LSC loops, we currently operate with a limiter on the output of the control filter bank. The value of the limit varies, but to get an idea of what sort of "threshold" velocities we are looking at, I calculated this for our Finesse 400 arm cavities. The calculation is rather simplistic (see Attachment #1), but I think we can still draw some useful conclusions from it:
So, from this rough calculation, it seems like we would lose ~25% efficiency in locking the arm cavity if we up the series resistance from 400ohm to 1kohm. Doesn't seem like a big deal, becuase currently, the single arm locking
We have two cold cathode gauges at the pump spool and one signal cable to controller. CC1 in horizontal position and CC1 in vertical position.
CC1 h started not reading so I moved cable over to CC1 v
Our cold cathode 423 gauges are 10 years old. They get insulated by age and show no ionization current. We should replace them at the next vent. I'm buying 4 at $317ea
CC4 cold cathode gauge jump triggered interlock to close VM1 valve to protect the RGA.
The IFO pressure is 1e-5 Torr
Vac normal was recovered by opening VM1
The cold cathode gauge is back to normal. cc4 is the last gauge is "functioning"
MKS is not responding. The spare controller and gauges are back for repair.
The IFO pressure is estimated ~1E-6 Torr with modified Vac normal valve configuration.
CC4 is in a jumping mode between 2e-5 and 1e-6 Torr
Pressure based interlock kicks in to close VM1 at 2e-5 Torr to protect the RGA.
I did open VM1 repeatedly in the last few mornings but as cc4 jumps VM1 closes.
As VM1 closed to RGA scans are not seeing the IFO. I will look at some scans on Monday.
Mean while I opened VM2 to lower the pressure for the RGA. This change will be read by "Current Status: Undefined State"
So do not panic, the IFO pressure is normal.
I need someone's help to raise the interlock threshold to 5e-5 Torr
I'm buying a new cold cathode gauge on Monday.
note: cc1 is out of order!
just read P1 the pressure is < 7e-4 Torr This gauge is very reliable and it is at the low end of it's range.
A comparator has been installed before the MFDs (mixer-based frequency discriminator) to eliminate the effect from the amplitude fluctuation (i.e. intensity noise).
As a result we reached an rms displacement of 580 Hz or 80 pm.
As a result we reached an rms displacement of 580 Hz or 80 pm.
(differential noise measurement)
Here is the resultant plot of the usual differential noise measurement.
The measurement has been done when the both green and red lasers were locked to the X arm.
In the blue curve I used only MFD. In the black curve I used the combination of the comparator and the MFD.
Noise below 3 Hz become lower by a factor of about 4, resulting in a better rms integrated from 40 Hz.
Note that the blue and the black curve were taken while I kept the same lock.
A calibration was done by injecting a peak at 311 Hz with an amplitude of 200 cnt on the ETMX_SUS_POS path.
Yesterday Koji modified his comparator circuit such that we can take a signal after it goes thorough the comparator.
The function of this comparator is to convert a sinusoidal signal to a square wave signal so that the amplitude fluctuation doesn't affect the frequency detection in the MFD.
I installed it and put the beat-note signal to it. Then the output signal from the comparator box is connected to the MFDs.
The input power for the comparator circuit has been reduced to -5 dBm so that it doesn't exceeds the maximum power rate.
I have modified the code for frequency scanning and have made it completely command line enabled. The code is written in python. It is saved in the name "frequency_scanning_argparse.py". I have uploaded it to the Mode-Spectroscopy Github repository.
Inorder to use this code there are two ways.
1. We can mention the ' frequency' on which marconi need to work. Then it will change the marconi frequency to that perticular value.
eg: Type in the terminal as follows for changing the marconi frequency to 59 Mhz.
python frequency_scanning_argparse.py 59e6
2. Inorder to give a scan to the marconi frequency, provide the 'start frequency', 'end frequency' and the 'number of points' in between. This will be more conveniant when we want to run the scan in different ranges.
eg: Type in the terminal as follows for a start frequency of 59 Mhz, end frequency of 62MHz and number of points in between equal to 1000.
python frequency_scanning_argparse.py 59e6 62e6 1000
In both cases the code will show you the frequency of the marconi before we run this code and it will change the marconi frequency to the desired frequency.
Well, let's see how the CM servo can handle this.
The key point here is that we have enough data to start the design of the CM servo.
It seems to me that current design of the common mode servo is already fine. Attached plots show common mode open and closed loop transfer function.
Frequency response of the servo is taken from the document D040180. I assumed coupled cavity pole to be ~100 Hz.
The only question is if our EOM has enough range. Boost 2 increases noise injection by 10 dB in the frequency range 20-50 kHz. Boost 3 has even higher factor.
Once the control cable (bakplane cable) is identified, we can install the module to the LSC analog rack.
We should be able to test the CM servo with either POX or POY and only one correspoding arm without modifying the servo TF.
Just for this test, we don't need to use MCL.
These seem like pretty terrible loop shapes. Can you give us a plot with the breakdown of several of the TFs and some .m file?
We should be able to estimate the noise coming out of the MC using the single arm and then make a guess for the CM loop gain requirement. There's no reason to keep the old Boost shapes; those were used in the old MC configuration which had a RefCav. In addition to minimizing the EOM range, we should also minimize the AO signal as Koji has pointed out. In practice, I've seen that using ~300 Hz of offset makes no harm with 4 kHz MC pole.
Attached is matlab code that I used
% IMC OL
G = zpk(-2*pi*8964, 2*pi*[-10; -10; -10; -1000; -274000], db2mag(242.5)) * ...
tf([1 0.8*1.55e+05 3.1806e+10], 1);
% CARM PATH
CARM = G/(1+G);
% Common mode boosts
BOOST = zpk(-2*pi*4000, -2*pi*40, 1);
BOOST1 = zpk(-2*pi*20000, -2*pi*1000, 1);
BOOST2 = zpk(-2*pi*20000, -2*pi*1000, 1);
BOOST3 = zpk(-2*pi*4500, -2*pi*300, 1);
% Coupled cavity pole
CCPole = zpk(, -2*pi*100, 2*pi*100);
% Servo gain
Gain = db2mag(43);
% CARM OL with boosts
H = CARM * CCPole * BOOST * Gain;
H1 = H * BOOST1;
H2 = H1 * BOOST2;
H3 = H2 * BOOST3;
% bode(H, H1, H2, H3, 2*pi*logspace(3, 5, 10000));
% bode(1/(1+H), 1/(1+H1), 1/(1+H2), 1/(1+H3), 2*pi*logspace(3, 5, 10000));
We wish to study the coherence of the two NPROs i.e. PSL and the X-end-NPRO by locking both of them to the X-arm and then observing the green beat frequency fluctuations.
What we did:
a) locked the PSL to the X-arm as described in 4153
b) locked the x-end-NPRO to the X-arm with a PDH lock to the reflected green from the ETMX
c) Obtained the green beat signal with a spectrum analyser as described in 3771
Please see the attached screen shots from the spectrum analyser. They are taken with different BW and sweep range settings. They give a estimate of the width of the green beat signal and the range of the frequency fluctuations of the beat-note.
a) width of the beat note is less than 6KHz if measured over time scales of a few milli seconds
b) the frequency fluctuations of the beat note are about 100KHz over time scales longer than 100ms
We wish to record the beat note frequency as a function of time in order to establish the stability over time scale of a day.
Today we attempted to convert the beat-note frequency into an analog voltage using the SR620 frequency counter.
First an observation: the stability of the green beat was seen to be much better than the 100kHz fluctuation seen yesterday. Probably because Kiwamu noticed that one of the MC mirrors had a large variance in its motion and changed the gain and filter parameters to decrease this. The PSL was therefore more stable and the green peak fluctuation was less than 10kHz over time scales of a few seconds.
SR620 D/A output resolution given by the manufacturer is 5mV over the -10 to +10V range and this range corresponding to 300MHz. We, however saw fluctuations of 100mV on the screen which looked as if they corresponded to the least significant bit. This would imply a resolution of 1.5MHz at this range. Even if the manufacturer's claim was true it would lead to a resolution of 75kHz, far in excess of the required resolution a few hundred Hz.
We therefore require to set up the VCO-PLL to obtain a finer frequency resolution.
In the mean time the green beat drifted beyond the 100MHz detection band of the green-PD. So we changed the x-end-NPRO temperature by -0.05 to bring it back into the detection band.
We are also considering, Rana and Koji's suggestion of using a set of 14 flip-flops to divide the ~80MHz beat frequency so that it comes down to about 4kHz. This could then be sampled by the usual 16-bit, 64kSa/s ADC cards and brought into the digital domain where further digital processing would be needed to extract the the required frequency variations in the 0 to 10kHz band. Found a nice paper on this object
>> which decimate
Rack 1x6 is very noisy.
SunFire X4600 computer: FB (directly below Megatron) has it's yellow warning light on. It must be loosing one of it's fan bearings.
Jetstore's error message: IDE channel #2 reading error
It seems that the front fan unit was running at the full speed. The fan itself seems still OK.
I talked with Jamie and make a power cycling (i.e. shutdown gracefully, unplug the power supply cables (x4), plug them in again, and pushed the power button)
The warning signal went off and the fan is quiet. FOR NOW.
Now, daqd and ndsd is down.
FB cannot mount /opt/rtcds and /cvs/cds during its boot.
After mounting these manually, I tried to run /opt/rtcds/caltech/c1/target/fb/start_daqd.inittab and /opt/rtcds/caltech/c1/target/fb/start_nds.inittab
but they don't keep running.
I'll be back to this issue tomorrow with Jamie's help.
All suspentions are kicked up. Sus dampings and oplev servos turned off.
c1iscey and c1lsc are down. c1asc and c1iovme are up-down
The computers and RFM network are up working again. A boot fest was necessary.Then I restored all the parameters with burtgooey.
The mode cleaner alignment is in a bad state. The autolocker can't get it locked. I don't know what caused it to move so far from the good state that it was till this afternoon. I went tuning the periscope but the cavity alignment is so bad that it's taking more time than expected. I'll continue working on that tomorrow morning.
I now suspect that after the reboot the MC mirrors didn't really go back to their original place even if the MC sliders were on the same positions as before.
we diagnosed the problem. It was related with sticky sliders. After a reboot of C1:IOO the actual output of the DAC does not correspond anymore to the values read on the sliders. In order to update the actual output it is necessary to do a change of the values of the sliders, i.e. jiggling a bit with them.
The PSL -leg concrete was sealed with a single coat of SCOFIELD Cureseal-S to minimize shedding of particles.
The optical table was covered and optics were removed from the shelf. Accelerometers were turned off.