After installation we characterized the waist of the bright alignment beam out of the telescope. The first plot in attachment shows the beam radius versus propagation distance (in blue) as compared with the corresponding measurement of the B1 beam from the ITF reflected from the SDB1 Faraday isolator towards the SQZ bench (in red). The positive direction of the propagation distance in the plot goes from SDB1 towards the squeezer. Solid lines represent a fit with the propagation law for Gaussian beams. The new BAB waist radius is 1.01+/-0.02 mm, and the waist position is at 1.7+/-0.07 m from the last steering mirror on the SQZ bench, i.e. very close to SDB1. The second plot shows the measured waist radius versus waist position for the two beams, i.e. B1 and BAB; error bars are given by the standard error from least-squares fitting. The differences between the two beams in terms of waist radius and waist position are now comparable with the overall measurement errors.
The new configuration also implies a longer optical path on the SQZ bench. For this reason the double stage Faraday isolator will have to be displaced from the previous position.
The evacuation of MC, IB and DET towers is in progress...
Below is a summary of the scattered light investigations and mitigation actions performed in the detection tower on the SDB1 bench from Monday morning to Wednesday morning (Jul 9-11).
For the first time it was possible thanks to the preparatory work performed by the locking team last week (many thanks to Julia and Diego!) to perform this investigation while the ITF was locked (0.5 dark fringe) which allowed us to visualize the beams with a relevant mirror configuration (PR aligned) and with a lot of power on the main beam. Most of the scattered light inspections were performed with the bench in-air but suspended. During the installation of beam dumps we managed to block the bench in a position that allowed to have the beam still aligned on the optics, which helped in positioning correctly the beam dumps. Below is a list of problems that we observed and tried to address:
· The most shiny source of scattered light on the bench was located on the large beam dump used to dump 90% of the B1s1 beam (OMC1 reflection). This was due to a damage on the Si plate of the beam dump (see Picture 1) which was presumably caused by flashes happening during ITF unlocks. In order to mitigate this problem, the Si plate has been flipped in its mount (the other side was clear from damage) and the optical path of B1s1 towards this beam dump was modified (see pictures 2 and 3): a diverging lens provided by the EGO optics group (many thanks to Eric, Gabriel and Andrea) was installed approximately at the former location of the beam dump, and the beam dump was moved further way in such a way that the beam size reaching the Si plate is now 3 times larger (so approximately w=2.1 mm). Therefore the power density reaching this beam dump is now about 9 times lower. An additional glass beam dump was installed near the lens (picture 3) in order to dump the residual reflection from the Si beam dump.
· Looking for the residual reflections from the B1p/B1s1/B1s2 minilink viewport we found that they are not at the expected location/height on the bench. This can only be explained by a wrong inclination of the viewport, which must be tilted mostly horizontally instead of being tilted vertically. Accordingly we installed two new glass beam dumps (see picture 4) to dump these reflections. The beam dumps originally foreseen to block these beams (which were supposed to be lower than the main beam – see picture 5) have been removed. There is one residual reflection which could not be dumped, as it reaches the top part of the mount of the Hartmann beam lens. A possible solution to be considered in the future would be to perform a black coating on this mount.
· We realized that the beam reflected by the waveplate that we installed last February in front of the OMC was not dumped. A glass beam dump has been added to properly block this beam (se picture 6).
· We found a beam hitting the east flange of the tower. Thanks to the help of Paolo who rotated the NI CP in TY, we could confirm that this beam is a reflection from the NI CP. The NI CP position was then adjusted in such a way that the beam is no longer sent to the tower wall, but instead is being dumped on the B1/B5 diaphragm.
· Finally a ghost beam which was hitting one of the edge of the dichroic mirror mount was blocked by adding an extra glass beam dump (see picture 7). We do not know from where this beam is coming from, it is not moving when moving NI CP, WI CP nor SR in Ty.
Note that on the M2 parabolic mirror we visualized 3 spots: the main spot near the center of the mirror which should be the main beam hitting M2, another spot located at the bottom of the mirror, which we assumed to be the B5 beam, and another spot which we can see at the bottom left of the M2 mirror and which is in fact an image of the beam hitting the dichroic mirror.
In addition to addressing the issues mentioned above, we also installed a beam dump (see drawing 1) to block the beam which is supposed to be reflected by the B5 minilink viewport (but we could not see this beam), and we installed a beam dump inside the SQZ pipe (see drawing 2) to block the reflection from the SQZ mini-link viewport.
During the investigations of scattered light we broke one of the bench LVDT wire, which was repaired by Fabio (many thanks to him!).
After the installation of all these beam dumps, we removed some ballast mass attached below the bench. The total bench weight has increased by about 80 g.
The bench was then suspended with the help of Paolo and rebalanced.
* OMC bridge changed to allow birefrigence tuning with additional side screws
* obtained 0.75e-3 polarization mismatch without using the side screws
* obtained 98% OMC2 throughput with a coarse alignment and mode matching between the two OMCs
* the OMC1/OMC2 resonant mode seems to have 7e-3 of P-polarization
* the OMC PZTs are now tightened at the nominal 20cNm instead of a few cNm
=> should allow faster lock acquisition but increases coupling of PZT driving electronic noise (it was a factor 30 below h(t) despite a large offset on the OMC1 locking point)
* results may change after going into vacuum and fine alignment
To tune more finely the birefrigence of the OMCs we have prepared new
bridges above the OMC. Instead of having one hole for tightening the
PZT mounted on top of the OMC with a screw. The new bridges have three
holes. One for the PZT screw, and two holes for screws compensating
the briefrigence caused by the PZT screw.
To land SDB1 on the safety bolts we have lifted the nuts on the bolts
all the way to the top of the blot to prevent the bolts from falling
into the safety catch holes that are not exactly well aligned with the
controlled position of the bench (by ~0.5mm). We then lift the bolts
till they lightly touched the bench, and then we put weights on top of
the bench, and screwed additional weights underneath the bench to
block it. We then used BS to fine align the direct NI reflection beam
on OMC1.
To change the bridges we have removed the OMCs from the support block
and left them on SDB1. We unscrewed the whole OMC support block and
took it to the clean room. We put chocks (clamps) to mark the position
of the support bock before removing it. To remove the bridge we need
to remove the copper plate below. At that point we noticed that unlike
the spare setup at LAPP the PZT wires are going through the screw hole
in the middle of the copper plate which we wanted to use for the
bridge instead of a dedicated small cable hole (see figure 1).
We thank Vincenzo for lending us a soldering iron and flux free solder to
unsolder the OMC PZTs, change holes used for the PZT wires and
resolder the PZT. We also changed the kapton insulation around the
PZTs. After that we could mount the new bridges. To be sure to have a
good thermal contact we have changed the indium sheets on both sides
of the Peltier cells and underneath the OMCs. On one of the Peltier
cells on one side the indium sheet was stuck (the Peltier cell was
stuck to the copper plate by the indium sheet), so we left it.
We then checked if the new black coated OMC covers fit the copper
support. They did not. We measured them to be 0.2mm more narrow than
the old OMC covers, so they did not fit onto the copper support
plate. We gave them to the LAPP mechanical team that was on site to
file the bottom 4mm of the covers by 0.2mm of material on the inner
side around the bottom of the OMC covers.
Then we installed back the OMC support block on SDB1. While removing
the temporary chocks (clamps) we lost a ~10mm long M6 screw and a
washer inside the bench. It fell through a ~2cm diameter hole that was
designed ~20 years go to pass a beam underneath SDB1 with a
periscope. Note that is no longer possible, as the bottom plate of the
bench has been changed and the corresponding holes have been
forgotten. This free screw should not be a problem for balancing the
bench. During the suspended bench alignement recovery the bench has
been shaken by local controls many times and the balancing did not
change.
Afterwards we put the OMCs on the support, tightened the PZT screw
with a torque of 20cNm and put one screw barely touching the OMC in
the side hole of each OMC bridge in preparation for birefrigence
tuning. We then aligned the OMC1 and locked it using the B1s1
photodiode. Figure 2 shows the power on B1s2 and B1s2P, there is also
a ratio of the two photodiode, that shows 0.02. Given that B1s2 sees
only 8% of the power, this correspond to 1.6e-3 of P-polarization in
transmission of OMC1. This was surprisingly good, we spend some time
wondering if we are looking at ghost beam on B1s2P, but we didn't find
any brighter beams.
Afterwards we reduced the power on SDB1, by dumping 90% of the power on
the squeezing bench using the Faraday isolator (we installed a beam
dump on the squeezing bench on Monday morning and left it there), and
locked OMC2. Figure 3 shows the PD powers, in particular the ratio of
power between B1s2P and B1_PD2 was 0.006, given that PD2 sees only
half of the power this corresponds to 3e-3 of light rejected by OMC2
in P-polarization.
At that time we have also seen that the error signal on OMC2 was 3
orders of magnitude smaller than for OMC1 for the same PZT
modulation. We went inside the tower and put the modulation frequency
at ~2.5kHz. We could hear clearly the PZT on OMC1 but not on OMC2. We
removed the OMC2 PZT screw and pressed on the PZT with a metal
tweezers handle. At the second attempt we could hear the OMC2 PZT
modulation. Which pointed to a bad mechanical contact and not a bad
soldering. We put back the OMC2 PZT, removed the 5mm longer side screw
and used it to tighten the PZT. The new bridges might be a hundred of
microns taller than the old ones.
After this we continued with the birefrigence tuning. First locking
only OMC1. We tightened the side screw by 5cNm. This degraded the
birefrigence by a factor 40, B1s2P/B1s2 ratio went from 0.02 to 0.8,
so 6% of P-polarization. This reassured us that we were actually
having a very good birefrigence tuning. We removed completely the side
screw of OMC1. The result is shown on figure 4, the B1s2P/B1s2 dropped
to 0.09, so 7e-3 of P-polarization.
As we were running out of time, we moved on and locked OMC2. Figure 5
shows the result, the B1s2P/B1p_PD2 ratio is 1.5e-3, which means
0.75e-3 of P-polarization rejected by OMC2. Very satisfactory, the
removal of the barely touching screws might be the explanation of the
improvement. Also on figure 5, there is 0.015mW on B1s2_PD1 and
0.007mW on B1s2P_PD2, this corresponds to 0.015*12 + 0.007 = 0.187mW
of power rejected by OMC2, while there is ~5mW on B1_PD2, so 10mW
passing through OMC2 and a throughput slightly above 98%. This is
confirmed by comparing B1s2 on figure 4 and 5 (which are separeted by
a few minutes), the power drops from 0.6mW to 0.015mW, so only ~2.5%
of the power remaining in reflection of OMC2.
In conclusion the resonant mode of OMC1 and OMC2 seems well
polarization matched, with a difference of 0.75e-3. In the past we
have seen that quantity to degrade by a factor 2-3 when fine aligning the
two OMCs. Lets hope that after going to vacuum and fine alignment it
will not degrade by more than a factor few. This common mode has 7e-3
of P-polarization, which will probably result in a ~1% loss at the
OMC1 input. In addition there is 2% of s-polarized light loss between
the two OMCs, some of it could be due to coarse alignment and mode
matching, some to RF sidebands.
There is a motorized lambda plate to tune the polarization impinging
on OMC1 and remove this 1% loss, but it is not connected. After O3
additional cabling for the Faraday and this plate is foreseen. Before
O3 it should be possible to tune it by opening the detection tower and
temporarily disconnecting one of the picomotors.
Note that for all of this work the light resonating in the OMCs is
fluctuating by a factor 3 due to beam alignment fluctuation caused by
the nitrogen flow and the clean air flow in the tower. So it was
impossible to do a good alignment tuning, and everything needs to be
confirmed in vacuum with a good alignment.
After this tuning, we put the OMC covers that have been filed in the
meantime and checked that it didn't change the polarization
tuning. For OMC2, the cover wouldn't fully go in, the
new bridge seems slightly to tall by ~0.5mm. This would also explain why the PZT
screw became too short. We expect the cover is just sitting on top of
the bridge, and it is in contact in a few points at the bottom around
the copper plate. We left Irene a spare uncoated OMC cover, so its
mechanical resonances can be measured in case we see new bumps in the
h(t) spectrum.
Figure 6, 7 and 8 show the OMCs at the end of the work.
As planned we entered in the IB tower to install a baffle around the RFC minilink input port (in IB tower) (picture 1 and 2).
We took benefit of this intervention to adjust a few things:
- We have moved a bit the SiC baffle on SIB1 which protect one suspension wire of SIB1to avoid clipping on the IMC_REFL beam.
- We installed a long baffle on the SIB1 south leg in order to dump properly the beam reflected off the IB tower input window (we forgot to reinstall the baffle when we integrated SIB1 bench in 2014) (see picture 3).
We made an inspection in the tower to check that nothing was touching. No problem was found neither at the level of the marionette nor at the level of the bench itself.
At the end, the bench balancing has been checked.
We left the PMC cavity scanning for the week-end and the beam blocked on the Laser bench. The EIB has been suspended again and the controls have been closed.
We would like to thank to the EGO mechanics team, A. Chiummo and Padova's group (JP Zendri et al) for the preparation of the baffling system.
This integration in VPM has been done via a generic Python server (PyVPMlauncher v1r0) using the Python3 based pyserver template and able to start/stop any executable via Popen()/Popen.kill() and periodically monitoring its execution state via Popen.poll().
After some tuning effort, mostly needed to make the cWB machinery more user independent (it is now running as virgorun), the two main top cWb processes run.py (on olserver145 machine) and run_ts.py (on submit1 machine) can now be managed from the Low Latency Analysis VMP instance (Fig. 1).
Further levels of integration could be studied for cWB but this fast solution has allowed to quickly integrate in VPM applications developed for a different environment without making changes into them.
More efforts are also needed in order to make the cWB software installation and configuration more "Cascina compliant" and this will be carried out in view of the September OPA challenge.
To be noted that the PyVPMlauncher application is completely generic and could be used for other similar needs of integrating external applications in VPM.
Today several activities went on in parallel:
- N.Baldocchi performed the mainanance of overhead-traveling crane in the MC
- DET tower closed and started to make the vacuum
- E.Genin, A.Magazzu and G.Pillant worked on the IB
- Venting of IB and MC towers
- Installation of rolling shutters in front of TCS benches (TCS).
activities still in progress
Before the IB tower venting the PMC has been let scanned at 4 Hz (plot 3)
I took profit to assess the TEM01 & TEM02 contribution to the neoVAN beam.
Better than the "rough" alignment attempt of log entry 42043 this should say more preciselly what could be the available power at the PMC transmission
- Measure at PMC_T (plots 1 & 4)
TEM01 = 10,01 % of the TEM00 (measured in transmission)
TEM02 = 2,22 % of the TEM00 (measured in transmission)
--> PMC_TRA = 61,68 W/V* 0,99 V *[ ( 1 + 0,022 + 0,1001 ] = 68,57 W
(61,68 W/V is the calibration of the signal PMC_TRA_DC from the PMC diagnobox, see 41060)
- Measure at PMC_R (plots 1 & 4)
TEM00 = 2,4972 V / 3,215 V = 77,67 % of the overallreflectedpower (measuredin reflection)
TEM01 = 7,90% of the overallreflectedpower (measuredin reflection)
TEM02 = 1,43% of the overallreflectedpower (measuredin reflection)
--> Modal Content = 87,0 %
- Piezo sensitivity (plot 2)
1 PMC FSR is scanned with 0,2607 V read at PZT_Monit (which is 1/20 of the voltage on the piezo)
--> S_pzt = 35,96 MHz / V
FSR = c/1,6 m ~ 187,5 MHz
The next step will be the He-leak test of:
_ DT: the SQZ viewport assembly (DN250)just redone
_ MC: the newly added flanged joints: 2 x DN300mm + 3 x DN250mm
After input power increase to 25W, PDs seems to be saturated.
I checked what sideband powers are high at B1p, B2, and B4 photodiodes at different MICH offsets.
Summary:
- Sideband behaviour at B2 looks reproducable.
- Sideband power at B1p and B4 fluctuates between locks, especially when MICH offset is 0.2 to 0.0. Maybe this is from different alignment conditions, which result in the different sideband power build-up for different modulation frequencies (see, also lobgook #42011 (6MHz decay) and #41817 (56MHz decay)).
- B4_DC decays at dark fringe quite rapidly (see also logbook #42058).
Possible solution:
If my understanding of the lock sequence is correct......
- For B1p, we can notch 12MHz and 2MHz since we are not using these at B1p.
- For B4, it's hard to notch because we are using 12MHz (for sideband power monitor), 56MHz (for SSFS). We can notch 2MHz. We can also try reducing modulation depth of 6MHz and 56MHz.
- For B2, we can notch 16MHz. We can also try reducing modulation depth of 8MHz and 56MHz.
Detailed results:
DC power and RF power at different MICH offsets for 3 lock sequences with different conditions are listed below.
For each lock sequence, DC power evolution and modulation depth change with MICH offset change, and spectra of RF PD signals are attached.
In the spectra, color corresponds MICH offsets as;
- 0.7: red
- 0.5: yellow
- 0.3: green
- 0.2: cyan
- 0.1: blue
- 0.0: magenta
- no light: black (taken this morning)
From gps = 1214554740 (2018-07-02 08:18:42 UTC) Figure of DC signals, Figure of RF PD spectra
(original 25 W, did not reached DF)
DQ_META_ITF_State 103. 105. 107. 110. 112.
LSC_MICH_SET 0.70 0.50 0.30 0.20 0.10
LSC_B1p_DC_mean 1.85 2.93 4.80 6.46 8.78
LSC_B2_DC_mean 17.36 15.55 12.70 10.14 5.64
LSC_B4_DC_mean 0.08 0.28 1.07 2.46 7.53
DAQ_LNFS_6MHz_mag_mean 0.57 0.57 0.57 0.28 0.28 (reduced towards dark fringe)
DAQ_LNFS_8MHz_mag_mean 1.10 1.10 1.10 1.10 1.10
DAQ_LNFS_56MHz_mag_mean 0.31 0.31 0.31 0.31 0.31
B1p_PD2 highest freq 2MHz 12MHz 12MHz 6MHz 6MHz
B1p_PD2 highest mag 3e-4 9e-4 1e-3 1e-3 2e-3 [mW/rtHz]
B1p_PD2 2nd high freq 12MHz 6MHz 6MHz 12MHz 56MHz
B1p_PD2 2nd high mag 2e-4 6e-4 9e-4 4e-4 1e-3 [mW/rtHz]
B1p_PD2 3rd high freq 14MHz 2MHz 2MHz 2MHz 12MHz
B1p_PD2 3rd high mag 2e-4 5e-4 5e-4 2e-4 4e-4 [mW/rtHz]
(mostly same as MICH offset reduction starting from gps = 1214556256 below, but different at 0.2-0.1 offset)
B4_PD2 highest freq 2MHz 12MHz 12MHz 56MHz 56MHz
B4_PD2 highest mag 1e-5 9e-5 2e-4 4e-4 5e-4 [mW/rtHz]
B4_PD2 2nd high freq 14MHz 56MHz 56MHz 12MHz 12MHz
B4_PD2 2nd high mag 1e-5 7e-5 2e-4 1e-4 4e-4 [mW/rtHz]
B4_PD2 3rd high freq 12MHz 2MHz 2MHz 2MHz 50MHz
B4_PD2 3rd high mag 1e-5 5e-5 9e-5 7e-5 1e-4 [mW/rtHz]
(mostly same as MICH offset reduction starting from gps = 1214556256 below)
B2_PD2 highest freq 6MHz 6MHz 6MHz 56MHz 16MHz
B2_PD2 highest mag 2e-5 1e-3 1e-3 1e-3 1e-3 [mW/rtHz]
B2_PD2 2nd high freq 2MHz 56MHz 56MHz 12MHz 2MHz
B2_PD2 2nd high mag 1e-5 9e-4 1e-3 1e-3 6e-4 [mW/rtHz]
B2_PD2 3rd high freq 14MHz 12MHz 12MHz 16MHz 14MHz
B2_PD2 3rd high mag 1e-5 7e-4 7e-4 7e-4 5e-4 [mW/rtHz]
(mostly same as the MICH offset reduction starting from gps = 1214556256 below)
From gps = 1214556256 (2018-07-02 08:43:58 UTC) Figure of DC signals, Figure of RF PD spectra
(after B1p saturation fixed)
DQ_META_ITF_State 103. 105. 107. 110. 112. 120.
LSC_MICH_SET 0.70 0.50 0.30 0.20 0.10 0.00
LSC_B1p_DC_mean 1.85 2.93 4.80 6.51 8.86 0.25
LSC_B2_DC_mean 17.44 15.81 12.85 10.10 5.64 2.88
LSC_B4_DC_mean 0.08 0.28 1.07 2.48 7.60 44.37
DAQ_LNFS_6MHz_mag_mean 0.57 0.57 0.57 0.28 0.28 0.03 (reduced towards dark fringe)
DAQ_LNFS_8MHz_mag_mean 1.10 1.10 1.10 1.10 1.10 1.10
DAQ_LNFS_56MHz_mag_mean 0.31 0.31 0.31 0.31 0.31 0.31
B1p_PD2 highest freq 12MHz 12MHz 12MHz 56MHz 56MHz 8MHz
B1p_PD2 highest mag 7e-4 9e-4 1e-3 4e-4 5e-4 5e-5 [mW/rtHz]
B1p_PD2 2nd high freq 6MHz 2MHz 6MHz 12MHz 12MHz 112MHz
B1p_PD2 2nd high mag 6e-4 5e-4 5e-4 4e-4 5e-4 9e-6 [mW/rtHz]
B1p_PD2 3rd high freq 2MHz 6MHz 2MHz 6MHz 8MHz 56MHz
B1p_PD2 3rd high mag 5e-4 4e-4 5e-4 3e-4 3e-4 4e-6 [mW/rtHz]
(12MHz at 0.3 offset is highest, 2MHz is also high)
B4_PD2 highest freq 12MHz 12MHz 12MHz 56MHz 56MHz 8MHz
B4_PD2 highest mag 3e-5 9e-5 2e-4 2e-4 7e-4 1e-4 [mW/rtHz]
B4_PD2 2nd high freq 2MHz 56MHz 56MHz 12MHz 12MHz 16MHz
B4_PD2 2nd high mag 3e-5 6e-5 2e-4 1e-4 2e-4 1e-4 [mW/rtHz]
B4_PD2 3rd high freq 14MHz 2MHz 2MHz 2MHz 2MHz 48MHz
B4_PD2 3rd high mag 2e-5 5e-5 9e-5 7e-5 1e-4 2e-5 [mW/rtHz]
(56MHz at 0.1 offset is highest, 12MHz is also high)
B2_PD2 highest freq 6MHz 6MHz 6MHz 56MHz 16MHz 16MHz
B2_PD2 highest mag 7e-4 1e-3 2e-3 9e-4 1e-3 2e-3 [mW/rtHz]
B2_PD2 2nd high freq 12MHz 56MHz 56MHz 12MHz 56MHz 48MHz
B2_PD2 2nd high mag 5e-4 8e-4 1e-3 7e-4 9e-4 1e-3 [mW/rtHz]
B2_PD2 3rd high freq 2MHz 12MHz 12MHz 6MHz 2MHz 64MHz
B2_PD2 3rd high mag 4e-4 6e-4 7e-4 6e-4 7e-4 8e-4 [mW/rtHz]
(16MHz at dark fringe is highest, 56MHz and 56+/-8MHz are also high)
gps = 1214578932 (2018-07-02 15:01:54 UTC) Figure of DC signals, Figure of RF PD spectra
(after decreasing the power on B2)
DQ_META_ITF_State 103. 105. 107. 110. 112. 120.
LSC_MICH_SET 0.70 0.50 0.30 0.20 0.10 0.00
LSC_B1p_DC_mean 1.87 2.97 4.87 6.50 8.78 0.49
LSC_B2_DC_mean 8.17 7.35 6.03 4.79 2.65 1.24 (~half the DC power)
LSC_B4_DC_mean 0.08 0.28 1.08 2.47 7.52 44.11
DAQ_LNFS_6MHz_mag_mean 0.57 0.57 0.57 0.28 0.28 0.02 (reduced towards dark fringe)
DAQ_LNFS_8MHz_mag_mean 1.10 1.10 1.10 1.10 1.10 1.10
DAQ_LNFS_56MHz_mag_mean 0.31 0.31 0.31 0.31 0.31 0.31
B1p_PD2 highest freq 12MHz 12MHz 12MHz 12MHz 56MHz 112MHz
B1p_PD2 highest mag 7e-4 9e-4 1e-3 4e-4 2e-3 2e-5 [mW/rtHz]
B1p_PD2 2nd high freq 6MHz 2MHz 6MHz 6MHz 6MHz 8MHz
B1p_PD2 2nd high mag 7e-4 5e-4 6e-4 4e-4 1e-3 1e-5 [mW/rtHz]
B1p_PD2 3rd high freq 2MHz 6MHz 2MHz 56MHz 8MHz 6MHz
B1p_PD2 3rd high mag 5e-4 4e-4 4e-4 2e-4 3e-4 9e-6 [mW/rtHz]
(mostly same as MICH offset reduction starting from gps = 1214556256 above, but different at 0.2-0.0 offset)
B4_PD2 highest freq 12MHz 12MHz 12MHz 56MHz 12MHz 16MHz
B4_PD2 highest mag 3e-5 8e-5 2e-4 3e-4 5e-4 1e-4 [mW/rtHz]
B4_PD2 2nd high freq 2MHz 56MHz 56MHz 12MHz 48MHz 8MHz
B4_PD2 2nd high mag 3e-5 6e-5 2e-4 1e-4 1e-4 4e-5 [mW/rtHz]
B4_PD2 3rd high freq 14MHz 2MHz 2MHz 2MHz 56MHz 48MHz
B4_PD2 3rd high mag 2e-5 5e-5 9e-5 7e-5 1e-4 3e-5 [mW/rtHz]
(mostly same as MICH offset reduction starting from gps = 1214556256 above, but different at 0.2-0.0 offset)
B2_PD2 highest freq 6MHz 6MHz 6MHz 56MHz 16MHz 16MHz
B2_PD2 highest mag 3e-4 6e-4 6e-4 4e-4 5e-4 1e-3 [mW/rtHz]
B2_PD2 2nd high freq 12MHz 56MHz 56MHz 12MHz 2MHz 48MHz
B2_PD2 2nd high mag 3e-4 4e-4 5e-4 3e-4 3e-4 3e-4 [mW/rtHz]
B2_PD2 3rd high freq 56MHz 12MHz 12MHz 6MHz 14MHz 64MHz
B2_PD2 3rd high mag 3e-4 3e-4 4e-4 3e-4 3e-4 2e-4 [mW/rtHz]
(mostly half the MICH offset reduction starting from gps = 1214556256 above, as expected)
Michal noticed that the spectrum of B2 6MHz which is not flat at high frequencies, suggests that the signal does not reach the sensing noise but still contains information. Making the coherence between the B2 8MHz (which is used for correcting the frequency noise since it has better SNR) and the B2 6MHz shows that at low frequencies and at high frequencies there are coherence between both, even though not at all bandwidths (Figure 1).
Figure 2 shows both the B2 6MHz and 8MHz error signal superposed. Notices that the B2 8MHz has a SNR for the SSFS of ~ 145, less than B2 6MHz, suggesting that with the 6MHz at a normal modulation depth the B2 6MHz error signal would be better than the 8 one.
Everything points towards the B2 6MHz as a promising error signal.
From Wednesday 11th of July around 13:30 UTC to Friday 13th of July 10:00 UTC, PCal on WE and NE have been installed.
The set-up on WE have been fully re-installed since we had dismounted it to make various tests at LAPP. A new metal plate more robust has been added to the set-up in order to prealign the collimator with the beamsplitter polarizing cube and the new mirror (BSX11) for the injection.
Another mirror BSX11 on the injection bench has been set in order to reduce the power incoming on the photodiode.
On NE, the set-up was already installed but we made a few changes. The metal plate has been replaced also and we added the beamsplitter polarizing cube and two BSX11 mirrors as on WE. The set-up has also been realigned.
Attached, pictures of the optical benches for both PCals and the image of the WE and NE cam where the spot of the laser can be seen plus a bigger spot likely coming from diffused light in the tower.
Pre-measurements of calibration for the lasers and the photodiodes has been made with a thermopile powermeter. The measurements were done both on the injection and on the reflection benches on WE and NE and will soon be analysed.
Further measurements for the calibration of the PCals will be made in the next months with a new integrating sphere from Newport much less sensitive on the orientation of the input port with respect to the laser beam and a better accuracy on the measurement of the power.
parallel activity:
-WE photon calibrator installation
-NE newtonian calibrator installation
-inf
at 19:50utc I changed the detection area UTA DET from "Portata Nominale" to "Portata Ridotta".
ITF found unlocked, the shift was mainly dedicated to the DET Team activities; still in progress.
Also, other works carried out and communicated to the Control Room were the Beam Cranes Maintenance inside the experimental buildings and Oxygen Sensor Maintenance at WE Building.
INF
At 6:27 UTC the EE Room Eurotherm box was restarted because of missing data.
ACS
7:01 UTC, under the request of R. Goauty, the air flux of UTA DET was switched to "Portata Nominale" to allow activities in the laboratory.
VPM
ParticleCounterWAB crashed at 13:10 UTC, process properly restarted.
I have taken a look to the two days of data with the 6MHz on also in Dark Fringe. We let the 6MHz at 0dBm of modulatio depth.
First interesting thing is that for B2 6MHz error signal MICH and SSFS are not separated exactly by 90deg but by 50deg. (for B4 56MHz they are separated by 85deg). However, the loss of SNR for MICH if we use the demodulation phase optimal for the SSFS is only of 10%. If we compare the SNR of both error signals we have (see Figure 1 and 2):
| B2 6MHz | B4 56MHz | |
| SSFS | 156.4 | 666.7 |
| MICH | 78.9 | 355.6 |
The difference is of a factor 4, which means that both error signals are comparable for a modulation depth of 12dBm. Notice that these measurements were done for 3mW in Dark Fringe, so there were non-linearities on the RF channel at the moment of the measurement.
Michal noticed that the spectrum of B2 6MHz which is not flat at high frequencies, suggests that the signal does not reach the sensing noise but still contains information. Making the coherence between the B2 8MHz (which is used for correcting the frequency noise since it has better SNR) and the B2 6MHz shows that at low frequencies and at high frequencies there are coherence between both, even though not at all bandwidths (Figure 1).
Figure 2 shows both the B2 6MHz and 8MHz error signal superposed. Notices that the B2 8MHz has a SNR for the SSFS of ~ 145, less than B2 6MHz, suggesting that with the 6MHz at a normal modulation depth the B2 6MHz error signal would be better than the 8 one.
Everything points towards the B2 6MHz as a promising error signal.
14:00 UTC ITF not locked.
The planned activities went on without major problem for all the shift. 21:00 UTC DET crew still working in DetLab.
19:00 UTC, under the request of Michimura (according with the DET crew), I lock ITF in SSFS step. This operation required a realignment of BS for ~90 URad in TX and ~20 Urad in TY.
19:30 UTC, under the request of DET crew, I misaligned W Arm and NE.
20:30 UTC activities concluded. ITF left unlocked in this configuration: NI aligned, W Arm and NE misaligned.
20:30 UTC Commissioning Mode stopped.
ACS
20:45 UTC I changed the UTA DET air flux from Portata Nominale to Portata Ridotta.
DMS - ACS
INF_WE_HEATER_TE_OUT flag - changed thresholds.
INF_TB_HEATER_PRES_OUT flag shalved under the request of the expert.
VPM
15:00 UTC ENV_DETR_DUST_0P7UM signal added on EnvMoni.
17:17, 20:01 UTC FbmPyAccess crashed / restarted.
At 15:00 UTC I added ENV_DETR..DUST_0P7UM channel in VPM -> EnvMoni.
Now it's monitored in DMS -> DET_Area.
- mod cleaner building lights maintenance and upgrade: started at 6:15utc, in progress...
- O2 sensor maintenance: north end building from 8:15utc to 12:05utc; central building started at 12:10utc, in progress...
- detection bench activity: started at 6:45utc, first part of the work with the itf locked in PRITF_MICH_OFFSET_0_5 state; then with only the NI mirror aligned, in progress...
-inf
to allow the work in DET LAB the UTA was set in "portata nominale" at 8:35utc and it is still running in this condition
In order to monitor the SDB1-SQZ viewport replacement activities the DET particle counter has been reactivated including data collection (Fig. 1).
Today the whole shift was dedicated to the work on SBD1 Scattered light mitigation. The activities went on without problems. ITF left in Recombined.
Vpm
15.07 UTC FbmMainUsers restarted after a crash
ITF Status
21.00 UTC Commissioning mode stopped
ITF found locked in LOCKED_SSFS, Maintenance mode started at 6:07 UTC to allow activities inside the Buildings.
The shift was mainly dedicated to SBD1 Scattered light mitigation, carried out by DET Team.
List of maintenance activities communicated to the Control Room:
- Cryotraps refill;
- Cleaning operation in Central Building and Tunnel Mode Cleaner;
- Preparation works of CB A/C pipe 3-way valve for replacement;
- Filming Crew in Central Building followed by F. Richard.
Maintenance mode ended at 10:24 UTC, activities inside the SBD1 Tower still in progress.
VPM
ParseSeismonProcessing crashed at 10:37 UTC, process properly restarted.
FbmPyAccess crashed at 11:10 UTC, process properly restarted.
VacuumMoni restarted at 11:30 UTC to adjust the threshold.
TCS
Check of the TCS chillers water level.
The activity on SDB1 inside the tower continued all the shift until 20:00 UTC, when I stopped the Commissioning Mode.
ITF left in Locked SSFS for the night.
Nothing else to report.
06:00 UTC ITF not locked.
Upon arrival I found IMC unlocked. E. Genin relocked and restored the standard state of Injection System.
Commissioning Mode set at 06:16 UTC.
In order to allow the planned activity on SBD1 Scattered light mitigation inside SDB1 Tower (carried out by Gouaty and Bonnand) with Casanueva we realigned cavities and relock ITF at PRITF_MICH_OFFSET_0_2 but ITF was very unstable. It unlocked several times.
According to the DET crew, we decided to work with ITF locked at PRITF_MICH_OFFSET_0_5. ITF much more stable.
Activity still in progress.
Vacuum
06:30 UTC SDB1 Tower Lower part opened.
DMS red flags
-
Detection
SDB1_IP and SDB1_Vert -> red flags due to the intervention on SDB1. -
Suspensions
SR_Vert -> red flag due to the thermal transient after the SDB1 tower opening. -
Vacuum
CleanAir -> red flag due to the air flux inside SDB1 Tower.
LargeValves -> red flag due to the valves closed at DET cryolink.
CompressedAir -> red flag due to the morning intervention on TB compressed air machine. -
Environment
CB_Hall -> red flag due to the acoustic noise generated by the clean airflux machine.
TCS_zones -> red flag due to the acoustic noise generated by the clean airflux machine. -
Infrastructure
ACS_WAB -> red flag due to the ongoing intervention on WAB ACS machine.
ACS_TB -> red flag due to the morning intervention on TB compressed air machine.