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Section: H1
Task: COC
Maybe this isn't the best place to share this, but life can be frustrating as a deuteranope. Matplotlib has an easy to use colorblind friendly style built in. It can be invoked by adding the line plt.style.use('tableau-colorblind10') before starting to setup your plot (if you've used the usual import matplotlib.pyplot as plt). Maybe this is common knowledge, but I just found it while working on a script.
The first plot is one of the plots produced for the weekly CPS noise monitoring famis for ITMX. The second plt is the same one, but I added the colorblind style to the script. For me, on the first image the H3 and V1 sensors on both subplots are almost the same color. It's especially difficult to go between the legend and the traces on the first plot. Reading these plots on a backlit monitor make this even harder. More than a 4-6 traces, I have a really hard time telling which line is which.
On the second figure, it's much easier. Add in some different linestyles and thicknesses, and everybody's pretty plots can be appreciated by more people.
Nice one! Tagging all the groups, so some folks get emails about this dueteranope-approved color palate. Now we just need the equivalent for matlab!
Today, Travis and I pulled the ITMX-HR FIrstContact cleaning layer and inspected. With bright light it was difficult to find many particulates in the main area of the center of the optic which was good. We fully suspended the 8 locked QUAD masses and returned the ACB back to it's nominal position (removed locking bracket and wedge). We then inspected the ITMX OPLEV laser transmitter and receiver beam with respect to the new nozzle baffles, and also check to confirm that for this ITM, the optical lever readback SUM is the same as it was before the locking episode. So all good there. A few quick TFs identified that I left a stop rubbing on the CP top barrel which Travis found, but the TFs look better now. Wafers are down in the chamber and we swept for tools, etc.
Nidhi is finishing the ITMY SUS TFs.
Jim is going to try to run ISI TFS of ITMX, ITMY, and the BS tonight.
Today, Travis peeled the BS FirstContact cleaning layers he applied last week. (We had to feed the N2 Top Gun and hose through the side of the HAM3 East door since that door was off.) Upon inspection, Travis found that there was some leftover FC streaks at around the 10 o'clock position on the AR surface of the optic, so he had to reapply the FC brush-on layer. The HR surface appeared clean. A few hours and a meeting later, we repeated the removal process, this time yielding a clean looking AR surface.
We unlocked the suspension, added the toilet seat shaped AR and HR baffles back onto the suspension cage, took a few pictures, pulled all tools from the chamber and exited. We redamped/untripped the ISI and BS SUS from the control room. The BS is not back to the nominal ALIGNED guardian state. HAM3 was still damped even though we were in the vicinity.
The first picture attached is the view of BS-AR from the SR3 perspective, showing how the gold barrel wire protection baffle on the left side is now less in the beam path than previously (recall it was cut per a new revision of the drawing and reinstalled). The second is the BS-AR as viewed from ITMX, again showing that the sharp edges of the right side baffle have been cut back per the drawing.
https://dcc.ligo.org/DocDB/0148/E1700418/001/BS%20WIRE%20BAFFLE%20MODS%20DETAILS.PDF
In prep for closeout of the BSC corner chambers, Camilla assisted me in applying First contact to the ITMY HR surface today.
We used the tooling bracket and wedge to push the ACB out of the way and we painted the cleaning layer onto the surface. It was decided to perform the painting application as opposed to the spray application, after Calum and I quickly l reviewed procedures again this afternoon. As well, the surface did not seem terribly dirty since there has been very minimal activity in this chamber, 0-5 particles per square inch.
Camilla also took note of the particle counts from the monitor very near the door, which were all around 20 and 40 or less during entry and exit of the chamber.
As Patrick recorded in his summary from yesterday, we have put the ITMY in the SAFE Guardian state and then removed many of the OSEMs. So, ignore any error signals from th ITMY SUS. (Recall the BSC1 HEPI and ISI are locked so those states are also now static.)
Yesterday, Travis and I got so far as to lock all of the masses and muscling through the removal of most of the hardware on the QUAD needed in prep to remove the lower structure (and lowest 6) masses of the ITMY QUAD. We plan to do the deinstall with the arm on Monday. We noted a fair amount of metal particulate on the bottom of our shoe covers each time we exited the chamber.
Prior to disassembly, Travis marched down to the ITMY Optical Lever receiving viewport and double checked our previous mapping. Namely, with bias enabled for the main and reaction chain, the ITMY-HR beam is ~centered on the OPLEV diode (as confirmed by Kissel's trends yesterday) and the ITMY-AR overlaps the CP-HR very well. I'll add the sketch soon.
Pictures attached are 1) ITMy pre-disassembly, 2) disassembly in process (ACB swung back, floor planks removed, sleeve removed) and 3) ITMy bit naked and ready for arm-assist removal.
For the record, the new ITMY optic (ITM01) was weighed after the ears were bonded and comes in at: 39,611g
Gerardo and I, with Rahul in training, bonded PUM ear S1201472 to the test mass ITM01 S3 flat. (Yes, a PUM ear on a test mass - this was deemed acceptable in times of short test mass ear supply.) The bonding was straight forward and placed with 0.04mm measured error along the beam path axis (0.1mm is the tolerance).
Note this was the first bond in the new lab space. All systems up and working well, thanks to Bubba/Tyler/Chris and the many hours Travis spent to help move everything.
The second ear bonding session is scheduled for next week.
Late entry - ITM01 had the second ear bonded on March 4th, 2020.
A PUM ear was again used. Ear - S1201484
During the bond, there was initially a set of bubbles which we watched migrate out over the course of a few hours. At 2 hours the location and bubble situation (very minimal) were well within tolerance.
The optic will be FirstContact cleaned and stowed in the coming week.
4 hours 48 mimutes 26 seconds later, H1 is still locked, and GPS time rolls over to 1260000000.
Very nice!
Managed to finish the OPLEV charge measurements today during the maintenance downtime, for both the ends (ETMX and ETMY). The results are attached below. The effective bias voltage for both ETMX and ETMY this week has been mostly below 40 V (except for ETMY yaw which is now 50V). The long term trend is on the rise for some of the quadrant, however we still don't need to flip the sign yet.
After the measurements were taken, all the values were restored to it's orignal and SDF differences have been removed (expect for optical align offset for pitch and yaw for both ETMX and ETMY which is still flagged, maybe operators can accept the difference if required).
At the start, I clarify that these above measurements that Rahul regularly takes are measures of *absolute* *angular* actuation strength of each ETM ESD system, in terms of effective bias voltage in Volts on the ESD bias electrode (i.e. an imagined *extra* bias voltage on top of the regularly *requested* bias voltage [think ~100s of Volts] that would bring this absolute angular actuation strength to *zero* when the requested voltage is set to zero).
I re-clarify all this terminology because conversations are happening about whether we'll need to
- launch a Test Mass Discharge System campaign any time soon,
- begin alternating the requested bias voltage
- do nothing
during O3.
I answer the question with additional plots of another, different metric of the charge accumulated: the *change* in *relative* *longitudinal* actuation strength for the ESD system on ETMX (alone) between
- April 18th 2019 (during O3, after we think we finally got the calibration tracking system right),
- May 18th 2019, and
- June 18th 2019.
Remember that the *absolute* *longitudinal* actuation strength for the ESD was measured to be 4.739e-12 N/ct by the calibration group on Mar 28th 2019 (see LHO aLOG 47941), and this relative longitudinal actuation strength is with respect to that. Note, you can find these plots on any day, readily made under the "CAL > Time Varying Factors" tab of the individual IFO summary pages, and these are plots of the real part of the "\kappa_TST" factor (e.g.
Attached below are images of the HR surfaces of the H1 ITMs with IR light resonating in the arms (19.7 W of 1064 nm laser light).
They were captured by Jeff Bartlett a few weeks ago using the "Pcal" ITM camera systems mounted on the spools at the ends of the beam tube manifolds in the LVEA, near the cryopumps.
The camera settings were:
ITM-X
#109 ISO 800, shutter 1/800
#110 ISO 800, shutter 1/400
ITM-Y
#016 ISO 400, shutter 1/500
#110 ISO 250, shutter 1/200
The assembly drawing for the camera system is LIGO-D1500073-v9.
Kentaro Mogushi's technical note regarding camera system upgrades to minimize aberrations introduced by the vacuum windows is LIGO-T1700540-v3.
Note that these are the first IR images after implementing Kentaro's upgrades. Image quality may improve slightly as the systems are adjusted.
Gabriele and I were curious as to the exact locations of the spots on these images. I played with the brightness and contrast of ITMY until I could see some fiducials of the cage structure (in this case, the EQ stops on the right hand side of the image - see first attached image). Then, I super-imposed this on an old image of ITMY from aLOG 42520 that showed the cage structure much more clearly. The results are attached:
The camera position is fixed (physically locked down), the suspension cage is also fixed, and the position of the heads of the EQ stops are well known. By using the EQ screw heads as the zero position, the location of spots on the optic face can identified. I made a conscious decision in these frames to turn down the exposure to accent the surface spots. In most the position of the EQ screw heads are visible.
Here's ITMX blended with images from aLOG 43174 and aLOG 42774
Took pictures of face of ITM-X and ITM-y under green light as the IFO unlocked while setting up. Will try to get a set of shots under IR at at least 20W before the holiday break.
There are two shots of each optic at different exposures and focus points.
| Optic | Frame # | Shutter | ISO | Focus |
|---|---|---|---|---|
| ITM-Y | 111 | 1.0 sec | 6400 | 1725 |
| 112 | 1.6 sec | 6400 | 1725 | |
| IYM-X | 110 | 3 sec | 800 | 1745 |
| 117 | 3 sec | 800 | 1625 |
to do precise image subtraction in the future (to detect small movement in the point scatterers) we would like the camera position to remain the same. It would be nice, therefore, to design a camera holding jig that would get us back to the same place w.r.t. the viewport. Would be easier to make that analysis quantitiative this way rather than do a lot of image scaling/aligning with camera at different positions.
Rana, Very good points. The camera/lens assemblies are bolted to the Viewport Camera Housing (D1500073), which allows for positioning the cameras. This assembly is attached to the viewport on the Spool Flange via the Viewport Guard Assembly (D080367). This provides a rigid and locked positioning of the cameras. The whole mounting assembly is then covered by a light and dust proof housing. The cameras are controlled, focused, and fired remotely, so there is no touching of the actual camera assembly. Unless the system is disturbed is some way the image should not shift in the frame. Also the edges of the baffles and the EQ stop mountings are present in the image, which should provide a fixed point of reference. These are just being deployed and any input to make the system more useful would be greatly appreciated.
During the low noise lock at 4:50 UTC today (Oct 11), there is a comb of lines in h(t) at 56.84 and multiples. They are quite narrow lines. The most interesting characteristic is that they have extreme amplitude modulation. The first attachment is the h(t) spectrum with the lines marked. The second shows narrow BLRMS around each of the lines. The fundamental at 56.84 Hz has a half-period of about 24 minutes. The amplitude goes very close to zero, and looks very periodic. Each multiple n has zeros in the same place, but the period is n times shorter. Maybe this could be all generated from the fundamental with the right kind of nonlinearity. I'm not sure what would give such a slow but extreme modulation - maybe some centering servo? The BRUCO results show a lot of channels at End-X coherent. Accelerometers on BSC9 seem to see it, but without amplitude modulation. PCal X sees it in the TX and RX PDs, but stronger in RX; but it doesn't seem anywhere near the level to get into h(t).
The 56.84 Hz comb is a blast from the past. Here is an entry from March 2013 concerning H2 one-arm data suggesting that the comb could be purely DAQ-related: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=5806
This one is close enough to the 57Hz ETM HWS that we've seen in the past that I thought I should mention it here. However, we've recently overhauled that system and I've not confirmed what the new frame-rate is yet.
Here's the old analysis: https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=14778
I Looked at an empty EX ADC channel (H1:PEM-EX_ADC_0_08_OUT_DQ) and found that the 58.64 Hz comb is there too, indicating that the comb comes from some source independent of the interferometer (i.e. in the DAQ or RF pick-up). I have attached ASDs of the empty ADC in 0.1mHz bins both for the entire spectrum (0-1024Hz) and near to the 14th 56.84 harmonic (~795.76Hz). I was slightly surprised that a second nearby line (that would explain the amplitude modulation) was not seen even with the 0.1mHz resolution.
Yes - the ETM HWS are running at 57Hz. This doesn't mean that this is the issue since it appears to be DAQ related, buuuut .....
aidan.brooks@zotws11:~$ caget H1:TCS-ETMX_HWS_SYNC_FREQUENCY
H1:TCS-ETMX_HWS_SYNC_FREQUENCY 57 Hz
aidan.brooks@zotws11:~$ caget H1:TCS-ETMY_HWS_SYNC_FREQUENCY
H1:TCS-ETMY_HWS_SYNC_FREQUENCY 57 Hz
I've searched EX channels and found some channels where amplitude modulation is seen: H1:SUS-ETMX_L3_DRIVEALIGN_L_OUT_DQ H1:SUS-ETMX_L3_ISCINF_L_IN1_DQ H1:SUS-ETMX_L3_LVESDAMON_LL_OUT_DQ H1:SUS-ETMX_L3_LVESDAMON_LR_OUT_DQ H1:SUS-ETMX_L3_LVESDAMON_UL_OUT_DQ H1:SUS-ETMX_L3_LVESDAMON_UR_OUT_DQ H1:SUS-ETMX_L3_MASTER_OUT_LL_DQ H1:SUS-ETMX_L3_MASTER_OUT_LR_DQ H1:SUS-ETMX_L3_MASTER_OUT_UL_DQ H1:SUS-ETMX_L3_MASTER_OUT_UR_DQ Attached plots are BLRMS and zoomed spectrum of H1:SUS-ETMX_L3_DRIVEALIGN_L_OUT_DQ as an example. The vertical line (orange, dotted) in the zoomed spectrum is at 568.404 Hz (10th harmonics).
NO
we moved the Hartmann sync frequency and the lines moved accordingly - its Hartmann, not DAQ.
Why does the Hartmann sensor so strongly couple to DARM?
With regards to the coupling, the ETM HWS are served by the same power supply as the ring heaters. It's a long shot but it might be worthwhile to try disconnecting the ring heaters from the driver while the to see if the coupling of the 57Hz to DARM is changed.
https://dcc.ligo.org/LIGO-E1100891
TVo, Georgia
Last night we powered up to 20 W before losing lock. Today TVo and I had a look at the ETM HWSs to see if we can see any thermal lensing caused by absorption. There is some absorption visible on ETMY HWS.
The first screenshot shows the PSL power [W], ETMX HWS spherical power [diopters], and ETMY HWS spherical power [diopters]. We can estimate the absorption of the optic from the circulating power, the measured thermal lens on the HWS, and the substrate and surface deformations (or lensing per unit power). A back-of-the-envelope calculation puts a first estimate of total absorption at 0.21 ppm. The absorption on ETMX is not visible above the noise.
The HWS beam passes through the substrate of the ETM, reflects off the HR surface, and passes through the substrate again. It samples the substrate lens twice and the surface lens once. So the thermal lens measured on the HWS is
L_tot [D] = (2 A_sub [D/W] + A_surf [D/W] ) * P_circ [W] * alpha
Where L_tot is the total lens in diopters, A_sub and A_surf are the substrate and surface deformations respectively in diopters per W, P_circ is the circulating power in the arms, and alpha is the optic absorption.
Going from 2 W to 15 W we see ~15 uD of thermal lens on the Hartmann. The circulating power at 15 W is ~95 kW (assuming 45 PR gain, 280 arm gain, and 50% reflectivity of the beamsplitter). The substrate and surface deformations as assumed to be 3.86e-4 D/W and -2.93e-5 D/W respectively (numbers acquired from the TCS simulation tool, not sure if they need updating with new test mass coatings).
This gives us an absorption of 0.21 ppm, which seems reasonable.
Final screenshot shows the HWS contour plots between the cold and hot ETM states.
My interpretation from the coating documentation shows that this measurement is in line with what was measured during metrology characterization circa 2015, see last page.
https://dcc.ligo.org/DocDB/0059/C1103241/001/C1103241-v1_Coating%20Characterization%20Report_ETM16.pdf
[Hang, Craig, Gabriele]
We moved PR3, PRM and the soft degrees of freedom to improve the beam centering on all four test masses and increase the recycling gain.
We started with a recycling gain of about 38.2 and finished with a recycling gain of 47.4 [+24%]
A lock loss terminated our work, so there is still some re-alignment to do to get the test masses centered. And there might be more recycling gain.
We added dithering lines in yaw to all four test masses, and we could improve the centering significantly. At the end all Y2L coefficients are zero, and the dithering signals are quite close to zero. The two ITMs are reasonably centered, as is ETMX. Instead ETMY seems to have a larger mis-centering.
If we need to put back the Y2L coefficients, we probably only need to set ETMY to about 4.
We finally lost lock after more than 6h continuous lock.
Wow, very impressive. Hiro's simulations (G1700140) gave a PRG of only 39, though that was including an ad-hoc loss per arm of 50 ppm.
This is awesome!
Our PR gain is POP_A_LF / IM4_TRANS_SUM with calibrations to take into account reflectivity branching ratios, but we're quite close to the edge of IM4 trans. I think our normalized yaw number is more than 0.8. (We haven't pico'ed yet, to keep an alignment reference, but I think it might be about time to pico and say that this is better than O2.) I'm suspicious that our PR numbers that we've been reporting might be systematically high, if the number we're dividing by is smaller than the total actual amount of power in transmission of IM4.
That said, this has been true since our vent recovery (and also to a lesser extent during O2), so the +24% is certainly real, but the absolute values we've been reporting for PR gain might be high. We should pico and check the calibrations to be sure.
Looking at TR_X_NORM and TR_Y_NORM (which are normalized so that the single arm build ups are 1, at the time of the best recycling gain the build ups were 1646 and 1732 relative to the single arm, which would indicate a recycling gain of 45. Gabriele pointed out that the reflectivity of PRM is 3.1% according to galaxy, which means that this gives a recycling gain of 53.0
Another option for estimating the circulating power would be to try this method which has been done at LLO: 36745
WOW! Amazing!! Congratulations!!
Here's a quick computation of the power recycling gain as a function of the round trip losses in the arm (in ppm, sorry I forgot the units in the plot), assuming Tprm = 3.1%.
The two marked points correspond to the values of recycling gain estimated with POP_LF and with the arm transmission.
Dark offsets for TR_X and TR_Y are not very well set. The table below shows the TR values in different configurations, and the corresponding estimated recycling gain. Taking into account the dark offsets now the X and Y arm transmission give consistent recycling gains.
| Dark | Single arm | Full IFO | Recycling gain | |
|---|---|---|---|---|
| X | 0.045 | 1.00 | 1648 | 53.5 |
| Y | -0.007 | 0.98 | 1736 | 54.5 |
The REFL_A_LF also goes up by about 5% (relative to unlocked so it measures the ifo reflectivity) as expected. Great job!
From the level of reflected power (w.r.t. the off resonance state) we can estimate again the round trip losses.
The plot below shows that the REFL level we measured after re-aligning (8.3%) corresponds to about 61 ppm round trip losses, and a recycling gain of 53.4, which is very close to the recycling gain we can estimate from the arm power buildup.
The recycling gain improvement is seen in the CARM offset reduction sequence too. I ran the script that Sheila and Gabriele posted in alog-43344 on data from yesterday (starting at t = 1220674303).
This plots the reflected power (normalised) vs the arm build up (transmission normalised to a single arm). As we step through the CARM offset reduction, the TR_X increases and the REFL_DC decreases. The slope is an indication of the power recycling gain.
As of yesterday we're going better than the previous measurements, including compared to O1.
In addition to Georgia's analysis, here is a similar plot, with also some fit lines. The new curve is again consistent with no losses in the PRC and arm round-trip losses of about 66 ppm.
With the X arm open and the green laser locked; took the following picture with the ITM-X camera. Image was shot at 1/2sec shutter speed, Moonlite focuser at 1735, and the aperture plate rotated to put aperture hole at the bottom.
Next is to look into adjusting exposure time and focus to produce a better (more informative) image of the optic face.
Tagging AWC, COC, and TCS to see if we can corroborate any of these "point" scatterers with HWS camera measurements or pre-installation COC group's characterization (i.e. E1000770)
While inspecting the HR surface during (and just) after the FirstContact pull on the ETMX HR Surface yesterday, Travis and I saw a few points within the central 6" of the optic. Pictures are attached. One feature looks more like a small sleek or scratch rather than a dot. Upon review of the "map" we made roughly a year ago when the optic was in the bonding lab (also attached), we see that many of these were there during that inspection. In conference with GariLynn this morning, she confirmed my decision to move to chamber closeout and the door has just been installed on the chamber. We will digest these pictures and compare to previously obtained coating maps and metrology data.
Note, keep in mind that it is very difficult to say much about the optic surface quality based on these photos. It is difficult to state whether such observed features will be a problem, whether they are in the coating or on top of the coating, etc. TBC...
The scratch is found in the original polishing defect report at C1205029 Scatter measured with an integrating sphere shows several high points in the center 50 mm diameter, measured scatter is 7.7 ppm at E1500336 Thanks for the great pics!
Further analysis at https://dcc.ligo.org/T1800255 No new conclusions.