For the 200W beam
Note that the peak in the ISS at ~120Hz is back indicating noise eater noise. This is odd as I had already reset the noise eater once today and it already went back into oscillation.
After talking to Jan I left the PMC heater off. The temperature is still coming to equilibrium.
[Giacomo, Deepak] Owing to the invaluable help of Deepak and the support of a lot of people on- and off-site (thanks all for searching, investigating, procuring, shipping, etc.,..), HAUX build has gone smoothly and swiftly. As of yesterday night, we have 5 complete suspensions, that you can admire in the attached pictures. If you can't see the optics, it not because they are very clean: as they were not immediately available due to needed FirstContact work, we decided that the suspensions could be completed (including wiring) without the optics, and the optics added later (procedure in which we have been forced in the past to become experts). Because of that, we didn't even put in OSEMs and magnets. Altogether this would probably amount to another 1/2 to 1 hour of work per suspension. The plan for today is probably to move the suspensions chamber-side, and then give priority to setting up electronics and cabling to exploit David Feldbaum experience (it's his last day here). After that's taken care of, we'll FC the optics, insert them and then proceed to the testing phase.
After Mike R. has transitioned to high-power operation I went ahead and aligned the FI with the CWPs, TGGs and Quartz. The straps for the magnet were not yet ready. Earlier I was not going to insert the TGGs into an unsecured magnet, however I decided that there is hardly any risk involved provided the platform is well secured in place.
To get a better CWP extinction ratio I had to get a better adjustible HWP rotator for the incoming beam. I found one in the PSL team's cabinet. With that:
| power p-pol | power in s-pol | extinction |
| 3.8 W | 19 µW | 53.0 dB |
| 50 W | 0.36 mW | 51.4 dB |
| 100 W | 0.70 mW | 51.5 dB |
| 125 W | 0.85 mW | 51.7 dB |
| 20 W | 0.12 mW | 52.2 dB |
| power p-pol | power s-pol | extinction |
| 50 W | 0.41 mW | 50.9 dB |
| 126 W | 1.0 mW | 51.0 dB |
| 100 W | 0.83 mW | 50.8 dB |
| 20 W | 0.16 mW | 51. 0 dB |
Inserted Magnet with TGG+Quartz, polarization should rotate by 90 degree, p-pol should be minimized
| power in | power s-pol | power p-pol | extinction |
| 8.99 W | 8.92 W | 0.42 mW | 43.3 dB |
Inserted the 2nd TGGs
| power in | power s-pol | power p-pol | Pin*sin^2(22.5 deg) |
| 10 W | 8.3 W | 1.78 W | 1.78 W |
In prep for a few days of dirty cabling/EE work under/around HAM3/2, we removed the HAM installation arm from HAM3. The arm will next be used on HAM2 in another week or two. Bubba/Hugh/Mitchell (and maybe one or two others?) put the HAM3 East door on. Tomorrow the other HAM3 and possibly both HAM2 doors will also go on. Other notes about MC2/MC3:
Both MC2 and PR2 in-vacuum cables have been plugged in, completing all routing. Signals are reading out in the appropriate medms.
Grounding was checked and mitigated on in-vacuum MC2 and MC3 cables.
B&K Hammer measurements were run on MC2.
MC2 has been left fully suspended, PR2 is locked however.
Cleanroom vacuums were tested chamberside. Particle counter alarmed a few times, as expected.
Attached are plots of dust counts > .5 microns in particles per cubic foot.
Lisa Austin, Scott (Apollo), Nichole Washington, Thomas Vo We chased a few holes in the viewport frame assemblies to give room around the top portion of the threads in order to give a bit more tolerance when installing the assemblies into the chamber. We finished all four (two per baffle) today, yay! We also finished assembling the aperture portions today and will be installing those tomorrow morning, which will close out this install.
I built a new h2tcsitmy model which makes it the same as the recently updated h2tcsetmy model. The new model was started on h2tcsl0.
New DAQ channels were added for the sus aux systems (h2susauxb478 and h2susauxb6).
H2 DAQ was restarted take the new configurations.
Noisy morning work (until noon) & then quiet for OAT afterward.
noon: quiet time begins!!
The high power stage was turned on for faraday isolator work. The PMC and FSS are locked, the ISS is unlocked while work is ongoing in the room.
The ILS had some trouble locking, but after raising the reference level to -1.2V from -1.4V it was able to continuously hold lock. The phase of the PMC LO was moved from 67 to 276. The PMC mode matching lenses were moved to the following positions:
L2
Old position (35W) - 368mm, 10.78mm on vernier
New position (200W) - 310mm, 10.78mm on vernier
L3
Old position (35W) - 738mm, 4.10mm on vernier
New position (200W) - 728mm, 4.10 on vernier
Position was measured on the north edge (towards HAM1) of the lens block that mounted onto the rail.
After correcting for alignment we had 126W transmitted and 30W reflected. I did not try to correct for mode matching losses, I only moved the lenses into their original positions, before we moved them to mode match the 35W laser.
The PMC ref level was changed to 1.22V from 1.11V.
The high power stage will stay on overnight but will be turned off for the weekend. I will take some DBB plots tomorrow and give everything some more time to warm up.
One more thing to note
The Florida high power beam dump at the far end of the table, used for IO power control, was not hooked up into the water manifold. We needed another high power dump for the transmitted beam through the faraday, so we hooked up the portable power meter to the water manifold and ran the Florida dump in series with it. This is only a temporary solution, as we will eventually remove the portable power meter.
The PMC heater does not look healthy, and has been going between rails since the transition. I'm not sure what is causing this, but I think it'd be worse to leave the PMC with the heater off so I'm leaving it in this state overnight.
(Jax, Elli) At 13:59:25 local time (20:59:25 UTC) 630mA was requested from each segement of the ITM. Cavity scans are being recorded. We'll turn the ITM ring heater off after 3 hours.
Running the ring heater is affecting the alignment of the cavity a lot, I'm having to increase the pitch offset on the ITM by about 25 counts every 2 minutes. Wavefront sensors are on.
Ring heater has been swtiched off at 17:31.
35W beam
We installed the compression rings on both A and B ends of the Mode Cleaner Tube (MC2) between HAM4 and HAM5. We completed assembly of all four of the Viewport Frame sections (2 per baffle). We attempted to attach the frames to the compression ring brackets and had difficulty. Screws were meeting resistance at three locations, one per frame. To prevent galling and particulate generation, we removed three of the four frames from the tube. One frame was successfully installed at MC2 A. The plan is to evaluate the #10-32 screws and tapped holes tomorrow morning. Lisa C. Austin, Thomas Vo, Nichole Washington and Scott (of Apollo).
[Alberto, Adam, Bram]
We locked the arm, with a jumpy RefCav. Starting time 21:04 local time, 22 August 2012.
The ETMY has the super sensor with the STS seismometer.
We did various WFS matirx measurements, came up with a matrix ... it looks wrong but seems to work. I set limits on the pit and yaw feedback signal and left them engaged for the night.
It is late, so more details later.
Got home, check the locking status ... the arm had dropped lock .... I commanded 'caput H2:ALS-Y_REFL_SERVO_IN1EN 0' followed by 'caput H2:ALS-Y_REFL_SERVO_IN1EN 1' and the cavity locked ... even more surprising it had a REFL power of 7000 ... and it started to move up automatically to 9200!! It seemed that the WFS are working
I tried to write an auto locker script but I hidiously failed. Although it may have something to do with a remote shell. I disengaged the REFL servo as it dropped lock and would not come back in the time I was trying to write the script.
We centered the WFS and repeated the measurement of the sensing matrix. We did it in two ways: a) measuring the frequency response of the PIT and YAW outputs of both BFS A and B when exciting the POS and ANG mode of the cavity at about 4 Hz; b) introducing offsets in the cavity's POS and ANG degrees of freedom and measuring the displacement of the PIT and YAW output of the WFS.
The first method gave us almost degenerate sensing matrix. The second one seemed a bit better. The measured matrix M was:
M =
0.0157 -0.7306 0 0
0.0708 -0.6684 0 0
0 0 0.0598 0.1663
0 0 -0.0210 0.3363
The PIT and YAW inverted matrices were:
iP =
-16.2163 17.7263
-1.7176 0.3814
iY =
14.2483 -7.0453
0.8899 2.5339
These are the matrices used for the overnight arm cavity locking.
Th eigenvectors of these matrices are:
VP =
-0.9931 -0.7741
-0.1177 -0.6331
VY =
0.9968 0.5341
0.0795 0.8454
(see below)
PIT sensing matrix that Bram posted in the above elog entry actually means this:
|WFSA| = |0.0157 -0.7306| x |POS| = |-0.7306 0.0000| x |-0.021 1| x |POS| |WFSB| |0.0708 -0.6684| |ANG| | 0.0000 -0.6684| |-0.110 1| |ANG|
The columns correspond to POS and ANG excitation, and the rows represent the WFS heads. (Sorry for the crappy formatting, I hope you get that I'm trying to write a matrix equation.)
POS refers to the translation of the cavity axis caused by the rotation of ETM and ITM in the opposite direction by the same amount. ANG refers to the rotation of the cavity axis by the rotation of the ETM and ITM in the same direction by the same amount.
For WFSA, ANG PIT generates a factor of 50-ish bigger signal than POS PIT. For WFSB, ANG IT is about a factor of 10 bigger.
Similarly, if you take the YAW matrix it's this:
|WFSA| = | 0.0598 0.1663| x |POS| = |0.1663 0.0000| x | 0.36 1| x |POS| |WFSB| |-0.0210 0.3363| |ANG| |0.0000 0.3363| |-0.06 1| |ANG|
If you look at the YAW numbers (not shown here but see the above entry by Bram), WFSA is a factor of 3-ish more sensitive to POS YAW than ANG YAW, and for WFSB this is a factor of 16.
Because of the cavity geometry (see below) ANG naturally produces a factor of 3 larger signal than POS. That means that, in terms of Gouy shift from the center of the cavity, WFSA for example is located at atan(-0.021*3) = -3.6 degrees away for PIT. Note that there's an uncertainty of n times pi that is common to all DOFs, and also the sign is sort of arbitrary though it should be consistent for both WFSs.
Anyway, below is the table of Gouy shift: from the waist of the arm in degrees (the above caveat about uncertaintly applies).
PIT YAW WFSA | -3.6 deg | +47 deg| WFSB | -18 deg | -10.6 deg|
PIT and YAW difference in WFSA looks kind of suspiciously large, but I would say that the crappy beam quality on the table could be blamed. It's not the TMS telescope (if it is, we'll see the same thing in WFSB too).
All in all the WFS locations could be adjusted better, and certainly the beam on the table is not passing through the center of lenses, but if the servo works (which we'll find eventually) I'll leave it.
----
Why a factor of 3 naturally?
Because we're using ETM substrate for both ETM and ITM, ROC of both is about 2300 m (2312 for EY, 2307 for IY).
Waist (w0=11.5mm for green) is at the center of the cavity, and the divergence angle is theta0=14.6 urad.
If we rotate both of the mirrors by the same amount (theta) as if one is the mirror image of the other, the cavity axis is purely translated by 2000m*theta. In terms of the higher order mode excitation, this is equivalent of
Normalized POS = 2000m * theta / w0 = 1.7e5 * theta.
ANG: If we rotate both of the mirrors by the same amount (theta) in the same direction, the cavity axis is purely rotated around the waist by (2300m * theta * 2)/600m. This is equvalent of
Normalized ANG = (2300m * theta * 2)/600m/theta0 = 5.3E5 * theta.
Therefore a factor of 3.
Electronics were troubleshooted.
SEI and SUS models were arranged to allow un-tripping HAM2-ISI Payload Watchdogs.
HAM2 model was re-compiled, installed and re-started after that. It is now running.
Matrices were filled
Input and output filters are loaded
The latest version (Version_2) of the unit-specific control scripts were copied from LASTI. They were made ready for use on HAM2.
Spectra were taken on the ISI tilted. It is the worse configuration for GS13s and they all appear to be working fine (see attached plot).
Transfer function measurements are running overnight.
The transfer functions measured last night had features that are typical to mis-connected sensors/actuators. Deeper analysis allowed narrowing it down the the GS13s.
We made a program to check for "cross-coupling transfer functions" (e.g. drive on H1, response on H2). It revealed that:
H1-GS13 was read on the channel of H3-GS13
H2-GS13 was read on the channel of H1-GS13
H3-GS13 was read on the channel of H2-GS13
V1-GS13 was read on the channel of V3-GS13
V2-GS13 was read on the channel of V1-GS13
V3-GS13 was read on the channel of V2-GS13
We checked our model and did not find a cause for such behaviour there. We moved on the the electronics rack and spotted the issue: GS13 In-field cables were connected to the wrong inputs on HAM2 sensor interfaces.
We ran a quick TF measurement between 500mHz and 5Hz. It confirmed that the sensors were now all correctly connected. This quick measurement is also in good accordance with what we measured on HAM-ISIs in the past which is encourraging.
TF measurement are running overnight on HAM2. They will be over by 7am.
Note: A blinking notification was recently added to HAM-ISI overview MEDM screens (see attachement). It turns the green "measurement" button to blinking yellow when a TF is running. HAM2 overview screen can be seen on the Video6 monitor of the Control Room.
Hugh and I added screwdriver tips under the top payload mass of HAM2-ISI last week, before the chamber was closed. They helped prevent this big mass of ~600lbs from causing unwanted resonances. Befoire/After comparison plots are attached.
We compared the latest transfer functions with the ones taken on LLO HAM2-ISI during the same phase of testing (Intitial In-Chamber Testing). Plots are attached. Accordance is good. We are confident that the unwanted resonance seen at 96Hz comes from the top mass. We plan on ajusting its boundary conditions with the optical table once the doors of HAM2 chamber are open again.
