~1230 hrs. local -> Started pump cart ~1255 hrs. local -> Began pumping BSC4 annulus volume -> No change in PT140B resulted
1 April 2016
Site Activities:
15:45 JeffB - LVEA - 3IFO
15:53 JeffB - out of LVEA
15:20 Kirshna, Michael - EY BRS-2
17:20 Chandra and Kyle - hook up pump cart to BSC4
17:56 Kyle-Chandra - craning pump cart to prime location (West crane, will restore crane parking)
17:58 Water delivery done at both End Stations
17:59 Fil-Ed LVEA to eval upgrade to PSL electronics
19:30 all but Kyle out of the LVEA
20:03 Kyle out of the LVEA
H1 Activities:
15:20 Aiden, DaveB - EY Hartman testing code
17:25 COMM PLL red - not sure why, resolved after QPD offsets set
17:25 EX QPD offsets - Evan measuring Dark Offsets, since new hardware was installed
17:30 hartman EY epics not working - Dave and Aidan working on it
19:30 H1 attempting to lock DRMI, no known issues to prevent full lock
20:00 earthquake, 6.1, Papua New Guinea, guardian in Down
The PI AA/BP Chassis was reinstalled at EX this morning. No issues found with chassis, see alog 26351. Unit was left powered on, as not to pull down the TMS QPS's signals.
Unit installed in Rack SUS-C2, slot U21.
Using a power budget for IOT2L at input power to the IMC of 1W (alog 9331), which measured 12mW on REFL PD, and a modification to the IMC REFL path HWP (alog 9521) for IMC input power of 10W, which maintained the power on REFL PD of 12mW, I've calculated the power REFL PD saw in O1 at 22W IMC input, and will potentialy see in O2 at 50W. Summary below. Chart attached.
O1 numbers, 22W:
Potential O2 numbers, 50W:
B. Weaver, H. Radkins, V. Sandberg
DCC Document: E1600092, “HAM6 - ISI Damper Install”
https://dcc.ligo.org/LIGO-E1600092
APPROVED work to be done in order of importance:
Install HAM ISI Dampers assemblies (Jim W., Nutsinee K.).
Retune Tuned Mass Dampers (TMDs).
DCC Vent Documents referenced in this plan:
a) D1500469 Drawing documents for ham blade dampers
b) D1600085 Drawing documents for GS13 dampers
c) D1500200 Drawing documents for flexure dampers
d) D0900703 Drawing documents for Tuned Mass Dampers (TMDs)
e) E1100963 Retuning the TMDs
f) T1500580 HAM ISI Damping Study - Mittleman
g) G1500880 Damping Tests on Flexture Demo - Lantz
MON April 4, 2016 (possibly prior if time allowed)
1) Transition to LASER SAFE
2) Turn cleanrooms on around HAM6
3) Mark and move ISCT6 out of the way to facilitate door removal
4) Clean area, door flange, and cleanrooms
5) Stage supplies and equipment
a) Contamination control kit
b) B&K hammer setup and computer
c) Various ISI damper assemblies
d) ISI tool kit, TMD table setup
e) ISI parts as per E1600084
f) Septum viewport cover D1200448
6) Confirm dust monitor is working
7) Lock HEPI
8) Confirm purge air is on at HAM6
9) Vent HAM6
TUES April 5th, 2015
10) Remove ALL 3 CHAMBER DOORS – Review and follow M1100039 “ Hanford checklist – HAM Door Removal”
11) Entry chamber checklist items: Pick up floor CC wafers. Take particle counter measurements and record:
12) SEI Lock ISI
13) Entry chamber checklist items: Pick up table top CC wafers.
14)Install Septum Window Cover
15) Evaluate, mark and Move Beam Diverter ONLY IF ABSOLUTELY NEEDED for ISI work. IF CABLES of Beam Diverter get removed, a test of the Beam Diverter function will need to be made before closeout.
16) Start ISI damper install work.
a) ISI Wall units need to be moved for this work.
Note, DO NOT REMOVE ANY TABLE TOP OPTICS. Confer with Keita before hand if this is needed.
b) Remove Tuned Mass Dampers (TMDs)
c) Install new spring damper assemblies
d) Measure new spring modes using the B&K System
e) Retune TMDs with new info
f) Reinstall TMDs
WED April 6th, 2016
17) Continue ISI damper install work.
18) Take particle measurements and record:
THUR April 7th, 2016
19) Finish ISI damper install work
20) Check Beam Diverter functionality
21) Quick check of ISI Balance and clean TF
22) Remove Septum Window Cover
23) Chamber closeout – perform applicable exit checklist tasks E1201035.
24) Take particle count measurements and record:
25) Replace 1 HAM6 door if possible
FRI, April 8th, 2016
26) Replace remaining HAM6 Doors
27) Begin pump down
28) Reset ISCT6
See D1201388-v4 for as-built of the Optical Table top payload, which may need to be removed temporarily.
Michael, Krishna
There has been very little wind since we have had BRS-2 up and running so I'm posting some interesting data from the earthquake last night. The attached ASD plot, shows the spectra from the Mag 6.0 earthquake in Japan last night. The data set was about 10k secs and centered around peak of the earthquake.
The first blue line is the BRS-2 raw rX data showing the resonance at 7.6 mHz. The green line shows the BRS rX OUT from the filter banks. The third shows the ground seismometer's Y measurement showing the big peak at 50 mHz from the earthquake. Notice that there is absolutely no such signal in the BRS-2 output. This is because the acceleration coupling is very small as shown by the fourth line. Also, the real angular signal expected from the surface waves from this earthquake were not big enough to be resolved by BRS-2. We need a bigger earthquake to resolve the angular motion of the ground from them.
I've also attached the matlab code for this data set.
These are the temperature and RH data for the 3IFO Desiccant Cabinet in the LVEA and the two Dry Boxes in the VPW. There were some temperature fluctuation during the month but the RH remained constant and very low.
Pressure profiles over 1 day and 60 day attached Current pressures (Torr): PT-243: 1.05e-9 PT-244: 1.35e-9 PT-210: 1.35e-9
Pressure spike on 60 day plot on March 18th at 6pm local time likely from opening GV 1, 5 on March 18th after beam manifold vent.
1 April 2016
Site Activities: as of 15:26UTC (8:26PT)
Morning Meeting:
Major Activities by day of the week:
Monday:
Tuesday:
Wed: ...
Coming Up:
Questions that came up:
6 am reading (torr) PT243 - 1.07 x 10-9 PT244 - 1.39 x 10-9 PT210 - 1.40 x 10-9
4 am reading (torr) PT243 - 1.08 x 10-9 PT244 - 1.42 x 10-9 PT210 - 1.43 x 10-9
2 am reading (torr) PT243 - 1.09 x 10-9 PT244 - 1.45 x 10-9 PT210 - 1.45 x 10-9
12 am reading (torr) PT243 - 1.12 x 10-9 PT244 - 1.48 x 10-9 PT210 - 1.48 x 10-9
10 pm reading (torr) PT243 - 1.13 x 10-9 PT244 - 1.50 x 10-9 PT210 - 1.50 x 10-9 Note: time stamp of site overview different by two hours from Chandra's last entry yet same values
My 8pm reading turned into 9:30 because I forgot to look at 8. But my alarm is set for midnight, so get some sleep!
8 pm reading (torr) PT243 - 1.13 x 10-9 PT244 - 1.50 x 10-9 PT210 - 1.50 x 10-9
Tonight I moved the power recycling cavity axis around to try to center the spots on the ITMs. I was moving PR2 around, and the IFO's ASC followed me. It was a pretty significant move - enough that we no longer had green hitting the transmission cameras at the vertex. The carrier power recycling gain never really changed, but the sideband recycling gain decreased. I couldn't seem to recover this, even by moving the input beam (IM3 and a little IM2), so I have to think more about this.
Anyhow, when I tried to increase the power from 12W to 15W, I saw the ~0.5Hz pitch oscillations that Sheila describes in alog 26367. In general, the ASC loops are stable, however as we saw last night, it's very hard to get any coherence right near this peak, so I can't say for sure that we don't have a loop issue.
Big EQ in Japan, so we're calling it an early night.
We have an oscillation in H1 that has been with us for a long time, is not understood, and can be mitigated by moving alignment offsets, and gets worse at high power. All the information in this alog is elsewhere in the log, this is just a summary.
For about 6 months we didn't change our soft loop offsets because when we did we would get the oscillation, this is how we stayed stable through O1. The main symptom is that the pitch optical levers move at frequencies around 0.45 Hz, all in phase with each other, and if you look at the relative sign of the optical levers it looks like CSOFT motion. the POP and arm transmitted powers also oscillate. Now that our soft loops are working again, we are probably in a position to again tune the soft loop offsets to be stable at 20 Watts, but it seems like this won't be a great solution as we try to increase the power even further.
There have been many alogs about this, but I wanted to summarize some of the recent things we have looked at.
It seems like the torque that moves the test masses isn't coming from any of the arm ASC loops, or the optical lever damping. The first screenshot shows this, this is from Tuesday night when we powered up several times in slightly different configurations and repeatedly saw the same size of oscillation. The solid lines here show what was our normal configuration before Tuesday, with ITM optical lever damping on and ETM optical lever damping off. The dashed lines show the test configuration, where we added notches to the soft loops that reduce the actuation by about a factor of 100 at the oscillation frequency, and lowered the CHARD gains by a factor of 10. You can see that in the test configuration we also have about 5 and a half times less DHARD drive in the test configuration than in the normal one. Since all of these ASC drives are smaller in the test configuration but the oscillation is about the same, it seems like the force that moves the test masses must not be from these control signals.
It seems like the fluctuating radiation pressure due to changes in circulating power alone can't provide enough torque.
In the attached matlab script I estimated the miscentering we would need on each optic so that the approx 900 W changes in circulating power we see during the oscillation could provide the radiation pressure torque. These are way too large, ranging from 8-33 cm on the different optics. As a sanity check I also assumed that the alignment shift we see powering up before the soft loops get a changce to correct is due to radiation pressure (which it may not be). From that I estimate miscenterings ranging from 0.5-3 cm. I used the moment of interias from Evan Hall's alog , which he tells me are slightly wrong but not enough to matter.
The oscillation frequency does seem to depend on circulating power
The evidence for this may be a little shaky since it is hard to get enough cycles of the oscillation to get a spectrum with nice resolution, but the second attached screen shot shows a spectrum of ETMX optical lever pit for 3 different circulating powers. These circulating powers are based on Dan Hoak's calibration and the TR XB QPD. The frequency of the lower two powers is the same within the resolution of my spectra. This may not hang together perfectly because I have included a little bit of time when we were powering up or down in the spectrum.
| frequency | circulating power | time |
| 0.44 | 23.6kW | 30/03/2016 03:53:05 |
| 0.44 | 34.3 kW |
30/03/2016 03:53:38 |
| 0.515 | 52.9 kW |
31/03/2016 04:13:30 |
Other ideas?
We have also tried putting a resonant gain the DARM loop(no impact), changing A2L feedforward (no impact), and centering on the ETMs (improvement). One possible test we could try to understand this better would be to drive the laser intensity and see if we can produce angular motion.
Given the observation 1 and 3 (torque moves masses, frequency not dependent on power), the most likely guess is that power modulation changes the feed-back on the fundamental mode of the quad pendulum.
Note that this doesn't require obervation 2 (feed-back through torque alone).
Instead, we need to estimate the effective change in the Q of the fundamental mode:
Q_RP = (Energy in quad pendulum oscillation) / (Energy pumped into the mode due to delayed power fluctuations)
We can estimate all of this:
a)
(Energy in quad pendulum oscillation) =omega^2/2 * SUM_i [ m_i x_i^2 + I_i*theta_i^2 ]
where the sum goes over all 4 masses of one quad (test, penultimate, etc.) , and the amplitudes x_i and theta_i come from the quad model https://awiki.ligo-wa.caltech.edu/aLIGO/Suspensions/OpsManual/QUAD/Models/20140304TMproductionTM , scaled by the observed pitch amplitude.
The dominant term is from the test mass. Neglecting the other masses, and for a pitch amplitude of 3e-7 rad (typical), we get
(Energy in quad pendulum oscillation) = 2.3e-12 Joule
b)
(Energy pumped into the mode due to delayed power fluctuations) = 2*pi*P0/c * (x_disp) * sin(phi)
Here P0 is the amplitude of the power fluctuation in the arm - from Sheila's number's I get 3.84% of the arm build-up, so let's call it 0.0384*50kW = 1.92kW
x_disp is the pendulum movement = effecive_arm * (3e-7 rad) = 1.21e-7 meter (the effective arm comes directly from the Quad page: effecive_arm = 0.244m / 0.602rad = 0.40meter )
phi is the phase delay between the pendulum motion and the power fluctuation. For a 1Hz cavity pole (do we have a more accurate number?) this is about 23deg
All this gives
(Energy pumped into the mode due to delayed power fluctuations) = 1.9e-12 Joule
or
Q_RP = 1.2 (there are enough approximations here that I would't thake the actual value seriously - but the effect is certainly of the right order of magnitude.
This is a follow up study on the angular instability. I have looked at the phase relation between some relevant signals from the data sets that Sheila posted.
Here is a summary:
| relative phase [deg] on 30/03/2016 03:53:05 | relative phase [deg] on 30/03/2016 03:53:38 | relative phase [deg] on 31/03/2016 04:13:30 | |
| ETMX oplev | N/A | N/A | N/A |
| ITMX oplev | -0.7 | + 0.1 | -5.0 |
| ETMY oplev | +2.8 | -5.4 | +43.7 |
| ITMY oplev | -1.05 | -14.8 | +52.3 |
| TR_X (average of A and B) | +136 | +137 | -46.1 |
| TR_Y (average of A and B) | +131 | +134 | -32.0 |
| POP_A_LF | +90 | + 92.0 | -84.8 |
The phases are measured with respect to the ETMX oplev. All the optical levers listed above are for pitch. Also I attach some screen shots of diaggui in which I extracted these phase information by taking passive transfer function measurements.
Interestingly, the first two data sets show qualitatively the same phase relations. However, the last data set showed very different phase relations. For example, all optical levers were almost in-phase in the first two data sets, while the last data indicates that the Y arm moved in advance to the X arm by 50-iish deg. Also, the cavity power signals were in advance with respect to ETMX oplev in the first data sets, while they were delayed in the last data set -- it seems as if they flipped the phase by 180 deg between the first two data sets and the last data set for some reason. This phase flip might be a clue to understand the cause of the instability.
We've had much more success tonight with the non-broken Xarm Trans QPD. We once again re-centered the spots on the ETMs, although they didn't need much moving. We are able to sit at 10W and 12W just fine now. Now, we're running into regular ol' loop oscillations, so we've been measuring loops at different powers, and trying to re-tune them.
CHARD Y seemed the most egregious, so we created a new control and boost filter combo, which live in FMs 4 and 5. Unfortunately, these filters are totally unuseable at 2W, although they improve our stability at 10W, so right now the guardian still only engages the old loop shape filters. We'll have to re-think the 2W filter situation to make sure we can transition between these filters. Right now, we were by-hand turning off the CHARDY loop, changing the filters, then re-engaging the loop. Attached is an open loop gain for the new loop.
PRC2 pitch we've decided is kind of okay if we use a factor of 2 less gain.
Now, we're seeing oscillations that also show up in AS 90, so we suspect either the MICH or SRC angular loops. Unfortunately, there's something going on with NDS/the lockloss plotter/something, such that I can't get data from the last ~5 locklosses. The ones before that, I can still get and plot, but it can't find data for the last several even if it's been an hour since that lockloss.
So, next up: Measure the MICH and SRC loops at 10W to see if they're close to unstable. Measure again at 15W, and then think about going from there.
I feel I should know this already, but what is known about the QPD failure (circumstance at failure, failure mode, etc.)
It's not totally clear to me yet what the exact problem was. R.McCarthy is looking into why (apparently) putting the PI chassis spoiled the signal. Removing the new PI chassis seems to have fixed our problems. See alog 26328 and comments for symptoms and Rich's comment.
The PI AA was off and its OpAmp inputs were probably 'shorted' to ground due to the input protection diodes.
I am designing the input circuitry for the ITM PI Driver using the same input chip as that used on the ETM PI AA, so I will hedge our bets by including some input protection circuitry (current limit and clamp) to avoid this if that turns out to be the case.
In the lab, Fil reproduced the situation at EX by connecting a function generator to a coil driver test box (D1000931) and only used the single to differential converter of the board inside (D1000879) to drive the input of unpowered PI bandpass, and daisy chained to powered AA board.
Things looked OK until the PI input reached about +-1V differential (that's +-500mV positive and -+500mV negative), anything larger than that and the voltage started to be pulled down. Looked like a diode and a small resistor in series to me. As soon as the PI bandpass was powered on, everything got back to normal.
Daniel is correct. The chips used on the input to the PI filters have internal input protection diodes that will (up to the limit of their current handling capacity, which is not much over 10mA or so) clamp the voltage from the QPD amplifier to something around a volt. This is not a problem if the PI BPF is powered, which is the normal state of the system. This event prompted a redesign of the differential input to the ITM ESD Driver to avoid this in the future. Another case of incremental learning.
Reset a few times, but won't turn on.
This gauge was cycled as the result of a CDS reboot.
