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Reports until 16:43, Monday 04 April 2016
H1 General
nutsinee.kijbunchoo@LIGO.ORG - posted 16:43, Monday 04 April 2016 (26415)
Day Ops Summary

TITLE: 04/04 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in PT
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:'
LOG:

5:15 Jeff B. out to HAM6 area prepping clean room

5:27 Hugh out to lock HAM6 HEPI

6:30 Hugh out

7:00 Keita to ISCT6

9:15 Hugh locking up HAM5 HEPI

         Keita going back to ISCT6

9:34 Fill to CER to take down roation stage Ethercat chassis. This won't affect PSL power-up work.

9:50 Vern and Fill out of CER (with the chassis).

10:16 Travis head to EY to check PCal.

10:17 Bryn's taking a company  around the LVEA. They're informed to not go near HAM6.

10:28 Bryn and a company out of LVEA.

10:37 Bryn an company walking down the arm to EY VEA.

10:48 Jeff B out of the LVEA.

11:00 Travis back

11:35 Peter and Jason to PSL.

12:09 Vacuum team out

12:11 Jeff K restarting H1 OAF model

12:20 Bryn's back

12:35 Betsy to HAM5/6 area

13:13 Jeff B going back to HAM5/6 area

14:26 Jeff B out.

15:09 Fil to Y mid filling out the CP3

15:42 Kyle out working by BSC4

16:39 PSL Team out for the day. HPO fired up without problems.

LHO VE (VE)
gerardo.moreno@LIGO.ORG - posted 16:07, Monday 04 April 2016 - last comment - 16:54, Monday 04 April 2016(26432)
Manually over-filled CP3 at 22:15 utc

1/2 open LLCV bypass valve, and the exhaust bypass valve fully open.

Flow was noted after 5 minute and 45 seconds, closed LLCV valve, and 3 minutes later the exhaust bypass valve was closed.

Next over-fill on Monday, April 6th before 23:00 utc.

Comments related to this report
kyle.ryan@LIGO.ORG - 16:54, Monday 04 April 2016 (26434)
Wednesday, April 6th
H1 SEI
jeffrey.kissel@LIGO.ORG - posted 15:56, Monday 04 April 2016 (26430)
A New T240 has arrived!
J. Kissel, H. Radkins, R. McCarthy, A. Pele [remotely]

A brand new T240 has arrived from Nanometrics; the first of several over the next few year to replace our aging GND STS population. Yay, thanks Ken! 

The (order?) number on the outside of the 3 boxes we've received is 53341-2, and the serial number of the instrument itself is 953.

Our plan (eventually) will be to replace the ill-performing ETMX GND STS with this new instrument.
and then take the ill-performing STS and bury it outside to support wind-fend testing a la LHO aLOG 25842, and G1600548.

Arnaud has graciously offered to update the DCC's inventory E1200068. 

For now, I've put the T240 back in its box, and left it with the other two boxes in the shipping-and-receiving area. We still need to figure out the appropriate readout electronics situation, since we'd borrowed from 3IFO the *last* time we used a T240 at EX, and we'll now need both an STS readout (for outside) and T420 readout system (for inside).
Images attached to this report
H1 AOS
krishna.venkateswara@LIGO.ORG - posted 15:39, Monday 04 April 2016 - last comment - 15:42, Monday 04 April 2016(26429)
BRS-2 Installation DAY 10: Tilt Subtraction with BRS1 and BRS2

Michael, Krishna

Right on cue, winds picked up today and we got a good chance to test out both BRS-2 at EY and BRS-1 at EX. The wind speeds were in the 20-30 mph range during the following measurements.

EY: The first pdf shows the ASD of Ground seismometer (STS-2) and BRS-2 data and the online tilt-subtracted Y super-sensor data. The magnitude of Y ground motion at ~ 50 mHz is 10 microns/rt(Hz) while the tilt-subtracted Y channel is at ~1 micron/rt(Hz). The second page shows three lines - the first is the coherence between the ground seismometer and BRS-2 showing ~99% coherence in 10-100 mHz region. The second is the coherence between BRS-2 and Stage 1 Y and the third is between Stage 1 rX and BRS-2, showing significant coherences between them.

With BRS-2, we modified the damping scheme to have the damping set at Q of ~50 in the quiet state and Q of ~5 if driven up to a very large amplitude state (>5000 counts). We expect that we won't reach this large amplitude state under wind-speeds of < ~60 mph. The Q=50 state seems to not add any additional noise so far. We will do a more detailed analysis on this soon.

EX: The second pdf is for BRS-1, the ground STS-2 and a similar tilt-subtracted X super-sensor. The magnitude of Y ground motion at ~ 50 mHz is ~4 microns/rt(Hz) while the tilt-subtracted X channel is at ~0.7 micron/rt(Hz). On the second page,  the coherence between the ground seismometer and BRS-2 is ~96% in 10-100 mHz region. The coherences between BRS-2 and Stage 1 X and Stage 1 rY is smaller, especially that between rY and BRS-1 near the microseism. This last part is worrisome and I suspect that the rY sensor may have some problems - (I've noted this in the past - see 14426). Jim has promised to help look into this more by designing some high-frequency CPS-only blends for Stage 1. The idea is that by locking the platform as rigidly as possible to the ground, we can calibrate  the on-board rY sensor by comparing it to the ground (match T240 scale-factors). This may also prove useful for all other chambers which can be roughly calibrated by ensuring that the rY signal is small under quiet conditions.

The second minor issue with the EX data is that the coherence of BRS-1 with the ground seismometer data, and hence the subtraction is not as good as it was with the T240. Jeff tells me that this was the least reliable seismometer they had and will be replaced with a T240 very soon. A third issue is that the ~35 mph wind-gusts occasionally triggered the damper at EX. We will increase the large amplitude threshold for this damper, soon.

Summary: The tilt-subtraction at EX and EY is working reasonably well.

Non-image files attached to this report
Comments related to this report
krishna.venkateswara@LIGO.ORG - 15:42, Monday 04 April 2016 (26431)

Michael, Krishna

Here is similar data in angle units and matlab code for analysis. These have some extra information such as wind speeds.

Non-image files attached to this comment
H1 General
jeffrey.bartlett@LIGO.ORG - posted 14:53, Monday 04 April 2016 (26428)
Prep for HAM6 Vent 2.0
   First cleaning and vent prep staging are complete. Dust counts in the HAM6 cleanroom are excellent. They have been below 100 all day, even with the high level of activity around and in the cleanroom. There was one very high spike (18k both 0.3 and 0.5u particles), while there was cleaning going on inside the cleanroom. These cleared quickly after the crew left the cleanroom. Posted below are trends of the HAM6 dust monitor for the past 12 and 24 hours.   

   I did a compassion check of the new dust monitors and my HHPC-6 hand-held. No more than 10 count difference between the two monitors over several samplings.       
Images attached to this report
LHO VE
chandra.romel@LIGO.ORG - posted 14:23, Monday 04 April 2016 (26427)
HAM6 vent
Gerardo, Kyle, Chandra

Vented HAM6 this morning, after soft closing GV5 & GV7. Removed all but four bolts from each of three doors. Vent lasted ~ 1 hour.
H1 SEI
travis.sadecki@LIGO.ORG - posted 13:38, Monday 04 April 2016 (26426)
SEI Ground STS2 Seismometer Mass Position check

Averaging Mass Centering channels for 10 [sec] ...


There are 3 STS proof masses out of range ( > 2.0 [V] )!
STS EY DOF X/U = 3.345 [V]
STS EY DOF Y/V = 2.25 [V]
STS EY DOF Z/W = -4.708 [V]


All other proof masses are within range ( < 2.0 [V] ):
STS A DOF X/U = -0.337 [V]
STS A DOF Y/V = 0.17 [V]
STS A DOF Z/W = 0.584 [V]
STS B DOF X/U = 0.888 [V]
STS B DOF Y/V = 0.928 [V]
STS B DOF Z/W = 0.072 [V]
STS C DOF X/U = -1.081 [V]
STS C DOF Y/V = -0.328 [V]
STS C DOF Z/W = -0.434 [V]
STS EX DOF X/U = 0.55 [V]
STS EX DOF Y/V = -1.05 [V]
STS EX DOF Z/W = 0.414 [V]
 

This closes FAMIS task 4605.

H1 CAL
travis.sadecki@LIGO.ORG - posted 13:33, Monday 04 April 2016 (26425)
H1 PCALY issues

Today I went to EY to investigate the issues with the PCALY OFS described in aLog 26229. The first thing I noticed upon approaching the PCAL TX module were a pair of cables (red and yellow) coiled underneath the TX module enclosure.  Upon first inspection, I didn't notice anything else egregious.  Everything was powered on and appeared to be functioning.  I then opened the TX module and verified that the PCAL beam was making it to the OFS PD.  As I was closing the TX enclosure, I noticed that a cable was exiting the TX module at a non-perpendicular angle.  I then noted that this particular cable was the OFS PD cable.  It practically fell into my hand as I went to check it.  I then plugged the cable back in and secured the fixing screws on the connector to the module.  For peace of mind, I then checked ALL cables on the TX module and chassis for security.  Satisfied I had fixed the problem, and unable to log into the workstation adjacent to the PCAL module, I returned to the control room.

While the signals on the PCALY MEDM appeared to be reasonable, Kissel suggested that I turn the 3 PCALY exc. lines back on the verify.  When I did so, I saw that the oscillation monitor railed.  Turning them on one at a time, I could get the first two on, but the third (1kHz, 15000 amp.) line caused a rail.  I gradually stepped up the amplitude of the 1kHz (3rd) line, and saw that at ~4000, it railed.  I began playing with the OFS offset, which was set to 0.56V, and saw that by increasing by a factor of ~3, I could turn on the 1kHz, 15000 amp. line without issue.  Trending the offset, I saw that it changed from 4V to 0.56V on Mar. 23.  I could not find an aLog referencing this change, so I have restored it to 4V. 

After finding an OPS shift aLog referencing Fil and Peter doing table access system work on Mar. 17, I asked Fil if they were doing similar access system work at PCALY on the 18th.  He told me that they had replaced the key switches on the PCAL setup that day.  He also told me that the pair of cables I had noticed coiled under the TX module were for the access system, but had been done further in the past.  Mystery 1: What could have happened to the OFS? SOLVED.  Mystery 2: Why does LIGO always have a loose cable? Unlikely to ever be solved.

H1 SEI (CDS, DetChar)
jeffrey.kissel@LIGO.ORG - posted 12:49, Monday 04 April 2016 (26423)
Extra Filter Banks for SUSPOINT path added; IPC removed from H1OAF Model
J. Kissel, D. Barker
WP #5812

I'm continuing to work on filling out and debugging the recently installed SUSPOINT path (see LHO aLOGs 26363, 26321, 26320). 

I realized the part of that path which resides inside the OAF front-end model which projects the optic's Longitudinal displacement into the IFO Cavity Basis will need AI filtering for the corner station IPC channels (the ISI models send at 4096 Hz and the OAF model receives at 16384 Hz). Where there had previously only been test points and epics outputs to monitor the received channels, there are now full filter banks. Screens and details of filtering to come.

Also, while playing with the OAF model, Dave suggested we get rid of some more unused IPC connections. So, the "CONN" block -- some vestigial attempt at a monitoring system for the inter-process communication -- and its corresponding IPC senders (on of each flavor, Shared Memory SHMEM, Dolphin PCIe, Reflected Memory RFM) which had no receivers, have been removed. Attached is a screen shot of the block and senders we removed.

The latest version of the h1oaf model has been committed to the svn repo.

This required a frame-builder restart, but we've made no change to the DAQ channel list.
Images attached to this report
H1 CDS (DAQ)
david.barker@LIGO.ORG - posted 12:45, Monday 04 April 2016 (26424)
h1oaf model restart, h1fw1 continues to panic crash

h1oaf, addition of filter modules and removal of connection monitor part with IPC channel. WP5812

Jeff, Jim, Dave:

h1oaf was modified to add more filter modules and remove the unused "connection monitor" system, which frees up an RFM channel per arm. After the DAQ restart, h1fw1 panic crashed with:

Kernel panic - not syncing: Fatal execption in interrupt

This time I power cycled h1fw1 (after lessons learnt Friday) and it has been running for 20mins so far.

LHO VE
chandra.romel@LIGO.ORG - posted 12:04, Monday 04 April 2016 (26422)
Diagonal annuli pumping
HAM 8:   6 mA  @ IP and 2.6e-6 Torr at turbo
HAM 9:   8 mA and 6.0e-7 Torr at turbo
HAM 11:  10 mA+ (still with red light) and 2.1e-6 Torr at turbo
BSC4: 6.8e-6 Torr at turbo
H1 General
jeffrey.bartlett@LIGO.ORG - posted 11:26, Monday 04 April 2016 (26421)
Prep for HAM6 Vent
   Cleanroom over HAM5 & HAM6 has been patched up and is powered up. A first cleaning was done this morning. Clean crew (give them a big thanks for the phenomenal job of maintaining cleanliness in the LVEA and at the Ends) gave the floor an extra scrub. Initial dust counts do not look too bad considering the activities this morning around HAM6.

   Staged two small cleanrooms on the south wall ahead of the doors coming off. Several work tables have also been staged.

   Will do a second cleaning tomorrow morning before the doors come off.     
H1 SEI
hugh.radkins@LIGO.ORG - posted 10:53, Monday 04 April 2016 (26419)
WHAM5 HEPI Locked for Good Measure

Since HAM5 will be in the cleanroom and likely HAM5 will be bumped almost as much as HAM6, locked up HAM5 HEPI as well.

Position, relative to normally isolated:

-7um X, +15 Y, +31 Z, -10urad RX, -0.1 RY, +3 RZ.  The ISI remains isolated.  If the operator finds  either HAM5 or HAM6 tripped, maybe best to just put it in DAMPED.  The Chamber Manager has been paused since the HEPI can't isolate, so, you'll have to use the ISI Manager to change the guardian state.

H1 SEI
cheryl.vorvick@LIGO.ORG - posted 09:34, Monday 04 April 2016 (26418)
SEI in-vac T240 mass position check

Results are that three proof masses are out of range - I've emailed Hugh to make aware.

Averaging Mass Centering channels for 10 [sec] ...


There are 3 T240 proof masses out of range ( > 0.3 [V] )!
ETMX T240 2 DOF X/U = -0.387 [V]
ETMX T240 2 DOF Y/V = -0.399 [V]
ITMY T240 3 DOF Z/W = -0.303 [V]


All other proof masses are within range ( < 0.3 [V] ):
ETMX T240 1 DOF X/U = 0.041 [V]
ETMX T240 1 DOF Y/V = 0.063 [V]
ETMX T240 1 DOF Z/W = 0.083 [V]
ETMX T240 2 DOF Z/W = -0.251 [V]
ETMX T240 3 DOF X/U = 0.063 [V]
ETMX T240 3 DOF Y/V = -0.13 [V]
ETMX T240 3 DOF Z/W = 0.027 [V]
ETMY T240 1 DOF X/U = 0.011 [V]
ETMY T240 1 DOF Y/V = -0.069 [V]
ETMY T240 1 DOF Z/W = -0.02 [V]
ETMY T240 2 DOF X/U = -0.192 [V]
ETMY T240 2 DOF Y/V = 0.011 [V]
ETMY T240 2 DOF Z/W = 0.123 [V]
ETMY T240 3 DOF X/U = -0.028 [V]
ETMY T240 3 DOF Y/V = -0.026 [V]
ETMY T240 3 DOF Z/W = 0.071 [V]
ITMX T240 1 DOF X/U = -0.197 [V]
ITMX T240 1 DOF Y/V = 0.24 [V]
ITMX T240 1 DOF Z/W = 0.186 [V]
ITMX T240 2 DOF X/U = 0.201 [V]
ITMX T240 2 DOF Y/V = 0.244 [V]
ITMX T240 2 DOF Z/W = 0.227 [V]
ITMX T240 3 DOF X/U = -0.091 [V]
ITMX T240 3 DOF Y/V = 0.186 [V]
ITMX T240 3 DOF Z/W = 0.212 [V]
ITMY T240 1 DOF X/U = 0.165 [V]
ITMY T240 1 DOF Y/V = 0.027 [V]
ITMY T240 1 DOF Z/W = 0.095 [V]
ITMY T240 2 DOF X/U = 0.166 [V]
ITMY T240 2 DOF Y/V = 0.259 [V]
ITMY T240 2 DOF Z/W = 0.184 [V]
ITMY T240 3 DOF X/U = 0.037 [V]
ITMY T240 3 DOF Y/V = 0.194 [V]
BS T240 1 DOF X/U = 0.033 [V]
BS T240 1 DOF Y/V = 0.049 [V]
BS T240 1 DOF Z/W = 0.178 [V]
BS T240 2 DOF X/U = 0.12 [V]
BS T240 2 DOF Y/V = 0.196 [V]
BS T240 2 DOF Z/W = 0.205 [V]
BS T240 3 DOF X/U = 0.089 [V]
BS T240 3 DOF Y/V = 0.074 [V]
BS T240 3 DOF Z/W = -0.026 [V]


Assessment complete.

This closes FAMIS task 4367.
 

H1 SEI
hugh.radkins@LIGO.ORG - posted 07:38, Monday 04 April 2016 (26414)
WHAM6 HEPI Locked

Completed locking around 0615.  Ready to tolerate rambunctious activities.

Position is pretty good wrt nominal: +19um X, +15 Y, +38 Z, +5urad RX, -3 RY, & +7 RZ. Plenty level for ISI work.

H1 ISC
keita.kawabe@LIGO.ORG - posted 02:33, Monday 04 April 2016 - last comment - 09:08, Monday 04 April 2016(26412)
Before moving ISCT6

If you'd like to move the table, you need to do the following:

Comments related to this report
keita.kawabe@LIGO.ORG - 09:08, Monday 04 April 2016 (26417)

All done, ISCT6 was moved to the side of HAM5, JeffB is covering the duct opening on ISCT6. (JeffB, Richard, Kyle, Keita)

H1 SEI (ISC, SEI, SYS, VE)
vernon.sandberg@LIGO.ORG - posted 11:40, Friday 01 April 2016 - last comment - 08:32, Monday 04 April 2016(26389)
HAM6 Vent Plan for the Week of April 4, 2016

B. Weaver, H. Radkins, V. Sandberg

 

LHO WHAM6 Vent Plan for 2016 April 04 - 08

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

 

SCHEDULE

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

 

Comments related to this report
hugh.radkins@LIGO.ORG - 08:32, Monday 04 April 2016 (26416)

See D1201388-v4 for as-built of the Optical Table top payload, which may need to be removed temporarily.

H1 ISC
sheila.dwyer@LIGO.ORG - posted 17:49, Thursday 31 March 2016 - last comment - 16:21, Monday 04 April 2016(26367)
summarizing csoft pit oscillation information

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.  

Images attached to this report
Non-image files attached to this report
Comments related to this report
stefan.ballmer@LIGO.ORG - 10:43, Friday 01 April 2016 (26388)

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.

kiwamu.izumi@LIGO.ORG - 16:21, Monday 04 April 2016 (26433)

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.

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