Displaying reports 65721-65740 of 84502.Go to page Start 3283 3284 3285 3286 3287 3288 3289 3290 3291 End
Reports until 16:57, Monday 22 June 2015
H1 SEI
jim.warner@LIGO.ORG - posted 16:57, Monday 22 June 2015 - last comment - 10:00, Tuesday 23 June 2015(19281)
ER7 BSC-ISI performance spectra posted to DCC

A while ago there was a request for representative spectra of current HAM ISI performance at LHO. I posted a number of documents like pngs, ascii data files and DTT xmls to T1500289 in the DCC. I've now posted a similar document for the ETMX BSC-ISI at T1500318. The data is from about 8 AM on June 11, during ER7, and it's not exhaustive, but useful for a quick snapshot of the BSC's current performance.

Images attached to this report
Comments related to this report
jim.warner@LIGO.ORG - 10:00, Tuesday 23 June 2015 (19286)

Forgot to mention: all plots are calibrated in nm/nrad.

H1 SEI
jim.warner@LIGO.ORG - posted 16:39, Monday 22 June 2015 (19280)
ITMY blends are maybe an improvement

Friday, I said I was trying some new blends on ITMY. It looks like they are probably an improvement over the 90 mhz blends we are currently using. Attached plot shows op-lev and ground spectra, but the real test will be when we have arm cavities again. Red is pitch, green is yaw, black is gnd Y and pink is gnd Z. Dashed lines are the new blends, solid are the old blends. I also looked at the ISI local sensors, they largely agree, but I don't really want to post that many plots. Currently these blends are installed on ITMY and the BS, I have a script ready to install them on all chambers when people agree that we should make the change.

Images attached to this report
H1 SEI
hugh.radkins@LIGO.ORG - posted 16:25, Monday 22 June 2015 (19279)
EndX ETMX WBSC9 HEPI Unlocked

Will run tests in the morning.

H1 General
edmond.merilh@LIGO.ORG - posted 15:58, Monday 22 June 2015 (19265)
Daily Ops Summary

08:00 GRB alarm sounding. Will investigate for the exercise.

08:05 Alarm Handlers restarted.

09:00 Heintze to HAM6 area to get ready for Black Glass install

09:07 Bartlett o end stations to disable "monitor2" dust monitors

09:14 Heintze back from LVEA

09:25 Fil and Richard to MY and EY to measure for new vacuum cables

09:44 Calum ad Matt out to HAM6

09:46 Bartlett back

09:57 Corey out to LVEA to begin replacing handles

10:15 Bubba to crans a table and a small cleanroom over to the HAM6 area. There is no worl permit for this but John Worden gave his approval.

10:17 FIl and ichard back from Y arm

10:45 Karen and Christina to EY

11:17 Karen and hristina leaving EY and goin to MY

11:25 Karen and Christina skipped MY and are in the LVEA to clean a clean room by HAM6

11:30 Corey done in LVEA

12:15 HAM 6 crew out

13:12 Corey out to End stations to change out handles on ISC I/O tables

13:12 HAM6 crew back out into LVEA.

13:42 Jordan out to EY. PEM

14:23 Corey back from end stations

14:55 McCarthy out to the LVEA with interviewee and Ryan

15:07 Jordan back from EY

15:34 Hugh to EX to unlock HEPI

H1 SEI (ISC)
hugh.radkins@LIGO.ORG - posted 14:23, Monday 22 June 2015 (19276)
Position of WHAM6 while locked: Good enough for optic realignment?

Alignment of optics that will be moved on WHAM6 may be possible with the HEPI and ISI locked if the current position is close enough to operating position.  Easy to do, just look at the calibrated LocationMon channel for the IPS & CPS (HEPI & ISI).  Trending back a week and the vent and lock of HEPI and the ISI are clear.  The differences of now and before are:

Rx (Pitch if you will of the ISI & OMC) is 108urad; Ry (Roll) is -81urad; Rz (Yaw) is 34urads.  See attached for the data.

Images attached to this report
H1 General
jeffrey.bartlett@LIGO.ORG - posted 11:25, Monday 22 June 2015 (19273)
End-X & End-Y Vent Dust counts
Posted below are the dust trends for the past week, during the vets of End-X and End-Y. Plots are as expected. There are large numbers of high counts in the VEAs (monitor VEA1), which are consistent with work activities in the VEAs. The counts within the cleanrooms over the chambers show decent isolation of these spaces from the clouds of particles found in the VEA in general. 

   The large spikes within the cleanrooms (monitor VEA2)seen on 6/17 at End-Y and on 6/18 at End-X are the doors being installed. The flat line from VEA2 at End-Y starting on the 18th is the dust monitor being powered down.     
Images attached to this report
H1 SEI
hugh.radkins@LIGO.ORG - posted 09:50, Monday 22 June 2015 (19270)
STS2 Update--Unit on HAM2 (located in BG) from ETF Lab looks iffy.

LHO got two STS2s returned from Stanford a few days ago and they are in the BG area.  One is installed as ITMY or STS2-B; the other is on temporary cabling going into HAM2 or STS2-A.  The attached ASD shows that the Y axis on unit A has excess noise below 3 hertz.  The noise is much less on the X & Z. It might be reasonable that the tilt condition is different between the BG location for Units A & B and the HAM5 location for Unit C so I'm not confident saying anything about the differences at low frequencies between A/B and C.  But A and B are within a couple meters of each other and we should expect the tilts for A & B to be very similar.  This further suggests the HAM2 unit has issues.  I should move unit A to its final location by HAM2 and its dedicated cabling but we've been down this swap fest route before.

The attachment data is from Sunday ~5am local

Images attached to this report
H1 PSL (PSL)
edmond.merilh@LIGO.ORG - posted 09:27, Monday 22 June 2015 (19267)
PSL Status report
Laser Status: 
SysStat is good
Front End power is 33.1W (should be around 30 W); 29.1W @ Power Monitor PD
FRONTEND WATCH is GREEN
HPO WATCH is RED

PMC:
It has been locked 2 day, 21 hr 15 minutes (should be days/weeks)
Reflected power is 2.2 Watts  and PowerSum = 25.7 Watts.
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 2 d  21h and 29 min (should be days/weeks)
TPD[V] = 1.49V (min 0.9V)

ISS:
The diffracted power is around 7.2% (should be 5-9%)
Last saturation event was 2d 18 h and 5 m ago (should be days/weeks)

NOTES: ISS diffracted power was up to ~9% this morning. I've adjusted the refsignal from -2.12 to -2.14 to yield ~ 7.5%
H1 General
edmond.merilh@LIGO.ORG - posted 09:06, Monday 22 June 2015 (19268)
Morning Meeting Summary

We are currently LASER SAFE in the corner and the ends. PSL is shuttered, CO2 LASERs are OFF. End station Viewports and tables are closed and locked. Not sure about the on/off statues of the ALS.

Code Freeze has been deemed LIFTED

Basic LASER safety training for SURF and STAR students in LSB.

Corey replacing all handles on ISC I/O tables.

 

 

SEI - Jim working on blend filters

SUS - No ESDs until interlocks are re-installed; Kissel needs o determine which TFs still need to be run; HAM6 black glass has been cleaned - Heintze talked about how much of it will be installed in terms of the potential hampering of suspension wires.

VAC - https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=19252https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=19255. EY = 2.12e-06; EX 2.45e-06.

FAC - Beam Tube cleaning ongoing; Ken hanging tubing in bt enclosure for ion pump.

CDS - modifying end station Beckhoff; CHanging out HV power supply scheme for PSL from LVEA rack mounts to CER supplies. 

LHO VE
bubba.gateley@LIGO.ORG - posted 07:59, Monday 22 June 2015 (19264)
Beam Tube Washing
Scott L. Ed P.

6/18/15
Cleaned 39.8 meters of tube ending at HNW-4-082. Test results posted on this A-Log. Remove and begin re-hanging lights in next section north.

6/19/15
Completed hanging lights, start vacuum of support tubes and spraying of heavily soiled floor areas with water/bleach solution. Cleaned 20.8 meters of tube.
Non-image files attached to this report
H1 INS
kaitlin.gushwa@LIGO.ORG - posted 19:44, Sunday 21 June 2015 - last comment - 20:17, Tuesday 23 June 2015(19263)
OMC Black Glass Shroud - update

Calum & Kate

Finished unwrapping and inspecting all 26 panels of black glass. 100% of the parts made it in one piece and all of the coatings look good. This is great news! The panels are dusty, smudgy, and streaky; and will need to be cleaned (this was expected). The plan is to use a methanol rinse followed by drag wipping. 24/26 pieces of glass were rinsed 2x, so we're about halfway through the cleaning effort. Currently using 3 large cleanroom tables, but we'll need at least one more for prep work.

Two points of note for LLO:

1) The following parts were packaged between 2 sheets of float glass:

D1500054-101 & 102

D1500055-101 & 102

It was a good idea to protect the oddly shaped parts, but care should be taken when opening them because a couple pieces of the float (packaging) glass had chips and cracks and these were spread around the wrapping. Again these did their job and protected the black glass (which was in good shape) just a heads up.

2)  Some of the parts are double packed in the bubble wrap. Again caution when opening.

Comments related to this report
gary.traylor@LIGO.ORG - 20:17, Tuesday 23 June 2015 (19301)
All of the black glass at LLO was unwrapped today and laid out on a flow bench in the optics lab for inspection. Upon initial inspection for damage, there were no obvious chips or dings in any of the glass. The odd shaped pieces were in great shape with no abnormalities around the edges due to being sandwiched between glass for packing (the float glass was even flawless). Tomorrow we will check the coatings and begin the cleaning process. I will leave it to the inspection crew to record tomorrow but there were a few minor spot flaws in the coating on about 3 pieces.
H1 AOS
robert.schofield@LIGO.ORG - posted 15:21, Sunday 21 June 2015 (19261)
Completed study of acoustic coupling at HAM6

Turning the chamber over to next group. Report to follow.

H1 SUS
arnaud.pele@LIGO.ORG - posted 17:55, Wednesday 17 June 2015 - last comment - 11:20, Wednesday 24 June 2015(19208)
TFs started on ETMY and TMSY at 00:45 UTC

[sus crew]

Following the in chamber work from today at end-Y we took quick TFs on the quad and the transmon. They look ok.

Since the pump won't happen before tomorrow I started matlab tfs for all DOF.

The measurement will be running for few hours. 

Images attached to this report
Comments related to this report
arnaud.pele@LIGO.ORG - 11:20, Wednesday 24 June 2015 (19306)

More clue on the TMSX measurement showing a different TF than before the vent (cf log below 19246). I looked at the response from pitch and vertical drive to the individual osems (LF, RT) and it looks like something is funny with the RT osem which should have the same response as the LF one, cf light red curves below 

EDIT : Actually, LF and RT osem response are superposed on the graphs (green LF lies under red RT), so their response is the same.

Mountain View Mountain View

Images attached to this comment
arnaud.pele@LIGO.ORG - 23:16, Friday 19 June 2015 (19246)

EY measurements

ETMY ant TMSY transfer functions were measured on thursday after the doors went on, with chamber at atmospheric pressure. They did not show signs of rubbing, cf the first two pdf attached showing good agreement with previous measurements.

Today, I remeasured the vertical dof, after the suspension sagged ~120um from the pressure drop, and it still looks fine, cf figures below.

 
 
 
  The Pulpit Rock
 

EX measurements

ETMX and TMSX were measured today when pressure in chamber was about 3 Torrs, after the QUAD sagged by about 130um. 

 
 
ETMX TFs are similar to previous ones (3rd pdf), but the dynamics of TMSX table in pitch and vertical changed since the last measurement, cf figure below or 4th pdf. This might be ok, but the damping should be revised.
 
 
Images attached to this comment
Non-image files attached to this comment
arnaud.pele@LIGO.ORG - 14:54, Monday 22 June 2015 (19277)

The second pdf attachment on the log above was supposed to show TMSY transfer functions. Attached is the correct pdf. 

Non-image files attached to this comment
H1 ISC
keita.kawabe@LIGO.ORG - posted 16:10, Tuesday 16 June 2015 - last comment - 11:55, Monday 22 June 2015(19175)
Done with TMSY (Corey, Kiwamu, Keita)

ISI was locked by Jim in the morning.

Before doing anything, EY alignment slider [PIT, YAW] = [142.0, -75.1], TMSY = [116.6, -20.0], EY OPLEV=[-39, -15]-ish.

Transitioned to laser hazard, moved EY such that the green return beam hits the center of the relf PD: EY [PIT, YAW]=[207.4, -75.1]

- Krytox on beam diverter in situ: Good.

Everything went well as per yesterday.

- QPD strain relief: Good-ish.

Unlike TMSX, it turns out that all QPDs were already equipped with a make-shift strain relief using stainless steel cable clamps, the same clamps used for fixing the cables on the TMS ISC table, but the cables were without kapton tubes. We decided to install the right strain relief anyway.

In the end, we were able to install the right ones on three out of four QPDs. As for the remaining one (Green QPDB), we weren't able to install it as the 1/4-20 Allen key to attach the PEEK strain relief to the QPD base would have interfered with the YAW knob of one of the QPD sled mirror holders (M102 in D1201458).  The stainless steel strain relief was left as is.

After this work, we checked if QPDs still work and they did (used green beam for the green QPDs and a flashlight for IR QPDs).

- TMS balancing: Good.

After the work, we checked the balace of the TMS table with the green light injected to the chamber. The vertical alignment was found to be already good and therefore we did not make any mechanical adjustment. Similarly, the horizontal was also good and giving an extra digital bias of +13 urad (resulting in -7.0 urad in OPTICALIGN_OFFSET) made the return beam well-centered on ALS-REFL_PD. So the balance is good.

 

After everything was done: EY slider [PIT, YAW] = [142.0, -75.1] (back to the original), TMSY = [116.6, -7.0], EY OPLEV=[-24, -31]-ish.

Seems like EY moves around by 15urad-ish both in  PIT and YAW, so TMS alignment could be only as good as 15urad-ish.

Comments related to this report
corey.gray@LIGO.ORG - 21:31, Tuesday 16 June 2015 (19189)

Here are photos from EY TMS work today:  https://ligoimages.mit.edu/?c=1616

keita.kawabe@LIGO.ORG - 09:19, Monday 22 June 2015 (19269)
jameson.rollins@LIGO.ORG - 11:55, Monday 22 June 2015 (19274)

The certificate for ligoimages.mit.edu has expired, so this site is currently not accessible.

H1 PSL
edmond.merilh@LIGO.ORG - posted 10:08, Monday 15 June 2015 - last comment - 10:06, Monday 22 June 2015(19147)
NPRO Tripped again
Comments related to this report
edmond.merilh@LIGO.ORG - 10:11, Monday 15 June 2015 (19148)

I'm told this was intentional. I wasn't informed.

jason.oberling@LIGO.ORG - 14:00, Monday 15 June 2015 (19153)

This was actually completely accidental.  Peter and I went out to see if we could pull a log off of the NPRO UPS as part of our investigation into this morning's NPRO trip.  Turns out that when you plug in a DB9 cable to the back of the UPS, the UPS shuts off.  We did not know this.  Now we do.  Note to self...

In other news we were not able to establish communication between the laptop and the UPS, not sure why.  Will continue to investigate.

edmond.merilh@LIGO.ORG - 10:06, Monday 22 June 2015 (19272)

That make me feel much better about not having gone out there alone to try it!

H1 SYS (GRD, ISC, SYS)
sheila.dwyer@LIGO.ORG - posted 14:09, Thursday 11 June 2015 - last comment - 19:01, Thursday 29 August 2019(19075)
a look at duty cycle for the first week of ER7

I've taken a look at guardian state information from the last week, with the goal of getting an idea of what we can do to improve our duty cycle. The main messages is that we spent 63% of our time in the nominal low noise state, 13% in the down state, (mostly because the DOWN state was requested), and 8.7% of the week trying to lock DRMI. 

Details

I have not taken into account if the intent bit was set or not during this time, I'm only considering the guardian state.  These are based on 7 days of data, starting at 19:24:48 UTC on June3rd.  The first pie chart shows the percentage of the time during the week the guardian was in a certain state.  For legibility states that took up less than 1% of the week are unlabeled, some of the labels are slightly in the wrong position but you can figure out where they should be if you care. The first two charts show the percentage of the time during the week we were in a particular state, the second chart shows only the unlocked time. 

DOWN as the requested state

We were requesting DOWN for 12.13% of the week, or 20.4 hours.  Down could be the requested state because operators were doing initial alignment, we were in the middle of maintainece (4 hours ), or it was too windy for locking.  Although I haven't done any careful study, I would guess that most of this time was spent on inital alingment.

There are probably three ways to reduce the time spent on initial alignment:

Bounce and roll mode damping

We spent 5.3% of the week waiting in states between lock DRMI and LSC FF, when the state was already the requested state.  Most of this was after RF DARM, and is probably because people were trying to damp bounce and roll or waiting for them to damp.  A more careful study of how well we can tolerate these modes being rung up will tell us it is really necessary to wait, and better automation using the monitors can probably help us damp them more efficiently. 

Locking DRMI

we spent 8.7% of the week locking DRMI, 14.6 hours.  During this time we made 109 attempts to lock it, (10 of these ended in ALS locklosses), and the median time per lock attempt was 5.4 minutes.  From the histogram of time for DRMI locking attempts(3rd attachment), you can see that the mean locking time is increased by 6 attempts that took more than a half hour, presumably either because DRMI was not well aligned or because the wind was high. It is probably worth checking if these were really due to wind or something else.  This histogram includes unsuccessful as well as successful attempts.  

Probably the most effective way to reduce the time we spend locking DRMI would be to prevent locklosses later in the lock acquisition sequence, which we have had many of this week.

Locklosses

A more careful study of locklosses during ER7 needs to be done. The last plot attached here shows from which guardian state we lost lock, they are fairly well distributed throughout the lock acquisition process. The locklosses from states after DRMI has locked are more costly to us, while locklosses from the state "locking arms green" don't cost us much time and are expect as the optics swing after a lockloss. 

Images attached to this report
Comments related to this report
sheila.dwyer@LIGO.ORG - 18:13, Friday 19 June 2015 (19251)

I used the channel H1:GRD-ISC_LOCK_STATE_N to identify locklosses in to make the pie chart of locklosses here, specifcally I looked for times when the state was lockloss or lockloss_drmi.  However, this is a 16 Hz channel and we can move through the lockloss state faster than 1/16th of a second, so doing this I missed some of the locklosses.  I've added 0.2 second pauses to the lockloss states to make sure they will be recorded by this 16 Hz cahnnel in the future.  This could be a bad thing since we should move to DOWN quickly to avoid ringing up suspension modes, but we can try it for now.  

A version of the lockloss pie chart that spans the end of ER7 is attached.  

Images attached to this comment
jameson.rollins@LIGO.ORG - 08:38, Sunday 21 June 2015 (19258)

I'm bothered that you found instances of the LOCKLOSS state not being recorded.  Guardian should never pass through a state without registering it, so I'm considering this a bug.

Another way you should be able to get around this in the LOCKLOSS state is by just removing the "return True" from LOCKLOSS.main().  If main returns True the state will complete immediately, after only the first cycle, which apparently can happen in less than one CAS cycle.  If main does not return True, then LOCKLOSS.run() will be executed, which defaults to returning True if not specified.  That will give the state one extra cycle, which will bump it's total execution time to just above one 16th of a second, therefore ensuring that the STATE channels will be set at least once.

jameson.rollins@LIGO.ORG - 12:56, Sunday 21 June 2015 (19260)

reported as Guardian issue 881

sheila.dwyer@LIGO.ORG - 16:19, Monday 22 June 2015 (19278)

Note that the corrected pie chart includes times that I interprerted as locklosses that in fact were times when the operators made requests that sent the IFO to down.  So, the message is that you can imagine the true picture of locklosses is somewhere intermediate between the firrst and the second pie charts. 

I realized this new mistake because Dave asked me for an example of a gps time when a lockloss was not recorded by the channel I grabbed from nds2, H1:GRD-ISC_LOCK_STATE_N.  An example is

1117959175 

I got rid of the return True from the main and added run states that just return true, so hopefully next time around the channel that is saved will record all locklosses. 

H1 AOS
darkhan.tuyenbayev@LIGO.ORG - posted 20:57, Tuesday 09 June 2015 - last comment - 08:41, Monday 22 June 2015(19031)
Cavity pole fluctuations calculated from Pcal line at 540.7 Hz

Sudarshan, Kiwamu, Darkhan,

Abstract

According to the PCALY line at 540.7 Hz, the DARM cavity pole frequency dropped by roughly 7 Hz from the 17 W configuration to the 23 W (alog 18923). The frequency remained constant after the power increment to 23 W. This certainly impacts on the GDS and CAL-CS calibration by 2 % or so above 350 Hz.

Method

Today we've extracted CAL-DELTAL data from ER7 (June 3 - June 8) to track cavity pole frequency shift in this period. The portion of data that can be used are only then DARM had stable lock, so for our calculation we've used a filtered data taking only data at GPS_TIME when guardian flag was > 501.

From an FFT at a single frequency it is possible to obtain DARM gain and the cavity pole frequency from the phase of the DARM line at a particular frequency at which the drive phase is known or not changing. Since the phase of the resultant FFT does not depend on the optical gain but the cavity pole, looking at the phase essentially gives us information about the cavity pole (see for example alog 18436). However we do not know the phase offset due to time-delay and perhaps for some uncompensated filter. We've decided to focus on cavity pole frequency fluctuations (Delta f_p), rather than trying to find actual cavity pole. In our calculations we have assumed that the change in phase come entirely from cavity pole frequency fluctuations.

The phase of the DARM optical plant can be written as

phi = arctan(- f / f_p),

where          f is the Pcal line frequency;

                     f_p - the cavity pole frequency.

Since this equation does not include any dependence on optical gain, the technique we use, according to our knowledge, the measured value of phi does not get disturbed by the change of the optical gain. Introducing a first order perturbation in f_p, one can linearize the above equation to the following:

               f_p^2 + f^2
(Delta f_p) = ------------- (Delta phi)
                    f

An advantage of using this linearized form is that we don't have to do an absolute calibation of the cavity pole frequency since it focues on fluctuations rather than the absolute values.

Results

Using f_p = 355 Hz, the frequency of the cavity pole measured at the particular time (see alog 18420), and f = 540.7 Hz (Pcal EY line freq.), we can write Delta f_p as

Delta f_p = 773.78 * (Delta phi)

Delta f_p trend based on ER7 data is given in the attached plot: "Delta phi" (in degrees) in the upper subplot and "Delta f_p" (in Hz) in the lower subplot.

Judging by overall trend in Delta f_p we can say that the cavity pole frequency dropped to about 7 Hz after June 6, 3:00 UTC, this correspond to a time when PSL power was changed from 17 W to 23 W (see lho alog 18923, [WP] 5252)

Delta phi also show fast fluctuations of about +/-3 degrees, and right now we do not know the reason that causes this "fuzzyness" of the measured phase.

Filtered channel data was saved into:

aligocalibration/trunk/Runs/ER7/H1/Measurements/PCAL_TRENDS/H1-calib_1117324816-1117670416_501above.txt (@ r737)

Scripts and results were saved into:

aligocalibration/trunk/Runs/ER7/H1/Scripts/PCAL_TRENDS (@ r736)
Images attached to this report
Comments related to this report
darkhan.tuyenbayev@LIGO.ORG - 13:36, Thursday 11 June 2015 (19078)

Clarifications

Notice that this method does not give an absolute value of the cavity pole frequency. The equation

Delta f_p = 773.78 * (Deta phi)

gives a first order approximation of change in cav. pole frequency with respect to change in phase of Pcal EY line in CAL-DELTAL at 540.7 Hz (with the assumptions given in the original message).

Notice that (Delta phi) in this equation is in "radians", i.e. (Delta f_p) [Hz] = 773.78 [Hz/rad] (Delta phi) [rad].

shivaraj.kandhasamy@LIGO.ORG - 08:41, Monday 22 June 2015 (19266)

Darkhan, Did you also look at the low frequency (~30 Hz), both amplitude and phase? If these variations come from just cavity pole, then there shouldn't be any changes in either amplitude or phase at low frequencies (below cavity pole). If there is change only in gain, then it is optical gain. Any changes in the phase would indicate more complex change in the response of the detector.

H1 ISC (ISC)
sheila.dwyer@LIGO.ORG - posted 12:15, Tuesday 02 June 2015 - last comment - 16:49, Monday 22 June 2015(18777)
Trial of SR3 optical lever feedback to prevent locklosses

Daniel and I looked at three of the locklosses from Travis's shift last night, from 14:40, 14:02 and 11:33 UTC.  The earlier two both seem to be related to an alignment drift over 2-3 minutes before the lockloss, which shows up clearly in SR3 PIT.  (there is currently not feedback to SR3 PIT)  According to the witness sensors, this drift is only seen on M3.  No optics saturated until after the lockloss.  The DC4 centering loop, as well as both of the SRC alignment loops respond to the drift.  

Its unclear what causes the drift to accelerate in the minutes before the lockloss.  There is also a drfit of SR3 when we power up, as we noted yesterday, but this happens on a slower timescale than the dirfts that preceed a lockloss (3rd screenshot).  Also, there is a longer, slow drift that happens whenever we are locked.  

With Patrick and Cheryl I have engaged a DC coupled optical lever for SR3 PIT, we will see if this helps.  The last screen shot attached shows the MEDM screen used to turn this on or off.  

If the operators need to disable this (due to an earthquake, a trip, or if the optic becomes misalinged for any other reason) you can get to this screen from SR3, M2 OLDAMP.  

Turning off:  

turn off FM1 (labeled DC), then the input

Turning it back on:

Once the optic has settled and the beam is back on the oplev QPD, turn on the damping loop (with FM1 still off).  Average INMON (in a  command line tdsavg 10 H1:SUS-SR3_M2_OLDAMP_P_INMON), type -1 times the average into the offset, make sure the offset is engaged, and finally turn on FM1 to make the loop DC coupled.  

Since this is just a trial, Jeff is not including these changes in his current SDF cleanup campaign. 

Images attached to this report
Comments related to this report
daniel.sigg@LIGO.ORG - 13:22, Tuesday 02 June 2015 (18790)

Looking at the initial power up, we can see that an increase of a factor of ~10 causes ~0.7 µrad of pitch misalignment. During the accelerated drift in the last 3-5 minutes before the lock loss another 0.4 µrad of pitch misalignment was acquired with only ~10% of power increase. One might wonder, if we see a geometrically induced wire heating run away.

brett.shapiro@LIGO.ORG - 12:23, Saturday 06 June 2015 (18934)

I modeled how much the two front wires have to heat up to casue a bottom mass pitch of 1 microradian. A very small temperature increase is needed to predict this.

* Assuming a constant temperature profile along the wire length (I'm sure this is not the case, but it is easy to calculate), it is

0.003 [C]

* Assuming a linear temperature profile where with the max temperature is in the middle, and the ends of the wire have no temperature increase

0.006 [C]

So we can say an order of magnitude estimate is greater than 1 mC / urad and less than 10 mC / urad.

 

Calculations:

From gwinc, the thermal coefficient of expansion for C70 steel wire is

alpha = 12e-6 [1/C].

From the HLTS model at ../SusSVN/sus/trunk/Common/MatlabTools/TripleModel_Production/hltsopt_wire.m

wire length L = 0.255 [m]

front-back wire spacing s = 0.01 [m]

The change in wire length for pitch = 1 urad is then

dL = s * pitch = 0.01 * 1e-6 = 1e-8 [m]

* For uniform wire heating of dT, this change comes from

dL = alpha * L * dT

So, solving for dT

dT = dL / (alpha * L) = 1e-8 / ( 12e-6 * 0.255 ) = 0.0033 [C]

* For a linear temperature increase profile (max at middle, 0 at ends), I break the wire into many constant temperature segments of length Lsegment.

The temperature increase profile is a vector defined by

dT = dTmax * TempPrile

where TempProfile is a vector of the normalized shape of the temperature prodile. It is triangular, 0 at the ends and 1 at the peak in the middle. Each element of the vector corresponds to a constant temperature segment of the wire. dTmax is a scalar representing the maximum temeprature increase at the middle of the wire.

The change in wire length is then given by

dL = sum( alpha * Lsegment * TempProfile ) * dTmax

solving for dTmax

dTmax = dL / sum( alpha * Lsegment * TempProfile )

with 101 segments, this gives us

dTmax = 0.0063 [C]

about double the uniform heating case.

* I also considered that since the wire has significant stress due to the test mass weight, the Young's modulus's temperature dependence might cause a different effective thermal expansion coefficient alpha_effective. This appears to be a negligible effect.

From gwinc, the temperate dependence of the young's modulus E is

dE/dT = -2.5e-4 [1/C]

and young's modulus E is

E = 212e9 [Pa]

from https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=12581, we know that the change in spring length due to the modulus of eleasticity dependence is

dL = -dE/dT * dT * Tension / Stiffness

where Tension is the load in the wire and Stiffness is the vertical stiffness of the wire.

The Stiffness is given by

Stiffness = E * A / L = E * pi * r^2 / L

where A is the cross sectional area of the wire, and r is the radius.

So plugging this in above

dL = -dE/dT * dT * Tension * L / ( E * pi * r^2 )

We get the correction on alpha by dividing this by L and dT, which eliminates both from the equation. From the HLTS model, the bottom mass is 12.142 kg and the wire radius is 1.346e-4 m.

Tension = 12.142 * 9.81 / 4 = 29.8 [N]

The correction on alpha is then

-dE/dT * Tension / ( E * pi * r^2 ) = 2.5e-4 * 29.8 / (212e9 * pi * 1.346e-4^2) = 6.2e-7 [1/C]

This changes alpha from

12e-6 to 12.6e-6 [1/C]

Not enough to matter for the estimates above.

keita.kawabe@LIGO.ORG - 16:49, Monday 22 June 2015 (19163)

Localizing the heat source:

I made a calculation of the heat absorption by wires.

Based on Brett's temperature estimate, assuming the radiation as the only heat dissipation mechanism, the heat the front wires should be absorbing is about 1uW total per two wires when SR3 tilts by 1 urad regardless of the temperature distribution.

If you only look at the power, any ghost beam coming from PRC power (about 800W per 20W input assuming recycling gain of 40) can supply 1uW as each of these beams has O(10mW) or more.

I looked at BS AR reflection of X reflection, CP wedge AR both ways, and ITM AR both ways. I'm not sure about the first one, but the rest are mostly untouched by anything and falls on SR3 off centered.

The attachment depicts SR3 outline together with the position of CP wedge AR (green) and ITM AR (blue) reflections, assuming the perfect centering of the main beam and the SR3 baffle on SR3. Note that ITMX AR reflection of +X propagating beam falls roughly on the same position on SR3 as ITMY AR reflection of +Y propagating beam. Ditto for all ITM and CP AR reflections. The radius of these circles represent the beam radius. The power is simply 20W*G_rec(40)*(AR(X)+AR(Y))/4 (extra factor of 2 due to the fact that the AR beam goes through the BS) for ITM and CP, and 20W*40*AR/2 for BSAR of -X beam.

I haven't done any more calculations and I don't intend to, but just by looking at the numbers (total power in green and blue beams in the figure is about 240mW, 5 orders of magnitude larger than the heat absorbed by wires), and considering that the centering on SR3 cannot be perfect, and that SR3 baffle is somewhat larger than SR3 itself, and that CP alignment is somewhat arbitrary, it could be that these blobs seeps through the space between the baffle and the SR3 and provide 1uW.

The red thing is where BSAR reflection of -X beam would be if it is not clipped by the SR2 scraper baffle. If everything is as designed, SR2 scraper baffle will cut off 90% of the power (SR2 edge is 5mm outside of the center of the beam with 8mm radius), and remaining 10% comes back to the left edge of the red circle.

Any ghost beam originating from SRC power is (almost) exhonerated, because the wire (0.0106"=0.27mm diameter) is much smaller than any of the known beams such that it's difficult for these beams to dump 1uW on wires. For example the SRC power hitting SRM is about 600mW per 20W input, SRM AR reflection is already about 22uW.

Details of heat absorption:

When the temperature on a section of wire rises, the stretching of that section is proportional to the length of that section itself and the rise in temperature. Due to this, the total wire stretch is  proportional to the temperature rise integrated over the wire length (which is equial to the mean temperature rise multiplied by the wire length) regardless of the temperature distribution as is shown in effect by Brett's calculation:

stretch prop int^L_0 t dL = mean(t) * L

where L is the length of the wire and t is the difference from the room temperature.

Likewise, the heat dissipation of a short wire section of the length dL at temperature T+t via radiation is

sigma*E*C*dL*[(T+t)^4-T^4] ~ 4*sigma*E*C*dL*T^3*t

where sigma is Stefan-Boltzmann constant, E the emmissivity, C the circumference of the wire, T the room temperature (about 300K). The heat dissipation for the entire length of wire is obtained by integrating this over the length, and the relevant integral is int^L_0 t dL, so again the heat dissipation via radiation is proportional to the temperature rise integrated over the wire length regardless of the temperature distribution:

P(radiation) ~ 4*sigma*E*T^3*(C*L)*mean(t).

I assume the emmissivity E of the steel wire surface to be O(0.1). These wires are drawn, couldn't find the emissivity but it's 0.07 for polished steel surface and 0.24 for rolled steel plate.

I used T=300K, t=3mK (Brett's calculation for both of the temperature distributions), C=pi*0.0106", L=0.255m*2 for two front wires, and obtained:

P(radiation) ~ 0.8uW ~ 1uW.

ITM AR:

ITM has a wedge of 0.08 deg, thick side down.

ITM AR reflection of the beam propagating toward ETM is deflected by 2*wedge in +Z direction. For the beam propagating toward BS, ITM AR reflects the beam, deflecting down, and this beam is reflected by ITM and comes back to BS. Deflection of this beam relative to the main bean is -(1+n)*wedge.

AR beam displacement at BS is +14mm for +Z-deflection and -17mm for -Z-deflection. Since the BS baffle hole "radius" seen from ITMs is 100+ mm, and since the beam radius is about 53mm, AR  beams are not blocked much by BS baffle and reaches SR3.

ITM AR reflectivity is about 300ppm.

CP AR:

Similar calculation  for CP except that they have horizontal wedge, thick part being -Y for CPX and -X for CPY.

CP wedge is about 0.07 degrees.

I only looked at the surface of CP that is opposite of the ITM, and assumed that the surface facing ITM is more or less parallel to ITM AR, within an accuracy of O(100urad).

I assumed that S1 is the surface close to the ITM, and took S2 AR numbers from galaxy web page (43.7ppm for X, 5ppm for Y).

BS AR propagation:

BS wedge is 0.076 degrees, with a reflectivity of 50ppm.

Deflection of BS AR reflection of -X beam relative to the main beam is NOT -2*wedge as BS is tilted by 45 degrees. With some calculation it turns out that it is about -0.27 degrees, with a displacement of +48mm (positive = +X).

This beam is not obstructed at all by the BS baffle, hits SR3 and makes it to SR2 baffle edge. What made it to the SR2 surface doesn't go to SRM and instead comes back to SR3 as SR2 is convex  and the beam is heavily off-centered.

If there's no SR2 baffle and if SR2 is much larger, the center of the reflected beam is going to be  50cm in -X direction from the center of SRM, which happens to be on SR3.

I don't know what happens to the edge scattering and the reflection from SR2, but both of these are highly dependent on SR2 centering.

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