Displaying reports 56101-56120 of 83527.Go to page Start 2802 2803 2804 2805 2806 2807 2808 2809 2810 End
Reports until 11:48, Wednesday 06 July 2016
H1 ISC (ISC, SUS)
carl.blair@LIGO.ORG - posted 11:48, Wednesday 06 July 2016 (28185)
Measurements of ETMY PI ESD
[Ross, Carl]
 
Measurements of the ETMY PI ESD path were made over the last week.  The DAC was also driven to saturation to investigate its behaviour.  We also drove multiple lines.
The measurement of the output voltage to the ESD with 80,000 counts drive is shown in the first figure.  It is very similar to measurements from other test masses.  The second image show the DAC saturation results.  We see the sub nyquist signal reach approximately its expected first Fourier component of a square wave ~ 4/pi times the saturation sinusoidal amplitude.  The super-nyquist frequencies do not reach this amplitude ratio.  This makes sense, as the sub nyquist saturates it removes lower amplitude super-nyquist information.  The saturated waveform does not however look like a square wave at all.  See the third and fourth image for an example of the waveform unsaturated and saturated with the DAC driven with ~ one million counts. 
[Ross, Carl]
 
Measuremets of the ETMY PI ESD path were made over the last week.  The DAC was also driven to saturation to see if it behaved as expected.  And we drove multiple lines.
The measurement of the output voltage to the ESD with 80,000 counts drive is shown in the first figure.  It is ver similar to measurments from other test masses.  The second image show the DAC saturation results.  We see the sub nyquist signal reach approximately its expected first fourier component of a square wave ~ 4/pi times the saturation sinusoidal amplitude.  The super-nyquist frequencies do not reach this amplitude ratio.  This makes sense, as the sub nyquist saturates more it removes lower amplitude supernyquist information.  The saturated waveform does not however look like a square wave at all.  See the fourth image for an example of the waveform when the DAC is driven with ~ one million counts. 
 
When two lines were driven the result was the expected beat signal.  The short video shows the beat in the spectrum showing sidebands when saturating and the time domain waveform.
When two lines were driven the result was the expected beat signal.  The short video shows the beat in the spectrum showing sidebands when saturating and the time domain waveform.
When two lines were driven the result was the expected beat signal.  The short video shows the beat in the spectrum showing side-bands when the signals are in phase and saturating and the time domain waveform.[Ross, Carl]
 
Measuremets of the ETMY PI ESD path were made over the last week.  The DAC was also driven to saturation to see if it behaved as expected.  And we drove multiple lines.
The measurement of the output voltage to the ESD with 80,000 counts drive is shown in the first figure.  It is ver similar to measurments from other test masses.  The second image show the DAC saturation results.  We see the sub nyquist signal reach approximately its expected first fourier component of a square wave ~ 4/pi times the saturation sinusoidal amplitude.  The super-nyquist frequencies do not reach this amplitude ratio.  This makes sense, as the sub nyquist saturates more it removes lower amplitude supernyquist information.  The saturated waveform does not however look like a square wave at all.  See the fourth image for an example of the waveform when the DAC is driven with ~ one million counts. 
 
When two lines were driven the result was the expected beat signal.  The short video shows the beat in the spectrum showing sidebands when saturating and the time domain waveform.
Images attached to this report
Non-image files attached to this report
MOV_0460e.avi
H1 General
cheryl.vorvick@LIGO.ORG - posted 11:21, Wednesday 06 July 2016 (28194)
Day Shift Morning Update: H1 laser work continues

State of H1: not able to make it through Locking ALS

Activities:

No significant site activities.

H1 INJ
evan.goetz@LIGO.ORG - posted 10:39, Wednesday 06 July 2016 (28193)
PINJ_TRANSIENT filter modules turned on

Chris B. noticed that the PINJ_TRANSIENT filter modules were all turned off. I have turned them back on, and updated the Guardian state so that these filters are monitored and set to be on in the observe mode.

H1 ISC
thomas.shaffer@LIGO.ORG - posted 10:03, Wednesday 06 July 2016 (28192)
ALS Y Fiber Polarization Adjusted

Was ~23% and brought it down to 2%.

ALS X was also at 2%

H1 PSL
edmond.merilh@LIGO.ORG - posted 09:46, Wednesday 06 July 2016 (28190)
PSL Weekly 10 Day trends - FAMIS #6103

Attached below are the past 10 day PSL trends. The trends reflect, largely the incursion into the enclosure due to the diode failure that occurred on Tuesday morning (July 5)

As usual refer to more in depth analysis to Jasoin O or Peter K.

In depth Chiller analysis can be referred to Jeff B

Images attached to this report
H1 PSL (PSL)
peter.king@LIGO.ORG - posted 06:30, Wednesday 06 July 2016 (28189)
ISS 
Came in and engaged the ISS.  Found it was in manual mode.  Left it in auto.  The integrator engaged straight
away.  This was before I did any temperature tuning of the laser diodes.

    Attached is the average diffraction over the past week.  I don't know why the spread was larger over the
past ~4 days and wonder if it was/is a portent of diode troubles.  Things seem okay at the moment.
Images attached to this report
H1 PSL (PSL)
peter.king@LIGO.ORG - posted 05:53, Wednesday 06 July 2016 (28188)
Front end laser temperature tuning 
After yesterday's front end diode box replacement, the diode temperatures were left at the values
from the old diode box.  The diodes are now temperature tuned for what I think is close to the
optimum values.  Optimum being decided by the output power of the front end.
Images attached to this report
LHO General
patrick.thomas@LIGO.ORG - posted 23:53, Tuesday 05 July 2016 (28186)
Ops Evening Summary 
Trouble keeping MC and FSS locked.

23:14 UTC Chandra to CP3
23:17 UTC Jenne and Sheila to LVEA to measure MC open loop gain
00:07 UTC Jenne and Sheila back
00:37 UTC Sheila to LVEA to plug in SR785 for analog measurement of MC open loop gain
00:44 UTC Sheila back
00:50 UTC Sheila to LVEA
00:54 UTC Sheila back
01:44 UTC Sheila to LVEA to set up RF analyzer
01:59 UTC Sheila back
H1 PSL (PSL)
jenne.driggers@LIGO.ORG - posted 21:51, Tuesday 05 July 2016 - last comment - 05:28, Wednesday 06 July 2016(28182)
ISS noisy since Friday

[Sheila, Keita, Jenne, Patrick]

We have been struggling to lock anything at all today.  Sheila is going to post about the loop measurements that we made today, but this alog is a cry for help with regard to the ISS. 

The ISS average diffracted power has been much more noisy than usual, ever since Friday.  Since today's PSL work, it's even worse.  We suspect that this may be bad enough that we are unable to lock.  We can no longer keep the integrator for the first ISS loop engaged for more than a few minutes before the loop starts to oscillate.  But, with or without the integrator on, the diffracted power is moving around like crazy.

At this point, we are leaving the IFO in Down, and hopefully someone from Team PSL will come in and look at the ISS tomorrow, and then maybe locking will be possible.

As a side note, it appears that everything in the PSL is misaligned by a bit.  Both the PMC and RefCav transmissions are about 25% lower than normal, with corresponding increases in their reflected powers.  This is probably the reason that we've had to increase the FSS loop gain earlier today to make locking even the IMC possible (see Sheila's alog).

Images attached to this report
Comments related to this report
sheila.dwyer@LIGO.ORG - 22:22, Tuesday 05 July 2016 (28183)
Link

Attached are measruements of the IMC open loop gain.  We cannot measure the FSS gain without going into the PSL, but Peter King posted some measurements from May

The first attached plot shows that the IMC goes unstable around 200 kHz when the FSS gain drops by only 2dB.  Since the power transmitted by the reference cavity droped 25% after the laser problem, this probably explains why we were having trouble keeping the IMC locked with our old FSS gain of 14dB.  (see Hoacun's measurement of the time when we reduced the fast gain from 20 to 14 dB for a comparison.)  It seems like we want more than 2dB of gain margin though...  The orange trace shows that the IMC OLG continues to improve as we turn the common gain up to 20dB, but in this configuration the FSS cannot recover from a lockloss.  If this is the reason we keep the FSS gain marginal, we could write a gaurdian to automate relocking at a lower gain and turning up the gain once locked.

We checked that the IMC optical gain has not changed since Evan H's mid June measurement. (taken on the day the IMC gain was reduced by 4 dB from a IN1 gain of 20dB for 2 Watts to 16 dB at 2Watts which gives us a UGF of about 65kHz).

The second plot shows what happens when we change the fast gain by +/- 4 dB, reducing the gain makes gain peaking at 200 kHz.  

The data attached is for the configuration we are leaving, IMC locked at 2 Watts with 16dB IN1 gain, FSS common gain 16 dB, FSS fast gain of 22 dB.

Non-image files attached to this comment
sheila.dwyer@LIGO.ORG - 22:25, Tuesday 05 July 2016 (28184)
Link

Also, there seems to be a problem with ALS DIFF after today's maintence.  We tried flipping the bias sign back, but that didn't help.  Since we still have laser/FSS/IMC problems we didn't investigate much further.

matthew.heintze@LIGO.ORG - 05:28, Wednesday 06 July 2016 (28187)
Link

My guess based on the LLO experience of late is its the ISS AOM. My suggestion (from afar) is to realign and recalibrate the ISS AOM (its something that Christina B from AEI suggested should be done each time laser alignment could change). Since Ive done ours, our fluctuations that were on the order of %'s during O1 and before has really settled down to barely vary at all (hopefully I haven't jinxed myself now).

 

However doing this to the ISS AOM will probably misalign the PMC a bit (but if its already misaligned and need to redo the alignment anyway, now is maybe a good time to try realigning and recalibrating the ISS AOM)

H1 CAL
evan.goetz@LIGO.ORG - posted 21:22, Tuesday 05 July 2016 (28179)
DARM open loop gain, sensing function, actuator coefficient measurements for ER9

Evan G., Jeff K., Kiwamu I., Darkhan T.

Summary:
We have processed the DARM open loop gain and sensing function measurements and built a model of the loop that we believe sufficiently represents our knowledge of the parameters. In addition, the actuator coefficients have been remeasured using the Pcal. In summary, our model reproduces the DARM open loop transfer function to within +/-10% in magnitude and within +/-5 degrees in phase from 10 Hz to 1 kHz. Caveat: we have not yet assessed how this translates to the overall calibration uncertainty. Actuation coefficients for L1, L2, and L3 are within +/-5% of their O1 values. This model is used in the recently updated CAL-CS model (alog 28178).

Details:
The DARM measurements made recently (alog 28107) were processed using the updated DARM model code. Included in this new model is a functional form for the SRC detuning (alog 28150), and the fit to the measured data gives updated cavity gain, cavity pole frequency, time delay, and detuning spring frequency. The uncompensated OMC whitening filters are updated (alog 28087). Since the L1, L2, and L3 driver compensation has been updated (alogs 27150 and 27180), we removed all the measured and compensation zeros and poles, except for the uncompensated high frequency zeros and poles of the L3 stage (alog 27619). The AA/AI downsampling filters are using the RCG 3.0 64-16k filter coefficients (alog 27173).

Attached are figures showing (in order) the measurement and model comparison DARM open loop gain transfer function, the measurement and model comparison of the sensing function, and the L1/L2/L3 actuation coefficient measurements calibrated using the Pcal.

It was realized that since we no longer read out H1:CAL-DARM_ERR_WHITEN_OUT_DQ for the for the Pcal to DARM transfer functions--instead we are reading out H1:LSC-DARM1_IN1_DQ--the measurement to model comparison for the sensing function should not include the 1 16k clock cycle delay. However, the model for the sensing function should include this 1 16k clock cycle delay.

We tried a few different values for unknown sensing and actuation delays but did not attempt to optimize this any further.

Non-image files attached to this report
2016-07-01_H1DARM_OpenLoopGain.pdf
2016-07-01_H1DARM_SensingFunction.pdf
2016-07-01_H1SUSETMY_ActuationCoeffMeas_L1_Pcal.pdf
2016-07-01_H1SUSETMY_ActuationCoeffMeas_L2_Pcal.pdf
2016-07-01_H1SUSETMY_ActuationCoeffMeas_L3_Pcal.pdf
H1 SEI
patrick.thomas@LIGO.ORG - posted 20:59, Tuesday 05 July 2016 (28181)
SEI ground seismometer mass position check 
There are 1 STS proof masses out of range ( > 2.0 [V] )!
STS EY DOF X/U = -2.072 [V]

(full results attached)
Non-image files attached to this report
results.txt
H1 CAL (CAL)
darkhan.tuyenbayev@LIGO.ORG - posted 18:25, Tuesday 05 July 2016 (28180)
Updated EPICS records for tracking DARM time-dependent parameters (param. set for ER9)

Evan G, Darkhan,

Summary

EPICS records that will be used by GDS pipeline for calculation of the DARM time-dependent parameters in ER9 were updated on 05-Jul-2016 17:44:57 PDT (06-Jul-2016 00:44:57 UTC).

Details

The H1 DARM model parameters used for generation of the EPICS values are

Output files: raw epics values, a verbose log and a Matlab file with EP# variables (see T1500377-08, Table 2) were committed to the calibration SVN directory (the verbose log is also attached to this alog):

Runs/PreER9/H1/Scripts/CAL_EPICS

./20160705_H1_CAL_EPICS_VALUES.txt
./20160705_H1_CAL_EPICS_verbose.log
./D20160705_H1_CAL_EPICS_VALUES.m
./callineParams_20160705.m
./writeH1_CAL_EPICS.m

Runs/O2/Common/Scripts/CAL_EPICS/writeO2_TDEP_EPICS.m

H1 CAL
jeffrey.kissel@LIGO.ORG - posted 18:13, Tuesday 05 July 2016 - last comment - 12:37, Wednesday 06 July 2016(28178)
H1 CAL CS Front End Calibration Updated for ER9 
J. Kissel, E. Goetz, K. Izumi, D. Tuyenbayev

Evan will post the details of the work we've had to do to get the model running, but in the interest of time, I've taken what we needed from the Matlab model to update the CAL-CS front-end filters. Since early results indicate that the only low-frequency (sub-Nyquist) things that have changed from the O1 model are in the sensing function (see LHO aLOG 28171):
   - Lower optical gain = 9.071e5 [ct/m],
   - Lower frequency DARM coupled cavity pole frequency, f_c = 328.7 Hz, and
   - New SRC-detuned optical spring frequency, f_s = 9.831 Hz.
I only needed to update the H1:CAL-CS_DARM_ERR inverse sensing function filter (see further discussion below). 

The new settings have been captured in the SDF system.

Details of the design:
Foton Design String --
       zpk([9.831;-9.831;328.7],[0.1; 0.1;7000],1,"n")gain(9574.81)*gain(1.102e-6)
The gain of 1.102e-6 is 1 / 9.071e5 [ct/m], this lives separately in FM4, called "ER9gain." In FM3, in the filter called "SRC D-2N" for "Signal Recycling Cavity De-Two-Ne" there lies:
- The pair of real poles at 9.831 Hz, one of which is in the right-half-plane, reflect the detuning dynamics. Note that we've rolled of these inversion zeros at low frequency of two real poles 0.1 Hz. 
- The 328.7 Hz is the new f_c, and we retain the same high-frequency roll off of 7000 Hz.  
- The gain of gain(9574.81) which is the correct normalization gain to get the over-all gain to be unity at 100 Hz, which is the frequency at which I matched the no-detuning gain of the (unused) 329:7000 filter in FM3.
The attached PDF shows that the ER9 gains agree between detuning and no detuning, and as expected, the overall optical gain is ~20% lower that O1 because we've not yet digitally compensated for the ~20% lower optical gain (because of 20% lower PRC gain; see LHO aLOG 28133) in the DARM loop.


Further Discussion on why I've only updated the Sensing Function:
All actuation strengths are within ~5% of there O1 values (see LHO aLOG 28130), and we've compensated all electronics better (see LHO aLOGs 27180, 27150, and 28087), so we need not update anything in the actuation chain. Rana and Evan H. have changed the local, top-mass damping loop filters for the QUADs, so nominally the QUAD dynamics have been changed, but that should be a small effect in the GW band. We'll update for O2, but no need for ER9. There have been several changes to effects at high-frequency, but all of those are covered in the GDS FIR filters which absorb the CAL-CS output and acausaly correct for these super-Nyquist frequency effects.
Images attached to this report
Non-image files attached to this report
2016-07-06_H1CALSCS_ER9_InvSensing_Update.pdf
Comments related to this report
jeffrey.kissel@LIGO.ORG - 12:37, Wednesday 06 July 2016 (28195)
Link 

J. Kissel, E. Goetz

After exporting the above SRCD-2N filter from foton and importing it back into matlab to compare against the matlab model of the sensing function, we discovered that my gain normalization was not perfect, and had a ~1% systematic error. This is likely because there is still some influence of the 9.8 Hz detuning poles at 100 Hz where I chose to normalize to the no-detuning filter. 

As such, instead, I've re-normalized to the gain at 500 Hz above the DARM coupled cavity pole. This results in a now-better-than-0.01% agreement with the matlab model in gain at all frequencies. I've updated the design string to
     zpk([9.831;-9.831;328.7],[0.1; 0.1;7000],1,"n")gain(9674.74)
and loaded coefficients.
H1 DAQ (CDS)
james.batch@LIGO.ORG - posted 17:04, Tuesday 05 July 2016 (28177)
Restarted h1tw0 trend writing 
Carlos, Jim

After installing Ubuntu 12 on h1tw0 and performing a file system check, the h1tw0 is now writing minute trend files.
LHO VE
chandra.romel@LIGO.ORG - posted 16:35, Tuesday 05 July 2016 (28175)
CP3 overfill 
4pm local

1/2 turn open on bypass LLCV - took 1:08 min. until LN2 came out the exhaust.
H1 CDS (DAQ)
david.barker@LIGO.ORG - posted 14:49, Tuesday 05 July 2016 - last comment - 16:42, Tuesday 05 July 2016(28168)
CDS maintenance summary

h1iscex lost timing

Jim, Dave:

at 09:41 PDT h1iscex lost its timing sync. Possibly due to a power cord being moved which drives the independent DC powered timing slave in the IO Chassis. Models were restarted at 11:50 PDT.

h1susetm and h1omcpi new models

Jeff, Carl, Dave

New h1susetm[x,y] and h1omcpi models were installed. DAQ was restarted

New Vacuum Controls code

Patrick, Dave

New Vacuum controls Beckhoff code was installed at all 7 locations. Required a DAQ restart.

alog tiny font fixed

an entry made this morning set the font size to x-small. This was fixed.

Ready to upgrade h1fw0 to 10 GigE if it becomes unstable WP5985

Jim, Dave

If h1fw0 becomes unstable, we will upgrade its CDS-LDAS link from 1GE to 10GE using borrowed LDAS cards. The next time it crashes it will not restart. We'll wait until 4pm PDT and then allow a restart.

Comments related to this report
david.barker@LIGO.ORG - 16:42, Tuesday 05 July 2016 (28176)
Link

will keep h1fw0 running overnight. the 4pm deadline passed, all daq systems have been running for 3 hours now. Reminder, difference now is that two 64kHz channels have been removed from the commissioning frame, six 512Hz channels added to science frame.

H1 SUS
rana.adhikari@LIGO.ORG - posted 15:56, Wednesday 01 June 2016 - last comment - 09:59, Wednesday 06 July 2016(27488)
SRM composite mass thermal noise

Rana, Evan

WE measured the SRM to SRCL TF today to find the frequency and Q of the internal mode. Our hypothesis is that the thermal noise from the PEEK screws used to clamp the mirror into the mirror holder might be significant contribution to DARM.

The attached Bode plot shows the TF. The resonance frequency is ~3340 and the Q ~150. Our paper and pencil estimate is that this may be within an order of magnitude of DARM, depending upon the shape of the thermal noise spectrum. If its steeper than structural damping it could be very close.

"But isn't this ruled out by the DARM offset / noise test ?", you might be thinking. No! Since the SRCL->DARM coupling is a superposition of radiation pressure  (1/f^2) and the 'HOM' flat coupling, there is a broad notch in the SRCL->DARM TF at ~80 Hz. So, we need to redo this test at ~50 Hz to see if the changing SRCL coupling shows up there.

Also recall that the SRCLFF is not doing the right thing for SRM displacement noise; it is designed to subtract SRC sensing noise. Stay tuned for an updated noise budget with SRM thermal noise added.

** see  https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=27455  for pictures of the SRM compsoite mass.

Images attached to this report
Comments related to this report
rana.adhikari@LIGO.ORG - 16:24, Wednesday 01 June 2016 (27489)
Link

The peak is also visible in the DARM spectrum. In this plot the peak is at 3335 instead of 3340 Hz. Why is there a 1.5% frequency shift?

Images attached to this comment
evan.hall@LIGO.ORG - 17:33, Wednesday 01 June 2016 (27490)
Link

Here are projected SRM thermal noise curves for structural and viscous damping.

Given a typical SRC coupling into DARM of 1×10−4 m/m at 40 Hz, 20 W of PSL power, and 13 pm of DARM offset (25019), this would imply a noise in DARM of 1×10−20 m/Hz1/2 at 40 Hz if the damping is structural.

Non-image files attached to this comment
calum.torrie@LIGO.ORG - 18:07, Wednesday 01 June 2016 (27493)
Link

When I modelled the optics in https://dcc.ligo.org/LIGO-T1500376 and in particular the surrogate SRM I had assumed optic was bonded. After looking again earlier with Rana and Betsy realised it is held with 2 set screws (Peek?) on barrell at 12 o'clock and two line contacts at 4 and 8 o'clcok. See https://dcc.ligo.org/LIGO-D1200886.

The previous bonded model for the SRM surrogate (I believe) had a fisrt mode predicted around 8k Hz. However, from a quick model I ran today (with the set screws etc ... ) the first mode appears to be around 3400 Hz. The mode is associated with the optic held with the peek screws. (Now I was doing model using remote desktop so I will need to check it again when I get a better connection, so more to follow on this. I will also post updated model, once I get back to Caltech.) 

stefan.ballmer@LIGO.ORG - 07:27, Thursday 02 June 2016 (27498)
Link

The ~3340Hz peak is also clearly visible in the PDA/PDB x-correlation spectrum. See alog 26345.

peter.fritschel@LIGO.ORG - 14:11, Thursday 02 June 2016 (27510)
Link

A couple of comments on this topic:

  • There is no feature at 3340 Hz in the L1 DARM spectrum, nor within several hundred Hz of this. So the main mode of the L1 composite SRM seems to be at a different frequency, though I think there has never been a transfer function measured there above ~1 kHz that would indicate the mode frequency (put on todo list). The first attached plot shows Kiwamu's full-O1 DARM and cross-correlation spectra for H1 and L1, zoomed in to the several kHz region. There are some peaks in L1 in the 4700-5100 Hz region, but it's fairly complicated in that region.
  • The thermal noise peak in Evan's SRM plot is at a level of 2e-15 m/rtHz, which is a bit above the SRCL sensing shot noise level, so we should be able to see it in SRCL. The second attached plot shows a spectrum of the SRCL error signal from January 9, 2016. From the Aug 2015 entry 20270, the shot noise corresponds to a displacement noise of 1.3e-15 m/rtHz. In the attached spectrum, the mode peak (which is at 3320 Hz here - ?), is 2.5x above the shot noise level, putting it at about 3e-15 m/rtHz. This is a bit higher than in Evan's model, but it is actually remarkably close. (I didn't include it in this plot, but the DARM spectrum also shows this peak at 3320 Hz at this time, and there is 0.8 coherence with SRCL at the peak.)
Images attached to this comment
Non-image files attached to this comment
matthew.heintze@LIGO.ORG - 08:11, Friday 03 June 2016 (27530)SUS
Link

Danny, Matt (Peter F remotely)

Due to the issues currently seen at LHO, we were asked how the LLO SRM surrogate was put together and if we could add to the alog for a record of the process. The easiest way is to do it via photos (which we have of the assembly process).

IMG_1462....There are only two setscrews that hold the optic in place. Can be seen putting these in place below in the "cup" that holds the optic (eventually). Im not sure of the material but Peter F's speculation is that "I think those set screws must be the carbon-loaded PEEK type. The only other option I can think of for a black set screw would be carbon-steel, and it surely isn’t that."

IMG_1455...Here you seen the three main parts. The optic, the “cup” that the optic goes into and then the main mass the cup goes in. Note in the “cup” you see the two raised parts at around 4 and 8 o’clock that the setscrews ‘push’ the optic onto. So its not 'really' a three point contact, its 2 points (set screws) and 2 lines (in the holder)

IMG_1466...Here is the optic going into the cup making sure the fiducial on the optic lines up with the arrow on the cup

IMG_1470.....Optic now in the cup and doing up the setscrews that hold it in place. I cant remember how much we torqued it up (we only did it by hand). But as Peter F again speculated that perhaps we just did the setscrews up tighter than LHO

IMG_1475....Flipping the cup (with the optic in it) over and placing in main mass

IMG_1478....Cup now sitting in Main mass (without screws holding cup into main mass)

IMG_5172......the SRM surrogate installed into the suspension

Images attached to this comment
peter.fritschel@LIGO.ORG - 13:36, Friday 03 June 2016 (27546)
Link

It looks like there might be a mode in the L1 SRM at 2400 Hz. See the attached plot of SRCL error signal from January, along with DARM and the coherence. There is also a broad peak (hump) around 3500 Hz in SRCL, with very low coherence (0.04 or so) with DARM. The SRCL data has been scaled by 5e-5 here so that it lines up with DARM at 2400 Hz.

Non-image files attached to this comment
evan.hall@LIGO.ORG - 12:56, Tuesday 07 June 2016 (27625)ISC
Link

Here are two noise budgets showing the expected DARM noise assuming (1) structural (1/f1/2) SRM damping and (2) a hyperstructural (1/f3/4) SRM damping. This hyperstructural damping could explain the DARM noise around 30 to 40 Hz, but not the noise at 50 Hz and above.

I also attach an updated plot of the SRCL/DARM coupling during O1, showing the effect of the feedforward on both the control noise and on the cavity displacement noise (e.g., thermal noise). Above 20 Hz, the feeforward is not really making the displacement noise coupling any worse (compared to having the feedforward off).

Note that the PEEK thermal noise spectrum along with the SRCL/DARM coupling is able to explain quite well the appearance of the peak in DARM.

Non-image files attached to this comment
evan.hall@LIGO.ORG - 09:59, Wednesday 06 July 2016 (28191)
Link

I am attaching noise budget data for the structural case in 27625.

Non-image files attached to this comment
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