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ID Date Author Type Category Subject
14365   Tue Dec 18 18:13:32 2018 aaronUpdateOMCOMC L HV Piezo driver tests (again)

I tested the OMC-L HV driver box again, and made the following observations:

• Drove the HV diff pins (2,7) with a 5V triangle wave
• Observed that with a ~0.4V offset on the drive, the HV output (measured directly with a 10x probe) has a 0-(almost)200V triangle wave (for 200V HV in), saturating near 200V and near 0V somewhat before reaching the full range of the triangle
• The HV mon gives the same answer as measuring the HV output directly, and is reduced 100x compared to the HV output.
• At 1Hz and above, the rolloff of the low pass still attenuates the drive a bit, and we don't reach the full range.
• Drove the HV dither pins (1,6) with a 100mV to 10V triangle wave, around 15kHz
• Even at 10V, the dithering is near the noise of the mon channel, so while I could see a slight peak changing on the FFT near the dither frequency, I couldn't directly observe this on a scope using the mon channel
• However, measuring the HV directly I do see the dither applied on top of the HV signal. The amplitude of the dither is the same on the HV output as on the dither drive.

[gautam, aaron]

We searched for blips while nominally scanning the OMC length.

We sent a 0.1Hz, 10Vpp triangle wave to the OMC piezo drive diff channels, so the piezo length is seeing a slow triangle wave from 0-200V.

Then, we applied a ~15kHz dither to the OMC length. This dither is added directly onto the HV signal, so the amplitude of the dither at the OMC is the same as the amplitude of the dither into the HV driver.

We monitored the OMC REFL signal (where we saw no blips yesterday) and mixed this with the 15kHz dither signal to get an error signal. Gautam found a pomona box with a low pass filter, so we also low passsed to get rid of some unidentified high frequency noise we were seeing (possibly a ground loop at the function generator? it was present with the box off, but gone with the AC line unplugged). [So we made our own lock-in amplifier.] Photo attached.

We tested the transfer function of the LP, and finding it at 100kHz rather than the advertised 10kHz, we opened the box, removed a resistor to change the 3dB back to 10kHz, and confirmed this by measuring the TF.

We didn't see flashes of error signal in the mixed reflection either, so we suspect that either the PZT is not actuating on the OMC or the alignment is bad. Based on what appears to be the shimmering of far-misaligned fringes on the AS camera, Aaron's suspicion from aligning the cavity with the card, and the lack of flashes, we suspect the alignment. To avoid being stymied by a malfunctioning PZT, we can scan the laser frequency next time rather than the PZT length.

Attachment 1: IMG_4576_copy.jpg
14366   Wed Dec 19 00:12:46 2018 gautamUpdateOMC40m OMC DCC node

I made a node to collect drawings/schematics for the 40m OMC, added the length drive for now. We should collect other stuff (TT drivers, AA/AI, mechanical drawings etc) there as well for easy reference.

Some numbers FTR:

• OMC length PZT capacitance was measured to be 209 nF.
• Series resistance in HV path of OMC lenght PZT driver is 10 kohms, so this creates a LP with corner 1/2/pi/10kohm/200nF ~80 Hz.
• Per Rob's thesis, the length PZT has DC actuation coefficient of 8.3 nm/V, ∼ 2 µm range.
16845   Wed May 11 15:49:42 2022 JCUpdateOPLEV TablesGreen Beam OPLEV Alignment

[Paco, JC]

Paco and I began aligning the Green Beam in the BS Oplev Table. while aligning the GRN-TRX, the initial beam was entering the table a bit low. To fix this, Paco went into the chamber and correcting the pitch with the steering mirror. The GRN-TRX is now set up, both the PD and Camera. Paco is continuing to work on the GRN-TRY and will update later on today.

In the morning, I will update this post with photos of the new arrangement of the BS OPLEV Table.

Update Wed May 11 16:54:49 2022

[Paco]

GRY is now better mode matched to the YARM and is on the edge of locking, but it more work is needed to improve the alignment. The key difference this time with respect to previous attempts was to scan the two lenses on translation stages along the green injection path. This improved the GTRY level by a factor of 2.5, and I know it can be further improved. Anyways, the locked HOMs are nicely centered on the GTRY PD, so we are likely done with the in-vac GTRY GTRX alignment.

Update Wed May 12 10:59:22 2022

[JC]

The GTRX PD is now set up and connected. The camera have been set to an angle because the cable to connect it is too thick for the camera to maintain its original position along the side.

Attachment 1: IMG_0770.jpeg
16906   Fri Jun 10 13:52:22 2022 JCUpdateOPLEV TablesITMX, ITMY, and Vertex Table Beam Paths

I have at taken photos and added arrows which signify the beam paths for ITMX, ITMY, and Vertex Oplev tables.

Attachment 1: DCE4F1D7-5AE0-491C-8AF6-F8B659C0787E_1_105_c.jpeg
Attachment 2: 4B24C891-654D-4C51-A8D9-D316364FCF68_1_105_c.jpeg
Attachment 3: F5B115E5-885F-463C-9645-BB2EB73B6144_1_201_a.jpeg
16912   Tue Jun 14 08:41:36 2022 JCUpdateOPLEV TablesBS Oplev Table Sketch

[JC]

Lately, I have been working on a 3d sketch of the BS OPLEV Table on SolidWorks. This is my progress so far, a few of the components I will have to sketch myself, such as the HeNe laser and photodiodes. This will just be a general layout of the HeNe laser, optics, and photodiodes.

Attachment 1: BS_OPLEV_Table.PNG
3180   Thu Jul 8 16:24:30 2010 GopalUpdateOptic StacksCompletion of single stack layer

Single layer of stack successfully modeled in COMSOL. I'm working on trying to add Viton springs now and extend it to a full stack. Having some difficulty with finding consistent parameters to work with.

3186   Fri Jul 9 11:41:58 2010 GopalSummaryOptic StacksTop Optic Layer Complete; Mechanical Tests Giving Problems

For the last week, I have been attempting to determine the mirror stack transfer function which relates mechanical mirror response to a given ground-motion drive. The idea is to model the stacks in COMSOL and ultimately apply mechanical tests for manual calculation.

Procuring the correct drawings to base my 3D models off of was no simple task. There are two binders full of a random assortment of drawings, and some of them are associated with the smaller chambers, while others are appropriate for the main chamber, which is what we're interested in right now. For future workers, I suggest checking that your drawings are appropriate for the task at hand with other people before wasting time beginning the painstaking process of CAD design in COMSOL.

The drawings that I ultimately decided to use are attached below. They detail four layers of stacks, each which arrange 15, 12, 8, and 5 (going from bottom to top) Viton damping springs in an orderly fashion. The numbers have been chosen to keep the load per spring as constant as possible, in order for all springs to oscillate with as close a resonant frequency to each other as possible.

After making some minor simplifications, I have finished modeling the top stack:

After triangular meshing, before my many failed attempts at mechanical testing:

Both the Viton and steel portions have been given their material properties, and so I should be (theoretically ) ready to perform some eigenfrequency calculations on this simplified system. If my predictions are correct, these eigenfrequencies shouldn’t be too far of the eigenfrequencies of the 4-layer stacked system, because of the layout of the springs. I’ve tried doing mechanical tests on the top stack alone, but there hasn’t been much progress yet on this end, mostly because of some boundary value exceptions that COMSOL keeps throwing at me.

In the next couple weeks or so, I plan to extend this model to combine all four layers into one completed stack, along with a simple steel base and mirror platform. I also plan to figure out how to make eigenfrequency and transfer function measurements.

Lastly, to anyone who is experienced with COMSOL, I am facing two major roadblocks and could really use your help:

1) How to import one model into another, merge models together, or copy and paste the same model over and over.

2) Understanding and debugging run-time errors during mechanical testing.

If you have any idea how to attack either of these issues, please talk to me! Thanks!

3199   Mon Jul 12 18:37:10 2010 GopalUpdateOptic StacksEigenfrequency Analysis of Simple Objects

Eigenfrequency analysis has been successfully completed in COMSOL on both a tutorial camshaft, as well as a homemade metal bar.

Upon increasing in complexity to the busbar, I once again began getting into run time errors and increased lag. It seems that this is due to undefined eigenvalues when solving the linear matrices. I tried many boundary values as well as initial conditions in case this was the issue, but it was not. There seems to be some sort of an internal inconsistency. This is no longer a matter of tweaking parameters.

Next steps:

1) Try using the same techniques on the actual mirror stacks to see if we get lucky.

2) In the likely case that this doesn't happen, continue the debugging process. If necessary, a good deal of time may need to be spent learning the COMSOL lower-level jargon.

3206   Tue Jul 13 13:56:29 2010 GopalConfigurationOptic StacksVitol Material Properties

Viton flouroelastomers have somewhat variable material properties. The following parameters are being used for eigenfrequency analysis.

Young's Modulus: 72,500-87,000 psi (cite: http://www.row-inc.com/pfa.html) *Accurate for PFAs

Poisson's Ratio: 0.48-0.50 (cite: http://www.engineeringtoolbox.com/poissons-ratio-d_1224.html) *Accurate for rubber

Density: 1800 kg/m^3 (cite: http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=275)

3207   Tue Jul 13 14:59:04 2010 GopalUpdateOptic StacksEigenfrequency Analysis of Single Stack Complete

Via reconfiguration of Viton parameters (previously posted), I managed to debug the COMSOL run time errors and null pointer exceptions. Listed are the resultant eigenfrequencies obtained through structural analysis testing. For all tests, the bottom of the Viton springs are constrained from motion, and all other parts are free to oscillate. Notice that color variations signify displacement from the equilibrium position. Also note that different initial conditions produce different eigenmodes:

No initial displacement:

0.01 m x-displacement:

0.01 m y-displacement:

0.01 m z-displacement:

Clearly, the plate has its first harmonic between 210-215 Hz, which is much greater than seismic noises (which never exceed the 10-Hz range). This suggests a highly attenuating transfer function. Since the remaining three plates have been designed to resonate similarly, it is likely that the entire stack system will also function very well.

Next steps:

1) Extend the eigenfrequency analysis to obtain a transfer function for the single-plate system

2) Expand the CAD model to include all four stack layers, and perhaps a base

3222   Wed Jul 14 19:00:56 2010 GopalConfigurationOptic StacksVitol Material Properties, REVISED

 Quote: Viton flouroelastomers have somewhat variable material properties. The following parameters are being used for eigenfrequency analysis. Young's Modulus: 72,500-87,000 psi (cite: http://www.row-inc.com/pfa.html) *Accurate for PFAs Poisson's Ratio: 0.48-0.50 (cite: http://www.engineeringtoolbox.com/poissons-ratio-d_1224.html) *Accurate for rubber Density: 1800 kg/m^3 (cite: http://physics.nist.gov/cgi-bin/Star/compos.pl?matno=275)

The Young's Modulus for PFA turned out to be orders of magnitude greater than for Viton. The revised values produced much more accurate results:

Young's Modulus for Viton-75: 1950 psi or 6.6 MPa

(Courtesy Row, Inc. and Steve Vass)

This website contains other details: http://www.row-inc.com/viton.html

3223   Wed Jul 14 19:15:26 2010 GopalSummaryOptic StacksREVISION: Eigenfrequency Analysis of Single Stack Complete

My previous eigenfrequency analysis was incorrect by two orders of magnitude due to the misuse of Young's Modulus information for Viton. After editing this parameter (as documented on 7/14 19:00), the eigenmodes became much more reasonable. I also discovered the Deformation option under the Surface Plotting Options, which makes the eigenmodes of the single stack much more apparant.

Attached are pictures of the first four eigenmodes:

First Eigenmode: y-translational, 7.49 Hz

Second Eigenmode: x-translational, 7.55 Hz

Third Eigenmode: z-rotational, 8.63 Hz

Fourth Eigenmode: z-translational, 18.26 Hz

Attachment 2: Eigenfrequency_2_Stack4.png
3224   Wed Jul 14 19:36:17 2010 GopalUpdateOptic StacksExperimental Confirmation of COMSOL Analysis

I experimentally determined the spring constant of a single Vitol spring in order to obtain a rough estimate for the natural frequency of single-stack oscillation.

The procedure basically involved stacking metal bars of known mass onto the Vitol and using a caliper to measure deviations from the equilibrium length.

The plot below shows that, for small compressions, the response is linear to an R-squared of 0.98.

The experimental spring constant came out to be about 270 lb/ft, or 3900 N/m.

Previous documents have listed that the top stack takes on a load of approximately 43 kg. per individual spring. A bit of calculation yields an experimental resonant frequency of 9.5 Hz.

Compared with the theoretical COMSOL first harmonic of about 7.5 Hz, there is a reasonable amount of error. Of course, I used this calculation as a simple ballpark estimate: errors from misplacement onto the Viton were minimized through use of a level, but were still inevitable on the mm scale. Since the two methods yield answers with the same order of magnitude, we are ready to move forward and build the remaining layers of the stack.

3246   Mon Jul 19 16:11:17 2010 GopalUpdateOptic StacksEigenfrequency Analysis of Full Stack

Expanding on the single-layer model, I added the second, third, and fourth layers to the stack in COMSOL. Eigenfrequency analysis run times increased exponentially as the model multiplied in complexity. The following images document the some of the important eigenfrequencies:

First Eigenmode: y-translational, 3.34 Hz:

Second Eigenmode: x-translational, 3.39 Hz:

Third Eigenmode: z-rotational, 3.88 Hz:

Sixth Eigenmode: z-translational, 8.55 Hz:

As expected, the eigenfrequencies are generally lower, but still in the same range, as the single-layer model, because of greater mass but constant weight-per-spring distribution.

Next Steps:

1) Extend a single stack to the full stack system, which consists of three stacks like this. Perform similar eigenmode analysis.

2) Analyze the mirror suspension system and incorporate a similar pendulum on the top plate.

3) Make transfer function measurements between seismic and mirror motions.

3252   Tue Jul 20 17:38:16 2010 GopalConfigurationOptic StacksStack Type Clarifications

Some clarification is warranted regarding the different shapes of stacks. Corrections are appreciated:

1) The single-leg stack that I just completed should function as a working model for the IO, OO, and MC1/3. Rana commented, however, that the current dimensions are slightly off for MC1/3 (which makes sense since I could only find drawings for the IOC). If anyone knows the whereabouts of similar drawings for MC1/3, I'd much appreciate it.

2) A triple-leg stack can model the BS, ITMX, and ITMY chambers. I don't have exact dimensions for these, but I can make decent approximations from to-scale stack drawings. I'll probably work on a model for this style next, since at least I have some information regarding this version.

3) The MC2 chamber has its own stack model, about which I haven't found any drawings in the binders. I can't start on MC2C at all until I find such drawings.

3261   Wed Jul 21 17:41:17 2010 GopalConfigurationOptic StacksPictures of Stacks

Now that venting is complete, this is a request for anyone who opens any chamber:

1) Please notify me immediately so I can take pictures of the stacks in that chamber.

2) If I'm not around, please take a few pictures for me. I'm most interested in the shape, number of layers, size, and damper arrangements of each stack.

This is most important for the MC1/MC3 chamber, MC2 chamber, and BS/ITMX/ITMY chambers.

Thanks!

3276   Fri Jul 23 14:26:01 2010 GopalUpdateOptic StacksSimple Frequency Response Measurements in COMSOL

Over the past couple days, I discovered a simple, direct method for calculating frequency responses with a combination of COMSOL and any plotter such as Excel or MatLab. The simple case of rectangular prism of steel was analyzed using this method; details will be posted shortly on the COMSOL Wiki page. The frequency response matched theoretical reasoning: the bar acts as a simple mechanical low-pass filter, rapidly attenuating driving frequencies at the base beyond the first eigenmode.

It therefore shouldn't be too difficult to extend this analysis to the MC1/MC3 stack. The many eigenfrequencies will produce a more complicated transfer function, and so more data points will be taken.

The major shortcoming of this method involves dealing with the imaginary components of the eigenfrequencies. As of now, I haven't found a way of measuring the phase lag between the drive and the response. I also haven't found a way of changing the damping constants and therefore playing with phase components.

3298   Tue Jul 27 12:02:31 2010 GopalUpdateOptic StacksPreliminary Transfer Function Measurements on MC1/MC3

I have successfully completed a preliminary transfer function measurement test on the MC1/MC3 stack in COMSOL. Using the measurement scheme described on the Wiki, I initialized a 1 N/m^2 sinusoidal perturbation on the bottom of the stack and measured the maximum displacement of the top layer. This preliminary test just calculated the responses to 1-,2-,3-,4-, and 5-Hz drives along the x-axis (pictures attached).

Currently, I am rerunning the same test but from 1-10 Hz with 0.1-Hz steps. When both x- and y-axis responses have been plotted, I can move on to repeating this entire process on the MC2 stack.

Attachment 1: MC1_MC3_FDA_1.png
Attachment 2: MC1_MC3_FDA_2.png
Attachment 3: MC1_MC3_FDA_3.png
Attachment 4: MC1_MC3_FDA_4.png
Attachment 5: MC1_MC3_FDA_5.png
3301   Tue Jul 27 18:42:57 2010 GopalUpdateOptic StacksBode Magnitude Plot and Concerns

I completed the frequency domain analysis mentioned previously in the x-direction. Although I ran it from 1-10 Hz, with 0.1-Hz increments, COMSOL was unable to complete the task past 7 Hz because the relative error was beyond the relative tolerance. To solve this issue, I'd have to rerun the simulation with a finer mesh, an unfavorable option because of the already-extensive run times. The Bode magnitude plot from this simulation is attached:

This simulation raises some questions about the feasibility of this method:

1) Do we have the computing power necessary?

I already moved my work from my personal Mac Pro to Kallo (4 GB --> 12 GB RAM difference). Now, instead of crashing the program constantly, I typically wait a half hour for a standard run of the model. Preferably, I could move my work to Megatron or some other workhorse-computer... but I also know that many of the big boys are already being strained as is.

2) Is it possible to take measurements through Matlab?

This way, I could write a script to instruct COMSOL and just run a few tests at a time overnight. Also, I wouldn't have to sit and record measurements manually as I've done here. The benefits of such an improvement warrant further attention. I'll work on this option next.

3) Up until what frequency do we need to model?

As I've shown, normal meshing yields data up to 7 Hz. Is this enough? Do we need more data? Certainly not less, I'm quite sure. We need to keep in mind that as frequency range increases, run times increase exponentially.

4) How do we incorporate gravity into the equation?

Gravity will produce a bit of extra force in the non-restoring direction for off-axis deviations, slightly decreasing the expected frequency. Whether or not this is an important effect is questionable, since the deviations are typically on the order of a micron, which is orders of magnitude smaller than the initial displacement I'm using on the base. I've decided to ignore this complication for now.

3324   Thu Jul 29 20:43:32 2010 GopalSummaryOptic StacksModeling Tips and Tilts

I have discovered a method of completely characterizing the 6x6 response of all six types (x-,y-, and z- translational/rotational) of oscillatory disturbances at the base of the stack.

• "Tipping" drives are trivial, and simply require a face load in the appropriate direction.
• "Tilting" drives could use a torque, but I am instead implementing multiple edge loads in opposing directions to create the appropriate net curl. This curl will be kept constant across the three axes for sake of comparing the resulting transfer functions.
• "Tipping" responses are once again trivial, and merely require the displacement vector of the top center coordinate to be recorded.
• "Tilting" responses require the normal vector to be recorded and manipulated to produce the angular coordinates (assuming right-handed coordinate system):
• θx = tan-1(x/z)
• θy = tan-1(y/z)
• θz = tan-1(y/x)

The first three concepts have been confirmed through simulations to produce correct transfer functions. The last test seems to be producing some problems, in that the vector normal to the equilibrium position (an obvious and useless piece of information) is sometimes given instead of the vector normal to the position of maximum displacement. This means that, as of now, I have the capability of measure the half of the complete 6x6 matrix of transfer functions in the coming weeks. The first three of eighteen transfer functions are attached below and will be included in my progress report.

3339   Sat Jul 31 04:03:11 2010 GopalSummaryOptic StacksComplete Displacement Translational Transfer Function Matrix

Over the past 36 hours, I've run full-fledged FDAs on KALLO.

The transfer functions for translational drives and responses are neatly described by the attached transfer function "matrix."

Next steps:

1) Extend the 3x3 analysis to include tilts and rotations in a 6x6 analysis.

2) Figure out how to do the same types of tests for phase instead of displacement.

3376   Fri Aug 6 15:50:29 2010 GopalUpdateOptic Stacks(Much Better Looking) Displacement-Displacment Transfer Functions

I reran the FDA in COMSOL on the MC1/MC3 Stack and produced the following Displacement-Displacement Transfer Functions:

X-Translational Drive has a blue background

Y-Translational Drive has a red background

Z-Translational Drive has a green background

Obtaining the Displacement-to-Phase part of the Transfer Function still produces difficulties -- I'm still working on the COMSOL-Matlab interface to perhaps better facilitate this.

RA: I have deleted those plots because they weren't transfer functions. Transfer functions must always be the ratio of something to something. For example: if I had a nickel for every bad plot I see, I would be a millionaire. In that example, the transfer function would have the units of nickels/plots. For the stacks, it should be meters/meter.

Attachment 1: MC1_MC3_XTrans.png
Attachment 2: MC1_MC3_YTrans.png
Attachment 3: MC1_MC3_ZTrans.png
3380   Fri Aug 6 19:46:59 2010 GopalUpdateOptic Stacks(Much Better Looking) Displacement-Displacment Transfer Functions

 Quote: I reran the FDA in COMSOL on the MC1/MC3 Stack and produced the following Displacement-Displacement Transfer Functions: X-Translational Drive has a blue background Y-Translational Drive has a red background Z-Translational Drive has a green background Obtaining the Displacement-to-Phase part of the Transfer Function still produces difficulties -- I'm still working on the COMSOL-Matlab interface to perhaps better facilitate this. RA: I have deleted those plots because they weren't transfer functions. Transfer functions must always be the ratio of something to something. For example: if I had a nickel for every bad plot I see, I would be a millionaire. In that example, the transfer function would have the units of nickels/plots. For the stacks, it should be meters/meter.

My apologies for the mislabeled axes on my previous plots. They have been corrected to a ratio (in./in.), as Rana so kindly suggested in his helpful, not-at-all-condescending response.

I have chosen to stay in the English system because all of the original stack drawings are in inches as well.

3418   Fri Aug 13 01:53:12 2010 GopalUpdateOptic StacksGravity Implementation Confirmed

Time Domain Analysis on a Driven, Damped Simple Pendulum has produced a method for implementing gravity.

• Previous Frequency Domain testing lead to unwanted oscillations of all loads.
• Prescribed accelerations at first seemed to create a constant gravity, but instead incorrectly constrained net acceleration to the inputted amount

Methodology:

1) An (approximately) impulse displacement was applied in the horizontal direction. The pendulum bob's displacement was observed for varying pendulum lengths.

2) The drive and response displacements vs. time were FFT'd to produce transfer functions.

3) The fundamental frequencies were inverted, squared, and plotted against frequency.

4) Since the graph is linear with an R^2 of over 0.99, it is reasonable to assume that gravity is properly acting as a restoration force.

Attachment 1: Pendulum_Length.png
Attachment 2: Pendulum_Length.png
10455   Fri Sep 5 00:56:00 2014 ranaSummaryOptical LeversITM OLs recentered: violations found

I re-centered the ITMX & ITMY Optical lever beams today since they were off. First I aligned the beam into the vacuum so that it went through the center of the on table optics and then tweaked the receiver optics alignment.

There are several bad practices on these which probably makes them drift:

• plastic bases on some lens mounts
• some lens mounts are fastened with a single dog instead of two
• there is no need to use dogs on mounts that have screw holes. Just put the mount so that 2 screws with washers can be used. The placement for these is not so critical.
• Use less steering mirrors! The ITMY OL path has 5 optics the beam enters the vacuum!!!

According to the datasheets, the laser has a beam diameter of 0.6 mm and a divergence angle of 1.3/2 mrad. So we can just calculate the right lens positions next time and not have to experiment with the whole visible laser lens kit.

For next Wednesday's cleanup, someone should volunteer to make the mounts more stable for the ITMs.

10731   Fri Nov 21 13:58:51 2014 ericqUpdateOptical LeversHeNe RIN test

Steve had me measure the RIN of a JDSU HeNe laser. I used a PDA520, and measured the RIN after the laser had been running for about an hour, which let the laser "settle" (I saw the low frequency RIN fall after this period).

Here's the plot and zipped data.

Steve: brand new laser with JDSU 1201 PS

Attachment 1: 2014-11-21_HeNeRIN.zip
10735   Tue Nov 25 14:52:14 2014 ericqUpdateOptical LeversOpLev RINs

At Rana's request, I've made an in-situ measurement of the RIN of all of our OpLevs. PSL shutter closed, 10mHz BW. The OpLevs are not neccesarily centered, but the counts on darkest quadrant on each QPD is not more than a factor of a few lower than the brightest quadrant; i.e. I'm confident that the beam is not falling off.

I have not attached that raw data, as it is ~90MB. Instead, the DTT template can be found in /users/Templates/OL/ALL-SUM_141125.xml

Here are the mean and std of the channels as reported by z avg 30 -s, (in parenthesis, I've added the std/mean to estimate the RMS RIN)

SUS-BS_OLSUM_IN1 1957.02440999 1.09957708641 (5.62e-4)
SUS-ETMX_OLSUM_IN1 16226.5940104 2.25084766713 (1.39e-4)
SUS-ETMY_OLSUM_IN1 6755.87203776 8.07100449176 (1.19e-3)
SUS-ITMX_OLSUM_IN1 6920.07502441 1.4903816992 (2.15e-4)
SUS-ITMY_OLSUM_IN1 13680.9810547 4.71903560692 (3.45e-4)
SUS-PRM_OLSUM_IN1 2333.40523682 1.28749988092 (5.52e-4)
SUS-SRM_OLSUM_IN1 26436.5919596 4.26549117459 (1.61e-4)

Dividing each spectrum from DTT by these mean values gives me this plot:

ETMY is the worst offender here...

10802   Tue Dec 16 00:20:06 2014 diegoUpdateOptical LeversBS & PRM OL realignment

[Rana, Diego]

We manually realigned the BS and PRM optical levers on the optical table.

11224   Thu Apr 16 10:32:42 2015 SteveUpdateOptical Leversoplevs monitoring

The IFO_overview of oplevs seems ok, The servos are working fine. The green arms are locked, but master and oplev_summary monitoring screens are not.

I'm proposing to Erick G. to postpone the oplev noise measurement.

Attachment 1: oplevCond.png
11230   Tue Apr 21 11:55:05 2015 SteveUpdateOptical Levers1103P noise measurement

Manasa and Steve,

Is this what you want?  Dashed lines are dark.

BS and PRM oplevs are blocked for this measurement. I will restore to normal operation at 4pm today.

Attachment 1: 1103P@qpdBS.jpg
Attachment 2: oplev1103P.png
Attachment 3: oplevSum1103Pbs.png
11231   Tue Apr 21 15:03:27 2015 ranaUpdateOptical Levers1103P noise measurement

It doesn't work with the lens in there, but it seems pretty close. Please leave it as is and I'll play with it after 5 today.

11232   Tue Apr 21 21:46:34 2015 ranaUpdateOptical Levers1103P noise measurement

To test what the inherent angular noise of the HeNe 1103P laser is, we're testing it on a table pointing into the BS OL QPD with only a few steering mirrors.

From the setup that I found today, I've removed the lens nearest to the laser (which was used for the BS and PRM) as well as the ND filter (what was this for?) and the lens placed just before the BS QPD.

With the ND filter removed, the quadrant signals are now ~15000 if we misalign it and ~9000 each with the beam centered.

In order to calibrate the OLPIT_IN1 and OLYAW_IN1 signals into mm of beam motion, I misaligned the mirror just before the QPD. The knobs on there actuate the 100 TPI screws and the knurling on the knob itself has 10 ridges, so that's 36 deg per bump.

Pit Knob (deg) OLPIT Yaw Knob (deg) OLYAW
0 29 0 -36
45 13 36 -16
90 -16 72 19
135 -39 108 36

PIT cal ~ 1.55 (knob deg / count) -->> 10 microns / count --->>> 10 urad / count

YAW cal ~ 1 (knob deg / count)  -->> 6.5 microns / count --->>> 6.5 urad / count

Distance from the 45 deg turning mirror to the QPD silicon surface is 23 cm. Distance between knob tip and fixed pivot point is ~4 cm. 1 knob turn = 0.01" = 0.254 mm = 0.254/40 radians of mirror angle.

So 360 deg of knob gives 2*0.254/40 = 0.012 radians of beam angle = 0.012 * 230 mm ~2.3 mm of beam spot motion. Or 6.4 microns of translation / deg of knob.

The distance from the face of the laser to the QPD is 96 cm.

The punchline is that the laser shows a level of noise which has a similar shape to what's seen at LLO, but 10x lower.

The noise at 0.05 - 0.2 Hz is ~2-3x worse than the PR3 at LLO. Not sure if this is inherent to the HeNe or the wind in our setup.

Attachment 1: oplev1103P.png
Attachment 2: L1-ISI_SUS_ODC_FC496F_SPECTRUM-1113523216-86400.png
11233   Wed Apr 22 11:21:51 2015 SteveUpdateOptical LeversBS & PRM oplevs are back to normal

BS & PRM oplev is restored. Note: the F -150 lens was removed right after the first turning mirror from the laser. This helped Rana to get small spot on the qpd.

It also means that the oplev paths are somewhat different now.

11344   Wed Jun 3 11:55:52 2015 SteveUpdateOptical LeversPRM-BS oplev

I'm getting ready change the Newport Ultima U100-AC to SS-Polaris-K1  LOW DRIFT MIRROR MOUNTS

Note: there is only one lens in the PRM lunching path (  only realized later ) , so the spots are large ~ 3 mm at PRM qpd and ~4.5 mm at BS qpd

The spots are well centered.

Atm3,  the spots were well centered yesterday ( the PRM is misaligned in pitch and retsore does not work today )

Attachment 1: PRM-BS_oplEr_noLenses.png
Attachment 2: PRM-BSopl_3jun2015.jpg
Attachment 3: opServos.png
Attachment 4: 10d_trend_opl.png
Attachment 5: opl_trend_40d.png
11766   Mon Nov 16 11:48:34 2015 yutaroUpdateOptical LeversBeam centering for the oplev of ETMY

[yutaro, ericq]

We made the beam spot on QPD for the oplev of ETMY centered by changing the orientation of the mirror just before the QPD.

Before doing this, we ran dithering for Y arm and froze the output of ASS for Y arm.

11783   Wed Nov 18 17:32:36 2015 yutaroUpdateOptical LeversBeam centering for the oplev of ITMY

[yutaro, Koji]

We made the beam spot on QPD for the oplev of ITMY centered by changing the orientation of the mirror just before the QPD.

Before doing this, we ran dithering for Y arm and froze the output of ASS for Y arm.

11785   Wed Nov 18 22:26:33 2015 yutaroUpdateOptical LeversCalibration of oplevs for ITMY/ETMY

Based on elog 1403, I calibrated the oplevs for ITMY/ETMY.

Summary of this method is following:

We lock an arm, and slightly misalign one mirror of the arm. Then, the transmission of the arm starts to decrease quadratically as the misalign angle of the mirror changes. Here, how much the transmission decreases in terms of the misalign angle is determined by geometry of optics, so we can see how much the angle really changes from this quadratic curve.

RESULTS

These are the relationship between misalign angles measured by oplev (the units are based on the calibration for now) and transmission power.

(I updated following figures on Nov 19 2015. You can find the figures I attached once here in the zipped folder attached.)

According to this measurement, ratio of the calibration factor derived with this measurement (NEW) and the calibration factor for now (OLD), i.e. NEW/OLD was:

ETMY_PIT: 5.0265  --->> 5.3922 (without an outlier; the outlier I removed is shown in the figure in zipped folder attached.)

ETMY_YAW: 4.6205

ITMY_PIT: 1.5010

ITMY_YAW: 1.2970

This results show that calibration of oplevs for ITMY is kind of OK, but that for ETMY is so BAD and the calibration factors should be updated.

NOTE

The calibration factors of the oplevs for ETMY/ITMY are   NOT UPDATED YET.  I updated on Dec 11, 2015

If these results are reliable, I will update them tomorrow.

Attachment 1: calib_etmypit2.pdf
Attachment 2: calib_etmyyaw2.pdf
Attachment 3: calib_itmypit2.pdf
Attachment 4: calib_itmyyaw2.pdf
Attachment 5: calib_oplev.zip
11787   Wed Nov 18 23:40:01 2015 ranaUpdateOptical LeversCalibration of oplevs for ITMY/ETMY

OMG. Please try to use larger fonts and PDF so that we can read the plots.

 Quote: Based on elog 1403, I calibrated the oplevs for ITMY/ETMY.

I'm not sure that these calibration measurements are reliable. I would feel better if Steve can confirm them using our low accuracy method of moving the QPD by 1 mm and doing trigonometry.

11790   Thu Nov 19 16:06:54 2015 yutaroUpdateOptical LeversCalibration of oplevs for ITMY/ETMY

I'm sorry. I will be careful about that. And I updated the plots in elog 11785.

 Quote: OMG. Please try to use larger fonts and PDF so that we can read the plots.

Quote:
 Quote: Based on elog 1403, I calibrated the oplevs for ITMY/ETMY.

I'm not sure that these calibration measurements are reliable. I would feel better if Steve can confirm them using our low accuracy method of moving the QPD by 1 mm and doing trigonometry.

In this morning, Steve and I looked at the ETMY table and we found that the measurement you suggested might interfere with other optics or detectors because of space constraint. So, before doing this measurement, I roughly estimated the calibration factors for ETMY oplev by using the rough value of the arm length of the optical lever and the beam width of the light just before the QPD.

How I got the arm length and the beam width:

I measured the length of the optical path between ETMY and the QPD. Then I measured the beam width with an iris to screen the beam. To get the beam width from the decrease of the power of the beam detected by QPD, I used this formula: $P/P_{max}=1-\exp(-2r^2/w^2)$.

Then I got:   (arm length) = 1.8 +/-0.2 m,    w= 0.56 +/- 0.5 mm.

How I estimated the calibration factors from these:

The calibration factors (such as C1:SUS-ETMY_OL_PIT_CALIB; (real angle) / (normalized output of QPDXorY)) can be calculated with: $\sqrt{\pi/32}\times w\,/\,(\mathrm{arm\,length})$. Then, I got

$130\,\pm\,20 \,\mu \mathrm{rad}$,

though the calibration factors, C1:SUS-ETMY_OL_PIT_CALIB C1:SUS-ETMY_OL_YAW_CALIB, right now are 26.0 and 31.0, respectively. (If I express this in the same way as elog 11785, 5.0 and 4.2 for ETMY_PIT and ETMY_YAW, respectively. they are consistent with yesterday's results.)

I believe that the calibration factors I estimated today are not different from the true values by a factor of 2 or something, so this estimation indicates that the oplev calibration measurements I did yesterday are reliable, at least for the oplev for ETMY.

11805   Tue Nov 24 11:18:47 2015 yutaroUpdateOptical LeversBeam centering for the oplev of ITMY

I made the beam spot on QPD for the oplev of ITMY centered by changing the orientation of the mirror just before the QPD.

Before doing this, I ran dithering for Y arm and froze the output of ASS for Y arm.

11831   Tue Dec 1 11:26:23 2015 yutaroUpdateOptical LeversCalibration of oplevs for ITMX/ETMX

With the same method as reported in elog 11785, I calibrated oplevs for ITMX/ETMX.

RESULTS

According to this measurement, ratio of the calibration factor derived with this measurement (NEW) and the calibration factor for now (OLD), i.e. NEW/OLD was:

ETMX_PIT: 4.470

ETMX_YAW: 2.5970

ITMX_PIT: (-)1.1102

ITMX_YAW: 1.8173

NOTE

The calibration factors of the oplevs for ETMY/ITMY are   NOT UPDATED YET. I updated on Dec 11, 2015

Attachment 1: ep_l.pdf
Attachment 2: ey_l.pdf
Attachment 3: ip_l.pdf
Attachment 4: iy_l.pdf
11842   Thu Dec 3 06:15:38 2015 ranaUpdateOptical LeversCalibration of oplevs for ITMX/ETMX

http://blogs.mathworks.com/loren/2007/12/11/making-pretty-graphs/

11843   Thu Dec 3 10:05:07 2015 yutaroUpdateOptical LeversCalibration of oplevs for ITMX/ETMX

I updated the figures. I think it's easier to read now.

11875   Fri Dec 11 16:16:36 2015 yutaroUpdateOptical LeversCalibration of oplevs for ITMX/ETMX

Based on calibration measurement I have done (elog 11785, 11831), I updated calibration factors of oplevs on medm screen as follows. Not to change loop gain oplev servo, I also changed oplev servo gain.

C1:SUS-ETMX_OL_PIT_CALIB, C1:SUS-ETMX_OL_PIT_GAIN

(45.1,16) => (200,3.5)

C1:SUS-ETMX_OL_YAW_CALIB, C1:SUS-ETMX_OL_YAW_GAIN

(85.6,8) => (222,3.0)

C1:SUS-ETMY_OL_PIT_CALIB, C1:SUS-ETMY_OL_PIT_GAIN

(26,-16) => (140,-3.0)

C1:SUS-ETMY_OL_YAW_CALIB, C1:SUS-ETMY_OL_YAW_GAIN

(31,-21) => (143,-4.5)

C1:SUS-ITMX_OL_PIT_CALIB, C1:SUS-ITMX_OL_PIT_GAIN

(110,8) => (122,7.2)

C1:SUS-ITMX_OL_YAW_CALIB, C1:SUS-ITMX_OL_YAW_GAIN

(81,-11) => (147,-6)

C1:SUS-ITMY_OL_PIT_CALIB, C1:SUS-ITMY_OL_PIT_GAIN

(159,15) => (239,10)

C1:SUS-ITMY_OL_YAW_CALIB, C1:SUS-ITMY_OL_YAW_GAIN

(174,-21) => (226,-16)

11881   Mon Dec 14 23:49:03 2015 ericqUpdateOptical LeversCalibration of oplevs for ITMX/ETMX
 Quote: Based on calibration measurement I have done (elog 11785, 11831), I updated calibration factors of oplevs on medm screen as follows. Not to change loop gain oplev servo, I also changed oplev servo gain.

After making sure that the upper UGFs were properly in place, I saved these settings to the SDF files. Thanks Yutaro!

12746   Mon Jan 23 15:16:52 2017 gautamUpdateOptical LeversETMY Oplev HeNe needs to be replaced

On the control room monitors, I noticed that the IR TEM00 spot was moving around rather a lot in the Y arm. The last time this happened had something to do with the ETMY Oplev, so I took a look at the 30 day trend of the QPD sum, and saw that it was decaying steeply (Steve will update with a long term trend plot shortly). I noticed the RIN also seemed rather high, judging by how much the EPICS channel reading for the QPD sum was jumping around. Attached are the RIN spectra, taken with the OL spot well centered on the QPD and the arms locked to IR. Steve will swap the laser out if it is indeed the cluprit.

Attachment 1: ETMY_Oplev.pdf
12747   Mon Jan 23 17:24:26 2017 SteveUpdateOptical LeversETMY Oplev HeNe is running hot

ETMY He/Ne 1103P  body temp is  ~45 C The laser was seated loosely  in the V-mount with black rubber padding.

The enclosure has a stinky plastic smell from this black plastic. This laser was installed on Oct 5, 2016 See 1 year plot.

Oplev servo turned off. Thermocouple attached to the He/Ne

It will be replaced tomorrow morning.

 Quote: On the control room monitors, I noticed that the IR TEM00 spot was moving around rather a lot in the Y arm. The last time this happened had something to do with the ETMY Oplev, so I took a look at the 30 day trend of the QPD sum, and saw that it was decaying steeply (Steve will update with a long term trend plot shortly). I noticed the RIN also seemed rather high, judging by how much the EPICS channel reading for the QPD sum was jumping around. Attached are the RIN spectra, taken with the OL spot well centered on the QPD and the arms locked to IR. Steve will swap the laser out if it is indeed the cluprit.

Attachment 1: ETMY_oplev__lasers.png
12750   Tue Jan 24 17:52:15 2017 CraigUpdateOptical LeversETMY Oplev HeNe is replaced

Steve, Craig, Gautam

Today Steve replaced the ETMY He/Ne sr P919645 OpLev laser with sr P947049 and Craig realigned it using a new AR coated lenses.

Attached are the RIN of the OpLev QPD Sum channels.  The ETMY OpLev RIN is much lower than when Gautam took the same measurement yesterday.

Also attached are the pitch and yaw OLG TFs to ensure we still have acceptable phase margins at the UGF.

The last three plots show the optical layout of the ETMY OpLev, a QPD reflection blocker we added to the table, and green light to ETMY not being blocked by any changes to the OpLev.

Quote:

ETMY He/Ne body temp is  ~45 C The laser was seated loosely  in the V-mount with black rubber padding.

The enclosure has a stinky plastic smell from this black plastic. This laser was installed on Oct 5, 2016 See 1 year plot.

Oplev servo turned off. Thermocouple attached to the He/Ne

It will be replaced tomorrow morning.

 Quote: On the control room monitors, I noticed that the IR TEM00 spot was moving around rather a lot in the Y arm. The last time this happened had something to do with the ETMY Oplev, so I took a look at the 30 day trend of the QPD sum, and saw that it was decaying steeply (Steve will update with a long term trend plot shortly). I noticed the RIN also seemed rather high, judging by how much the EPICS channel reading for the QPD sum was jumping around. Attached are the RIN spectra, taken with the OL spot well centered on the QPD and the arms locked to IR. Steve will swap the laser out if it is indeed the cluprit.

Attachment 1: OpLevRIN24Jan2017.pdf
Attachment 2: ETMYpit_24Jan2017.pdf
Attachment 3: ETMYyaw_24Jan2017.pdf
Attachment 4: IMG_3510.JPG
Attachment 5: IMG_3513.JPG
Attachment 6: IMG_3514.JPG
12858   Wed Mar 1 08:28:04 2017 SteveUpdateOptical Leversoplev laser RIN

Gautam and Steve,

New JDSU 1103P HeNe oplev laser RIN was measured on the SP table with cover on.

This is the beginning of an effort to improve oplev laser noise.

Attachment 1: RIN_1103P.png
Attachment 2: RIN_HeNe.png
12863   Thu Mar 2 13:59:04 2017 SteveUpdateOptical Leversoplev laser RIN

The laser got much better at low frequency as it warmed up. This laser is almost as good as the electronics?

Dark noise cal was the same today as it was 2 days ago.

Attachment 1: 1103P@2d.png
ELOG V3.1.3-