40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Authordown Type Category Subject
  65   Wed May 23 15:17:30 2018 calum and Luis MechanicsElectric Field MeterEfm 0003 he test - yes again

This time we torqued to 185 in lbs Cf. before 180 in lbs 

starting level pump down was (after 1 re-start and vent) = 1 e-10 torr l/s with pressure 6.2e-3 Torr

Then he into bag 

stayed flat for ~ 1min after 1st helium

Highest num got was  5e-10   torr l/s after 2 min


Calum and Luis

After the success of the Helium Leak Test, we continue on fill EFM 003 with Neon 1cfm for 2min 15sec, video is also attached.


Attachment 1: EFM3_Helium_Leak_Test.mov
Attachment 2: EFM3_Helium_Leak_Test.mp4
Attachment 3: EFM3_Neon_fill.mov
Attachment 4: EFM3_Neon_fill.mp4
  53   Mon May 14 10:57:43 2018 Stephen AppertProgressElectric Field MeterMechanical Part History and Serial Numbers

WIP (photos will be posted, more information will be gathered)

  1. 14 May 2018: Stephen and Luis gathered serial numbers from Cube 2 / Cube 3 / spares (all of which were Class A baked in Bake-9049) (ICS records will be updated)
    1. Cube 3
      1. D1800043-v1 SN003
      2. D1800032-v2 SN013
      3. D1800032-v2 SN004
      4. D1800032-v2 SN001
      5. D1800032-v2 SN012
      6. D1800054-v1 SN002
      7. Cube 408003 unserialized
    2. Cube 2
      1. D1800043-v1 SN004
      2. D1800032-v2 SN009
      3. D1800032-v2 SN010
      4. D1800032-v2 SN002
      5. D1800032-v2 SN014
      6. D1800054-v1 SN003
      7. Cube 408003 unserialized
    3. Spares
      1. D1800032-v2 SN011
      2. D1800032-v2 SN007
  21   Thu Oct 13 16:06:34 2016 StephenSummaryPMC WorkTesting of Spring Plate for PMC Spacer Assy


The purpose of this test was to evaluate a spring plate in a custom optic mount design which will be deployed in the reworked and upgraded PMC Spacer Assy per D1600270.

Summary of Results (Fit)

Mechanical inspection of the fabricated showed conformance to manufacturing specifications. Assembly of the Fit Test Interface Assy D1600398 in the nominal configuration was successful.

  • The primary source of assembly clearance was the 0.030” radial gap between the mirror and the 1in. Mirror MT.
  • Secondarily, assembly clearance was evident in the clearance bore bolt circle in the 1in. Mirror MT. for the M2.5 x 0.45 SHCS.

Some additional consideration (Tooling? Interfacing part?) may be necessary to combat these sources of “slop” and permit repeatable assembly.

Summary of Results (Holding Force)

The Fit Test Interface Assy D1600398 was laid flat on the work bench with the normal axis of the mirror vertical. The force required to overcome the static friction for a given spring plate defection and induce macroscopic translation was evaluated as follows:

  • 0.050” deflection (nominal): 6 +/- 0.5 ounces of force (1.7 newtons)
  • 0.030” deflection: 4 +/- 0.5 ounces of force (1.1 newtons)
  • No spring plate: no measurement, as this force was too small for this experimental set-up

In comparison, the weight of the optic is estimated to contribute a force of 1.6E-2 newtons in the nominal orientation. The optic did not sag in the mount when held in the nominal configuration and orientation for 2 hours.

In shipping configuration, the set screws were found to couple rigidly to the barrel of the optic and provide sufficient static friction to withstand jarring motions. The design seems to be sound from a shipping point of view.

Summary of Results (Comparison with COTS)

Two Commercial Off-The-Shelf (COTS) optic mounts were investigated. Barrel contact points, namely two flats and a preloading point-contact plunger, were used in conjunction with a spring plate. The assembly was rigidly coupled with high static friction constraining all degrees of freedom.

Perhaps barrel contact points should be employed in the LIGO design.



Full Description of Experiment



COTS Spring Plate Mounts

Two models of Commercial Off-The-Shelf (COTS) Low Outgassing optic mounts from Newport which provide axial clamping using the COTS 906919-02 Mirror Mount Spring Plate were investigated. Both use the Spring Plate in conjunction with barrel contact points, namely two flats and a preloading point-contact plunger.

An optic is loaded into these mounts by using the barrel to depress the plunger, then tilting the optic into flush face contact with a retaining lip that is integral to the mount. The plunger then pushes the optic into its seat on the two flats (visible contacting the right hand site in the image below). Subsequently, the blade spring is bolted to the exposed face, and the assembly is rigidly coupled with high static friction constraining all degrees of freedom.

Optic Mount models are:

  • NewFocus (Newport) 902817-04 (9817-6-NI-K) (pictured below, with dirty optic)
  • NewFocus (Newport) 902816-04 (9814-6-NI-K)



The parts procured for the Fit Test Interface Assy D1600398-v1 were received in good condition. Using micrometers, calipers, and pin gages, Stephen employed partial inspection of mating and critical features to establish that the parts were made to specification by the vendor. The parts consisted of the COTS 906919-02 Mirror Mount Spring Plate (Qty 25, New Focus / Newport), the D1600233-v1 1in. Mirror MT. (Qty 1, ProtoLabs), the D1600397-v1 Base Plate (Qty 1, ProtoLabs) and assorted COTS hardware and fasteners.

The only item worth raising from this inspection is the difficulty of inspecting the 1.010” Diameter pocket in the D1600397-v1 base plate. No accurate measurement could be made due to the nominal .030” high shoulder, the nominal .0075” machine tool radius, and the un-deburred lip, all of which limited the contact area and precision for the calipers. A fit check of the PZT showed that the pocket was large enough to insert the PZT, and this was taken to be sufficient to “Pass” the size dimension on this feature.


To assemble the Fit Test Interface Assy, the following procedure was followed:

  1. The COTS 906919-02 Mirror Mount Spring Plate was bolted to the D1600233-v1 1in. Mirror MT. and the subassembly was placed flat on the workbench with the spring plate on the table side.
  2. The 25 mm Diameter x 5 mm Thick mirror was laid flat on top of the spring plate within the 1in. Mirror Mount, with the HR-coated side facing away from the table. Now, the AR-coated side was in contact with the Spring Plate.
  3. The M2 x 0.4 set screws were tightened onto the barrel of the mirror until rigidly coupled, with the mirror centered by eye in the 1in. Mirror Mount. THIS WAS NOT A VERY PRECISE CENTERING OPERATION, but using a pin gage as a spacer, I was able to position the optic within 0.005” of the center of the mount.
  4. The 1in. Mirror Mount was lowered toward the surface of the D1600397-v1 Base Plate, until the HR-coated side was registering on a single plane with three locations of point contact.

  1.  The M2.5 x 0.45 SHCS were tightened by a couple of turns, indexing the 1in. Mirror Mount BUT NOT LOADING THE SCREWS. The 1in. Mirror Mount was NOT in contact with the Base Plate. THE SLOP IN THE CLEARANCE BORES DID NOT PERMIT PRECISE CENTERING AT THIS STAGE.
  2. The set screws were loosened and retracted into the threaded bores to prevent any possible contact with the barrel of the mirror.
  3. The 1in. Mirror Mount was bolted to the Base plate using the M2.5 x 0.45 SHCS with tightening conducted in stages, so that each tab was loaded approximately 1 mm at a time. A final torque of 5 in*lb was applied, per T1100066 (interpolation between #2-56 and #4-40).

Note that the mirror used in this experiment was a flat mirror removed from PMC 10. See item 36 of D1001955-v2 Assembly Drawing.


Using the Fit Test Interface Assy D1600398 and a 36 ounce Jonard Compression/Tension Force Guage, the holding force of the 906919-02 Mirror Mount Spring Plate was tested.

This holding force was found to hold the optic tightly without macroscopic translation in the nominal mount configuration (0.050” axial deflection on spring plate) until acted upon by approximately 6 ounces of force (converted, about 1.7 newtons). This force was applied approximately perpendicular to points on the barrel of the mirror near the face opposite the 3-point contact plane.

SEE 50thou Holding Force.MOV

In contrast to the nominal 0.050” of deflection on the spring plate, under an axial deflection of 0.030” approximately 4 ounces of force (1.1 newtons) were required to overcome the static friction and induce macroscopic translation. This set-up utilized precise shims to reduce the deflection, as shown below.

SEE 30thou Holding Force.MOV

The force required to induce macroscopic translation without the spring plate installed was too small to be measured with the same set-up.

SEE NoSpring Holding Force.MOV

The weight of the optic contributes a force of 1.6E-2 newtons in the nominal orientation, using a calculated volume of 0.78 cm^3 and an estimate density of 2.2 grams per cm^3. The optic was set in the Interface Assy for 2 hours under the nominal configuration, and no gravitational sag was observed (using a pin gage as a probe).


Evaluation of Shipping Configuration

In order to push the limits of the holding force of the mount for shipping purposes, the mount was carefully subjected to a repeated jarring motion (held with one hand and "clapped" firmly into the other) with the set screws driven tightly into the barrels. The contact provided by the set screws and the spring plate in conjunction was sufficient that the optic did not macroscopically move (using a pin gage as a probe). Meanwhile, when the optic was held only by the spring plate and the mount was subjected to the same jarring motion, the optic did macroscopically move. The set screw contact on the barrel is very much necessary for shipping of the optic in place within this mount in order to provide sufficient static friction to rigidly couple the optic to the mount.




Attachment 1: image3.JPG
Attachment 2: image2.JPG
Attachment 3: image1.JPG
Attachment 4: image1.JPG
Attachment 5: image5.JPG
Attachment 6: image11.JPG
Attachment 7: 30thou_Holding_Force.MOV
Attachment 8: 50thou_Holding_Force.MOV
Attachment 9: NoSpring_Holding_Force.MOV
Attachment 10: image21.JPG
Attachment 12: image22.JPG
  33   Thu Dec 1 18:12:17 2016 StephenHow ToCASI BRDFGigE Camera: First Set-Up


I was successful in connecting two Basler GigE cameras to my personal laptop and viewing/saving images using pylon, the UI downloaded from the Basler website here. The details of the cameras are documented below:

  • Basler ace acA640-100gm, same as used at sites, borrowed from Johannes at 40 m. Equivalent to acA640-120gm, which is the current Basler designation of this camera. ~$500 for qty of 1, 3 week lead time.
  • Basler scout scA1400-17gc, originally purchased by OpLev design team, leftover from aLIGO efforts, borrowed from Eric/Gabrielle in West Bridge. ~$3300 for qty of 1, 3-4 week lead time.

There will be more to follow in subsequent log entries regarding integration into the CASI BRDF measurement system.

Some Helpful Resources

aLIGO GigE camera layout and usage. Joe Betzwieser from LLO has a guide to the camera usage and system set-up at the sites located at T1300202.

Basler set-up guide. Basler has a very good set up guide which covers details and some troubleshooting. Accessed at this link, by navigating to [ Support > Downloads > Current pylon Windows ]

Description of Set-Up

Once all of the materials were in hand, a PoE injector (TP-Link TL-POE150S; 40m loan) was connected in series between my laptop and the camera in question. I also had success using the power supply supplied with the camera and a direct ethernet connection to the laptop. A lens (Rainbow, 50mm focal length, C mount, 2/3" to 1" aperture, 1:1.8 image; 40m loan)  was installed on the camera, and the focus ring was adjusted as needed (no iris adjustment required).

The pylon IP Configurator was used to force IP addresses at the onset (Static IP used for the ace and DHCP used for the scout, based on defaults upon opening). The camera status was "OK", then the pylon Viewer was opened, the camera was opened (may need to refresh the list) and placed in Continuous Mode for image collection (ctrl-S to save an image) See the Basler set-up guide (link at the top of this post) for full details of camera set-up.

Difficulty with Set-Up

The only real difficulty I had turned out to be due to exceeding the bandwidth of the set-up. The common error was:

Error: 0xe1000014 "The buffer was incompletely grabbed. This can be caused by performance problems of the network hardware used, i.e. network adapter, switch, or ethernet cable. To fix this, try increasing the camera's Inter-Packet Delay in the Transport Layer category to reduce the required bandwidth, and adjust the camera's Packet Size setting to the highest supported frame size."

Accessing Transport Layer in the camera drop-down and following the recommendations eliminated the bandwidth issues. I was confused at first because there is a second Transport Layer category that lives outside of the camera drop-down. This one is not useful.

Better yet, following Joe's recommendations in "Notes on camera settings" on page 11 of T1300202 (link at the top of this post) made for a seamless camera run.


The color image from the scout camera was taken from about 3m distance with my unsteady hand holding the camera.

Link to scA1400-17gc_image_from_test_office_emergency_map_01.bmp

The black and white images from the ace camera were taken from the same 3m distance, also mounted in an unsteady hand. The image tagged 02 has an increased Gain (250 --> 700) which increased the contrast while causing the image to be less sharp and detailed.

Link to acA640-100gm_image_from_test_office_light_switch_01.bmp

Link to acA640-100gm_image_from_test_office_light_switch_02.bmp

Admittedly, these images don't really mean anything. There will be more to follow in subsequent log entries regarding integration into the CASI BRDF measurement system.



Attachment 1: scA1400-17gc_image_from_test_office_emergency_map_01.bmp
Attachment 2: acA640-100gm_image_from_test_office_light_switch_01.bmp
Attachment 3: acA640-100gm_image_from_test_office_light_switch_02.bmp
Attachment 4: scA1400-17gc_image_from_test_office_emergency_map_01.bmp
Attachment 5: acA640-100gm_image_from_test_office_light_switch_01.bmp
Attachment 6: acA640-100gm_image_from_test_office_light_switch_02.bmp
  35   Thu Jan 12 07:36:55 2017 StephenProgressCASI BRDFGigE Camera: Photos of Oxidized SSTL

This log entry reflects on recent efforts to image the 1064nm spot on samples undergoing BRDF measurement within the CIT CASI scatterometer. The cameras used are (reiterating from eLOG ENG_Labs/33)

  • Basler ace acA640-100gm, same as used at sites, borrowed from Johannes at 40 m. Equivalent to acA640-120gm, which is the current Basler designation of this camera.
  • Basler scout scA1400-17gc, originally purchased by OpLev design team, leftover from aLIGO efforts, borrowed from Eric/Gabrielle in West Bridge.

The set up and measurement is described by the following procedure:

  1. A sample of oxidized stainless steel was found in the lab and taped to an existing sample mount using kapton tape.
  2. Images were taken with the room lights on and then without the room lights.
  3. Imaging settings were maintained for each photo taken with an individual camera, but gain values and packet size varied between cameras.

Hardware for the cameras included:

  • a lens with adjustable focus (Rainbow, 50mm focal length, C mount, 2/3" to 1" aperture, 1:1.8 image; 40m loan)
  • where indicated, a ~70% transmissive bandpass filter (Newport 10LF25-1064).
  • mounting post with fixed clamping platform (will add photo), approximately 1 meter from the sample.

The acquired images may be summarized by the following points:

  • The 1064nm light was represented by the color scout camera as white-ish pixels with a bluish tinge.
  • The scout camera appeared to have a number of dead pixels (someone with more camera expertise may have better terminology; I am referring to the scattered red and blue pixels that do not appear to be real light).
  • The focal length of the two cameras was different, hence the difference in perceived spot size.
  • The bandpass filter reduced intensity of the image and, with the light off, did not seem to provide any useful noise cancelling.

Image 07: Lights on, scout OpLev GigE Camera Link to casi_test_07_laptop_lights_high_exposure_10_mw_high_gain.bmp

Image 08: Lights off, scout OpLev GigE Camera Link to casi_test_08_no_lights_high_exposure_10_mw_high_gain.bmp

Image 09 Lights off, bandpass filter, scout OpLev GigE Camera Link to casi_test_09_no_lights_high_exposure_10_mw_high_gain_bandpass_filter.bmp

Image 13: Lights on, ace Site GigE Camera Link to casi_test_13_site_gige_foyer_light_auto_exposure_10_mw_auto_gain.bmp

Image 15: Lights off, ace Site GigE Camera Link to casi_test_15_site_gige_foyer_light_auto_exposure_10_mw_100_gain.bmp

Image 19: Lights off, bandpass filter, ace Site GigE Camera Link to casi_test_19_site_gige_no_light_auto_exposure_10_mw_100_gain_bandpass_filter.bmp

Attachment 1: casi_test_07_laptop_lights_high_exposure_10_mw_high_gain.bmp
Attachment 2: casi_test_08_no_lights_high_exposure_10_mw_high_gain.bmp
Attachment 3: casi_test_13_site_gige_foyer_light_auto_exposure_10_mw_auto_gain.bmp
Attachment 4: casi_test_15_site_gige_foyer_light_auto_exposure_10_mw_100_gain.bmp
Attachment 5: casi_test_09_no_lights_high_exposure_10_mw_high_gain_bandpass_filter.bmp
Attachment 6: casi_test_19_site_gige_no_light_auto_exposure_10_mw_100_gain_bandpass_filter.bmp
  110   Fri Feb 1 16:30:52 2019 StephenProgressModal TestingVMD: non-excitation characterization

Contributors: Craig, Alexei, Stephen

Project: VMD Testing (BK Connect)

Summary: Non-excitation measurements by laser vibrometer were successful. We will work on curve fitting the spectra to extract Qs, but this technique seems to work well.


The following measurements have been made:

  • Bolted-base non-excitation measurement in the transverse direction
  • Glued-base non-excitation measurement in the transverse direction
  • Glued-base non-excitation measurement in the longitudinal direction

Remember, our bolted-base excitation measurement in the longitudinal direction was poor, so we did not feel like the non-excitation measurement would be informative.

We made measurements of a field calibrator reference, which oscillates at 159.2 Hz at a velocity of 10 m/s. We measured the velocity of this peak using a separate setup within our VMD Testing project, using 2 vibrometers. We adjusted the sensitivity of each vibrometer in our hardware table using the proportional relationship:

[Old Sensitivity * (Measured Velocity / Nominal Velocity)] = [New Sensitivity]

We then collected non-excitation measurements in two directions at once using the two calibrated vibrometers, and then swapped the response direction of each vibrometer to make a second measurement. There was good agreement between the two vibrometers, and the technique seemed very promising for resolving the peaks fully.

We investigated comparison with the autospectrum of the excitation measurements, and we'll tie up lose ends on that - seems like a visual check of the shape and the prominence of the resonance peak will be a good way to confirm that this technique is working.

Next Steps

  1. Craig - Finalize plots of non-excitation measurements and push to next rev of T1800474
  2. Craig - Look into matlab curve fitting toolbox - looking to extract Q from noisy non-excitation measurements


None to share this time - oops!

  113   Mon Feb 4 16:08:00 2019 StephenProgressOCF CavityEddy Current Damping - Mechanical Design and Magnet Characterization

Contributors: Stephen, Rich

Project: Optical Cavity Eddy Current Damping (see 120)

Summary: Mechanical design shared with Rich (Dean unavailable). Quotes obtained from Proto Labs for machined parts. Surface Field of Ni-plated ND42 magnets was measured and compared with magnets from prototype.


Mechanical Design

  • Looked at D1900070 OCF ECD design with Rich, Dean was out today otherwise would've met with him as well. We discussed adjustment degrees of freedom, assembly technique, vacuum compatibility, and came away with no snags or issues.
  • I am working on posting the minimum design documentation to share the design and potentially even move toward fabrication if needed (.stp files exported for quotations, .easm solid models for visualization and docuementation including dimensions, BOM, etc). Formal part drawings are outstanding at this time.

Characterization of Magnets

  • Magnets have arrived from K&J Magnetics (P/N SD64-OUT, see C1900105). Material is Ni-plated ND42 - nominal surface field is ~5000 Gauss.
  • The nickel plating looks very bright and uniform, and the dimensions are very consistent (and in conformance with manufacturer spec)
  • The surface field parameter was inspected with Rich using a PCE Hall Effect probe (AC/DC MAGNETIC METER Model: PCE-MFM 3000) within 5% of nominal on 5 articles of this SD64-OUT magnet.
  • For comparison, one of the magnets from the ECD prototype (material and sourcing unknown, borrowed from Calum) was found to have surface field ~3000 Gauss.

Modal Testing

  • With Alexei on spring break, we are still working toward updating plots and findings from ENG_Labs log 120. No progress to report there, but success

Next Steps:

  1. Bob, Calum, Dean, Rich, Stephen will meet to discuss the OCF path ahead and as part of that discussion will make a plan for fabricating and implementing the ECD.
  2. E1000193 OCF Log item OCF001, Acrylite-coated optical fiber S1900194, is done with C+B processing (approval?) and might need to go into an OCF cavity before the ECD is ready.



  121   Tue Feb 26 11:04:27 2019 StephenProgressModal TestingOptical Cavity Eddy Current Damping

Looking at this work, the next step will be to re-generate plots with (1) improved resolution [Q should be resolved with (3dB width) > (10*resolution), if possible!] and (2) on longitudinal scales (either physical units or dB) to enable qualitative visual comparison. (also, I think the longitudinal movies you took didn't get posted?)

The following step would be to make a quantitative comparison of Q - see below table, intended as a mockup of the important information to summarize.

The key outcome of this effort is assessing whether the prototype damping scheme is working, and if so, what degrees of freedom should be incorporated into the final design of the damper. Hope this helps clarify why these requests are being made!

Comparison Table Mockup
Resonance Frequency (Hz) Prominent Direction (Long/Tran) Mode Shape Description Measurement technique Undamped 3 dB width (Hz) Undamped Q Best damped 3 dB width (Hz) Best damped Q

Best damping parameters

Resolution of FFT (Hz)
2.337 Transverse  Primary Pendulum Excitation, non-excitation .0163   .0241   1.5 mm spacing, 4 magnets, V .0125
2.438 or 2.425 Longitudinal Primary  Pendulum Excitation, non-excitation .0173   .0332   1.5 mm spacing, 4 magnets, V .0125
13.338 or w/e is next     Excitation, non-excitation (?)            

Work in Progress

Contributors: Alexei, Stephen

Project: Optical Cavity Eddy Current Damping Mode Testing (BK Connect)

Summary: Non-excitation, transverse, and longitudinal excitation measurements by laser vibrometer (OMC and Ometron).  Recordings taken and fitted with fft spectrum to compare damping effects of different magnet configurations used for eddy current damping.


The following measurements have been made:

  • No-excitation measurement in the transverse/longitudinal direction
  • Longitudinal excitation measurement undamped / 1.5mm damping / 3mm damping / 2 magnet centerline damping
  • Transverse excitation measurement undamped / 1.5mm damping / 3mm damping / 2 magnet centerline damping
  • Transverse/Longitudinal huddle tests

The pendulum mode of the optical cavity assembly was recorded when the assembly was undamped, damped by 4 magnets oriented at 45 degrees from the horizontal and with 2 magnets oriented along the centerline.  Distance of the magnets from the copper sheeting of the cavity was also tested (magnets kept at distance of 1.5mm and 3mm).

Note: OMC laser vibrometer has issue of signal LED having gone out. Prompted huddle tests.

Next Steps

  1. Alexei/Stephen - Finalize documentation from attached plots.  Calculate and compare Q's from fft spectra.


See attached


  220   Thu Nov 21 10:53:59 2019 StephenLab InfrastructureClean and BakeElectrical Check of new Epoxy Curing "Wait Test" Oven

RichA, StephenA, LizN 12 November 2019 (catching up after-the-fact)

A new simple oven has been procured which will be dedicated to dirty operations like the "Wait Test" (in other words, elevated temperature checks that proportions and procedures of epoxy mixing have been adequate mixing of epoxy, such as EP30-2 - ref. T1300322 section I.5).

This oven has been property tagged and Liz was planning to help input into the PCS system - C32329 is the property tag but currently there is a conflict in PCS; here is the conflicting entry https://services.ligo-la.caltech.edu/Inventory/history.php?recid=1590&invtype=cit_noncap

Rich has reviewed the electrical characteristics of the toaster (Power = 1150 W per manufacturer spec, so current drawn will be < 10 A, and therefore no issue plugging into standard wall outlet) and has checked dis/continuity of ground and power at the plug. Rich has given the OK to proceed using this oven.

Photos show oven, property tag, and receipt.


Attachment 1: IMG_5994.JPG
Attachment 2: IMG_5995.JPG
Attachment 3: IMG_6008.JPG
  224   Thu Dec 12 11:16:03 2019 StephenProgressGeneralSR3 ROC Actuator photos

StephenA, various others :)

Sharing a link to photos of SR3 ROC Actuator efforts in various labs at CIT - others involved in various measurements are welcome to add their own photos here.


Related documents:

Notes about the lab setups:

  • In the lab at CIT, we make use of a type K thermocouple (Accuglass p/n 100770 with Hot Junction flat washer lug termination, aka 1/4-20 washer). Accuglass non-controlled print is attached.
    • This auxiliary thermocouple is not used in situ. This caused confusion as documented in FRS Ticket 10063. There is an internal temperature sensor native to the heater which is used.


Attachment 1: image3.JPG
Attachment 2: accuglass_type_k_thermocouple_with_flat_washer_6-103011.pdf
  234   Wed Feb 19 13:28:18 2020 StephenItems to BuyGeneralGigE Camera - IR Sensitivity improvements available


Stephen, Noah


It appears that Basler offers GigE cameras with over 2x improved sensitivity to the typical LIGO infrared laser wavelength. This camera is the "acA1300-60gmNIR" and it appears to be 2 to 5 times more sensitive at 1064 nm.

We do not have any of these cameras, and might want to consider getting our hands on one to evaluate its utility in lab settings (or perhaps even in site GigE camera installations).

Detailed Findings

As discussed in the Basler technical documentation, there are 3 different sensors that Basler packages into their cameras.

--> ref. https://www.baslerweb.com/en/vision-campus/camera-technology/nir-cameras/

"The NIR-optimized cameras with NIR-optimized 2 MP (CMV2000) and 4 MP (CMV4000) sensors from CMOSIS, or the 1.3 MP sensor (EV76C661) from e2V, still manage quantum efficiencies close to 40% in the 850nm range. Compared to non-NIR-optimized cameras, this represents a doubling of the sensitivity value at this wavelength."

Examining these sensors closer, the better QE at 1000 nm wavelength is from the 1.3 MP sensor (EV76C661) from e2V. This is notable because LIGO uses 1064 nm wavelength, and the highest QE reported in the datasheets is at 1000 nm.

The camera which uses this sensor is the "acA1300-60gmNIR" which is available in either C-mount lens interface, or CS-mount lens interface.

--> ref. https://www.baslerweb.com/en/products/cameras/area-scan-cameras/ace/aca1300-60gmnir/


Begin at a given camera's Basler webpage. See example below.

--> ref. https://www.baslerweb.com/en/sales-support/downloads/document-downloads/basler-ace-aca2000-50gmnir-emva-data/

Navigate to "Documents" tab and then to "EMVA Data". There are two attachments in this section:

  • the overview pdf, which gives a rundown of the specs of each camera and the cameras using each sensor
  • the sensor-specific pdf, which gives technical data from the tests collected for a number of articles of each sensor, which corresponds to the indicated sensor

By using the camera-specific pdf, you can identify the quantum efficiency at NIR wavelenghts up to 1000 nm.

Alternatively, if you know you want a specific sensor or specification, you can identify the cameras using the overview pdf, or using the Vision System Configurator

--> ref. https://www.baslerweb.com/en/products/tools/vision-system-configurator/#/selection/camera/

Next Steps

We'll use this log as a starting point to compile the resolutions, sensitivities, and any other parameters for each existing LIGO GigE camera and each possible improved camera.

We will also continue our work in identifying all of the necessary components that could help us construct a mobile setup which enables interchangeability of the various GigE cameras that are at our disposal (WIP).

  247   Thu Nov 19 15:55:45 2020 StephenProgressVacuumNuts and Rod for A+ FC Tube Support Stand

Stephen A, 2020 Nov 19

Ordered and received PO 75-S492380 including threaded rod and nut with 2"-12 thread.  These items are under consideration for A+ FC Tube Support Stand, particularly for use in weldment D2000445. Some observations:

  • Thread area seems very small, nuts seem very large - wonder how strong the interface is.
  • Pitch seems cumbersome - minutes may be necessary to install a nut in the middle of the thread.
  • External thread appears to have some small damaged areas. Thread of nut can run over these areas, but with increase in friction.
  • No apparent wobble or loosness of nut due to fit.
  • Nut appears to have a oily coating applied to the outer surfaces, but not to internal threads.

Also ordered were two McMaster offerings which could be used for rust inhibiting conversion coatings (formulations appear to be based on phosphoric acid - more could be learned by investigating specific products). Potential workflow for experimenting:

  1. Learn about the operating instructions for the specific product
  2. Apply the coatings to 1 nut each (preclean needed for outer surfaces?)
  3. Apply the coatings to different regions of the threaded rod

This experiment would allow us to learn about how the conversion coatings may work and behave.

See attached photos and video for more insights.

Attachment 1: IMG_7794.JPG
Attachment 2: IMG_7795.JPG
Attachment 3: IMG_7796.JPG
Attachment 4: IMG_7799.MOV
Attachment 5: IMG_7801.JPG
Attachment 6: IMG_7802.MOV
Attachment 7: IMG_7804.JPG
  250   Thu Apr 8 17:01:52 2021 StephenHow ToModal TestingTroubleshooting low vibrometer signal / absence of ring down

Regina's problem statement:

 I attached examples of two measurements I got and wanted to know if these look reasonable. I took 6 measurements total, and I attached the first and last measurements. The graph on the last page is a picture of the weighting step for reference.

I didn't see significant ring down in all my measurements. Is this to be expected? I thought since the baffle is now rigidly mounted, the vibration should go almost to zero. I was also getting some low amplitude noise throughout the entire frequency domain that didn't show up in the first couple measurements I took. I tried to reset the vibrometer like you mentioned but they were still present. Is this a problem?

Stephen's reply:

1) Vibrometer may need a higher diffusivity surface to improve signal level.

Replying to your absence of ring down in your measurements - I agree that it looks like the vibrometer output is not behaving well, for one reason or another. In the freely suspended case, I was thinking this was due to large yaw and pitch motion causing high signal variation. Given that the symptom occurs when the baffle is fixed, I think the likeliest reason is the low signal, due to the low scatter and highly specular surface finish of this baffle (aka shiny). One way to troubleshoot would be to attach a compliant, diffusely reflecting material to the surface - think a small square of the adhesive-coated part of a Post-It note, for example - then tune the focus of the vibrometer and see if the vibrometer's signal level bar improves. If the signal level improves, take a hammer-excited measurement, and see if you see any ring down. If this behaves as you might expect, you could generate mode shape data with your excitation roving around the surface of the baffle while your response is fixed - just one baffle point would need your diffuse Post-It square (I might go with a central, or near central, location).

2) Test Article is not well understood, so try measuring something that has been characterized before.

If you try playing with the diffusivity and focus but the signal level doesn't improve, or if you don't see any ring down still, try pointing the vibrometerat the suspension cage and exciting the suspension with the hammer - that should give some real signal regardless of the precise setup, and if that gives similarly mystifying results, let me know and we can think a little harder about what might be going on. I feel pretty confident that between these two tests, you will find an answer.

3) Add another transducer (ie. a witness accelerometer) for comparison.

Another way to support your understanding of your setup (and a good practice) would be to mount the accelerometer to the suspension cage, adjacent to the baffle mounting brackets, or even to the mounting brackets themselves. This accelerometer would supply a witness to the low frequency resonances of the cage, which you may excite during your measurements, and might also provide some insights to the baffle panel resonances (rigid coupling with lower modal mass = smaller vibrations, but likely still above the noise floor of the accel) supporting your eventual successful vibrometer measurements.

4) Notes about mounting an accelerometer.

Mounting would involve collecting a ~[1mm x 1mm x 1mm] chunk of beeswax, spreading the beeswax onto the face of the accelerometer opposite the cable (I like to press it with the outer, flat-ish surface of my thumb nail to spread), and pressing the beeswaxed face onto a flat surface - think a 5 second push with all of your arm strength, which should create a thin layer with plenty of tackiness to hold the accel in any orientation. If it doesn't seem like it could hold for a day, then you might need more beeswax, or more force to create that thin layer. Note: the main way that an accel can go from useful to not is to experience a shock event, so I would recommend that you use some kapton tape to affix the accelerometer cable to the suspension cage - this will strain relieve your cabling and provide a fall restraint, and the potential for the cabling to influence the measurement is minimal here because it is remote from the baffle.

Attachment 1: regina_troubleshooting_GraphsBKHammer.pdf
regina_troubleshooting_GraphsBKHammer.pdf regina_troubleshooting_GraphsBKHammer.pdf regina_troubleshooting_GraphsBKHammer.pdf
  251   Wed May 19 09:24:32 2021 StephenProgressRTS for COCKeyence Microscope integrated into RTS Setup

StephenA, 20 April 2021

Finished integrating the RTS Microscope Mount Assembly for the Keyence VH-Z250T lens (D2000085 WIP).

Feature description:

  • Lens assembly may be fully connected to microscope, then attached to the mount.
  • Easy on/off by passing lens assembly upward on shaft, then tightening thumb screw.
  • Locking shaft collars are added for security, once the lens is in the final position on the shaft and the thumb screw has been tightened
  • Position of lens assembly is repeatable in height and rotation.
    • Lens shaft mount (affixed by single thumb screw) registers in height and rotation against a flats cut into the vertical shaft. This provides registration of rotation about shaft axis.
    • Shaft is affixed to cantilever arm using shaft mounting blocks, including one with a set screw registering the rotation of the shaft with respect to the structure.
  • Lens shaft height and lens height may be adjusted independently to a large range of positions, using a series of thumbscrew flats and a continuous shaft registration flat.
  • Translation stage (used to focus microscope) has a hard stop in the direction toward the optic surface.

Overview of procedure for assembling the mount:

  1. Cantilevered aluminum extrusion arm is preassembled to interface plates on an optical table. Interface plates should be spaced appropriately for the destination breadboard - the spacing on a one inch grid can be confirmed on an arbitrary optical table, but the layout should be confirmed with measurements of the application.
  2. Shaft interface plates are preassembled to arm at a length along the arm that is appropriate for application.
  3. Translation stage may be preassembled to arm, or mounted in situ. Translation stage free plate is slid out of the way to access 1/4-20 clearance holes used to affix translation stage base plate to the aluminum adapter plate.
  4. Arm should be mounted to application at this stage.
  5. Shaft should be mounted to translation stage in situ, via the below process.
    1. A set screw through the base of one of the shaft mount blocks is driven into the shaft's continuous upper flat, registering the shaft's rotation. The shaft should be clamped fully on the base, with the set screw meeting the flat - needs some slight loosening of the upper clamp to attain the correct rotation.
    2. The shaft is lightly clamped into the second base, with roughly the correct alignment and spacing, which are
    3. The mount bases are placed on the translation stage, and adjustments are made with the bases gently loosened to align to the vertically-held shaft and interface to the tranlation stage threaded hole spacing.
      1. If loosening any mount block clamps, the shaft must be held to prevent a sudden drop!
    4. Overall shaft height is set by the position of the mount blocks along the shaft. Once the rotation-registering set screw is in place, shaft height may be adjusted by loosening the mount block clamps, with the mount block bases still on the translation stage.
  6. Confirm height of shaft provides clearance from optic (check for interference every time!)
  7. Add upper shaft clamp to provide a third clamping location and vertical stop.

Overview of procedure for installing the microscope:

  1. Bring the microscope lens assembly upward onto the shaft from underneath.
  2. Tighten the thumb screw into the correct flat, currently the second from the bottom.
    1. Helps to make sure the thumb screw is just outside of the ID of the mount when you start the installation, so that you can tell when the thumb screw has extended into the flat and past the OD of the shaft.
    2. I prefer to turn the thumb screw 2 turns, then gently lower the thumb screw into contact with the bottom surface of the flat. This provides a height registration and constraint for the lens assembly. Once I feel the lens assembly resting on the flat of the shaft, I then tighten the thumb screw into the vertical surface of the flat and lock in the position.
    3. Hold the lens assembly by the main body with one hand during this operaiton, to avoid dropping the lens
  3. Add the bottom shaft collar, typically stored loose above the permanent top shaft collar, to provide a redundant vertical height restraint.
  4. Use the translation stage to make any final height adjustments required to bring the optic into position under the microscope and avoid interference.
  5. Remove lens cap only when ready to bring the optic into position!

Images of mount in various states:

  1. Mount ready to host microscope lens assembly - IMG_8613
  2. Array of flats used to host the lens assembly's thumbscrew (we currently are mounted in the second from bottom flat) - IMG_8614
  3. Tightening of thumb screw, from similar POV to previous images (slightly higher zoom) - IMG_8615
  4. Lens assembly mounted and fully secured to mount - IMG_8617
  5. Overview image of lens assembly in mount; taken before fully secured, as lower shaft clamp is missing - IMG_8616
  6. Microscope hosted on small wire cart, in corner adjacent to RTS table - IMG_8467
Attachment 1: IMG_8613.JPG
Attachment 2: IMG_8614.JPG
Attachment 3: IMG_8615.JPG
Attachment 4: IMG_8617.JPG
Attachment 5: IMG_8616.JPG
Attachment 6: IMG_8467.JPG
  253   Fri Sep 3 14:25:00 2021 StephenProgressRTS for COCAnneal of SN0932 at 300C for 10 hours

SN0932 was annealed between 02 and 03 September 2021 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe).

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 300 °C
Hold time = 10 hours
Ramp down rate = 100 °C per hour

Witness RTD observed a ~22 °C overshoot and ~14 °C offset from controller RTD. See attached image (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.


Attachment 1: anneal_sn0932_300C_20210903.png
Attachment 2: anneal_sn0932_300C_20210903.xlsx
  254   Thu Sep 9 14:56:26 2021 StephenProgressRTS for COCAnneal of SN1535 at 300C for 10 hours

SN1535 was annealed between 07 and 08 September 2021 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe).

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 300 °C
Hold time = 10 hours
Ramp down rate = 100 °C per hour

Witness RTD observed a ~21 °C overshoot and ~14 °C offset from controller RTD. These parameters were consistent with the elog entry ENG_Labs/253. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.

Attachment 1: anneal_sn1535_300C_20210910.png
Attachment 2: anneal_sn1535_300C_20210910.xlsx
  255   Thu Sep 16 21:23:08 2021 StephenProgressRTS for COCSEM Log for LMA Coating Chamber panel coupon

Imaging effort of coupons collected from LMA coating chamber panels.

uncoated_A_01 = area where coating delaminated during coupon cutting, near angled edge.


  256   Fri Sep 24 13:40:22 2021 StephenProgressRTS for COCModified 75mm RTS mount ring to host 80mm witness sample

Simple machining operation setup and executed in Downs 228. Taking notes for future replication, and to drop the Photo Album somewhere useful.

Also thought this log would be helpful to communicate that we are able to quickly knock out simple mounts and mods like this in house.

 - Used Rotary Table for uniform circular cutting path; bolted down with 1/2" T-nuts and translated mill table to center ID of Rotary Table with edge finder. See Attachment 1 (more images in above photo album).

   --> 8" diameter Rotaty Table was a little too big for a standard end mill as the mill spindle is only offset from the turret by about 5 inches. There was not enough travel range in the direction toward the turret to reach the 40 mm radius from the Rotaty Table center. Could have cut in a different direction, but I didn't want to be caught later so I shifted to a larger radius cutter. While I was figuring this out, I managed to shear off one of the handles for locking down the Rotary Table during cutting - oops!

   --> Originally intended cutter was a .5" end mill, but I shifted to a 90 degree face mill for the extended radius given the above issue. I didn't feel too guilty about cutting the corners with the face mill, as the optic will have bevels and the acetal/delrin was soft.

 - I attempted to measure the 75mm diameter bore, and found the radius was larger by ~1mm. I then attempted to make a minimum 81mm diameter bore to host the 80mm optic, and overshot by a bit ( < 1mm ).

 - I elected to go for a greedy cut, creating a counterbore of the 75mm bore at an intermediate bore depth. This was an attempt to retain the 75mm bore function along with the new 80mm bore, and to fix either bore with the existing set screw. Liyuan verified that the new 80mm bore still behaves. So far, so good.

Attachment 1: IMG_9912.JPG
  257   Fri Oct 1 19:14:49 2021 StephenProgressRTS for COCCarbon tape absorber refererences on 1" optic


WIP placeholder

  258   Fri Oct 1 19:58:57 2021 StephenProgressCOC AbsorbersCoupons cut for Bead Blasting (quote pending)


WIP placeholder

Ref. T2100351 instructions, plus email exchange indicating available media sizes.

Ref. FRS Ticket 20562 for shipment details.

  259   Fri Oct 1 20:44:08 2021 StephenProgressTMDSFabrication and drawing of Connector Guard


Ref. D1400331-v8 Item 48 - new high voltage feedthrough D2000585 protrudes along axis and requires protection.

Constructed simple connector guard for a 6" conflat on TMDS, with the following materials:

 - Stainless 304 sheet, 4" x 36" cut to length (a little long since I initially thought the conflat was 6.5" OD, but intended length is 18.7" for the 18.8" diameter) - p/n McMaster 1421T63

 - Stainless worm drive clamp - p/n McMaster 5682K22

Attachment 1: IMG_9949.JPG
  260   Tue Oct 12 12:59:23 2021 StephenHow ToGeneralLista tool chest jammed, opened

[Stephen, Dean]

Aaron's past experience at Cryo_Lab/2563 is familiar to other LIGO users of the Lista tool chests. Occaisionally the mechanism which keeps the remaining drawers closed while a single drawer is open can lock all drawers. Dean brought to my attention that the Downs 228 chest was apparently locked. The key was nowhere to be found. Here's how we solved the problem:

  1. I remembered Aaron's past experience and searched the elogs for "lista" until I found it.
  2. Dean and I tried to perform the maneuver described at Aaron's link, but we were using flimsy stock that didn't seem to allow us to get the needed leverage.
  3. I called the local Lista distributer (DMARK, 562.799.9010) and received an email including break-in instructions (Attachment 1, Attachment 2).
  4. To expand upon the attached instructions, here are a few points of emphasis:
  • Dean and I used a 1/4" x 1" x 36" aluminum strip to push straight forward on the C Channel.
  • A flashlight could be used to ensure alignment to the C Channel if feel wasn't enough.
  • Lifting a drawer was necessary to create a large enough gap (Attachment 3).
  • Once we were successfule we removed a drawer to show how we had pushed (Attachment 4).

The key was found in the upper drawer and placed atop the chest.

Attachment 1: Lockout.pdf
Attachment 2: Break_in_Instructions_Video.mov
Attachment 3: IMG_0170.JPG
Attachment 4: IMG_0169.JPG
  261   Wed Jan 19 18:31:18 2022 StephenProgressRTS for COCAnneal of SN1009 at 300C for 10 hours

SN1009 (80 mm witness sample) was annealed between 19 and 20 January 2022 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe). Start time was 18:28 Pacific, and sample was removed at 17:50 Pacific on the next day.

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 300 °C
Hold time = 10 hours
Ramp down rate = 100 °C per hour

Witness RTD observed a ~20 °C overshoot and ~13 °C offset from controller RTD. These parameters were consistent with the elog entries ENG_Labs/253 and ENG_Labs/254. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.


Attachment 1: anneal_sn1009_300C_20220120.png
Attachment 2: anneal_sn1009_300C_20220120.xlsx
  262   Tue Jan 25 18:25:22 2022 StephenProgressRTS for COCAnneal of SN1009 at 400C for 10 hours

SN1009 (80 mm witness sample) was annealed between 25 and 26 January 2022 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe). Start time was 17:48 Pacific, and sample was removed at ~17:30 Pacific on the next day.

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 400 °C
Hold time = 10 hours
Ramp down rate = 100 °C per hour

Additional annealing run after ENG_Labs/260 at higher temperature to hopefully yield improvements to absorption.

Witness RTD observed a 421.1 °C overshoot and 14.5 °C offset from controller RTD. These parameters were consistent with the elog entries ENG_Labs/253, ENG_Labs/254, and ENG_Labs/260. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.

Attachment 1: anneal_sn1009_400C_20220126.png
Attachment 2: TMC01004_sn1009_400C_20210126.xlsx
  263   Fri Jan 28 18:01:33 2022 StephenProgressRTS for COCAnneal of SN1009 at 500C for 10 hours

SN1009 (80 mm witness sample) was annealed between 28 and 31January 2022 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe). Start time was 17:58 Pacific, and sample was removed at 8:30 am on Monday after a full weekend's cooldown.

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 478 °C (To avoid any unintended over-temperature due to overshoot or steady state offset - the datalogger RTD and the controller RTD have some discrepency at high temperatures)
Hold time = 10 hours
Ramp down rate = 100 °C per hour

Additional annealing run after ENG_Labs/261 and ENG_Labs/262 at higher temperature to hopefully yield improvements to absorption.

Witness RTD observed a 497.2 °C overshoot and 14.6 °C offset from controller RTD. These parameters were consistent with the elog entries ENG_Labs/253, ENG_Labs/254, ENG_Labs/260, ENG_Labs/261, and ENG_Labs/262. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.

Attachment 1: anneal_sn1009_500C_20220131.png
Attachment 2: TMC01004_sn1009_500C_20210128.xlsx
  264   Tue Feb 1 10:05:46 2022 StephenProgressRTS for COC Anneal of SN1009 at 500C for 56 hours

SN1009 (80 mm witness sample) was annealed between 01 and 04 February 2022 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe). Start time was 09:56 Pacific, and sample was removed at 10:00 on Friday morning after a 16 hour cooldown.

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 478 °C (To avoid any unintended over-temperature due to overshoot or steady state offset - the datalogger RTD and the controller RTD have some discrepency at high temperatures)
Hold time = 51.5 hours (was 56, but I had neglected the ramp up time
Ramp down rate = 100 °C per hour

Additional annealing run after ENG_Labs/263 with longer duration to hopefully yield improvements to absorption.

Witness RTD observed a 497.1 °C overshoot and 14.5 °C offset from controller RTD. These parameters were consistent with the elog entries all entries, particularly the shorter duration ENG_Labs/263. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.

Attachment 1: anneal_sn1009_500C_20220204.png
Attachment 2: TMC01004_sn1009_500C_20210201.xlsx
  Draft   Tue Feb 8 18:52:56 2022 StephenProgressRTS for COCAnneal of SN0818 and SN0654 at 500°C for 100 hours

[WIP Placeholder]

SN0818 and SN0654 (25 mm HR witness samples - SN0818 is ETM, SN0654 is ITM) were annealed between 08 and 15 February 2022 - used the large furnace in Downs 221, atmosphere was air, used glass petri dishes to protect optic (from Gabriele and CRiMe). Start time was 18:42 Pacific, and sample was removed at 11:00 on Monday morning after a 16 hour cooldown.

Controller parameters:

Ramp up rate = 100 °C per hour
Hold temp = 478 °C (To avoid any unintended over-temperature due to overshoot or steady state offset - the datalogger RTD and the controller RTD have some discrepency at high temperatures)
Hold time = 100 hours
Ramp down rate = 100 °C per hour

Annealing run on ETM HR coatings for long duration at high temperature, hoping to yield improvements to absorption.

Witness RTD observed a 497.1 °C overshoot and 14.5 °C offset from controller RTD. These parameters were consistent with the elog entries all entries, particularly the shorter duration ENG_Labs/263. See attached image of the temperature profile (.xlsx file is source document).

Optic is now with Liyuan in RTS for recharacterization after anneal.

  266   Thu Apr 14 14:12:23 2022 StephenProgressHWS_PADXY Stage build for TM-HPAD in Downs 318

[Stephen, Jordan, Camille]

We started building the Zaber XY stage, following instructions in vendor manual link with notes at E2200112 google doc.

Some notes and lessons learned:

  • The motor - controller cables need to be straightened by 24 hours of vertical hanging "to relieve packaging stresses".
  • In vendor terminology, the X axis is the longer lower rail, and the Y axis is the shorter upper rail.
  • The vendor recommends testing device functionality before completeing structural assembly.
  • We have all motors attached and are just about to attach the Y axis rails onto the X axis alignment bars.

With the cables needing to hang and the device functionality testing depending on those cables, we have paused until Friday. Complete stage structural assembly anticipated tomorrow!

Attachment 1: IMG_1476.JPG
  267   Fri Apr 15 16:15:56 2022 StephenProgressHWS_PADXY Stage build for TM-HPAD in Downs 318, device testing and joining of axes

[Stephen, Jordan, Camille]

We continued building the Zaber XY stage, following instructions in vendor manual link with notes at E2200112 google doc.

Some notes and lessons learned:

  • The stepper motors and controller are all functional, yay!
    •  A homing test using the vendor's software was conducted, videos will be posted here.
    • First homing test used travel range 1250 mm, following instructions from vendor using stepper motor p/n; however, we found that this caused a crash at the far end of travel; actual max travel from home, considering physical constraints, is approximately 1200 mm, but we ordered a stage with 1000 mm travel. So, there's extra range, but 1100 mm is a good limit.
    • Manual stop button on controller seems to only pause sometimes; useful but better to use software stop.
    • One axis had home sensor installed in reverse orientation, so the homing failed during its homing test, causing a crash at the far end of travel.
  • The cable for the Y axis was supplied incorrectly, and inconsistently with the packing slip (should have been a 16 pin to 25 pin cable, p/n MC10T3L300, but we instead received a 16 pin to 16 pin cable, p/n MC03L300.
    • Until a replacement is supplied, we can wire only 2 axes at any one time.
  • The X and Y axes have been structurally joined, then mounted on 6" pylons.
    • Because of some interference between the bracing and the alignment bars, these were removed and can be reapplied when the vendor gives further instruction.
    • Calipers were used to square the axes and ensure parallelism, and the free X axis was driven through the squared axes to confirm the friction feels similar through the entire travel range.
  • The correct Y axis cable has been received, installed, and routed.
    • This included an international FedEx Priority overnight shipment, a quick double check that the connectors would fit, and a 24 hour vertical hang.
    • The cable guide has been finalized; this long cable runs along the long axis as the stage is driven through its range of motion, and the cable guide articulates to retain a safe bend radius.
  • All three of us have learned to use the control software, Zaber Launcher.
    • Software commands may be implemented through the GUI in some cases, for convenience, but all can be routed through an ASCII protocol Terminal.
    • Documentation relating to software (manuals, tips, discoveries, lessons learned) are compiled at E2200112.
  • The breadboard and A frame are assembled and mounted.
    • We still require an interface plate to come through, hopefully in April.
    • We will next consider shielding to prevent turbulence in the Hartmann WFS path.
  • Laser install and optical alignment may proceed next week (April 25th).

We have a stage which is needing a bit of fine tuning, an interface plate, and some software integration work, but overall the build has proceeded nicely.

Attachment 1: 20220421_142120.jpg
  Draft   Fri Apr 29 15:00:47 2022 StephenProgressHWS_PAD 

Actions taken this week:

  • Placed PO for


Next steps (for next week):

  • Cable routing
  • Move breadboard to back side of A frame
  44   Fri May 4 15:58:20 2018 Rich AbbottGeneralElectric Field MeterNeon Gas Fill of Cube 1

Todd, Luis, Calum, Rich

Filled EFM #1 with neon today.  This is the first time we have done this so a procedure (E1800138) was written.  Basically we wrapped the EFM with a band of foil across all electrometer (X and Y) inputs to ground them, then put the EFM into a bag.  We used a vacuum cleaner to remove the air from the bag, then sealed off the port used for the vacuum cleaner.  A hose to inject neon from the gas bottle was prestaged such that it went into the top flange port of the EFM (the blank off flange).  We filled the bag with neon while recording time and flow rate.  The neon was being delivered at ~4psi which corresponded to ~1 +/-0.1 standard cubic feet per minute as measured by a sightglass flow meter.  It took 1 minute and 50 seconds to fill our bag.  Using flow and time this corresponded to 1.83 cubic feet of neon.  We also measured the dimensions of the bag which had formed a rough cylinder (2.5ft long, 0.5ft radius) which equates to 2 cubic feet which is in good agreement with the flow based number.

After filling the bag with neon, we found that it was better to snug up the bolts using a closed end wrench thus keeping the neon inside the EFM, then to do the final torquing immediately after the EFM is removed from the bag.  The torque spec used was 180 inch-pounds to bolt the CF flange to the cube.  This spec was derived from the MDC vacuum specification for the cube and flange arrangement we used.

Attachment 1: Under_vacuum.jpg
Attachment 2: Sealed_bag.jpg
Attachment 3: 180_inch-pounds_torque.jpg
Attachment 4: Bolted_after_fill_with_Neon.jpg
Attachment 5: TeamWork.jpg
Attachment 6: TeamWork2.jpg
Attachment 7: EFM1.jpg
Attachment 8: NeonBottle.jpg
Attachment 9: NeonInflatedBag.jpg
  45   Mon May 7 10:36:50 2018 Rich AbbottGeneralElectric Field MeterMoving EFM #1

Rich, Bob, Calum, Todd, Luis

EFM#1 has passed the helium leak checking phase and is being moved over to the 40m Lab for the neon accumulation test.  The electrical inputs will be banded with clean aluminum foil to protect against inadvertent static electric charge damage.

  47   Mon May 7 17:53:46 2018 Rich AbbottElectronicsElectric Field MeterCapacitance Measurement

Luis, Rich

In an effort to understand where the ~20pF capacitance comes from as measured at the site of the sense plate to body, we measured the capacitance of the ceramic feedthrough all by itself.  After checking two examples, we concluded that the feedthrough capacitance is about 3pF.  The datasheet for the AD549 opamp says the amplifier input capacitance is around 1pF.  A calculation of the approximate capacitance of the sense plate to the body is around 7pF ignoring fringe fields, and the capacitance of the L-bracket inside the cube to the inner flange is around 0.5pF.  This total (~11.5pF) leaves 8.5pF unaccounted for.

  50   Thu May 10 10:19:01 2018 Rich AbbottElectronicsElectric Field MeterMeasurement of input capacitance of EFM

Luis, Rich

Yesterday, we spent quite sometime messing around trying to measure the input capacitance of the EFM.  Each EFM input feeds into an AD549 opamp.  These opamps have a very high input impedance made using JFETs.  Essentially, one is looking into the gates of a bunch of JFETs in parallel.  The gate of a JFET can be envisioned as a very high impedance resistor (>10^15 ohms) in parallel with a picofarad or so.  We thought we would be clever and measure this capacitor.  It turns out that the opamp had different ideas...

While the input of the opamp is reasonably modeled by a parallel resistor and capacitor, the capacitor value depends on the amount of voltage present on the opamp input.  When we would try to measure the input impedance using a simple capacitance meter, the meter would apply a sinusoidal voltage that is used to calculate the capacitance of the circuit hooked to the meter.  As the voltage of the sinusoid varies, so does the capacitance.  This dynamic situation confused the hell out of the capacitance meter, which staunchly refused to place any limit on the measured capacitance other than approximately a value from minus 1uF to plus 1uF.  The actual expected value should be around 1pF.

Eventually, we gave up trying to measure the input capacitance and instead applied a step change of input voltage to the electrometer input (using a piece of aluminum foil near the copper rod that forms the input to the EFM).  We would watch and plot the voltage decay as a function of time.  Because we don't know the resistance (assumed to be 1 x 10^12 ohms), nor do we know the input capacitance, we can only derive the product, RC, of the two.  Here's what we saw:

This grainy image shows some measured data with a fit overlayed in orange.  If the resistance is indeed 10^12 ohms, then the calculated capacitance would be 6pF.  We were able to measure the capacitance of the ceramic feedthrough to be about 4pF, so this means the total input capacitance of the EFM circuit board and opamp would be around 2pF.  Quite reasonable really.  Next, we are going to bolster our confidence that these resistors are actually producing 10^12 ohms by using a second resistor in series with the EFM input to form a 2:1 divider.  If this doesn't end tragically, we will post the results soon.

Attachment 1: RCtimeEFM.pdf
  55   Tue May 15 19:47:01 2018 Rich AbbottElectronicsElectric Field MeterElectrical Tests on EFM 1, 2, and 3

Luis, Stephen, Calum, Liz, Rich

Today we had a first look at EFM 1, 2, and 3 in terms of the DC transfer function (observing 1VDC injected into each axis input results in 10V differential at the output), and the exponential decay associated with a step voltage change applied to a single calibration plate.  We spent the first part of the day in a typical state of confusion as we struggled to interpret the behavior of EFM 2 and 3.  EFM 1 was just clearing the final clean and bake process in the 40m Lab.  EFM 2 and 3 appear to be functional, however the background electrical noise in the Downs 2nd floor clean room seemed to be getting rectified and contributed a current to the input that lead to saturation.  At some point, we got the word that the mission critical EFM 1 was on it's way over from the 40m Lab, so we abandoned EFM 2 and 3 for now.

On EFM 1, we first verified all axes are functional with a simple DC injection.  1V injected into each output produced the requisite 10V differentially at the EFM outputs.  Then we moved on to the exponential decay test.  We first estimated the capacitance of each of the components on a single axis input to the EFM.  Corroborated by direct measurement where possible, we calculated based on area the following (1 inch PEEK standoffs on the sense plate to the body of the EFM, 1/2 inch PEEK standoffs from the sense plate to the calibration plate:

Sense Plate to EFM Body - 3.6pF

Sense Plate to Grounded Calibration Plate - 5.7pF

Ceramic Vacuum Feedthrough (measured) - 4pF

This yields a total expected capacitance of around 14pF including a bit for the input to the opamp internal to the EFM.

Well, so much for that notion.  Nature had a different picture of the capacitance.  As can be seen in the attached decay plot taken with an oscilloscope in response to a 5V step applied to the calibration plate, the RC time constant is around 23 seconds.  Assuming we got what we paid for in terms of the 10% tolerance, 10^12 ohm resistors, that would imply a capacitance of around 23pF.  Quite a bit more than we expected.  We then embarked on a process to try to figure out where we went wrong.  We had been shielding the sense and calibration plates during the decay measurement by creating a grounded aluminum foil tube that acted as an electric field shield.  We wondered if this was contributing and parasitic capacitance, so we repeated the decay with no shield.  Now we had a 19.8 second RC time constant.  Not much different, but better.  Next, we hung the sense and calibration plates off the side of the work bench in a effort to see if the proximity to the grounded bench was a factor.  Now we had a 18.8 second RC time constant.  Next we removed the voltage source from the calibration plate to effectively unground it so it would be an unreferenced metal object that theoretically should add no capacitance. This also required that we make a big step change in the local EFM electric field environment (Rich wiggling around) such that it would essentially saturate as we no longer had a calibration plate to drive.  This brought the time constant down to 13.6 seconds.  Lastly we did the absurd and completely removed the calibration plate even though Rich was sure it would make absolutely no difference.  Now the time constant decreased to 8.8 seconds to his utter amazement.  Here's a summary:

RC Time Summary
Note RC Time Constant (sec)
Grounded foil Shield around sense and cal plate 20.4
Foil shield removed 19.8
Plates hanging off bench 18.8
Ungrounded Calibration Plate 13.6
Calibration Plate Removed 8.8







Perhaps, and most likely by coincidence, the time constant of 8.8 seconds actually is beginning to agree reasonably with the anticpated capacitance of the sense plate plus feedthough (3.6pF plus 4pF)

Attachment 1: EFM1TimeConstXminusAxis.jpg
  56   Wed May 16 14:39:28 2018 Rich AbbottElectronicsElectric Field MeterSetting Common Mode Rejection Ratio on EFM1

Luis, Rich

Today we explored setting the common mode rejection ratio (CMRR) of the Y-axis on EFM1.  We quickly realized we have a shortcoming in the range of CMRR we can adjust.  Based on the schematic used in EFM1 for the differential amplifier, we are only able to vary the gain (which in turn specifies the window aperture of gain that we can accommodate) over a 0.11dB range.  The intrinsic imbalance of a pair of inputs is usually around 0.3dB or so, so this window is not large enough to reach a minimum in the CMRR.  We are going to ship this unit as it is, but are immediately going to fix the problem and ready EFM2 as a replacement at LHO.

Attachment 1: EFM_Schematic_For_CMRR.pdf
  58   Thu May 17 17:14:18 2018 Rich AbbottElectronicsElectric Field MeterInitial Test of EFM3

Luis, Rich

The attached notes are a first look at EFM3 after Luis soldered the new parts (C5 and C8 were 100pF and now 470pF for both X and Y differential amplifiers.  The resistors (R12 and R15) were 240k and 249k respectively, and are now 43k and 49.9k respectively. The resistor change was done to broaden the range of gain mismatch that we could compensate with the CMRR trim potentiometer. We measured the DC offsets with the inputs shorted and the DC response to a 1VDC input on all axes

Attachment 1: Testing_EFM3.pdf
  59   Fri May 18 16:30:29 2018 Rich AbbottElectronicsElectric Field MeterElectrical tests complete on EFM 3

Nichole, Calum, Rich

The electrical testing for EFM 3 is complete.  EFM 3 has now been torqued down on 5 out of 6 flanges to 180 inch-pounds and was left attached to the helium leak checker.  The leak checker was running well around 8e-10 mBar-l/sec as it was left.  A new procedure (E1800151) has been written to describe the following measurements.  The data below was used to seed the procedure with reasonable numbers.  A SPICE simulation was performed to validate the anticipated magnitude and phase plus noise performance.

Testing EFM3 Continued

Calculated RC pole frequency based on R=49.9k, C=470pF to be 6.79kHz. Using this as a basis for TF acceptance testing. X and Y pots set to 0561 HEX at start of measurement to get +/- gains to be nominally the same. SR-785 on 400 points, 100Hz to 10kHz, 1V source.

In on X+ -> Out Differential -> 100Hz, 6.024dB, -0.9 deg

In on X+ -> Out Differential -> 6.754kHz, 2.979dB, -45.3 deg

In on X- -> Out Differential -> 100Hz, 6.020dB, 179.1 deg

In on X- -> Out Differential -> 6.754kHz, 2.921dB, 134.3 deg

In on Y+ -> Out Differential -> 100Hz, 6.021dB, -0.8 deg

In on Y+ -> Out Differential -> 6.754kHz, 3.278dB, -43.4 deg

In on Y- -> Out Differential -> 100Hz, 6.021dB, 179.2 deg

In on Y- -> Out Differential -> 6.754kHz, 3.229dB, 136.5 deg

Next, the noise measured differentially at the output of each axis is measured with both positive and negative inputs shorted

X-axis noise at 100Hz -> 215 nVrms/rtHz

Y-axis noise at 100Hz -> 215 nVrms/rtHz

Measured the time constant of each input:

X+ -> 5.8 sec

X- -> 6.2 sec

Y+ -> 6.0 sec

Y- -> 5.8 sec

​CMRR (added by Luis on 052418)

X = -65dB @ 10Hz

Y = -75dB @ 10Hz

  60   Mon May 21 15:49:04 2018 Rich AbbottGeneralElectric Field MeterEFM 2 and EFM 3 Update

Luis, Calum, Rich

Changed out the resistors in EFM 2 from 249k to 49.9k (R15), 240k to 43k (R12), 100pF to 470pF (C5 and C8) to allow wider CMRR range and reduced gain.

Bagged EFM 3 for helium leak test

20 sec helium. Pump rate started at 2e-10 mbar liter/sec helium and rose to 2e-9 over a few minutes.  Pressure then started slowly dropping to 1.9e-9.  We consulted with Dennis on this and he feels the result is marginal.  We elected to remove the unit from the bag and start again.  We checked the torque on each bolt using the same torque wrench as we used on EFM 1 in case there was a calibration error on the torque wrench.  Some bolts did move by 5 to 10 degrees or so.  The feeling we got was that the observed pressure rise may have been due to one of the couplings used to attach the leak checker to the EFM, so we bagged all the couplings as a precaution.  We will wait until the pressure is back down in the minus 10 range and try again.

We tried again, but are still having problems.  The leak rate is now ~7e-9 so we abandoned the helium leak check of EFM 3 and are moving to do the electrical tests of EFM 2.

Below can be seen the video from EFM3 test process.



Attachment 1: EFM_3_Leak_Test___Fail.mp4
Attachment 2: EFM_3_Leak_Test__Take_2.mp4
Attachment 3: EFM_3_Leak_Test_Take_3.mp4
  64   Tue May 22 19:06:30 2018 Rich AbbottGeneralElectric Field MeterStatus Update

Luis, Calum, Rich

After a successful helium leak check which took unbelievable care to pull off (mainly by Calum's persistence and good judgement), EFM 2 was charged with neon gas today.  A flow for 125 seconds at 1 SCFM was performed and other steps per the procedure.  The resulting bag measured approximately 60cm long with a radius of around 20cm. 

The volume of neon introduced into the bag was 6e4 cm^3 based on flow and time, and 7.5e4 cm^3 based on final bag volume, which is within reason for a crude measurement.  The EFM was placed in its dedicated Pelican case and is ready for transport to the 40m lab for neon accumulation test preparation in the morning.  The test data for EFM 2 is being loaded into the revised E1800151 procedure for upload to DCC

Attachment 1: EFM_2_NEON_FILL.mov
Attachment 2: EFM_2_NEON_FILL.mp4
  252   Tue Jul 27 14:32:30 2021 Rich AbbottElectronicsHelicoflex Enclosure105kHz FC Detector

Luis, Chub, Calum, Jordan, Dean, Rich

Today we filled neon into the new enclosure (Dxxx) that's destined for use with the A+ filter cavity length and alignment detector, plus the new DCPD preamplifiers.  The goal is to do a neon accumulation test over in the 40m lab.

Here is some related information:

  1. The enclosure, lid, Helicoflex gasket, A286 10-32 SHCS bolts (used 20), S5 titanium washers (used 38*), S5 titanium nuts (used 20) were all cleaned and baked in the 40m bake facility by Jordan as an initial condition. * there were two holes where the washer would not fit under the head of the SHCS
  2. We had on hand:
    1. Fresh bottle of neon plus hoses and regulators (loosen the regulator knob for minimum pressure, tighten the knob for more pressure to load)
    2. Torque wrench
    3. Allan adapters for torque wrench to go into SHCS
    4. 3/8 inch spanner to hold nuts
    5. Fresh glove bag
    6. Vacuum pump plus hoses
    7. Kapton tape to seal hose ports
    8. Measuring tape to judge how much volume of neon we used
    9. iPad to take pictures as we went
    10. Big adjustable wrench and allen key to change out regulator on neon bottle
    11. Circuit board to install inside
    12. Ribbon cable to attach the circuit board to the inner wall of the enclosure (need strain relief design to be sure these connectors don't fall off)
  3. Here's what happened:
    1. Luis and Rich staged all the stuff in the clean room in the jitter lab
    2. We put the internal circuit board into the enclosure
    3. We plugged in the ribbon cable but had a bit of difficulty with putting the strain relief screws into the connectors (need a different setup here).  We ended up using some 4-40 screws in the connector on the wall of the enclosure, plus some zip ties to anchor down the connector to the PCB
    4. We didn't have any shorting plugs for the external connectors to avoid ESD damage, so we were careful, but no guarantees.
    5. We placed the gasket in its groove, then placed the lid on top of the enclosure.  Before tightening the bolts at all, we put a rolled up lint free cloth between the lid and the enclosure body so the neon had access to the inside of the enclosure while filling
    6. We put the allen adapters and 3/8 inch wrench into the glove bag
    7. We put the enclosure plus lid and gasket into a glove bag and rolled up as much of the bag as we could while still allowing room to get our hands into the access ports
    8. We added the vacuum hose and neon hose into the ports on the glove bag and taped them closed.
    9. We evacuated the bag with the vacuum pump, and then filled the bag with neon to a bag volume of approximately a 24-inch sphere.
    10. We removed the lint free cloth, then blew more neon into the enclosure to be sure it was filled well.  At this point, we were not thinking that neon was lighter than air.  Our first potential mistake.
    11. We snugged down the bolts and then removed the enclosure from the bag.  
    12. We then went off to lunch (our second mistake) and came back later to do the final torquing.
    13. When we returned, we realized that we now didn't know how much neon may have diffused from the interior of the enclosure, thus the experiment was uncertain.
    14. We proceeded anyway, and found torqued the bolts initially in a star pattern to 30 inch-pounds.
    15. After seven loops, (the second of which we abandoned the star pattern as it was too hard to keep our heads straight) we were at metal to metal on the flange surfaces, and could no longer rotate the bolts at 30 inch pounds.

We are chalking our inconclusive results up to experience, and starting again tomorrow with a fresh gasket.  We will be sure to account for the boyancy of neon in our fill method, and to rig a better way of flushing the interior of the enclosure with neon.


  96   Thu Nov 8 16:14:06 2018 Regina LeeOpticsGeneralBlack Glass Cleaning

Cleaning of the Black Glass Beam Dumps

This was done as part of the analysis of fog/particulates on the black glass beam dump samples from LHO. New samples of black glass from the manufacturer were examined and cleaned. 

Inventory: Brush, TX715 Alpha sampling swab, green flash light, IPA, small beaker, IPA wipes, black glass (S1812059), container

-An air nozzle (top gun) was used to blow off any hanging dust particulates

-A plastic brush dipped in IPA was used to brush off the smudges and other particulates. There were streaks left behind from the bristles after brushing the black glass. Most of the particulates were gone.

-A sampling swab was dipped in IPA and was brushed in one direction at a time to get rid of the smudges. This was done until all the streaks were gone, it took about 10 minutes. 

Photos of the black glass after each above step are attached. 



Attachment 1: Tools.JPG
Attachment 2: Black_Glass_Before.JPG
Attachment 3: After_Top_Gun.JPG
Attachment 4: After_Brush.JPG
Attachment 5: Final_(After_Swab).JPG
  2   Tue Apr 22 10:37:21 2014 Norna RobertsonMechanicsImproved HSTSdraft technical doc put together

I have written a doc summarising current status of work on HSTS redesign of middle mass, including MATLAB transfer functions for a preliminary conceptual design.

See T1400290 at https://dcc.ligo.org/LIGO-T1400290


I'm currently working with Calum on change request for funding a prototype of the middle mass. Eddie is helping us to cost this based on Harrison's conceptual design.

Harrison is working on more details of the design.

  4   Sun Jun 8 10:16:27 2014 Norna Roberson, Harrison MillerProgressImproved HSTSSW rendering of revised HSTS

Harrison has put together a first look at what a revised HSTS with blades at middle mass might look like. This is a work in progress, some parts missing (magnet /flag assemblies etc.)

Attachment 1: HSTS_assembly_clean.JPG
  139   Mon May 20 18:24:11 2019 Marie K. ProgressBS BRDsTest of the new springs

We received the 12 new springs made with a sandwich layer of Pyralux damping today (see dcc D1700188-v3). 

According to T1700176, the bounce and roll modes of the dummy BS in the modal lab are respectively 16.70 Hz and 24.34 Hz. Aiming for a Q~100 for the damped BS, the relative mass of the damper and the modes has to be > 2.0e-4. It means the masses have to be >= 5.556 g for the bounce mode and >= 2.580 g for the roll mode, taking into account the weight of the spring (0.168 g) and the screws (~0.49g each). I got: mb = 0.91 + 4.23 + screw = 5.622 g for bounce and mr = 2*1.06 + screw = 2.620 g for roll. 

Calum helped me taking the first measurement of the new BRD with the B&K software and the vibrometer. We found that the roll resonance is at 27.750 Hz (i.e. 14% too high), with a measured BRD Q of 59 (TBC).

Attachment 1: IMG_20190520_164859560.jpg
Attachment 2: IMG_20190520_184709517.jpg
  143   Fri May 24 17:40:36 2019 Marie K. ProgressBS BRDsSecond BRD assembled

Today I built a second BRD mimicking the first one:

  • Bounce_brd2 = 2.269+2*1.025+screw = 4.936g
  • Roll_brd2 = 241+screw+spacer = 3.062g

I spent some time moving the masses along the blade axis to adjust the frequencies. As measured with the vibrometer, its characteristics are:

  • bounce mode: Q = 80 +/- 6  with f = 16.75 Hz (mean of 8 over 30 measurements).
  • roll mode: Q = 94 +/-7 with f = 24.25 Hz (mean of 8 over 30 measurements).

Then I installed the two BRDs on the suspension to get a rough estimation of the new BS Q. I had to double the drive (2.2V) to significantly excite the suspension. The data is noisy, the maximum of the frequency response is shifted compared to the excitation. The modes are hard to excite and damped very fast (figure 1 to 4) Ther might be an issue with the setup, I will have to chack it again without the BRDS.

I tried to scan the BS resonances with swept sin from the spectrum analyzer to finely measure the resonances of BS. However, the scans are not clean. The best scan I obtained is attached here (see figure 5). The resonances seem to be at 16.8 Hz and 24.4 Hz.

Attachment 1: BS_bounce_spectra.png
Attachment 2: BS_bounce_ringdown.png
Attachment 3: BS_roll_spectra.png
Attachment 4: BS_roll_ringdown.png
Attachment 5: best_TF_large_range.jpg
  154   Fri Jun 28 16:05:40 2019 Marie K. ProgressBS BRDsBRD2 tuning

I tuned BRD2 (with version 4 of the blades) to the measured frequencies of the BS, aiming for a tuning better than 0.5 % as displayed in the range below. 

After some trials, I got the bounce mode tuned to 0.2% and the roll mode tuned better than 0.1 %.


Bounce - target = 16.69 Hz

(range = 16.61-16.77 Hz)

Resonance [Hz]

Roll - target = 24.34 Hz

(range = 24.22 - 24.46 Hz)

Resonance [Hz]
Test 1 2.385+1.029+1.026+screw = 5.050 g 15.450 2.546+screw+spacer = 3.198g 25.175
Test 2 Masses moved along the axis to raise the freq. Max position. 16.400 Masses moved along the axis to lower the freq. Max position. 23.075
Test 3

less mass is needed & moved to max position

2.383+1.025+0.987+screw = 5.006 g

16.800 Masses moved back and forth few times 24.325
Test 4 Masses moved back and forth a few times - f still too low      
Test 5 2.383+2*0.98+screw = 4.967g - still too low 16.475    
Test 6 2.383+0.98+0.95+screw = 4.927 g 16.575    
Test 7 2.383+0.95*2+screw = 4.889 g + back and forth tuning 16.700 - 16.725    

However, repeating the measurements several times after the tuning, I got the following results (mean over 6 measurements):

  • bounce mode: f = 16.750 Hz, Q = 131, tuning = 0.4% (see figure 1)
  • roll mode: f = 24.496 Hz, Q = 133, tuning = 0.6% (see figure 2)

It turns out the tuning is not that great. Furthermore, the Q are higher than expected from previous tests. When measuring the decay, the values were closer to 90. I should rerun the Q analysis via decay fit over the same set of measurements.

Attachment 1: brd2v4_bounce_tuned_july12019.png
Attachment 2: brd2v4_roll_tuned_july12019.png
  155   Tue Jul 2 09:00:46 2019 Marie K. ProgressBS BRDsBRD2 tuning

Retuning BRD2 after yesterday trials. After moving the masses again along the blade axis, I get (mean over 6 measurements):

  • bounce mode: f = 16.76, Q = 130, tuning = 0.4%
  • roll mode: f = 24.38, Q = 126, tuning = 0.2%
  170   Wed Jul 24 10:13:38 2019 Marie K. SummaryBS BRDsSummary of tests with BRDs v4

I haven't posted the BS transfer functions results since we started to test the BS with 2 BRDs attached. I can now read the data that has been saved in .78D from the spectrum analyzer, which makes data analysis much easier! (see elog 171).

  • The first set of tests (tests srs0014.txt to srs0018.txt) were done with BRD1_v4 and BRD2_v4 on the beam splitter.
  • Then, I noticed the blade of BRD2_v4 had been torqued to much. BRD2_v4 was replaced by BRD3_v4. The tests are srs0019.txt to srs0021.txt.
  • Finally I removed both BRDs from the BS to remeasure their tuning. I took this opportunity to remeasure BS modes undamped because I didn't have global scans saved in the .78D format. I'm still missing precise scans for the bounce mode (also because not saved in .78D format originally).

The results are summarized in the tables below and in the figures attached.


B1 Freq. [Hz]

Q1 (from 3dB width) B2 Freq. [Hz] Q2 (from 3dB width) BRD tuning Measured range  Nb points Drive [V] Filename Comments
Measurement B6 16.733 325 - -   16 - 17 600 1 srs0015.txt BRD1_v4 + BRD2_v4 on
Measurement B7 16.742 46 - - BRD3 tuned 16.3 - 17.2 600 1 srs0020.txt BRD1_v4 + BRD3_v4 on
Measurement B8 16.749 289 - - drift from B7? 16 - 17 600 1 srs0021.txt BRD1_v4 + BRD3_v4 on

Is the low Q of measurement B7 due to a very good tuning? See elog 164, BRD3 was tuned to 0.01%. The measurement B7 was taken soon after tuning, and the BRDs might have drifted for the folllowing measurement B8. However, we don't see this good performance in the overall scan that was taken just after installing BRD3 on BS (see figure 3).

To do: retake transfer functions of the bounce mode region with and without the dampers to confirm the Qs. Understand the difference in the measurements (drifts?). A tentative summary is presented in figure 1, but the undamped mode is missing from the figure.


The results are so far are cleaner for the roll mode (see figure 2).


R1 Freq. [Hz]

Q1 (from 3dB width) R2 Freq. [Hz] Q2 (from 3dB width) BRD tuning Measured range  Nb points Drive [V] Filename Comments
Measurement R11 24.116 182 24.419 161   24 - 24.6 600 0.1 srs0016.txt BRD1_v4 + BRD2_v4 on
Measurement R12 24.110 174 24.414 167   24 - 25 600 0.1 srs0018.txt BRD1_v4 + BRD2_v4 on

We can see that adding a second BRD helped to reduce the Q of the second resonance from ~250 to ~170. From elog , we know that the undamped Q of BS is around 3000, and that adding the first BRD split the resonance in two, with Q1 below 200 and Q2 around 250. A third resonance/feature can be seen on the glocal scans, but it is outside the frequncy range of our current measurements.

To do: Take measurements over a larger range (on the high frequency side) to check the third resonance. Add a comparison with the model to check if the measured behavior is expected.


Attachment 1: BS_bounce_BRD_July2019.png
Attachment 2: BS_roll_BRD_July2019.png
Attachment 3: BS_summary_July2019.png
  196   Mon Aug 19 15:57:52 2019 Marie K. ProgressBS BRDsResolving the resonance peaks?

We are currently tracking the evolution of the resonances over time. As Norna pointed out, I am taking measurements of the resonances with a coarser resolution than she did. It means that the peaks may not be quite resolved, and that we are underestimating the Qs of the modes.

On Friday, I measured the lower peak of the bounce mode with a higher resolution. I did this measurement just after the usual measurement of the two bounce peaks (see figure 1). The results from the two measurements are similar in frequency and Q. We will repeat with other resonances before drawing definitive conclusions.

Attachment 1: Meas_54_55.png
Attachment 2: Meas_54_55_zoom.png
ELOG V3.1.3-