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ID Date Author Type Category Subject
15685   Mon Nov 23 14:52:10 2020 KojiUpdateBHDBHD MMT Optics delivered

Basically, they repeated our specs and showed the coating performances for HR/AR for 10deg P and PR/AR for 45deg P. There is no RoC measurement by the vendor.
Nevertheless, their RoC (paper) specs should be compared with our request.

15727   Thu Dec 10 14:48:00 2020 YehonathanUpdateBHDMonte Carlo Simulations

I have rebuilt the MCMC simulation in an OOP fashion and incorporated Lance/Pytickle functionality into it. The usage of the MCMC now is much less messy, hopefully.

I made an example that calculates the closed-loop noise-coupling from SRCL sensing and displacement to DARM in A+. I used the control filters that Kevin defined in his controls example.

The resulting noise budget is in attachment 1. The code is in the 40m/bhd git.

I also investigated why aLIGO simulations behave so different than the A+ simulation (See few previous elogs in this thread). That is why aLIGO results are much less variable, and the simulations in aLIGO barely pass the validity checks, while A+ simulations almost always pass.

The way I check for the validity of a kat model is by scanning all the DOFs and checking that the corresponding sensing RFPDs demodulated signals cross zero. Attachment 2 shows these scanning for 3 such RFPDS for 3 cases:

A+ model with maxtem = 2

ALigo model with maxtem = 2

ALigo model with maxtem = 'off'

It seems like the scanning curves for A+ and ALigo with no HOMs are well behaved and look like normal PDH signals, while the ALigo with maxtem = 2 curves look funky. I believe that the aLIGO+HOMS curves indicate that the IFO is not really in a good locking point. All the IFO lockings were done by using the locking methods straight out of the PyKat package.

Attachment 1: MCMCLance_NoiseBudget_Example.pdf
Attachment 2: IFO_Check.pdf
15732   Fri Dec 11 09:28:52 2020 ranaUpdateBHDMonte Carlo loop coupling Simulations

Cool. Can you give us Bode plots of the open loop gain for each of the 5 length control loops?

 Quote: I have rebuilt the MCMC simulation in an OOP fashion and incorporated Lance/Pytickle functionality into it. The usage of the MCMC now is much less messy, hopefully.

15734   Mon Dec 14 11:09:28 2020 YehonathanUpdateBHDMonte Carlo loop coupling Simulations

I spent a few hours monkeying around with the control filters. They are totally made up and also it's my first time trying to design control filters.

The OLTFs of the different length controls are shown in attachment 1.

The open-loop couplings of the DOFS to DARM are shown in attachment 2.

Note that in Lance/Pytickle the convention is that CLTFs are 1/(1 - G). Where G is the OLTF.

 Quote: Cool. Can you give us Bode plots of the open loop gain for each of the 5 length control loops?

Attachment 1: MCMC_LANCE_OLTFs.pdf
Attachment 2: MCMC_LANCE_OLCoupling2DARM.pdf
15758   Mon Jan 11 16:11:51 2021 YehonathanUpdateBHDMonte Carlo loop coupling Simulations

I dived into the alog to make the OLTFs in the MC_controls example more realistic. I was mainly inspired by these entries:

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=18742

https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=20466

and Evan's and Dennis's Theses.

Attachment 1 shows the new OLTFs. I tried to make them go like 1/f around the UGF and fall as quickly as possible at higher frequencies. I didn't do more advanced stability checks.

I also noticed that imbalances and detunings in the MC simulation can change the plants significantly. Especially DARM, CARM, and sometimes PRCL. I added the option to fix some OLTFs throughout the simulation. At every iteration, the simulation computes the required control filter to fix the selected OLTFs such that it will match the OLTFs in the undetuned and balanced IFO.

Attachment 1: MC_LANCE_OLTFs.pdf
15759   Mon Jan 11 19:10:10 2021 ranaUpdateBHDMonte Carlo loop coupling Simulations
• looking better, but the CARM plot still looks weird.
• you should plot from 0.01 - 10,000 Hz
• All of the loops should have true integrators below 1 Hz.
• I don't think these loops are stable; the Bode plot is not a good way to check stability for LTI systems since you can be fooled by phase wrapping.
15774   Wed Jan 20 18:07:09 2021 AnchalSummaryBHDHAM-A Coil Driver measurements before modifications

I have taken transfer functions and noise measurements of the two HAM-A coil driver boxes D1100687 #S2100027 and #S2100028. All transfer functions look as expected. I'm not sure about the noise measurements. If anyone sees flaw in my measurement method, please let me know. I'm not sure why in some channels I got 10Hz harmoni peaks in the noise. That was very strange. Also let me know if my current noise estimate is wrong.

# Transfer Function Measurement details

• SR785 source out was connected to the differential amplifier input of D1900068.
• The one pair of two BNC outputs of this differential amplifier goes directly to the SR785 Input 1 A and B.
• The DB9 output of the differential amplifier goes to the Coil Input DB9 connector J3.
• Header W2 was shorted to provide ground to the incoming signal.
• Header P4 was shorted to enable all the channels manually.
• Normal operation is the Acquisition mode (Acq) while when pins of header P3 are shorted, we go into the Run mode for respective channel.
• The “To Satellite Box” DB25 port at the read side was conencted to a DB25 breakout circuit and pins 1-9, 3-11, 5-13 and 7-15 were connected to 36 Ohm resistor to simulate Coil load.
• The “Output Monitor” on the rear side is then connected to the test switch DB9 port on D1900068.
• The the pair of BNCs from the test switch is connected to SR785 Input 2 A and B.
• Measurements are taken with file D1100687_TF.yml and D1100687_TF_LF.yml.
• A measurement of just cables without the DUT is taken as well.
• Commands.txt list all the commands used.
• All data is compiled and plotted in Plotting.ipynb
• D1100117_S2100027_TF.pdf and D1100117_S2100028_TF.pdf shows all the transfer functions measured.

# Spectrum Measurements

• All channels were kept in disabled mode (Not shorting P4) to ensure their inputs are grounded on the board.
• I ran two BNC cables with their centers connected to output monitors V2+ and V2- and one of their shields connected to board GND.
• in SR785, A-B differential mode always runs with grounded shields mode, so effectively the board GND got grounded to SR785 GND through internal 50 Ohm resistor. But all ground loops have been evaded.
• The two BNC cables were twisted together to minimize the area between the two center cores of the cables as that is the remaining pickoff possible in this measurement.
• Instrument noise with cables was measured first but shorting the clips of the center cores and one of the shields of the two BNC cables together.
• Measurements were taken with file D1100687_SP.yml and D1100687_SP_LF.yml.
• D1100117_S2100027_Voltage_Noise_Spectrum.pdf and D1100117_S2100028_Voltage_Noise_Spectrum.pdf shows the measured voltage noise spectrum at the output monitors when loaded with 36 Ohms.
• D1100117_S2100027_Current_Noise_Spectrum.pdf and D1100117_S2100028_Current_Noise_Spectrum.pdf shows the esitmate current noise through the coil calculated by dividing the measured voltage noise by 2436 Ohms.
Attachment 1: MeasurementData.zip
Attachment 2: D1100117_S2100027_TF.pdf
Attachment 3: D1100117_S2100028_TF.pdf
Attachment 4: D1100117_S2100027_Voltage_Noise_Spectrum.pdf
Attachment 5: D1100117_S2100028_Voltage_Noise_Spectrum.pdf
Attachment 6: D1100117_S2100027_Current_Noise_Spectrum.pdf
Attachment 7: D1100117_S2100028_Current_Noise_Spectrum.pdf
15776   Mon Jan 25 18:18:04 2021 AnchalSummaryBHDSatellite Amplifier Transfer Functions and noise

I took transfer function and noise measurement of satellite amplifier box's photodiode transimpedance circuit. For the measurement, I created a makeshift connector to convert backside DB25 into DB9 with the 4 channels for PDA input. The output was taken in differential form at the front PD Output port. To feed current to the circuit, I put in 12 kOhm resistors in series at the inputs, so the V/V transfer function measured was multiplied by 12 kOhm to get the transimpedance of the circuit.

# Transfer Function Measurement details

• SR785 source out was fed into PDA input pins using a makeshift BNC-DB9-DB25 converter.
• The output from PDOut DB9 port was fed to test switch in D1900068 to separate differential signal.
• This differential signal was fed back to SR785 at input 2 in A-B configuration.
• Measurements are taken with file D1002818_TF.yml and D1002818_TF_LF.yml.
• A measurement of just cables without the DUT is taken as well.
• Commands.txt list all the commands used.
• All data is compiled and plotted in Plotting.ipynb
• D1100117_S2100029_TFandNoiseSpectrum.pdf shows all the transfer functions measured.

# Spectrum Measurements

• Two pair of BNC cables were twisted together and clips were added at ends.
• One of the GND was connected to board GND. Rest were left unconnected to avoid ground loops.
• Each pair of signal was connected to PDOutP/N.
• The PDA inputs were shorted together to make zero input current to the board.
• Instrument noise with cables was measured by shorting the clips of the center cores and one of the shields of the two BNC cables together.
• Measurements were taken with file D1002818_SP.yml and D1002818_SP_LF.yml.
• Input referred current noise spectrum was calculated by dividing the output voltage noise spectrum by the measured transfer function.
• D1100117_S2100029_TFandNoiseSpectrum.pdf shows all the output votlage noise spectrum and input referred current noise spectrum measured.

Edit Wed Feb 10 15:14:13 2021 :

THE NOISE MEASUREMENT WAS WRONG HERE. SEE 40m/15799.

Attachment 1: D1002818_S2100029_TFandNoiseSpectrum.pdf
Attachment 2: D1002818_Testing.zip
15780   Thu Jan 28 12:53:14 2021 AnchalSummaryBHDHAM-A Coil Driver measurements before modifications

I took some steps to reduce the coupling of 60 Hz harmonics in noise measurement. The box was transferred to the floor instead of on top of another instrument. Measurement was immediately converted into single-ended using SR560 in battery mode with a gain of 10. All of the setups was covered in aluminum foil to increase isolation.

# Spectrum measurement details

Attachment 1: D1100117_S2100027_Current_Noise_Spectrum.pdf
Attachment 2: D1100117_S2100027_Voltage_Noise_Spectrum.pdf
Attachment 3: D1100117_S2100028_Current_Noise_Spectrum.pdf
Attachment 4: D1100117_S2100028_Voltage_Noise_Spectrum.pdf
Attachment 5: SpectrumMeasurement.zip
15781   Thu Jan 28 18:04:55 2021 AnchalSummaryBHDHAM-A Coil Driver measurements After modifications

I did the recommended modifications on of the boards with serial number S2100028. These included:

• R13, R27: 160 -> 75
• C11, C21: 470 nF -> 68nF
• C19: 4.7 uF -> 470 nF
• R15: 3.23 kOhm -> 1.82 kOhm

I took transfer function measurements with same method as in 40m/15774 and I'm presenting it here to ensure the modifications are correct and if I should proceed to the next board as well. I didn't have the data used to make plots in here but I think the poles and zeros have landed in the right spot. I'll wait for comments until tomorrow to proceed with changes in the other board as well. I'll do noise measurements tomorrow.

Attachment 1: D1100117_S2100027_TF.pdf
Attachment 2: AfterChanges.zip
15782   Thu Jan 28 21:44:45 2021 gautamSummaryBHDHAM-A Coil Driver measurements After modifications

Looks fine to me visually but the verdict can only be made once the z:p locations are quantitatively confirmed, and the noise tests pass. It would be interesting to see what kind of time-domain transient (in N of force) switching on the de-whitening introduces, i guess best done interferometrically.

 Quote: I'll wait for comments until tomorrow to proceed with changes in the other board as well. I'll do noise measurements tomorrow.
15784   Fri Jan 29 15:39:30 2021 AnchalSummaryBHDHAM-A Coil Driver measurements After modifications TF and Noise S2100027

I fitted zeros and poles in the measured transfer function of D1100687 S2100027 and got zeros at 130 Hz and 234 Hz and poles at 10Hz and 2845 Hz. These values are different from the aimed values in this doc, particularly the 234Hz zero which was aimed at 530 Hz in the doc.

I also took the noise measurement using the same method as described in 40m/15780. The noise in Acquisition mode seems to have gone up in 10 Hz - 500 Hz region compared to the measurement in 40m/15780 before the modifications.

All channels are consistent with each other.

Edit Mon Feb 1 12:24:14 2021:
Added zero model prediction after the changes. The measurements match with the predictions.

Edit Wed Feb 3 16:46:59 2021:

Added zero modeled noise in the noise spectrum curves. The acquisition mode curves are in agreement with the model. The noise in Run mode is weirdly lower than predicted by zero.

Attachment 1: D1100687_S2100027_After_Modifications_Jan28.jpg
Attachment 2: D1100117_S2100027_TF.pdf
Attachment 3: D1100117_S2100027_Voltage_Noise_Spectrum.pdf
Attachment 4: D1100117_S2100027_Current_Noise_Spectrum.pdf
Attachment 5: AfterChanges.zip
15787   Tue Feb 2 11:57:46 2021 AnchalSummaryBHDHAM-A Coil Driver measurements After modifications TF and Noise S2100028

I have made the modifications on the other board D1100687 S2100028 as well. The measurements were taken as mentioned in 40m/15784. All conclusions remain the same as 40m/15784. The attached zip file contains all measurement data, before and after the modifications.

Edit Wed Feb 3 16:44:51 2021 :

Added zero modeled noise in the noise spectrum curves. The acquisition mode curves are in agreement with the model. The noise in Run mode is weirdly lower than predicted by zero.

Attachment 1: D1100687_S2100028_After_Modifications_Feb01_2021.jpg
Attachment 2: D1100117_S2100028_TF.pdf
Attachment 3: D1100117_S2100028_Voltage_Noise_Spectrum.pdf
Attachment 4: D1100117_S2100028_Current_Noise_Spectrum.pdf
Attachment 5: AfterChanges.zip
15788   Tue Feb 2 17:09:17 2021 yehonathanUpdateBHDSOS assembly

I set up a working area on the table next to the south flow bench (see attachment). I also brought in a rolling table for some extra space.

I covered all the working surfaces with a foil from the big roll between 1x3 and 1x4.

I took the SOSs, SOS parts and the OSEMS from the MC2 table to the working area.

I cleaned some LN Allen keys with isopropanol and put them on the working table, please don't take them.

Attachment 1: 20210202_165501.jpg
Attachment 2: 20210202_162452.jpg
15790   Tue Feb 2 18:24:54 2021 KojiUpdateBHDSOS assembly

You can remove the components of the optical table enclosure (black ones) and use the optical table as your working area too.

15793   Wed Feb 3 16:27:19 2021 AnchalSummaryBHDSatellite Amplifier Transfer Functions and noise After modifications

I have made modifications recommended in this doc. The changes made are:

• R24: 19.6k to 4.99k Ohms
• R20: 19.6k to 4.99k Ohms
• R23: 787 to 499 Ohms
• Removed C16.

I took transfer function measurements, fitted them with zeros and poles and plotted it against the zero model of the circuit. The zeros and poles we intended to shift are matching well with 3Hz zero and 30 Hz pole. The later pole at 1500 Hz is at a higher value from what is predicted by zero.

I also took noise measurements and they are in good agreement with the noise predicted by zero.

Edit Wed Feb 10 15:14:13 2021 :

THE NOISE MEASUREMENT WAS WRONG HERE. SEE 40m/15799.

Attachment 1: D1002818_S2100029_TFAfterChanges.pdf
Attachment 2: D1002818_S2100029_OutputNoiseSpecAfterChanges.pdf
Attachment 3: D1002818_S2100029_InputRefferedNoiseSpecAfterChanges.pdf
Attachment 4: D1002812_S2100029_After_Modifications_Feb3.jpg
Attachment 5: AfterChanges.zip
15796   Thu Feb 4 15:14:55 2021 YehonathanUpdateBHDSOS assembly

I gathered all the components I could find from the SOS towers and the cleanroom and put it all on the table next to the flow bench (See attachment).

I combed through the cleanroom cabinet for SOS parts but didn't find all the parts listed in the procurement spreadsheet. I did find some extra items that were not listed.

This table compares the quantities in the spreadsheet to the quantities collected on the table. Green rows are items I found more than in the procurement spreedsheet while red rows are items I found less.

 ITEM DCC # Qty required Qty in procurement spreadsheet How much I found SENSOR/ACTUATOR PLATE D960002 14 21 21 SUSPENSION BLOCK D960003 7 9 9 TOWER BASE D960004 7 10 11 RIGHT SIDE PLATE D960005 7 12 13 LEFT SIDE PLATE D960006 7 12 13 UPPER MIRROR CLAMP D960007 7 8 7+1 teflon LOWER CLAMP D960008-1 7 8 8 LOWER CLAMP, OPPOSITE D960008-2 7 8 8 WIRE CLAMP 1205308-1 10 17 9 CLAMP, SUSPENSION BLOCK D960134 14 19 21 STIFFENER PLATE D960009 7 9 9 DUMBBELL STANDOFF D970075 50 10 7 SAFETY STOP, LONG D970313 14 2 10 OSEM assy D960011 35 2 13 wire wound osem housings (gold) WIRE STANDOFF D970187 20 7 0 GUIDE ROD D970188 10 9 0 MAGNET D960501 50 54 51 rusted + 37 slightly rusted. Didn't put on table SAFETY STOP, SMALL D970312 28 0 4 SAFETY STOP D970311 28 0 16+9 stained w/o spring SS Spring Plunger 8498A999 35 4 27
Attachment 1: 20210204_144007.jpg
15797   Wed Feb 10 11:45:59 2021 AnchalSummaryBHDSatellite Amplifier Very Low frequency noise After modifications

As suggested, I wrapped the satellite amplifier box D10028128 S2100029 in blanket and foam and took very low frequency spectrum starting from 32 mHz to 3 Hz. The results are attached along with stiched high frequency measurements from 40m/15793.

# Very Low Frequency Spectrum Measurement

• D1002818 S2100029 box was powered and covered in a foam blanket.
• Additionally, it was covered from all sides with foam to reduce wind and temperature effects on it.
• The rear panel DB25 connector was connected to a breakout board where pins od PDA input and GND were shorted, shorting the transimpedance circuit input.
• The output was read from PDMon DB9 output at front panel which was converted to 4 BNC channels using breakout board.
• Two channel noise was measured at once using D1002818_SP.yml parameter file.
• Instrument noise at all the used input ranges were measured separately by shorting the input of the BNC cables.

Edit Wed Feb 10 15:14:13 2021 :

THIS MEASUREMENT WAS WRONG. SEE 40m/15799.

Attachment 1: FrontsideLook.jpg
Attachment 2: BacksideLook.jpg
Attachment 3: InnerFoamBlanket.jpg
Attachment 4: D1002818_S2100029_OutputNoiseLFSpecAfterChanges.pdf
Attachment 5: D1002818_S2100029_InputRefCurrentNoiseLFSpecAfterChanges.pdf
Attachment 6: AfterChangesLFSpectrum.zip
15799   Wed Feb 10 15:07:50 2021 AnchalSummaryBHDSatellite Amplifier Output Offset measurements

I measured the output DC voltage of the satellite amplifier box at PDMon port when the PDA input was shorted and got following offsets:

CH Output Offset (mV) CH Output Offset (mV)
1 6 5 750
2 140 6 120
3 350 7 537
4 40 8 670

However, I think I'm making a mistake while measuring this offset as well as all the noise measurements of this satellite amplifier box so far. Since it is a current input, transimpedance circuit, the noise of the circuit should be measured with open input, not closed. Infact, by shorting the PDA input, I'm giving DC path to input bias current of AD833 transimpedance amplifier to create this huge DC offset. This won't be the case when a photodiode is connected at the input which is a capacitor and hence no DC path is allowed. So my issue of offset was bogus and past two noise measurements in 40m/15797 and 40m/15793 are wrong.

15800   Wed Feb 10 15:25:45 2021 gautamSummaryBHDSatellite Amplifier Output Offset measurements

Why not just do this test with the dummy suspension box and CDS system? I think Rich's claim was that the intrinsic LED RIN was dominant over any drive current noise but we can at least measure the quadrature sum of the two (which is after all the relevant quantity in terms of what performance we can realize) and compare to a model.

15801   Wed Feb 10 17:18:03 2021 KojiSummaryBHDSatellite Amplifier Output Offset measurements

Testing the satellite amp i.e.  PD driver
- To test the noise of the PD transimpedance amps:
Leave the PD input open (do not short the terminal goes to the PD)
- To test the current noise of the LED drivers: Short the output with an appropriate Rs to have the nominal current.
- To test the overall noise level together with the LED/PD pair: Connect the dummy OSEM module.

Testing the coil drivers
-
Short the output with an appropriate Rs.

15803   Thu Feb 11 11:10:05 2021 AnchalSummaryBHDSatellite Amplifier Very Low frequency noise After modifications

Here is a proper measurement for PD transimpedance amplifier circuit in the Satellite amplifier box D1002818 S2100029. The input from rear DB25 connector was left open and measurement was taken with AC coupling with correction by the AC coupling transfer function (Zero at 0, pole at 160 mHz). I have calculated the input referred displacement noise by calculating the conversion factor of OSEM in A/m. From 40m/12470, old conversion factor of OSEM to output of sat amplifier was 1.6 V/mm. then, the transimpedance was 39.2 kOhm, so that must mean a conversion factor of 1.6e3/39.2 A/m. This I scaled with increased drive current by factor of 35/25 as mentioned in this document. The final conversion factor turned out to be around 57 mA / m. If someone finds error in this, please let me know.

There is excess noise in the low-frequency region below 5-6 Hz. If people think I should make a measurement of amplified noise to go further away from the instrument noise floor, let me know.

Attachment 1: AfterChangesSpectrum_AC.zip
Attachment 2: D1002818_S2100029_OutputNoiseSpecAfterChanges.pdf
Attachment 3: D1002818_S2100029_InputRefCurrentNoiseSpecAfterChanges.pdf
Attachment 4: D1002818_S2100029_InputRefDispNoiseSpecAfterChanges.pdf
15804   Thu Feb 11 16:58:52 2021 ranaSummaryBHDSatellite Amplifier Very Low frequency noise After modifications

I expect that a single OSEM channel can't be better than 1e-10 m/rHz above 5 Hz, so probably something wrong in the calibration. 1.6 V/mm seems right to me, so could be some place else.

15808   Tue Feb 16 13:13:39 2021 YehonathanUpdateBHDSOS assembly

Gautam pointed out that there are extra Sm-Co magnets stored in the clean optics cabinet.

I took the magnet box out and put it on the rolling table next to south flow bench. The box contains 3 envelopes with magnets.

They are labelled as following:

FLUX 94 - 50 parts

FLUX 93 - 10 parts

FLUX 95 - 40 parts

(What is FLUX??)

The box also contains some procurement documents.

The clean and bake dcc says :

1. Ultrasonic clean in methanol for 10 minutes

2. Bake in vacuum at 177 C° for 96 hours

Should we go ahead with the C&B?

15810   Tue Feb 16 15:29:01 2021 KojiUpdateBHDSOS assembly

The curie temp of SmCo seems about x2 (in K) of the one for NdFeB. i.e. 600K vs 1000K. So I believe 177degC = 450K is not an issue. Just make sure the curie temp, referring the specific property for the magnets from this company. (You already know the company from the procurement doc). It'd be great if you upload the doc on the 40m wiki.

15811   Tue Feb 16 22:59:36 2021 YehonathanUpdateBHDSOS assembly

Done.

Also, the magnets are nickel-plated. I guess that doesn't matter for the baking (Curie temp of 355 °C)?

 Quote: The curie temp of SmCo seems about x2 (in K) of the one for NdFeB. i.e. 600K vs 1000K. So I believe 177degC = 450K is not an issue. Just make sure the curie temp, referring the specific property for the magnets from this company. (You already know the company from the procurement doc). It'd be great if you upload the doc on the 40m wiki.

15821   Fri Feb 19 12:21:04 2021 YehonathanUpdateBHDSOS assembly

A summary of things that need to be fabricated/purchased/done:

 Part What needs to be done How much more needed SUSPENSION BLOCK Fabricate SS dowel pins for 1 suspension block. 2X(diameter 0.094"+-0.002, length 0.38"+-0.01)+2X(diameter 0.188"+-0.002, length 0.5"+-0.01) WIRE CLAMP If using the opposite side is acceptable, we have enough. DUMBBELL STANDOFF Fabricate. Schematics. Need to check the size is compatible with the magnets we have. 40 + 10 for double stacking of side dumbbells. With the existing dumbbells, we'll have 18 spares. SAFETY STOP, LONG Fabricate or buy. Schematics 4 OSEM assy Check if we have 35. Schematics SAFETY STOP, SMALL Fabricate or buy. Schematics 24 SAFETY STOP Fabricate or buy. Schematics 12 SS Spring Plunger Buy from McMaster. Find and check custom plungers around the X arm. 8 4-40 3/8" Ag SHCS Buy from uccomponents.com 30 4-40 1/2 Ag SHCS Buy from uccomponents.com 60 1/4-20 3/4 Ag SHCS Buy from uccomponents.com 150 1/4-20 5/4 Ag SHCS Buy from uccomponents.com 30 1/4 SS Lock Washer Buy from McMaster 30 1/4 SS Lock Wassher (Reduced OD) Buy from McMaster 30 Viton Tips Need to find stock Not sure. Existing eq stops have phosphor bronze springs. Should all of them be replaced with Viton? Steel Music Wire There are 500ft of wire (enough for many SOSs) in a desiccator somewhere according to this elog

15901   Thu Mar 11 02:10:06 2021 KojiSummaryBHDBHD Platform vertical dimentions

Stephen and I discussed the nominal heights of the BHD platform components.

• The beam height from the stack is 5.5"
• The platform height is 1.5" and the thickness of 0.4", according to the VOPO suspension, which we want to be compatible with.
• Thus the beam height on the BHD platform is 4".
• The VOPO platform has a minimum 0.1" gap from the installation surface when it is suspended.
• When the BHD platform is fixed on the table, we'll use positioners that are fixed on the stack table. Then the BHD platform is fixed on the positioner rather than fixing the entire platform on the stack. This leaves us the option to suspend the platform in the future. The number of the positioners is TBD.
• Looking at the head size for 1/4-20 socket head screws, It'd be nice to have the thickness of 0.5" for the positioners. This makes the thin part of the stiffener to be 0.6" in thickness.

• The numbers are nominal for the initial design and subject to the change along with FEA simulations to determine the resonant frequency of the body modes.
Attachment 1: BHD_Platform_Vertical_Dimentions.pdf
15909   Fri Mar 12 03:23:37 2021 KojiUpdateBHDDO card (DO-32L-PE) brought from WB

I've brought 4 DO-32L-PE cards from WB for BHD upgrade for Jon.

Attachment 1: P_20210311_232742.jpg
Attachment 2: P_20210311_232752.jpg
15922   Tue Mar 16 14:37:36 2021 YehonathanUpdateBHDSOS SmCo magnets Inspection

In the cleanroom, I opened the nickel-plated SmCo magnet box to take a closer look. I handled the magnets with tweezers. I wrapped the tips of the tweezers with some Kapton tape to prevent scratching and magnetization.

I put some magnets on a razor blade and took some close-up pictures of the face of the magnets on both sides. Most of them look like attachment 1.

Some have worn off plating on the edges. The most serious case is shown in attachment 2. Maybe it doesn't matter if we are going to sand them?

I measure the magnetic flux of the magnets by just attaching the gaussmeter flat head to the face of the magnet and move it around until the maximum value is reached.

For envelope #1 out of 3 the values are: (The magnet ordering is in attachment 3):

 Magnet # Max Magnetic Field (kG) 1 2.57 2 2.54 3 2.57 4 2.57 5 2.55 6 2.61 7 2.55 8 2.52 9 2.64 10 2.58

Going to continue tomorrow with the rest of the magnets. I left the magnet box and the gaussmeter under the flow bench in the cleanroom.

Attachment 1: 20210316_142906.jpg
Attachment 2: 20210316_165626.jpg
Attachment 3: 20210316_165838.jpg
15931   Wed Mar 17 14:40:39 2021 YehonathanUpdateBHDSOS SmCo magnets Inspection

Continuing with envelope number 2

 Magnet number Magnetic field (kG) 1 2.89 2 2.85 3 2.92 4 2.75 5 2.95 6 2.91 7 2.93 8 2.9 9 2.93 10 2.9 11 2.85 12 2.89 13 2.85 14 2.88 15 2.92 16 2.75 17 2.97 18 2.88 19 2.85 20 2.87 21 2.93 22 2.9 23 2.9 24 2.89 25 2.88 26 2.88 27 2.95 28 2.88 29 2.88 30 2.9 31 2.96 32 2.91 33 2.93 34 2.9 35 2.9 36 3.03 37 2.84 38 2.95 39 2.89 40 2.88 41 2.88 42 2.93 43 2.97 44 2.74 45 2.84 46 2.85 47 2.85 48 2.87 49 2.88 50 2.8

I think I have to redo envelope 1 tomorrow.

15964   Thu Mar 25 14:58:16 2021 YehonathanUpdateBHDSOS SmCo magnets Inspection

Redoing magnet measurement of envelope 1:

 Magnet # Max Magnetic Field (kG) 1 2.89 2 2.82 3 2.86 4 2.9 5 2.86 6 2.73 7 2.9 8 2.88 9 2.85 10 2.93

Moving on to inspect and measure envelope 3 (the last one):

 Magnet # Max Magnetic Field (kG) 1 2.92 2 2.85 3 2.93 4 2.97 5 2.9 6 3.04 7 2.9 8 2.92 9 3 10 2.92 11 2.94 12 2.92 13 2.92 14 2.95 15 3.02 16 2.91 17 2.89 18 2.9 19 2.86 20 2.9 21 2.92 22 2.9 23 2.87 24 2.93 25 2.85 26 2.88 27 2.92 28 2.9 29 2.9 30 2.89 31 2.83 32 2.83 33 2.8 34 2.94 35 2.88 36 2.91 37 2.9 38 2.91 39 2.94 40 2.88

15969   Fri Mar 26 10:25:37 2021 YehonathanUpdateBHDSOS assembly

I measure some of the dowel pins we got from Mcmaster with a caliper.

One small pin is 0.093" in diameter and 0.376" in length. The other sampled small pin has the same dimensions.

One big pin is 0.187" in diameter and 0.505" in length. The other is 0.187" in diameter and 0.506" in length.

The dowels meet our requirements.

15999   Tue Apr 6 15:42:57 2021 YehonathanUpdateBHDSOS assembly

We got some dumbells from Re-Source Manufacturing (see attached). I picked 3 in random and measured their dimensions:

1. 0.0760" in diameter, 0.0860" in length

2. 0.0760" in diameter, 0.0860" in length

3. 0.0760" in diameter, 0.0865" in length

In accordance with the Schematics.

Attachment 1: 20210406_150724.png
16011   Fri Apr 9 20:54:54 2021 YehonathanUpdateBHDSOS assembly

Today I assembled the skeleton of 6 towers, without clamps and sensor assembly (attachment 1).

Some of the side plates have this weird hole that doesn't fit any of the suspension blocks (attachment 2). I didn't notice when I counted the parts and now there are exactly enough side plates to assemble 7 towers.

Also found that one of the stiffener plates has a broken threading.

We will need more parts to go beyond the necessary 7 SOSs. I will do the recounting later.

Things to do next:

1. Find the capped spring plungers and send them to C&B.

2. Assemble the clamps onto the suspension blocks.

3. Push some Viton tips into the vented screws we got to make safety stops.

4. more C&B: Magnets, dumbells, dowel pins, OSEMs.

5. Push clean dowel pins into the last suspension block.

6. Assemble 7th Tower.

7. Assemble safety stops and clamps.

8. Glue magnets to dumbells.

Attachment 1: 20210409_202717.jpg
Attachment 2: 20210409_202755.jpg
16018   Mon Apr 12 17:30:11 2021 YehonathanUpdateBHDSOS assembly

Today, I screwed the plungers on the sensor plates and installed them on the Towers. I also installed the wire clamps on the suspension blocks (attachment).

I ran into problems in 2 separate suspension blocks: one had a dowel pin that was slightly too fat for the wire clamp. In another, the tapped holes were too short so that the 4-40 screws couldn't be screwed all the way.

Attachment 1: 20210412_170913.jpg
16111   Mon May 3 16:49:04 2021 YehonathanUpdateBHDSOS assembly

I found a "vice" in the cleanroom (attachment 1). I used it to push dowel pins into the last suspension block using some alcohol as a lubricant.

I then assembled the 7th and last suspension tower (attachment 2).

Things that need to be done:

1. Push Viton tips into vented screws and assemble the earthquake stops.

2. Glue magnets to dumbells.

Attachment 1: 20210503_161422.png
Attachment 2: 20210503_161456.jpg
16158   Mon May 24 20:55:00 2021 KojiSummaryBHDHow to align two OMCs on the BHD platform?

Differential misalignment of the OMCs

40m BHD will employ two OMCs on the BHD platform. We will have two SOSs for each of the LO and AS beams. The challenge here is that the input beam must optimally couple to the OMCs simultaneously. This is not easy as we won't have independent actuators for each OMC. e.g. The alignment of the LO beam can be optimally adjusted to the OMC1, but this, in general, does not mean the beam is optimally aligned to the OMC2.

Requirement

When a beam with the matched mode to an optical cavity has a misalignment, the power coupling C can be reduced from the unity as

$C = 1 - \left(\frac{a}{\omega_0}\right)^2 - \left(\frac{\alpha}{\theta_0}\right)^2$

where $\omega_0$ is the waist radius, $\theta_0$ is the divergence angle defined as $\theta_0 \equiv \lambda/ \pi \omega$, $a$ and $\alpha$ are the beam lateral translation and rotation at the waist position.

The waist size of the OMC is 500um. Therefore $\omega_0$ = 500um and $\theta_0$ = 0.68 mrad. If we require C to be better than 0.995 according to the design requirement document (T1900761). This corresponds to $a$ (only) to be 35um and $\alpha$ (only) to be 48urad. These numbers are quite tough to be realized without post-installation adjustment. Moreover, the OMCs themselves have individual differences in the beam axis. So no matter how we set the mechanical precision of the OMC installation, we will introduce a maximum of 1mm and ~5mrad uncertainty of the optical axis.

Suppose we adjust the incident beam to the OMC placed at the transmission side of the BHD BS. The reflected beam at the BS can be steered by picomotors. The distance from the BS to the OMC waist is 12.7" (322mm) according to the drawing.
So we can absorb the misalignment mode of ($a$, $\alpha$) = (0.322 $\theta$, $\theta$). This is a bit unfortunate. 0.322m is about 1/2 of the rayleigh range. Therefore, this actuation is still angle-dominated but a bit of translation is still coupled.

If we enable to use the third picomotor on the BHD BS mount, we can introduce the translation of the beam in the horiz direction. This is not too huge therefore we still want to prepare the method to align the OMC in the horiz direction.

The difficult problem is the vertical alignment. This requires the vertical displacement of the OMC. And we will not have the option to lower the OMC. Therefore if the OMC2 is too high, we have to raise the OMC1 so that the resulting beam is aligned to the OMC2. i.e. we need to maintain the method to raise both OMCs. (... or swap the OMCs). From the images of the OMC beam spots, we'll probably be able to analyze the intracavity axes of the OMCs. So we can always place the OMC with a higher optical axis at the transmission side of the BHD BS.

16170   Tue Jun 1 16:17:06 2021 YehonathanUpdateBHDSOS assembly

I tried to push the clean Viton tips into the vented screws just to find out that the vented holes are too small. We need to drill 0.1" diameter holes about 0.1" deep into these screws and clean them again.

16172   Wed Jun 2 01:03:19 2021 KojiUpdateBHDSOS assembly

Can you just cut the viton tips smaller? If you cut it to have some wedge (or say, taper), it can get stuck with the vent hole.

16198   Fri Jun 11 20:19:50 2021 KojiSummaryBHDBHD OMC invacuum wiring

Stephen and I discussed the in-vacuum OMC wiring.

- One of the OMCs has already been completed. (Blue)
- The other OMC is still being built. It means that these cables need to be built. (Pink)
- However, the cables for the former OMC should also be replaced because the cable harness needs to be replaced from the metal one to the PEEK one.
- The replacement of the harness can be done by releasing the Glenair Mighty Mouse connectors from the harness. (This probably requires a special tool)

- We want to combine the signals for the two OMCs into three DB25s. (Green)
- These cables are custom and need to be designed.

- The three standard aLIGO-style cables are going to be used. (Yellow)

- The cable stand here should be the aLIGO style.

Attachment 1: 40mBHD_OMC_wiring.pdf
16215   Fri Jun 18 19:02:00 2021 YehonathanUpdateBHDSOS assembly

Today I glued some magnets to dumbells.

First, I took 6 magnets (the maximum I can glue in one go) and divided them into 3 north and 3 south. Each triplet on a different razor (attachment 1).

I put the gluing fixture I found on top of these magnets so that each of the magnets sits in a hole in the fixture. I close the fixture but not all the way so that the dumbells get in easily (attachment 2).

I prepared EP-30 glue according to this dcc. I tested the mixture by putting some of it in the small toaster oven in the cleanroom for 15min at 200 degrees F.

The first two batches came out sticky and soft. I discarded the glue cartridge and opened a new one. The oven test results with the new cartridge were much better: smooth and hard surface. I picked up some glue with a needle and applied it to the surface of 6 dumbells I prepared in advance. I dropped the dumbells with the glue facing down into the magnet holes in the fixtures (attachment 3). I tightened the fixture and put some weight on it. I let it cure over the weekend.

I also pushed cut Viton tips that Jordan cleaned into the vented screws. While screwing small EQ stops into the lower clamps I found some problems. 4 of the lower clamps need rethreading. This is quite urgent because without those 4 clamps we don't have enough SOS towers. Moreover, I found that the screws that we bought from UC components to hold the lower clamps on the SOS towers were silver plated. This is a mistake in the SOS schematics (part 23) - they should be SS.

Attachment 1: 20210618_115017.jpg
Attachment 2: Untitled_2.png
Attachment 3: 20210618_160041_HDR.jpg
16216   Fri Jun 18 23:53:08 2021 KojiUpdateBHDSOS assembly

Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).

16221   Tue Jun 22 17:05:26 2021 YehonathanUpdateBHDSOS assembly

According to the schematics, the distance between the original EQ tap holes is 0.5". Given that the original tap holes' diameter is 0.13" there is enough room for a 1/4" drill.

 Quote: Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).

16227   Mon Jun 28 12:35:19 2021 YehonathanUpdateBHDSOS assembly

On Thursday, I glued another set of 6 dumbells+magnets using the same method as before. I made sure that dumbells are pressed onto the magnets.

I came in today to check the gluing situation. The situation looks much better than before. It seems like the glue is stable against small forces (magnetic etc.). I checked the assemblies under a microscope.

It seems like I used excessive amounts of glue (attachment 1,2). The surfaces of the dumbells were also contaminated (attachment 3). I cleaned the dumbells' surfaces using acetone and IPO (attachment 4) and scratched some of the glue residues from the sides of the assemblies.

Next time, I will make a shallow bath of glue to obtain precise amounts using a needle.

I glued a sample assembly on a metal bracket using epoxy. Once it cures I will hang a weight on the dumbell to test the gluing strength.

Attachment 1: toomuchglue1.png
Attachment 2: toomuchglue2.png
Attachment 3: dirtydumbell.png
Attachment 4: cleandumbell.png
Attachment 5: assembly_on_metalbracket.png
16229   Tue Jun 29 20:45:52 2021 YehonathanUpdateBHDSOS assembly

I glued another batch of 6 magnet+dumbell assemblies. I will take a look at them under the microscope once they are cured.

I also hanged a weight of ~150g from a sample dumbell made in the previous batch (attachments) to test the magnet+dumbell bonding strength.

Attachment 1: 20210629_135736.jpg
Attachment 2: 20210629_135746.jpg
16235   Thu Jul 1 16:45:25 2021 YehonathanUpdateBHDSOS assembly

The bonding test passed - the weight still hangs from the dumbell. Unfortunately, I broke the bond trying to release the assembly from the bracket. I made another batch of 6 dumbell+magnet.

I used some of the leftover epoxy to bond an assembly from the previous batch to a bracket so I can test it.

16259   Tue Jul 27 17:14:18 2021 YehonathanUpdateBHDSOS assembly

Jordan has made 1/4" tap holes in the lower EQ stop holders (attachment). The 1/4" stops (schematics) fit nicely in them. Also, they are about the same length as the small EQ stops, so they can be used.

However, counting all the 1/4"-3/4" vented screws we have shows that we are missing 2 screws to cover all the 7 SOSs. We can either:

1. Order new vented screws.

2. Use 2 old (stained but clean) EQ stops.

3. Screw holes into existing 1/4"-3/4" screws and clean them.

4. Use small EQ stops for one SOS.

etc.

Also, I found a mistake in the schematics of the SOS tower. The 4-40 screws used to hold the lower EQ stop holders should be SS and not silver plated as noted. I'll have to find some (28) spares in the cleanroom or order new ones.

Attachment 1: 20210727_154506.png
16260   Tue Jul 27 20:12:53 2021 KojiUpdateBHDSOS assembly

1 or 2. The stained ones are just fine. If you find the vented 1/4-20 screws in the clean room, you can use them.

For the 28 screws, yeah find some spares in the clean room (faster), otherwise just order.

16262   Wed Jul 28 12:00:35 2021 YehonathanUpdateBHDSOS assembly

After receiving two new tubes of EP-30 I resumed the gluing activities. I made a spreadsheet to track the assemblies that have been made, their position on the metal sheet in the cleanroom, their magnetic field, and the batch number.

I made another batch of 6 magnets yesterday (4th batch), the assembly from the 2nd batch is currently being tested for bonding strength.

One thing that we overlooked in calculating the amount of glue needed is that in addition to the minimum 8gr of EP-30 needed for every gluing session, there is also 4gr of EP-30 wasted on the mixing tube. So that means 12gr of EP-30 are used in every gluing session. We need 5 more batches so at least 60gr of EP-30 is needed. Luckily, we bought two tubes of 50gr each.

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