Sub-ASSY #10

Attachment #1: Mounting Block SN021

Attachment #2: PZT-Mounting Block bonding looks just excellent.

Attachment #3: The other side of the PZT-Mounting Block bonding is also excellent.

Attachment #4: The mirror-PZT bonding also look excellent. Some barrel fracture is visible at the lower left of the mirror.

Sub-ASSY #7

Probably the best glued unit among the four.

Attachment #1: Mounting Block SN001

Attachment #2: PZT-Mounting Block bonding looks completely wet. Excellent.

Attachment #3: The other side of the PZT-Mounting Block bonding. Also looks excellent.

Attachment #4: Overall look.

Attachment #5: The mirror-PZT bonding also look excellent. The mounting block surface has many EP30-2 residue. But they were shaved off later. The center area of the aperture is clear.

Attachment #6: A small fracture of the mirror barrel is visible (at 7 o'clock).

Sub-ASSY #8

Probably the best glued unit among the four.

Attachment #1: Mounting Block SN007

Attachment #2: Overall look.

Attachment #3: Some fracture on the barrel visible.

Attachment #4: It is visible that a part of the PZT removed. Otherwise, PZT-Mounting Block bonding looks pretty good.

Attachment #5: The other side of the PZT bonding. Looks fine.

Attachment #6: Fractured PZT visible on the fixture parts.

Attachment #7: Fractured glass parts also visible on the fixture parts.

Attachment #8: MIrror bonding looks fine except for the glass chip.

Sub-ASSY #9

The most fractured unit among four.

Attachment #1: Mounting Block SN017

Attachment #2: Two large removals well visbile. The bottom right corener was chipped.

Attachment #3: Another view of the chipping.

Attachment #4: PZT-mounting block bonding look very good.

Attachment #5: Another view of the PZT-mounting block bonding. Looks very good too.

Attachment #6: Fractures bonded on the fixture.

Attachment #7: Front view. The mirror-PZT bonding look just fine.

[Koji, Philip]

Today we tested the functionality of the four remaining PZTs (11,12,13 and 22) .  Each PZT was placed within a collimated 500um beam.
Roughly half of the beam was blocked by the PZT. The PZT and a PD then acted as shadow sensor. Each PZT was tested with 0 and
150 V. The resulting power change then could be converted into a displacement of the PZT using the beam diameter.

The open light value for each of these tests was 3.25 V.

PZT 11:
0 V supply voltage     --> 1.717 V on PD
150 V supply voltage --> 1.709 V on PD
delta = 0.008 V

PZT 12:
0 V supply voltage     --> 1.716 V on PD
150 V supply voltage --> 1.709 V on PD
delta = 0.007 V

PZT 13:
0 V supply voltage     --> 1.702 V on PD
150 V supply voltage --> 1.694 V on PD
delta = 0.008 V

PZT 22:
0 V supply voltage     --> 1.770 V on PD
150 V supply voltage --> 1.762 V on PD
delta = 0.008 V

0.008 V --> 0.24% change in power on PD --> about  3.8 um displacement assuming no light which is blocked
by the PZT is hitting the PD.

We further started to drive all four PZTs over night with 100 V (half of their range) at 100 Hz.
We additionally display the impedance to ensure none of them degrades.

All four PZTs seem to be connected to Teflon coated wires. It needs to be checked if these
fulfill the vacuum compatibility requirements.

Attachment 1: Shadow sensor setup for the PZT displacement test

Attachment 2: PZT endurance test. 4 PZTs were shaken at once.

Attachment 3~5: Function generator setup 100Hz, 3.5Vpp 1.75Voffset (meant be displayed for 50Ohm load)

Attachment 6: The above setting yields 7Vpp unipolar signal @Hi-Z load

Attachment 7: The output was monitored with a 1/10 probe with the PZTs connected. This shows 10Vmax 0Vin -> Good. This photo was taken at 17:35.

Attachment 8: The test is going well @9:15 next day. (t=15.7hours = 5.6Mcycles)

Attachment 9: The test went well. The modulation was stopped @15:35. (t=21hours = 7.6Mcycles)

After having dug into the past email, it turned out that these wires were the ones already replaced from the original teflonwires. The length of them were confirmed to be ~19" (480mm). 

(Now the CCD image is captured as a movie and the screen capture is easier!)

Various spot positions on CM1 and CM2 were tried to test how the transmission is dependent on the spot positions. CM1 has a few bright spots while CM2 shows very dark scattering most of the case. Attachment 1 is the example images of one of the best alignment that realized the transmission of ~96%. FM1 and FM2 also showed bright spots. The replacement of the FM mirrors does not improve nor degrade the transmission significantly. The transmission is still sensitive to the spot positions on the alignment. This indicates that the loss is likely to be limited by CM1.

Attachment 2 shows the distribution of the (known) scattering spots on CM1. The bright spots are distributed every ~1mm on the spot height and the beam (with beam radius of .5mmm) can't find a place where there is no prominent spots.

We will be able to examine if the transmission can be improved or not by replacing this CM1 mirror.

Similarly to OMC ELOG 349 the spot positions after the replacement of CM2 were measured (Attachment 1)
Also, the spot positions after the realignment were measured. (Attachment 2)

Tried a few things.

1. Replaced CM1 (PZT ASSY #10=M21+PZT#22+C12) with PZT ASSY #7 (=M1+PZT#13+C13)

We tried PZT ASSY #7 at the beginning and had the spots at almost at the top edge of the curved mirrors. As we found a particle on the bottom of the M1 prism (and removed it), I gave it a try again. Resulting spots are again very high. This results in rejecting PZT ASSY #7 and we set the combination of the PZT ASSYs as #8 (M7+P11+C11) and #10 (M21+P22+C12). This combination nominally gives the spot ~1mm above the center of the curved mirrors.

2. Swapped FM1 and FM2. Now FM1=A5 and FM2=A14.

No significant change of the scattering features on the FMs. The transmitted power was 14.85mW (Ref PD Vin = 3.42V), Reflection PD Vrefl,lock = 54.3mV and Vrefl,unlock = 2.89V (Vin=3.45V), Vrefl,offset = -6.39mV. The incident power was 17.43mW (Vin 3.69V).

==> Coupling 0.979 , OMC transmission 0.939 (This includes 0.6% loss to the QPD path) ...Not so great number

3. Built better camera setups to check the spot position and the scattering from the cavity mirrors.

Now the spot heights are fixed and safe to move the camera up for inches to obtain better views of the mirror faces. The camera was set 15" away from the mirrors with 1.5" height from the beam elevation. This is 0.1rad (~ 5 deg) and Cos(0.1)~0.995 so the distortion (compression) of the view is negligible. (Attachment) The spot photo were taken with the fixed CCD gain, the focus on the glass, and  lens aperture F=8.0. Later the focus and aperture were adjusted to have clear view of the scattring points.

The intensity of each scattering was constant at different views. I suppose this is because the scattering is coming from a spot smaller than the wavelength. The bright spots does not show any visible feature on the mirror surfaces when they were inspected with a green flash light.

CM2 has the excellent darkness and we want to keep this spot position. FM1, FM2, and CM1 showed bright scattering.

The spot at CM1 is not well centered on the mirror. And this is the way to avoid this scattering point. So let's think about to move the spot on CM1 by 1.3mm towards the center while the spot on the CM2 is fixed. Note that this is going to be done by the micrometers for CM1 and CM2.

By turning right micrometer of CM1 forward (50um = 5div = 1/10 turn) and the left micrometer of CM2 backward (60um = 6div) moves the spots on FM1, FM2, CM1, and CM2 by (0.43, 0.87, 1.3, 0)mm. This basically moves the spots toward the center of each mirror. Let's give it a try.

Experiment on 5/1
- CM1 right knob was moved 1div (10um) backward such that the spots were better centered on the mirrors 
FM1 (A5): h=-0.2mm -> 0.4mm made the spot much darker but still it has a few scattering spots.
FM2 (A14): h=-0.8mm -> 0.2mm reduced the number of spots from 2 to 1. And it is darker. The remaining spot at the center.
CM1 (C11): h=-1.3mm -> +1.0mm made the spot much darker.
CM2 (C12): h=-0.7mm -> +0.2mm remains dark.

Note: CM1 h=1mm and CM2 h~0mm are good locations. h+ is the good direction to move. Avoid h-.
FM1 and FM2 has the scat spots at the center. Want to go h+ more.

Uniformly go h+ is the good move. => This can be done by rotate CM1 positive => CM1 right knob CCW.

Improvement of the transmission from 93.9%->95.3%

- Further moved CM1 right knob 0.5div (0.5um) backward such that the spots were moved to h+ directions.
FM1 (A5): h=0.4mm -> 1.1mm (there is only one spot rather than multiple spots)
FM2 (A14): h=0.2mm -> 1.1mm (darker but multiple spots)
CM1 (C11): h=1.0mm -> 1.8mm (brighter but single spot)
CM2 (C12): h=0.2mm -> 1.5mm (dark multiple spots)

Not much improvement of the transmission but kept 95% level.

- Replaced FM1 (A5) with A1 mirror (No photo)

Good news: This did not change the cavity alignment at all.

Transmission 95.4%

- Tweaked the CM1 angle

Transmission 95.3%

=> A1 mirror does not improve the transmission much.

Next Plan: Use A5 (or something else) as FM2 and see if A14 caused the dominant loss.

[Stephen, Philip, Koji, Joe]

Breadboard D1200105 SN06 was selected as described in eLOG 338. This log describes unwrapping and preparation of the breadboard.

Relevant procedure section: E1300201 section 6.1.5

Breadboard was unwrapped. No issues observed during unwrapping.

• Attachment 1: packaging of SN06.

Visual inspection showed no issues observed in breadboard - no large scratches, no cracks, no chipping, polished area (1 cm margin) looks good.

• Attachment 2: engraving of SN06.

Initially the breadboard has a large amount of dust and fiber from the paper wrapping. Images were gathered using a green flashlight at grazing incidence (technique typical of optic inspection).

PROCEDURE IMPROVEMENT: Flashlight inspection and Top Gun use should be described (materials, steps) in E1300201.

• Attachment 3: particulate before Top Gun, large face.
• Attachment 4: particulate before Top Gun, small face.

Top gun was used (with medium flow rate) to remove large particulate. Breadboard was placed on Ameristat sheet during this operation.

• Attachment 5: particulate after Top Gun

Next, a clean surface within the cleanroom was protected with Vectra Alpha 10 wipes. The breadboard, with reduced particulate after Top Gun, was then placed inside the cleanroom on top of these wipes. Wiping with IPA Pre-wetted Vectra Alpha 10 wipes proceeded until the particulate levels were acceptable.

Joe and Koji then proceeded with placing the breadboard into the transport fixture.

Preparation for the PZT subassembly bonding (Section 6.2 and 7.3 of T1500060 (aLIGO OMC optical testing procedure)
- Gluing fixture (Qty 4)
- Silica sphere powder
- Electric scale
- Toaster oven for epoxy mixture qualification

- M prisms
- C prisms
- Noliac PZTs

- Cleaning tools (forceps, tweezers)
- Bonding kits (copper wires, steering sticks)
- Thorlabs BA-2 bases Qty2
- Razor blades

Also brought to the 40m on 10 April, in preparation for PZT subassembly bonding:

- new EP30-2 epoxy (purchased Jan 2019, expiring Jul 2019 - as documented on documents attached to glue, also documented at C1900052.

- EP30-2 tool kit (maintained by Calum, consisting of mixing nozzles, various spatulas, etc)

Already at the 40m for use within PZT subassembly bonding:

- "dirty" ABO A with temperature controller (for controlled ramping of curing bake)

- clean work areas on laminar flow benches

- Class B tools, packaging supplies, IPA "red wipes", etc.

Upon reviewing EP30-2 procedure T1300322 (current revision v6) and OMC assembly procedure E1300201 (current revision v1) it appears that we have gathered everything required.

[Koji Jeff]

In order to prepare for the splinkler installation on the HEPA enclosure, the table with the optics was wrapped with Ameristat sheets.

Link to the "Mirror/PZT Characterization links"

Breadboard

BB1 OMC(001) OMC
BB2 OMC(002) OMC
BB3 -
BB4 OMC(003) OMC
BB5 -
BB6 -

Mounting Prisms:

M01
M02
M06 OMC(002) CM1 (PZT ASSY #6)
M07
M10 OMC(003) CM1 (PZT ASSY #5)
M11 OMC(002) CM2 (PZT ASSY #4)
M12
M13 OMC(003) CM2 (PZT ASSY #3)
M14
M15
M16 OMC(001) CM1 (PZT ASSY #1)
M17
M20 OMC(001) CM2 (PZT ASSY #2)
M21
M22 

Mirror A:
A1  fOMC FM1
A2  Fullerton for the scattering measurement
A3  fOMC FM2
A4 
A5 
A6  OMC(003) FM2
A7  OMC(001) FM2
A8  OMC(001) FM1
A9  OMC(002) FM1
A10
A11
A12 OMC(003) FM1
A13 OMC(002) FM2
A14 

Mirror B:
B1 
B2 
B3  OMC(001) BS2 (QPD)
B4 
B5  OMC(003) BS2 (QPD)
B6 
B7  OMC(001) BS3 (DCPD)
B8 
B9  OMC(002) BS2 (QPD)
B10 OMC(002) BS3 (DCPD)
B11
B12 OMC(003) BS3 (DCPD)

Mirror C:

C1 OMC(003) CM1 (PZT ASSY #5)
C2 Fullerton for the scattering measurement
C3 OMC(003) CM2 (PZT ASSY #3)
C4 OMC(002) CM2 (PZT ASSY #4)
C5 OMC(001) CM2 (PZT ASSY #2)
C6 OMC(001) CM1 (PZT ASSY #1)
C7 fOMC CM1
C8 fOMC CM2 -> OMC(002) CM1 (PZT ASSY #6)
C9 OMC(002) CM1 (PZT ASSY #6) -> BURNT
C10 (Liyuan tested)
C11 (Liyuan tested)
C12 curvature untested, faux OMC CM2
C13 curvature untested

Mirror E:
E1  OMC(002) SM2
E2  OMC(002) SM3
E3  OMC(002) BS1
E4  OMC(001) SM2
E5  OMC(002) SM1
E6 
E7  OMC(003) BS1
E8  OMC(003) SM1
E9 
E10 OMC(001) BS1
E11
E12 OMC(001) SM1
E13 OMC(003) SM2
E14
E15
E16 OMC(001) SM3
E17 OMC(003) SM3
E18

PZT:
PZT11
PZT12
PZT13
PZT14 OMC(003) CM1 (PZT ASSY #5)
PZT15 OMC(003) CM2 (PZT ASSY #3)
PZT21 OMC(002) CM1 (PZT ASSY #6)
PZT22
PZT23 OMC(001) CM2 (PZT ASSY #2)
PZT24
PZT25 OMC(002) CM2 (PZT ASSY #4)
PZT26 OMC(001) CM1 (PZT ASSY #1)

The backscatter beam is supposed to appear in the backpropagation path. The transmission of the OMC has a couple of optics, it's not easy to access that beam.
To try to deflect the beam either horizontally or vertically, small optical pieces were made. (Attachment)

These are the combination of the optics

- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs 1/2"sq BB Dielectric Mirror BBSQ05-E03

- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs ME05-G01 Protected Al Mirror (dia12.7mm x t 3.2mm) + Thorlabs MRA10-K13 Right-Angle Prism Nd:YAG 10mm

Torr seal was used as the bonding epoxy. It uses a 1:2 volume mixture (not easy because of the viscosity) and is relatively fast to cure (in a couple of hours).
The test piece showed some softness after 3~4 hours so I left the parts cured overnight at room temp (i.e. 18degC)

Motivation: Characterize the loss of the Calcite Brewster PBS.

Setup: (Attachment 1)

- The beam polarization is rotated by an HWP
- The first PBS filters out most of the S pol
- The second PBS further filters the S and also confirms how good the polarization is.

- The resulting beam is modulated by a chopper disk. The chopping freq can be 20~1kHz.

- The 50:50 BS splits the P-pol beam into two. One beam goes to the reference PD. The other beam goes to the measurement PD.

- Compare the transfer functions between RefPD and MeasPD at the chopping frequency with and without the DUT inserted to the measurement pass.

- The PBS shift the beam significantly. The beam can't keep the alignment on the Meas PD when the crystal is removed.
  Therefore the "On" and "Off" states are swicthed by moving the PBS and the steering mirror at the same time.
  The positions and angles of the mounts are defined by the bases on the table. The bases are adjusted to have the same spot position for these states as much as possible.

Device Under Test:

Brewster polarizer https://dcc.ligo.org/LIGO-T1300346

The prisms are aligned as shown in Attachment 2

Between the prisms, a kapton sheet (2MIL thickness) is inserted to keep the thin air gap between them.

Result:

Set1: (~max power without hard saturation)
PD1(REF) 10dB Gain (4.75kV/A) 6.39V
PD2(PBS) 10dB Gain (4.75kV/A) Thru 4.77V, PBS 4.75
Chopping frequency 234Hz, FFT 1.6kHz span AVG 20 (1s*20 = 20s)

Thru 0.748307, PBS 0.745476 => 3783 +/- 5 ppm loss
Thru 0.748227, PBS 0.745552 => 3575 +/- 5 ppm
Thru 0.748461, PBS 0.745557 => 3879 +/- 5 ppm
Thru 0.748401, PBS 0.745552 => 3806 +/- 5 ppm
Thru 0.748671, PBS 0.745557 => 4159 +/- 5 ppm
=> Loss 3841 +/- 2 ppm

Set2: (half power)
PD1(REF) 10dB Gain (4.75kV/A) 3.20V
PD2(PBS) 10dB Gain (4.75kV/A) Thru 2.38V, PBS 2.37
Chopping frequency 234Hz, FFT 1.6kHz span AVG 20 (1s*20 = 20s)

Thru 0.747618, PBS 0.744704 => 3898 +/- 5 ppm loss
Thru 0.747591, PBS 0.744690 => 3880 +/- 5 ppm
Thru 0.747875, PBS 0.744685 => 4265 +/- 5 ppm
Thru 0.747524, PBS 0.744655 => 3838 +/- 5 ppm
Thru 0.747745, PBS 0.744591 => 4218 +/- 5 ppm
=> Loss 4020 +/- 2 ppm

Set3: (1/4 power)
PD1(REF) 10dB Gain (4.75kV/A) 1.34V
PD2(PBS) 10dB Gain (4.75kV/A) Thru 1.00V, PBS 0.999
Chopping frequency 234Hz, FFT 1.6kHz span AVG 20 (1s*20 = 20s)

Thru 0.745140, PBS 0.741949 => 4282 +/- 5ppm loss
Thru 0.745227, PBS 0.741938 => 4413 +/- 5ppm
Thru 0.745584, PBS 0.741983 => 4830 +/- 5ppm
Thru 0.745504, PBS 0.741933 => 4790 +/- 5ppm
Thru 0.745497, PBS 0.741920 => 4798 +/- 5ppm
Thru 0.745405, PBS 0.741895 => 4709 +/- 5ppm
=> Loss 4637 +/- 2ppm

Possible improvement:

- Further smaller power
- Use the smaller gain as much as possible
- Compare the number for the same measurmeent with the gain changed

- Use a ND Filter instead of HWP/PBS power adjustment to reduce incident S pol
- Use a double pass configuration to correct the beam shift by the PBS

To be measured

- Angular dependence
- aLIGO Thin Film Polarizer
- HWP
- Glasgow PBS

Calcite Brewster PBS Continued

The transmission loss of the Calcite brewster PBS (eLIGO squeezer OFI) was measured with different conditions.
The measured loss was 3600+/-200ppm. (i.e. 900+/-50 ppm per surface)
The measurement error was limited by the systematic error, probably due to the dependence of the PD response on the spot position.

I wonder if it is better to attenuate the beam by a ND filter instead of HWP+PBS.

o First PBS power adjustment -> full power transmission, OD1.0 ATTN Full Power
   PDA20CS Gain 10dB
   Thru 0.746711, PBS 0.744155 => Loss L = 3423 +/- 5ppm

o Same as above, PDA20CS Gain 0dB (smaller amplitude = slew rate less effective?)
   Thru 0.748721, PBS 0.746220 => L = 3340 +/- 5ppm

o Same as above but OD1.4 ATTN
   Thru 0.744853, PBS 0.742111 => L = 3681 +/- 5ppm

o More alignment, more statistics
(PDA20CS 0dB gain =  0.6A/W, 1.51kV/A)
PD(REF, 0dB) 0.426V = 0.47W
PD(MEAS, 0dB) Thru 0.320V, PBS 0.318V = 0.35W, L = 6000+/-3000ppm

Chopping 234Hz, TF 1.6kHz AVG10
Thru 0.745152, PBS 0.742474 => 3594 +/- 5 ppm
Thru 0.745141, PBS 0.742467 => 3589 +/- 5ppm
Thru 0.745150, PBS 0.742459 => 3611 +/- 5ppm
Thru 0.745120, PBS 0.742452 => 3581 +/- 5ppm
Thru 0.745153, PBS 0.742438 => 3644 +/- 5ppm
=> 3604ppm +/-25ppm

o More power

Attenuation OD 1.0
PD(REF, 0dB) 0.875V = 0.97W
PD(MEAS, 0dB) Thru 0.651V, PBS 0.649V = 0.72W, L = 3100+/-1600ppm

Chopping 234Hz, TF 1.6kHz AVG10
Thru 0.746689, PBS 0.743789 => 3884 +/- 5ppm
Thru 0.746660, PBS 0.743724 => 3932 +/- 5ppm
Thru 0.746689, PBS 0.743786 => 3888 +/- 5ppm
Thru 0.746663, PBS 0.743780 => 3861 +/- 5ppm
Thru 0.746684, PBS 0.743783 => 3885 +/- 5ppm
=> 3890ppm +/- 26ppm

o Much less power

Attenuation OD 2.4
PD(REF, 0dB) 67.1mV = 74.0mW
PD(MEAS, 0dB) Thru 53.7V, PBS 53.5V = 59mW, L = 3700+/-1900ppm

Thru 0.745142, PBS 0.742430 => 3640 +/- 5ppm
Thru 0.745011, PBS 0.742557 => 3294 +/- 5ppm
Thru 0.744992, PBS 0.742537 => 3295 +/- 5ppm
Thru 0.745052, PBS 0.742602 => 3288 +/- 5ppm
Thru 0.745089, PBS 0.742602 => 3338 +/- 5ppm
=> 3371ppm +/- 151ppm

o Much less power, but different gain

Attenuation OD 2.4
PD(REF, 20dB) 662mV = 73.1mW
PD(MEAS, 20dB) Thru 501V, PBS 500V = 55.3mW, L = 2000+/-2000ppm

Thru 0.744343, PBS 0.741753 => 3480 +/- 5ppm
Thru 0.744304, PBS 0.741739 => 3446 +/- 5ppm
Thru 0.744358, PBS 0.741713 => 3553 +/- 5ppm
Thru 0.744341, PBS 0.741719 => 3523 +/- 5ppm
Thru 0.744339, PBS 0.741666 => 3591 +/- 5ppm
=> 3519ppm +/- 58ppm

Using the last 4 measurements, mean loss is 3596, and the std is 218. => Loss = 3600+/-200ppm

 shim 1.5mm 001/002

Upon the LLO work, the current PD arrangement in the cages are:
CAGE B
B1 OMC1 PDT (A1-23)
B2 OMC1 PDR (A1-25)
B3 original (C1-03)
B4 OMC2 PDT (B1-22)

CAGE C
C1 OMC2 PDR (B1-23)
C2 original (C1-08)
C3 original (C1-09)
C4 original (C1-10)

On friday, I removed a glass cover of a G30655 with a PD can cutter.

When a beam shoots a Perkin Elmer/Excelitas PD, we usually observe three reflections.
We always wonder what these are.

When the glass window is illuminated by a beam, I could see two reflections. So they are the front and rear reflection from the glass windows.

DCPD2 got misaligned during the cable installation. The PD alignment procedure have been gone through again.

Cavity locking

- Removed the FC layers for the cavity related mirrors.

- Aligned and locked the cavity.

PD alignment

- Loosen DCPD2. Checked the reflection with a IR card. Checked the spot on the PD with an IR viewer.

- Finger-tight the screws. Check the reflection with the card again. Check the pot on the PD with a CCD.

- If the spot positions are not satisfactory repeat the process.

- If the spot positions are satisfactory, take pictures of the CCD image.

- Fixing screws for all of the PDs/QPDs were tighten by the torque driver with a torque od 1.75 inch lb.

PD QE measurements

- Measure the power incident on the PDs.

- Set up the transimpedance amp to check the photo current.

- PD1 (T side) 9.10+/-0.03 V 13.02 +/- 0.01W -> QE ~80%

- PD2 (R side) 8.70+/-0.01 V 12.53 +/- 0.01W -> QE ~80%

- These are not strange values considering the presence of the glass caps.

PZT polarity check

- The connections between the PZT electrodes and the pins were checked.

- The positive side is marked by a knot on the wire.

FC painting

- The new FC bottle was brought from Downs, thanks to Margot.

[Jeff Koji]

- Placed the optics on the PD/QPD path

- Checked the alignment of the beam on the dummy PD/QPD mounts

- There is a bit of (~0.5mm) shift of the spot position from the center. Mainly downward. This is well within a ball park of the PD mounts.

- The PD/QPD path gluing will take place tomorrow.

- Went to the 40m and received the DCPDs from Bob's lab.

- Took six ISC QPDs for the sake of the OMCs.

- They are now in the OMC lab. 

- Measured the B mirror / E mirror R&Ts.

- Found anomalously high loss (3%) for the B mirrors (BSs)

- Went through the all mirrors. Some mirrors (3 or 4) seemed less lossy (<~1%). They will be used for the DCPD BS.

Attachment 1: PDH amp RF part (before the preamp was installed)

Attachment 2: RF-AF transmission

Attachment 3: Attachment 3: LO dependence

Attachment 4: RF amp gain (saturation)

Attachment 5: Input/output noise level

Attachment 6: Attachment 6: Preamp/DCPD out buffer AF circuit

attachment 6: DCPD preamp looks like the opamp is wired for positive feedback?

The polarities indicated in the right circuits were opposite, obviously.

Mode cleaning capability of an optical fiber was measured. The conclusion is that the leakage of the non-fiber mode to the fiber output is insignificant and also practically negligible.

The tested fiber was Thorlabs 5-m Polarization Maintaining Single-Mode fiber (P3-1064PM-FC-5, PM Patch Cable, PANDA, 1064 nm, FC/APC, 5m).

The output mode cleaner was used as a mode analyzer. The fiber input was aligned and the misaligned so that the amount of higher order mode for the fiber is changed. The fiber output has been mode matched to an output mode cleaner. Therefore excess mode mismatch when the fiber input was misaligned, was accounted as the leakage higher order mode.

For each alignment state, the OMC transmission (in V), the OMC reflection (in V), and the OMC reflection with the OMC unlocked were measured. The voltages were measured with a digital multimeter (non-portable unit). With the fiber input beam aligned to the fiber, the fiber input and output powers were measured with a power meter.

With the input beam aligned
- Fiber input: 52.5 +/- 0.2 [mW]
- Fiber output: 35.5 +/- 0.2 [mW] (~68% coupling)
- Reflection PD offset: -0.00677 +/- 0.00001 [V]

- Refl PD reading with the OMC unlocked: 6.32 +/- 0.01 [V]
- Refl PD reading with the OMC locked: 0.133 +/- 0.002 [V]
- OMC Trans PD with the OMC locked: -1.72 +/- 0.01 [V] 

With the input beam misaligned
- Refl PD reading with the OMC unlocked: 3.63 +/- 0.01 [V]
- Refl PD reading with the OMC locked: 0.0752 +/- 0.001 [V]
- OMC Trans PD with the OMC locked: -1.00 +/- 0.01 [V] 

The naive mode matching was 0.9779 +/- 0.0003 and 0.9775 +/- 0.0003 without and with misalignment. We initially had roughly 17mW of non-fiber mode incident. And it was increased by roughly 15mW. For the misaligned case, the amount of the OMC-matched carrier was also reduced due to the misalignment. So the actual fiber mode cleaning effect needs more careful quantitative analysis.

The power budget at each part of the setup was modeled as shown in Attachment 1. The blue numbers are the measured values.
The factor a is the ratio of the leakage non-fiber mode into the fiber transmission.
The factor (1-b) is the mode matching of the fiber mode into the OMC mode.

and

With the calibration between the refl PD and the power meter measurement,
 

The solution of the equations is

So, the leakage of the non-fiber mode to the fiber output is insignificant. Moreover, the number is practically negligible because the mismatching between the fiber and OMC modes is of the order of percent and dominated by the aberration of the collimator (i.e. the OMC reflection looks like concentric higher-order LG modes) with the order of 1~2%.
 

Assembly #1:

Mounting Prism #16
PZT #26
Mirror C6

Assembly #2:

Mounting Prism #20
PZT #23
Mirror C5

Yesterday, Jeff and I bonded the PZT assemblies (#3/#4).
The attached is the arrangement of the components

PZT Assembly #5/#6 were glued on Fri Aug 9th

They are removed from the fixture on Mon Aug 12th.

All of the four PZT assemblies were moved to the OMC lab.

12 May 2023, Downs 227

Stephen, Camille, Thejas

We completed a first batch of PZT DC response measurements, and we are working on the processing of quantitative results.

For now, presented below are some general observations and remarks, as well as qualitative results for the full set of 18 PZTs.

General observations

• The following improvements have helped us graduate to observing and measuring DC response:
  • Improving our drive electronics (better function generator, direct monitoring of function generator output and PZT drive amplifier input)
  • Improving our experimental design (focusing and collimating of input beam allowed greater sensitivity to same PZT motion)
  • Improving our signal chain (PD to SR785 Spectrum Analyzer allowed better resolution and reduced systematic noise)
• It seems that Qty 2 of the PZTs that we handled a lot during our test setup may have degraded due to some inattention or accidental mistakes.
• Qty 5 PZTs had solder preventing uniform contact with the end face, which seemed to effect our ability to observe well-resolved DC response.
  • Resoldering next for these articles!
  • We had not clearly specified that there was a restriction to the extent of the solder joint - something to add to the DCC entry for the PZT. We'd also like to recommend that specific soldering steps for the leads be documented here!
• The remaining articles were characterized using a 0.5 Hz triangle wave of range 0-150 Hz, sampled for 8 seconds on a SRS785 Spectrum Analyzer.

Qualitative DC Response Results

11 PZTs are Good (DC Response measured)
36 - labeled "?" due to a fair amount of initial handling
37 - good
38 - good
39 - somewhat high intrinsic noise
41 - good
42 - good
43 - good 
44 - good
46 - good
47 - good
48 - good

5 PZTs are WIP (Still need to measure DC Response)
31 - Solder extends past end face
32 - Lead Desoldered
35 - Solder extends past end face
40 - Solder extends (maybe) past end face
45 - Solder blob on ID of end face

2 PZTs are Bad (Inadequate DC response)
33 - 150 V applied in reverse due to lead polarity mistake; still buzzes, but now DC response is unreliable
34 - Low DC response, maybe because we were using it in tests?

Next Steps

We need to remeasure the 5 PZTs that had soldering issues. We'll call this Batch 2.

Soon we will finish analyzing the quantitative response, with an output of PZT Displacement per Drive Voltage.

Then we will decide whether we are happy to move forward without additional PZT spares to replace the faulty articles, or if we want to order additional units.

We also will continue characterizing the PZT Length-to-Angle Coupling and Reliability, per OMC Testing Procedure ref. T1500060-v2 PZT Testing Sections Section 2.3.2 and 2.3.4

[Stephen, Camille, Thejas]

A running log of our efforts from Monday 1 May. Data continues to be placed in T2300050 at sheet "PiezoDCResponse":

• Continuing with the DCPD and 3-axis piezo driver for our "final" setup
  • PD Thorlabs
  • Driver Thorlabs MDT694B
  • Function Generator in line
• "Averaging" mode of the oscilloscope only reported 3 significant figures, so there was no benefit from switching away from "Sampling" mode
• Acoustic buzzing test of PZT 36 and PZT 31 yielded consistent results
  • Audible buzzing tone with 1 kHz, 10 Vpp input
  • Reverse polarity also buzzes
• We attempted on/off testing, and also AC drive testing, for PZTs 31, 32, and 36
  • PZT 36 was used in the initial setup effort, and since there was inadequate insulation of the PZT from the setup, there was charge buildup and static discharge during that early effort. This PZT was chosen because it has the greatest wedge. We should be skeptical of it now that we have used it in these setup efforts.
  • PZT 31 was used next, also during setup but only after adequate insulation of the PZT had been implemented. It probably has been treated well! Except during today's efforts, one of the solder joints debonded. (Need to follow up with Dean to confirm that LIGO soldering practice follows recommendations of vendor - pads should be clean, solder should include Ag; see D1102070 and other sources)
  • PZT 32 was used afterwards, and was measured.
• We were not really satisfied with the "feel" of the measurement
  • The oscilloscope output didn't seem to change on time scales that we were expecting, when we manipulated the frequency of the drive
  • We attempted to directly measure the PZT extension using the dial indicator, but did not succeed
• We tried to make a list of items that we didn't understand fully, and came up with these:
  • We aren't really that familiar with the driver/amplifier and how it interacts with the input from the function generator:
    • Thorlabs documentation was reviewed - driver manual
      • https://www.thorlabs.com/drawings/d90d63f542e805de-80E05D38-00C3-80BB-4CF17F9FDBF42AB6/MDT693B-Manual.pdf
    • V_out = V_manual + 15 * V_external
      • We applied a 2 V peak-to-peak external voltage, so we were not driving through the full range of the output voltage
      • We may benefit from a low frequency, triangular wave drive so that we can better monitor the output voltage
  • Maybe the time constant of the capacitive charging is too long?
    • Thorlabs documentation was reviewed - Piezo Bandwidth section of Piezo Tutorial
      • https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5030
    • Slew rate (rate of capacitive charging, V/s) is more complicated for a sinusoidal wave than a triangular wave, but the maximum is characterized by the Maximum Driver Current / System Capacitance.
      • Max Driver Current I_max = .06 A, System Capacitance C_sys = C_PZT + C_driver = 5.1 E-7 F + 1 E-9 F
      • Slew rate = 1.18 E5 V/s, or a charging time of 1.28 E-3 s to reach 150 V (note that this is not a true value as the input waveform was sinusoidal)
    • More helpfully, the system bandwidth for a sinusoidal wave is f_max = I_max / (pi * V_pp * C_sys); a triangular wave with a minimum of 0 V is f_max = I_max / (V_pp * C_sys)
      • Our system, if driven sinusoidally from 0 to 150 V, would have a bandwidth of 249 Hz
      • Our system, if driven triangularly from 0 to 150 V, would have a bandwidth of 783 Hz
• We should try to get a low frequency triangular wave drive output from 0 to 150 V with a frequency of 100 Hz, and see if that generates any meaningful signal.

The measurement "results" for PZT 32 (note that these results seem to be dominated by a slow drift in the measurement, and this measurement was not reproducible):

• PD signal with PZT 32 on (150 V) : 3.242934 V, standard deviation 0.013894 V
• PD signal with PZT 32 off (0 V): 3.315395 V, standard deviation 0.014658 V
• sensitivity: -13.65102 V per mm PZT displacement
  • (from PD Calibration, removing factor of 10 from oscilloscope during that measurement)
• displacement of PZT = 5.308 microns
  • the standard deviation of the On measurement was 1.018 microns, and the standard deviation of the Off measurement was 1.074 microns.
• Conclusion: this measurement has a rather large error bar, and was not very repeatable / could not be directly observed by another means (see above comments in log) we were not really satisfied with the "feel" of the measurement
  • The oscilloscope output didn't seem to change on time scales associated with low frequency AC drive; Since high frequency AC drive does cause motion (witnessed by buzzing) maybe we need to find other ways to measure the motion that are more sensitive?

Efforts from Tuesday through Thursday Wednesday, 02 through 04 May, are described below.

The main outcomes were:

• We are able to see some response in the frequency domain (which confirms the response that we hear at acoustic drive frequencies) on a few PZTs Wednesday and Thursday.
• We then improved our drive input and monitoring, so we now see the full waveform delivered to the PZT.
• Now, we are able to reliably see some length response, though typically the reponse seems to be somewhat less than the expected 3.3 micron / 200 V from the spec sheet.
• We are also still subject to low SNR, though at least now the DC response is visible to the eye.
  • We also recalibrated the PD using the stage in the current setup.
• We met this morning to talk about data collection, and we realized it would be best to try to improve the setup.
  • Koji provided some good suggestions, some of which reflected feedback collected from Gabriele, Dean, and Luis.
  • Our setup was sensitive enough to observe the response (yay) but not sensitive enough to make a good measurement.

The next log will reflect the updated setup.

I hope to come back to edit this log to fill out more detail, but the detail reflects intermediate steps with the old setup.

[Thejas, Camille, Stephen]

In Downs 227 on 05 May 2023

We took the following actions:

• Reconfigure our data acquisition with a SR785 instead of the oscilloscope.
  • The scope had been limited to ~10 mV precision, and the SR785 has better than mV precision.
• Contract the beam using some lenses borrowed from Gabriele.
  • Increases sensitivity, following some feedback from Koji which Gabriele had also mentioned
  • We measured the spot size on our flag to be .44 mm (had been about 1 mm).
• Moved all electronics, especially AC function generator, off of optical table.
  • Feedback from Koji.

We recalibrated the photodiode using the razorblade flag. We continued to be plagued by slow variations but we had much better data quality (less fuzziness and fewer spikes in the time series). It seemed like the razorblade was not stiff enough and was sensitive to airflow.

We may readjust and recalibrate to see if our data is better, but in the meantime, below are images of the calibration and setup. Data is at T2300050 Optical Component Testing Measurements, sheet "PiezoDCResponse".

Revisiting the measurement requirements and applying the sensitivity of the new setup:

• The NAC2124 PZT nominally extends 3.3 microns with a 200 V drive, +/- 15%.
  • Our 150 V drive should extend the PZT by 2.5 microns nominally.
  • Our shadow sensor would ideally be able to observe with accuracy better by order of magnitude (.25 microns).
• Our stage-driven, dial-indicator-observed PD calibration reveals a sensitivity of -6.704 V PD output per mm of displacement.
  • This corresponds with 149 microns of displacement per V PD output.
  • Across these 11 stage calibration measurements, the error terms were:
    • Standard Deviation: max. 0.00182 V, min. 0.00008 V, avg. 0.00069 V (no, I'm not going to report the standard deviation of the standard deviations.)
    • Range, V (max. value - min. value): max. 0.00563V, min. {C} 0. 00042 V, avg. 0. 00232 V
• If we want to measure with accuracy of .25 microns, that corresponds with a PD output of .0017 V
  • Looks like some of our measurements had low enough error for this accuracy, but there were some measurements which did not.
  • Hopefully we can improve by reducing the impact of vibration and airflow.

[Stephen, Camille, Thejas, with support from Luis]

Calibration reattempted with the PD borrowed from Koji, equivalent to the last PZT measurment (OMC_Lab/336). There were a couple of differences in contrast to the last measurement:

• We navigated to the central 1 mm of the range (the interval we found to be sensitive in the QPD calibration, dictated by the beam size) and we stepped through in .05 mm intervals.
• We had the oscilloscope on 10x Voltage probe mode. See setup in Attachment 1.

Data collected in table at T2300050 Optical Component Testing Measurements, sheet "PiezoDCResponse" (Day 2 section).

In the linear range from stage position [3.450, 3.550] the least squares linear fit is:

QPD_Sum = m * Stage_Position + b

• QPD_Sum is the dependent variable of QPD signal voltage, derived from the Channel 1 (sum) average, unit V.
• m = -136.45 V / mm is the response of the QPD to change in stage position.
• Stage_Position is the independent variable of stage height, observed via dial indicator readout, unit mm.
• b = 501.91 V is the best fit y-intercept - not a physical quantity.

So, does this setup allow us to measure the DC response of the PZT?

• Over the linear range, the "m" sensitivity parameter would correspond with a signal of .13645 V / micron
• We expect a stroke of 3 or 4 microns, yielding a signal of .40 V to .55 V.
  • (Noliac NAC2124 nominal free stroke is 3.3 microns +/- 15% for a maximum operating voltage of 200 V)
• The standard deviation was not consistent for each measurement; at this linear range, the standard deviation was between .10 V and .15 V.
  • This would be a large error bar in comparison to the signal level

So, is this DCPD setup better than the QPD?

• Comparing sensitivity against standard deviation, there is not much difference.
  • Standard deviation is the same for each measurement in the QPD case, while the PD has some variation (as the signal increases, the standard deviation also increases, but not with uniform scaling; at lower signal levels, the standard deviation is smaller for the PD than the QPD).
  • The ratio between Channel 1 Average and Standard Deviation is similar for the two setups, so neither setup reduces the error significantly.

We will probably just keep the PD in place, since there is not a great motivation to revert to the QPD, and the QPD could then be used for the OpLev independently. We will look at using the oscilloscope "Averaging" mode to reduce the noise in our measurement.

[Stephen, Camille, Thejas, with support from Marie, Dean, Luis]

We setup a shadow sensor! (Attachment 1)

• QPD (Thorlabs PDQ80A) and HeNe laser (< 4 mW @ 633 nm, Thorlabs HNLS008R, 12V / .7A) borrowed from Marie.
  • QPD supplied by 5V from DC power supply.
• Razor blade flag used to eliminate effect of pitch misalignment, atop a 62.5 gram mass.
• Lab jack used to provide height adjustment.
• Dial indicator (Mitutoyo Absolute +/- .001 mm, p/n S112TXB) mounted to height gauge, used to monitor stage height.

The calibration measurement proceeded as follows:

• Manually lowered the stage until the flag was not occluding any light on the QPD
• Raised the stage in 0.5 mm increments and recorded raw data (using the oscilloscope "Sampling" mode), until the flag occluded all of the light previously on the QPD.
• Identified the central 0.5 mm increment, and stepped through that range in .05 mm increments

Data collected in table at T2300050 Optical Component Testing Measurements, sheet "PiezoDCResponse"

In the linear range from stage position [3.450, 3.550] the least squares linear fit is:

QPD_Sum = m * Stage_Position + b

• QPD_Sum is the dependent variable of QPD signal voltage, derived from the Channel 1 (sum) average, unit V.
• m = -9.685 V / mm is the response of the QPD to change in stage position.
• Stage_Position is the independent variable of stage height, observed via dial indicator readout, unit mm.
• b = 35.6111 V is the best fit y-intercept - not a physical quantity.

So, does this setup allow us to measure the DC response of the PZT?

• Over the linear range, the "m" sensitivity parameter would correspond with a signal of .009685 V / micron
• We expect a stroke of 3 or 4 microns, yielding a signal of .03 to .04 V.
  • (Noliac NAC2124 nominal free stroke is 3.3 microns +/- 15% for a maximum operating voltage of 200 V)
• The typical standard deviation of each measurement is .009 to .011 V.
  • This would be a large error bar in comparison to the signal level.
• We will try again using a different photodiode.

Analysis of the PZT scan / TF data taken on May 31st and Jun 1st.

[DC scan]

Each PZT was shaken with 10Vpp 1Hz triangular voltage to the thorlabs amp.
The amp gain was x15. Abut 4 TEM00 peaks were seen on a sweep between 0 and 10V.

The input voltage where the peaks were seen was marked. Each peak was mapped on the
corresponding fringe among four. Then the each slope (up and down) was fitted by a iiner slope.
Of course, the PZTs show hystersis. Therefore the result is only an approximation.

PZT1: PZT #26, Mirror C6 (CM1)
PZT2: PZT #23, Mirror C5 (CM2)

PZT arrangement [ELOG Entry]

PZT1:
Ramp Up        13.21nm/V
Ramp Down   13.25nm/V
Ramp Up        13.23nm/V
Ramp Down   13.29nm/V

=> 13.24+/-0.02 nm/V

PZT2:
Ramp Up        13.27nm/V
Ramp Down   12.94nm/V
Ramp Up        12.67nm/V
Ramp Down   12.82nm/V

=> 12.9+/-0.1 nm/V

[AC scan]

The OMC cavity was locked with the fast laser actuation. Each PZT was shaken with a FFT analyzer for transfer function measurments.
(No bias voltage was given)

The displacement data was readout from the laser fast feedback. Since the UGF of the control was above 30kHz, the data was
valid at least up to 30kHz. The over all calibration of the each curve was adjusted so that it agrees with the DC response of the PZTs (as shown above).

The response is pretty similar for these two PZTs. The first series resonance is seen at 10kHz. It is fairly high Q (~30).

Aim: To find the combinations of mounting prism+PZT+curved mirror to build two PZT sub-assemblies that best minimises the total vertical beam deviation.

(In short, attachment 1 shows the two chosen sets of components and the configuration according which they must be bonded to minimize the total vertical angular deviation.)

The specfic components and configuration were chosen as follows, closely following Section 2.3.3 of T1500060:

Available components:

Mounting prisms: 1,2,12,14,15 (Even though there is mention of M17 in the attachments, it can not be used because it was chipped earlier.)

PZTs: 12,13

Curved mirrors: 10,13

Method:

For a given choice of prism, PZT and mirror, the PZT can be placed either at 0deg or 180deg, and the mirror can rotated. This allows us to choose an optimal mirror rotation and PZT orientation which minimises the vertical deviation.

Total vertical angle 

 was measured by Koji as described in elog 369.

,              are the wedge angle and orientation respectively and were measured earlier and shown in elog 373 . 

,               The measurement of the location of the curvature bottom (d, ) of the mirrors is shown in elog 372 . The optimal  is to be found.

These steps were followed:

1. For every combination of prism, PZT, and mirror, the total vertical deviation was minimized with respect to the angle of rotation of the curved mirror computationally (SciPy.optimize.minimize). The results of this computation can be found in Attachment 2: where Tables 1.1 and 2.1 show the minimum achievable deviations for mirrors C10 and C13 respectively, and Tables 1.2 and 2.2 show the corresponding angle of rotation of the mirrors  .
2. From the combinations that show low total deviations (highlighted in red in Attachment 2), the tolerances for 5 arcsec and 10 arcsec deviations with mirror rotation were calculated, and is shown in Tables 1.3, 1.4, 2.3, 2.4 of Attachment 2.
3. While calculating the tolerances, the dependence of the vertical deviations with rotation were also plotted (refer Attachment 3).
4. Two sets from available components with low total deviation and high tolerance were chosen. 

Result:

These are the ones that were chosen:

1. M14 + PZT13 at 0deg + C13 rotated by 169deg anticlockwise (tot vertical dev ~ -3 arcsec)
2. M12 + PZT12 at 0deg + C10 rotated by 88deg clockwise (tot vertical dev ~0 arcsec)

The method of attaching them is depicted in Attachment 1.

Test result of the PZTs by Valera and Ryan

PZT  Length Angle
 #   [nm/V] [urad/um]
 11  14.5   17.6
 12  13.8   17.8
 13  11.2   25.0
 14  14.5    6.6
 15  12.5   10.6

 21  14.5    9.7
 22  13.8   28.8
 23  14.5    6.8  ==> Assembly #2
 24  18.5   51.7  ==> Used for prototyping
 25  17.1   13.8
 26  14.5    6.6  ==> Assembly #1

[Jeff, Zach, Koji]

PZT assembly gluing

Glue gun -> to be returned to MIT
Fixtures x2
Al bases, spacers
spare screws
mirrors / prisms / PZTs
IPA bottle
clean tools x2
first contact kit
gloves (7.5)

Prototype PZT assembly

Motivation:

Before we glue the PZT assembly, we need to build a prototype. This is to confirm the heat cure process
does not cause any cracking of the PZT or glass components. The CTE of the PZT is 2~3ppm
(depends on the direction) while the one for Fused Silica is 0.55ppm.

Materials:

- A fused silica substrate, 1/2" in dia. Supplied from Garilynn. I defined the chamfered side as the front side.

- PZT: Noliac NAC2124, serial #24, this is a spare PZT as this has the worst length to angle coupling.

- Mounting Prism: D1102069 SN22. This has the worst perpendicularity among the prisms.

- Fixtures:

D1300185 aLIGO OMC CURVED MIRROR BONDING FIXTURE ASSY
D1300186 aLIGO OMC CURVED MIRROR BONDING FIXTURE FRONT
D1300187 aLIGO OMC CURVED MIRROR BONDING FIXTURE BACK
D1300188 aLIGO OMC CURVED MIRROR BONDING FIXTURE RING

Procedure:

- Wipe all of the components with the isopropanol.

- Attach the back piece of the fixture on the Al wrapped bracket.
(The current 4-40 screws for the middle piece are too long and stick out from the back side of the back piece.
Therefore a 1/16" shim for a 1/2" rod is inserted between the bracket and the back piece)

- Brought a glue package to the lab (10:40PM)

- Loosely attach the middle piece to the back piece with four 4-40 screws.

- Insert the mounting prism in the fixture. Insert the PZT in the fixture too.

- Insert a dummy substrate in the fixture.

- Attach the front piece with spring loaded screws.

- Align the PZT and the optic in the fixture. (Basically apply downward force to them)

- Test the rigidity of the assembly (11:30PM)

- Remove the PZT and the mirror. Apply UV epoxy.
(A single dub was applied for each PZT surface of the PZT but this was too much.)

- Make sure the PZT and the optic are aligned by applying the downward force.

- Illuminate UV light from the front.

- Illuminate UV light from the back. (11:50PM)

Procedural issues:

- Long 4-40 screws (described above)
(Circumvented)

- As the PZT is not constrained with the middle piece, it tends to move vertically and rotationally
because of the wire tension. (This is not a mistake but the design so that the PZT is constrained by the optic.)
Therefore after applying glue on the PZT, the motion of the PZT spreads the glue on the back surface of
the curved mirror.
(Solution to be tried) Our solution is to glue the PZT and the mounting prism first with a dummy optics (made of SF2).
The wires should be tacked somewhere on the mount 

- The amount of glue on the PZT was too much. I gave one dub of glue for each side.
As a result, excess glue leaks out along the ring.

- The front plate has a chamfered hole but this tends to slip and move the mirror vertically.
Later I used the flat side of the plate to hole the mirror.
(Circumvented) It seems that this hold the mirror in a better way as the plate can't rock

- Spring load for the front plate was too strong. This was because the natural length of the spring was too long.
(Circumvented) The spring was cut at the length of the 4-40 screw. Then attaching the screws became completely fine.

Result:

Slide show:

Each PZT was swept with 0-150V 11Hz triangular wave.
Time series data for 0.2sec was recorded for each PZT.

The swept voltage at the resonances were extracted and the fringe number was counted.
Some hysteresis is seen as usual.

The upward/downward slopes are fitted by a linear line.

The average displacement is 11.3nm/V for PZT1 and 12.7nm/V.

The PZT response was measured with a FFT analyzer. The DC calibration was adjusted by the above numbers.

A simple COMSOL simulation was run to see how the PZT deforms as the voltage applied.

Use the geometry of the ring PZT which is used in the OMCs -  NAC2124 (OD 15mm, ID 9mm, H 2mm)
The material is PZT-5H (https://bostonpiezooptics.com/ceramic-materials-pzt) which is predefined in COMSOL and somewhat similar to the one used in NAC2124 (NCE51F - http://www.noliac.com/products/materials/nce51f/)
The bottom surface of the ring was electrically grounded (0V), and mechanically fixed.
Applied 100V between the top and bottom.

[Koji, Jeff]

Background

In response to the failure of one of the PZTs on L1OMC (LLO:8366), we have been taking place an endurance test of
the four PZT sub-assemblies in prior to their being glued on the glass breadboard.

According to the technical note by Noliac, the common mode of PZT failure is degradation of the impedance
due to cyclic actuation (like 10^7 times) with over voltage. Therefore our procedure of the test to actuate the PZTs
at least 10^7 times with half voltage of the nominal operating voltage (i.e. nominal 200V) and check the degradation
of the impedance.

Driving signal

For the driving of the PZT, a thorlabs HV amp is used. A source signal of 3.5Vpp with an offset of 1.7V is produced
by DS345 function generator. This signal turns to a sinusoidal signal between 0 and 100V in conjunction with the gain
of 15 at the HV amp.

The maximum driving frequency is determined by the current supply limit of the HV amp (60mA). The capacitance
of each PZT is 0.47uF. If we decide to cycle the signal for 4 PZTs in parallel, the maximum frequency achievable
without inducing voltage drop is 100Hz. This yields the test period of 28hours in order to achive 10^7 cycles.

Initial impedance diagnosis

To check the initial state of the PZTs, a DC voltage of 100V was applied via 1kOhm output resistance.
(Note that this output resistance is used only for the impedance test.)
For each PZTs, both side of the resister showed 99.1V for all measurement by a digital multimeter.
Assuming the minimum resolution (0.1V) of the multimeter, the resistance of each PZT was more than 1MOhm before
the cycling test.

Failure detection

In order to detect any impedance drop of the PZTs, the driving signal is monitored on the oscilloscope via a 1:10 probe.
If there is any significant impedance drop, the driver can't provide the driving current correctly. This can be found
by the deviation of the driving voltage from the reference trace on the oscilloscope (below).

Temperature rise

Because of the loss angle of the PZT capacitance, heating of the PZTs is expected. In order to check the temperature rise,
an IR Viewer (FLIR) was used. We did not take care of careful calibration for the PZT emissibity as what we want was a
rough estimation of the temperature.

Before the driving (LEFT) and at the equilibrium (RIGHT)

The temperature change of the PZT was tracked for an hour (below). Fitting of the points indicated that the temperature rise is 2.3degC and the
time constant of 446 sec. This level of temperature rise is totally OK. (Note that the fitting function was T = 27.55 - 2.31 Exp[-t/446.])

Results

DAY1:

Start driving
20:27 25.2 degC, status OK
20:33 26.7 degC, status OK
20:41 26.9 degC, status OK
20:48 27.6 degC, status OK
20:54 27.4 degC, status OK
21:10 27.4 degC, status OK
21:37 status OK
Stop driving

70 minutes of driving (i.e. 4.2x10^5 cycles) => no sign of degradation

DAY2:

Start driving
14:15, 24.5 degC, status OK
14:17, 26.0 degC, status OK
14:24, 27.0 degC, status OK
14:40, 26.8 degC, status OK
14:50, 26.8 degC, status OK
15:30, 26.8 degC, status OK
15:55 status OK
17:40 status OK
21:00 status OK (2.43Mcycles + 0.42Mcycles = 2.85Mcycles)
1d+12:00 status OK (7.83Mcycles + 0.42Mcycles = 8.25Mcycles)
1d+15:00 status OK (8.91Mcycles + 0.42Mcycles = 9.33Mcycles)
1d+18:40 status OK (10.23Mcycles + 0.42Mcycles = 10.65Mcycles)
Stop Driving

After 10.65Mcycles no sign of degradationwas found.

The PZT tests were finished with the conclusion that the PZT won't be damaged with our expected usage.

This is another test of the PZTs to make sure small (~10V) reverse voltage does not break the PZTs.

Background

At the site, we decided to use one of the PZT, which is still alive, for the HV and LV actuation.
The HV actuation is limited to 0 to 100V while the LV actuation is 10Vdc with 1Vpp fast dithering.
This means that a reverse voltage upto 10.5V will be applied to the PZT at the worst case.

From the technical note this level of reverse voltage does not induce polarization of the PZT.
The test is to ensure the PZT is not damaged or degraded by this small reverse voltage.

Method

HV drive: Thorlabs HV amp (G=15) driven with DS345 function generator (3.5Vpp+1.7Vdc, 0.1Hz)
=> 0-100V @0.1Hz
=> The hot side of the potential is connected to the positive side of the PZT

LV drive: Phillips function generator (1Vpp+9.5Vdc@1kHz)
The driving frequency is limited by the current output of the function generator.
=> The hot side of the potential is connected to the negative side of the PZT

These drives shares the common ground.

Tests

Testing with spare PZTs 

Started @19:23 (Aug 23)
Stopped @20:15+2d (Aug 25, duration 48h52m)
17600cycles for the 0.1Hz drive.
176Mcycles for the 1kHz drive.

Checked the impedances of PZT1 and PZT2.

Apply 100Vdc via a 1kOhm resister, 0V detected across the 1kOhm resister
This is equivalent to the resistance of 1MOhm.

Testing with the PZT subassemblies

Started shaking of the four PZT assemblies @20:20 (Aug 25)
No impedance change observed @11:10+1d
No impedance change observed @15:30+1d
Stopped shaking of the four PZT assemblies @XXXX (Aug 26)

Wiring for the test

As OMC SN002 already has the PZTs connected to the Mighty-Mouse connector, a test cable with a female mighty-mouse connector was made.

A small imperfection: When the cable was inserted to the connector shell, I forgot to mirror the pin out. Therefore the color and pin number do not match.