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ID Datedown Author Type Category Subject
  361   Wed May 15 19:07:53 2019 KojiCleanGeneralWhat is this???

Suddenly something dirty emerged in the lab. What is this? It looks like an insulation foam or similar, but is quite degraded and emits a lot of particulates.

This does not belong to the lab. I don't see piping above this area which shows broken insulation or anything. All the pipes in the room are painted white.

The only possibility is that it comes from the hole between the next lab (CRIME Lab). I found that the A.C. today is much stronger and colder than last week. And there is a positive pressure from CRIME Lab. Maybe the foam was pushed out from the hole due to the differential pressure (or any RF cable action).

 

Attachment 1: P_20190515_185602.jpg
P_20190515_185602.jpg
Attachment 2: P_20190515_185844.jpg
P_20190515_185844.jpg
  360   Thu May 9 18:10:24 2019 KojiOpticsCharacterizationOMC(004): Spot position scan / power budget

(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.

Attachment 1: 190508.png
190508.png
Attachment 2: scattering_spots_CM1.png
scattering_spots_CM1.png
  359   Thu May 9 17:35:07 2019 KojiOpticsGeneralAlignment strategy

Notes on the OMC cavity alignment strategy

- x3=1.17 γ + 1.40 δ, x4=1.40 γ + 1.17 δ
- This means that the effect of the two curved mirrors (i.e. gouy phases) are very similar. To move x3 and x4 in common is easy, but to do differentially is not simple.
- 1div of a micrometer is 10um. This corresponds to the angular motion of 0.5mrad (10e-6/20e-3 = 5e-4). ~0.5mm spot motion.
- ~10um displacement of the mirror longitudinal position has infinitesimal effect on the FSR. Just use either micrometer (-x side).
- 1div of micrometer motion is just barely small enough to keep the cavity flashing. => Easier alignment recovery. Larger step causes longer time for the alignment recovery due to the loss of the flashes.

- After micrometer action, the first move should be done by the bottom mirror of the periscope. And this is the correct direction for beam walking.

- If x3 should be moved more than x4, use CM2, and vise versa.
- If you want to move x3 to +x and keep x4 at a certain place, 1) Move CM2 in (+). This moves x3 and x4 but x3>x4. 2) Compensate x4 by turning CM1 in (-). This returnes x4 to the original position (approximately), but leave x3 still moved. Remember the increment is <1div of a micrometer and everytime the cavity alignment is lost, recover it before loosing the flashes.

Attachment 1: T1500060_OMC_Optical_Testing_Procedure.pdf
T1500060_OMC_Optical_Testing_Procedure.pdf
  358   Thu May 9 16:07:18 2019 StephenMechanicsGeneralImprovements to OMC Bonding Fixture

[Stephen, Koji]

As mentioned in eLOG 331, either increased thermal cycling or apparent improvements in cured EP30-2 strength led to fracture of curved mirrors at unintended locations of bonding to the PEEK fixture parts.

The issue and intended resolution is summarized in the attached images (2 different visualizations of the same item).

Redline has been posted to D1600336-v3.

Drawing update will be processed shortly, and parts will be modified to D1600336-v4.

 

Attachment 1: image_of_issue_with_OMC_PZT_bonding_fixture_from_D16003336-v3.png
image_of_issue_with_OMC_PZT_bonding_fixture_from_D16003336-v3.png
Attachment 2: image_02_of_issue_with_OMC_PZT_bonding_fixture_from_D16003336-v3.PNG
image_02_of_issue_with_OMC_PZT_bonding_fixture_from_D16003336-v3.PNG
  357   Fri May 3 11:06:28 2019 KojiOpticsCharacterizationOMC(004): Spot positions and the scattering

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.

2019/5/1 CM1 right micrometer 1div backward
         
    Unit   V_RefPD [V]
P_TRANS 13.53 [mW]   3.09
V_REFL_LOCKED 53.4 [mV]   3.09
V_REFL_UNLOCK 2.52 [V]   3.065
P_IN 14.45 [mW]   3.07
V_REFL_OFFSET -6.35 [mV]    
         
Coupling 0.977      
OMC_Trans 0.953      

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)

2019/5/1 CM1 right micrometer 0.5div backward
         
    Unit   V_RefPD [V]
P_TRANS 14.55 [mW]   3.28
V_REFL_LOCKED 49 [mV]   3.28
V_REFL_UNLOCK 2.755 [V]   3.299
P_IN 15.64 [mW]   3.3
V_REFL_OFFSET -6.316 [mV]    
         
Coupling 0.980      
OMC_Trans 0.955      

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.

Attachment 1: misalignment.pdf
misalignment.pdf misalignment.pdf misalignment.pdf
  356   Wed May 1 15:40:46 2019 KojiOpticsCharacterizationOMC(004): Spot positions and the scattering

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.

 

Attachment 1: misalignment.pdf
misalignment.pdf misalignment.pdf
  355   Thu Apr 25 15:05:19 2019 JoeOpticsCharacterizationLooking at PZT HOM spacing dependance and thinking about workflow

[koji, joe]

The template or glass breadboard was wobbling, and we noticed that the caivty alignment became worse/better when it was pressed down. We saw that it was the glass breadboard, so it was fixed into the transport fixture more securely. Now its alignement didn't change when it was pressed down. We took a pzt mirror out and replaced it, the alignment din't change much so that was good. We set up posts to hold the pzt wires.

We noticed that the bottom of the mirrors were dirty, so we cleaned them, and once we were happy with the newton rings, we aligned the cavity

Took a photo of CM2, the spot is maybe 1 beam diameter vertically and horizontally from the centre, and quite a bright spot could be seen. The same problem with CM1. We thought it would be good to see a measurement of higher order mode spacing dependence on PZT DC voltage rather than doing the full characterisation since the alignment seems to change quite a lot when ever we do anything, and this cavity arrangement probably isn't very good anyway (can see scattering on both curved mirrors with the IR camera). 

did measurements of FSR, = 2.64835MHz

did HOM spacing for 0,75,150V on CM1 in pitch and yaw.

we want to come up with a work flow for how to do these measurements, and make automate parts of the analysis?

 

  354   Wed Apr 24 13:58:51 2019 JoeOpticsCharacterizationOMC power budget and UV Epoxy Bonding of BS1

[koji,philip,joe,liyuan,stephen]

need to add spot positions.

Mirrors: PZT11,PZT22, A14, A5

Measurement postion Power P_normalise
P_in 15.66+-0.01mV 3.251+-0.001
V_ref,lock 64+-2mV 3.22+-0.001
V_ref,unlock 2.808+-0.001 V 3.253+-0.001
P_qpd 99.5+-0.5 uW 3.24+-0.002
P_cm1 79.0+-0.5 uW 3.22+-0.002
P_cm2 76.2+-0.03 uW 3.22+-0.01
P_trans 14.55+-0.05 mW 3.22+-0.01
Vref,dark -6.286 mV +-0.01mV  

Mode matching = 97.72%

15.66-> 15.30mW coupled.

~100uW for QPD

->15.2mW in cavity

Trans = 14.55mW -> 95.7% transmission

The flat mirrors were the ones with the most scattering, so we thought about how to improve it. We tried to move the first flat mirror by pushing it with our finger so that he beam would move along the optic. We tried this a couple of times, however the second time we moved it we lost our alignment and could not retrieve it. We looked at the mirror and we could see quite a lot of newtonian rings. We could see a small fibre on the glass bread board. We cleaned the optics base and the gbb, and we could get the alignment back. The beam was aligned to the cavity, the spots no longer hit the centre of the CM2. 

We measured the power budget again.

Measurement position Power P_normalise
V_ref,lock 47mV 3.24V
P_trans 14.45+-0.005mW 3.24 +-0.003 V
V_ref,unlock 2.68+-0.001 V 3.25+-.003
     

mode matching = 1-47/2680 = 0.9824, 98.2% mode matching

same p_normalise so

15.66-> 15.34mW coupled.

~15.24mW in cavity

transmission = 14.45, so 94.8% transmission.

Koji noticed that FM1 wasn't touching the template correctly, so he re-aligned the cavity.

Afternoon session - UV Bonding (E1300201-v1 procedure 6.4.4 "Gluing" using procedure in section 7.2 "UV Gluing")

Wiped down UV PPE, UV Illuminator, and UV Power Meter

Applied Optocast 3553-LV Epoxy to sample fused silica optics, to test quantity of glue needed and to become familiar with the process and tools. Philip and Joe each created a successful bond. Joe's had 3 visible spots in the bulk of the bond. Acetone was used to scrub some residue of epoxy from the surface near the OD, which was likely cured. Short duration exposure (seconds) to acetone at the perimeter of the bond did not yield any weakening of bond.

While test pieces were bonded, Koji was making some adjustments to the cavity alignment in preparation for gluing of the steering mirror BS1.

Koji noticed that the spring clamp was causing pitch in the BS1 mirror, so he recommended that we utilize the "restrain by allen key" technique to load the mirror during curing.

Once aligned, we tried taking the BS1 mirror out of the template and then putting it back. We did this twice and both times the cavity needed realigning (with the curved mirrors as well as the input steering periscope). Why is this? Since the mirror was touching the template it should not have become misaligned right? Maybe the template moves slightly? I think before glueing in the cavity mirrors we should find out why probably? Koji took a look and claimed that a few optics may have been unconstrained. 

Planning between Koji and Joe led to placement of 5 drops of epoxy on the BS1 surface, to match the bonding area. At this point we noticed that the template was not secured very well, by poking down on it we could see it move. This might explain why we are becoming misaligned very easily. Once the prism was back on the board, Koji used allen keys to move around the prism. This was done until we could align it again (i.t looked too pitched). The beam was aligned back into the cavity, and the UV light was used to cure the bond. The reflected DC when locked was

  • pre-cured = 47mV
  • cured = 55 mV

so it looks ok still.

 

 

 

  353   Tue Apr 23 10:21:12 2019 JoeOpticsConfigurationMoving the spots to the centre of the curved mirrors

[Koji,Philip, Liyuan, Joe]

CM1:

We moved the curved mirrors to these positions:

inner = 0.807mm

outer = 0.983 mm

CM2:

inner = 0.92 mm

outer = 0.85 mm

To do this so that realignment was easier, we moved the screws in steps of 5um. We alternated which mirror we adjusted so that we could monitor with a wincam how well aligned the beam into the cavity was. We only moved the cavity mirrors a small amount so we could still see higher order mode flashes transmitted through the cavity (e.g.TM03 modes). We would then improve the input alignment, and then move the cavity mirrors some more. Once the mirrors were adjusted according to http://nodus.ligo.caltech.edu:8080/OMC_Lab/190422_195450/misalignment4.pdf the spot positions looked near the middle of the curved mirrors (using a beam card). We began beam walking but we ran  out of range of the bottom periscope screws in the yaw dof. We tried using the third screw to move the mirrror in both yaw and pitch, hopefully this will let move the mirror such that we can use the just the yaw screw. This screw also ran out of range, so we decided that the cavity needed a small adjustment.

The curved mirrors were moved slightly (>5um) and then we tried to get alignment. By using the fibre coupler translation stage, we move the beam side ways slightly, and then tried to get the periscope mirrors back to a position where the screws could move the mirrors. Once we had an ok alignment, we checked the beam. It looked like it was pretty close to the centre of the curved mirrors, which is where we wanted it to be.

We then tried locking the cavity, although the error signal was quite small. The adjusted the input offset and gain of the servo (there is apparently some problem to do with the input and output offsets). Once the cavity was locked we could make the final adjustments to aligning. We still ran out of range on the periscope. We decided to move the breadboard with the fibre coupler and mode matching lenses on it. Because we knew that the cavity was aligned such that the beam hits the centres of the curved mirrors, we could regain flashes quite quickly. We saw the error signal go down, but eventually this decrease was just to do with the beam clipping on the periscope mirrors. We moved the spot back to where we ok aligned, and slid the periscope so we were not clipping the mirror. This worked very well, and then optimised the alignment.

We then tried to improve the mode matching. 

We took photos of the spot positions (quite near the center) and made the detuned locking measurement. The fitting of the data (attachment 1) wsa 1.1318m (what error should we put here?).

I think the order we did things in was:

  • turning anti clockwise on the fibre coupler and misalign the diode, we measured the modespacing.
  • returned the alignment for the photodiode, and realign fibre couple.
  • miss align the photodiode horizontally, and then used fibre coupler to maximise the peak higher order mode peak height. We then used the PD again to make the peak height bigger.
  •  
Attachment 1: FSR_detuned_locking.pdf
FSR_detuned_locking.pdf
Attachment 2: CM1_IMG_7702.JPG
CM1_IMG_7702.JPG
Attachment 3: CM2_IMG_7704.JPG
CM2_IMG_7704.JPG
  352   Mon Apr 22 19:54:28 2019 KojiGeneral OMC(004): Spot positions at the end of Apr 22nd
Attachment 1: misalignment4.pdf
misalignment4.pdf
  351   Mon Apr 22 09:54:21 2019 JoeGeneral Shortening cavity (A5,A14,PZT11,PZT22) to get closer to design FSR

[Koji,Joe,Philip,stephen]

in units 20um per div on the micrometer [n.b. we reailised that its 10um per div on the micrometer]

CM1 inner screw pos: 11.5

cm1 outer screw pos: 33.5

cm2 inner screw pos: 11

cm2 outer screw pos: 13

the cavity is currently 3mm too long, move each mirror closer by 0.75mm

CM1 inner screw pos: 11.5+37.5 = 49

cm1 outer screw pos: 33.5+37.5= 71

cm2 inner screw pos: 11+37.5 = 48.5

cm2 outer screw pos: 13+37.5 = 50.5

The screws on the micrometers were adjusted to these values.

cleaned cm1 (PZT 11). There was a mark near the edge which we were not able to remove with acetone. On the breadboard there were 3 spots which we could not remove with acetone. Once we wiped the mirror and breadboard we put the mirror back. 

FM2 (A5). The prism looked quite bad when inspected under the green torch, with lots of lines going breadthways. We thought about replacing this with A1, however this has had the most exposure to the environment according to koji. This has a bit of negative pitch, so would bring down the beam slightly. We decided to continue to use A5 as it had worked fairly well before. The breadboard was cleaned, we could see a few spots on it, they were cleaned using acetone.

FM1 (A14). Near the edge of the bottom surface of the prism we could see some shiny marks, which may have been first contact. We attempted to scrape them off we tweezers. The breadboard looked like it had a few marks on it. These were hard to remove with the acetone, it kept leaving residue marks. We used isopropanol to clean this now, which worked much better. The sharp edges of the breadboard can cause the lens tissue to tear a bit, so it took a few rounds of cleaning before it looked good to put a prism on. The mirror was put back onto the breadboard. 

The cavity was aligned, then we realised that 1 turn is 500um, so its still too long (1.75mm long). The FSR was 264.433Mhz, which is 

CM2 still showed quite a bit more scattering than CM1, so we want to move this beam.

CM1:

  • inner = 0.405mm
  • outer = 0.67mm

CM2

  • inner = 0.507mm
  • outer = 0.42mm

want to increase by 1.7/4 = 0.425, so

CM1:

  • inner = 0.405+ 0.425 mm = 0.83 mm
  • outer = 0.67+ 0.425mm = 1.095 mm

CM2

  • inner = 0.507 + 0.425mm = 0.932 mm
  • outer = 0.42 + 0.425mm = 0.845 mm

we tried to align the cavity, however the periscope screws ran out of range, so we changed the mircometers on CM2. We tried this for quite some time, but had problems with the beam reflected from the cavity clipping the steering mirror on the breadboard (to close to the outer edge of the mirror). This was fixed by changing the angle of the two curved mirrors. (We should include a diagram to explain this).

The cavity was locke, the FSR was measured using the detuned locking method, and we found that the FSR = 264.805 MHz, which corresponds to a cavity length of 1.1321m

we took some photos, the spot is quite far to the edge of the mirrors (3 to 4mm), but its near the centre vertically. photos are 

123-7699 = CM2

123-7697 = CM1

 

 

Attachment 1: CM1_IMG_7699.jpg
CM1_IMG_7699.jpg
Attachment 2: CM2_IMG_7697.jpg
CM2_IMG_7697.jpg
  350   Sat Apr 20 00:50:12 2019 KojiOpticsCharacterizationOMC(004): Spot positions

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)

Attachment 1: misalignment2.pdf
misalignment2.pdf
Attachment 2: misalignment3.pdf
misalignment3.pdf
  349   Fri Apr 19 11:34:19 2019 KojiOptics OMC initial alignment and locking

The spot on CM1 was found displaced by 3.4mm (horiz.) and 3.0mm (vert.) in the upper right direction looking from the face side.
The spot on CM2 was found displaced by 1.2mm (horiz.) and 1.8mm (vert.) in the upper left direction looking from the face side.

The drawing on the left side of the attachment shows the estimated misalignment when we think they all come from the curved mirrors.
As for the yaw misalignment, CM1 and CM2 were 3.9mrad and 5.6mrad rotated (misaligned) in CW, respectively.
As for the pitch misalignment, CM1 and CM2 has 1.7mrad (narrowing) and 3.5mrad (widening), respectively. We have no adjustment for this.
Let's say if this comes from the dusts on the bottom of the prisms, CM1 has ~17um one, and CM2 has ~35um one beneath them. The question is if we can believe this or not? This should be checked with the Newton fringes we can see at the bottom of the prisms.

Attachment 1: misalignment1.pdf
misalignment1.pdf
  348   Fri Apr 19 09:35:28 2019 JoeGeneral Adjusting cavity axis, re-alignment of OMC and locking

[koji,philip, joe, liyuan, steven]

*still need to add photos to post*

PZT 11 was removed and inspected for so dust/dirt on the bottom of the prism. We saw a spot. We tried to remove this with acetone, but it stayed there. (Attachment 2, see the little white spec near the edge of the bottom surface of the prism)

current micrometer positions:

  • CM1: one closest to centre 11, close to edge 35 marking
  • CM2: both at 20 marking

Swapped PZT for PZT 22, cleaned the bottom and put it into position of CM1. We saw a low number of newton rings, so this is good.

We got a rough initial alignment by walking the beam with the periscope and PZT 22  mirrors. Once we saw a faint amount of transmission, we set up the wincam at the output. The reflected light from the cavity could also be seen to be flashing as the laser frequency was being modulated. 

Once it was roughly aligned, using the persicope we walked the beam until we got good 00 flashes. We checked the positions of the spots on the mirror with the beam card. This looked a lot better in the verticle direction (very near the centre) on both curved mirrors. We locked the cavity and contiued to align it better. This was done with the periscope until the DC error signal was about 0.6V. We switched to the fibre coupler after this. 

Once we were satisfied that he cavity was near where it would be really well aligned, we took some images of the spot positions. Using these we can work out which way to move the curved mirrors. Koji worked this out and drew some diagrams, we should attach them to this post. [Diagram: See Attachment 1 of ELOG OMC 350]

We made the corrections to the cavity mirrors

  • CM1: one closest to centre 11, close to edge 35+16 marking
  • CM2: I can't remember exactly, Koji created a diagram which would help explain this step [Diagram: See Attachment 2 of ELOG OMC 350]

The scatter from CM1 looked very small, it was hard to see with a viewer or CCD. We had to turn up the laser power by a factor of 3 to begin to see it, indicating that this is a good mirror.

Once this was done, the spot positions looked uch nearer the centre of each mirror. They look pitched 1mm too high, which might be because of the bottom surfaces of the prisms having a piece of dust on them? For now though it was good enough to try take the detuned locking FSR measurement and RFAM measurement. 

To see the higher order mode spacing, we misaligned them incoming beam in pitch and yaw so that the TM10 and TM01 modes were excited. The cavity transmission beam was aligned onto the photodiode such that we could make a transfer function measurement (i.e. shift the beam along the photodiode so that only half of the beam was on it, this maximises the amount of photocurrent).

attachment 1 shows the fitting of the detuned locking method for measuring FSR and cavity length/

I saved this data on my laptop. When I next edit this post (hopefully I will before monday, although I might be too tired from being a tourist in california...) I want to upload plots of the higher order mode spacing.

 

 

Attachment 1: FSR_Scan_Fitfsrdata.pdf
FSR_Scan_Fitfsrdata.pdf
Attachment 2: IMG_7679_cropped.jpg
IMG_7679_cropped.jpg
  347   Fri Apr 19 09:21:07 2019 PhilipOptics Cleaning of OMC optics

ach[Joe, Phillip, Koji, Stephen]

Work from 17.04.2019

First contact cleaning of OMC optics
We cleaned the OMC optic with first contact. After a first cleaning run all mirrors except for two looked
fine. One had some first contact residuals on the left at center height and another had some particle sitting
near the center area. As the ionized nitrogen gun didn't help we applied another round of first contact which resolved
the two issues. Unfortutanely the second run of cleaning again left some residuals of first contact at the edges.
We were able to peal these off with tweezers.

Placement of Optics at the breadboard
We cleaned the contact surfaces for the bonds using optic wipes and pure isopropanol. The placement wen't well for 3 of the 5 optics (low number of newtonian rings).
One was recleaned and placed on the breadboard again which seemed fine. For the 5th no newtonian rings could be seen (either verry ood or bad) we planed on trying it in the current set-up. Mirrors used can be seen in attachment 3.

 

Attachment 1: IMG_7877.JPG
IMG_7877.JPG
Attachment 2: IMG_7883.JPG
IMG_7883.JPG
Attachment 3: IMG_7884.JPG
IMG_7884.JPG
  346   Thu Apr 18 20:47:54 2019 JoeOptics OMC initial alignment and locking

[Joe, Phillip, Koji, Stephen]

*draft post, please add anymore info if I missed something*

  • made initial alignment of the cavity. To do this we used the periscope mirrors to aim the incoming beam at the centre of the first mirror and second (1st curved mirror) mirror. Using the micrometers (initial positions was 0.20mm), we moved the first curved mirror so that it hit the third mirror. We then used a combination of the periscope and first curved mirror movements to start seeing 2 or 3 round trips. micrometer was set to roughly 0.11mm. We then only used  periscope mirrors to align the beam into the cavity.
  • We set up a wincam at the transmission of the cavity. This was a useful was of seeing what mode was being transmitted through the cavity. We walked the beam with the periscope mirrors until we saw flashes of the TM00 mode.
  • Once the cavity was transmitting TM00 modes, we started to lock it. Once it was locked we looked at the the spot positions of beam on the mirrors. Phillip looked with an IR viewer and could see that the spots were too high on both the curved mirrors
  • We set up a CCD to capture an image of this. Two post holders have been left in place for easy movement of the CCD.

General notes about working with this set up. The lens on the CCD can come off quite easily, as you just change how much its screwed on to change the focus. Care should be taken that you don't know the template with this as well, as the camera is quite close to the template (and near the edge of the bench!). Also be mindful of the PZT wires, as they can pull the mirrors out of position.

Attachment 1 shows the position of the spots on the mirrors A14 and PZT11. The spots are about 3mm ish from the centre of the curved mirror in the vertical and horizontal direction. 

Attachment 2 sketch of mirror positions.

Attachment 3 shows the postion of the spot on PZT13. The spot is less near the edge than on PZT11, but its still 2mm ish from the centre of the curved mirror in both directions.

To move the beam horizontally we can use the alignment matrix in appendix C of T1500060. However since we don't have control over the pitch of the mirrors, moving the spots down could require us to inspect the glass breadboard/prisms for dust. We suspect that PZT could be the culprit, as we could not see newtonian rings between its base and the glass breadboard. One way to test this idea is just to clean the bottom of the PZT with acetone, and see if that improves the spot position. If we don't have to do any work to realign it, then this was not the issue.

Koji pointed out that the spot in attachment 1 is very near the edge of the optic, so shifting the beam horizontally could also fix the vertical issue. 

Attachment 1: IMG_7676.JPG
IMG_7676.JPG
Attachment 2: IMG_7666.JPG
IMG_7666.JPG
Attachment 3: IMG_7670.JPG
IMG_7670.JPG
Attachment 4: IMG_7883.JPG
IMG_7883.JPG
Attachment 5: IMG_7882.JPG
IMG_7882.JPG
  345   Wed Apr 17 10:30:37 2019 PhilipOpticsGeneralOMC optical set-up day 1

[Joe, Koji, Liyuan, Philip, Stephen]
Work done on 16.04.2019

Finishing assembly of transport box
Assembly worked fine except for the clamping structure to clamp the lid of the transport box to the bottom part.
It seemed that some of the plastic of these clamps became brittle during the baking. The plastic was removed and the
clamps where wiped clean. It appears that the clamps can't be locked as they should. Still the transport box should be fine
as the long screws will mainly clamp the two parts together.

Preparing the transport box to mount the breadboard
The lid of the the transport box was placed upside down and clamped to the table. All peak clamping structures where pulled back as far as possible.

Preparation and cleaning of the breadboard
We unpacked the breadboard and found lots of dust particles on it (most likely from the soft paper cover which was used). We used the ionized nitrogen gun
at 25 psi to get rid of the majority of particles and cross-checked with a bright green flash light before and after blowing. The second stage of cleaning was done
below the clean room tent and included the wiping of all surfaces. The breadboard was then placed into the prepared lid of the transport box and clamped with peak
screws.

Unpacking of the template
The previously cleaned template was unpacked while the last layer of coverage was removed below the cleanroom tent.

Template adjustment on the breadboard
All peak screws of the clamping structure of the template where removed. The template was placed onto the breadboard only seperated by peak spacers.
All peak screws have been inserted for horizontal clapming. A calipper was used to measure the distance of each edge of the template to the edge of the
breadboard. For documentation the labeled side of the bradboard (facing away from the persons on the pictures) of the upside down breadboard is defined to 
be the south side, continuing clockwise with west, north and east. First rough alignment was done by shifting the template on the breadboard and then the 
peak screws where used for fine tuning. The caliper values measured where:
North   C 8.32mm     E 8.52 mm     W 8.41 mm
East     C 8.08 mm
South   C 8.32 mm
West    C 8.02 mm
(E indicating east side position, W indicating west side position and C indicating center position)

  344   Wed Apr 17 09:08:47 2019 StephenGeneralGeneralOMC(004): Unwrapping and preparing breadboard

[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.

 

Attachment 1: IMG_7635_packaging_of_sn06.JPG
IMG_7635_packaging_of_sn06.JPG
Attachment 2: IMG_7637_engraving_of_sn06.JPG
IMG_7637_engraving_of_sn06.JPG
Attachment 3: IMG_7641_particulate_before_top_gun_large_face.JPG
IMG_7641_particulate_before_top_gun_large_face.JPG
Attachment 4: IMG_7644_particulate_before_top_gun_small_face.JPG
IMG_7644_particulate_before_top_gun_small_face.JPG
Attachment 5: IMG_7646_particulate_after_top_gun.JPG
IMG_7646_particulate_after_top_gun.JPG
  343   Tue Apr 16 23:11:43 2019 KojiGeneralGeneralBorrowed items from the other labs

Apr 16, 2019
Borrowed two laser goggles from the 40m. (Returned Apr 29, 2019)
Borrowed small isopropanol glass bottole from CTN.

Apr 19, 2019
Borrowed from the 40m:
- Universal camera mount
- 50mm CCD lens
- zoom CCD lens (Returned Apr 29, 2019)
- Olympus SP-570UZ (Returned Apr 29, 2019)
- Special Olympus USB Cable (Returned Apr 29, 2019)

 

  342   Tue Apr 16 21:16:11 2019 KojiOpticsCharacterizationOMC(004): PZT testing for spare OMC

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). 

Quote:

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

 

  341   Tue Apr 16 17:24:56 2019 KojiOpticsConfigurationOMC(004): E Mirror selection

We are going to use E6, E9, E11, and E14 for BS1, SM1, SM2, and SM3. They (and E18) are all very similar.

The attachment is the excerpt from T1500060 with some highlighting

Attachment 1: E_Mirror_selection.pdf
E_Mirror_selection.pdf
  340   Tue Apr 16 16:52:36 2019 KojiOpticsConfigurationOMC(004): B Mirror selection

We are going to use B6 for the DCPD BS (BS2), and B1 for the QPD BS (BS3). Their role can not be swapped.

B6 has the best loss among the available ones, while the perpendicularity is not so critical due to the short arm.

B1 has the OK perpendicularity, while the loss is also moderately good.

The attachment is the excerpt from T1500060 with some highlighting.

Attachment 1: B_Mirror_selection.pdf
B_Mirror_selection.pdf
  339   Tue Apr 16 16:40:26 2019 KojiGeneralConfigurationOMC(004): A Mirror selection

We are going to use A5 and A14 for FM1 and FM2. (The role of these two can be swapped)

The reason for the selection is the better perpendicularity among the available prisms.

A11 has the best perpendicularity among them. However, the T didn't match with the others. The pair of A5 and A14 has a good matching with small compromise of the perpend.

The attachment is the excerpt from T1500060.

Attachment 1: A_Mirror_selection.pdf
A_Mirror_selection.pdf
  338   Tue Apr 16 16:35:09 2019 KojiOpticsConfigurationOMC(004): Glass breadboard selection

D1200105 SN006 was selected as the breadboard for OMC(004).
The reason is the best parallelism among the 
unused ones.

The attached is the excerpt from T1500060 with the #006 highlighted.

Attachment 1: BB_selection.pdf
BB_selection.pdf
  337   Tue Apr 16 11:36:36 2019 KojiOpticsCharacterizationOMC(004): PZT testing for spare OMC

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)

Attachment 1: IMG_7620.jpg
IMG_7620.jpg
Attachment 2: IMG_7623.jpg
IMG_7623.jpg
Attachment 3: IMG_7629.jpg
IMG_7629.jpg
Attachment 4: IMG_7630.jpg
IMG_7630.jpg
Attachment 5: IMG_7631.jpg
IMG_7631.jpg
Attachment 6: IMG_7632.jpg
IMG_7632.jpg
Attachment 7: IMG_7633.jpg
IMG_7633.jpg
Attachment 8: P_20190416_091537.jpg
P_20190416_091537.jpg
Attachment 9: IMG_7634.JPG
IMG_7634.JPG
  336   Mon Apr 15 21:11:49 2019 PhilipOpticsCharacterizationOMC(004): PZT testing for spare OMC

[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.

  335   Mon Apr 15 01:23:45 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #10)

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.

Attachment 1: IMG_7589.jpg
IMG_7589.jpg
Attachment 2: IMG_7590.jpg
IMG_7590.jpg
Attachment 3: IMG_7591.jpg
IMG_7591.jpg
Attachment 4: IMG_7592.jpg
IMG_7592.jpg
  334   Mon Apr 15 01:07:30 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #9)

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.

 

Attachment 1: IMG_7594.jpg
IMG_7594.jpg
Attachment 2: IMG_7595.jpg
IMG_7595.jpg
Attachment 3: IMG_7596.jpg
IMG_7596.jpg
Attachment 4: IMG_7597.jpg
IMG_7597.jpg
Attachment 5: IMG_7598.jpg
IMG_7598.jpg
Attachment 6: IMG_7600.jpg
IMG_7600.jpg
Attachment 7: IMG_7618.jpg
IMG_7618.jpg
  333   Mon Apr 15 00:39:04 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #8)

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.

Attachment 1: IMG_7601.jpg
IMG_7601.jpg
Attachment 2: IMG_7602.jpg
IMG_7602.jpg
Attachment 3: IMG_7603.jpg
IMG_7603.jpg
Attachment 4: IMG_7604.jpg
IMG_7604.jpg
Attachment 5: IMG_7605.jpg
IMG_7605.jpg
Attachment 6: IMG_7607.jpg
IMG_7607.jpg
Attachment 7: IMG_7608.jpg
IMG_7608.jpg
Attachment 8: IMG_7616.jpg
IMG_7616.jpg
  332   Mon Apr 15 00:08:32 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly post air-bake inspection (Sub-assy #7)

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).

 

Attachment 1: IMG_7609.jpg
IMG_7609.jpg
Attachment 2: IMG_7610.jpg
IMG_7610.jpg
Attachment 3: IMG_7611.jpg
IMG_7611.jpg
Attachment 4: IMG_7612.jpg
IMG_7612.jpg
Attachment 5: IMG_7613.jpg
IMG_7613.jpg
Attachment 6: IMG_7614.jpg
IMG_7614.jpg
  331   Sun Apr 14 23:58:49 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly post air-bake inspection

[Koji Stephen]

(Friday afternoon) We retrieved the PZT sub-assemblies to the clean room.

We started removing the ASSYs from the fixtures. We noticed that some part of the glass and PZT are ripped off from the ASSY and stuck with the fixture. For three ASSYs (except for #9), the effect is minimal. However, ASSY #9 has two large removals on the front surface, and one of the bottom corners got chipped. This #9 is still usable, I believe, but let's avoid to use this unit for the OMC. Individual inspection of the ASSYs is posted in the following entries.

This kind of fracture events was not visible for the past 6 PZT sub-ASSYs. This may indicate a few possibilities:
- More rigorous quality control of EP30-2 was carried out for the PZT ASSY bonding. (The procedure was defined after the past OMC production.) The procedure leads to the strength of the epoxy enhanced.
- During the strong and fast thermal cycling, the glass was exposed to stress, and this might make the glass more prone to fracture.

For the production of the A+ units, we think we can avoid the issues by modifying the fixtures. Also, reliable temperature control/monitor technology should be employed. These improvements should be confirmed with the bonding of spare PZTs and blank 1/2" mirrors before gluing any precious components.

  330   Thu Apr 11 21:22:58 2019 KojiGeneralGeneralOMC(004): PZT sub-assembly air baking

[Stephen Koji]

The baking of the PZT subassemblies was more complicated than we initially thought.

The four PZT subassemblies were placed in the air bake oven A. We meant to bake the assemblies with the ramp time of 2.5h, a plateau of 2h at 94degC, and slow ramp down.

The oven controller was started and the temperature has been monitored. The ramping up was ~20% faster than expected (0.57degC/min instead of 0.47degC/min), but at least it was linear and steady.

Once the temperature reached the set temperature (around t=120min), the temperature started oscillating between 74 and 94degC. Stephen's interpretation was that the PID loop of the controller was not on and the controller falled into the dead-bang mode (=sort of bang-bang control).

As the assembly was already exposed to T>70F for more than 2.5hours, it was expected the epoxy cure was done. Our concern was mainly the fast temperature change and associated stress due to thermal expansion, which may cause delamination of the joint. To increase the heat capacity of the load, we decided to introduce more components (suspension balance weights). We also decided to cover the oven with an insulator so that the conductive heat loss was reduced.

However, the controller thought it was already the end of the baking process and turned to stand-by mode (i.e. turned off everything). This started to cause rapid temp drop. So I (Koji) decided to give a manual heat control for mind cooling. When the controller is turned off and on, it gives some heat for ramping up. So the number of heat pulses and the intervals were manually controlled to give the temp drop of ~0.5degC/min. Around t=325, the temperature decay was already slower than 0.5degC/min without heat pulse, so I decided to leave the lab.

We will check the condition of the sub-assemblies tomorrow (Fri) afternoon.

Attachment 1: temp_profile.pdf
temp_profile.pdf
Attachment 2: bake.xlsx
  329   Thu Apr 11 21:22:26 2019 KojiMechanicsGeneralOMC(004): PZT sub-assembly gluing

[Koji Stephen]

The four PZT sub-assemblies were glued in the gluing fixtures. There were two original gluing fixtures and two additional modified fixtures for the in-situ bonding at the repair of OMC(002).

- Firstly, we checked the fitting and arrangements of the components without glue. The component combinations are described in ELOG 329.
- Turned on the oven toaster for the cure test (200F).
- Then prepared EP30-2 mixture (7g EP30-2 + 0.35g glass sphere).
- The test specimen of EP30-2 was baked in the toaster oven. (The result shows perfect curing (no stickyness, no finger print, crisp fracture when bent)
- Applied the bond to the subassemblies.
- FInally the fixtures were put in airbake Oven A. We needed to raise one of the tray with four HSTS balance weights (Attachment 2).

Attachment 1: IMG_7561.jpg
IMG_7561.jpg
Attachment 2: IMG_7567.jpg
IMG_7567.jpg
  328   Thu Apr 11 12:15:31 2019 KojiMechanicsConfigurationPZT sub assy mirror orientations
Attachment 1: PZT_subassy.png
PZT_subassy.png
Attachment 2: PZT_subassy.pdf
PZT_subassy.pdf PZT_subassy.pdf PZT_subassy.pdf PZT_subassy.pdf
  327   Thu Apr 11 10:54:38 2019 StephenGeneralGeneralOMC(004): preparation for the PZT subassembly bonding
Quote:

Preparation for the PZT subassembly bonding (Section 6.2 and 7.3 of T1500060 (aLIGO OMC optical testing procedure)
- Gluing FIxture (Qty4)
- 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.

  326   Wed Apr 10 19:22:24 2019 KojiGeneralGeneralOMC(004): preparation for the PZT subassembly bonding

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

  325   Fri Apr 5 23:30:20 2019 KojiGeneralGeneralOMC (002) repair completed

OMC(002) repair completed

When the cable harness of OMC(004) is going to be assembled, the cable harness of OMC(002) will be replaced with the PEEK one. Otherwise, the work has been done.

Note that there are no DCPDs installed to the unit. (Each site has two in the OMC and two more as the spares)

More photos: https://photos.app.goo.gl/XdU1NPcmaXhATMXw6

Attachment 1: P_20190405_222401.jpg
P_20190405_222401.jpg
Attachment 2: P_20190405_222509.jpg
P_20190405_222509.jpg
Attachment 3: P_20190405_222529.jpg
P_20190405_222529.jpg
  324   Fri Apr 5 20:50:54 2019 KojiOpticsCharacterizationOMC(002): QPD alignment

QPD#              QPD1       QPD2
Housing#          #004       #008
Diode#            #44        #46
Shim              (see OMC ELOG 323)

-------------------------------------
Power Incident    252.3 uW  266.0 uW
Sum Out           174.2 mV  176.0 mV   +0.3
Vertical Out      + 4.7 mV  +19.0 mV   +0.2
Horizontal Out    -16.1 mV  - 8.0 mV   +0.0
SEG1              -52.4 mV  -53.  mV   -0.1
SEG2              -37.6 mV  -47.  mV   -0.1
SEG3              -41.8 mV  -34.  mV   -0.1
SEG4              -43.7 mV  -36.  mV   -0.1

-------------------------------------
Spot position X   +39   um  +15. um  (positive = more power on SEG1 and SEG4)
Spot position Y   - 8.1 um  -56. um  (positive = more power on SEG3 and SEG4)
-------------------------------------

Responsivity[A/W] 0.69      0.66
Q.E.              0.80      0.77
-------------------------------------

Arrangement of the segments
View from the beam
/ 2 | 1 X
|---+---|
\ 3 | 4 /


---------------

I(w,x,y) = Exp[-2 (x^2 + y^2)/w^2]/(Pi w^2/2)

(SEG_A+SEG_B-SEG_C-SEG_D)/(SEG_A+SEG_B+SEG_C+SEG_D) = Erf[sqrt(2) d/w]

d: distance of the spot from the center
w: beam width

Attachment 1: P_20190405_215906.jpg
P_20190405_215906.jpg
Attachment 2: P_20190405_215927.jpg
P_20190405_215927.jpg
  323   Fri Apr 5 01:08:17 2019 KojiOpticsCharacterizationOMC(002): DCPD / QPD alignment

The beam height in the cavity became totally different from the previous one and the shims needed to be much thicker than before. This is probably because of the alignment of the newly-glue curved mirror.

As the beam height is 2~2.5mm higher, two shims need to be stacked. The preliminary check of the heights using the alignment disks (dummy PDs) suggested the following combinations.

QPD1(SHORT)  D1201467-03 (SN 007) + D1201467-03 (SN 008) (2.0 mm + 2.0 mm = 4 mm)
QPD2(LONG)   D1201467-01 (SN 001) + D1201467-01 (SN 002) (1.5 mm + 1.5 mm = 3 mm)
DCPD1(TRANS) D1201467-02 (SN 006) + D1201467-03 (SN 005) (1.75mm + 2.0 mm = 3.75 mm)
DCPD2(REFL)  D1201467-02 (SN 002) + D1201467-03 (SN 006) (1.75mm + 2.0 mm = 3.75 mm)

This resulted that the fixing button head socket screws for the PD housings to be replaced from 5/16" to 7/16". Stephen kept CLASS A spare screws from Jeff's time.

For the DCPD alignment, a cap-removed Excelitas 3mm InGaAs PD is used. -> This needs to be returned to the PD stock next time.

- DCPD1 was aligned using the zoomed CCD image (Attachment 1). Once the beam is aligned, the angle was tweaked to have the reflection nicely dumped by the glass beam dump (Attachment 2).

- DCPD2 was aligned too. (Attachment 2/3)

- The two housings were fastened by a torque wrench at 2 inch lb.

Next step:

Continue with the QPDs. The QPD amp was already set.

Notes:
The cable of the CCD monitor has a problem -> need to check what's wrong
The servo box probably have large offset at the output stage or somewhere (but not input stages).

Attachment 1: IMG_7521.JPG
IMG_7521.JPG
Attachment 2: IMG_7529.JPG
IMG_7529.JPG
Attachment 3: IMG_7539.JPG
IMG_7539.JPG
Attachment 4: IMG_7541.JPG
IMG_7541.JPG
  322   Fri Apr 5 01:07:18 2019 KojiOpticsCharacterizationOMC(002): transmitted beam images

There was a concern that the transmission from CM1 has additional fringes. The shape of the transmitted beams from CM1, CM2, and FM2 (main) werecaptured with WinCamD.
Indeed CM1 and CM2 have the fringes, but it does not exist in the main transmission. So it seems that the fringes are associated with the curved mirrors. But how???

Attachment 1: CM1trasns.png
CM1trasns.png
Attachment 2: CM2trasns.png
CM2trasns.png
Attachment 3: FM2trans2.png
FM2trans2.png
  321   Thu Apr 4 20:07:39 2019 KojiSupplyGeneralPurchase

== Office Depot ==
Really Useful Box 9L x 6 (delivered)
Really Useful Box 17L x 5 (ordered 4/4)
P-TOUCH tape (6mm, 9mm, 12mmx2, 18mm) (ordered 4/4)

== Digikey ==
9V AC Adapter (- inside, 1.3A) for P-TOUCH (ordered 4/4)
12V AC Adapter (+ inside, 1A) for Cameras (ordered 4/4)

== VWR ==
Mask KIMBERLY CLARK "KIMTECH Pure M3" ISO CLASS 3 (ordered 4/4)

  320   Thu Mar 28 16:36:52 2019 KojiMechanicsCharacterizationOMC(002) PZT characterization

As performed in the ELOG 202, the PZTs of the OMC 002 were tested.

DC response was measured by sweeping each PZT with 0-150V triangular voltage at 11Hz. Acquire 0.2sec of the tie series using an oscilloscope to get the PDH error, cavity transmission, and the sweep signal.

The voltage where the tranmission peaks were observed were fitted were recorded. One fringe corresponds to the displacement of 532nm. So the displacement and the applied volatagewere fitted witha linear function.

This gave the PZT response for PZT1 and PZT2 to be 14.9nm/V and 14.4nm/V.

 

AC response was measured with SR785. The PZT was shaken with 1~50mVpp signal with the DC offset of 5V while the OMC was locked with the feedback to the laser fast PZT. The transfer function from the applied PZT voltage to the servo output were measured. The closed loop TF was also measured to remove the effect of the servo control.  The DC levels of the responses were calibrated using the values above.

Attachment 1: PZT_Scan.pdf
PZT_Scan.pdf
Attachment 2: OMC_PZT_Response.pdf
OMC_PZT_Response.pdf
  319   Tue Mar 19 17:30:25 2019 KojiGeneralCharacterizationOMC (002) Test items

OMC #002 Optical tests

  • FSR measurement (done, 2019/1/8-9, 2019/4/1)
  • TMS measurement (done, 2019/1/9)
  • TMS measurement (with DC voltage on PZTs) (done, 2019/1/10)
  • Cleaning (done, 2019/3/19)
  • Power Budget (done, 2019/3/19, 2019/4/1)
  • PZT DC response (done, 2019/3/27)
  • PZT AC response (done, 2019/3/27)
  • QPD alignment (done, 2019/4/5)
  • DCPD alignment (done, 2019/4/4)
  • Beam quality check (done, 2019/4/4)

(Backscattering test)

(Cabling / Wiring)

  • (Attaching cable/mass platforms)
  • (PZT cabling)
  • (DCPD cabling)
  • (QPD cabling)

(Baking)
(First Contact)
(Packing / Shipping)

  318   Sat Feb 2 20:35:02 2019 KojiOpticsCharacterization Summary: OMC(002) HOM structure recalculation (after mirror replacement)

OMC (002) after repair
History:
Mirror replacement after the damage at H1. Measurement date 2019/1/10

Attachment 1: OMC_HOM_190110.pdf
OMC_HOM_190110.pdf
Attachment 2: HOM_PZTV.pdf
HOM_PZTV.pdf
Attachment 3: HOM_plot_PZT0_0.pdf
HOM_plot_PZT0_0.pdf
Attachment 4: Cav_scan_response_PZT.pdf
Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf Cav_scan_response_PZT.pdf
  317   Sat Feb 2 20:28:21 2019 KojiOpticsCharacterizationSummary: OMC(003) HOM structure recalculation

OMC (003)
History:
Measurement date 2014/7/5, Stored for I1, Installed to H1 2016/8 upon damage on 002

Attachment 1: OMC_HOM_140705.pdf
OMC_HOM_140705.pdf
Attachment 2: HOM_PZTV_PZT1_0V.pdf
HOM_PZTV_PZT1_0V.pdf
Attachment 3: HOM_plot_PZT0_0.pdf
HOM_plot_PZT0_0.pdf
Attachment 4: Cav_scan_response_PZT_HOM.pdf
Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf
  316   Sat Feb 2 20:03:19 2019 KojiOpticsCharacterizationSummary: OMC(002) HOM structure recalculation (before mirror replacement)

OMC (002)
History:
Measurement date 2013/10/11, Installed to L1 2013/XX

Attachment 1: OMC_HOM_131011.pdf
OMC_HOM_131011.pdf
Attachment 2: HOM_PZTV.pdf
HOM_PZTV.pdf
Attachment 3: HOM_plot_PZT0_0.pdf
HOM_plot_PZT0_0.pdf
Attachment 4: Cav_scan_response_PZT_HOM.pdf
Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf Cav_scan_response_PZT_HOM.pdf
  315   Sat Feb 2 16:17:13 2019 KojiOpticsCharacterizationSummary: OMC(001) HOM structure recalculation

Each peak of the transfer function measurement was fitted again with a complex function:

\begin{align} h(f;a_{\rm r}, a_{\rm i}, f_0, dT, \Gamma, a_0, b_0, a_1, b_1) & \nonumber\\ = (a_{\rm r} + i a_{\rm i}) e^{-i 2 \pi f dT} \frac{1}{1 + i (f - f_0)/\Gamma} &+ (a_0 + i b_0) + (a_1 + i b_1)f \nonumber \end{align}


OMC (001)
History:
Measurement date 2013/5/31, Installed to L1 2013/6/10~

Attachment 1: OMC_HOM_130531.pdf
OMC_HOM_130531.pdf
Attachment 2: HOM_PZTV.pdf
HOM_PZTV.pdf
Attachment 3: HOM_plot_PZT0_0.pdf
HOM_plot_PZT0_0.pdf
Attachment 4: Cav_scan_response_HOM.pdf
Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf Cav_scan_response_HOM.pdf
  314   Fri Feb 1 12:52:12 2019 KojiMechanicsGeneralPZT deformation simulation

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.

 

Attachment 1: pzt.png
pzt.png
  313   Sat Jan 12 22:49:11 2019 KojiOpticsCharacterizationPM-SM patch cable mode cleaning effect

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.

\begin{align} P_{\rm omcrefl} & = a P_{\rm nofib} + b P_{\rm fib} \nonumber \\ P_{\rm fibout} & = P_{\rm omcrefl} + (1-b) P_{\rm fib} \nonumber \\ P_{\rm tot} & = P_{\rm nofib} + P_{\rm fib} \nonumber \end{align}

and

\begin{align} P'_{\rm omcrefl} &= a P'_{\rm nofib} + b P'_{\rm fib} \nonumber \\ P'_{\rm fibout} &= P'_{\rm omcrefl} + (1-b) P'_{\rm fib} \nonumber \\ P_{\rm tot} &= P'_{\rm nofib} + P'_{\rm fib} \nonumber \end{align}

With the calibration between the refl PD and the power meter measurement,
  \begin{align} P_{\rm tot} &= 52.5 \pm 0.2 {[mW]} \nonumber \\ P_{\rm fibout} &= 35.5 \pm 0.2 {\rm [mW]} \nonumber \end{align}
\begin{align} P_{\rm omcrefl} &= 0.78 \pm 0.01\,\,{\rm [mW]} \nonumber \\ P'_{\rm omcrefl} &= 0.460 \pm 0.006\,\,{\rm [mW]} \nonumber \\ P'_{\rm fibout} &= 20.4 \pm 0.13 \,\,{\rm [mW]} \nonumber \end{align}

The solution of the equations is
\begin{align} a &= (4 \pm 4) \times 10^{-4} \nonumber \\ b &= 0.0219 \pm 0.0005 \nonumber \end{align}

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%.
 

Attachment 1: fiber_mode_cleaning.pdf
fiber_mode_cleaning.pdf
  312   Thu Jan 10 20:45:00 2019 KojiOpticsCharacterizationPZT test cable

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.

Attachment 1: OMC_PZT_wiring.pdf
OMC_PZT_wiring.pdf
ELOG V3.1.3-