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Wed Apr 10 00:40:30 2013

[Koji, Zach]

Tonight, we locked the "fauxMC". We obtained a visibility of >99%.

Koji had aligned it roughly last night, but we wanted to have a couple steering mirrors in the path for this practice cavity (the periscope mirrors will serve this function in the real setup), so we marked the alignment with irises and installed two extra mirrors.

After obtaining flashes with the WinCam placed at the output coupler, we removed the WinCam and put a CCD camera at one of the curved mirror transmissions and used this to get a strong TEM₀₀ flash. Then, we installed the REFL PD/CCD, swept the laser PZT and optimized the alignment by minimizing the REFL dips. Finally, we connected the RF electronics and locked the cavity with the LB box. We used whatever cables we had around to trim the RF phase, and then Koji made some nice SMA cables at the 40m.

One thing we noticed was that we don't have enough actuation range to keep the cavity locked for very long---even with the HV amp (100V). We are going to offload to the NPRO temperature using an SR560 or pomona box circuit. We may also make an enclosure for the cavity to protect it from the HEPA blasting.

Tomorrow, after we do the above things, we will practice measuring the transmission, length (FSR) and mode spectrum of the cavity before moving on to the real McCoy.

137

Wed Jun 5 01:06:35 2013

Zach

General

Characterization

L1 OMC as-built diagram

D1300507

143

Thu Jun 13 12:12:20 2013

Zach

General

[LLO] OMC and OMCS in LVEA

https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=7395

293

Thu May 3 21:45:58 2018

awade

General

Loan / Lending

Borrowed toaster oven

I’ve borrowed the black and decker toaster oven to dry some sonicated parts. It is temporarly located in the QIL lab.

405

Tue Nov 24 10:45:07 2020

gautam

Electronics

Characterization

The dark noise of the Q3000 QPDs

I see that these measurements are done out to 100 kHz - I guess there is no reason to suspect anything at 55 MHz which is where this QPD will be reading out photocurrent given the low frequency behavior looks fine? The broad feature at ~80 kHz is the usual SR785 feature I guess, IIRC it's got to do with the display scanning rate.

Quote:

The measured floor level of the dark current was below the shot noise level for the DC current of 0.1mA (i.e. 6pA/rtHz).

Tue Oct 16 14:50:54 2012

jamie, jeff

General

OMC breadboard/plate measurement dimensions

We have measured the dimensions and mass of the OMC glass plates/breadboards:

S/N	Mass (g)	Length (mm)	Width (mm)	Height (mm)	Notes
01	6146	449.66	149.85	41.42, 41.42	for LLO
02	6126	449.66	149.97	41.32, 41.32	for LHO
03	6143	449.76	149.98	41.39, 41.43
04	6139	449.78	149.81	41.40, 41.40	for 3IFO
05	6132	449.76	150.03	41.27, 41.31	corner chip, front-bottom-left^*
06	6138	449.84	149.71	41.42, 41.42

^* orientation is relative to "front" face, i.e. long-short face with S/N on it, with S/N upright.
Height measurements were made twice, once at each end.
TMeasurements of 03, 05, 02, and 06 were done in the open in the OMC lab. This was not thought to be too much of an issue since the plates
are already covered with particulate matter from the tissue paper that they were wrapped in.
Measurements of 04 and 01 were done on the optics table, under the clean room enclosure.

Note by Koji:

The scale of the bake lab was used. (Max 60kg, Min resolution of 1g)
The dimensions were measured by a huge caliper which Jeff brought from Downs.
S/N 01, 03, 04 look pretty similar. They should be the primary candidates.

286

Sat Jul 29 18:44:38 2017

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

393

Mon Sep 28 16:03:13 2020

rana

General

OMC Beam Dump Production Cure Bake

are there any measurements of the BRDF of these things? I'm curious how much light is backscattered into the incoming beam and how much goes out into the world.

Maybe we can take some camera images of the cleaned ones or send 1-2 samples to Josh. No urgency, just curiosity.

I saw that ANU and also some labs in India use this kind of blue/green glass for beam dumps. I don't know much about it, but I am curious about its micro-roughness and how it compares to our usual black glass. For the BRDF, I think the roughnesss matters more for the blackness than the absorption.

372

Fri Aug 23 11:11:44 2019

shruti

Optics

Characterization

Finding the curvature bottom

I attempted to fit the data taken by Koji of the beam spot precession at the CCD in order to find the location of the curvature bottom in terms of its distance (d) and angle ( $\phi$ ) from the centre of the mirror. This was done using the method described in a previous similar measurement and Section 2.1.3 of T1500060.

Initially, I attempted doing a circle_fit on python as seen in Attachment 1, and even though more points seem to coincide with the circle, Koji pointed out that the more appropriate way of doing it would be to fit the following function:

$f(i, \theta, r, \phi) = \delta_{i,0} [r \cos(\theta+\phi) + x_c] + \delta_{i,1} [r \sin(\theta+\phi) +y_c]$

since that would allow us to measure the angle $\phi$ more accurately; $\phi$ is the anti-clockwise measured angle that the curvature bottom makes with the positive x direction.

As seen on the face of the CCD, x is positive up and y is positive right, thus, plotting it as the reflection (ref. Attachment 2) would make sure that $\phi$ is measured anti-clockwise from the positive x direction.

The distance from the curvature bottom is calculated as

$d = \frac{rR}{2L}$

r: radius of precession on CCD screen (value obtained from fit parameters, uncertainty in this taken from the std dev provided by fit function)

R: radius of curvature of the mirror

L: Distance between mirror and CCD

R = 2.575 $\pm$ 0.005 m (taken from testing procedure doc referenced earlier) and L = 0.644 $\pm$ 0.005 m (value taken from testing doc, uncertainty from Koji)

	d (mm)	$\phi$ (deg)
C7	0.554 $\pm$ 0.004	-80.028 $\pm$ 0.005
C10	0.257 $\pm$ 0.002	-135.55 $\pm$ 0.02
C13	0.161 $\pm$ 0.001	-79.31 $\pm$ 0.06

373

Thu Aug 29 11:51:49 2019

shruti

Optics

Characterization

Wedging of the debonded PZTs - Calculation

Using the measurements of PZTs 12,13 taken by Stephen, I estimated the wedging angle and orientation following Section 2.3.1 of T1500060. The results can be found in Attachment1 and is summarised as follows.

For PZT 12, PZT 13 respectively:

Avg. height = 2.0063 mm, 2.0035 mm

Wedge direction (from the same direction as in the doc: positive right) = 120 deg, 120 deg

Wedge angles = 45.8 arcsec, 30.6 arcsec

This was done assuming that the measurements were taken uniformly at intervals of 60deg along the inner rim of the PZT. The diameter (2r) of the inner rim, according to T1500060, is 9mm. The measured heights were fitted with the function

$h = h_0 + \tan(\Omega)\text{ }r(1-\cos(\theta - \alpha))$

as depicted in Attachment2 to find wedging angle $(\Omega)$ and orientation $(\alpha)$ .

Quote:

Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it format).

These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material while mechanically removing glue. It is also possible that there is systematic error between the two sets of measurements. I did not run any calculations of wedge ange or orientation on these data.

Note that cleaning of debonded PZTs involved mechanically separating glue from the planar faces of PZTs. The second image shows the razer blade used to scrape the glue away.

There were thick rings of glue where there had been excess squeezed out of the bond region, and there was also a difficult-to-remove bond layer that was thinner. I observed the presence of the thin layer by its reflectivity. The thick glue came off in patches, while the thin glue came off with a bit of a powdery appearance. It was hard to be certain that all of the thin bond layer came off, but I made many passes on each of the faces of the 2 PZTs that had been in the bonded CM assemblies. I found it was easiest to remove the glue in the bonded

I was anticipating that the expected 75-90 micron bond layer would affect the micrometer thickness measurements if it was still present, but I did not notice any irregularities (and certainly not at the 10 micron level), indicating that the glue was removed successfully (at least to the ~1 micron level).

Quote:

Yesterday I measured the thickness of the PZTs in order to get an idea how much the PZTs are wedged.

For each PZT, the thickness at six points along the ring was measured with a micrometer gauge.
The orientation of the PZT was recognized by the wire direction and a black marking to indicate the polarity.

A least square fitting of these six points determines the most likely PZT plane.
Note that the measured numbers are assumed to be the thickness at the inner rim of the ring
as the micrometer can only measure the maximum thickness of a region and the inner rim has the largest effect on the wedge angle.
The inner diameter of the ring is 9mm.  

The measurements show all PZTs have thickness variation of 3um maximum. 
The estimated wedge angles are distributed from 8 to 26 arcsec. The directions of the wedges seem to be random
(i.e. not associated with the wires)  

As wedging of 30 arcsec causes at most ~0.3mm spot shift of the cavity (easy to remember),
the wedging of the PZTs is not critical by itself. Also, this number can be reduced by choosing the PZT orientations
based on the estimated wedge directions --- as long as we can believe the measurements.  

Next step is to locate the minima of each curved mirror. Do you have any idea how to measure them?

374

Thu Sep 5 15:40:42 2019

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 $= $\theta_{v, prism} +\theta_{v,wedge} +\theta_{v,mirror}$$

$\theta_{v, prism}$ was measured by Koji as described in elog 369.

$\theta_{v, wedge} [\text{arcsec}] = \theta_{PZT} \sin{\frac{\pi \phi_{PZT}}{180}}$ , $\theta_{PZT}, \phi_{PZT}$ are the wedge angle and orientation respectively and were measured earlier and shown in elog 373 .

$\theta_{v, mirror} [\text{arcsec}] = \frac{180 \times 3600 \times d}{\pi R_{RoC}} \times \sin{\frac{\pi (\phi-\phi_{ROT})}{180}}$ , The measurement of the location of the curvature bottom (d, $\phi$ ) of the mirrors is shown in elog 372 . The optimal $\phi_{ROT}$ is to be found.

These steps were followed:

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 $\phi_{ROT}$ .
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.
While calculating the tolerances, the dependence of the vertical deviations with rotation were also plotted (refer Attachment 3).
Two sets from available components with low total deviation and high tolerance were chosen.

Result:

These are the ones that were chosen:

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

The method of attaching them is depicted in Attachment 1.

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