40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  Cryo Lab eLog, Page 32 of 60  Not logged in ELOG logo
ID Date Author Type Categoryup Subject
  2557   Wed Aug 19 12:15:40 2020 aaronUpdateLab WorkNotice of entry

The cameras were unfortunately lost in the mail, but we can use my laptop or other camera. Ended up leaving to do a couple comsol things that needed completing today.

  2558   Mon Aug 24 13:21:40 2020 aaronUpdateLab Worknotice of entry

Notice of lab entry

Date of entry: 24 Aug 2020

time of entry: 12pm
time of exit:  
 
Purpose: stage 1 cavity setup
  2559   Mon Aug 24 13:22:32 2020 aaronUpdateLab WorkalaPSOMA

Did some mode matching, see the git.

  2561   Tue Aug 25 13:42:40 2020 aaronUpdateLab Workoptics setup

setting up PSOMA beam path

I took some photos of the existing layout. I'll just take apart the E beam path, and leave the W path unchanged for now as reference.

I moved the E fiber output coupler closer to the edge of the table, to make this path easier to reach.

Hopped around on the laser hysterisis curve for a minute. To optimize the temperature,

  1. Started with TEC on near room temperature, then turned on the laser driver with the current set to maximize power on the meter (S122C)
  2. increased the temperature setpoint (decrease resistance setpoint) slowly until the laser power starts to decrease.
  3. Turn off the laser driver. Decrease temperature setpoint to just below the maximum power setpoint.
  4. Turn on the laser driver. Total power is now 4.6mW, compared to ~2mW with TEC off.
  2562   Wed Aug 26 12:12:22 2020 aaronUpdateLab Workoptics setup
  • aligned beam along the NS axis using two irises and the existing 2x f=100 lenses from the E path.
    • HWP->steering mirror-> 90-10 BS -> iris -> lens -> lens -> iris -> PD
    • all transmitted beams dumped
  • Mounted a 1'' x 1m FL Si mirror in a polaris mount. Made a ring cavity with that and 2x mirrors coated for 45 deg.

optics

Can anyone tell me the specs / history of some of the custom optics in cryo? I'm mounting the 1m Coastline mirror and will start with that in the PSOMA cavity.

  • Laseroptik 1'' mirrors. Batch # 19028Kel. Part(?) numbers L-13997, L-13998. (these are in red boxes cases w clear lid)
  • Coastline Optics 1.0''x0.25'' FS substrates. Coated for 1550nm at 45 degrees. (these are in stacks cylindrical clear cases, and include some witness and rejected samples)
  • Coastline optics 1'' silicon substrate, 1 meter focal length. SN 1.0-Si-1.0M
  • Photon Laseroptik 1'' FS substrates (~50), labeled 75S308926. Also labeled with a wedge angle or what looks like a focal length (no unit)
  • Two stacks from Gooch & Housego, taped in bubble wrap with the data sheet. These are coated for 1550nm, transmission ~1% S and ~5% P at 45 deg.
  2564   Fri Aug 28 16:59:59 2020 aaronUpdateLab Workoptics setup

I measured the transmission of the Coastline 1m mirror at 180. ppm (S122C).

Alignment procedure while setting location of optics:

  1. use 2x irises to constrain a beam path at the locations of the eventual MZ input BS and the cavity BS.
  2. Place the first (R~1) flat mirror at 45 degrees centered on the beam line. Use this mirror to steer into an iris at the location of the cavity's curved mirror.
  3. Use steering optics to direct the eventual transmission beam into the trans mon PD (PDA 20CS)
  4. Place the curved mirror at near normal incidence. Use this mirror to steer the beam through irises at the location of the MZ output BS and cavity BS.
  5. Use steering mirrors to send the beam to the refl PD (PDA255).
  6. Place the cavity BS and steer the reflected beam to the refl PD.

Alignment procedure subsequently:

  1. Misalign the cavity BS
  2. Use the cavity mirrors to steer the circulated reflection into refl PD.
  3. Use cavity BS to align prompt reflection into refl PD.

 

  2565   Mon Aug 31 10:00:25 2020 aaronUpdateLab Workoptics setup

Here's the layout.

Some easy things that should be changed:

  • Transmission through the cavity end mirror should go to a steering mirror before PDA20CS
  • Should clamp the cables (eg power to PDA255) with something soft so they stay in place and aren't strained
  • Need to dump the reflection from transmon PD. Do we really need to dump transmission through mirrors with frosted backs?
Attachment 1: 200828_layout.jpg
200828_layout.jpg
  2566   Wed Sep 2 16:19:57 2020 shrutiUpdateLab Worklab entry, information gathering

Notice of lab entry: 20 Sep 2020   evening

Fiber modulators on the table :

1. Intensity modulators (BW: up to 12 GHz) MXAN-LN-10

2. EOM phase modulators (BW: up to 150 MHz) MPX-LN-01

Dimensions of vacuum cans mentioned in attachments.

Attachment 1: 7BA40146-4F86-4819-8D6C-FFDC8F246E50.jpeg
7BA40146-4F86-4819-8D6C-FFDC8F246E50.jpeg
Attachment 2: 129FE089-1E57-4E6D-9E77-F80F8E124CD1.jpeg
129FE089-1E57-4E6D-9E77-F80F8E124CD1.jpeg
  2570   Tue Sep 22 21:30:07 2020 aaronDailyProgressLab Worklab entry, supplies

notice of lab entry

Tue Sep 22 21:33:30 2020

inventory

I'm cleaning a bit, and gathering items not in use or in need of repair. They would make less mess in my office.

took an inventory of optics cleaning supplies, first aid kit, general cleaning supplies, wipes, etc. I found most were included in the first round inventory, but I took photos this time to convince my future self of object permanence. Will add to the wiki and update in a bit.

entered QIL, CTN

gloved up, shoe covers, went to QIL to check out the sprinklers and CTN to grab a GHz spectrum analyzer (HP8560E).

out: Wed Sep 23 00:20:03 2020

  2576   Tue Oct 27 15:57:27 2020 shrutiDailyProgressLab Workpsoma locking

Today I modified the optical setup with the aim of obtaining the beat between the two diode lasers for phase-locking.

I added pick-off polarizing beamsplitters with HWPs in each path for now (to be able to adjust their power) and mixed them at a 50/50 non-polarizing beam-splitter to eventually reach a Newfocus 1811 low noise PD.

I will add pictures and more details later.

 

  2577   Wed Oct 28 12:42:31 2020 shrutiDailyProgressLab Workpsoma locking

Phase-locking the two lasers:

Updates:

- Although when we talked about adjusting the MZ-phase, we decided that having the phase/path length control with fiber components might be better initially (Refer Attachment 2), for now I began doing everything in free-space.

- Attachment 1 shows the setup as it is now. Previously I'd placed polarizing beam splitters instead of 90/10 beam-splitters because I thought it would be easier to work with, but now changed my mind and decided to stick with what we planned.

Next steps:

(Once the beat is obtained on the spectrum analyzer)

1. Adjust set-point temperatures to adjust beat frequency to the right frequency.
Since ideally we want the two frequencies to be identical, it might be a good idea to add an AOM to one of the paths so that the first order beam is mixed with the other laser and this beat be compared to a stable reference for phase-locking.
But, initially we plan to skip the AOM.
2. Adjust the PID parameters if needed
3. Add electronic components

- Measure the laser frequency noise


29 Oct 20:

I've added Attachment 3 -- which is the current free space version and some PLL electronics. 

- It does not show the Mach-Zehnder part as that will be added only later

- This setup is asymmetric but in a future version we will change that

Attachment 1: Setup2020Oct27.pdf
Setup2020Oct27.pdf
Attachment 2: psoma_PLL.pdf
psoma_PLL.pdf
Attachment 3: psoma_pll_freespace_intermediate.pdf
psoma_pll_freespace_intermediate.pdf
  2582   Thu Nov 19 11:23:44 2020 shrutiUpdateLab Workpsoma locking

Attachment 1: An updated version of the diagram in elog 2577 where the path lengths to the beat beam-splitter are identical. The fiber launchers and some components have been moved around, but everything after PO1.1 along the beam has been retained as before.

Attachment 2: Retaining the same configuration to the beat BS, the cavity with Mach-Zehnder interferometer has been added. Also the path lengths to the MZ input BS along both laser beam paths have the same length. Except for the ring cavity, the Mach-Zehnder is also balanced.

Attachment 3: Updates pertaining to the current setup

  • Work in progress to achieve the configuration in Attachment 1.
  • I have switched the two PDs so the beat can be measured with the Newfocus 1611 (has a larger BW) and the noise measurement with the east laser can be done with the Newfocus 1811.
  • I removed the 10/90 pick-off circled in green, so that would have to be added to the path to continue the noise measurement.

 

Attachment 1: PLL_FS_sym.pdf
PLL_FS_sym.pdf
Attachment 2: MZ_PLL_FS_sym.pdf
MZ_PLL_FS_sym.pdf
Attachment 3: NewBeat.pdf
NewBeat.pdf
  2585   Tue Nov 24 10:16:04 2020 shrutiUpdateLab Workpsoma locking

Updates

- Found a suitable power cable M-M for the New Focus 0901 power supply on the east table (I did not realize yesterday that these were the same cables). Then I checked the voltage on the pins and they were fine.

- Using the New Focus 1611 (1 GHz PD) powered by the New Focus 0901 +-15 V / 0.3 A max. power supply, I tried finding the beat note. I looked at the RF output on a HP 8560 E spectrum analyzer and the DC output on an oscilloscope.

The DC output ranged from 500 mV to over 1 V as I scanned the temperature of one or both lasers.

- When the east laser temperature read roughly 8.34 kOhm and west was 9.04 kOhm I saw a pattern as in Attachment 2.

Changing the temperature slightly did cause the peaks to shift about, and further when I changed the polarization of the east laser using the HWP the height of the peaks varied. They also disappeared when either of the beams were blocked.

The estimated peak power in the taller peaks is ~0.1 µW from the plot.

- I also tried scanning the temperature of both lasers again to possibly find a single peak. No luck yet.

Today, I didn't check the alignment very carefully and I probably have to tune it further after the changes that Aaron and I made over the past few days.

The next step is to do the phase-locking.

 

 

Attachment 1: BeatSetup.pdf
BeatSetup.pdf
Attachment 2: BeatOrNot.pdf
BeatOrNot.pdf
  2588   Fri Nov 27 13:38:18 2020 ShrutiUpdateLab Workpsoma locking

Attachment 1: Video of spectrum analyzer with zoomed out beat after turning off the PID loop of west laser

Attachment 2: Another image of the zoomed in spectrum when the PID is on.

Attachment 1: Beat.mp4
Attachment 2: BeatZoomed.pdf
BeatZoomed.pdf
  2589   Fri Nov 27 19:43:33 2020 KojiUpdateLab Workpsoma locking

Isn't the PID oscilating at 10MHz?

  2611   Thu Jan 21 15:25:13 2021 aaronDailyProgressLab Work 

Enter Thu Jan 21 15:25:08 2021

resealed the HEPA filter

over the lab's air intake with Loctite silicone sealant. The rubber cement I used last time delaminated, and I'm hoping this sealant contours to the rough wall paint and proves more effective.

Historically, sealing the HEPA filter decreased the lab temperature. Attachment 1 shows the lab temperature for the last 17 days -- as you can begin to see, sealing the HEPA actually increased the lab filter. This is unfortunate, but consistent with the HVAC blowing hot air despite being set to cool.

 

Organizing electronics rack

I relabelled the 'E' and 'W' path to 'North' and 'South'. This should be less confusing, as the lasers' fiber components run parallel from west-to-east (one laser is north of the other). It would be good to continue labeling, including the AC power cables. I started a techmart cart for cable solutions from digikey (+torque wrench, panel mount SMA feedthroughs, to avoid sending RF through BNC, rack mount components).

Bypassed lossy AOM

The South laser is losing >8dB passing through its AOM. I've taken this AOM out of the path, so the South laser now runs from its Faraday isolator directly to its EOM. For symmetry, I've also removed the North laser's EOM, so the north laser passes through an AOM before being sent to a 90-10 beam splitter. With this modification, the power at the laser launch for the north laser is 7.3 mW and the south is 6.2 mW (the AOM is expected to be lossier than the EOM).

For PSOMA we typically think of our signal being an amplitude modulation, while the pump is phase-modulated for locking. With this modification, the north laser is playing the role of 'signal', while the south laser plays the role of 'pump.' Fine for now, but of course eventually we'll want to swap in a higher power laser for the south (pump) path.

I noticed that the latex gloves being used to softly clamp the AOM have begun to stiffen and deteriorate. Touching the glove at all breaks it into small pieces. This is worrying, so I unmounted the AOM and replaced the gloves. I will look into butterfly mounts and soft, non-degradable cable clamps for the future.

miscellany

  • Pulled aside some bad BNC cables for repair (connector loose, no strain relief).

Exit Thu Jan 21 20:20:27 2021

Attachment 1: Screenshot_from_2021-01-21_19-57-47.png
Screenshot_from_2021-01-21_19-57-47.png
  2657   Fri Feb 19 13:24:10 2021 aaronDailyProgressLab Work 

Enter Fri Feb 19 13:24:02 2021

  • The power strip for the lab workstations was unplugged. Was there a reason for this? I plugged it back in. Nothing wrong necessarily, but since it seems unrelated to anything on the elog and the hall lights were also off want to be sure there wasn't an unauthorized/undocumented lab entry.  
  • I found a slotted lid for rack electronics next to the cymac / cryo cavs rack, and used it to close the OCXO preamp box on PSOMA rack. I think it belonged to the ISS box on cryo cavs rack, which is currently not in use.
  • The Valon 3010 frequency divider had a loose screw rattling around inside. I opened the box (grounded, no power), secured the loose screws, and put the divider in the RF drawer.
  • Moved over the l-He dewar a few inches to confirm we have enough room for a 48" shelf (gap is now 49"). Also lowered its rubber feet, so it is resting on the fixed feet rather than the wheels. 
  • The label makers in EE and cryo are in the Casio family (for reference) 

 

A lot of the electronics around the lab use green for the negative supply line, and black for ground. I figured I just remembered the convention wrong, but from what I can find online the standard is green for ground and black/red for line in both US and EU... I don't want to change this local convention, but is there a reason we use it? Is this just cryo, or other WB labs / 40m? Since our colors are nonstandard, it's really necessary to label all power wires.

Mostly was fixing the AI chassis.

exit Fri Feb 19 22:01:12 2021

  2674   Fri Mar 5 14:36:00 2021 aaronDailyProgressLab Worklearned something about measuring clocks

enter about 2pm

daq

  • chatted with Radhika, who is going to get our particle counter logging again.
    • We found the services script that Duo and others had worked on in controls@cominaux:~/services, but many of the corresponding files in /etc/systemd/system were null linked.
    • In the process, I remembered that I'd tried to initialize the x1oma model again, but was unsuccessful. Consequently, cymac crashes during starting 'all' frontends.
    • Regardless, one could always caget the slow channels to see what's up (eg caget C5:PEM-COUNT_05UM returns the 5 um particle count). The data may not be saved to frames by cymac1, but at least the particle counter seems to be talking with cominaux.
  • untangling cymac1
    • Undid the steps I had taken to try to install x1oma:
      • Removed x1oma entry from /etc/advligorts/systemd_env
      • removed x1oma entry from /etc/advligorts/master
      • Manually restart rts-local_dc and rts-daqd services using systemctl
      • Rebooting cymac after these changes seems to have resolved the issues with frontends, but I still have white boxes for the GPS signal on X0DAQ (attachment 1).
    • meanwhile spirou's cds-workstation package is broken (no medm, for example).

Three Corner Hat to Allan Covariance [aka Cross-variance, aka Groslambert Variance]

A conversation with Rana had me thinking again about the 2-channel, 'coherent hat' measurement, where one compares the beat note between a laser of interest (X) and two other lasers (N, S). It felt like there should be enough information there. If I know $(\phi_{X}-\phi_{S})^2\equiv \Delta_{SX}$ and likewise for $\Delta_{NX}$, I ought to know the difference between I and Q.

Indeed I found this paper comparing the two methods... looks promising! The authors have further work quantifying the confidence intervals for the so-called Allan covariance.

The method is a natural extension of the Allan variance, where the phase noise on an oscillator as a function of frequency (1/t) is estimated by the autocorrelation of the oscillator's frequency at varying time separations (t). "Allan covariance" then is the same method applied to a set of different oscillators, where the oscillator frequencies are cross-correlated. I'll adapt the equations below from the paper to use more familiar notation.

Let $\phi_i$ denote the phase error (additonal phase relative to the carrier frequency) on the i'th laser (N, S, and X, for our cryo lab measurement). We want to estimate the phase noise of the TeraXion laser (\phi_X) by measuring the phase errors of the beat note between X and the N and S lasers (\phi_{NX}, \phi_{SX}). To see why the covariance of $\phi_{NX}$ and $\phi_{SX}$ gives a good estimate of the variance of $\phi_X$, consider

\phi_{NX} = \phi_N -\phi_X+\theta_{NX}

\phi_{SX} = \phi_S -\phi_X+\theta_{SX}

\implies \langle \phi_{NX}\phi_{SX}\rangle = 2\langle\phi_N\phi_S\rangle + 2\langle\phi_X^2\rangle -\langle\phi_N\phi_X\rangle - \langle\phi_S\phi_X\rangle + \langle\phi_S\theta_{NX}\rangle + \langle\phi_N\theta_{NX}\rangle - \langle\phi_X\theta_{SX}\rangle - \langle\phi_X\theta_{NX}\rangle

Since the expectations of all the uncorrelated terms are 0, we can conclude that as long as the measurements were taken simultaneously,

\langle\phi_X^2\rangle_\tau\to \langle \phi_{NX}\phi_{SX}\rangle

We should (and the paper does) use the phase errors $\phi$ to define a corresponding frequency error at each timestep $k$ set by our sampling period $\tau$, $f_i(k) \equiv \frac{\phi_i(k)-\phi_i(k-1)}{\tau}$. The frequency error is then $\Delta_i(k) = f_i(k)-f_i(k-1)$. The Allan variance is the variance of that frequency error, while the Allan covariance is the covariance of $\Delta_i$ with $\Delta_k$. Averaging the residuals makes explicit the dependence on $\tau$ and according to David Allan "effectively modulates the bandwidth in the software allowing one to distinguish between white-noise phase modulations (PM) and flicker-noise PM." I'm a bit unclear why it is necessary to take the second difference (that is, correlating frequencies separated by \tau rather than directly phases separated by \tau), but I think this paper from Allan goes into a bit more depth. My best guess is, it's because flicker phase noise (which asymptotes with infinite slope at low frequencies) will show up as a DC offset that is consequently not averaged away in terms like $\langle\phi_N\phi_S\rangle$. Taking a second difference means rather than negating this DC offset once (as I did above by defining $\phi_i$ as a phase error), phase noise below the sampling rate is discarded with each measurement time step.

With the frequency noise estimate from Allan (co)variance and some knowledge of the power law dependence of the noise, one can derive a corresponding spectral density. The Allan (co)variance with a particular sampling rate \tau corresponds to sampling the frequency-domain noise distribution with a function related to the Fourier transform of the chosen time-domain estimator. See the paper on converting between time and frequency domain noise estimates from Allan (linked above and here).
 

measurement

Very exciting! Sketch of the measurement with equipment on our tables in attachment 2. Whoops, we only have a free space 1811, not a fiber coupled one. Between that and the floppy path to PSOMA table, I'm going to think further on this measurement and try it next week. Maybe I can pick up some spare fiber parts from the 40m when I stop by to search for a transformer. In the meantime, yesterday's log has been updated with the current noise spectra.

exit Fri Mar 5 20:47:39 2021

Attachment 1: Screenshot_from_2021-03-05_15-14-24.png
Screenshot_from_2021-03-05_15-14-24.png
Attachment 2: 8B3029C0-A1D3-4044-B238-68D545187BE5.jpeg
8B3029C0-A1D3-4044-B238-68D545187BE5.jpeg
  2677   Mon Mar 8 12:11:52 2021 aaronDailyProgressLab Workallan covariance

I've attached a new diagram for this measurement. Instead of using two RFPD, I'll mix all three beams on one RFPD and separate the notes with passive filters. I'll use the N and S PSOMA lasers as reference clocks to measure the frequency noise of the Teraxion laser.

  • Rearranged the fiber components as shown in the diagram, trying to minimally disrupt the PSOMA path
  • Connected an SMA power splitter to some HP and LP BP minicircuits filters
  • Moved the ITC510 combination controller that was controlling cryo cavs E laser TEC (not in use) over to PSOMA rack. Now, both PSOMA N and S lasers are being controlled by separate ITC502 controllers; PSOMA N TEC is still on the TED 200 C.
    • Labelled disconnected cables (cryo cav E TEC and E temperature tuning) so we can find them again
    • Now, PSOMA S laser LD and TEC are being controlled by our ITC502, N laser TEC is controlled by TED 200 C, and N LD controlled by ITC510.
    • ITC510 has a larger range but worse quoted current noise properties than ITC502. In principle this shouldn't matter, as the measurement will be insensitive to frequency noise on the N and S lasers.
    • I set the LD current limit on ITC510 to 144.9 mA. It was at 125 mA.
  • DC power levels in measurement configuration
    • 550 uW total
    • 150 uW due to PSOMA S laser
    • 52 uW due to PSOMA N laser
      • I realized I sent 0.6 mW in the wrong direction through the PSOMA N EOM. After swapping the connectors (so 0.663 mW is entering the 'in' port of the EOM), I get 304 uW out of the EOM.
        • This is worse than the specified 2.7 dB insertion loss, which I measured in January.
        • I think Rana's measurement last week was transmitting Teraxion through this EOM.
        • I've taken the N EOM out of the path for now. Hoping I haven't damaged this.
    • 348 uW due to TeraXion laser
  • RF beat notes
    • I tuned the N and S LD currents to achieve the desired beat note spacing
      • S-X beat note (-12 dBm) at 32.5 MHz. I have a 27-33 MHz bandpass filter. I was using a 22 MHz lowpass filter, but realized I could separate the other two peaks a bit more by increasing this beat frequency and using a BPF.
      • N-X beat note (-27 dBm) at 98 MHz. I'm using a 90 MHz highpass filter, and want to be somewhat away from the corner where the phase changes rapidly.
      • This puts the NS beat note (-59 dBm) at about 65.5 MHz, outside the bands of both passive filters.
    • After fixing the beat frequencies, I send 1611's RF out to a splitter, followed by passive filter, and onto the two moku input channels in phasemeter mode.
      • The filters are
  • Measurement
    • Cleared moku ram with 
      • python [path_to_scripts]mokuCleanRAM.py -i 10.0.5.253
    • Left the room, and started a measurement from spirou with
      • python [path_to_scripts]mokuPhaseMeterTimeSeries.py -c both -d 450 -i 10.0.5.253 -s veryfast --useInternal --fileType bin
      • Use DC coupling to avoid the 100 Hz corner for Moku's AC coupling.

      • I observed substantial frequency drift (>30 MHz) during the measurement time (possibly from cycling the lights earlier). I took a second measurement with lights on after keeping the lights on for ~10 min, haven't yet seen if there was further drift. 

    • not sure why the moku has a new IP? Also sometime during my measurements the IP address was reassigned back to 10.0.5.220 (from 10.0.5.253 earlier today), though I didn't change its ethernet port. 

    • To measure the high frequency noise (> 7 kHz), I ran

      • python [path_to_scripts]mokuPhaseMeterTimeSeries.py -c both -d 90 -i 10.0.5.253 -s ultrafast --ac --ac2 --useInternal --fileType bin
      • This time I did ac couple the inputs

Update: Meh, the frequency drifted too much to be useful (20 MHz over 7.5 minutes measurement time).

Attachment 1: 9EEB7450-A584-4085-8F4F-0F70F164AF13.jpeg
9EEB7450-A584-4085-8F4F-0F70F164AF13.jpeg
  2688   Fri Mar 19 11:08:15 2021 aaronDailyProgressLab Work 

Lab temperature is high again (85 at the particle counter), but apparently hasn't been logging. Attachment 1 is the set of status screens -- still no GPS, and yellow CFC.

incoherent three corner hat

Measured beat note with 3 lasers incident on 1611, RF out sent through SLP-21.4 to moku phasemeter

  • python [path_to_scripts]mokuPhaseMeterTimeSeries.py -c ch1 -d 450 -i 10.0.5.220 -s veryfast --useInternal --fileType bin --altFileName "L1L2_note"
    • where L1L2 are the lasers being measured (SX, NX, NS)

  • DC level on 1611 0.5 mW

  • In all three measurements, the phaselock was lost when the beat note drifted too close to DC. I'm trying again with the SLP-100 to give myself some more range.

  • really need to put these fibers in a box

While waiting for the measurements,

Update:

Attachment 1: Screenshot_from_2021-03-19_11-09-04.png
Screenshot_from_2021-03-19_11-09-04.png
Attachment 2: lasers_ASD.pdf
lasers_ASD.pdf
  2690   Mon Mar 22 12:05:41 2021 ranaDailyProgressLab Work 

What happened to the temperature logging? Has the CDS system stopped recording data due to model changes, or is it just the python for the dust monitor?

  2691   Mon Mar 22 13:28:32 2021 aaronDailyProgressLab Worklab temperature logging

Attachment 1 shows the most recent temperature data available on nds.

Separate from the dust monitor, we have an AD590 set up as a temperature sensor read by the Acromag, which interfaces with cominaux. This is the channel that cymac is supposed to write to frames as X1:AUX-LAB_TEMP_[K, F, C], but the value read by cominaux is currently (and has been) 0. I've confirmed the signal is reaching the acromax ADC on the correct channel.

The dust monitor is a particle counter (GT-526) that also shows temperature and relative humidity, and is read by cominaux over ethernet. Despite an "error reading and converting data from the counter" shown in cominaux:~/services/particlecounter.log between Feb 3 and today, caget'ing the channel C5:PEM-COUNT_TEMP (or the particle counts) returns the expected value (89-90 F). However, cymac has not been logging these frames and I can't access live or lookback data through nds.

I see that daqd.service and nds.service on cymac1 are both dead linked to /etc/systemd/system/[nds, daqd].service. Neither service script still exists in cymac1:/etc/systemd/system, only the 'old' version of these scripts. I think binaries for nds and daqd now live in /opt/rtcds/tst/x1/target/fb, and the standalone_edc service is meant to pull data from epics.

If I run standalone_edc, I get an error 'edc.ini' failed to open, and there are no channels to record; this service is not running on cymac1. /opt/rtcds/rtscore/edc_status.json is empty.

Quote:

What happened to the temperature logging? Has the CDS system stopped recording data due to model changes, or is it just the python for the dust monitor?

 

Attachment 1: Screenshot_from_2021-03-22_14-08-10.png
Screenshot_from_2021-03-22_14-08-10.png
  2692   Mon Mar 22 21:41:09 2021 ChrisDailyProgressLab Worklab temperature logging

standalone_edc now works, and data from the temperature sensors (and other aux epics channels) is again being recorded.

The version of standalone_edc we had from RCG 4.0 silently fails to acquire data, unless symmetricom timing hardware is present. We don’t have such hardware in the cymac. I upgraded cymac1 to RCG 4.1 in order to get a newer version of standalone_edc. It can now use the IOP model as a timing source (--sync-to=x1iop_daq was added to the argument list). All models were rebuilt and reinstalled after the upgrade.

To minimize the chance for confusion, I removed the old nds/daqd service files, and archived the /opt/rtcds/tst/x1/target/fb directory. None of that is used anymore.

  2693   Tue Mar 23 11:07:56 2021 shrutiDailyProgressLab Worklab temperature logging

Lab temperature is now stabilized. The particle counter is now logging the temperature, but not the AD590 which records X1:AUX-LAB_TEMP_F.

The AD590 history also seems different from the previous record.

Attachment 1: Screenshot_from_2021-03-23_11-06-46.png
Screenshot_from_2021-03-23_11-06-46.png
Attachment 2: Screenshot_from_2021-03-23_11-04-15.png
Screenshot_from_2021-03-23_11-04-15.png
  2749   Mon Jun 7 13:23:33 2021 aaronDailyProgressLab Workmonitoring PDH signal on cymac

[aaron, shruti]

We would like to start recording our PDH error signal on cymac, both for noise budgeting and to provide slow feedback to the laser temperature.

Today we ran a couple cables from the PSOMA rack to the fast ADC/DAC boxes. Then, updated the x1oma model to record the N and S PDH error signals as _DQ channels. Next step is to define some softIOC channels for the PID controller. Attachment 1 shows the status lights after modifying the x1oma model, and disabling the models for older Cryo Lab experiments.

Attachment 1: status.png
status.png
  2754   Tue Jun 15 16:33:35 2021 aaronDailyProgressLab Workslow controls

[shruti, aaron]

Ran more cables to the ADC/DAC for PSOMA, and started setting up the soft channels to do slow control of the temperature setpoint.

  • Fast ADC channels 0-3 are mapped to the cavity PDH signal, control signal, reflection DC level, and transmission DC level respectively
  • Slow ADC channel 0 is mapped to the S laser driver temperature monitor
  • Slow DAC channel 0 is mapped to the S laser driver temperature tune

Beware, the temp tune setting seems to be an 'absolute' setpoint rather than a relative tuning on top of the setpoint from the front panel. We'll be testing this out in more detail.

  2757   Thu Jun 17 12:14:33 2021 aaronDailyProgressLab WorkTemp tune not absolute

I measured the voltage from X1:OMA-S_TEMP_TUNE, and found caputing some value on that channel resulted in seemingly random voltages from that DAC channel. Modifying the epics record for X1:OMA-S_TEMP_TUNE to match the other analog output channels fixed the problem, namely commenting out the PREC, ASLO, and SCAN fields. The temp tune channel now reads the actual voltage from Acromag analog output channel 0.

I renamed the fast channels for clarity, and created some subsystems.

  • ERC = East Ring Cavity (anticipated a West cavity)
  • SLD = South Laser Diode (anticipating a North laser)
  • Also renamed the slow channels to match the new naming convention. X1:OMA-SLD_TEMP_[MON, TUNE]
Attachment 1: Screenshot_from_2021-06-17_12-54-07.png
Screenshot_from_2021-06-17_12-54-07.png
  2760   Mon Jun 21 15:34:09 2021 aaronElectronicsLab Workswapping mixer

I swapped out the level 17 mixer in our PDH setup for a level 7 (ZFM-2-S+), and put it all in a box (attachment 1).

This let me remove the 10 dB attenuator before the LB box, though I had to add a 6 dB attenuator on the LO.

I measured the open loop transfer function again with the new mixer, and saw a 34 kHz UGF (attachment 2. I wasn't very careful to maximize the gain of the LB box). No correction was needed, since there is no longer an attenuator at either input of the LB box.

Attachment 1: A172449C-4B5D-47C1-B7FC-014B6CC28471.jpeg
A172449C-4B5D-47C1-B7FC-014B6CC28471.jpeg
Attachment 2: 796CBB56-3AA5-48D6-A344-F8239D9E605D.png
796CBB56-3AA5-48D6-A344-F8239D9E605D.png
  2762   Wed Jun 23 11:36:49 2021 shrutiElectronicsLab Workswapping mixer

I just switched the mixer back to level-17 and changed the low pass filter to SLP-5+ (5 MHz corner)

Attachment 1: MixerandLPFupdate.pdf
MixerandLPFupdate.pdf
  2777   Thu Jul 8 14:51:08 2021 shrutiDailyProgressLab WorkSetting changes

Following our discussion earlier when we realized that the AC electronics of the 1811 may be saturating, since our RF power (at the mod freq of 33.59 MHz) is near or over 55 microW, I added an additional 10dB attenuator before the EOM. The total attenuation is now 40 dB. To compensate for this I removed the 10 dB attenuator at the input of the LB1005.

I also added a 50 ohm terminator in parallel to the 20 dB attenuator at the analog input modulation port of the ITC 502 current driver. This is to ensure a more or less accurate 20 dB attenuation of the control signal since the ITC 502 input has an impedance of 10 kOhm.

Everything seemed to lock once again when the gain on the LB1005 was increased from 5 to 6.

 

  2778   Thu Jul 8 19:10:59 2021 aaronDailyProgressLab WorkSetting changes

We should note that the LB box driving into 50 Ohm is current limited at its output (assuming we don't narrow the voltage window using the trim pots on the back panel). It can supply up to +- 20 mA, so if we see control voltages approaching 1 V we are nearing saturation of the servo controller.

Quote:

I also added a 50 ohm terminator in parallel to the 20 dB attenuator at the analog input modulation port of the ITC 502 current driver. This is to ensure a more or less accurate 20 dB attenuation of the control signal since the ITC 502 input has an impedance of 10 kOhm.

  2779   Mon Jul 12 14:28:38 2021 aaronElectronicsLab Workno noisy pickoffs for PDH signals

We've been using T-junctions to pick off PDH control and error signals, but sometimes we should have a high impedance, floating buffer between our current control loop and noisy or grounded devices like the ADC or oscilloscopes. I've added an SR560 between the PDH error signal and control signal pickoff points, and also used the 'aux out' connector on the back of the LB servo box as the control signal monitor point. I terminated aux out into 50 Ohm, with a T to the SR560 high impedance input.

Changes to the previous configuration are highlighted in attachment 1.

Attachment 1: 321F64CD-6EDA-4E4F-B9D5-0C403286E2AF.jpeg
321F64CD-6EDA-4E4F-B9D5-0C403286E2AF.jpeg
  2782   Thu Jul 15 17:22:03 2021 aaronDailyProgressLab Worklab cleanup

[shruti, aaron]

We cleared out the desk drawers and the middle optics table today. This involved

  • sorting the papers in the draws into scratch paper / notes; manuals, datasheets, and MSDS; miscellaneous electronics diagrams and the like; papers and articles; black paper. We kept the manuals, datasheets, and MSDS, along with the papers and articles, and stored both in the small wooden cabinet along the S wall where we'd been keeping some books
  • Sorted the other materials (like cables, router, hard disks, other computer components, CDs, etc) into appropriately labeled clear plastic boxes, which we are storing under the workbench for now
  • Mounted the fiber breadboard box on the PSOMA rack, and put the associated connector panels inside the box
  • Decommissioned the cryo GeNS experiment
    • Gowned up and opened up the cryostat
    • Removed the Si wafer therein, and stored it in the desiccator cabinet
    • Detached the copper straps from the cold plate, and detached the wires coming from the electrical feedthrough at their kapton-wrapped pin connectors.
    • Wrapped the GeNS mount, including copper straps, periscope, substrate holder, ESD, schwarzschild, and the bottom of the cold plate in foil, and stored it in a clear plastic box. Also stored all in-vacuum screws, washers, and nuts in foil in the plastic box.
    • Removed the hot mirror from the cold shield and stored it in its original lens case in the optics cabinet
    • Closed up the cryostat and removed it from its mount. We stored the cryostat, the breadboard with an open center that it sits on, and its channel strut mounting hardware in the cage in the WB subbasement hallway.
    • Put the remaining channel strut materials making up the cryostat's mount with the rest of our channel strut hardware in cryo lab

We still need to clear the following heavier equipment from the desks. To move this equipment, we'll first need to sort through the miscellaneous objects on the workbench so we have somewhere to put everything. It will require at least two people to move the reference cavity safely.

  • reference cavity
  • gaston and spirou workstation computers, plus monitors and peripherals
  • stereo and speaker system

Other than that, we're ready for facilities to move out the desks and optics table. We should place an order for the new desks by tomorrow so they will arrive without too much awkward waiting.

  2783   Tue Jul 20 19:15:43 2021 aaronDailyProgressLab Workfibers inspection

I started moving our fiber components to the rack-mounted box. I inspected and cleaned the tip of the fibers for the 50-50 fiber beamsplitter. Will work on some photos through the viewer of the analog microscope.

We need an uncoated APC to uncoated PC fiber patch cable to send a beam to our FC 1611. We have a coated patch cable, but should only use that for launching to free space.

I also searched for an appropriate replacement o-ring for the cantilever cryostat. I found the drawings and manual from IR labs, but they don't mention the size of the o-ring, and I didn't find something suitable in our supply. I'll order a new one, along with the patch cables and some panel mount DB9 adapters. 

  2786   Thu Aug 5 19:36:43 2021 aaronLab InfrastructureLab Workpreparing for lab rearrangement

I continued preparing the PSOMA table and cryo lab for moving out the central optics table and 2 desks tomorrow:

  • Powered off lasers, wrapped and taped their cables to the PSOMA table
  • Powered off all electronics on the table and rack
  • Disconnected all cabling running between the PSOMA rack and PSOMA table, such that they are completely disconnected systems.
  • Moved the crane to the space between the cryo cavs table and the E wall of the lab
  • Removed the laser curtains and hung them on the crane
  • Moved the 80-20 components that were being stored in the lab into the hallway cage
  • Moved the power supplies from under the PSOMA table to under the workbench
  • Disconnected the pump and covered open ports with foil. Moved the pumping station onto the sink benchtop, and moved its box stand onto the liquid He cryostat stand.
  • Moved the chairs to along the N wall next to the cryo cavs table
  • disconnected pressurized N2 line and hung it along the cable rack on the N wall
  • Wrapped up the blue optical fiber (running from the cryo cavs table) on the sprinkler hose it's ziptied to
  • Turned off the cryo cavs laser drivers, PDH boxes, and OXCO; Acromag chassis; AI and AA chassis. Then, with the DC current at the Sorensens reading 0A, turned off the Sorensen supplies. Finally, disconnected the DC power strip for the PSOMA rack at the Sorensen, and wrapped up that cable into the PSOMA rack.
  • Began but did not complete removing or securing all loose objects on the PSOMA table

The SR560 on the PSOMA rack are still plugged in to a power strip connected to the wall, but that is the only remaining cable running from the PSOMA rack or table. I'll return tomorrow morning to finish securing and wrapping the PSOMA table. Other than that, should be ready to move.

  2788   Tue Aug 10 17:39:40 2021 aaronLab InfrastructureLab Workpreparing for lab rearrangement

Friday, 6 August

Facilities came to move out the cryo Q (central, rigid legs) optics table, and left us the legs. They also took the two desks from the lab. Lastly, they moved the PSOMA table to the center of the room and rotated it 90 degrees so its long axis runs EW. Afterwards, Shruti and I moved the PSOMA rack to the E end of the PSOMA table, directly across from the other two racks .

Tuesday, 10 August

  • set up new desks
  • installed gaston and spirou workstations on the desks
  • Began rerouting cables among the three electronics racks.
    • We would like to move the AI and AA chassis over to the cymac rack, to reduce the number of cables running between racks and get them away from the DC supplies. Has the added benefit of making them somewhat more accessible in the new configuration. Is there any obvious reason we would not want the Acromag, AI, or AA chassis on the backside of the cymac rack?
    • Continued labeling cables as we go
  • power on Sorensen, Acromag chassis for pumpdown measurement.
  • Removed plastic wrap from the PSOMA table
  • We should figure out what to do with the lHe cryostat. If it leaves the lab, it would be convenient to move the silicon / fiber / optoelectronics cabinet slightly south, to let us space out the desks and place the speakers along the N wall (and easier access for that cabinet).

Attachment 1 is a screenshot of the temperature and particle count trends over the last 4 weeks. I need to figure out how to add axis labels on ndscope... the units for both temprature channels are F, relative humidity is %, and all particle count channels are log(counts). There is a factor of 10-1000 excess particle counts around the time of our lab rearrangement, mostly affecting the larger particle sizes. Humidity also experienced a mild increase. The AD590 temperature channel drops off because I turned off its power supply to accommodate our rearrangement, and haven't yet turned it on again. The daily and weekly particle count fluctuations are interesting, presumably dictated by lab access.

Attachment 1: Screenshot_from_2021-08-10_19-01-13.png
Screenshot_from_2021-08-10_19-01-13.png
  2790   Wed Aug 11 16:09:29 2021 aaronLab InfrastructureLab Workpreparing for lab rearrangement

During the vacuum testing, I'm continuing some lab maintenance, mostly cleaning up and labeling cables on the electronics racks.

  2917   Tue May 24 15:54:52 2022 ranaLab InfrastructureLab Workgeneral cleanup
  2918   Wed May 25 10:32:19 2022 aaronLab InfrastructureLab Workgeneral cleanup

[jancarlo, aaron]

We did the following:

  • We moved the HEPA filter that doesn't fit from over the enclosure to under the table. We wrapped it in plastic, and placed it on sliders (used some unistrut brackets) for easy removal.
  • Jancarlo removed several unused cables from the PSOMA rack and stored them
  • We stored the LB box (aaron is going to continue laser locking with moku pro, following Shruti's latest log)
  • Jancarlo photographed the LB servo box and SR560s and will set up a repair or replacement
  • Jancarlo will identify some unused Sorensen supplies from the 40m, or order some if needed
  2924   Thu May 26 10:24:27 2022 aaronDailyProgressLab Workrealigning cavity

Found the cantilever with mirror in the silicon cabinet, and mounted it in the clamp. Also transferred MC1 (curved mirror) to the 45 degree mount to give us more clearance on the input coupling. Then, started to align the cavity.

  2926   Wed Jun 1 16:02:42 2022 aaronDailyProgressLab Workalignment

Spent 4 hours aligning today (mostly just chasing my tail) before breaking another cantilever.

  2927   Thu Jun 2 09:59:16 2022 aaronDailyProgressLab Workalignment

I took microscope photos of the mirror surface (attachment 1, 2)

I'm de-bonding the mirror following the procedure used previously. (attachment 3)

Attachment 1: Photo_on_6-2-22_at_09.54_#2.jpg
Photo_on_6-2-22_at_09.54_#2.jpg
Attachment 2: Photo_on_6-2-22_at_09.55.jpg
Photo_on_6-2-22_at_09.55.jpg
Attachment 3: IMG_2953.jpg
IMG_2953.jpg
  2928   Tue Jun 7 10:14:42 2022 shrutiDailyProgressLab Worknew cantilever clamped

I have de-bonded the mirror from the other cantilever also following this procedure re-using this setup. It took about 10 minutes or so to de-bond.

I saw that there were two cantilevers (possibly selected earlier by Aaron) left in the 'clean' part of our enclosure that looked good to bond the mirrors to.

  • I cleaned both sides using drag wiping with 100% 2-propanol, especially the outline of the window where the optic would be placed
  • I also used drag wiping on both the HR and AR surfaces of both mirrors.

[Rana, Shruti]

Then, with cryo varnish borrowed from QIL, we followed this procedure and bonded the AR surface of the mirror to the cantilever.

 

After roughly 3-4 hrs, the mirrors seemed to have bonded to the cantilever. I checked this by picking up the cantilever by holding the mirror edges with ceramic tipped tweezers. I clamped one of them and placed it roughly where it should be in the setup and stored the other one in a wafer case.

Images can be found here.

Rana: photos from my phone and somewhat processed here in the ligo.wbridge Google Photos account. I'm also attaching one showing that the second mirror we bonded is most likely cracked, rather than scratched as I previously thought. It still might be fine for in air testing.

 

 

Attachment 1: PXL_20220607_183717642.jpg
PXL_20220607_183717642.jpg
  Draft   Thu Jun 16 11:04:13 2022 shrutiDailyProgressLab Workalignment

Attachment 1 shows 4 composite posts that I placed around the cantilever for some minimal protection.

After aligning to see some resonances in the transmission and reflection, I turned off the teraxion laser and switched the fibers to send the light after South Rio laser->Faraday->EOM chain to the fiber launch to begin locking. Attachment 2 shows the reflected light (blue) and transmitted light (yellow) before I optimized the mode-matching further.

For attempting the locking, I am now just using the Laser Lock Box on the Moku:Pro. The error signal looks weird even after checking with multiple phase offsets. Not sure what's happening. (Attachment 3)

 

Attachment 1: fortress.pdf
fortress.pdf
Attachment 2: Screen_Shot_2022-06-16_at_11.10.56.png
Screen_Shot_2022-06-16_at_11.10.56.png
  2931   Thu Jun 16 14:28:32 2022 Peter, OjoLab InfrastructureLab WorkLab set up for clamp testing

Today we moved some of the mirrors and lenses on the back end of the table where the 630nm laser is. We wanted to prepare a space to be able to test the optical lever. We learned a bit about what the setup of a model cavity looks like within the lab. We were also introduced to some of the PDH locking and control systems.

it was said that we couldn't determine if the PSOMA cavity was locked to the 00 mode, or to a higher-order mode, so Shruti, Dr. Chris, Ojo, and Peter did a small bit of preparation to test the optical lever and see how it's aligned.

Next time, we plan on creating clamps of one of the cantilevers and setting up the photodiodes.

  2935   Mon Jun 27 15:44:53 2022 aaronDailyProgressLab Workimproving cavity mode matching

[shruti, aaron, ojo, peter]

  • We found the schematic of the LIGO current driver and saw that the input impedance for the current modulation path is 1 kOhm.
  • WIth the cavity locked, the power meter was measuring only 10s of nW where our CCD camera should monitor the transmitted light. The TRANS PD would have predicted several uW instead. We adjusted the transmission pickoff BS so its reflection was sending the full beam towards the camera, and moved the camera around until we could see the transmitted beam. Peter scanned the temperature while sweeping the current modulation at 1 Hz, eventually locking to a bright 00 mode.
  • We monitored the ratio of transmitted to reflected light while adjusting the input alignment to improve the modematching
  • Shruti modified the Pomona box to be impedance matched to the custom driver, and moved the pole to ~50 Hz and the zero to ~400 Hz. We measured the transfer function of the Pomona box.
  • We used nds to measure the power spectrum of the PDH control and error signals, as well as the RMS power. In attachment 2, the reference traces are with no Pomona box boost and the measurement traces are with the boost. We noticed a few peaks below 100 Hz in the "non-boosted" PDH error signal were absent in the error signal with boost.

 

Attachment 2 is the transfer function of the updated Pomona box and was measured with 1 kOhm in parallel with the output (assuming the current driver has a 1 kOhm input impedance which was what it seemed from the dcc data sheet)

Attachment 1: 220627_boosted.png
220627_boosted.png
Attachment 2: MokuFrequencyResponseAnalyzerData_20220627_174435_Screenshot.png
MokuFrequencyResponseAnalyzerData_20220627_174435_Screenshot.png
  2938   Tue Jun 28 14:38:23 2022 shrutiDailyProgressLab Workcharacterizing pdh loop

I tried measuring some open loop transfer functions while keeping the cavity locked without slow control.

Attachment 1

The red line is the measured open loop TF dividing the PDH/LB error mon after injecting a small signal at the -B port of the LB1005 controller. There seems to be a kink in the measured curve at ~ 1 kHz so we would have to repeat this measurement.

The gain being used is nearly at the limit of what the LB1005 can provide but the UGF is only a few kHz. Adding the pomona filter with design in Attachment 2 required us to increase the servo gain by ~18 dB to recover the UGF we had earlier. But seems like we could only increase it by ~ 6 dB with the knob.

How can we increase the gain further?

While chatting with Aaron, we realized since new cables were added, the PDH demod phase might not be optimized and could be the cause of the lower open loop gain.

Attachment 2: the updated pomona filter for 1 kOhm output impedance

  • The blue curves in Attachment 2 shows Vout/Vin for the circuit in Attachment 3
  • The vertical dashed lines in the the magnitude (of Attachment 2) are the zero and pole one would expect for high impedance output as calculated by pole=1 / (2*pi*R1*C1) and zero=1/(2*pi*R2*C1)
Attachment 1: LoopTFs_wpomona_knob9_20220628.pdf
LoopTFs_wpomona_knob9_20220628.pdf
Attachment 2: 20220628_FilterTF.pdf
20220628_FilterTF.pdf
Attachment 3: IMG_F1C22B0747F7-1.jpeg
IMG_F1C22B0747F7-1.jpeg
  2939   Thu Jun 30 10:35:55 2022 shrutiDailyProgressLab Workcharacterizing pdh loop

[aaron, shruti]

 

  • Estimating that the cavity pole is around 100 kHz, I played with the PI corner and locked the cavity with the corner at 100 kHz in hope that that would increase our UGF. The transmitted beam always looked very dim on the monitor in this configuration so we switched back to a pure integrator
  • We're also adjusting the cable lengths to optimize the PDH signal
  • Added a lambda/2 filter to make the beam into the cavity s-polarized. Added the lambda/2 followed by a PBS, rotated the polarization to maximize the power of reflected light, then removed the PBS.
  2940   Thu Jun 30 19:33:16 2022 ranaDailyProgressLab Workcharacterizing pdh loop

How to increase gain for this loop? What we want is an overall gain increase wihtout any shaping.

  1. What is the RF modulation depth? it should be ~0.2-0.4 radians. This should be measured, not inferred from the data sheets.
  2. What is the power level on the reflected PD, when the cavity is locked?
  3. What is the mode matching fraction?
  4. What is the AC transimpedance of the RFPD?

We are missing a factor of ~100x in the gain here, so most likely there is something broken. The RF phase most likely can give us a factor of a few if we're way off.

It would be good to see the modeled servo loop Bode plot on this plot (modeled using knowledge of all the pieces, rather than a fit).

  2942   Thu Jul 7 11:32:25 2022 PeterNotesLab WorkMeasuring cavity parameters

I just spent about an hour taking measurements of all the distances of the optical components in the PSOMA cavity. ie, the distance from the laser to lens1, distance from lens1 to SM1, SM1t to WP, and so on. I was just using a ruler.  Overall, I got some fairly accurate measurements. Kind of hard to measure with the setup since I didn't want to actually get close and touch anything, and I succeeded since nothing was touched. This data will be useful for me in creating a working model of the cavity in FINESSE.

Shruti and I then decided to try and measure the beam profile. However, the computer died on us before we could get it working. Even before then, we were experiencing some problems in actually collecting that data. The computer was reading the beam, but it wasn't giving us any output. We'll try again after lunch most likely.

Until then I'm going to get this code of the cavity parameters working. Now that I have the distances, I can create a model of the mode matching tolerances of this cavity with hopefully some accurate data.

ELOG V3.1.3-