40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Authorup Type Category Subject
  2537   Fri Jul 17 13:15:03 2020 aaronUpdateLab WorkReopening cryo lab

TLDR: I sealed the leaks around the HEPA filter. I did an inventory of PPE and cleaning supplies in cryo, and separated two sets of personal PPE for Shruti and myself from the common supply. I did not receive PPE or cleaning supplies from Downs or 40m, but have inquired after both. Any anticipated work not explicitly mentioned here was not done; I tried to take care, but still strongly suggest that Shruti wipe down anything I placed in your personal supplies, just in case.

Next steps: See prior elog


After clearing the temperature check at home, still showing no symptoms, and starting the daily log in the reporting app, I head to West Bridge.

I entered the lab at 13:10 PT, using the N (olive walk) entrance to W Bridge. I am wearing a disposable mask, applied hand sanitizer on entering the lab, and don nitrile gloves. I locate the ISO and Kim wipes and wipe down

  • personal devices
  • glasses
  • keyboard, mouse, spirou workstation
  • door handles
  • Orange-brown lab chair
  • Common cabinet handles
  • label maker

Existing PPE and cleaning supplies in cryo

I located the following in the cryo lab, and am storing all PPE in the staging area at the entrance.

  • 4x laser glasses suitable for 1550nm. 2 are over-glasses, 2 are not, and I've labeled the glasses and storage cubby for myself and Shruti to have one of each.
  • 4x laser glasses for 1064. 2 are labeled '40m' and will be placed clean in the outbox for pickup with the circuit, the other 2 are also in labeled cubbies.
  • 1 pair of lN2 safety googles, 1 pair of ordinary sunglasses. These are not in regular use, and can be used occasionally with proper cleaning.
  • Limited supply of blue shoe covers (1 package)
  • 56 boxes of small dry Kim wipes, 4 box supply of large dry Kim wipes
  • 1 box of large nitrile gloves, nearly depleted
  • 2 Kimtech lens cleaning stations (34623; need to check whether this is just anti fog or also EPA approved sanitizing spray)
  • Various Tyvek coveralls (PN IC 182 BWH SM 00250C) size small to XL
  • 2 polyester lab coats (M, L)
  • Variety of Single-wrapped latex gloves, size 7, 8, 8.5, 9, 
  • hair nets
  • sleeve covers
  • 1 Willson face shield
  • disposable frocks size S 
  • limited supply of shop wipes
  • 1 package pre-wetted polyester wipes
  • dust catcher floor mats

Personal tools and PPE

Any tool I used that we have multiple copies of, I labeled "[aaron/shruti]" and set aside one copy for me and one for Shruti. My tools are on the blue cart holding Spirou. Shruti's are on the tan cart formerly holding screws and power supples (which I moved onto the remaining cart, the work bench, and the middle optics bench). Personal toolkit currently includes:

  • scissors
  • large flat head screwdriver
  • glasses cleaning station
  • dry kim wipes
  • small IPA spritz bottle 

Personal PPE are in clear bins labeled "Shruti" or "Aaron" and with the box contents. Currently each set includes

  • 2 disposable (but multi use) frocks
  • 2 disposable (but multi use) coveralls
  • 1 washable lab coat (where to launder?)
  • several pairs of AccuTech ultra-clean latex gloves
  • several hair nets
  • several blue shoe covers
  • several white sleeve covers

The remaining PPE are in clear boxes near the entrance labeled "common" and with the box contents. Extra AccuTech gloves and a few more coveralls are on the shelf below the HEPA filter.

Any tool with only one copy, I am noting here for a future order. I sanitized these tools before and after use. Common tools will remain in the tall blue Crafsman tool box.

  • label maker. The batteries were badly corroded (we usually run on power supply), I set them aside for disposal.
  • ladder

HEPA filter

The model of the HEPA filter is not visible from the exterior, and I will have to look up its cleaning schedule. The tape sealing the edges of the filter does not adhere to the textured paint surrounding part of the filter [attachment 1] . The smooth paint on the far wall appears to support adequate adhesion. To create a seal on the textured surface, I first cleared the supplies from the shelf under the filter and pealed back the non-adhering tape. I applied rubber cement to the sticky side of the tape, and held the tape in position for drying using the small boxes of Kim wipes from before. I applied rubber cement along the entire edge wherever there was textured paint, but not on the region with smooth paint. Air flow through the filter was noticeably increased following this procedure and seal was intact after a few hours, though I did not make a quantitative measurement. 

Stopped by Downs

at 1500 I exited the lab to use the restroom, eat, and pick up PPE from Downs 318. I swapped gloves on exit, and resanitized my hands after using the restroom in W Bridge basement, which is designated for our lab's use. After eating, I entered Downs and took the elevator to the 3rd floor, but was not able to access room 318 for PPE. I emailed Chub and Calum (listed contacts for Thomas lab) to coordinate a pickup at a later date. Specifically, I am requesting:

  • Nitrile gloves, M and S
  • 4 cloth face coverings, 2 for me and 2 for Shruti
  • Cleanroom masks (can also obtain from 40m PPE supply)
  • Beard covers (can also obtain from 40m PPE)
  • IPA wipes (some available in 40m supply)
  • disposable frocks size M (available at 40m)
  • 2x Disinfectant spray can
  • 2x hand sanitizer
  • 2x face shield
  • 2x no touch tools
  • 2x door adapter
  • 2x shop safety glasses
  • Signage
  • Borrow air flow meter if available 
  • anti-fog disinfecting wipes for glasses (is this the same as the Kimtech station?)


  • I found one function generator (SRS DS345) plugged into a power strip that was not connected to power. I've plugged it in to the wall and labelled it "check battery"


At 17:15, I begin wiping down the common tools and surfaces I used and exit at 17:25, upon which I disinfect hands again.

Attachment 1: tape_before.pdf
Attachment 2: glasses.pdf
  2540   Fri Jul 24 15:59:12 2020 aaronUpdateLab Workcryo open

Notice of lab entry


Date of entry: 23 July 2020
time of entry:  15:15 PT
time of exit:    18:09 PT

Purpose: finish up the steps outlined above (2533)

[note: date is correct, I needed to remake the entries for July 23 but the content of 2541 is nearly identical. I had a backup.]

  2541   Fri Jul 24 16:12:13 2020 aaronUpdateLab Workcryo open

entered W Bridge 264

I stopped by my office (W Bridge 364E) to pick up the new workstation computer and a mini monitor that might be handy. Stayed < 15 min and wore fresh gloves, mask, etc; also recorded entry by door.

I entered the lab around 3:15pm and wiped down the common surfaces. I sanitized and sorted my set of PPE from the box Liz dropped off -- thank you!

We should try not to bring cardboard Into the lab, and remove any cardboard we find. I got rid of a couple boxes.

lab temperature is high

The thermostat is doing its usual thing. It is set to 'cool,' but despite the temperature reading 71.2 F at the thermostat, the temperature at the particle counter is 80F and it feels warm. When I try to lower the set point, the thermostat requests a password. I found online that the default password for is 9995. The thermostat seems to accept the password but won't let me change the setpoint.

The rubber cement at one corner of the HEPA filter delaminated, but the edge held by the kim wipes set in place. I reapplied glue and fixed the tape more securely, and noticed improved air flow through the filter again. The lab temperature also improved a bit -- the leak seems directs cold air down to the floor, while the filter sends cool air across the top of the room.

misc reopening steps

These cover most of the recommended reopening steps. I'll do some general cleaning and organization, and make some new signage, then will call it 'reopen.' 

  • ran the sink hot and cold for about 10 min. There are no noticeable leaks or dampness under the sink, along the edges of the lab, or in any of the major cabinets in the lab.
  • Valved off the cryo Q vacuum and turned off the pump. Pressure reached 2e-3 torr in ~3 hours
  • strain relieved cables of spirou workstation, moved the station, ethernet, etc closer to PSOMA electronics rack
  • checked level of compressed He (1900 psi) and N2 (we don't have a cylinder). I will coordinate with Chub to get an N2 delivery
  • Added isopropyl, methanol, other solvents to the PSOMA inventory
  • Confirmed that our fire extinguisher still has pressure. Where is our eye wash and emergency shower station?  There's one on the basement level, is there one in the subbasement?
  • Not sure about sprinklers, gas, and vacuum utilities. I checked the utility with a yellow valve at NE corner of the lab, but opening the valve releases neither gas nor vacuum. I did not touch the sprinkler system, and did not test the compressed gas tubing (such as for the optics benches).
  • Laser 'in use' lkight at the lab entrance is functioning.
  • Checked that the hot plate (1) and variac cables were not under stress or damaged

exit lab Thu Jul 23 18:09:38 2020

  2542   Sun Jul 26 20:37:50 2020 aaronUpdate  

Notice of lab entry


Date of entry: 27 July 2020
time of entry:  11:30 
time of exit:    19:00


Purpose: PSOMA hardware inventory, find out what we can turn on

  2543   Mon Jul 27 12:11:49 2020 aaronUpdateLab WorkSimplifying W optic bench

PSOMA hardware inventory

I located the materials for stage 1 PSOMA on the West optics table. I recorded what we have in the hardware inventory, and what we don't have is flagged for purchase. I start by cleaning up the electronics rack, removing anything I think is not in use.

Electronics rack

  • Both laser current drivers are D1500207
  • The E laser has a TED 200 C temp controller. The W laser is not plugged in to TEC, but there is a spare ITC 502 combination controller on the rack, and cryo cavs has a additional ITC 510.
  • There are three universal PDH servo boxes on the W rack: 1x D0901351 and 2x D1700219-v1. All of the boxes need lids and proper rack mount hardware.
    • Innards
      • Inside the *1351, the board matches the front panel DCC number (serial number 1437)
      • Both the *0219 have matching boards: D1700192-v2, D1700195-v2, D1799182-v2, D1700131-v2
  • Power supplies
    • The +- 15V power strip is currently unplugged. I don't see a low noise DC supply on this rack, but there is a Tenma 72-6615 on the ground. The closed-ring connector of the power strip is incompatible with this supply, so likely it was powered off of something else.
    • There's a NewFocus 1901 +- 15V supply on the W table itself. I think this should be located not on the table? The outputs are 0.1 A max to banana, plus 2x 0.3A max to a coax cable. The NewFocus was only supplying the PDs on the table. 
    • Cryo cavs has a dedicated rack for its power supplies (2x Sorensen DCS33-33E), separated from the laser control and PDH electronics. Is this an important choice, and should we also move our power supplies?
    • On the bottom of the rack, there's a Mech-Tronics NIM power supply. Seems out of use, only a PD power supply and readout board is plugged in, but this has no corresponding PD. 
    • I found on the elog that Chris moved the two Sorensens from the cryo cantilevers (W) rack to the cryoaux (central, rolling) rack after the supplies Johannes bought in 2017 died (fans not running). Do these usually die right after their 2 year warranty expires, or were we especially hard on them?
      • sidenote, great to see a potential solution to cryo lab timing woes, and that the overheated Sorensens were causing cominaux hard drive failures. Thanks Chris!
      • I've added 2x Sorensen supplies to our purchase list for PSOMA
    • For now, I moved all existing power supplies onto the electronics rack, and power the strip with the Tenma. In the future, we can discuss a remote location for power supplies, and will buy 2x additional Sorensens.
  • Misc
    • a bunch of old and open circuit boards, in cases compatible with the NIM supply. One power amp II; one PDH2 servo board (D1100996); 2 channel low noise amplifier (contains D1101396-v2 and another hand made board); a general filter board claiming to be from the gyro experiment. 
    • There were a few loose minicircuits components connected to the OCXO preamp (D1500064). These were providing 33.59 and 32.7 MHz modulation to Zach's experiments. I removed these from the preamp so we can give them a more permanent box later.

W optics bench

  • vacuum pump
    • I don't see the pumping station that used to be by the W optics bench. I don't remember using it elsewhere, and don't find any elog mentioning it being borrowed or moved. Has anyone seen this pump? It's one of the HiCube all-in-ones; it should have LIGO property tag C21832.
    • Similarly, what happened to the IR labs cryostat that housed the cantilever Q measurement (property tag)? I see maybe the glint of a cantilever in the short gryo vacuum can, and I have the cantilever Q HV driver and feedthrough, but no cryostat.
  • Photodiodes
    • PDA50B (Ge, 800-1800 nm)
    • 2x PDA255
    • Found 2 loose (unmounted) photodiodes wrapped in foil near the "optical contact razorblade test" setup (SE corner of W table).
    • NewFocus 1811, 1611
    • 1 home brewed QPD and breakout board, (PN on the circuit board is 10-00146 rev 1)
  • Put away or onto the workbench any loose optics, unused optomechanics, and most cables. Anything that wasn't a stock part I placed in a clear plastic box labeled 'Cryo Cantilevers' in the projects cabinet (2-part wooden cabinet on S wall). Stock parts went into the respective optics cabinets.


  • The lab temperature is still way too high. The temperature at the particle counter is reading 78, the thermostat still reads 71 F. The filter is not leaking substantially.j
  • Got the speaker working -- there was an aux adapter in the headphone port, so system was confused
  • Raymond requested a CF16 blank. I couldn't find one, but gave him a CF40-to-CF25 adapter that had a CF25 blank epoxied onto it, along with a CF16 to CF40 adapter and some gaskets. Here was the disinfection procedure for sending these items to QIL:
    1. Found a large plastic bag and disinfected inside and out with Phenomenal (TM) spray
    2. Disinfected the unpackaged UHV components with 70% isopropyl alcohol and a Kim wipe, wrapped them in foil, and placed in the disinfected bag
    3. Disinfect the outside of the bag with Phenomenal spray and leave outside the door to cryo for same-day pickup.
  • noted that pressure in cryo Q vacuum is 24 utorr after about a day valved off
  • Emailed Jordan and Liz about anemometer, to measure air flow in cryo. If we can compute the time for air to circulate through the cryo lab, we can reduce the length of time between lab entries (currently Shruti and I are leaving 1 day between our lab uses). 
  • Starting piling up seemingly unused components from W table onto the S workbench. These need a new home.
  • Found some historical documents, sticky notes from Zach. Took photos of these just in case (attached, later) and placed along with the miscellany on the workbench.
  • Checked with other W Bridge lab users before entering EE shop at 3:30pm. Disinfected surfaces I touched before and after use. I retrieved 3x 9V rechargeable batteries for the cryo lab multimeters.
  • Found a cardboard boxed fiber polarization controller (FPC032), which I placed in the NW optics cabinet sans box. Is this safe for storage (attachment 3)? What about things like Kim wipes, are those an acceptable amount of cardboard, or should they be eliminated?
  • Moved any cantilevers, etc into the silicon storage cabinet (NW corner cabinet)
  2544   Tue Jul 28 13:33:06 2020 aaronUpdateLab WorkRio laser

Notice of lab entry


Date of entry: 28 July 2020
time of entry:  15:00 
time of exit:    19:30
Purpose: Turn on the Rio laser, find what we need for beam profiling, do some cleaning (mop, putting away stuff from the workbenches, etc)
  2545   Tue Jul 28 16:13:56 2020 aaronUpdateLab WorkAir flow measurement


  • I propose we continue scheduling cryo lab use with one individual using the lab per day, and announcing who will be in lab the day before.
    • If needed, this analysis suggests we could schedule two people to use the lab during the same day, but not at the same time. (of course, we are not yet cleared for shared use of the lab)
  • Use the air scrubber near the workstations, or wherever in the lab has stagnant air and prolonged use
  • Increase air circulation in the lab
    • I can order fans this week.
    • Can we open an additional port for air flow out (and possibly in) to the lab? What's behind the old cryo access in the NW corner, could we put a vent for out flow?
    • Change the HEPA filter
  • Before returning the anemometer, perhaps should measure air flow in the interior of the lab.
  • Check out the new cryo lab group and repo(s) on the github!

Cryo lab air flow

Liz dropped off an air scrubber (Medify Airx MA-40) and an anemometer (Digi-sense 20250-15) today. I'm using the instructions on the DCC to measure the air flow and assess the occupancy limits of the cryo lab. I calculate an acceptable amount of time between lab uses, and for two people to occupy the cryo lab simultaneously. For these calculations, I use a conservative threshold of P<1% for the acceptable probability that a second person becomes infected, given one infected lab occupant who sheds virus at 10 nL/min. I measured the dimensions of the lab at about 30x20x10' (l, w, h), for a 6000 ft^3 volume. I expect that's a high estimate, as it doesn't account for things like the awkward geometry of the staircase, volume of lab equipment, or stagnant air inside cabinets.

I measured the air flow at 20 points in a grid covering the surface of the HEPA filter. I also confirmed that there is no measurable air flow into the lab other than at the HEPA filter (eg, at the hole in the ceiling in the NW corner of the lab, or where the RF timing sígnal is sent through wall to Crackle lab). The average air flow through the HEPA filter is 200 CFM (cubic ft / min).
The flow is highest near the edges of the filter--does this indicate it is nearing the end of its life (it's been at least a year since replacement)? The flow is mostly above 200 CFM, but varies from 100-300 CFM across position and time.


The first row is the minimum number of minutes to wait between when a (presumably infected) person exits the lab, and when a (presumably uninfected) person can enter the lab to maintain a <1% probability of new infection through aerosolized spread. The second row is the maximum number of person-hours the second and further (presumably uninfected) users can collectively spend in the lab with one presumably infected user, while still keeping a <1% probability of observing any areosolized spread. I don't have Spirou online currently, but I'll eventually put the calculation notebook in a shared folder accessible to the new cryo lab environment repo. Update: it's here.
Configuration cloth mask, no scrubber cloth mask, with scrubber N95+, no scrubber N95+,with Scrubber 
Minimum time between occupants (min) 17 7 0 0
Maximum person-hours of shared occupancy (person-hour) 0.004 0.008 0.08 0.15

These results are consistent with what I see for similar types of rooms in the LIGO spreadsheet.

Under an air flow model assuming perfect distribution of air from HVAC and HEPA scrubber throughout the lab, and very conservative requirements for probability of spreading COVID assuming a single lab user is infected, 

  1. Within 6 minutes of an infected user exiting lab, an uninfected person can enter and expect a tolerably low concentration of aerosolized virus.
  2. Within 10 minutes of one infected and one uninfected person working in the lab 6'+ apart with N95 or better masks, the viral load to an uninfected at-risk person may be intolerably high

Furthermore, the air in the lab Is not perfectly distributed. The air intake is several feet from the outflow, both near the door. The primary heat sources are the electronics racks along the N and NW sides of the room. The gradient from 71.1 F at the thermostat to 78 F at the cryocavs rack is uncomfortable to work in and bad for the electronics and optics. It's also too stagnant for the viral load conditions assumed in Evans P2000189 to apply. 

We are not currently cleared for 2+ people to use the lab. This analysis suggests to me that before doing so, we should improve the air flow conditions in the lab. And, even under optimal conditions we may minimize the total time with multiple people in the lab simultaneously.

Rio laser

I disconnected the oscillator, PDH boxes, and laser drivers from the power strip, and powered the strip with the Tenma supply. I had the ground and negative pins switched at first, careful of this -- ground is black, negative is green on this cable.

I plugged in the electronics, but only turned on DC power to the laser driver. I just left them on long enough to confirm a bright green (on viewcard) beam spot for both lasers -- we're in business!

Turned off the lasers, disinfected the common surfaces and objects.

PS, the anti-fog wipes work wonders. My goggles went from fogging in seconds to no fog at all.

  2550   Wed Aug 5 19:03:56 2020 aaronUpdateLab WorkNotice of lab entry

Notice of lab entry

Date of entry: 7 Aug 2020
time of entry:  11:00 
time of exit:   
edit: postponed this work from 6 Aug to 7 Aug.

Purpose: Measure optical table dimensions, start to assess what we need for an enclosure. Set up EOM/EOAM to take some transfer functions. Set up realtime model. Figure out why particle counter isn't logging to frames. Turn on the HEPA for cryo cavs table.

  2551   Fri Aug 7 11:35:09 2020 aaronUpdateLab Worklab work

Entered the lab at 11:00 am. The lab is far too hot (78F) and humid (45%)! 

Inventoried available photodiodes in the cryo lab, on the PSOMA wiki.

Fri Aug 7 12:55:53 2020
Facilities came to check the fire alarm. I let them in with shoe covers, they held a magnet up to the fire alarm and left. Total operation took less than 5 min.
[lunch and a couple meetings 1 - 3]

Pretty tired honestly, I submitted an order for a few things we want in the lab, such as:

  • 2x "ultra quiet" fans to circulate air
  • longer ethernet cable for reaching far end of PSOMA table
  • headset web cam so we can take video while doing lab activities
  • more plastic storage bins
  • food and water for our emergency kit

The PSOMA optics table is from TMC vibration control (TMC 784-29701-01). I sent them an inquiry for the datasheet, and also asked whether they sell clean enclosures or have application notes that might help us put one together. Also talked with Arian Jadbabaie a bit about the Hutzler lab enclosures, and got some photos.

Exit ~430 pm

  2552   Mon Aug 17 15:10:58 2020 aaronDailyProgressLab WorkNotice of lab entry

Notice of lab entry

Date of entry: 17 Aug 2020
time of entry: 3:30pm
time of exit:   
Purpose: Make sure unnecessary electronics in the lab are off, due to the CA energy Flex Alert. Take some photos of cryo cavities enclosure and filter to assist with new enclosure design.
  2553   Mon Aug 17 15:52:13 2020 aaronDailyProgressLab WorkNotice of lab entry

Measurements around table

  • Clearance of lights -- 100''
  • clearance of  beam -- 105''
  • distance between lights -- 6'
  • there's also a sprinkler head a few inches lower than the lights
  • distance from top of table to ground -- 35''
  • distance from bottom of table to ground -- 24''
  • distance between sprinklers -- 8'

Could probably move the table a few inches from the wall and make use of the space between the lights for the enclosure. There also isn't much room in the back corner in the NS direction, and we may want to shift in either direction. Orientation seems as good as it could be. The ceiling above PSOMA is lower than above cryo cavs.
Will mark up photos and post.


Attachment 1: Ceiling_lookingSouth.jpeg
Attachment 2: Ceiling_lookingNorth.jpeg
Attachment 3: Clearance.jpeg
  2554   Tue Aug 18 15:05:33 2020 aaronUpdateLab Worknotice of lab entry

Notice of lab entry

Date of entry: 18 Aug 2020
time of entry: 2pm
time of exit:   11pm

Purpose: Inventory lens supply, identify some combination of optics that will let us mode match to our ring cavity. Picked up some books on silicon from the library.

  2555   Tue Aug 18 21:35:49 2020 aaronUpdateLab Worknotice of lab entry
I'm taking inventory of our optics supply, in between figuring out what's wrong with the temperature log channels.

The inventory is in Clickup, which is a new organizational tool I'm trying out. There' an easy csv export, so I can get it elsewhere if/when we want. We have a wide variety of lenses:

Focal length (mm) 25.4 38.1 100 103.22 154.82 200 225 250 258.04 309.65 412.86 500 850
Quantity @ 1550nm 1 4 2 7 2 2 6 2 1 3 12 1 2

I found fewer curved mirrors, but there were a couple.

Steps I took for the temperature sensor:

1. Tried to see what's the temperature by reading the current temperature in ndscope or dataviewer. In dataviewer, go to 'Signal' tab, and enter the channel name or find it on the list of slow channels. For ndscope...

nsdscope X1:AUX-LAB_TEMP_F 

No data appears on either. I restart cymac1, which seemed frozen, but still nothing.

2. What's going on with these channels?

$ caget X1:AUX-LAB_TEMP_F
X1:AUX-LAB_TEMP_F     -459.7
$ caget X1:AUX-LAB_TEMP_K
X1:AUX-LAB_TEMP_K     -0.0166677

Looks like the channel is reading zero.

3. I traced the cable from the particle counter and found that it sends data to cominaux, the common auxiliary machine for the lab.

ssh cominauxThat's a little surprising to me, because
cd ~/services/modbusIOC/
less CRYOXT.db

This is the database file that defines the channels on cominaux. I search for 'LAB_TEMP_F' and find the epics record for the temperature channels. The epics records are all "calc" records, and the temperature in Kelvin is taken from X1:AUX-ACROXT_AI_15. This corresponds to channel 15 of the acromag slow ADC.

$ caget X1:AUX-ACROXT_AI_15
X1:AUX-ACROXT_AI_15     -0.0003333

 That's starting to make sense, the cable from the particle counter didn't go to the acromag ADC. Starting from the ADC channel 15, I traced the cable back to what used to be the AD590 temperature transducer.

4. Where did the IC temperature sensor go? Searching the elog and my dusty memory... neither readily recalls where it went. Let's get another one, they are cheap and easy to use.

  2556   Wed Aug 19 12:11:47 2020 aaronUpdateLab WorkNotice of entry

Notice of lab entry

Date of entry: 18 Aug 2020

time of entry: 12pm
time of exit:  
Purpose: Identify some combination of optics that will let us mode match to our ring cavity, set up PDH locking with the existing ~33 MHz modulation.
  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.

  2560   Tue Aug 25 13:23:49 2020 aaronThings to BuyGeneralcryo lab inventory

I started a cryo lab inventory that is separate from the PSOMA hardware inventory, and intended for stock items in the lab (optics, electronics, clamps, general safety and cleaning supplies, etc). It will be a work in progress. Both are accessible to anyone logged in to google drive with their ligo.org credentials.

Both are also linked on the PSOMA project wiki.

  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.


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.
  2563   Thu Aug 27 13:24:30 2020 aaronLab Infrastructurestuff happenslocked out of optomechanics cabinet

Not sure how, but none of the drawers of the blue optomechanics cabinet are opening. I don't have a key. Here's what happened

  1. I closed one drawer ("A") and opened the drawer below it ("B")
  2. Closed B
  3. Opened A and B simultaneously; I could not open only B, only A and B together. Close A and B.
  4. Open both A and B. Close only A.
  5. Close B
  6. None of the drawers now open, even A and B together. seems locked

Found someone who's had this problem before, might give it a try...


This worked, I used the metal meter stick to unlock the drawer.

[Stephen's updates]

--> note that link formatting breaks link for me, so here it is - https://www.practicalmachinist.com/vb/general/help-my-lista-locked-me-out-how-do-i-open-201606/

--> wrote up a similar experience with additional detail ENG_Labs/260

  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
  2567   Wed Sep 2 16:46:39 2020 aaronThings to BuyDrawingsdimension-full optical layout

I updated the stage 1/2 optical layout to be more detailed after getting a sense of the sizes of things again last week. Even though this isn't how the table is currently set up, it might be good to accommodate future vacuum chambers in our earlier designs to minimize how much we need to move and realign optics. 

  • just for convenience, I gave all of the vacuum chambers the footprint of the gyroscope vacuum chambers. I chose this footprint rather than the cantilever cavity cryostat footprint to allow 45 deg aoi on the mach zehnder BSs (the cryostat windows are all parallel)
  • The chamber containing the output BS and BHD is cramped. If these all need to be in the same vacuum, we should get a larger vacuum; if the BHD and LO path can be moved to air that works too.
  • If output BS chamber is larger and input MMT allows, the entire MZ can be shifted to the right (north). 
  • Picked off LO from input BS AR surface
  • Need additional mode matching lenses into some of the photodiodes -- certainly into PL_RFPD, but I think also into the other PDs?
  • The beam to TRANS_DCPD is probably geometrically unphysical. 
  • The cavity length is limited by the size of the cryostat.
  • Perhaps want free-space EOM, EOAM, Faraday isolator?
  • Not sure I've dumped all beams properly, for example the reflection from BHD_PD1 and from BHD_BS AR surface.

I will update the PSOMA hardware inventory tomorrow to reflect the additional details in the new drawing. The updated diagram is available on git LFS, and the hardware inventory now reflects the diagram up through stage 1.

Attachment 1: psoma_stage2.pdf
  2568   Thu Sep 10 10:21:34 2020 aaronLab InfrastructureHVACHEPA filters for PSOMA enclosure

Yesterday into today, I've been shopping for laminar flow HEPA fan filter modules for the PSOMA optical enclosure. I didn't find a lot of LIGO documentation listing specific filters, but here's what I've found online with some downselection on 'low vibration / high filter quality'. Please let me know If there's a company we often use, or if you can help direct this search at all. 

Another consideration is flow rate relative to our volume. I can do this calculation, but what is the particle density (eg at 0.3 um) we want to achieve inside the enclosure? I realize that I never got the particle counter recording despite it being on my list, so I'll try to do that remotely today. We need to know the ambient particle count and the clean volume in the enclosure.


Part number / name




Link for info


Terra Universal Smart Whisperflow Fan Filter Unit $1,111 HEPA (H10-100k) 40 dB @ 90 ft/min velocity @ face datasheet, product page The 'Smart' model has 9dB less noise than the standard, but costs about $500 more. Also comes in 'low profile' version.
Clean Air Products CAP118   HEPA -- product page requested quote
Thomas Scientific Fan filter module, "low noise" $1,760 HEPA   product page  
Price Industries LFDC series laminar flow diffusers       product page, datasheet  
Envirco Mac 10 original     51 dBA @ 90 FPM datasheet referenced in T2000382
A-J MFG SSLFHFD-FP "criti-clean" fan filter   HEPA 45dBA @ 90 FPM product page claims to be the lowest-height unit on the market (13.7''). The RFQ page looked fishy though, so I held off.
FungiFun (website)       link lists a number of other filter suppliers, by country

*all prices listed here are from publicly available pages

  2570   Tue Sep 22 21:30:07 2020 aaronDailyProgressLab Worklab entry, supplies

notice of lab entry

Tue Sep 22 21:33:30 2020


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

  2572   Tue Sep 29 11:00:53 2020 aaronComputingSimulationModeringer Simulation

Beautiful! Want to push this to the repo under git large file storage?


The step function represents the excitation of the sample. Ideally, it would excite to the setpoint and stay there but for some reason, it is jumping way past the point before returning. By messing with the gain and the frequency of the low pass filter I could get a variety of results the best is shown below at 50 gain and 40 rad/s.

The overshoot is interesting! To understand the loop shaping, I suggest checking out Gardner's Phaselock Techniques or Astrom and Murray's Feedback SystemsThey both have sections on optimal PID controller design (at least Astrom and Murray do). You can make a pole-zero plot to help choose the location of poles and zeros in your loop shaping filter (the discrete zero-pole TF we added, after the gain).


  2578   Wed Oct 28 18:10:27 2020 aaronNoise HuntingLaser

Lab entry

in: Wed Oct 28 18:11:00 2020
out: Wed Oct 28 21:05:58 2020

E laser noise

  • Moved the Newfocus 1611 from W path cryo cantilevers transmission, to just after the PSOMA beam launch.
    • nominal AC gain: 700 V/A
    • nominal DC gain: 10 kV/A
    • output impedance: 50 Ohm
    • Max input power: 1 mW DC (10 mW CW)
  • Measuring the following spectra across the PD band (~30kHz-1GHz) by connecting the 1611 AC output directly to an HP 8560E (50 Ohm input). I'm monitoring DC with TDS3024B oscilloscope (1 MOhm input).
    • dark current
    • free running E path laser intensity noise

Optical layout: beam launch -> lambda/2 -> steering mirrors -> lens 1 -> ND 0.6 -> lens 2 -> PD 1611

There is only a 12 VDC power supply compatible with the 1611 power port, but the PD requires +- 15V. Surely there's one somewhere. Perhaps this is why I observe only -6 V on the DC mon with 1mW input power at 1550nm (checked against the Thorlabs S122C; I expected -10V). Maybe the beam is too large.

  2580   Tue Nov 17 14:56:06 2020 aaronDailyProgressGenerallab entry

I entered the lab somewhat before Tue Nov 17 14:56:22 2020. Exited Tue Nov 17 16:39:12 2020

Hand sanitizer on entry, also sanitized the bulky green laser goggles before and after my use (forgot contacts). Turned off the laser, sat at desk and considered turning on the laser. Took a break. On my walk I wrote this haiku

Took another break.
Why align these mirrors when
photons have no mass?
I'm going to this seminar, so that's all for today. If nothing else, a reminder (even to myself) to always elog, no matter how small. 
  2583   Thu Nov 19 16:34:01 2020 aaronDailyProgressGeneralcantilever photos, laser intensity noise

Entered lab Thu Nov 19 16:33:57 2020. Usual sanitation, personal reminder to report campus access with Caltech.


we want to coat some of Zach's cantilevers with a-Si so we can make a cold Q measurement. I've started to take some photos, but have become tired and will finish tomorrow. There are O(5) suitable cantilevers produced in January 2018, but I'll have to dig a bit more (or ask Zach) to determine what's what. We can measure the Q of the most promising few cantilevers to be sure they're acceptable.

I borrowed the digital camera from EE shop, but left its case (which is very dusty).

Laser intensity noise

Sending W path beam to a Newfocus 1811 to measure free running laser intensity noise.

Following Shruti's recent diagram, I moved the Newfocus 1811 into position after OMTL1. I also moved PO1.1 back into the beam path, so I can use it to align into the 1811. Turn on the E laser and TEC, also had to move Ma for alignment. I still don't have a +-15V power supply, will ask around. Turn off the laser and TEC before exit at Thu Nov 19 20:41:22 2020

  2584   Fri Nov 20 19:24:00 2020 aaronElectronicsElectronicspower cables

Entered lab Fri Nov 20 19:24:32 2020, usual sanitation.

[blue "Photodiode Power Supply] Looking for a DB9 to BNC adapter. I found this spider instead -- close enough. Use multimeter to measure 24V between pints 4 an 9... not promising. Confirm power is connected, no signal on the frontpanel BNCs either. Could remove this one and take a look on the benchtop, but above is...

[Newfocus +-15V current-limited power supply] Has 3 pole bananas and a power switch on the front. Found a power cable for the back. There's a bananas to 3-pin LEMO already there. Double check the voltage with a multimeter. Alas the connector doesn't fit the PD, but should be some cables in the EE shop or elsewhere...

Didn't find the right connector in EE. On the 'power cables' rack (NE corner Cryo), there was a M-F connector, but I need M-M. Could cannibalize the 12VDC supply? I think for now +-12V is working, so should look a bit more.


I moved the power cables for our preamps for better strain relief (attachment 2 is the before photo). 

I also had left this ND filter sitting on the table (attachment 1). Yikes!

More photos here.

ExitFri Nov 20 20:39:43 2020

Attachment 1: DSCF3541.JPG
Attachment 2: DSCF3542.JPG
  2586   Tue Nov 24 13:23:09 2020 aaronPhotosSi fabSi cantilever photos

Entered lab around Tue Nov 24 13:24:57 2020 to finish photographing Zach's cantilevers.

some things about cameras, and in particular the FinePix F300 EXR

  • ISO -- the camera's sensitivity to light. More sensitive means more noise, but also more signal (useful when exposure time must remain short). 
  • aperture -- size of the opening before the lens. A wide aperture yields a shallow depth of field and lets in more light, but can cause blurriness in the foreground and background. Narrow aperture lets in less light and widens the depth of field, but can lead to diffraction effects or not enough exposure time depending on the application.
  • shutter speed -- how long with the shutter remain open? All the usual tradeoffs of integrating.
For these shots, I have the camera mounted on a tripod and close enough to the cantilevers that the subject takes up the full field. I've turned off the overhead lights and oriented the bright, fluorescent desk lamp away from the camera and slightly up. I'm reflecting some diffuse light back to the cantilevers with a large kim wipe (and my white face / lab coat). I've set minimum ISO, long exposure time, and large aperture. Since I'm handling nominally clean Si, I'm wearing gloves, lab coat, mask, and hair net. I covered the wall behind the shot with paper towel to provide a dark, uniform surface that isn't visible in reflections off the wafer containers and doesn't backlight the shot. The photos are not taken from above because doing so resulted in reflection from the top cover, which I wanted to keep on to avoid dust.
Looks like 5-7 cantilevers could be high Q (no visible contaminants, pitting, cracks, etc). I think there's also a pair of high Q cantilevers in Zach's cantilever cavities cryostat, and maybe one in the cantilever op lev cryostat (QIL). If we measure the Q of the most promising bare cantilevers, we can identify the 3ish best candidates for aSi coating.
Photos can be found in this album. I've pulled a representative good-looking cantilever and attach them here, along with the photo booth setup.
attachment 1: the photo booth
attachment 2: the lines near the top are reflections from the edge of the container. The long sides are parallel, and can give you a sense of the angle of the photograph. 
While doing this, I entered EE to retrieve a spare battery for the camera, and later again to return the camera to its place by the sink.
left around Tue Nov 24 17:50:48 2020
Attachment 1: DSCF3580.JPG
Attachment 2: DSCF3572.JPG
  2587   Tue Nov 24 15:58:00 2020 aaronNotesEquipment Loanmoku CTN to Cryo

Anchal dropped off the Moku from CTN, along with its USBA->USBC cable, power cable, and ipad.

  2594   Mon Nov 30 11:28:30 2020 aaronNoise HuntingLaserpll

Entered lab about Mon Nov 30 10:21:35 2020, after taking a COVID test through Caltech's new surveillance testing program.

I'll pick up where Shruti left off on the beat note. The comb of sidebands becomes a single line  remains a comb when the PID is offKoji suggests maybe the (PLL) PID is oscillating at 10Mhz.

  • Turned on both laser drivers, TEC, 15V PD power supply, HP 8560E spectrum analyzer.
    • E laser TEC was set to 8.301 kOhm
    • W laser TEC was set to 8.992 kOhm
  • Located the thermistor resistance on the RIO data sheets
    • Diode #104978 (E path) has thermistor resistance 10.050 kOhm at the nominal setpoint (25 C)
    • Diode #104987 (W path) has thermistor resistance 10.940 kOhm at the nominal setpoint (23 C)
    • Oddly, Dmass' elog on unboxing these lasers lists a different operating temperature than the datasheets
  • Adjusted the PID on both TEC
    • First, turned down I and D to 0. Next, increased P until there was oscillation. Added back a little D and turned down P until no oscillation. Increase I until it moves to the setpoint.
    • Checked 'step response' when the laser is turned on, and adjusted PID until no overshoot or oscillating on the way to setpoint, and equilibrium reached within seconds. This did not affect the sidebands.
    • Adjusting P while moni
    • toring the beat spectrum results in no change in the sidebands, until the temperature starts to oscillate and the beat is lost.
  • Checking out the HF current mon on a 200MHz oscilloscope to see if something's going on there. The HF drive input is open, so there should be no peaks.
    • W laser has a line at 9.75 MHz, 20 dB above the noise floor.
    • E laser has a line at 22.5 MHz, 20 dB above the noise floor (on second look, this peak is not present. Lots of adjustment between the two measurements though, and I'm not sure what did the trick)
  • I'm seeing the forest of sidebands hopping side-to-side (~38 MHz hops). Modehopping? [no, it was a triggering issue] I adjust the TEC setpoint to the nominal values on the datasheet.
    • The hops are always by exactly 4 times the sideband spacing (~40MHz, so the second to the right sideband frequency at +20 MHz coincides with the second to the left sideband frequency at -20 MHz after the hop)
    • Hm... turning off both lasers, I see several noise peaks in the dark spectrum that 'turn on and off' every other refresh of the spectrum video...
      • This is present even when I take single spectra manually (not continuous). Every other spectrum has some noise forest around 20MHz. Is this an artifact of the SA settings? No reason something at MHz should exhibit such repeatable on/off behavior for my random-near-Hz button presses.
        Indeed, when I turn on the 'frequency counter' on the spectrum analyzer, the hopping goes away... why?
      • With frequency counter on, I now see two sets of sideband peaks. What's the spectrum analyzer doing for demodulation, this looks like some artifact. Perhaps some saturated stage of the spectrum analyzer is causing sidebands. Here's a nice technical note from HP on spectrum analyzers.
  • Larger changes of temperature and current moves the forest of peaks out to higher frequency (after being lost for intermediate values of T and I).
  • The forest of modes is still there even with both PID off.


exit Mon Nov 30 16:12:04 2020

Attachment 1: IMG_0195.jpg
  2595   Tue Dec 1 10:59:49 2020 aaronNoise HuntingLaserpll

Entered Tue Dec 1 10:59:48 2020

Turning on the lasers in a more controlled way today, trying to reach datasheet nominal setpoint

  1. turn down current driver to 0mA
  2. Turn on TEC (P and D at 0, only I => definitely no oscillating).
  3. Ramp up the current to the datasheet's I_bias, while monitoring the DC current mon and laser power. According to the schematic, the total current mon is 1 V / 10 mA.
    • Zach mentioned some modifications to this board in an elog. Hm, I've been using the schematic's current mon mapping (max 100mA), so maybe I've already damaged one of the diodes and that's why we're having issues. I don't see a record of the second (W) laser drive being modified, so perhaps this is why we are only seeing the 10MHz line on the E laser HF current mon.

I'm getting turned around, so I'll summarize the state of the drivers and lasers. Yellow highlight indicates this is a best guess based on things like dates on the DCC, but I haven't verified by eye (by opening the driver chassis or making a measurement).

Laser Driver serial number Driver part number known Modifications Voltage limit DC current mon Measurements
East S1600246 D1200719-v4 none no 1V / 10mA (this must be wrong) Zach 2017
West S1500267 D1200719-v3 current doubled no 100 V/A Zach 2017

Something seems wrong with the W laser path. At the nominal laser setpoint, the E path puts out a steady 5.33 mW; the W path puts out up to 1.9ish mW, but the power is fluctuating between 1 and 2 mW.


Spent some time changing the W/E mixing BS into a michelson BS for the W path (uneven arms). The AS beam from one leg was substantially brighter (by eye and ~10x on the PD) than the other. I confirmed that the mirror is HR for 1550. Probably just clipping, I had the plate BS kinematic mount in the wrong handedness to avoid remounting it; this was misguided anyway, I return it to original state. When I realigned the PLL path (identical to before this Michelson excursion), the forest of modes returned to the gaussian envelope state (not the bessel 2 looking envelope from yesterday). Could this be alignment / path length dependent? I returned the lasers to nominal T and I, and the gaussian envelope remains, so optical path is my best guess.

A little later, I lowered the TEC setpoint for W laser, and the Bessel envelope returned. However, whereas yesterday the 2nd sideband had a maximum now the 1st sideband is maximized.

Another feature that's been puzzling me -- when I sweep the temperature or current monotonically in a direction that moves the beat to 0Hz, the forest moves towards 0 until about 50 MHz. Below 50MHz, the modes are suppressed nearly to the noise floor; I think the carrier is just visible above the floor, but above 50Mhz the carrier is 50 dB above the floor. The cutoff is sharp, and if I continue sweeping temperature or current in the same direction the modes eventually reappear above 50 MHz moving up. My guess is it's another 'feature' of the analog spectrum analyzer that I haven't worked out (maybe secretly normalizing out the 1/f? but it's faster than 1/f rolloff), and that something cuts off low frequency sensitivity. Seeing as I'm well within 200MHz, I'm switching to the moku to check.

While the ipad charges, made this table of the modes I'm seeing at the nominal T_set of 23 C (10.940 kOhm) for W laser, 25 C (10.050 kOhm) for E laser. The marker tells me sideband spacing is 9.6 MHz; the W current drive HF mon has a line at 9.7 MHz, so it does seem these are related. I've attached the oscilloscope trace, where you can see that the W laser drive HF mon (chan 4) has RMS noise at least 100x the noise on E laser HF mon. The oscillation is dominated by the peak at 9.7 MHz, though there are a few others. Maybe the solution is just to swap in another laser driver -- this driver is a modified version an out of date revision of the circuit. Tomorrow I will swap in the combi controller for the W current driver and see if that helps.

E laser current (mA / 2) W laser current (mA / 2) Envelope order carrier frequency (MHz) # of sidebands (100kHz RBW)
77.41 69.50 0 155 3
75.54 69.5 0 177 3
53.6   0 995 3


exit Tue Dec 1 18:08:59 2020

  2596   Wed Dec 2 13:37:55 2020 aaronNoise HuntingLaserW laser oscillating

Enter Wed Dec 2 13:37:57 2020

I'd like to know whether the problem is in the W laser driver (S1500207) or the diode (104987). I swap the E laser drive over to the W laser diode, so am driving diode 104987 with driver S1600246. I still don't see the E laser driver oscillating, but the W diode power still reaches only 1.38 mW before falling off (ramping up current at T_set). Just in case, I also drive the W diode using the E driver but the cable from the original W driver (checking that the cable isn't the cause); no oscillation.

Entered EE to obtain grounding strap (Wed Dec 2 14:10:12 2020). On second thought, putting off diagnosing the W laser drive and just continuing with ITC 502. I did get a look inside, and don't actually see evidence that R33 was changed, just a added resistor from R30 to V_ref mentioned on the schematic.

Found this elog helpful for making sure the pinout for ITC 502 is compatible. Oddly, I can't set the laser diode current limit higher than 10mA, though the range of the device is +- 200 mA. I suspect the left 2 digits of the current display are just inoperable, because I can turn the adjustment pot in either direction until the digits stop moving. I set the current limit at 149 mA by counting by 10, and will double check the eventual current from the monitor. the diode definitely is nearing end of life, I'm only getting 1mW at nominal setpoint. I was squeezing a little extra out of the custom laser driver, but probably at the expense of the diode.

With the thorlabs driver, we're down to 1 peak at last!

Looking at the spectrum today, maybe the low frequency cutoff I noticed yesterday is just a frequency offset issue?

switching over to Moku... wow this is a user friendly device.

  • beat note drifts by MHz over minute timescales
  • FWHM ~ 140 kHz
  • 35 dB above noise floor

Phaselock setup

  • Photodiode output to splitter (ZFSC-2-4+)
    • Long cable to 83 dB (!!?) gain amplifier to mixer (ZAY-1B) LO input. Mixer requires +23 dBm LO.
    • short cable to [gain] to mixer (ZAY-1B) RF input

While choosing the gain for producing an LO from the 1611 output, I tried to measure the absolute power with the Moku. When I change the range from 1 Vpp to 10 Vpp, the overall peak height changes by almost 10 dB. I wondered if this were just a clipping issue, so I hooked up the Moku function generator output to the channel 2 input to see if the behavior is consistent. The beat note is 300 mVpp at the laser settings I'm currently using, which should be about 0 dBm dissipated into 1 MOhm. Sourcing 300 mVpp from the Moku into its channel 2 input gives the correct power reading, but the 300 mVpp from the 1611 reads -25 dBm with 10 Vpp range and -34 dBm with 1 Vpp range. What's going on?

  • Probably just outside the linear range of the 1611, which saturates at 1mW input power. I'm seeing some unexpected sidebands (>> 9MHz), so nonlinearity makes sense. We're still well below the 10 mW damage threshold, but should add back the 90-10 pickoff mirrors now that alignment is done.
  • After adding the 90-10 (power) BS, the AC output of the 1611 has ~3 mVpp (amplitude). nice
  • The beat is now -53 dBm. That's still below what I'd expect for a 3 mVpp signal; Moku thinks it's seeing a 1.45 mVpp
    • I want to attribute this to some setting of the oscilloscope or Moku, but it's also not consistent with my expectation. moku shows 6 mVpp when measuring its 3 mVpp output with 1 MOhm input impedance, suggesting there's a factor of 2 I'm missing somewhere; on the other hand, the signal from the 1611 needs a factor of 1/2 to be consistent with the oscilloscope measurement. Awkward.
  • started these measurements at 50 Ohm input impedance for the SA, but when results didn't make sense I repeated at 1 MOhm. Should have stuck with 50.

I would have to string together eg 2x SR560 to get enough gain. I guess that's fine, because the noise floor of the SR560 is O(nV/rtHz)... but it gives me the feeling of doing something wrong, and I'm hungry so will pick it up tomorrow.

exit Wed Dec 2 18:42:15 2020

  2597   Thu Dec 3 10:18:07 2020 aaronNoise HuntingLaserpll

Entered somewhat before Thu Dec 3 10:18:07 2020

finishing up the PLL. I still need to set an appropriate gain for the LO, but in the meantime I'll try to use the Moku's laser lock feature


This is pretty straightforward. Moku has an internal oscillator and lets you control the LP (corner frequency) and controller filter (proportional gain, integrator frequency, differentiator frequency, integrator saturation level, differentiator saturation level). I'm driving the E laser HF and LF inputs from the Moku outputs. Quickly acquire a lock and play around with filter settings for a while.

exit Thu Dec 3 12:30:47 2020

  2599   Fri Dec 4 10:36:18 2020 aaronNoise HuntingLaserpll

Entered lab, then grabbed a spool of cable from EE, started elog Fri Dec 4 10:37:52 2020

thought about filters. The narrowest line I managed (yes really) is in the attached screenshot. I amplified +40 dB with Agilent 8447A before the splitter.

exit Fri Dec 4 16:14:19 2020

Attachment 1: IMG_0015.PNG
  2601   Thu Dec 10 10:05:03 2020 aaronNoise HuntingLaserpll

enter Thu Dec 10 10:04:54 2020


Doesn't the phase meter just read out the noise even with no locking? I thought that was going to be the magic.

For locking, the mixer readout is in units of phase and the laser current modulation gives a proportional frequency modulation with no frequency wiggles until > 1 MHz. So it should phase lock with no integrator, but I'm not sure if the free running noise will drive it out of the phase lock or not. I wonder if its possible to use the phase meter as an error signal. It would be much easier to lock frequency instead of phase via a mixer.

Hm, hadn't tried the phasemeter application. I'll check it out now... if I understand your second comment, you're saying because

f = \frac{d\phi}{dt} \\ \implies \int f dt = \Delta \phi

an error signal proportional to phase is already integrating the frequency error. Makes sense, but does 'easier to lock frequency instead of phase via a mixer' follow, or is that unrelated? 

The Moku phasemeter does produce a nice power spectrum. Here it is up to 200 Hz, I'm working with Anchal's ctn-scripts and pymoku to get the higher frequencies. 

Still odd that the beat amplitude is so small. Let's check:

quantity Power of E beam @ 1611 (power meter) Power of W laser @ 1611 (power meter) 1611 DC voltage from E beam 1611 DC voltage from W beam DC voltage gain responsivity @ 1550 (approx) Expected DC voltage due to E beam Expected DC voltage due to W beam
value 307.8 uW 65.7 uW  -1.55 V  -400 mV 10 V/mA 1 A/W -3.08 V -660 mV

Looks like neither beam is producing the expected photocurrent, but because the error is not the same factor for both beams I suspect alignment / beam size. I'm aligning with some apertures to avoid smearing the beam on lenses. Aligning each beam led to more power, but my procedure doesn't simultaneously align both beams. 

exit Thu Dec 10 15:11:30 2020

Attachment 1: IMG_0016.PNG
  2602   Mon Dec 14 10:32:51 2020 aaronUpdate  

Enter Mon Dec 14 10:32:49 2020

Met with Shruti and finalized the fiber components we want to order.

Alignment procedure has apertures on the E beam path, one before the mixing BS and one after.

  1. Use apertures to determine a path for the E beam
  2. Place the PD such that signal from the E beam is maximized
  3. Align W path to the PD using the penultimate aperture. Because the penultimate aperture and PD position are shared with the E beam, the beams should be copropagating.
  4. Add short focal length lens before the PD.
  5. adjust alignment to maximize beat note.
    1. maximize DC level for E and W with the other path blocked.
    2. maximize beat
    3. repeat

W path laser is down to 25 uW at the PD. Also noticed that the y-alignment depends sensitively on the position of the final lens. The PD height is not the same as the height of the apertures, or the lens is off-center.

Exit Mon Dec 14 15:36:59 2020

  2603   Thu Dec 17 10:23:08 2020 aaronNotesPSOMAlab entry

enter Thu Dec 17 10:24:44 2020

Just deskwork today.

exit Thu Dec 17 16:54:59 2020

  2604   Wed Dec 23 11:13:57 2020 aaronThings to BuyPurchasesoptomechanics arrived

Entered lab around Wed Dec 23 11:14:29 2020 to bring in optomechanics from Newport, step stool from McMaster, and a few other items for around the lab.

  2605   Mon Jan 4 10:46:01 2021 aaronLab InfrastructureTemperature Sensingfresh temperature sensor

Entered Mon Jan 4 10:45:56 2021 .

Temperature in the lab is 89 F at the sensor by the electronics rack. I had been planning to put our AD590s on a board today, unnecessary equipment is already off but I also turned off cominaux and the Sorensen DC supplies. There is hot air coming from HVAC.

I spent some time gathering components and checking out AD's notes on the sensor. I'm using the same components as Andrew/Johannes' old circuit, and putting it on one of Anchal's "generic op amp / diff amp" boards (D1900129-v2). After checking out the old circuit, I realized we still have it in the cryo lab -- it's just missing the AD590. I put the AD590 on a breadboard, made a few connectors, and confirmed that I get a sensible reading (83 K near the center of the room, a couple degrees hotter in/by the electronics rack where the sensor is located).

I noticed that the AC connection on one of our Tenma power supplies is loose (wobbling the cable switches the supply off/on). It's a dual supply, but since I wouldn't want to use it elsewhere I'm powering the AD590 with it (doesn't need to move, out of the way above the rack).

Here's the temperature (second trend) over 20 min, will post the overnight minute trends tomorrow.

Picked up the mess, changed the dust mats, exit

Attachment 1: Screenshot_from_2021-01-04_16-13-53.png
  2606   Tue Jan 5 16:43:44 2021 aaronLab InfrastructureTemperature Sensingfresh temperature sensor

Here is the 10 min trend for the past day. The temperature fluctuates by up to ~0.3 F over short times, and drifted by only ~0.5 F on average throughout the day. The lab is running consistently hot.

Attachment 1: Screen_Shot_2021-01-05_at_16.46.14.png
  2607   Wed Jan 6 10:47:18 2021 aaronDailyProgressPSOMADC to PSOMA rack, realtime model

enter Wed Jan 6 10:47:10 2021 

Making a new cable to run from the Sorensens' rack over to PSOMA rack

  • Grabbed from EE: an appropriately chonky 3-wire cable (AWG 12, same as the old cable), the 18V 'ligo style' connectors (not needed), and some lugs. Confirm the cable is long enough
  • open up the power strip, take a photo to make sure I get the wire mapping right.
  • Remove the old (short) cable, crimp the lugs (and insulator jacket) onto the new cable and install it on the power strip.
  • Run the cable along the cable tray to the Sorensen. Turn off the power supply, then attach the lugs on that end with a 10-32 screw/washer/nut
  • Turn on the supplies, confirm +- 18 V at the power strip. All good, returned parts to EE.

PSOMA realitime model

I figured I'd initialize our realtime model for PSOMA. First, copied over x1cry.mdl (cryo cavities model) into x1oma.mdl. When I build this model, I get the following error

Linux source does not match currently running kernel.

The RCG expects the linux source to be at /usr/src/linux.  For modern
distros this should be a symlink to the source installed as part of
the kernel header package for the running kernel.  For this system:

/usr/src/linux -> /usr/src/linux-headers-3.2.88-rtcds

Please create/update this link, or set the RCG_IGNORE_KERNEL_RELEASE
environment variable to bypass this check

 I haven't seen this before, do I need to update something? I haven't made recent changes to cymac, so I would be surprised if it's running a newer version of linux / rtcds than the existing source (and only one version of rtcds exists in /usr/src anyway). Indeed, when I ask for the currently running kernel (uname -r), it is '3.2.88-rtcds'; and the link at /usr/src/linux points to /usr/src/linux-headers-3.2.88-rtcds. I would expect that the source "linux-headers-3.2.88-rtcds" matches the kernel '3.2.88-rtcds'. I'm setting the ignore flag for now, but would like to know what this means.

Setting ignore to '1' or 'True' does not avoid the error message. I don't see mention of this message on the 40m or other elogs, so I'm a bit stuck. Since the realtime model isn't critical right now anyway, that's all for now.

exit Wed Jan 6 16:27:10 2021

  2608   Wed Jan 13 11:07:24 2021 aaronDailyProgressPSOMAfiber + free 3 corner hat

Picked up Thorlabs and Newport packages from Downs, enter lab Wed Jan 13 11:07:36 2021

The items that arrived today are:

  • FC 1611 photoreceiver, plus 2 power cables
  • cell phone lens kit
  • FC mating sleeve brackets (double only)
  • FiberPort free space couplers, plus mount
  • LB1 beam blocks
  • 90-10 (x2), 50-50 (x1), and 99-1 (x1) fiber beamsplitters
  • rectangular optics mounting bases
  • Remaining ultima mirror mounts (left handed)

Attachment 1 is a week long hour-trend of the temperature at the cymac electronics rack.

I disassembled most of the free space PLL setup, and replaced with fiber components (2x 90-10 BS, 1x 50-50 BS, leading to 1611 and one open ended fiber). On the 90% paths of the first BS, I'm coupling the fibers to free space with the fiber ports.

I also moved the mach zehnder and cavity over, and swapped most of the optic posts-and-forks to post-and-base. Still fiddling with positions / spacings that allow adjustment.

Exit around Wed Jan 13 19:16:39 2021

Attachment 1: labTemp.png
  2609   Thu Jan 14 17:16:35 2021 aaronDailyProgressPSOMAfree space setup

enter about Thu Jan 14 17:17:03 2021

Finished laying out the MZ, one cavity, and PDs. Need a couple more beam dumps, and should get 3/4'' posts with height appropriate for DC monitor PDs and PBS mount (as in D0901749).

Cleaned up to more easily work with two people tomorrow.

exit Thu Jan 14 19:25:15 2021

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  2610   Fri Jan 15 09:54:18 2021 aaronHowToPSOMAmode matching

[aaron, rana]

aaron enter about Fri Jan 15 09:54:39 2021. rana about

Aaron wiped down keyboard, doorknob, light switch, other high contact surfaces. Rana pointed out several improvements we should make to the optics and electronics, and we tried to collimate the beam coming out of the fiberport.

We noticed the fiber enters the port at an angle, and tried to correct for this to no avail. Turns out, the reason for the angle is to compensate for the angle on the end of FC/APC connectors. You can see an example in the diagram for Thorlabs' fixed focus FC/APC collimators (as opposed to the FC/PC collimators, where the end is perpendicular to the beam and the fiber enters at normal incidence).

We also were concerned that we were seeing only 1.3 mW out of the fiberport -- but we were measuring the W laser path, so this measurement is consistent with the power output from that laser. The E path has 3.9 mW from the fiberport, which I think is consistent with expected losses from the 10% pickoff and couplers.


accounting for observed power

I'm tracing our optical path and accounting for losses. We should at some point rename the E and W lasers, since they are no longer pumping parallel cavities. Pump and signal would be appropriate; cardinal directions are ambiguous, since the relative orientation of the beams changes before the MZ.

Which laser Power after diode (mW) Before isolator After isolator Before EOAM After EOAM Before EOPM After EOPM Before 10% pickoff After 10% pickoff After fiberport
East 21.5 21.5 18.3 18.2 8.4 8.3 4.6 4.6 3.9 3.9
West 20.4 20.5 18.4 18.4 2.4 2.6 1.5 1.5 1.2 1.2

The measurements showing increasing power across connectors (eg after diode to before isolator on W path) are correct, and I attribute to different beam diameter launching from fiber vs from connector affecting the power meter's reading. Not including connectors, these are the expected losses of the components, with anomalous losses highlighted:

Part Expected Optical loss (without connectors, dB) Observed on E path (dB) Observed W path (dB)
IO-G-1550-APC (isolator) 0.55 0.70 0.45
MXAN-LN-10 (EOAM) 3.5 3.36 8.85
MPX-LN-0.1 (EOPM) 2.7 2.56 2.39
PN1550R2A1 (pickoff) 0.8 0.72 0.97

Obviously we should be getting a lot more power from the W path -- and it's encouraging that the laser may not be at fault! Both lasers are near their nominal output power, and in particular we probably could get no more than another 0.1 mW from the E path (assuming we could recover the extra 0.15 dB at the isolator).

I turn off the W laser to inspect the fiber tips with magnifying glasses (from EE), but nothing visibly dirty. Here is an in-depth document describing inspecting and cleaning fibers. Dry wiping the EOAM's pigtails did not change transmitted power. Perhaps we can try again with a fiber microscope for a better view. The west EOAM itself has one bent pin, and is also suspect.

aligning fiberport

Afterwards, I followed Thorlabs' steps to pre-align the W beam fiberport. The E beam fiberport appears collimated to the extent I can tell by eye, but I'd like to use the beam profiler to make fine adjustments.

quick spectrum

Since the fiber PD is set up, I measured the beat note's frequency noise with Moku's phasemeter. Saved the binary and will plot when I'm with my laptop.

exit Fri Jan 15 18:16:38 2021

  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.


  • 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
  2612   Mon Jan 25 13:02:46 2021 aaronUpdatePSOMA 

enter Mon Jan 25 13:02:47 2021

cantilever Q materials

I moved the following materials to measure cantilever Qs from cryo lab to QIL. The are located in bins labelled 'cantilever Q' in a cabinet on the S wall of the QIL lab (see photos).

  • cantilevers
  • HeNe laser and power
  • QPD from the GeNS setup, and power
  • What I think are the clamps Zach was using for cantilever Q measurements.

I also identified in QIL the IR labs cryostat that was used for cantilever Qs, and is now set up for PD measurements. I tried lifting out the cold plate, but felt resistance while opening and stopped. Probably the electrical connections are keeping the cold plate in place, and I would like to check with the user of this cryostat before proceeding.

three corner hat

I am recording spectra of the beat note between three lasers: PSOMA north laser, PSOMA south laser, and cryo cavities East laser. I unplugged the E laser from its fiber-to-free launch (after Faraday isolator), and instead send it to the PSOMA table by fiber. Without changing settings on the cryo cavs TEC or laser driver, the E laser is 8.1 mW when it reaches PSOMA table. When measuring the beat note between the cryo cavs E laser and PSOMA north (south) laser, I send the E laser through the south (north) 90-10 pickoff BS in place of the PSOMA laser. Before recording spectra, I tune the current of the PSOMA N and S lasers until all beat notes are < 20 MHz (there is a few MHz drift during the measurements).

Summary of the measurements, all taken at the FC 1611 (AC measurements on the Moku):

  • acquisition speed: 125 kHz
  • phaselock bandwidth: 10 kHz
  • coupling: AC, 50 Ohm
  • Moku input range: 1 Vpp
  • Measurement time: 1 m 40 s
  • freewheeling: yes
Pair of lasers DC intensity mon (mW) beat note power (dBm) beat frequency (MHz)
PSOMA north and south 6.0 3 18
PSOMA north, cryo cavs east 4.3 -1 24
PSOMA south, cryo cavs east 3.5 -2 5

I notice that the FC 1611 has a UPC connector on its face... but the rest of our components have APC connectors. I'll watch out for effects from this, and order an adapting fiber. I also see sidebands at the harmonics of the beat note when the note is > 0 dBm (linear regime of 1611 is only 1mW).

The rate-limiting step is transferring data from Moku RAM to the ipad over the Wifi... should set up the Moku on ethernet, and check out ctn-scripts for automating the process.

exit Mon Jan 25 16:10:59 2021

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