40m QIL Cryo_Lab CTN SUS_Lab CAML OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  Cryo Lab eLog, Page 32 of 62  Not logged in ELOG logo
ID Date Author Type Categoryup Subject
  2460   Mon Jul 15 18:02:48 2019 AnnaDailyProgressLab WorkPrepping RTDs to put back in cryostat

We prepped three RTDs to add back into the cryostat. One was placed on a disk with varnish, and the other two will be placed else where. Twisted phosphor bronze was used for the lead wires on the RTDs, following the attached drawing.

RTD tips 

For the solder pads, the technique that works very well is to first heat up the gold pad and the wires, and then bring the solder close and begin melting it - it will flow onto the pads and cover all the wires very well. Otherwise, the solder is very hard to work with and does not stick to the wires unless they are heated. Also, it is important to have the wires from the RTD and the lead wires passing through the solder holes in opposite orientations, because the wires will travel away from the RTD out of the system. This is necessay otherwise the wires would have to be bent in this direction. So the RTD wires go down through the holes and the end of the lead wires should come up into the holes and be soldered in place. 

Next time, we will varnish to cover the stripped lead wires instead of tape, because this will form a better seal and will not result in trapped air.

We put the finished, clamped RTDs in foil and into the furnace to bake them over night before installing them tomorrow.


Attachment 1: IMG_3432.JPG
  2462   Wed Jul 17 11:13:35 2019 AnnaDailyProgressLab WorkAdditional Q measurements

Q measurements for 970.68 and 2224.72 Hz mode at room temperature. The previous measurement for the 970 Hz Q factor was 28367, so the data set with a longer ringdown allowed for a much better fit. For the rest of my Q measurements I will take longer ringdown data sets to improve fit accuracy, and I will add accuracy stats soon - I will put them in my code next. 

Eigenfrequency tau Q factor
970.68 Hz 12.52 38177
2224.72 Hz 2.86 20012


Attachment 1: decay_fit_970.pdf
Attachment 2: decay_fit_2224.pdf
Attachment 3: AnnaQcode_one_datafile.zip
  2466   Wed Jul 17 22:46:09 2019 DuoDailyProgressLab WorkFrontend restarted

I have been using the digital system in cryolab to test the noisemon and got problems (logged in SUS elog: https://nodus.ligo.caltech.edu:8081/SUS_Lab/1795

I restarted the frontend according to Chris' elog: https://nodus.ligo.caltech.edu:8081/Cryo_Lab/1793

The system is finally up again.

  2473   Wed Jul 24 22:17:08 2019 annaDailyProgressLab WorkCryostat modifications "20% chance of working"-aaron

[shub, anna, aaron]

We opened up the cryostat and added cold straps from the top of the cold  resevoir to the cold plate. The disk RTD was removed and a couple crimps broke, but the two other RTD resistances read fine, did not end up replacing the disk RTD, there is now an RTD remaining on the bottom and middle plate.

We placed a cold mirror- (Cold Mirror, 25.4 mm, 45° AOI, 780-2500 nm Transmittance Newport) into the cryostat on top of the hole on the disk inbetween the periscope and the disk.

Inserted number 6 disk 2in.

Wrapped the system in 3 sheets of foil

Ended up removing the strap placed early because the cryostat couldn't close, still very hard to close afterwards.

Ended up removing the copper strap entirely and took off a layer of foil in order for beam to finally come out clean.

Closed and pumped down, pressure dropping very slowly.



  2482   Mon Aug 5 14:00:48 2019 annaDailyProgressLab WorkESD Issues

I am having issues with the ESD, the power source is staying at 0.54 when I start an excitation. I opened up sitemap and the ESD is definitely on, and I tried changing the sign on the ESD from -1 to 1 but this did nothing so I changed it back.

I then took off the 10 pin/BNC cable from the cryostat to test the connections. I am getting the expected ~1.5 kOhm reading across the two RTDs,  150-300 Ohm across the heater, but there is no connection(beep) or resistance across the ESD pins (1 and 10) as well as no reading on the current +/- pins.

I'm not sure if the wires broke. They were fine on Friday - the ESD was working then and I do not believe anything has been changed since then.


  2485   Wed Aug 7 15:39:03 2019 aaronDailyProgressLab WorkESD Issues

The ESD should look like a capacitor from the outside, so I would expect a very large (~infinite) resistance. On the curernt pins--are there three RTD installed? Recall that the RTD are wired in series, so removing a single RTD will leave the current leads with an open circuit.

The ESD can be stuck near 0 for a few reasons

  • There's a short circuit. It sounds like that's not going on, because you're measuring an open circuit across the ESD pins (good).
  • The sign of the excitation is wrong, which you've checked.
  • There's something turning 'off' the excitation just before the DAC. If the channel X1:SIQ-ESD_OUTPUT is not reading zero, there should be a signal from the DAC, but just in case you can check the DAC channels directly.
  • The signal is getting to the DAC, but there's no DAC output. Sounds like this is the mostly likely at this point, and that means the front ends may need to be restarted. To do this, use the following scripts (/opt/rtcds/tst/x1/scripts/)
    • ./killAll.sh
    • ./startAll.sh
    • If that doesn't work (or if cymac freezes up/you get an error), restart cymac1(the computer) from the command line.
  • If there's a signal from the DAC, you can continue checking the rest of the signal chain. Is the BNC faulty? Can the HV driver do anything, even if disconnected? Is there a short downstream that the driver can't drive, but that goes away when you unplug the driver from the cryostat? Etc.
  2487   Thu Aug 8 14:46:56 2019 aaronDailyProgressLab WorkESD Issues

I unplugged the BNC from the HV driver input, and observed the driver output drop from 0.52V to 0V (according to the digital display). Probing the BNC with the multimeter, indeed the DAC is giving only 2mV instead of the expected 5V.

Attachment #1 is the state of the testpoint screens before I restarted the FE. After taknig that screenshot, I did the following:

ssh cymac1
cd /opt/rtcds/tst/x1/scripts/


Screenshot #2 is the state after startAll finishes running. I'm still seeing the FE lights red on the SIQ_GDS_TP screen, but looking back at some previous instances of this problem I think everything is nominal now. I probed the BNC again and get the expected 5V output. I ran

burtwb -f x1siq_burt_190808_145255.snap

to restore the settings from before this FE restart, and the system should be ready to go!

Attachment 1: before_FErestart.png
Attachment 2: after_startAll.png
  2491   Tue Aug 20 18:16:31 2019 annaDailyProgressLab Work 

aaron, anna

The beam has been clipping a lot recently, so we opened up the cryostat and adjusted the lens to get the disk level. Before we started adjusting it, it was very crooked and when the disk is raised the beam shifts drastically causing the major clipping.

With the adjusted lens postion the beam comes out clean again. Also, we replaced the foil in the holes of the actuator - the old foil had gotten drawn inbetween the gap in plastic sheath and metal rod.

Disk 8 is in the cryostat currently.

Room Temperature

Mode Frequency
1st butterfly 969.47, 973.08
1st butterfly 1005.18, 1007.19, 1008.63
2nd butterfly 2229.61, 2298.97

I excited these 8 modes before I had to head out. Cooled down before leaving.


  2512   Mon Mar 2 18:37:00 2020 DuoDailyProgressLab WorkExcitation working again

[Duo, Ian]

After the beam was re-aligned, we tried to excite modes again. However, somehow the excitation was not working. We fixed it. The reason is that the connector from CyMAC to the anti-imaging chassis is disconnected (attachment 1).

We reconnected it. Then the digital system crashed. When we move these cables around, it is good to check the status of the digital system. After the digital system is restarted, the excitation is working again.

Attachment 1: thumbnail_image1.jpg
  2535   Thu Jul 16 11:27:18 2020 aaronUpdateLab WorkReopening cryo lab

Notice of lab entry

Date of entry: 17 July 2020
time of entry:  13:00 PT
time of exit:    18:00 PT
Date of entry: 17 July 2020
time of entry:  13:10 PT
time of exit:    17:25 PT
Purpose: I will begin the reopening procedures outlined in previous elogs (2534, 2533). I'll also try to locate at least one Wilcoxon accelerometer and an M2 ISS readout board. I'll enter the EE shop to move one solder station from EE to cryo lab. 

That's probably all that's necessary for a typical lab entry, though more details always good. Here's what I'll be doing and a couple checklists for COVID procedures.

Planned activities
  1. Go to cryo lab and do a quick survey for PPE. I will pick up 2 sets of PPE, cleaning supplies, and signage from Downs 318 for cryo (one personal set per person). For list of PPE and other supplies, see the PSOMA hardware inventory (under Procurement on the wiki).
  2. Follow the applicable steps in the "back to lab" checklist in prior elog.
  3. ​ ​Put together personal tool cart and workstation, labeling
  4. Check / repair HEPA filter
    1. connection to wall
    2. check filter specification against requirements. air scrubbing reference. Calculator for acceptable person-time limits for shared rooms (currently not applicable, since cryo will be one person per day occupancy). Aerosol guidelines reference.
    3. See if particle counter still logging.
    4. Air flow meter measuring flow at filter, around filter, at the door, at the opening in the ceiling near NW corner.
  5. Set up in/out box bins for materials / tools entering and exiting cryo lab.
  6. Locate seismometer and circuit.
  7. Transport 1 solder station from EE shop to cryo
  8. Check inventory in cryo lab against the PSOMA hardware list
  9. Make sure cymac and the fe are running.
Before checklist

During checklist

  • Physically distanced at all times, following one-way signage around campus, wearing a face covering. I'll need to use elevators for a while, and will keep those single occupancy.
  • Wearing mask always and washing hands as appropriate.
  • On arrival, wipe down door knobs, keyboard, mouse, knobs, any frequently touched surface. 
  • No more than 1 person in the cryo lab per day, stay more then 6' from others.
  • Update other lab members of activity on the elog. The remote lab member is a 'virtual buddy'.

After checklist

  • complete elog, close work permit
  • Sanitize shared surfaces
  • Dof PPE except for face mask
  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
  2538   Mon Jul 20 08:59:02 2020 shrutiUpdateLab WorkAt cryo lab

Notice of lab entry:

After going over the checklist outlined in the previous elogs by Aaron, I completed everything relevant in the one labelled 'before', 'lab entry'.

Entry ~08:30, Will be here until ~17:30, with a break for lunch and a meeting (12:00-14:30)

Purpose: To give myself a lab tour, clean up the area around the workstation I'd be using, arrange and label tools, record part numbers of components for the PSOMA experiment

I also went in to the EE shop to get a solder station and related implements that I could find more than one of. I've placed this on the table to the south of the cryo Q experiment, after clearing up the space and placing the boxes below the table (see pictures).

Attachment 1: FFDA12DE-AD53-4751-96C5-7AA726F4BC51.jpeg
Attachment 2: 332F07DE-A250-44A6-BA28-5A0DF65207E9.jpeg
  2539   Tue Jul 21 14:03:33 2020 shrutiUpdateLab WorkAt cryo lab

Notice of lab entry: ~13:45. Expect to be here until around 17:00.

Liz dropped off PPE that was collected from the 40m (Thanks Liz!), this included two sets each of items as marked on the safety tab of PSOMA inventory doc. Also, see Attachment 1. I have removed one set of items and placed them on the tan cart that I use. Aaron's set is still in the box by the door; while I have worn gloves and tried not to touch those items, please assume that I have.

I think I have located the PD readout circuits requested by Gautam, which was in Johannes' setup. See Attachment 2,3,4; the DCC number of 2 checks out. I have placed them in a box in the area near the entrance marked by a red square. Other items labeled with '40m' are also in that box.

Attachment 1: 156CA9F4-5287-4222-9C45-5ACA006DFEDC.jpeg
Attachment 2: 64F84876-1D78-427F-B272-5584D0D7AC2C.jpeg
Attachment 3: B56E1C6B-C039-4E7E-85F1-AEFE8FA1BEAB.jpeg
Attachment 4: D540AD24-6D44-447C-B87F-B6CCD01D9521.jpeg
  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

  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.

  2546   Thu Jul 30 09:13:14 2020 shrutiDailyProgressLab Workbeam profile prep

Notice of lab entry: I will be at the cryo lab today (30 Jul 20) 9am-5pm.

Purpose: Beam profile the Rio planex laser

- Turned on the laser that goes into the east cavity on. Turned on the Tenma supply, then the laser current driver  D1500207 labeled'E'. Saw a tiny, but bright, green spot on the detector card.

- Located razor blade and translation stage, for the beam profile measurement but not sure which power meter/ photodiode to use for 1550 nm. I plan to move the optics on the path of the east laser (to the east cavity) in order to do this measurement and later set up the initial ring cavity

- Aaron suggested I do another airflow measurement within the lab. Without the scrubber, there seems to be no measurable flow around either the Cryo-Q table or the cantilever table. I moved the scrubber into the lab near the workspace at the north side of the lab and let it run on medium speed. A few cm from the scrubber it the airflow rate is almost 5000 CFM, but it becomes <40 CFM even as close as the Cryo-Q table and again becomes negligible near the cantilever table.

- I set up the translation stage, moved relevant optics, but will continue to measurement later after I've researched and located a 1550 nm power meter

Two of the four overhead lights over the west (cantilever) table don't work anymore. Three other overhead lights are very dim/out.



  2547   Fri Jul 31 08:51:00 2020 shrutiDailyProgressLab Workbeam profile prep

Notice of lab entry: I will be at the cryo lab today (31 Jul 20) 9 am - 2 pm.

Purpose: Look around for components [power meter charger, power connectors for PDs, flashlights, etc], laser operating manual; find out specifications of available mirrors, RF PDs

Also, there seems to be only one laser temperature controller in the lab. The west cavity laser TEC port is not hooked up to anything. For the time being this is okay since we'd be using only one laser.

  2548   Mon Aug 3 13:10:46 2020 shrutiDailyProgressLab WorkInitial experiments and prep

Notice of lab entry: I will be at the cryo this (03 Aug 20) afternoon

Lights fixed, safety, cleanliness:

- On entering the lab I noticed that the work with the light fixtures was completed. Unfortunately I could not avert it or get it all covered in time; I had assumed that I would be contacted beforehand but was not. But, by inspecting the table I do not think it looked any dustier than before. For any such activity in the future after we’ve cleaned the optics, I will remember to get it covered beforehand.

- The particle counter did not seem to be saving any data so I’m unsure what the effect of this activity was. The 1 micron particle count:
When I entered (1 pm): 80
(6 pm) : 70
This change might probably be entirely attributed to the air scrubber.

- When Aaron and I chatted with Calum today about COVID safety, Calum pointed out that turning on any HEPA filters in the lab would reduce the time between single-person occupancy to almost 0 for our room, as it would serve as an additional air scrubber. I tried locating a switch on the cryo cavity table for the HEPA fans but could not locate it today.

Laser and beam profile related:

- After reading through bits of the laser operating manual and turning on the east cavity laser, I turned on the TEC (thermo-electric cooler) box [TED 200 C] with neither the TEC nor the servo on. I used this just to read off the resistance values of the sensor. With the current drive off it was 11.2 k-ohms [22 C].

- I waited until the sensor readings stabilized to changing at the level of a few ohms around 8.5 k-ohms [28 C] in a minute and began measuring the beam profile. (See Attachment 1 for setup)
I could not mount properly the only translation stage I found since the holes on it were smaller than 8-32, and moreover, I could not locate anything suitable that fits into the 1/4" holes on the table with this.

- Nonetheless, when I took some data and plotted it, it looked like an error function so I took more data. Will post plots later after fitting and analyzing. I may have to repeat this again.

- The sensor for the power measurement was S122C (Germanium) with a range of 700-1800 nm and 40 mW. After setting the power meter to 1550 nm, the measured power of the entire cross-section was ~2.3 mW.

- Also in the image in Attachment 1, the two optics (HWP and mirror) near the fiber-free space coupler, were previously in the path of the laser and now moved to either side of the beam. No other optics were moved from the previous set-up.

Attachment 1: IMG_633BBA57553C-1.jpeg
  2549   Tue Aug 4 14:08:44 2020 shrutiDailyProgressLab WorkInitial experiments and prep: Beam profile

Notice of lab entry: I will be at the cryo lab for a few hours today (04 Aug 20) afternoon


Beam profile results [razor-blade method]

At a few locations along the beam I measured the vertical and horizontal beam radii by measuring the power at different positions of blade edge across the beam. The power measured at the photo-diode was fitted with  a + b \times {\rm erf}(\sqrt{2}(x-x_0)/w_z)) where w_z is the beam radius at the location along the beam and x was either the horizontal or vertical position of the blade.


The standard deviation as estimated from the fits are lower than \pm0.002 mm for all estimated radii.

But with the crude nature of the setup and not having the laser temperature stabilized (resulting in power drifts while taking readings), I guess that the error in each measurement is higher. The data in Attachment 3 also has recorded the resistance of the temperature sensor at different points while taking the data.

Beam radii
Distance [in.] Horizontal radius [mm] Vertical radius [mm]
5 \pm 0.1 0.120 0.121
6 \pm 0.1 0.146 0.150
7 \pm 0.1 0.175 0.173
8 \pm 0.1 0.203 0.200
9 \pm 0.1 0.231 0.229


- Attachment 1 has the updated setup with the clamped translation stage

- Attachment 2 shows the measured points with the error function fits. The offsets between the different curves along the x-axis are arbitrary.

- Attachment 3 shows a linear fit and an estimated divergence angle. I've assumed that all points I measured are outside the Rayleigh range, i.e., away the beam waist. The caption '5H' means that this set of data was taken 5 inches away from the output coupler (fibre-to-free space) moving the blade in the horizontal direction.

- Attachment 4 has all the data and jupyter notebook with analysis

- Attachment 5 shows the beam spot on the view card

Attachment 1: IMG_0268.jpg
Attachment 2: Erf.pdf
Attachment 3: Div.pdf
Attachment 4: beamprofdata.zip
Attachment 5: IMG_0258.jpg
  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.

  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.
  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
  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
Attachment 2: 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


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:


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


- 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
Attachment 2: 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
  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.


  • 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
  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


  • 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).


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
Attachment 2: 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
    • Left the room, and started a measurement from spirou with
      • python [path_to_scripts]mokuPhaseMeterTimeSeries.py -c both -d 450 -i -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 (from 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 -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
  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 -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,


Attachment 1: Screenshot_from_2021-03-19_11-09-04.png
Attachment 2: 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?

ELOG V3.1.3-