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ID Date Authorup Type Category Subject
  15369   Wed Jun 3 03:29:26 2020 KojiUpdateLSCLock acquisition update portal

Woo hoo!

Which 1f signals are you going to use? PRCL has sign flipping at the carrier critical coupling. So if the IFO is close to that condition, 1f PRCL suffers from the sign flipping or large gain variation.

  15374   Thu Jun 4 00:21:28 2020 KojiSummaryCOCITM spares and New PR3 mirrors transported to Downs for phasemap measurement

GariLynn worked on the measurement of E1800089 mirrros.

The result of the data analysis, as well as the data and the codes, have been summarized here:

  15377   Thu Jun 4 21:32:00 2020 KojiUpdateSUSMC1 Slow Bias issues

We can limit the EPICS values giving some parameters to the channels. cf https://epics.anl.gov/tech-talk/2012/msg00147.php

But this does not solve the MC1 issue. Only we can do right now is to make the output resister half, for example.

  15381   Mon Jun 8 12:49:07 2020 KojiUpdateBHDAstigmatism and scattering plots

Can you describe the mode matching  in terms of the total MM? Is MM_total = sqrt(MM_vert * MM_horiz)?

  15394   Fri Jun 12 01:23:32 2020 KojiUpdateVACPumpspool UPS needs battery replacement

1. I agree that it's likely that it was the temp signal glitch.
Recom #2: I approve to reopen the valves to pump down the main volume. As long as there is no frequent glitch, we can just bring the vacuum back to normal with the current software setup.

2. Recom #1 is also reasonable. You can use simple logic like if we register 10 consecutive samples that exceed the threshold, we can activate the interlock. I feel we should still keep the temp interlock. Switching between pumping mode and the normal operation may cause unexpected omission of the interlocks when it is necessary.

3. We should purchase the UPS battery / replacement rotary TIP seal. Once they are in hand, we can stop the vacuum and execute the replacement. Can one person (who?) accomplish everything with some remote help?

4. The lab temp: you mean, 12degC swing with the AC on!?


  15396   Fri Jun 12 17:32:40 2020 KojiUpdateVACPumpspool UPS needs battery replacement

Jon and Koji remotely supported Jordan's resetting the TP2 controller.

Here is the instruction by Jon
From the operator's console in front of the vac rack:
  1. Open a terminal window (click the LXTerminal icon on the desktop)
  2. Type "control" + enter to open the vac controls screen
  3. Toggle all the open valves closed (edit by KA: and manually close RV2 by rotating the gate valve handle )
  4. Turn OFF TP2 by clicking the "Off' button. Make sure the status changes and the rotation speed falls to zero (you'll also hear the pump spinning down) 
  5. The other pumps (TP1, TP3) can be left running
  6. Once TP2 has stopped spinning, go to the back of the rack and locate the ethernet cable running from the back of the TP2 controller to the IOLAN server (near the top of the rack). Disconnect and reconnect the cable at each end, verifying it is firmly locked in place.
  7. From the front of the rack, power down the TP2 controller (I don't quite remember for the Agilent, but you might have to move the slider on the front from "Remote" to "Local" first)
  8. Wait about 30 seconds, then power it back on. If you had to move the slider to shut it down, revert it back to the "Remote" position.
  9. Go back to the controls screen on the console. If the pump came back up and is communicating serially again, its status will say something other than "NO COMM"
  10. Turn TP2 back on. Verify that it spins up to its nominal speed (66 kRPM)
  11. At this point you can reopen any valves you initially closed (any that were already closed before, leave closed)

TP2 was stopped and at this moment the glitches were gone. Jordan powercycled the TP2 controller and we brought up the TP2 back at the full speed.
However, the glitches came back as before. Obviously we can't go on from here, and we've decided to stop the recovery process here today.

- We left TP1/2/3 running while the valves including RV2 were closed.

- When Jordan is back in the lab next week, we'll try to use TP3 as the backing of TP1 so that we can resume the main volume pumping.

- Currently, TP3 does not have interlocking and that is a risk. Jon is going to implement it.

- Meanwhile, we will try to replace the controller of TP2. We are supposed to have this in the lab. Ask Chub about the location.

- Once we confirm the stability of the diagnostic signals for TP2, we will come back to the nominal pumping scheme.

Attachment 1: Screen_Shot_2020-06-12_at_17.22.23.png
  15398   Fri Jun 12 19:23:56 2020 KojiUpdateVACPumpspool UPS needs battery replacement

The vacuum safety policy and design are not clear to me, and I don't know what the first and second defense is. Since we had limited time and bandwidth during the remotely-supported recovery work today, we wanted to work step by step.

The pressure rising rate is 20mtorr/day, and turning on TP3 early next week will resume the main-volume pumping without too much hustle. If you need the IFO time now, contact with Jon and use backing with TP3.

  15401   Tue Jun 16 13:05:36 2020 KojiUpdateCOCITM spares and New PR3 mirrors transported to Downs for phasemap measurement

ITMU01 / ITMU02 as well as the five E1800089 mirrors came back to the 40m. Instead, the two ETM spares (ETMU06 / ETMU08) were delivered to GariLynn.
Jordan worked on transportation.

Note that the E1800089 mirrors are together with the ITM container in the precious optics cabinet.

Attachment 1: 40m_Optics.jpg
  15440   Mon Jun 29 20:30:53 2020 KojiUpdateSUSMC1 sat-box de-lidded

Sigh. Do we have a spare sat box?

  15470   Sat Jul 11 18:24:30 2020 KojiUpdateLSCMC2 coils need DC balancing?

> Can't we offload this DC signal to the laser crystal temperature servo?
No. PSL already follows the MC length. So this offset is coming from the difference between the MC length and the CARM length.
What you can do is to offload the MC length to the CARM DC if this helps.

  15477   Tue Jul 14 01:55:03 2020 KojiUpdateLSCLocking with POX for CARM

The usual technique is that keeping the IFO locked with the old set of the signals and the relative gain/TF between the conventional and new signals are measured in-lock so that you can calibrate the new gain/demod-phase setting.

  15486   Wed Jul 15 19:51:51 2020 KojiUpdateGeneralEmergency light on in control room

It happened before too. Doesn't it say it has occasional self-testing or something?

  15518   Wed Aug 12 20:14:06 2020 KojiUpdateCDSTiming distribution slot availability

I believe we will use two new chassis at most. We'll replace c1ioo from Sun to Supermicro, but we recycle the existing timing system.

  15519   Wed Aug 12 20:15:42 2020 KojiUpdateElectronicsNumber of the beast

Grrr. Let's repair the unit. Let's get a help from Chub & Jordan.

Do you have a second unit in the lab to survive for a while?

  15520   Wed Aug 12 20:16:52 2020 KojiUpdateElectronicsPhotodiode inventory

When I tested Q3000 for aLIGO, the failure rate was pretty high. Let's get 10pcs.

  15522   Thu Aug 13 13:35:13 2020 KojiUpdateCDSTiming distribution slot availability

The new dolphin eventually helps us. But the installation is an invasive change to the existing system and should be done at the installation stage of the 40m BHD.

  15551   Tue Sep 1 01:49:49 2020 KojiUpdateElectronicsTeledyne AP1053 etc were transported

Teledyne AP1053 etc were transported from Rich's office to the 40m. The box is placed on the shelf at the entrance.

My record tells that there are 7 AP1053 in the box. I did not check the number this time.

Attachment 1: 20200831203756_IMG_9931.jpg
Attachment 2: 20200831203826_IMG_9932.jpg
Attachment 3: 20200831205126_IMG_9934.jpg
  15559   Sat Sep 5 14:28:03 2020 KojiUpdateGeneralLO beam: Fiber coupling work

2PM: Arrived at the 40m. Started the work for the coupling of the RF modulated LO beam into a fiber. -> I left the lab at 10:30 PM.

The fiber coupling setup for the phase-modulated beam was made right next to the PSL injection path. (See attachment 1)

  • For the alignment of the beam, the main PSL path, including the alignment of the 2" PO mirror, has not been touched.
  • There are two PO beams with the optical power of 0.8mW (left) and 1.6mW (right). Both had been blocked but the right one was designed to be used for PSL POS and ANG. For the fiber coupling, the right beam was used.
  • The alignment/mode-matching work has been done with a short (2m?) fiber patch cable from Thorlabs. The fiber is the same as the one used for LO delivery.
  • I tried to have a mode-matching telescope in the LO path. I ended up having no lens for the best result. The resulting transmitted power is 1.21mW out of 1.64mW incident (~74%). These powers were measured with the Ophir power meter. (Note that Thorlabs' fiber power meter indicated 1.0mW transmission.)

Some notes

  • After the PSL activity, the IMC locking was checked to see if I messed up the PSL alignment. It locks fine and looks fine.
    • The input shutter (left closed after Jon's vacuum work?) was opened.
    • The alignment was not optimal and had some pitch misalignment (e.g. TEM03).
    • After some MC SUS alignment, the automatic locking of TEM00 was recovered. Mainly MC3 pitch was moved (+0.17).
    • I've consulted with Gautam and he thinks this is with the level of regular drift. The AS beam was visible.
  • The IMC and MI were moving so much, but this seemed just the usual Saturday night Millikan shake.
  • During the activity, the PSL HEPA was turned up to 100 and it was reverted to 33 after the work.
  • I have been wearing a mask and gloves throughout the work there.
Attachment 1: 20200905212254_IMG_9938.JPG
  15563   Tue Sep 8 01:31:43 2020 KojiUpdateBHDA first look at RF44 scheme

- Loose fiber coupler: Sorry about that. I could not detect something was loose there, although some of the locks were not tightened.

- S incident instead of P: Sorry about that too. I completely missed that the IMC takes S-pol.

  15568   Thu Sep 10 15:56:08 2020 KojiUpdateGeneralHEPA & Particle Level Status

- PSL HEPA was running at 33% and is now at 100%
- South End HEPA was not on and is now running
- Yarm Portable HEPA was not running and is now running at max speed: the power was taken beneath the ITMY table. It is better to unplug it when one uses the IFO.
- Yend Portable HEPA was not running and is now running (presumably) at max speed

Particle Levels: (Not sure about the unit. The convention here is to multiply x10 of the reading)

Before running the HEPAs at their maximum
9/10/2020 15:30 / 0.3um 292180 / 0.5um 14420

(cf 9/5/2020 / 0.3um 94990 / 0.5um 6210)
After running the HEPAs at their maximum
The number gradually went down and now became constant at about half of the initial values
9/10/2020 19:30 / 0.3um 124400 / 0.5um 7410

  15580   Sat Sep 19 01:49:52 2020 KojiUpdateGeneralM4.5 EQ in LA

M4.5 EQ in LA 2020-09-19 06:38:46 (UTC) / -1d 23:38:46 (PDT) https://earthquake.usgs.gov/earthquakes/eventpage/ci38695658/executive

I only checked the watchdogs. All watchdogs were tripped. ITMX and ETMY seemed stuck (or have the OSEM magnet issue). They were left tripped. The watchdogs for the other SUSs were reloaded.

  15582   Sat Sep 19 18:07:35 2020 KojiUpdateVACTP3 RP failure

I came to the campus and Gautam notified that he just had received the alert from the vac watchdog.

I checked the vac status at c1vac. PTP3 went up to 10 torr-ish and this made the diff pressure for TP3 over 1torr. Then the watchdog kicked in.

To check the TP3 functionality, AUX RP was turned on and the manual valve (MV in the figure) was opened to pump the foreline of TP3. This easily made PTP3 <0.2 torr and TP3 happy (I didn't try to open V5 though).

So the conclusion is that RP for TP3 has failed. Presumably, the tip-seal needs to be replaced.

Right now TP3 was turned off and is ready for the tip-seal replacement. V5 was closed since the watchdog tripped.

Attachment 1: vac.png
Attachment 2: Screen_Shot_2020-09-19_at_17.52.40.png
  15584   Sat Sep 19 18:46:48 2020 KojiUpdateGeneralHand soap

I supplied a bottle of hand soap. Don't put water in the bottle to dilute it as it makes the soap vulnarable for cotamination.

  15585   Sat Sep 19 19:14:59 2020 KojiUpdateGeneralITMX released / ETMY UR magnet knocked off

There were two SUSs which didn't look normal.

- ITMX was easily released by the bias slider -> Shake the pitch slider and while all the OSEM values are moving, turn on the damping control (with x10 large watchdog threshold)

- ETMY has UR OSEM 0V output. This means that there is no light. And this didn't change at all with the slider move.
- Went to the Y table and tried to look at the coils. It seems that the UR magnet is detached from the optic and stuck in the OSEM.

We need a vent to fix the suspension, but until then what we can do is to redistribute the POS/PIT/YAW actuations to the three coils.

Attachment 1: IMG_6218.jpeg
  15595   Tue Sep 22 16:29:30 2020 KojiUpdateGeneralControl Room AC setting for continuous running

I came to the lab. The control room AC was off -> Now it is on.

Here is the setting of the AC meant for continuous running

Attachment 1: P_20200922_161125.jpg
  15597   Tue Sep 22 23:16:54 2020 KojiUpdateGeneralHEPA Inspection

Gautam reported that the PSL HEPA stopped running (ELOG 15592). So I came in today and started troubleshooting.

It looks like that the AC power reaches the motors. However, both motors do not run. It looks like the problem exists in the capacitors, the motors, or both.
Parts specs can be found in the next ELOG.

Attachment 1 is the connection diagram of the HEPA. The AC power is distributed by the breaker panel. The PSL HEPA is assigned to use M22 breaker (Attachment 2). I checked the breaker switch and it was (and is) ON. The power goes to the junction box above the enclosure (Attachment 3). A couple of wires goes to the HEPA switch (right above the enclosure light switch) and the output goes to the variac. The inside of the junction box looked like this (Attachment 4).

By the way, the wires were just twisted and screwed into a metal threaded (but isolated) caps (Attachment 5). Is this legit? Shouldn't we use stronger crimping? Anyway, there was nothing wrong with the caps w.r.t the connection for now.

I could easily trace the power up to the variac. The variac output was just fine (Attachment 6). The cord goes from the variac to the junction box (and then HEPAs) looked scorched. The connection from the plug to HEPAs was still OK, but this should be eventually replaced. Right now the cable was unplugged after the following tests for the safety reason.

The junction box for each HEPA unit was opened to check the voltage. The supply voltage came to the junction boxes and it was just fine. In Attachments 8 & 9, the voltages look low but this is because I just turned the variac only a little.

At the (main) junction box, the resistances of the HEPAs were checked with the Fluke. As the HEPA units are connected to the AC in parallel, the resistances were individually checked as follows.

South HEPA SW North HEPA SW Resistance
OFF LO 5 Ohm
LO OFF 7 Ohm

The coils were not disconnected (... I wonder if the wiring of South HEPA was flipped? But this is not the main issue right now.)

By removing the pre-filters, the motors were inspected Attachments 10 & 11. At least the north HEPA motor was warm, indicating there was some current before. A capacitor was connected per motor. When the variac was tuned up a bit, one side of the capacitor could see the voltage. I could not judge which has the issue between the capacitor and the motor.

Attachment 1: 0_PSL_HEPA.pdf
Attachment 2: 1_Breaker_Panel.JPG
Attachment 3: 2_Junction_Box.JPG
Attachment 4: 3_Junction_Box_Inside.JPG
Attachment 5: 4_Junction_Box_Inside_2.JPG
Attachment 6: 5_Variac_100%.JPG
Attachment 7: 6_VariAC_to_HEPA.JPG
Attachment 8: 7_North_HEPA_IN.JPG
Attachment 9: 8_South_HEPA_IN.JPG
Attachment 10: 9_North_Prefilter_Removed.JPG
Attachment 11: 10_South_Prefilter_Removed.JPG
  15598   Tue Sep 22 23:17:51 2020 KojiUpdateGeneralHEPA Inspection

Dimensions / Specs

- HEPA unit dimentions
- HEPA unit manufacturer
- Motor
- Capacitor

Attachment 1: A_HEPA_Dimention.JPG
Attachment 2: B_HEPA_Company.JPG
Attachment 3: C_North_HEPA_Spec.JPG
Attachment 4: D_South_HEPA_Spec.JPG
Attachment 5: E_Motor_Spec.JPG
Attachment 6: F_Cap_Spec.JPG
  15600   Wed Sep 23 10:06:52 2020 KojiUpdateVACTP2 running HOT

Here is the timeline. This suggests TP2 backing RP failure.

1st line: TP2 foreline pressure went up. Accordingly TP2 P, current, voltage, and temp went up. TP2 rotation went down.

2nd line: TP2 temp triggered the interlock. TP2 foreline pressure was still high (10torr) so TP2 struggled and was running at 1 torr.

3rd line: Gautam's operation. TP2 was isolated and stopped.

Between the 1st line and 2nd line, TP2 pressue (=TP1 foreline pressure) went up to 1torr. This made TP1 current increased from 0.55A to 0.68A (not shown in the plot), but TP1 rotation was not affected.

Attachment 1: Screen_Shot_2020-09-23_at_10.00.43.png
  15612   Mon Oct 5 00:53:16 2020 KojiUpdateBHDSingle bounce interferometer locked



  15616   Wed Oct 7 13:06:27 2020 KojiUpdateGeneralPresence in the lab

Tue evening from 4pm~6pm, Koji made a social distant tour for Anchal. We were present around the PSL/AS/ETMX tables.

  15621   Thu Oct 8 18:40:42 2020 KojiUpdateComputer Scripts / ProgramsFinesse GUI

Is it better than Luxor? https://labcit.ligo.caltech.edu/~jharms/luxor.html

  15625   Wed Oct 14 13:28:04 2020 KojiUpdateCOCITM/ETM spares in Downs

The two ITM spares and two ETM spares are together stored in the optic storage (B110) at Downs. c/o Liyuan and GariLynn

Attachment 1: IMG_3073.jpeg
  15630   Thu Oct 15 20:00:23 2020 KojiSummaryGeneralHEPA AC cord replacement

The AC cord from the PSL HEPA variac to the junction box was replaced.
Now the HEPA is running at 70%

Showed up at the 40m at 7pm


  • Closed the PSL shutter.
  • Closed the innolight shutter
  • Turned off the HEPA mains switch
  • Checked the HEPA fan rating: 115V 4.5A.
  • Brought the thickest power cord from the wall stock: the rating is 125V 15A. This should sufficiently hold two HEPAs.

Cable Replacing

  • Rechecked the wire connection. The new cord has green/black/white wires. And the colors agree with the color of the wires in the junction box.
  • Removed the existing cord.
  • Attached the new cord.
  • Checked the variac AC plug. The terminals in the plug look normal and the AC plug looked sufficiently rigid.
  • Checked the connection again. = OK


  • Turned on the HEPA mains switch
  • VairAC turned to 70%
  • Checked the air flow - The HEPA fans are sucking the air = OK

Closing the work

  • Closed the junction box.
  • Cleaned up the roof
  • Opend the innolight shutter
  • Opened the PSL shutter
  • Locked the PMC
  • Locked the IMC  - found the transmission was ~80% of the pre-work due to misalignment of the PMC
  • Aligned the PMC - this recovered the IMC REFL of ~5.2 when the IMC was unlocked

Leaving the 40m at 9:30pm

Memo: 40m wiring/Mask/Camera/Red Pitaya/Particle Counter

Attachment 1: P_20201015_200732.jpg
Attachment 2: P_20201015_200752.jpg
Attachment 3: P_20201015_202615.jpg
Attachment 4: P_20201015_204234.jpg
  15633   Mon Oct 19 15:38:42 2020 KojiUpdateElectronicsLoan: A file binder "40m wiring diagram"

I'll bring a file binder "40m wiring diagram" to home at the next chance.
There is another one on the shelf in the control room.

(I thought I put it in my bag, but it looks like that I left it somewhere around the fax area)

  15634   Mon Oct 19 15:40:02 2020 KojiUpdatePEMAlaska EQ M7.5

Alaska M7.5 20:54UTC https://earthquake.usgs.gov/earthquakes/eventpage/us6000c9hg/executive

I looked at the suspensions. The watchdogs have not been tripped.

IMC was locked but continually shaken. (and occasional unlock)

  15635   Tue Oct 20 20:12:18 2020 KojiSummaryGeneralDJI OSMO Pocket Camera Kit

I set up an action cam (DJI OSMO Pocket) and brought it back to the 40m. The kit is now placed in the control room cabinet together with the Canon DSLR.

I might have left the USBC chaging cable at home this time. Will bring it back next time.-> The cable was returned to the kit on Oct 23rd.

Attachment 1: 20201020200929_IMG_0173.JPG
  15641   Fri Oct 23 16:41:06 2020 KojiUpdateIOOExcess laser freq noise investigation

[Koji, Rana]

We wanted to track down the excess noise seen in MC_F and other places (see the previous report by Gautam)

Setup1: The IMC was locked and MC_F signal between 500 and 1500Hz was observed. The DTT template was saved as /users/Templates/MC/MCF_noise_201023.xml

- Suspected mech resonance/jitter coupled with clipping or any other imperfections. Poked the various optics and optomechanics on the table. Basically no change. If we tap the laser chassis and the optics close to the laser source, we occasionally unlocked the IMC

- When we touched (lifted) the Innolight controller box from the shelf, for the first time we saw a significant change in the shape of the noise spectrum. The peak around the 700Hz shited towards lower frequency by a few %. Other peaks have no obvious change in the shapes and the heights.

- While observing the MC_F signal on the laptop, we went to the back of the laser controller. Placing a hand close to the fan clearly changes the peak frequency lower. By temporarily disconnecting the fan from the power supply for a short moment, the 700Hz peak could be eliminated. We also tried to see the noise level with the slow thermal servo and diagnosis DB cable disconnected, but we didn't see any significant change of the noise level.

Setup 2: Using the ALS phase tracker, we can observe the relative freq noise of the PSL laser and the ETMY AUX laser without any servo involved. This way we can freely disconnect any cables from the lasers. The measurement template for DTT was saved as /users/Templates/ALS/Y_ALS_FINE_PHASE_OUT_102320.xml

- Noise spectrum before disconnecting the cable (REF0, RMS REF1)

- The Fast PZT input to the PSL was disconnected => This made all the peaks (including the 700Hz) disappeared (REF2, RMS REF3)

- The Fast PZT input was restored as before, then the chain was disconnected at the input of the HV PZT driver (Thorlabs) => Again, this made the peaks disappeared (REF4, RMS REF5)

- The chain was disconnected at the input of the TTFSS box => Again, this made the peaks disappeared (REF6, RMS REF7)

- Disconnected the demod input and the AO cables from the IMC servo board => This made the peaks came back (REF8)

- Disconnected all the input/peripheral cables from the IMC servo board except for the connection to the TTFSS box => Still the excess noise was observed  (REF9)

- In addition to the above, the cable to the FSS box was disconnected but the ground was still touching the MC servo board => This made the peaks disappeared (REF10)

The conclusion is that the noise is injected from the main circuit of the IMC servo board.

Next time we will check if the backplane connection is doing something wrong. Also, we'll test if the presence of the RF signals does something bad to the IMC board via EMI and RFI.

We have reverted the connection and tested if we lock the IMC and Y arm. ==> We saw at least they were locked for a short period. The things are still stabilizing, but left them turned on so they keep trying to lock automatically for the night.

Attachment 1: plot.pdf
  15642   Fri Oct 23 19:01:57 2020 KojiSummaryPEMPSL Particle Counter kit removed from the table

The particle counter on the 40m PSL was removed. The package was made together with the OMC lab particle counter (see the packing list below).

The kit was picked up by Radhika for a python code to read out the numbers.

=== Packing List ===

  • MET ONE 227A particle counter
    • used at the 40m. It has the particle reading and the temperature reading.
  • Power supply adapter (AC/DC) for 227A
    • Caution: It is not compatible with GT-321.
  • MET ONE GT-321
    • I found another type of particle counter in West Bridge.
  • Power supply adapter (AC/DC) for GT-321. (Labeled "for GT-321")
    • Caution: It is not compatible with 227A.
  • DB9 cable for GT-321
  • Air Filter G3111
    • When you run a particle counter attach this filter instead of the dust collecting cup to keep the air in take of the particle counter clean. This should keep the particle level down to zero.
Attachment 1: P_20201022_173529.jpg
Attachment 2: P_20201022_173419.jpg
  15643   Mon Oct 26 13:35:58 2020 KojiUpdateIOOExcess laser freq noise investigation

In fact, the problem was the grounding issue (presumably on the IOO racks).
A temporary differential receiver at the TTFSS side was built using an SR560 and a few ponoma cables. This removed the structures ~850Hz.

The MC Servo Output was disconnected from the TTFSS box and monitored with SR785. The 850Hz structure was kept visible no matter what cables, including all the acromag DB cables, were removed. This made me suspicious about the measurement setup. The SR785 was connected to an AC power strip under the SP table and this was too far from the IOO rack.

The SR785 was connected to the AC power strip on 1X2, and now the difference becomes clear. No matter if the acromag cables are connected or not, the connection (particularly ground connection) between the MC servo module and the TTFSS box causes the MC servo output contaminated. (Comparison between Blue and Orange of Attachment #1). During the measurement, the EPICS switch for the fast path was disengaged (=no signal) and the VCO gain (...so called. It's just the MC Servo Gain) was set to be 0dB.

To test if the differential receiving of the MC Servo Output at the PSL helps to reduce this noise, I've built a simple (hacky) differential receiver using an SR560. (Attachment #2)
This kept the noise level same as the disconnected case (Comparison between Green and Orange of Attachment #1, I don't think the difference between them is not significant), while the IMC is locked as before.
Note that we can see that the 36kHz line was significantly reduced. Did we remove this annoying noise?

After talking with Gautam, we decided to leave this configuration while the SE-Diff cable was replaced with a more robust one. (See Attachment #3)

The PSL laser frequency performance was evakluated in the following two ways as we did last week:
1) Use the beat frequency of the free running PSL and the Y-end laser (Attachment #4). The PSL shutter was closed and thus the IMC was not locked.
2) Use the IMC MCF while the IMC was locked. (Attachment #5)

For both cases, the improvement was confirmed.

I also tried to check the reported issue by Gautam on this elog. He used 1Hz BW, but I cheated with 16Hz BW and 10x12.8kHz span PSDs. (Attachment #6)

For the measurement, IN1 GAIN of the IMC Servo was set to be 0dB and the OUT2 was switched to monitor the IN1 noise, while IN1 was terminated by a 50Ohm.

As I mentioned above, the AC power of SR785 was taken from a 1X2 power strip. Is this the reason for the power line forest look less severe compared to the previous case???
Anyway, I tried to use the same differential receiving technique (but with gain of x100) to see if this helps. The differential receiver helped to reduce the structure above 50kHz. The floor noise level was observed to be higher. I didn't pursue this any further, but the forest of the power line looked like a part of the measurement noise. This is indicative that the grounding condition on 1X2 is really not great and we need to review the configuration of the acromag grounding.

Attachment 1: MC_Servo_Output.pdf
Attachment 2: 20201026135735_IMG_0175.jpg
Attachment 3: 20201026153435_IMG_0176.jpg
Attachment 4: Screen_Shot_2020-10-26_at_1.15.54_PM.png
Attachment 5: Screen_Shot_2020-10-26_at_1.35.19_PM.png
Attachment 6: MC_Servo_Error_Mon.pdf
  15646   Wed Oct 28 09:35:00 2020 KojiUpdateCDSRFM errors

I'm starting the model restarts from remote. Then later I'll show up in the lab to do more hard resets.
==> It seems that the RFM errors are gone. Here are the steps.

  1. Shutdown all the watchdogs
  2. login to c1iscex. Shutdown all the realtime models: rtcds kill --all
  3. login to c1iscey. Shutdown all the realtime models: rtcds kill --all
  4. run scripts/cds/rebootC1LSC.sh on pianosa
  5. reboot c1iscex
  6. reboot c1isxey
  7. Wait until all the machines/models are up by the script
  8. restart c1iscex models
  9. restart c1iscey models
  10. some IPC errors are still visible on the CDS status screen. Lauch c1daf and c1oaf


Attachment 1: Screen_Shot_2020-10-28_at_10.06.00.png
  15649   Wed Oct 28 20:42:53 2020 KojiUpdateGeneralVent Prep
  1. Two arms / BS / PRM / SRM were aligned. (Attachment 1)
  2. IMC was aligned by WFS and the WFS offsets were offloaded.
  3. Suspension Status Snapshot (Attachment 2)
  4. Oplevs are aligned (Attachment 3)
  5. Xarm green was aligned in the daytime. Xarm green refl DC (C1:ALS-X_REFL_DC_OUTPUT) was 620 (aligned) ~1300 (drifted). When unlocked, it was 3750.
  6. Yarm green: I saw no flash. We don't have functional PZT alignment since the ASY M2 PZT got broken. I went to the Yend. Something funky is going on with the Yend green. I struggled to have any flash of the cavity. The apertures were not so precise. I finally got TEM00 locked, but the modematching seems exteremely low (like 1/1000?). Basically I saw no power reduction of the refl when the cavity is locked. So at least the cavity was locked but we might need to revisit when we open the chamber
    ==> Gautam thinks it was not like that. So he will check the green alignment tomorrow (Thu).
  7. Item checking: I familialized myself with the yend crane operation. Today I learned that there is a power switch on the wall (Attachment 4). The yend has two heavy door storages (Attachments 4/5). The slings to lift the heavy door are in the crane cabinet along with the y arm (Attachment 6). I didn't yet try to find the "hammer" to hit the door if the o-ring stuck too strong, although that's optional.
  8. We want to reduce the PSL power. But Gautam wants to use the arm locking with the nominal power, it will be done tomorrow by him.
  9. The last thing is to check the green trans power. I noticed that the green trans beams are blocked by an HWP for the BHD LO path on the PSL table. (Attachment 7)
    The HWP was moved and the process was recorded in the movie (Attachment 8). The fiber output was monitored by the BHD DC (aka AS110 DC) with the AS path blocked. The fiber output of 22.6mV (offset -2.5mV) was improved tio 29.1mV after the HWP move and the alignment adjustment.
  10. Now the green transmissions are visible by the green PDs. Attachment 9 shows the trans and ref of each green beams with and without locking to TEM00. The questionable green TRY was ~0.3. If we compare this with the histrical data (Attachment 10), it is about 1/4 of the value in the past. It's not too crazy but still quite low.

At this point, I'm leaving the lab. All the suspensions (incl SRM) are aligned. PSL/GRX/GRY shutters were left open.

Attachment 1: Screen_Shot_2020-10-28_at_19.42.27.png
Attachment 2: Screen_Shot_2020-10-28_at_19.42.38.png
Attachment 3: Screen_Shot_2020-10-28_at_20.42.26.png
Attachment 4: P_20201028_222839.jpg
Attachment 5: P_20201028_223020.jpg
Attachment 6: P_20201028_223212.jpg
Attachment 7: 2020-10-28-233038.jpeg
Attachment 8: HWP_moving.mp4
Attachment 9: Screenshot_from_2020-10-29_01-04-06.png
Attachment 10: Screenshot_from_2020-10-29_01-16-53.png
  15655   Mon Nov 2 17:13:19 2020 KojiUpdateGeneralPlan for OMC chamber

I believe the mirror next to IM1 is for the green beams to be delivered to the PSL table. I think we still want to keep it. Otherwise, the plan looks fine.

  15665   Sun Nov 8 23:24:29 2020 KojiUpdateGeneralVent activities today

> I didn't bother to align the green beams to the arm cavities or re-center the Oplevs - is this necessary? It is a step in the pre-close up checklist, so maybe we should do it... The green transmission does reach the PSL table...

I don't think so. The beam is reaching the PSL, so we have no motivation to change the green alignment. Regarding the oplev, the green refl should come back to the PDH PD and this gives us additional beam reference. As soon as we find the green resonance after the pumping, we can tweak the green axis so that the spots on the mirrors become reasonable (as well as the green trans CCD on the PSL table).


  15667   Tue Nov 10 11:31:13 2020 KojiUpdateGeneralPumpdown

Main volume pressure as of 11:30AM 2020/11/10

Attachment 1: Screen_Shot_2020-11-10_at_11.30.21.png
  15676   Thu Nov 12 15:40:42 2020 KojiUpdateElectronicsMore systematic noise characterization

Yes. The datasheet has a recommendation circuit with 10uF caps. Companies are careful to show reproducible, reliably functional circuit examples on datasheets. So, if the caps are there you should try to replicate the design.


Additional bypass capacitors? I use 0.1 uF, 700V DC ceramic capacitors as bypass capacitors close to the leads of the PA95, as is recommended in the datasheet. Can adding a 10uF capacitor in parallel provide better filtering? I'm not sure if one with compatible footprint and voltage rating is readily available, I'll look around.

  15685   Mon Nov 23 14:52:10 2020 KojiUpdateBHDBHD MMT Optics delivered

Basically, they repeated our specs and showed the coating performances for HR/AR for 10deg P and PR/AR for 45deg P. There is no RoC measurement by the vendor.
Nevertheless, their RoC (paper) specs should be compared with our request.

  15687   Mon Nov 23 23:27:43 2020 KojiSummaryASCQ3000 characterization

Last week and this week I've been working on the characterization of the Q3000 QPDs. The QPDs were named 81, 82, 83, and 94.

  • Dark current [OMC LAB ELOG 402]: All the segments looked similar and acceptable except for the seg1 of #82. It has a smaller reverse breakdown voltage (~6V) but even this is an acceptable level.
  • Impedance [OMC LAB ELOG 403]: All the segments showed a ~300pF junction capacitance with no reverse bias. This looks quite normal.
  • Dark noise [OMC LAB ELOG 404]: All the segments showed ~5pA/rtHz dark noise above 1Hz.

My recommendation is to use #81 and #84 as they have similar dark current characteristics between the segments. But basically, all the QPDs look fine.

The actual junction capacitance and the RF dark noise should be characterized by the actual WFS head circuit.

The QPD packages were labeled and returned to Gautam to be implemented in the WFS heads.

gautam: S/N #84 was installed as the AS WFS QPD. The remaining 3 are stored in the clean cabinet at EX (where the rest of the RF photodiodes are).

  15702   Thu Dec 3 13:55:52 2020 KojiUpdateASCElectrical LO signal for AS WFS

I got a bit confused by your description.

The demod board claims that the nominal power at each LO port is 10dBm. So we want to give at least 16dBm to the (external?) 4way power splitter, but we only have 15dBm. As you said, the actual LO power reaching the FET mixier (PE4140) is the level of ~20dBm. But you said the requirement for the mixer is -7dBm. So are you proposing to reduce the LO level (slightly) than the LIGO recommendation because the minimum for PE4140 is -7dBm?
If that's the message, then I can say "yes". We supply 8~9dBm to the LO ports instead of 10dBm. I suppose the mixers don't care about this level of reduction.

Looking at my original post [40m ELOG 11817], the necessary modification is much larger than you have indicated in your post (as yours is the modification of my modification plan.)
If you do your modification you have to deal with the components rearrangement in the chassis. I think you can still accomplish it as you are going to remove an amplifier and gain the space from it.

The main RF line still has 5dBm Attn. How about to insert another 3dB power splitter there and create a spare 55MHz port for the future use?

Before doing any modification you should check how much the distributed powers are at the ports.
Also your modification will change the relative phase between 11MHz and 55MHz.
Can you characterize how much phase difference you have between them, maybe using the modulation of the main marconi? And you might want to adjust it to keep the previous value (or any new value) after the modification by adding a cable inside?


  15705   Thu Dec 3 21:14:38 2020 KojiUpdateASCElectrical LO signal for AS WFS

Let's use RG405 for better shielding. It is not too stiff. The bending  (just once) does not break the cable.

Are you going to full replacement of the 55MHz system? Or just remove the 7dBm and then implement the proposed modification for the 55MHz line?

  15707   Fri Dec 4 03:02:40 2020 KojiUpdateASCElectrical LO signal for AS WFS

1. That's true. But we are already in that regime with the Var attn at 0dB, aren't we? We can reduce the input to the amp by 1-2dBm sacrificing the EOM out by that amount (we can compensate this for the demo out by removing the 1dB attn).

2. Not 100% sure but one possible explanation is that we wanted to keep the Marconi output large (or as large as possible) to keep the SNR between the signal and the noise of the driver in Marconi. The attenuator is less noisy compared to the driver noise.

3. My guess is that theoretically we were supposed to have 13dBm input and 20dBm output in design. However, the actual input was as such.  We can restore it to the 13dBm input.

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