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ID Date Authorup Type Category Subject
  14685   Fri Jun 21 19:22:40 2019 KojiConfigurationBHDReviving the single OMC BHD design?

I think a Faraday rotator rotates the polarizations in a same way for both forward and backward beam, and it's not like in this figure.
And the transmission through multiple faradays will also be a big issue.

  14686   Fri Jun 21 19:36:26 2019 KojiUpdateIOOIMC diagnostics

The IMC REFL error signal was measured to compare it with the other spectra (if we have).

The blue curve is the in-loop IMC error and the red is the dark noise. So they are not an apple-to-apple comparison. But the red noise is going to be suppressed by the loop, and still the red is below blue. This means that the blue curve is the measured noise rather than the readout noise.

We suspect that the current issue is the PC drive saturation (as usual). Does this indicate that the laser freq noise is actually increased?


Another suspect was that the degradation of the LO level. We used to have the issue of slowly dying ERA-5 (ERA-5SM indeed). The RF levels on the demod board were measured using an active probe.

The LO input: 0dBm, ERA-5 input: -2.7dBm and -2.1dBm for I and Q. I found that the outputs of the ERA-5SM were +10.5dBm and +10.6dBm.
This lead me to replace the chips but the situation was not changed. Then I realized that the LO levels should have been measured with the load replaced from the mixers to a 50Ohm load. Somehow these mixers lower the apparent LO levels. So I decided to say this is OK.

Attachment 1: IMC_error.pdf
  14689   Sun Jun 23 14:43:14 2019 KojiUpdateIOOIMC is locking normally again

Note that I have removed an SR785, an oscilloscope, some SRS instruments from the PSL and PMC last night.

But they (and RF Network Analyzer) were not there when the problem started.

We should record the IMC error (at test point monitor) too? If the IMC locks on Monday too, I'll do it.

  14712   Sun Jun 30 23:52:09 2019 KojiUpdateIOOPMC and IMC locked again, some MEDM maintenance

> For channels corresponding to continuous values (such as say exposure time or the like) changes to abs(1+current_value)

Why abs? Is the current_value is like -5.4321 (for example for the alignment slider), this returns +4.4321 and the suspension will suffer from huge motion (well it will be returned to the original value soon though). 

  14725   Thu Jul 4 10:54:21 2019 KojiSummarySUSSuspension damping recovered, ITMX stuck

So Cal Earthquake. All suspension watchdogs tripped.

Tried to recover the OSEM damping. 

=> The watchdogs for all suspensions except for ITMX were restored. ITMX seems to be stuck. No further action by me for now.

  14727   Fri Jul 5 20:57:04 2019 KojiUpdateSUSAnother M7.1 EQ

[Kruthi, Koji]

Koji came to the lab to align the IMC/IFO, but found the mirrors are dancing around. Kruthi told me that there was M7.1 EQ at Ridgecrest. Looks like there are aftershocks of this EQ going on. So we need to wait for an hour to start the alignment work.

ITMX and ETMX are stuck.

Attachment 1: Screenshot_from_2019-07-05_21-03-06.png
  14728   Fri Jul 5 21:53:10 2019 KojiUpdateSUSAnother M7.1 EQ

- ITM unstuck now
- IMC briefly locked at TEM00

A series of aftershocks came. I could unstick ITMX by turning on the damping during one of the aftershocks.
Between the aftershocks, MC1~3 were aligned to the previous dof values. This allowed the IMC flashing. Once I got the lock of a low order TEM mode, it was easy to recover the alignment to have a weak TEM00.
Now at least temporarily the full alignment of the IMC was recovered.

  14729   Fri Jul 5 22:21:13 2019 KojiUpdateSUSAnother M7.1 EQ

In fact, ETMX was not stuck until the M7.1 EQ today. After that it got stuck, but during the after shocks, all the OSEMs occasionally showed full swing of the light levels. So I believe the magnets are OK.

Attachment 1: Screenshot_from_2019-07-05_22-19-57.png
  14743   Wed Jul 10 14:55:32 2019 KojiUpdateGeneralProjector lightbulb blown out

In fact the projector is still working. The lamp timer showed ~8200hrs. I just reset the timer, but not sure it was the cause of the shutdown. I also set the fan mode to be "High Altitude" to help cooling.

  14744   Wed Jul 10 14:57:01 2019 KojiSummaryCDSChannel recipe for iscaux upgrade

The list of the iscaux channels and pin assignments were posted to google drive.
The spreadsheet can be viewable by the link sent to the 40m ML. It was shared with foteee@gmail for full access.


  • We need
    4 ADC modules
    5 DAC modules
    5 Binary I/O modules
  • Be aware that there are bundled multiple digital I/O channels such as "mbboDirect" and "mbbi".
  • The full db record of the new channels need to be inferred from the existing channels.

Necessary electronics modification

1. D990694 whitening filter modification (4 modules)

This module shares the fast and slow channels on the top DIN96pin (P1) connector. Also, the whitening selector (done by an analog signal per channel) is assigned over 17pin of the P1 connector, resulting in the necessity of the second DSUB cable. By migrating the fast channels, we can swap the cable from the P1 to P2.  Also, the whitening selectors are concentrated on the first Dsub. (See Attachment1 P1)

2. D040180 / D1500308 Common Mode Board

CM servo board itself doesn't need any modification. The CM board uses P1 and P2. So we need to manufacture a special connector for CM Board P2. (cf The adapter board for P1 T1800260). See also D1700058.

3. D990543A1 LSC Photodiode Interface

PD I/F board has the DC mon channels spread over the 16pin limit. P1 21A can be connected to 6A so that we can accommdate it in the first Dsub.
Also the board uses AD797s. This is not necessary. We can replace them to OP27s. I actually don't know what is happening to those bias control, temp mon, enable, and status. These features should be disables at the I/F and the PDs. (See Attachment2 P1)

Attachment 1: D990694-B.pdf
D990694-B.pdf D990694-B.pdf D990694-B.pdf D990694-B.pdf D990694-B.pdf D990694-B.pdf D990694-B.pdf D990694-B.pdf
Attachment 2: D990543A1.PDF
D990543A1.PDF D990543A1.PDF D990543A1.PDF
  14756   Fri Jul 12 18:54:47 2019 KojiUpdateGeneralItem loan: optical chopper from Cryo Lab

Optical chopper borrowed from CryoLab to 40m


  14764   Tue Jul 16 15:17:57 2019 KojiHowToCDSFinal bit bug of the BIO CDS module

Yutaro talked about the BIO bug in KAGRA elog. http://klog.icrr.u-tokyo.ac.jp/osl/?r=9536

I think I made the similar change for the 40m model somewhere (don't remember), but be aware of the presense of this bug.

  14767   Wed Jul 17 17:56:18 2019 KojiConfigurationComputersGave resolv.conf to giada

Kruthi noticed that she could not login to rossa from giada.

I checked /etc/resolv.conf and it was


so obviously it is useless to refer localhost (i.e. giada) as a nameserver.

I copied our usual resolv.conf to giada as following:


search martian

Giada's ssh known_host had unupdated entry for rossa, so I had to clean it up, but after that we can connect to rossa from giada just by "ssh rossa".

Case closed.

  14770   Thu Jul 18 00:51:52 2019 KojiSummaryCDSiscaux electronics modifications

Along with the plan in ELOG 14744, the ISC PD interface and the whitening filter board have been modificed. The ISC PD I/Fs were restored to the crate and the cables were connected. The whitening filteres are still on the electronics bench for some more tests before being returned to the crate.

The updated schematics were uploaded as https://dcc.ligo.org/D1900318 and https://dcc.ligo.org/D1900319

- Modification of the ISC PD interface: Jumpers between DIN96 P1 and P2. Replace all AD797s with OP27. In fact only I/F #1 (the left most)  had total 12 AD797 but the other units already had OP27s.

- Modification of the whitening filter: Jumpers between DIN96 P1 and P2.

Attachment 1: LSC_whitening2.jpg
Attachment 2: LSC_whitening.jpg
  14775   Thu Jul 18 22:34:40 2019 KojiSummaryCDSiscaux electronics modifications

The whitening filter modules have been restored to the crates. The SMA cables have been restored and fastened by a spanner. The ribbon cable to the antialiasing board was also connected. The backplane cables have not been moved from the upper DIN96 connector to the lower one.

Everything is expected to be good, but just keep eyes on the LSC signals as the boards were not quantitatvely tested yet. If you find something suspicious, report on the elog.

  14821   Wed Jul 31 17:57:35 2019 KojiUpdateBHDOMC cavity geometry

4 deg is not an optimized number optimized for criteria, but to keep the cavity short width to 0.1m. But the justification of 4deg is found in Section 3 and 4 of T1000276 on Page 4.


Question for Koji: how is the aLIGO OMC angle of incidence of ~4 degrees chosen? Presumably we want it to be as small as possible to minimize astigmatism, and also, we want the geometric layout on the OMC breadboard to be easy to work with, but was there a quantitative metric? Koji points out that the backscatter is also expected to get worse with smaller angles of incidence.

  14843   Mon Aug 12 21:25:19 2019 KojiUpdateCDSMore bench test of c1iscaux


> Looking through the manual, I found a recommendation (pg10) that the "IN-" terminal of the Acromag ADC units be tied to the "RTN" pins on the same units. I don't know if this preserves the differential receiving capability of the Acromag ADCs

I suppose, we loose the differential capability of an input if the -IN is connected to whatever defined potential. We should check if the channels are still working as a true differential or not.


2. If the multi bit operation is too complicated to solve, we can use EPICS Calc channels to breakout a value to bits and send the individual bits as same as the other individual binary channels.


  14851   Tue Aug 20 19:05:24 2019 KojiUpdateCDSMC1 (and MC3) troubleshoot

Started the troubleshoot from the MC1 issue. Gautam showed me how to use the fake PD/LED pair to diagnose the satellite box without involving the suspension mechanics.

This revealed that the MC1 has frequent light level glitches which are common for five sensors. This feature does not exist in the test with the MC3 satellite box. I will open and check the MC1 satellite box to find the cause of this common glitches tomorrow. MC1 is currently shutdown and undamped.

BTW, at the MC3 test, i found that J2 of the satellite box (male Dsub) has all the pins too low (or too short?). I brought the box outside and found that the housing of this connector was half broken down. The connector was reassembled and the metal parts of the housing was bent again so that the housing can hold the connector body tightly.

The MC3 satellite box was restored and connected to the cables. As I touched this box, it is still under probation.

Attachment 1: Screenshot_from_2019-08-20_17-26-01.png
Attachment 2: Screenshot_from_2019-08-20_17-43-03.png
  14852   Thu Aug 22 12:54:06 2019 KojiUpdateCDSMC1 glitch removed (for now) and IMC locking recovered

I have checked the MC1 satellite box and made a bunch of changes. For now, the glitches coming from the satellite box is gone. I quickly tested the MC1 damping and the IMC locking. The IMC was locked as usual. I still have some cleaning up but will work on them today and tomorrow.

Attachment 1: Result

The noise level of the satellite box was tested with the suspension simulator (i.e., five pair of the LED and PD in a plastic box).

Each plot shows the ASD of the sensor outputs 1) before the modification, 2) after the change, and 3) with the satellite box disconnected (i.e., the noise from the PD whitening filter in the SUS rack).

Before the modification, these five signals showed significant (~0.9) correlation each other, indicating that the noise source is common. After the modification, the spectra are lowered down to the noise level of the whitening filters, and there is no correlation observed anymore. EXCEPT FOR the LR sensor: It seems that the LR has additional noise issue somewhere in the downstream. This is a separate issue.

Attachment 2: Photo of the satellite box before the modification

The thermal environment in the box is terrible. They are too hot to touch. You can see that the flat ribbon cable was burned. The amps, buffers, and regulators generate much heat.

Attachment 3: Where the board was modified

- (upper left corner) Every time I touched C51, the diode output went to zero. So C51 was replaced with WIMA 10uF (50V) cap.

- (lower left area) I found a clear indication of the glitch coming from the PD bias path (U3C). So I first replaced another 10uF (C50) with WIMA 10uF (50V). This did not change the glitch. So I replaced U3 (LT1125). This U3 had unused opamp which had railed to the supply voltage. Pins 14 and 15 of U3 were shorted to ground.

- (lower right corner) Similarly to U3, U6 also had two opamps which are railed due to no termination. U6 was replaced, and Pins 11, 12, 14, and 15 were shorted to ground.

- (middle right) During the course of the search, I suspected that the LR glitch comes from U5. So U5 was replaced to the new chip, but this had no effect.

Attachment 4: Thermal degradation of the internal ribbon cable

Because of the heat, the internal ribbon cable lost the flexibility. The cable is cracked and brittle. It now exposes  some wires. This needs to be replaced. I'll work on this later this week.

Attachment 5: Thermal degradation of the board

Because of the excessive heat for those 20years, the bond between the board and the patten were degraded. In conjunction with extremely thin wire pattern, desoldering of the components (particularly LT1125s) was very difficult. I'd want to throw away this board right now if it were possible...

Attachment 6: Shorting the unused opamps

This shows how the pieces of wires were soldered to ground vias to short the unused opamps.

Attachment 7: Comparison of the noise level with the sus simulator and the actual MC1 motion

After the satellite box fix, the sensor outputs were measured with the suspension connected. This shows that the suspension is moving much more than the noise level around 1Hz. However, at the microseismic frequency there is also most no mergin. Considering the use of the adaptive feedforward, we need to lower the noise of the satellite box as well as the noise of the whitening filters.

=> Use better chips (no LT1125, no current buffers), use low noise resistors, better thermal environment.

Attachment 1: satellite_box.pdf
Attachment 2: before.jpg
Attachment 3: after.jpg
Attachment 4: P_20190821_194035.jpg
Attachment 5: P_20190821_174240.jpg
Attachment 6: P_20190821_194013.jpg
Attachment 7: comparison_satellite_box.pdf
  14853   Thu Aug 22 20:56:51 2019 KojiUpdateCDSMC1 glitch removed (for now) and IMC locking recovered

The internal ribbon cable for the MC1 satellite box was replaced with the one in the spare box. The MC1 box was closed and reinstalled as before. The IMC is locking well.

Now the burnt cable was disassembled and reassembles with a new cable. It is now in the spare box.

The case closed (literally)

  14862   Fri Sep 6 15:12:49 2019 KojiHowToCDSWFS discussion, restarting CDS

Assuming you are at pianosa, /etc/resolv.conf is like

# Generated by NetworkManager

But this should be like


search martian

as indicated in https://nodus.ligo.caltech.edu:8081/40m/14767

I did this change for now. But this might get overridden by Network Manager.

  14865   Fri Sep 6 21:22:06 2019 KojiHowToCDSHow to save c1ioo

Q1 Can we run the machine with the reduced # of cores?

Q2 We might be able to order them quickly. What's the spec and configuration of the DIMMs (like DDR2-667MHz ECC 4GBx4, and even more specs (like Samsung 2GB DDR2 RAM PC2-6400 240-Pin DIMM M378T5663EH3) so that we are to identify the exact spec).

Q3 Can we scavenge the old OMC RT machine or even megatron to extract the memories?

  14870   Tue Sep 10 17:26:49 2019 KojiUpdateCDSD1900068 SR785 accessory box

I picked up a unit of D1900068 SR785 accessory box from Dean's office at Downs. 

Attachment 1: P_20190910_171859_1.jpg
  14877   Fri Sep 13 13:03:35 2019 KojiSummaryCDSDIN 96pin to DSUB37 adapter (single) ready for use

The PCB board of the adapter for DIN 96pin to DSUB37 conversion (single DSUB version) was delivered yesterday and I quickly soldered the connectors.

They are ready for use and stored in a JLCPCB cardboard box on a pile of acromag stuff. (Note that the lacel is written on the box with Sharpie)

Attachment 1: P_20190912_192109.jpg
  14884   Mon Sep 16 19:29:24 2019 KojiUpdateCamerasMC2 trans camera (?) rotated

The left one is analog and 90deg rotated.

See also: This issue tracker

  14892   Tue Sep 17 23:43:34 2019 KojiSummaryCDSAcromag logic checker

For the investigation of the latch logic issue for the CARM CM board, I have made the LED logic checkers with DB breakout boards. They require the pull up voltage supply of +15V because the acromag digital out is a open corrector (well... open "source") output.

The logic from Pin1 to Pin16 of DB37 can be monitored. The DB15 connector is only for monitoring the latch enable logic.

What Gautam and I found with the logic outputs was that the latch logic works fine but occasionally we found that the top 2 bits and the bottom 4bit were processed independently.

Attachment 1: digital_checker.pdf
Attachment 2: IMG_8914.JPG
  14893   Tue Sep 17 23:46:21 2019 KojiUpdateCDSLatch Enable Logic

[Koji Gautam]

We continued to check the latch logic. Today we found that latch.py didn't catch the change of LSB but did for MSB. We determined that this happens when the slider value is chaged between the polling for LSB and MSB.
SInce these two should always be related to a single gain value, latch.py was modified so.

Now we don't observe any logic error for ~100 gain transisitions (see attached).

Attachment 1: Screenshot_from_2019-09-17_23-39-35.png
  14906   Wed Sep 25 20:10:13 2019 KojiUpdateCDSc1iscaux testing

== Test Status ==
Whitening gain switching test
[none] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board

- LO Det Mon channel check

The StripTool template for the test was made:
Then, the RF output of the main Marconi was toggled a few times. -> Confirmed the channels are respopnding. (Attachment 1)

- IPPOS channel check

(0th order check) The StripTool template for the test was made:
Then, the IPPOS QPD was shined with a phone LED. Initially I saw no response of the QPD. It turned out that the IPPOS IF module had no input cable connected. After the connection, all the 4 segments are responding to the phone LED and also the IFO beam.

(more careful check)
I decided to do more careful check of IPPOS. As there was a f~30mm lens on the oplev table, beam was focused such that only one element reacted to the incident beam. The beam power (a few mW) was too strong for a single QPD element, which saturates at ~6, an ND filter of OD0.6 was used to reduce the incident power.

Here are the results:
SEG1 (UPPER LEFT seen from the beam) | C1:ASC-IP_POS_QPD_Seg1_Mon 3.651+/-0.003 (N=10) | Incident Power 2.35+/-0.01 mW, QPD X_Calc (+) Y_Calc (+)

Segment Arrangement
(Seen from the beam)
Epics Channel CH output

Incident Power

Polarity for the
X/Y_Calc channels
SEG1 UPPER LEFT C1:ASC-IP_POS_QPD_Seg1_Mon 3.651+/-0.003
2.35+/-0.01 X(+) / Y(+)
SEG2 LOWER LEFT C1:ASC-IP_POS_QPD_Seg2_Mon 3.607+/-0.002
2.35+/-0.01 X(+) / Y(-)
SEG3 LOWER RIGHT C1:ASC-IP_POS_QPD_Seg3_Mon 3.658+/-0.002
2.37+/-0.01 X(-) / Y(-)
SEG4 UPPER RIGHT C1:ASC-IP_POS_QPD_Seg4_Mon 3.529+/-0.004
2.30+/-0.01 X(-) / Y(+)

After the measurement, the lens and the filter were removed and the beam was adjusted to the center of the QPD.

Attachment 1: testDetectMons_190925.png
Attachment 2: testIPPOS_190925.png
  14907   Thu Sep 26 17:56:28 2019 KojiUpdateCDSsome rebooting

Yesterday (Sep 25) evening: I had to reboot c1psl, c1iool0, and c1aux to recover nominal IMC locking

Today megatron had no response and I had to reboot it with the reset button. MCautolocker and FSSSlow were recovered and the IMC is locking as usual.

  14908   Thu Sep 26 20:09:40 2019 KojiUpdateCDSc1iscaux testing

== Test Status ==

[done] Whitening gain switching test => Some issues found (POP110Q, Whitening3_8 not switching, ASDC overall behavior, REFL33Q needs recheck)
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board

And, the Y-arm lock was recovered! After some alignment work, the Y-arm was locked. The whitening gain for POY11 was +18dB. The servo gain was 0.015 (nominal).
Once the transmission reached 0.8, I could use ASS to align the cavity and the TTs.
The transmission reached just 1.00 at the end. Was the transmission recently normalized? (See attachment 5)

- Whitening Filter Gain Switching Test

Each whitening filters were tested individually. +50mV DC signal was connected to the 8 inputs using an SMA octopus cable.
The existing script ( /cvs/cds/caltech/target/c1iscaux/testScripts/testWhtGain.py ) did not work because cds.getdata failed to fetch all of the data requested. By giving some sleep before start downloading the data, the problem was avoided. Still some truncated data are seen in the result, but StripTools screenshots compliments the missing part.

Whitening Filters #2~4 were a little tricky because the code needed modification so that the spare channels can be tested.
The modified script is stored as /cvs/cds/caltech/target/c1iscaux/testScripts/testWhtGain_190926.py 

Whitening #1: No issue found.

Whitening #2: No issue found. Some of the step plots showed truncation of the data at the end. But this is an artifact of cds.getdat. The striptool show nothing irregular.

Whitening #3: POP110Q and the spare channel (CH8) did not show the reaction. REFL33Q showed some systematic gain deviation. It could just be the offset problem, but needs to be rechecked.

Whitening #4: The DC channels were found to be OK  except for ASDC. ASDC shows earlier saturation. The input was lowered to 5mVDC to avoid saturation in the second trial. The circuit needs to be checked. The spare channels look noisy, but this is because there is no way to turn off the whitening filters for them.

- AA Filter Test

Injected 11kHz 1Vpp sine wave to the whitening filters. The whiter gains were kept at 0dB. If the AA is disabled, the alias of the 11kHz signal appears in the time series.
-> Whitening #1, #3 and #4: the enable/disable worked correctly.
-> Whitening #2 AA
Bbypass no effect. this is an expected behavior.

Attachment 1: Wht1.pdf
Wht1.pdf Wht1.pdf Wht1.pdf Wht1.pdf Wht1.pdf
Attachment 2: Wht2.pdf
Wht2.pdf Wht2.pdf Wht2.pdf Wht2.pdf Wht2.pdf Wht2.pdf
Attachment 3: Wht3.pdf
Wht3.pdf Wht3.pdf Wht3.pdf Wht3.pdf Wht3.pdf Wht3.pdf Wht3.pdf
Attachment 4: Wht4.pdf
Wht4.pdf Wht4.pdf Wht4.pdf Wht4.pdf Wht4.pdf Wht4.pdf Wht4.pdf Wht4.pdf
Attachment 5: lock.png
  14921   Wed Oct 2 01:11:40 2019 KojiUpdateCDSc1iscaux testing

I worked on more troubleshooting of the whitening filters Tuesday afternoon

== Test Status ==

[done] Whitening gain switching test => Remaining issues ASDC overall behavior
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board

Issue 1: POP110Q did not show any gain switching [Resolved]

A DB37 breakout board was connected to the acromag front panel. I found that Ch6 (POP110Q) did not show any differential DC output. I searched around the other pins and found that the corresponding signal showed up on PIn36  instead of Pin35. Opening the front panel revealed that the internal wiring was wrong (Attachment 1). The wire which should have gone to Pin 35 was connected to Pin 36. By correcting the wiring, POP110Q started to show identical behavior to POP110I. (Attachment 2)

Issue 2: LSC reboot [Resolved]

A rough activity around the acromag chassis crashed c1lsc realtime processes (as usual). I ran usual rebooting script /opt/rtcds/caltech/c1/scripts/cds/rebootC1LSC.sh. This successfully restored the status of the vertex RT processes.

Issue 3: REFL33 different behavior between I and Q [Resolved]

REFL33I and Q consistently showed a difference (Attachment 3). The whitening board was pulled out and powered with an extension card. The raw outputs were checked with a function generator and an oscilloscope connected. The outputs for 33I and Q were identical (Attachment 4). So I concluded that the observed difference was an artifact of the checking script.

Issue 4: Whitening 3_8 did not switch at all [Resolved]

To switch the gain stages, each channel of the whitening board takes a DAC output from acromag and convert it into 4bit digital signals. For CH8 of the WF#3, this signal did not reach the instrumentation amplifier AD620. After tracing the signal on the electronics bench, it was found that the CH8 gain input to the DIN96 connector is not conducive to the input of the AD620. As there were no exposed pads between the DIN96 connector and the AD620 input (pin2), a wire was additionally soldered (forgot to take a photo). This solved the gain switching issue as the test result indicates (Attachment 5). The noisiness came from the whitening filter which can not be turned off right now. For this reason, the test of the whitening part is pending too.

The StripTool plot during the overall WF#3 test is shown in Attachment 6.

Issue 5: ASDC behavior [Unresolved]

First of all, at this test, I found that WF#4 was not responding to the gain change at all. This issue was restored by power cycling the acromag chassis (as usual).

The whitening filter #4 was pulled, and the behavior of CH5,6,7,8 (CH8=ASDC) was compared. It was found that the analog outputs were identical and the problem lies further downstream.

Issue 6: Illeagal REFL11 LO cable [Unresolved]

This is a newly found issue. The cable between the LO distributor and the REFL11 demodulator is not the legit solder soaked RG402 coax, but flexible coax (Attachment 7). This cable needs to be replaced in the end. But for today, it was not so that we can have a consistent configuratin as before.

Issue 7: Signature of a damaged POPDC cable [Resolved]

The cable for POPDC cale indicated some damage at the WF#4 side. It was not a complete damage, and therefore the solder coating was added (Attachment 8).

Attachment 1: WF3_wiring.png
Attachment 2: POP110.pdf
Attachment 3: REFL33.pdf
Attachment 4: P_20191001_174548_vHDR_On.jpg
Attachment 5: Whitening3_8.pdf
Attachment 6: Screenshot_WF3_191001.png
Attachment 7: P_20191001_181052_vHDR_On.jpg
Attachment 8: POPDCcable.png
  14932   Thu Oct 3 14:54:33 2019 KojiUpdateGeneralMake the Jenne-laser setup fiber-coupled

I'm afraid that the RF modualtion of the laser is nonlinear and the electrical and optical resoponse is dependent on the LD pumping current and RF input power. So I feel safe if we keep the reference PD. Of course, this is my feeling and it should be quantitatively tested.

  14936   Thu Oct 3 23:15:39 2019 KojiUpdateGeneralMake the Jenne-laser setup fiber-coupled

The 1GHz PD has a bit more flat response, but the laser and the driving network have more frequency dependence as you saw.

  14939   Fri Oct 4 01:57:09 2019 KojiUpdateCDSc1iscaux testing

The AA filter for ASDC was fixed.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[none] CM Board
[none] ALS I/F board

The AA filter for the 4th section of the LSC analog electronics bank (D000076) was pulled out for the test. On the workbench, questionable CH8 was checked. It tuned out that the filter amplifier module for the 8th-order elliptic filter at 7.5kHz was not properly working and exhibited unusual attenuation. This filter module (Frequency Devices Inc D68L8E-7.50kHz) was desoldered and replaced with a module from a spare board. Note that Gautam and I had tried to use this spare board instead of the current one, but it didn't give us any signal for an unknown reason. Since the desoldering required a lot of force and had a risk of damaging the PCB, a socket was made from an IC socket (see Attached 1). This change made CH8 functioning equally to the other channels do.

I took this opportunity to ckech the performance of the AA filters. For each channel, the input signal was injected from J3 using a pomona clip. The output was taken from pin 1, 5, 9, ... of J2. This is the + side of the differential output. The - side just has the equivalent performance but the signal polarity. The digital signals for the AA bypass switches were not connected. Fortunately, this was just fine as it made the anti-aliasing filters engaged.

Attachment 2 shows the transfer functions of all the channels. All the channels showed an identical response (at least visually). The transfer function for CH1 was fitted by LISO. The ZPK values are listed here:

pole 5.2860544577k 503.1473053928m
pole 5.9752193716k 1.0543411596
pole 8.9271953580k 3.5384364788
pole 8.2181747850k 3.4220607928
pole 182.1403534923k 1.1187869426 # This has almost no effect
zero 13.5305051680k 423.6130434049M
zero 15.5318357741k 747.6895990654k
zero 23.1746351749k 1.5412966100M

factor 989.1003181564m
delay 24.4846075283n

Attachment 3 shows the ASD of the output voltage noise measurement. Note the input was shorted for this measurement. The nominal output voltage was found to be 0.1 uV/rtHz and the 1/f noise corner freq was about 100Hz. Only CH3 showed a deviation from the typical values. It looks like this is neither an artifact nor transient noise. Fortunately, nothing is connected to this channel right now.

Attachment 1: P_20191003_172956_vHDR_On.jpg
Attachment 2: TF.pdf
Attachment 3: PSD.pdf
Attachment 4: 191003_AA_Filter.zip
  14942   Sat Oct 5 00:03:21 2019 KojiUpdateCDSc1iscaux testing

[Gautam, Koji]

Input gain part of the CM servo board D1500308 was tested. A couple of problems were detected. One still remains.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[in progress] CM Board
[none] ALS I/F board

We started to test the CM Servo board from the input stages. Initially, DC offsets were provided to IN1 and IN2 to check the gain on the oscilloscope or a StripTool plot. However, the results were confusing, AC measurements with SR785 was carried out in the end. It turned out that both IN1 and IN2 had some issues. IN1 showed an increment of the gain by 2dB every two gain steps, having suggested that the 1dB gain stage had a problem. IN2 showed sudden drop of the signal at the gain +8~+15dB and +24~+31dB, having suggested that a particular 8dB stage had a problem. The board was exposed with the extender and started tracing the signals.

CH1: The digital signal to switch the 1dB stage reached Pin 1A of the DIN96 connector. However, the latch logic (U47 74ALS573) does not spit out the corresponding level for this bit. Note that the next bit was properly working. We concluded that this 74ALS573 had failed and need to be replaced. We have no spare of this wide SOIC-20 chip, but Downs seems to have some spares (see Todd's spare parts list). We will try to get the chip on Monday.

CH2: The stage only used between +8dB and +15dB and between +24dB and +31dB is the +8dB stage (U9 and U2A). I found that the amped output signal did not reach the FET switch U2A (MAX333A). Therefore it was concluded that the opamp U9 (AD829) has an issue. In fact, the amp itself was working, but the output pin was not properly soldered to the pad.  Resoldering this chip made the issue gone. Note that this particular channel has some OP27s soldered instead of AD829. Gautam mentioned that there was some action on the board a few years back to deal with the offset issue. Next time when the board is polled out, I'll take the photos of the board.

Using SR785, the swept sine measurements between 100 and 100kHz were taken for all the gain settings for each channel. Between -31dB and -11dB, the input signal amplitude of 300mV was used. Between -10dB and +10dB, it was reduced to 100mV. For the rest, the amplitude was 10mV. Note that the data for +11dB for CH1 and +2dB for CH2 are missing presumably due to a data transfer issue.

The results are shown in Attachments 1~4.

Attachments 1 and 3 show the gain at each slider value. The measured gain was represented by the average between 1kHz and 10kHz. The missing 1dB every two slide values are seen for CH1. The phase delay at 100kHz is show in the lower plot. There is some delay and delay variation seen but it is in fact less than 1deg at 10kHz (see later) so it's effectfor CM servo (IMC AO path) is minimum. The gain for CH2 tracks the slider value nicely. The phase delay is larger than that of CH1, as expected because of OP27.

Attachments 2 and 4 show the transfer functions. The slider value was subtracted from the measured gain magnitude to indicate the deviation between them. The missing 1dB is obviously visible for CH1 in addition to the overall gain offset of ~0.2dB. CH2 also shows the gain offset of 0.1dB~0.2dB. The phase delay comes into the play around 20kHz particularly at higher gains where the UGF of the AO path is.

gautam: Here is the elog thread for IN2 opAmps going AD829-->OP27. Also, I guess Attachment #1 and #3 x-axes should be "Gain [dB]" rather than "Frequency [Hz]".

Attachment 1: REFL1_GAIN1.pdf
Attachment 2: REFL1_GAIN2.pdf
Attachment 3: REFL2_GAIN1.pdf
Attachment 4: REFL2_GAIN2.pdf
  14947   Tue Oct 8 03:19:14 2019 KojiUpdateCDSFinal incarnation of latch.py

Now with the CM board tested with the signal injected, it turned out that the latch logic was flipped. As the default state locked the digital levels, the buttons other than the mbbo channels were inactive.

By giving 0 to C1:LSC-CM_LATCH_ENABLE, the modification of the digital state is enabled. And with the value of 1, the digital bits on the board is locked.

In order to reflect this, latch.py was modified and now the controls are all activated.

  14948   Tue Oct 8 03:32:42 2019 KojiUpdateCDSCM servo board testing


The logic chips 74ALS573 were replaced. And now the gain sliders are working properly.

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[done] CM Board
[none] ALS I/F board

Last week we found that the logic chip for the REFL1 gain switching was not transmitting the input logic. I went to Downs and obtained the chips. After some inspection some other latch chips were suspicious. Therefore U46, U47, and U48 (#1, #3, and #4 from the top) were replaced. After the replacement, the gain measurements were repeated. This time the test for the AO gain was also performed. Now all three slideres show the gain as expected except for the consistent -0.2dB deficit.

Note that the transfer functions for the REFL gains were measured with the input at IN1 or IN2 and the output at TESTA1. The TFs for the AO gain was measured with the excitation at EXC B, the input at TESTB2 and the output at the SERVO output. The gain and phase variantions for the AO gain at low frequency is the effect of AC coupling existing between the excitation and the servo output.

[Update on Oct 14, 2019]

The measured transfer functions show the phase delay determined by the opamps involved. The phase delay well below the pole frequencies can be represented well by a simple time delay (a phase delay linear to the frequency). Attachment 7 shows the time delay estimated by LISO for each gain setting of each gain stage. REFL2 has particularly large phase delay because of the use of OP27s. The delay is even larger when the gain is high presunmably because of the limited GBW.

Attachment 1: REFL1_2_GAIN1.pdf
Attachment 2: REFL1_2_GAIN2.pdf
Attachment 3: REFL2_2_GAIN1.pdf
Attachment 4: REFL2_2_GAIN2.pdf
Attachment 5: AO_GAIN1.pdf
Attachment 6: AO_GAIN2.pdf
Attachment 7: delay.pdf
  14953   Tue Oct 8 17:59:29 2019 KojiUpdateCDSCM servo board testing (portal)

== Test Status ==

[done] Whitening gain switching test
[done] AA enable/disable switching
[0th order] LO Det Mon channel check
[none] PD I/F board check
[done] QPD I/F board check
[done] CM Board
[none] ALS I/F board

The photos of the latest board can be found as Attachments 3/4

With some input signals, the functionarities of the CM servo switches were tested.

  • Latch logic works. But latch alive signal is missing.
  • IN1 enable/disable, IN2 enable/disable are properly working
  • OUT2 toggle switch for REFL1/REFL2 mon is wokring
  • Boost / Super Boosts are working
  • EXC A enable/disable, EXC B enable/disable switches are working
  • Option 1 and Option 2 now isolate the input when either is enabled (as there is no option board)
  • 79Hz-1.6kHz pole zero pair works fine
  • OUT1 works fine
  • Disable/Enable switch for the fast path works
  • Polarity switch works
  • AO Gain property changes the gain
  • Limitter switch works (Attachments 4/5). The limitter clipps the output at 4~4.5V. The Limitter indicator also works.

After the tests the LSC cables were reconnected (Attachment 6)

Attachment 1: Screen_Shot_2019-10-08_at_18.36.04.png
Attachment 2: CM_Board_asof_191007_1.jpeg
Attachment 3: CM_Board_asof_191007_2.jpeg
Attachment 4: no_limitter.jpg
Attachment 5: with_limitter.jpg
Attachment 6: P_20191008_012442_vHDR_On.jpg
  14955   Tue Oct 8 18:42:39 2019 KojiUpdateCDSCM servo board testing

The boost filters of the CM servo board were tested. Their ZPK models were made.

The transfer functions of the boost filters were measured with the SG output of a SR785 connected to IN1. The IN1 gain was set to be 0dB. The transfer function was taken between the IN1 input and the TEST1A output.
With no boost and normal boost, the input signal amplitude was fixed to 20mVpk. For the other boosts, however, I could expect large gain variation through a single sweep. Therefore automatic SG amplitude tracking was used. The target was to have the output to be 1V with maximum amplitude of 100mV.

Attachment 1 shows the measured transfer functions.

The pole and zero frequencies of the boosts were estimated using LISO. Here the TFs were normalized by the TF of 'no boost' to cancel the delay of the other stages including that of the monitor channel.


ZPK model of Normal Boost:

pole 44.0597566447
zero 4.3927650910k

factor 98.8275377818


ZPK model of Super Boost (State1):

pole 878.5368382789
zero 17.5107366335k
factor 20.0840668188


ZPK model of Super Boost (State2):

pole 714.8112014271
pole 1.0147609373k
zero 13.2470941080k
zero 22.2259701828k

factor 404.5411036031

ZPK model of Super Boost (State3):

pole 886.3650348470
pole 420.4089305781
pole 887.8490768202
zero 8.3635166134k
zero 15.7953592754k
zero 20.5144907279k

factor 8.2051379423k


Attachment 1: boosts.pdf
  14964   Thu Oct 10 23:36:02 2019 KojiUpdateGeneralWednesday cleaning work

[Jon, Yehonathan, Gautam, Aaron, Shruti, Koji]

We get together on Wednesday afternoon for cleaning the lab. Particularly, we collected e-wastes: VME crates, VME modules, old slow control cables, and other old/broken electronics. They are piled up in the office area and the cage outside rioght now (Attachments 1/2). We asked Liz to come to pick them up (under the coordination with either Gautam or Koji). Eventually this will free up two office desks.

Also, we made the acromag components organized in plastic boxes. (Attachment 3)

Attachment 1: P_20191009_165624.jpg
Attachment 2: P_20191009_164740.jpg
Attachment 3: P_20191010_233631.jpg
  14965   Mon Oct 14 16:06:28 2019 KojiUpdateCDSCM servo board testing

CM Board Slow out (digital length control) path transfer function / pole-zero filter pair (79Hz/1.6kHz) transfer function

The excitation was given from EXC A. The denominator was TESTA2, and the numerator was OUT1.

Attachment 1 shows the measured transfer function with and without PZ filter off and on. The PZ filter provides ~26dB attenuation at  high frequency. The output stage has a single order 100kHz LPF and it is visible in the transfer function.

The transfer function without the PZ filter was modelled by LISO as the following PZK representation. There looked a small step in the TF which caused the additional PZ pair (66~67Hz) but has very minor effect in the mag and phase.

pole 66.2720207366
zero 67.2660731875
pole 93.3044858160k

factor -995.5583556921m

The transfer function of the PZ filter was separately analyzed. The TF with the switch ON was normalized by the one with the switch OFF. Thus it revealed the pure effect of the switch. The PZK model of the stage was estimated to be

pole 79.7312926438
zero 1.6395485993k

factor 996.2196584165m

Attachment 1: pole_zero_filter.pdf
  14966   Mon Oct 14 16:19:30 2019 KojiUpdateCDSCM servo board testing

For the CM board modeling purpose, the transfer function from TESTA2 to TESTB2 was needed. (Attachment 1)

The ZPK model of this part is

pole 76.2369881805
zero 77.4655685092
pole 7.0761486105M

factor -993.0593433578m


Attachment 1: testb2.pdf
  14967   Mon Oct 14 16:25:03 2019 KojiUpdateCDSCM servo board testing

The output stage (and AO GAIN stage) of the MC board was modelled. The transfer function was measured with the injection from EXC B. The denominator was TESTB2, and the numerator was SERVO OUT.

This stage is AC coupled by 2x 1st order HPFs. Firstly, this transfer function was measured with AO GAIN set to be 0dB. (Attachment 1)
This TF was used to characterize the cutoffs of the HPF stages, represented as the following ZPK:

zero 1m
zero 1m
pole 6.0502599855
pole 6.0624642854
factor -26.2725046079n

Then the AO GAIN was already measured as seen in [ELOG 14948]. The AO gain TF was then modeled by LISO with the above HPF as the preset. This allows us to characterize the time delay of the AO GAIN part.

Attachment 1: servo_out.pdf
  14968   Mon Oct 14 16:34:42 2019 KojiUpdateCDSCM servo board testing

Input referred offsets on the IN1/IN2 were tested with different gain settings. The two inputs were plugged by the 50 ohm terminators. The output was monitored at OUT1 (SLOW Length Output). The fast path is AC coupled and has no sensitivity to the offset.

There is the EPICS monitor point for OUT1. With the multimeter it was confirmed that the EPICS monitor (C1:LSC-CM_REFL1_GAIN) has the right value except for the opposite sign because the output stage of OUT1 is inverting. The previous stages have no sign inversion. Therefore, the numbers below does not compensate the sign inversion.

Attachment 1 shows the output offset observed at C1:LSC-CM_REFL1_GAIN. There is some gain variation, but it is around the constant offset of ~26mV. This suggested that the most of the offset is not from the gain stages but from the later stages (like the boost stages). Note that the boost stages were turned off during the measurements.

Attachment 2 shows the input refered offset naively calculated from the above output offset. In dependent from which path was used, the offset with low gain was hugely enhanced.

Since the input referred offset without subtracting the static offset seemed useless, a constant offset of -26mV was subtracted from the calculation (Attachment 2). This shows that the input refered offset can go up to ~+/-20mV when the gain is up to -16dB. Above that, the offset is mV level.

I don't think this level of offset by whichever OP27 or AD829 becomes an issue when the input error signal is the order of a volt.
This suggests that it is more important to properly set the internal offset cancellation as well as to keep the gain setting to be high.


Attachment 1: in12_output_offset.pdf
Attachment 2: in12_input_offset.pdf
Attachment 3: in12_input_offset2.pdf
  14970   Mon Oct 14 17:32:28 2019 KojiUpdateCDSPortal Elog entry for the recent CM servo board tests

Updated Circuit Diagram and photos: https://dcc.ligo.org/D1500308-v2

- (1) and (6) of the diagram: TFs with various gain slider values for REFL1/REFL2/AO GAIN [ELOG 14948] (gain values and time delay modeling)
- Switching checks, latest photo of the board, Limiter check  [ELOG 14953]
- (2): Boost transfer functions [ELOG 14955]
- (3): Slow (aka Length) CM output path [ELOG 14965]
- (4): Pole-Zero filter TF [ELOG 14965]
- (5): TF from TESTA2 to TESTB2 [ELOG 14966]
- (6): AC coupling TF of the AO GAIN stage [ELOG 14967]
- (7): AC coupling TF of the IN2 stage on IMC servo board [ELOG 15044]

Slow path = (1)*(2 if necessary)*(3)*(4 if necessary)

Fast path = (1)*(2 if necessary)*(4 if necessary)*(5)*(6)

gautam 20191122: Adding the measured AC coupling of the IN2 input of the IMC servo board for completeness.

Attachment 1: CM_Servo_Diagram.png
  14971   Tue Oct 15 17:19:38 2019 KojiUpdateGeneralWednesday cleaning work

[Liz, Gautam, Chub, Jordan, Koji]

We removed a significant amount of e-waste from the lab. The garbage was moved to the e-waste station in WB SB and are waiting for disposal.

Attachment 1: P_20191015_161711.jpeg
  14978   Fri Oct 18 18:13:55 2019 KojiUpdatesafetyLaser interlock looks OK

I've checked the state of the laser interlock switch and everything looked normal.

  15003   Wed Oct 30 23:12:27 2019 KojiUpdateSUSPRM suspension issues

Sigh... hard loch

  Draft   Wed Nov 6 20:34:08 2019 KojiUpdateIOOEOM resonant box installed



[Mirko / Kiwamu]

 The resonant box has been installed together with a 3 dB attenuator.

The demodulation phase of the MC lock was readjusted and the MC is now happily locked.



We needed more modulation depth on each modulation frequency and so for the reason we installed the resonant box to amplify the signal levels.

Since the resonant box isn't impedance matched well, the box creates some amount of the RF reflections (#5339).

In order to reduce somewhat of the RF reflection we decided to put a 3 dB attenuator in between the generation box and the resonant box.


(what we did)

 + attached the resonant box directly to the EOM input with a short SMA connector.

 + put stacked black plates underneath the resonant box to support the wight of the box and to relief the strain on the cable between the EOM and the box.

 + put a 3 dB attenuator just after the RF power combiner to reduce RF reflections.

 + readjusted the demodulation phase of the MC lock.


(Adjustment of MC demodulation phase)

 The demodulation phase was readjusted by adding more cable length in the local oscillator line.

After some iterations an additional cable length of about 30 cm was inserted to maximize the Q-phase signal.

So for the MC lock we are using the Q signal, which is the same as it had been before.


 Before the installation of the resonant box, the amplitude of the MC PDH signal was measured in the demodulation board's monitor pins.

The amplitude was about 500 mV in peak-peak (see the attached pictures of the I-Q projection in an oscilloscope). Then after the installation the amplitude decreased to 400 mV in peak-peak.

Therefore the amplitude of the PDH signal decreased by 20 %, which is not as bad as I expected since the previous measurement indicated 40 % reduction (#2586).



  15019   Wed Nov 6 20:34:28 2019 KojiUpdateIOOPower combiner loss (EOM resonant box installed)

Gautam and I were talking about some modulation and demodulation and wondered what is the power combining situation for the triple resonant EOM installed 8 years ago. And we noticed that the current setup has additional ~5dB loss associated with the 3-to-1 power combiner. (Figure a)

N-to-1 broadband power combiners have an intrinsic loss of 10 log10(N). You can think about a reciprocal process (power splitting) (Figure b). The 2W input coming to the 2-port power splitter gives us two 1W outputs. The opposite process is power combining as shown in Figure c. This case, the two identical signals are the constructively added in the combiner, but the output is not 20Vpk but 14Vpk. Considering thge linearity, when one of the port is terminated, the output is going to be a half. So we expect 27dBm output for a 30dBm input (Figure d). This fact is frequently oversight particularly when one combines the signals at multiple frequencies (Figrue e). We can avoid this kind of loss by using a frequency-dependent power combiner like a diplexer or a triplexer.

Attachment 1: power_combiner.pdf
ELOG V3.1.3-