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ID Date Authorup Type Category Subject
  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.
 

  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).

  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.

  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]".

  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

[Koji]

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.

  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)

  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

 

  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)

  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

  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

 

  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.

  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.

 

  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.

  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.

  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

 

Quote:

[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.

 

(Background)

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.

  15043   Thu Nov 21 13:14:33 2019 KojiUpdateLSCCM board study

One of the differences between the direct POY and the CM_SLOW POY is the presence of the CM Servo gain stages. So this might mean that you need to move some of the whitening gain to the CM IN1 gain.

  15063   Tue Dec 3 00:10:15 2019 KojiUpdateALSEY uPDH post mixer LPF

I got confused. Why don't we see that too-high-Q pole in the OLTF? 

  15196   Fri Feb 7 02:41:28 2020 KojiUpdateGeneraloffice area temperature

Not sure what's wrong, but the workstation desk is freezing cold again and the room temp is 18degC (64degF).

  15200   Fri Feb 7 19:39:10 2020 KojiUpdateLSCMore high BW POY experiments

This measurement tells you how the gain balance between the SLOW_CM and AO paths should be. Basically, what you need is to adjust the overall gain before the branch of the paths.

Except for the presence of the additional pole-zero in the optical gain because of the power recycling.

You have compensated this with a filter (z=120Hz, p=5kHz) for the CM path. However, AO path still don't know about it. Does this change the behavior of the cross over?

If the servo is not unconditionally stable when the AO gain is set low, can we just turn on the AO path at the nominal gain? This causes some glitch but if the servo is stable, you have a chance to recover the CARM control before everything explodes, maybe?

  15219   Fri Feb 21 13:02:53 2020 KojiUpdateALSPDH error signals?

Check out this elog: ELOG 4354

If this summing box is still used as is, it is probably giving the demod phase adjustment.

  15252   Wed Mar 4 21:02:49 2020 KojiUpdateElectronicsMore cabling removed

We are going to replace the old Sun c1ioo with a modernized supermicro. At the opportunity, remove the DAC and BIO cards to use them with the new machines. BTW I also have ~4 32ch BIO cards in my office.

  15267   Wed Mar 11 21:03:57 2020 KojiUpdateBHDSOS packages from Syracuse

I opened the packages send from Syracuse.

- The components are not vacuum clean. We need C&B.
- Some large parts are there, but many parts are missing to build complete SOSs.

- No OSEMs.
- Left and right panels for 6 towers
- 3 base blocks
- 1 suspension block
- 8 OSEM plates. (1 SOS needs 2 plates)

- The parts looks like old versions. The side panels needs insert pins to hold the OSEMs in place. We need to check what needs to be inserted there.

- An unrelated tower was also included.

  15280   Wed Mar 18 22:10:41 2020 KojiUpdateVACMain vol pressure jump

I was in the lab at the time. But did not notice anything (like turbo sound etc). I was around ETMX/Y (1X9, 1Y4) rack and SUS rack (1X4/5), but did not go into the Vac region.

  15293   Thu Apr 2 22:19:18 2020 KojiUpdateCDSC1AUXEY wiring + channel list

We want to migrate the end shutter controls from c1aux to the end acromags. Could you include them to the list if not yet?

This will let us remove c1aux from the rack, I believe.

 

  15301   Mon Apr 13 15:28:07 2020 KojiUpdateGeneralPower Event and recovery

[Larry (on site), Koji & Gautam (remote)]

Network recovery (Larry/KA)

  • Asked Larry to get into the lab. 

  • 14:30 Larry went to the lab office area. He restarted (power cycled) the edge-switch (on the rack next to the printer). This recovered the ssh-access to nodus. 

  • Also Larry turned on the CAD WS. Koji confirmed the remote access to the CAD WS.

Nodus recovery (KA)

  • Apr 12, 22:43 nodus was restarted.

  • Apache (dokuwiki, svn, etc) recovered along with the systemctl command on wiki

  • ELOG recovered by running the script

Control Machines / RT FE / Acromag server Status

  • Judging by uptime, basically only the machines that are on UPS (all control room workstations + chiara) survived the power outage. All RT FEs are down. Apart from c1susaux, the acromag servers are back up (but the modbus processes have NOT been restarted yet). Vacuum machine is not visible on the network (could just be a networking issue and the local subnet to valves/pumps is connected, but no way to tell remotely).

  • KA imagines that FB took some finite time to come up. However, the RT machines required FB to download the OS. That made the RTs down. If so, what we need is to power cycle them.

  • Acromag: unknown state

The power was lost at Apr 12 22:39:42, according to the vacuum pressure log. The power loss was for a few min.

  15303   Tue Apr 14 23:50:06 2020 KojiUpdateGeneral40m power glitch recovery

[Koji / Gautam (Remote)]

Lab status

  • Gray Panel: The lab AC was off. Turned on all three (N/S, CTRL RM, E/W)
  • The control room AC was running.

Work stations

  • Control Room: All the control machines were running. We knew that nodus/chiara/fb were running
  • 1X6/7:
    • JETSTOR was making beeping sound. “Power #1 failed””power #2 failed”
    • Optimus & megatron were off -> turned on -> up and running now
  • 1X1/2:
    • Power cycled the netgear at the top of the IOO rack (maybe not necessary)
    • Turned on c1ioo -> up and running now
  • 1X4/5: Rebooted c1sus / c1lsc -> up and running now
  • 1X9: Rebooted c1iscex -> up and running now
  • 1Y4: Rebooted c1iscex -> up and running now

Vacuum status

  • Looked like everything was running as if it did not see the power glitch
  • TP1 normal: Set speed 33.6k rpm / Actual speed 33.6k rpm 
  • TP2 normal: 66k rpm / PTP2 16.0 mtorr
  • TP3 normal: 31k rpm / PTP3 45.4mtorr
  • P1 LOW / P2 1.7mtorr / CC2 1.1e-6 / P3 7.6e-2 / P4 LO
  • Annuli: 2.7~3torr
  • CC1 9.6e-6 / SUPER BEE 0.9mtorr

C1VAC recovery

  • c1vac was alive, but was isolated from the martian network
  • Checked the network I/F status with /sbin/ifconfig -a
    • eth0 had no IP
    • eth1 had the vac subnet IP (192.168.114.9)
  • Ran sudo /sbin/ifdown eth0 then  sudo /sbin/ifup eth0
  • The I/F eth0 started running and c1vac became visible from martian
  • Later checked the vacuum screen: The pressure values and valve statuses looked normal.
    The interlock state was “running”. The system state was “unrecognized”.

End RTS recovery 

  • The end slow machines (auxex and auxey) were already running
  • Restarting end RT models:
    • c1iscey -> rtcds start --all
    • c1iscex -> rtcds start --all
  • Confirmed that the models can dump the SUSs

Vertex RTS recovery

  • We wanted to use the reboot script. (/opt/rtcds/caltech/c1/scripts/cds/rebootC1LSC.sh)
  • c1susaux​​
    • To be safe, we wanted to bring c1susaux first.
    • c1susaux does not make the network I/Fs up automatically upon reboot.
      -> Connect an LCD display / keyboard / mouse to c1susaux
      -> Ran sudo /sbin/ifup eth0 and sudo /sbin/ifup eth1
    • Now c1susaux is visible from martian.
    • Login c1susaux and ran:  
      sudo systemctl start modbusIOC.service 
      -> c1susaux epics is up and running now
    • ...Meanwhile c1susaux lost its eth1 somehow. This made the slow values of 8 vertex sus all zero
      -> Ran sudo /sbin/ifdown eth1 and sudo /sbin/ifup eth1 again on c1susaux ->  this resolved the issue
  • c1psl
    • Login c1psl and ran:  
      sudo systemctl start modbusIOC.service 
      -> c1psl epics is up and running now
  • Prepared for the rebooting script
    • Ran /opt/rtcds/caltech/c1/scripts/cds/rebootC1LSC.sh
    • Rebooting was done successfully. All the suspensions looked free and healthy.
    • Burtrestored c1susaux (used Apr 12 21:19 snapshot)

Hardware

  • PSL laser / Xend AUX laser / Yend AUX laser were off -> turned on
  • The PMC was immediately automatically locked.
  • The main marconi was off -> forgot to turn on
  • The end temp controllers for the SHG crystals were on but not enabled -> now enabled

RTS recovery ~ part 2

  • FB: FB status of all the RTS models were still red
  • Timing: c1x01/2/3/5 were 1 sec behind of FB and c1x04 was 2 sec behind
  • -> Remedy:  https://nodus.ligo.caltech.edu:8081/40m/14349
    • Software rebooting of FB
    • Manually start the open-mx and mx services using
    • sudo systemctl start open-mx.service 
    • sudo systemctl start mx.service
    • Check that the system time returned by gpstime matches the gpstime reported by internet sources. e.g. http://leapsecond.com/java/gpsclock.htm
    • Manually start the daqd processes using
      sudo systemctl start daqd_*
  • This made all the FB(FE) indicators green!
  • Ran the reboot script again -> All green!

IMC recovery

  • The IMC status was checked
  • No autolocker, but it could be manually locked. i.e. MC1/2/3 were not so much misalignment
  • Autolocker/Slow FSS recovery along with https://nodus.ligo.caltech.edu:8081/40m/15121
    • sudo systemctl start MCautolocker.service
    • sudo systemctl start FSSSlow.service
  • Both of them failed to run
  • Note by Gautam: The problem with the systemctl commands failing was that the NFS mount points weren’t mounted. Which in turn was because of the familiar /etc/resolv.conf problem. I added chiara to the namespace in this file, and then manually mounted the NFS mount points. This fixed the problem.
    Now the IMC is locked and the autolocker is left running.

Burt restore

  • Used Apr 12 21:19 snapshot
  • c1psl
  • c1alsepics/c1assepics/c1asxepics/c1asyepics
  • c1aux/c1auxex/c1auxey/
  • c1iscaux/c1susaux
  • This made REFL and AS beams back to the CCDs. As has small fringes.
  • Y arm has small IR flashes as well as green flashes.

JETSTOR recovery

  • JETSTOR was beeping. 
  • Shutdown megatron
  • Followed the instruction https://nodus.ligo.caltech.edu:8081/40m/13107
  • This stopped beeping. Waiting for JETSTOR to come up -> In a minute, JETSTOR display became normal and all disks showed green.
  • Bring megatron back up again

N2 bottle

  • The left N2 bottle was empty. The right one had 1500PSI.
  • Replaced the left bottle with the spare one in the room.
  • Now the left one 2680PSI and the right one 1400PSI.

Closing

  • Closed PSL/AUX laser shutters
  • Turned off the lights in the lab, CTRL room, and the office.

Remaining Issues

  • [done] MCAutoLocker / FSSSlow scripts are not running
  • The PRM alignment slider has no effect (although the PRM is aligned…) -> SLOW DAQ frozen???
  • JETSTOR is not mounted on megatron [gautam mounted Jetstor on megatron on 4/18 at 2pm]
  15317   Sat May 2 02:35:18 2020 KojiUpdateALSASY M2 PZT damaged

Yes, we are supposed to have a few spare PI PZTs.

  15327   Tue May 12 20:16:31 2020 KojiUpdateLSCRelative importance of losses in the arm and PRC

Is \eta_A the roundtrip loss for an arm?

Thinking about the PRG=10 you saw:
- What's the current PR2/3 AR? 100ppm? 300ppm? The beam double-passes them. So (AR loss)x4 is added.
- Average arm loss is ~150ppm?

Does this explain PRG=10?

 

  15340   Wed May 20 19:34:58 2020 KojiUpdateGeneralITM spares and New PR3 mirrors transported to Downs for phasemap measurement

Two ITM spares (ITMU01/ITMU02) and five new PR3 mirrors (E1800089 Rev 7-1~Rev7-5) were transported to Downs for phasemap measurement

  15358   Wed May 27 17:41:57 2020 KojiUpdateLSCPower buildup diagnostics

This is very interesting. Do you have the ASDC vs PRG (~ TRXor TRY) plot? That gives you insight on what is the cause of the low recycling gain.

  15359   Wed May 27 19:36:33 2020 KojiUpdateLSCArm transmission RIN

My speculation for the worse RIN is:

- Unoptimized alignment -> Larger linear coupling of the RIN with the misalignment
- PRC TT misalignment (~3Hz)

Don't can you check the correlation between the POP QPD and the arm RIN?

  15360   Wed May 27 20:14:51 2020 KojiUpdateLSCLock acquisition sequence

I see. At the 40m, we have the direct transition from ALS to RF. But it's hard to compare them as the storage time is very different.

  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:
https://nodus.ligo.caltech.edu:30889/40m_phasemap/#E1800089
 

  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.

  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.

  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.

ELOG V3.1.3-