The Y arm was locked with the TRY DC signal.
The handing off process is too complicated because there is no path from ALS to the LSC error.
The TRY DC error signal & the gain determination
- The error signal was produced by the operation 1/SQRT(TRY) - OFFSET. The initial offset was -5.
- The sign of the TRY DC error signal depends on which side of the resonance the arm is.
By looking at the strip chart, I determined that the sign is opposite of the ALS.
The ALS had the gain of -25, so the TRY control gain was to be positive.
- From the strip chart on the previous entry , the slope difference between the PDH error and the TRY DC error was x500.
The arm control with POY11 PDH had the gain of 0.2. So the target gain for the TRY DC was determined to be +100.
- The arm was stabilized by ALS. The ALS gain was -25 with FM2/3/5/6/7/10
- YARM configuration: no trigger / no FM trigger / gain =+0 / FM5 ON / OFFSET -5
- Start handing off:
YARM: Turned up the gain to +50
- ALS: Turned off FM6/7
- YARM: Turned on FM6/7
- ALS: Turned off FM2
- YARM: Turned on FM4
- ALS: Turned off FM3/10
- YARM: Turned on FM2/3/8/9 ON
- ALS: Reduced the gain to -15
- YARM: Increased the gain to +70
- ALS: Reduced the gain to 0
- YARM: Increased the gain to +100
HANDING OFF - DONE
Changing the offset
The offset of -5 gave the TRY of <0.1.
The detuning was reduced by giving the offset of -4. TRY went up to ~.1
The offset of -3 made TRY 0.13
The offset of -2 made TRY 0.25
The offset of -1.5 made TRY 0.4. And the arm could not be held by this error signal anymore.
[Annalisa, Manasa, Jenne, Koji]
We are working on the vent preparation.
First of all, there was no light in the interferometer.
Obviously there were lots of IFO activity in the weekend. Some were elogged, some were not.
Annalisa took her responsibility to restore the alignment and the arms recovered their flashes.
The odd thing was that the ASS got instable after we turned down the TRY PD gain from +20dB to +10dB (0dB original).
We increased the TRY gain by factor of 10 (that's the "10dB" of this PDA520. See the spec sheet) to compensate this change.
This made the ASS instable. Anyway we reduced the gain of TRY PD to 0dB. This restored the ASS.
Jenne took some more data for the QPD spectrum calibration.
Link to the vent plan
FE Web view was broken for a long time. It was fixed now.
The problem was that path names were not fixed when we moved the models from the old local place to the SVN structure.
The auto updating script (/cvs/cds/rtcds/caltech/c1/scripts/AutoUpdate/update_webview.cron) is running on Mafalda.
Link to the web view: https://nodus.ligo.caltech.edu:30889/FE/
The spot on the IPANG QPD was checked. The spot is higher than the center and South side of the lens.
Some photos are found below.
The spot on the IPANG steering mirrors in the ETMY chamber was also checked.
It is clipped at the top of the steering mirror. (See attachment 4)
So basically the spot is about 1" above the center of the mirror.
Centering of the oplev beams: done
Recording the OSEM values: done
Low power MC locking
- Rotated HWP right after the laser
- Put a knife edge beam dump at the output of the PBS after the HWP.
- Replaced the PO mirror for the MC refl by an HR mirror.
Input offset from 0 to 0.29
Servo Gain from 10 to 30
=> Transmission 0.84 (1.2W at the MC input) to 0.069 (100mW)
VCO Gain from 25 to 31
MC REFL: Unlocked 3.6 Locked 0.38-0.40
record of the initial state
The MC was manually aligned. The spot positions were measured and it is consistent with the measurements done yesterday.
Full alignment of the IFO was recovered. The arms were locked with the green beams first, and then locked with the IR.
In order to use the ASS with lower power, C1:LSC-OUTPUT_MTRX_9_6 and C1:LSC-OUTPUT_MTRX_10_7 were reduced to 0.05.
This compensates the gain imbalance between TRX/Y siganls and the A2L component in the arm feedback signals.
Despite the IFO was aligned, we don't touch the OPLEVs and green beams to the vented IFO.
Thesedays we were continuously annoyed by unELOGGED activities of the interferometer.
MC2 LOCKIN was left on and has continuously injected frequency noise and beam pointing modulation
during all of the comissioning / vent preparation.
C1:SUS-MC2_LOCKIN2_OSC_FREQ was 0.075
C1:SUS-MC2_LOCKIN2_OSC_CLKGAIN was 99
For more than a week ago we noticed that the curve of the MC WFS stripchart suddenly got THICKER.
MC WFS, arm transmission, beam pointing... everything was modulated.
It was not WFS instability, and it was not the cavity mirrors.
Today I made the investigation and finally tracked down the cause of this issue to be on MC2 suspension.
Then it was found that this LOCKIN was ON.
There is no direct record of this lockin in the frame files.
From the recorded channel "C1:IOO-WFS2-YAW_OUT16" (which is the trace on the StripTool chart on the wall)
It was turned on at July 10th, 2:00UTC (July 9th, 7PM PDT)
After the first flipping, X/Y arms were aligned and locked. Then the ASS aligned the arms.
There was no progress tonight after Jenne left.
I could not find any reasonable fringes of the IFO after 3 hours of optics jiggling.
* I jiggled TT1 and TT2. The slider has not been restored.
We should probably look at the value in the day time and revert them.
(Still this does not ensure the recovery of the previous pointing because of the hysteresis)
* The arms are still aligned for the green.
It's not TEM00 any more because of the vent/drift but the fringe is visible (i.e. eigenaxis is on the mirror)
* As we touched PR3, the input pointing is totally misaligned.
To Do / Plan
* We need to find the resonance of the yarm by the input TTs. Once the resonance is found, we will align the PRM.
* Move the BS to find the xarm resonance.
* Finally align SRM
* It was not possible to find the resonance of the yarm without going into the chamber. Definitely we can find the spot on the ITMY by a card, but we are not sure the beam can hit the ETMY. And the baffles makes the work difficult.
* One possibility is to align the input beam so that the ITMY beam is retroreflected to the PRM. I tried it but the beam was not visible form the camera.
It was not actually easy to see from the entry what signal was taken in what condition but from the shape of the spectra
I had the impression that the ASC & OPLEV signals were measured under the presence of the ASC control.
That is (moderately to say) tricky as the ASC control imprints the angular noise
from unkown mirror on the PRM, and then the oplev observes it. The original stability of the oplev is
obscured by the injection from the servo and the fair comparison of the stability is almost impossible.
So the true comparison between the ASC and oplev signals should be done without the control loop.
We can recover the free running spectrum of the ASC signals by compensating the loop transfer functions
because the ASC signals are the in-loop error signals. The oplev signals should be measured without
the ASC loop engaged.
Prior to the access connector removal, Manasa and I aligned the IFO mirrors.
The arms were locked and aligned by ASS.
[Koji, Manasa, Sujan]
Tomorrow we'll make final checks of the optics inside the chamber.
Then we will pump down the chamber.
I wonder what optics is causing the halo on the oplev beam.
It this comes from any uncoated lens (or similar) it should be identified.
- I suppose the green transmission paths were thoroughly inspected and aligned in prior to the measurement
- Of course it is a BAD idea to use 60Hz as the LO frequency.
- Power spectra should be plotted as "RIN (relative intensity noise)" as the DC of 1 and 100 gives you 100 times different power spectra for the same beam.
Don't forget to subtract the offset from your DC values.
I have a concern about the SRM suspension. The yaw alignment bias produces huge pitch coupling.
This could be a connector issue or the rubbing of the mirror on the EQ stops.
We have the photos of the magnets and they were not touching the OSEMs.
I moved bunch of ezcawrite from the ASS Dither On script to a snapshot file.
This accelerated a half of the "up" time but still switching part is not in the snapshot.
If you find anything wrong with ASS, please notify me.
While Gautam is working on the Xarm green ASS...
The EPICS monitor points for the ASS actuators were added to the ASS model.
This will be used for the offloading the ASS actuations to the alignment biases.
As this modification allowed us to monitor the actuation apart from the dithering,
now we can migrate the ASS actuation to the fast alignment offset on the suspension.
This modification to the offset moving scripts were also done.
- IPANG aligned on the QPD. The beam seems to be partially clipped in the chamber.
- Oplev of the IFO mirrors are aligned.
- After the oplev alignment, ITMX Yaw oplev servo started to oscillate. Reduced the gain from -50 to -20.
Now the SRM Yaw bias in yaw is functional without any strage behavior.
The problem was found at the connector of the flat ribbon cable from the DAC to the cross connect.
I used the extender board to diagnose the SRM coil driver circuit at 1X4.
The UL coil input did not show any sign of voltage no matter how the bias slider was jiggled.
I opened the side panel of the rack and found the signal was absent at the cross connect which relays two flat ribbon cables
for the SRM coil driver. I checked the DAC output with a multimeter. All the bias outputs were OK at the DAC.
Then I opened the IDC connector at the DAC side of the crossconnect as the signal was already missing there.
I found that the flat ribbon cable was a half line shifted from the supposed location.
This resulted a short circuit of the DAQ +/- pins for the SRM UL coil.
I recrimped the connector and now the SRM Yaw slider is back.
This changed the nominal position of the SRM. The new slider values were saved.
PRMI(sb) lock was recovered
- Stared at the time series data of the REFL demod signals, and decided to use REFL165I&Q for the locking.
- Jiggled the demodulation phase of REFL165 and POP110. Changed the servo gains.
- Finally found a short lock. Further optimized the parameters.
- PRM ASC was turned on by giving the identity matrices for the input and output matrices.
Now just hitting the up button is sufficient to engage the ASC servo.
- Under the presence of the ASC, the PRMI is indefinitely locked as before.
- Reacquisition is also instantaneous. (It acquires even if the ASC is left "on".)
- Actually the lock is somewhat robust even when the PRM ASC is not used.
This is VERY GOOD as we can skip one of the steps necessary for the full lock.
Although, the seismic on Friday night is very quiet.
The spot motion at POP seems to be somewhat pitch/yaw mixed, in stead of previous "totally-dominated-by-yaw" situation.
- We are ready to implement ASS for PRM
Demod phase adjustment
- Shook PRM at 580Hz / 100cnt
- Swept the demod phase of REFL165 such that the PRM peak is minimized in the Q signal
- Open DTT. Measured transfer functions between REFL165I and the Q signals of each PD.
- Minimized the PRCL signal coupling in the signals.
- The resolution of the adjustment was ~1deg.
Locking test with PRM/BS
Tried the lock acquisition only with PRM and BS. (cf. http://nodus.ligo.caltech.edu:8080/40m/8816)
This just worked nicely.
Today's locking parameters:
MC Trans: 17500
POP110I (in lock): 150
PRCL Source: REFL165(I) 106deg / 45dB / Normalization SQRT(10 POP110I) / Input MTRX 1.0
PRCL Trigger: POP110I x 1.0 50up 25down
PRCL Servo: G=+3.5 Acq: FM4/FM5 Opr: FM2/FM3/FM6/FM7
PRCL Actuator: PRM +1.0
MICH Source: REFL165(Q) 106deg / 45dB / Normalization SQRT(0.1 POP110I) / Input MTRX 1.0
MICH Trigger: POP110I x 1.0 50up 25down
MICH Servo: G=-10 Acq: FM4/FM5 Opr: FM2/FM3/FM6
MICH Actuator: (ITMX -1.0 / ITMY +1.0) or (BS 0.5 / PRM -0.267)
c1x01 timing issue was solved. Now all of the models on c1iscex are nicely running.
- c1x01 was synchronized to 1PPS in stead of TDS
- C1:DAQ-DC0_C1X01_STATUS (Upper right indicator) was red. The bits were 0x4000 or 0x2bad.
C1:DAQ-DC0_C1X01_CRC_SUM kept increasing
- c1scx, c1spx, c1asx could not get started.
- login to c1iscex "ssh c1iscex"
- Run "sudo shutdown -h now"
sudo shutdown -h now
- Walk down to the x end rack
- Make sure the supply voltages for the electronics are correct (See Steve's entry)
- Make sure the machine is already shutdown.
- Unplug two AC power supply of the machine.
- Turn off the front panel switch of the IO chassis
- Wait for 10sec
- Turn on the IO chassis
- Plug the AC power supply cables to the machine
- Push the power switch of the realtime machine
New AG4395, sn MY41101114 for West Bridge Labs was delivered. For the test purpose it is at the 40m now.
I made a series of tests in order to find anything broken.
Network analyzer test
- RF out / Rch test
RF out directly connected to R input channel.
The received power at the R-ch was measured while the output was swept from 10Hz to 500MHz.
The RF power was changed from -50dBm to +15dBm with +10dBm increment (but the last one).
The attenuator setting was changed from 50dB to 0dB.
=> The configured output power was properly detected by the R channel.
=> RF output is producing the signal properly. R-ch is detecting the produced signal properly.
- Ach/Bch test
Same test as above for Ach and Bch
=> Same result as above
=> A-ch and B-ch are detecting the produced signal properly.
- Transfer function test
Connect a power splitter to the RF out. Detect the split signals by R-ch and A-ch
=> Measurement is at around 0dB +/- 1dB up to 500MHz.
Same measurement for B-ch
=> Same result
=> A/R and B/R indicates proper transfer function measurements.
RF out was split in to two. One was connected to R-ch. The other was connected to A-ch.
The thru response calibration was run.
=> The thru calibration was performed properly.
- Practical tranfer function measurements.
In the above calibration setup, various RF filters were inserted in the Ach path.
The measured data was extracted via GPIB connection.
=> Practical transfer function measurements were performed.
=> GPIB connectivity was confirmed
External reference test
- External 10MHz reference from an SRS frequency counter was connected to Ext Ref In
=> Ext Ref indicator on the screen appeard
=> The internal oscillator seemed to be locked to the external reference in
Spectrum analyzer test
- Measured the signals from DS345 by R/A/B ch
Sinusoidal signal (1V) swept from 10MHz to 30Mhz
=> Corresponding moving peak was detected in each case
- Noise level measurement
R/A/B channels were terminated. The attenuation at each port was set to 0dB.
Frequency span was changed between 500MHz, 10MHz, 100kHz, 1kHz.
=> Noise level of ~10nV/rtHz between 0.1-500MHz was confirmed. All R/A/B channels have the same performance.
As a part of the network analyzer test in the previous entry, the transfer functions of Mini-Circuits filters we have at the 40m were measured.
<<List of the filters>>
- LPF (SMA): SLP1.9, SLP5, SLP21.4, SLP30, SLP50, SLP100, SLP150, SLP750
- LPF (BNC): BLP1.9, BLP2_5, BLP5, BLP30
- BPF (SMA): SBP10.7, SBP21.4, SBP70
- HPF (SMA): SHP25, SHP100, SHP150, SHP200, SHP500
Since the RFM-Dolphin bridges for the ASX model was added to the c1rfm model, c1rfm kept timing-out from the single sample time of 60us.
The model had 19 dolphin accesses, 21 RFM accesses, and 9 shared memory (SHM) accesses.
At the beginning 2 RFM and 2 SHM accesses were moved to c1sus (i.e. they were mistakenly placed on c1rfm).
But this actually made the c1sus model timed out. So the model was reverted.
The current configuration is that the WFS related bridges were accommdated in the c1mcs model.
This made the timing of c1rfm ~40us. So it is safe now.
On the other hand, the c1mcs model has the time consumption of ~59us. This is marginal now.
We need to understand why any RFM access takes such huge delay.
Yesterday we cleaned up the ASX model and screens to have more straight forward structure of the screen
and the channel names, and to correct mistakes in the model/screens.
The true motivation is that I suspect the excess LF noise of the X arm ALS can be caused by misalignment
and beam jitter coupling to the intensity noise of the beat. I wanted to see how the noise is affected by the alignment.
Currently X-end green is highly misaligned in pitch.
- Any string "XEND" was replaced by "XARM", as many components in the system is not localized at the end table.
- The name like "XARM-ITMX" was changed to "XARM-ITM". This makes easier to create the corresponding model for the other arm.
- There was some inconsistency between the MEDM screens and the ASX model. This was fixed.
- A template StripTool screen was created. It is currently saved in users/koji/template as ASX.stp.
It will be moved to the script directory once it's usefulness is confirmed.
The next step is to go to the end table and manually adjust M2 mirror while M1 is controlled by the ASX.
The test mass dithering provides the error signal for this adjustment but the range of the PZT is not enough
to make the input spot position to be controlled. In the end, we need different kind of matching optics
in order to control the spot position. (But is that what we want? That makes any PZT drift significantly moves the beam.)
This is an elog about the activity on Friday night.
- The X arm green beam was aligned with assist of the ASX system.
- M1 PZT alignment was swept while M2 PZT was under the control of ASX.
- Everytime M1 was touched, M2 was restored by manual alignment so that the REFL beam hits the center of the REFL PD.
This way we could recover the lock of TEM00. Once TEM00 is recovered, ASX took care of the alignment of M2
- The error signal used by the cavity dither did not give us a good indication where the optimal alignment is.
- Thus the best alignment of M1 had to be manually scanned. The resulting maximum green transmission was ~0.88
- Once the beam was aligned, the out-of-loop stability of the Xarm was measured.
There has been no indication of the improvement compared to Manasa's measurement taken before our beam alignment.
This disturbance in the MC ASC channels were fixed.
This craziness happened ~10pm last night. Was there any action at the time? >> Sunday-night workers? (RXA: No, Nakano-kun and I left before 9:30 PM)
We found that the signals came from c1ioo. However, restarting, recompiling c1ioo and c1mcs didn't help
to clean up this issue. Just in case we cleaned up the corresponding entries in the ipc file /opt/rtcds/caltech/c1/chans/ipc/C1.ipc
and recomplied c1ioo and c1mcs because these are the channels we touched last week to mitigate the timing out issue of c1rfm.
Incidentally, we fell into a strange mode of the RCG: IOPs could not restart. We ended up running "sudo shutdown -r now"
on each machine (except for c1lsc which was not affected by this issue). This solved the issue.
Even now c1oaf could not be running properly. This is not affecting the IFO operation right now, but we need to look into this issue again
in order to utilize OAF.
- An Aluminum mirror instead of 2" unknown mirror for the pick-off for the rejected beam from the green faraday isolator (Steve)
=> Replaced. To be reviewed
- Faraday mount replacement. Check what we have for the replacement. (Steve)
- The green REFL PD should be closer to the pick-off mirror. (Steve)
=> Moved. To be reviewed
- A beam dump should be placed for the green REFL PD
- Move the green shutter to the place where the spot is small (Steve)
=> Moved. To be reviewed.
- The pole of the PZT mounting should be replaced with a reasonable one. (Steve with Manasa's supervision)
- Tidying up doubling oven cable. Make a hole on the wall. (Steve)
=> Done. To be reviewed.
- Tidying up the PZT cabling (Steve)
- The optics are dirty. To be drag wiped. (Manasa, Masayuki)
As I always tell everyone: Don't use a 10% reflector which produce ghost beams. Use a 90% reflector.
It seems that the PRM violin mode freqs shifted from 625-ish to 640Hz.
The peaks rang up because of the servo.
Once the notch freq was shifted to 640Hz, the violin mode started to decay.
Don't go for a hacky solution. We want to climb a staircase step by step.
Prepare an independent 110MHz demod ports.
To-do: Set up the AS OSA. Also, perhaps temporarily borrow the 110 demod board from POP. We were triggering on POP22 tonight, and that seemed to work okay.
Friday night locking
Much more stable DRMI lock was achieved, partly thanks to the Friday-night quiet seismic,
and partly because of the improved servo gain and LF boosts
I wanted to confirm the enhancement of the 110MHz signal at the AS port.
As the AS110 PD is placed in the CCD path, there is nothing visible with PRMI.
The Thorlabs PD was moved to the main AS path. Now the AS110 PD is receiving 50% of the power.
With PRMI 110MHz peak was -30dBm (As it was fluctuating, anything more precise number did not make sense)
When the DRMI was locked, the peak was enhanced to 0dBm.
The 2f signal comes from the beat between the sidebands.
Thus the amplitude of the intensity is proportional to the power of the sidebands (assuming the +1 and -1 order sidebands have the same amplitude)
-30dBm -> 0dBm means 31.6 times amplitude of the intensity. Therefore the amplitude transmission of the sidebands is 5.6 times more. (Is this true?)
According to the wiki, the AS port thru-put (i.e. power transmission) for the 55MHz sideband is 0.0026 and 0.43 for PRMI and DRMI respectively.
This corresponds to the amplitude difference of ~13. So we still have only half of the sidebands leaking out from the IFO. This could be attributed
to both the smaller PR gain and SR gain.
Same as the one Jenne used the other day. Later I engaged several additional triggers.
The following is the trigger setting I used
MICH: Delay 2 sec, FM1/FM2/FM3/FM6/FM7
PRCL: Delay 0.5 sec, FM2/FM3/FM6
SRCL: Delay 5 sec, FM1/FM2/FM3/FM6
SRCL FM1 was modified from +3dB to +6dB
Once lock is acquired, it lasts tens of minutes. (see the attached striptool chart.)
Even the lock is lost, it reacquires quickly.
The videos to show the lock acquisition and the in-lock stability are attached below.
The AS port beam is very round. It is not so shaky, but some yaw motion is visible.
The mode at the AS port is defined by the SRM, putting a QPD at the AS port would help to
stabilize the spot.
IFO state upon leaving
I left the 40m with the arms aligned, PRM and SRM slightly misaligned, and LSC setting is for the DRMI locking.
- AS110I/Q for triggering
- PRCL/MICH/SRCL normalization
- We should resurrect the IFO config scripts.
- Remove BS->SRCL actuation coupling
- Handing off to 3f signals (preparation for the full lock)
- Improve ALS stability
- SRM ASC: AS QPD for SRM control
Lock Acquisition Video
UL (REFL) / UR (POP)
LL (AS) / LR (PRM Face)
UL (REFL) / UR (POP)
LL (AS) / LR (PRM Face)
What do you mean???
What is the effect of the anti-whitening filter?
You should know that if you use OUT16 channel, the effect of the unwhite filter is not taken into account.
- Do we have an appropriate amplifier?
- True challenge could be to find a feedthrough for the new port. (or to find a space for the amplifier in the box)
- PDXXX channels is on the DC whitening filter module. There could be some modification on this module (like diabling the whitening gain selector).
- We don't have AS11 and AS165, and so far it is unlikely to use AS11. i.e. The feedthrough, the slot on the crate, the whitening, and the channels can be trasnsition from 11 to 110.
I want to amplify that by ~10 dB, to give 9 dBm. Attenuate by 5 dB to get to 4 dBm, then split into 2, giving me 2 110 MHz spigots, each of ~1 dBm.
Thoughts, before I start scrounging parts, and pulling the RF distribution box?
The reason we had the PCIe/RFM system was to test this mixed configuration in prior to the actual implementation at the sites.
Has this configuration been intesively tested at the site with practical configuration?
Attached is a graph of my rough accounting of the intended direct IPC connections between the front ends.
It's hard to believe that c1lsc -> c1sus only has 4 channels. We actuate ITMX/Y/BS/PRM/SRM for the length control.
In addition to these, we control the angles of ITMX/Y/BS/PRM (and SRM in future) via c1ass model on c1lsc.
So there should be at least 12 connections (and more as I ignored MCL).
I personally prefers to give the PCIe card to c1ioo and move the RFM card to c1lsc.
But in either cases, we want to quantitatively compare what the current configuration is (not omitting the bridging by c1rfm),
and what the future configuration will be including the addtional channels we want add in close future,
because RFM connections are really costly and moving the RFM card to c1lsc may newly cause the timeout of c1lsc
just instead of c1sus.
Stable DRMI lock was recovered. The AS110 phase was adjusted. PRCL and MICH were locked with REFL33I and REFL165Q.
Still SRCL is controlled with REFL55Q.
PRMI sensing matrix
Thursday night, Jenne and I found DRMI can not be locked at all. Also the PRMI lock with REFL55 showed change in the optical gain.
In order to investigate what is happening, the PRMI sensing matrix was measured and compared with the previous one taken in the night of 8/26.
It shows that some signals are unchanged, some are partial change, and some are completely different.
My intuition saids something is wierd with the sensing matrix measurement.
Right now I can't trust these plots.
- Jenne and I have adjusted REFL55 demod angle so that REFL55Q has no PRCL. And I have confirmed with DTT that this is still true.
However, the radar chart shows that REFL55Q is almost correct phase for PRCL instead of MICH.
- REFL11 shows the same amplitude and angle as before. But POX11/POY11 shows different MICH angle.
- I have rotated REFL55 demod phase and remearsured the sensing matrix. Evrything else looked same but REFL55.
Since REFL55I&Q were not used for the control for this measurement, what we expect is to see no change of the sensing matrix and
only see the angle of "I"&"Q" rotates. But the result was different from the expectation.
Since no real info was obtained from the sensing matrix, I had to make a fight without any weapon.
After sevral hours of work, stable DRMI lock was recovered.
Basically I gave larger gains to REFL55 signals: REFL55I for SRCL was 100 instead of 1, and REFL55Q for MICH was 2 instead of 0.1.
This was enough to get a second locking. Using this short sections, I have optimized the FM triggers and the gain boosts (i.e. FM1)
as well as the mirror alignment.
Then, PRM ASS was left running during the lock. This actually stabilized the lock a lot.
This made thee lock indefinite.
The demod phase of AS110I was adjusted so that AS110Q fluctuates around zero.
In this condition, the nominal AS110I was 7300 with the whitening gain of 30dB.
Note that the AS110I&Q were also measured with PRMI. With the same phase and gains, AS110I and Q were -35, -170, respectively.
Do we expect to have this phase shift? If I believe these numbers, the aplitude of 110MHz at the optimal phase is 173,
The ratio of AS110 between DRMI and PRMI is 7300/173 = 42. This corresponds to the ratio of the 110MHz sideband power at the AS port.
According to the wiki, this ratio shoud be ~160.
AS110I was in fact glitchy as you can see in the StripTool chart. I wonder this signal is suitable for the normalization or not.
=== SENSING ===
REFL11 -67deg / whitening gain 0dB
REFL33 -20deg / whitening gain 30dB
REFL55 45deg / whitening gain 6dB
REFL165 96deg / whitening gain 45dB
POP110 69deg whitening on / 15dB
POP22 102.2deg whitening on / 21dB
AS110 145deg whitening off / 30dB (seems to be related to AS11 whitening setting)
=== INPUT MATRIX ===
REFL11I x -0.125 => PRCL (REFL33I x 2.5 was also OK)
REFL55I x 100 => SRCL
REFL55Q x 2 => MICH (REFL165Q x 0.1 was also OK)
=== NORMALIZATION / TRIGGER ===
MICH POP22I UP:50 DOWN:10
PRCL POP22I UP:50 DOWN:10
SRCL POP22I UP:50 DOWN:25
=== SERVO FILTERS ===
MICH x -0.8 FM4/5 ON, no limitter
FM Trigger: delay 2sec, FM1 (modified from 6dB to 20dB), FM2, FM3
PRCL x +0.035 FM4/5 ON, no limitter
FM Trigger: delay 0.5sec, FM2/3/6
SRCL x -0.1 FM4/5 ON, no limitter
FM Trigger: delay 5sec, FM1, FM2
=== OUTPUT FILTERS ===
MICH => PRM -0.267 / BS +0.5
PRCL => PRM +1.0
SRCL => SRM +1.0
=== VIOLIN FILTER TRIGGER ===
delay 1sec: FM1/FM2/FM3/FM6
=== ASC/ASS ===
PRM ASC UP:50 DOWN:25
PITCH&YAW: FM1/9 (ALWAYS ON) + FM2/3 (turned on by the up-script)
PRM ASS left turned on for slow tracking
What was the beat freq for each arm?
The HF noise level depends on the frequency of the beat note.
As the BBPD has the freq dependent noise level. (See this entry)
I vote on PRMI+1arm -> PRFPMI
While Manasa, Jenne, and Masayuki are working on the preparing the interferometer, I write the elog for them.
- 6PM-ish: X and Y arms were was locked. They were aligned with ASS.
- PRMI was locked. The PRM was aligned with ASS.
- Jenne went into the lab and aligned the PRM ASC QPD.
- Jenne also aligned all of the oplev spots except for the SRM.
- 6:40PM Then, Manasa and Masayuki checked the out-of-loop stability of the arms.
The X and Y arms have the rms of 2.2kHz and 600Hz, respectively.
The X arm is significantly worse than the Y arm.
Masayuki saved the plot somewhere in his directory.
- 7:20PM X beat: 41.2MHz, Y beat: 14.8MHz
- 7:22PM PRMI locked POP110 115-120
- 7:30PM Lost lock of everything. Start over. Taking the arm alignment.
- 7:45PM start the 2nd trial. PRMI+one arm ready.
- 8:00PM explosion! Lost lock.
- 8:30PM The Xarm ALS is not stable anymore. It loses the control in ~10sec.
We are investigating the out-of-loop stability of the Yarm ALS.
(i.e. Look at the beat note error signal while locking the Yarm with the IR PDH)
PMC aligned. Trans 0.78 -> 0.83
> all of complications of handing off
- ALS error signals transfered to the LSC input matrix.
- Handing off from the ALS to the 1/sqrt(TRX)+offset signal
- Handing off to the RF signal
- And, of course, CM servo.
I calibrated the ALS-OFFSETTER output.
I measured the FSR of cavity in unit of counts. That was 395 counts. Our cavity FSR is 3.8 MHz, so 1 count of the OFFSETTER output is 9.7 kHz.
Really? What cavity length did you use in the calculation?
Yes, the resonance of the 2nd-order sidebands to the IFO screws up the 3f scheme.
2f (~22MHz) and 10f (~110MHz) are at x 5.6 and x 27.9 FSR from the carrier, so that's not the case.
Could we also see how much gain fluctuation of the 3f signals we would experience when the arm comes into the resonance?
You have the data. Why don't you just calculate 1/SQRT(TRX)?
...yeah, you can calculate it but of course you don't have no any reference for the true displacement...
General Remarks on the BBPD
- To form the LC network: Use fixed SMD inductors from Coilcraft. SMD tunable capacitors are found in the shelf right next to Steve's desk.
If the tuning is too coarse, combine an appropriate fixed ceramic SMC C and the tunable C (in parallel, of course)
- L1/C1a/C1b pads are specifically designed for an additional notch
- Another notch at the diode stage can be formed between the middle PD pin (just left of the marking "C3b") to the large GND pad (between C1a/C1b to C3a).
You have to scratch off the green resin with a small flat screw driver (or anything similar)
- A notch at the amplifier stage can be formed between the output of MAR-6SM ("+" marking) and one of the GND pads (left side of the "U1" marking)
- The original design of the PD is broadband. So additional notches on the diode stage provides notches and resonances.
Check if the resonances do not hit the signal frequencies.
- One would think the PD can have resonant feature to reduce the coupling of the undesired signals.
In some sense it is possible but it will be different from the usual resonant tank circuit in the following two points.
* Just adding a parallel L between the cathode and ground does not work. As this DC current should be directed to the DC path,
L&C combo should be added. In fact this actually give a notch-resonance pair. This C should be big enough so that you can ignore it
at the target resonant frequency. Supply complimentary small C if necessary to keep low impedance of the Cs at the target frequency.
(i.e. Check SRF - self-resonant frequency of the big C)
* Since the input impedance of MAR-6SM is 50Ohm, the top of the resonant curve will be cut at 50Ohm. So the resultant shape looks
like a bandpass rather than a resonance.
- So in total, simulation of the circuit is very important to shape the transimpedance. And, consider the circuit can not be formed as simulated
because of many practical imperfections like stray Ls and Cs.
Unfortunately this does not work. These WFSs are not the detectors which we can move freely.
In order to move the WFS detectors, we need the precise design of the Gouy phase for each WFS heads.
Without the design, we can't move the detectors.