I have recalibrated the REFL signals.
I first adjusted the demod phases until the I-signals lined up with the I-phase in the sensing matrix plot:
I then balanced the ITM drives by pushing on -1*ITMX and +1.015*ITMY, and seeing a minimum of MICH actuation in the I-phase of REFL55 (the PD I was locking with).
I then took a nice long measurement with DTT, and measured the peak heights in I and Q for each REFL diode. I was driving PRM with 100 cts at 675.1Hz, and ITMX with 1000 cts at 452.1 Hz (and matching ITMY drive, to make pure MICH). Knowing these numbers, and the actuator calibrations (PRM elog 8255, ITMs elog 8242), I know that I was driving PRCL by ~4.3 pm, and MICH by ~23 pm.
For the I-phase calibrations, I find the peak height at the PRCL drive frequency, and divide 4.3 pm by that height. For the Q-phase calibrations, I find the peak height at the MICH drive frequency, and divide 23 pm by that height.
This gives me the following calibrations:
Calibration [picometers / count]
REFL 11 I
REFL 11 Q
REFL 33 I
REFL 33 Q
REFL 55 I
REFL 55 Q
REFL 165 I
REFL 165 Q
My calibrated REFL spectra then looks like:
Last night we noticed an excess in the GUR1Z seis BLRMS on the StripTool. It was in the 0.1 - 0.3 Hz band. The rumor in the control room was that "this kind of noise has been showing up at night recently".
AS it turns out, this was not some environmental noise around the 40m at night, but instead its some internal servo oscillation in the GUR1 Z channel. In the Guralp seismometers, each channel is a different mechanical sensor (unlike the STS or T240), so when a single channel gets noisy it doesn't always implicate the others.
My guess is that the oscillation came from the Z channel needing to be recentered. I power cycled the interface box just now. The oscillation had already gone away, but I thought this might reduce the excess noise. Maybe it did, but the effect is tiny. You can see in the oscillation reference that the low frequency noise is high, but in the new trace its still kind of high. Needs to be re-centered correctly with the paddle. Or add a centering button to the interface box.
I have measured the sensing matrix at a variety of PRCL offset values.
During this each measurement, I also took a 20 second average of the POP 2f signals and the ASDC signal:
All of this data was taken during a single lock stretch.
If / when I do this again, I want to go out to larger offsets. I won't take as many points, but I do want to see how far I can go before I lose lock, and what the phase separation looks like at larger offset values (this time, I stopped at +700 counts which is about 0.7nm, to start checking the negative values. MC has been unhappy, so I wasn't able to take very many negative offset values.)
I conclude that these sensing matrix measurements do see changes in the phase separation with PRCL length offset (what we saw / said yesterday), but that they do not line up with Q's simulation from this afternoon in elog 9671.
The simulation says that we shouldn't be seeing large phase changes until we get out to several nanometers, however the measurement is showing that we get large phase chnages with picometer scale offsets. Yesterday, Rana and I said that the offsets due to RAM were small (of order picometer), and that they were therefore likely not important (elog 9668). However, now it seems that the RAM is causing significant length offsets which then cause poor MICH/PRCL phase separation.
To Do List:
* Confirm MIST simulation with Optickle.
* Look at sensing matrix data pre-lockins (in the raw sensors).
* Check that there is no clipping anywhere in the REFL path (at least out of vacuum), and that the beam is sufficiently small on all 4 REFL diodes.
* Calculate the new PRC g-factor with the new length.
I've asked Manasa and Q to have a look at the MC in the morning. Rana and I have found it to be slightly uncooperative in relocking after a lockloss.
We have found that just letting the autolocker go doesn't seem to work very well, and sometimes the MC just doesn't want to re-lock. Closing the PSL shutter or disabling the autolocker for a few minutes (5ish) doesn't do anything, but leaving it closed for a long time (30 ish minutes) helps a lot. The MC will relock immediately after a nice long break.
The MC is happy (but only for this tiny snapshot in time and most probably will go dysfunctional again as it has been for several months, as of this writing)
....fb timing issue happened again.
I thought that it was the thing that Koji and I saw the other day, where it was individual front end computers that had lost ntp sync, since it wasn't every core on every computer that was red, but reconnecting to the ntp server on c1lsc didn't do anything. I then tried reconnecting to the ntp server on fb, and that fixed things right up. Annoying.
We had an oplev tuning party this afternoon. What we have learned is that we don't have a lot of intuition yet on tuning loops. But, that was part of the point - to build some intuition.
I took responsibility for the PRM, and Vivien took ITMX. I think, in the end, all changes were reverted on ITMX, however Vivien took some data to try and make a computer-generated controller. Before we got started, I locked and aligned the PRMI, and we centered the PRMI-relevant oplevs.
I moved my "boost bump" around a bit, to do more at higher frequencies, but had to sacrifice some of the "oomph", since it was starting to eat up too much phase at my UGF of ~8Hz. I also made the stack resonant gain higher Q and lower height so that it didn't eat so much phase. In the end, I have 25 degrees of phase margin, which isn't really great, but I do win a factor of 2 around 2 and 3 Hz. Also, now I'm able to engage the 3.2 resgain at all, whereas with the previous filter shape I was not able to turn it on.
Maybe it's because I really want it to have helped, but I feel like the POP spot isn't moving as much when I'm locked on PRMI sidebands as it was earlier (we were seeing a lot of low frequency (few Hz) motion). So, I think I did something good.
We had our annual safety inspection today. Our SOPs are outdated. The full list of needed correction will be posted tomorrow.
The most useful found was that the ITMX-ISCT ac power is coming from 1Y1 rack. This should actually go to 1Y2 LSC rack ?
Please test this so we do not create more ground loops.
Linus-1, Nodus and others ac cords can be moved over to new blank yellow extension cord with multiple recepticals.
Remove two red extension cords going to Smart UPS
in order to Win in Loop Tuning, you must draw a cartoon of the cost function on the whiteboard before starting. Some qualitative considerations from our Workshop:
Give us a cost function in the elog and then keep tuning.
lsc and sus needed mxstream restarts after I restarted the ntp on fb.
We need to correctly setup crontab or rc.local for the frontend machines.
I wanted to check how the refl signals looked like.
I decided to measure the demod phase where PRCL and MICH appear, one by one.
The method I used is to actuate PRCL or MICH at a fixed frequency and rotate the demod phase such that
the signal at the actuating frequency disappears.
For the PRCL actuation, PRM was actuated by the lock-in oscillator with the amplitude of 100cnt.
For MICH, the ITMX and ITMY was actuate at the amplitude of 1000cnt and 1015cnt respectively.
The script I used was something like this
ezcaservo -r C1:CAL-SENSMAT_CARM_REFL11_Q_I_OUTPUT C1:LSC-REFL11_PHASE_R -g 100 -t 60
"11" should be changed according to the PD you want to test.
"Q" should be changed to "I" depending on form which quadrature you want to eliminate the signal
The option "-g" specifies the servo gain. This specifies which slope (up or down) of the sinusoidal curve the signal is locked.
Therefore, it is important to flip the signal angle 180degree if a negative gain is used.
Note: Original phase settings before touching them
REFL11 - 19.2
Here in the measurement PRMI was locked with AS55Q (MICH) and REFL55I (PRCL)
Without no serious reason I injected a peak at 503.1Hz. This peak is not notched out by the servo. There may have been
some residual effect of the feedback loops.
PRCL: By elliminating the peak from the Q quadrature, we optimize the I phase for PRCL.
REFL11, minimize PRCL in "Q", gain, -1, -19.3659 deg
REFL33, minimize PRCL in "Q", gain, -1, 132.813 deg
REFL55, minimize PRCL in "Q", gain, -1, 20.9747 deg
REFL165, minimize PRCL in "Q", gain, -1, -119.004 deg
MICH: By elliminating the peak from the I quadrature, we optimize the Q phase for MICH.
If PRCL and MICH appears at the same phase, the resulting angles shows an identical number.
REFL11, minimize PRCL in "I", gain, -1, -28.4526 deg
REFL33, minimize PRCL in "I", gain, -1, 65.9148 deg
REFL55, minimize PRCL in "I", gain, -1, 12.4051 deg
REFL165, minimize PRCL in "I", gain, -0.1, -143.75 deg
Then, the signal frequency was changed to 675Hz where the notch filters in the servo is active.
REFL11, minimize PRCL in "Q", gain, 1, -19.5224 deg
REFL33, minimize PRCL in "Q", gain, -1, 135.868 deg
REFL55, minimize PRCL in "Q", gain, 1, 48.5716 deg
REFL165, minimize PRCL in "Q", gain, 1, -122.398 deg
REFL11, minimize PRCL in "I", gain, -10, -73.7153 deg
REFL33, minimize PRCL in "I", gain, -10, 135.5 deg
REFL55, minimize PRCL in "I", gain, 10, -2.55868 deg
REFL165, minimize PRCL in "I", gain, -5, -156.135 deg
This is just a test of the REFL channels for the arms signals. ETMX or ETMY were actuated.
REFL11, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 145.694
REFL55, minimize ETMY in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = -60.1512
REFL11, minimize ETMX in "Q", gain 100 => C1:LSC-REFL11_PHASE_R = 142.365
REFL55, minimize ETMX in "Q", gain 100 => C1:LSC-REFL55_PHASE_R = -68.6521
I have installed Dropbox on the 40m workstations, using the foteee account.
I put it in /users/Dropbox.
As a side note, I did the install while sitting on Pianosa, but since I put the folder on the mounted hard drive, I think we should be able to use it from any workstation, although I have not yet confirmed this.
I was getting the Y Arm ready for Eric Q's loss measurements and so I looked at the noise and loop shape. The loop shape was strange:
You can see that the gain margin is too low at high frequencies. That's why we have >15 dB of gain peaking. Way too much! I think this is from Masayuki and Manasa increasing the phase margin at some point in the past. I lowered the gain by 3 dB from 0.1 to 0.07 and now the awful gain peaking is less. But what about the low frequency gain? Is there enough?
I calibrated the OUT channel with 14 nm/count (1/f^2) with a Q = 10 pole pair at 1 Hz. The error signal is done to cross over at 180 Hz. It looks like the resonant gain at 25 Hz is a little too much and the in-loop RMS is 10 pm. Jenne says the linewidth is ~1 nm, so this seems sort of OK. Except that the LIGO-I DARM RMS had to be <0.1 pm for ~the same linewidth. Do we need to do better before trying to bring the arms into resonance?
I've remove FM1 and FM8. I put the RollRG of FM8 into the BounceRG and renamed it BounceRoll. Also changed the Y-arm restore so that RollRG and the 5,5:0,0 are no longer triggered automatically since the double integrator was overkill and we already have a 1:0 in FM2. I also lowered the peak gain for the roll mode RG from 30 to 10 dB because it was also overkill. We've gained a few more degrees at the UGF.
The floor was cleaned under the east arm tube with hand held wet towel. We moved staff around and mopped. I did at the bottom of rack 1Y1, 2 and 3.
Last week we did the south arm tube floor.
Next week we 'd like to clean under rack 1X1,2,3, 4, 5, 6 and 7
1Y4, 1X1,2,3,4 & 5 instrument racks floor space were cleaned.
1X6, 1X7 and 1X9 instrument racks floor space were cleaned today
Not a whiteboard, but here's a cartoon of my oplev cost function cartoon. For the "maximize this area" and "minimize this area", I plan to use ratios between the curves, and then give those ratios to a sigmoid function.
I measured the arm cavity losses as Kiwamu did way back in ELOG 5074.
I used the same logic as the ../scripts/LSC/armloss script, but did it manually. This meant:
Analysis was done similar to ../scripts/LSC/armloss.m. This uses the nominal T values (.014 and 15e-6) to estimate the input power from the unlocked ASDC data, and the cavity reflectivity from the locked ASDC / input power. Then, loss is calculated by:
I did this for pairs of locked / unlocked data stretches. (Subsequent pairs maybe have slightly different things going on, but each pair was taken within a minute or so of each other)
Unfortunately, during the X Arm measurements, the MC was misbehaving with large REFL fluctuations, so I don't have confidence the results.
The Y Arm data seems fine, however.
The Y arm loss is 123.91 +/- 10.47 ppm
(Trial-to-Trial fluctuations dominate the fluctuations within each trial by far, and their standard deviation is what I report as the random error above)
This seems roughly in agreement with old values I've seen in the ELOG. I'll remeasure the x arm tomorrow during the day. Here's a plot showing the ASDC values of the Y Arm measurements.
At today's meeting, it was suspected that these noise levels were far too low. (ELOG 9660)
I've attached the math I did to get the conversions, as well as the dark noise SQRTINV spectra at various imitated transmission values and the python script that does the converting.
I've gone over my calculations, and think they're self-consistent. However, a potential source of misestimation is the treatment of the Lorentzian profile simply existing with the coupled arm line width (38pm). The conversion to m/rtHz is directly proportional to the line width of the transmission peak, so if it is much broader in practice (because of imperfect PRC buildup or something), the noise will be that much worse.
I'm open to any other feedback about what I may have done wrong!
#! /usr/bin/env python
import numpy as np
import matplotlib.pyplot as plt
data = np.loadtxt('./SQRTINVspectra.dat')
# Coupled arm linewidth
w = 38e-12
# Lorentzian value at full resonance
I0 = 700
The IMC has not been behaving well since this morning and totally not happy when Q was finishing his measurements. The WFS servo had large offsets in pitch. Looking back at the trend and using ezcaservo to restore the suspensions did not help.
I realigned the IMC and brought TRANS SUM to ~18000 and MCREFL to < 0.5. The spot positions are not very good; nearly 2 mm off in pitch on MC1 and MC3. But after the alignment of MC, the WFS servo offsets were below +/-20.
The MC has been locked stably with WFS servo ON for the last few hours.
P.S. I did not touch the WFS pointing or reset the WFS offsets.
Step by step description of transition from 2arm ALS to Common/Differential LSC for FPMI
- Step 0: Place the frequencies of the arm green beams at the opposite side of the carrier green.
- Step 1: Activate stablization loops for ALSX and ALSY simultaneously.
(Use LSC filter modules for the control. This still requires correct handling of the servo and filter module triggers)
- Step 2: Activate stablization loops for ALS Common and Differential by actuating ETMX and ETMY
I locked the arms using ALS error signals and the LSC filter modules. But when I try to acquire CARM and DARM using ALS, the arms lose lock when the matrix elements ALSX to Yarm and ALSY to X arm reach -/+0.9
What I did:
1. ALS locking of arms
(i) Found arm beat notes
(ii) Input matrix POX and POY elements set to '0'
(iii) Aux matrix elements ALSX to Xarm and ALSY to Y arm set to '1'
(iv) Power normalization matrix elements for TRX and TRY set to '0'
(v) Triggers for arm lock over ridden and the FM triggers were set to 'manual'
(vi) Arm servo gains set to '0'
(vii) All but FM5 were disabled
(viii) Phase tracker history reset and servo actuation set to ETMs
(ix) Servo gain increased in steps (+/-10 for the arms)
(x) FM1, FM6, FM7 enabled (see note 1 below)
(xi) FM9 enabled
Arms were locked with ~2000Hz rms
2. CARM and DARM locking
(i) Scanned the arms for IR resonance
(ii) Moved off-resonance (Stepped arm servo offsets by 30 counts)
(iiI) Stepped matrix elements ALSY to X arm and ALSX to Y arm ezcastep C1:LSC-PD_DOF_MTRX_6_29 +-0.1 C1:LSC-PD_DOF_MTRX_7_28 +0.1
Whenever the matrix elements reached -/+0.9, the arms were kicked out of lock. I don't see anything obvious as to why this is happening even after nearly 10+times of redoing.
1. I found the filters for the arm servos different for X and Y. FM1 and FM8 were missing in one of the filter modules. Jenne remembered Rana modifying and removing the unnecessary filters in one arm. We put back FM1 (low pass filter) which might not be necessary for PDH lock but is necessary for ALS. FM8 is now added to FM7.
2. To self : Check ALS Y arm power outlets (60Hz frequency comb seen in the error signal)
CMG-40T handheld controller unit is missing its power supply. In order to zero the instrument one has to apply plus and minus DC voltage.
The wiring on this 10 pin Amphenol PT02E-12-10P is shown.
In addition, we have to make sure to not let the suspension DACs saturate and make sure that the impulse response time of the OL servo is short; otherwise the lock acquisition kicks or bumps can make it wiggle for too long.
MC remained locked with WFS enabled all through last night and this morning. Koji dropped by and looked at the MC. The MC WFS servo, though stable, was at the edge of becoming unstable. This was because I did not touch the WFS pointing on the QPDs yesterday after realigning. So I recentered the WFS, reset the WFS filterbank offsets and reenabled the servo.
I measured the spot positions on MC mirrors for reference.
Spot positions in mm (MC1,2,3 pit MC1,2,3 yaw): [1.405767579680834, 0.79369009503571208, 1.3220430681427462, -1.2937873599406551, -1.1704264340968924, -1.2518046122798692]
ALS common locked by actuating on MC2 and ALS Differential locked by actuating on ETMX and ETMY (Stable lock acquired for over an hour).
Common and Differential offsets were swept to obtain IR resonance in both the arms (arms stayed on resonance for over 15 minutes).
1. Configured LSC settings to allow locking using ALS error signals.
2. Locked common and differential using ALS error signals
XARM 1 -1
YARM 1 1
X arm servo settings:
FIlters: FM1, FM5, FM6, FM7, FM9
Gain = -8.0
Y arm servo settings:
Filters: FM1, FM5, FM6, FM7, FM9
Gain = +8.0
ETMX 1 0
ETMY 0 1
3. Transitioned CARM control output to actuate on MC2 instead of ETMX
SUS-MC2_LSC servo gain = 1.0
The transition was done in very small steps : actuating on MC2 in -0.01 steps at the outmatrix upto -1.0 while reducing the ETMX actuation to 0 simultaneously.
DARM still stayed locked only with actuation on ETMY.
4. Transitioned DARM control to ETMX and ETMY.
Used ezcastep to step up DARM control (Y arm output) actuation on ETMX and step down the actuation on ETMY.
Final output matrix
ETMX 0 -0.5
ETMY 0 0.5
MC2 -1.0 0
Noise plot in attachment.
5. Finding arm resonance
Used ezcastep to gradually build up offsets in CARM (LSC-XARM_OFS) to find IR resoance in one arm (Y arm).
Introducing a small (order of 0.5) DARM offset (LSC-YARM_OFS) shifted the Y arm off-resonance.
Used CARM offset to get back the Y arm to resonance.
Changing CARM and DARM offsets alternately while tracking the Y arm resonance got us to a point where we had both the arms resonating for IR.
6. At this point the MC decided to give up and we lost lock.
1. We found that the WFS2 YAW output filterbank had the output switched OFF (probably accidentally by one of us). This was reenabled. Please be careful while manually turning ON and OFF the MC WFS servos.
Valve configuration: Vacuum Normal is reached in really 4 days if we do not count overnight rest of roughing.
VA6 and VC2 are reconnected. I'm turning on the RGA next
All 4 ion pumps were vented with air and pumped down to ~ 1e-4 Torr
Ion pumps gate valve control cables are connected and their pumps are disconnected.
The black relay box was tested repeatedly and it stopped misbehaiving.
We were at atmosphere for 13 days. Chamber BS, ITMX, ITMY and ETMY were opened.
Al foil "cups" were placed on the back side OSEMs of PRM.
Pd 76 and 77 are compared at 30 days of pumping. We spend 13-14 days at atmosphere before each.
Pump down 76 was with leaky ion pump gate valve. The ion pumps are not in use for years so they accumulated some higher pressure PLUS the valve switching caos at computer reboot most likely
increased the ion pumps pressures to about 10-20 torr
I think one of the ion pump gate valve was not sealing well. This leak was holding back pump down speed at pd76
Morning seconds without adjustment.
fb timing was off again.
I don't know why, but as you can see in Steve's plot from earlier this morning, the PMC transmission has been going down significantly all weekend. The PMC refl camera was very bright. I tweaked up the alignment (mostly pitch), and now we're back to normal.
The IMC was having trouble staying locked all morning, and I'm hoping that this PMC adjustment will help - the MC already looks better, although it's only been a few minutes.
Two weeks ago (Feb 26) I took the "Q MON" output of the demodulator that sends its Q output to the MC servo board as the error signal, and connected it to an SR785, so we can occasionally monitor the error signal noise. (Also, I did not appropriately ELOG the fact I touched things...)
I'm working on an automated script to do the monitoring, but the wireless router that the SR785 is connected is wicked slow. I should run an ethernet cable to it...
I'm just figuring I'll look at the full span (~100kHz) spectrum every ten minutes, and compare it to some nominal spectrum from a known-good time, and the last few hours.
As part of our CESAR testing last night, we had a look at the noise of the 1/sqrt(TR) signal.
Looking at the time series data, while we were slowly sweeping through IR resonance (using the ALS), Rana noted that the linear range of the 1/sqrt(TR) signal was not as wide as it should be, and that this is likely because our SNR is really poor.
When a single arm is at a normalized transmission power of 1, we are getting about 300 ADC counts. We want this to be more like 3000 ADC counts, to be taking advantage of the full range of the ADC.
This means that we want to increase our analog gain by a factor of 10 for the low gain Thorlabs PDs.
Looking at the photos from November when I pulled out the Xend transmission whitening board (elog 9367), we want to change "Rgain" of the AD620 on the daughter board. While we're at it, we should also change the noisy black thick film resistors to the green thin film resistors in the signal path.
The daughter board is D04060, S/N 101. The main whitening board for the low gain trans QPD is D990399, RevB, S/N 104.
We should also check whether we're saturating somewhere in the whitening board by putting in a function generator signal via BNC cable into the input of the Thorlabs whitening path, and seeing where (in Dataviewer) we start to see saturation. Is it the full 32,000 counts, or somewhere lower, like 28,000?
Actually the gain was changed. From gain of 2 (Rgain = 49.4kOhm) to 20 (Rgain = 2.10kOhm), Corresponding calibration in CDS was also changed by locking the Xarm, running ASS, then setting the average arm power to be 1. Confirmed Xarm is locking. And now the signal is used for CESAR. We see emperically that the noise has improved by a factor of approximately 10ish.
Today we modified the CESAR block.
- Now the sign(X) function is in a block.
- We decided to use the linearization of the PDH.
- By adding the offset to the TR signal used for the switching between TR and PDH, we can force pure 1/sqrt(TR) or pure PDH to control the cavity.
[Nic, Jenne, EricQ, and Koji]
We have used CESAR successfully to bring the Xarm into resonance. We start with the ALS signal, then as we approach resonance, the error signal is automatically transitioned to 1/sqrt(TRX), and ramped from there to POX, which we use as the PDH signal.
In the first plot, we have several spectra of the CESAR output signal (which is the error signal for the Xarm), at different arm resonance conditions. Dark blue is the signal when we are locked with the ALS beatnote, far from IR resonance. Gold is when we are starting to see IR resonance (arm buildup of about 0.03 or more), and we are using the 1/sqrt(TRX) signal for locking. Cyan is after we have achieved resonance, and are using only the POX PDH signal. Purple is the same condition as cyan, except that we have also engaged the low frequency boosts (FM 2, 3, 4) in the locking servo. FM4 is only usable once you are at IR resonance, and locked using the PDH signal. We see in the plot that our high frequency noise (and total RMS) decreases with each stage of CESAR (ALS, 1/sqrt(TR) and PDH).
To actually achieve the gold noise level of 1/sqrt(TR), we first had to increase the analog gain by swapping out a resistor on the whitening board.
The other plots attached are time series data. For the python plots (last 2), the error signals are calibrated to nanometers, but the dark blue, which is the transmitted power of the cavity, is left in normalized power units (where 1 is full IR resonance).
In the scan from off resonance to on resonance, around the 58 second mark, we see a glitch when we engage FM4, the strong low frequency boosts. Around the 75 second mark we turned off any contribution from 1/sqrt(TR), so the noise decreases once we are on pure PDH signal.
In the scan through the resonance, we see a little more clearly the glitch that happens when we switch from ALS to IR signals, around the 7 and 12 second marks.
We want to make some changes, so that the transition from ALS to IR signals is more smooth, and not a discrete switch.
Speaking of the whitening board, I had neglected to post details showing the the whitening was at least having a positive effect on the transmon QPD noise. So, here is a spectrum showing the effects that the whitening stages have on a QPD dark noise measurement like I did in ELOG 9660, at a simulated transmission level of 40 counts.
The first whitening stages gives us a full 20dB of noise reduction, while the second stage brings us down to either the dark noise of the QPD or the noise of the whitening board. We should figure out which it is, and fix up the board if necessary.
The DTT xml file is attached in a zip, if anyone wants it.
Nic, Jenne, EricQ, and Koji should describe the demonstartion of CESAR achieved tonight.
Q and I have started to use the ALS slow servo for the end aux lasers while locking the arms using ALS. The servo prevents us from hitting the limits of the PZT range for the end lasers and a better PDH locking.
But keeping the servo ON causes the slow output to drift away making it hard to find the beat note everytime the arm loses lock. The extensive beat note search following the unlock can be avoided by clearing history of the slow servo.
I have modified the IFOconfigure scripts and the corresponding .req files for the X arm and Y arm in burt. I have also added configure scripts to save and restore LSC settings for locking the arms using ALS error signals.
The settings are yet to be saved and the scripts should also be checked if they are working as required.
As Koji suggested in his email this afternoon, we looked at how much actuator range is required for various forms of arm locking: (1) "regular" PDH lock aquisition, (2) ALS lock acquisition, (3) CESAR cooling.
To start, I looked at the spectra and time series data of the control signal (XARM_OUT) for several locking situations. Happily, when the arm is at the half fringe, where we expect the 1/sqrt(TRX) signal to be the most sensitive (versus the same signal at other arm powers), we see that it is in fact more quiet than even the PDH signal. Of course, we can't ever use this signal once the arm is at resonance, so we haven't discovered anything new here.
EricQ then made some violin plots with the time series data from these situations, and we determined that a limit of ~400 counts encompasses most of the steady-state peak-to-peak output from locking on the PDH signal.
[ericq: What's being plotted here are "kernel density estimates" of the time series data of XARM_OUT when locked on these signals. The extent of the line goes to the furthest outlier, while the dashed and dotted lines indicate the median and quartiles, respectively]
I tried acquiring ALS and transitioning to final PDH signals with different limiters set in the Xarm servo. I discovered that it's not too hard to do with a limit of 400 counts, but that below ~350 counts, I can't keep the ALS locked for long enough to find the IR resonance. Here's a plot of acquiring ALS lock, scanning for the resonance, and then using CESAR to transition to PDH, with the limit of 400 counts in place, and then a lockloss at the end. Even though I'm hitting the rails pretty consistently, until I transition to the more quiet signals, I don't ever lose lock (until, at the end, I started pushing other buttons...).
After that, I tried acquiring lock using our "regular" PDH method, and found that it wasn't too hard to capture lock with a limit of 400, but with limits below that I can't hold the lock through the boosts turning on.
Finally, I took spectra of the XARM_OUT control signal while locked using ALS only, but with different limiter values. Interestingly, I see much higher noise between 30-300 Hz with the limiter engaged, but the high frequency noise goes down. Since the high frequency is dominating the RMS, we see that the RMS value is actually decreasing a bit (although not much).
We have not made any changes to the LSC model, so there is still no smoothing between the ALS and IR signals. That is still on the to-do list. I started modifying things to be compatible with CARM rather than a single arm, but that's more of a daytime-y task, so that version of the c1lsc model is saved under a different name, and the model that is currently compiled and running is reverted as the "c1lsc.mdl" file.
Annual crane inspection is scheduled for 8-11am Monday, March 17, 2014
The control room Smart UPS has two red extension cords that has to be removed: Nodus and Linux1
Q and I have started to...
Asymptotic cooling of the mirror motion with CESAR was tested.
With ALS and the full control bandwidth (UGF 80-100Hz), the actuator amplitude of 8000cnt_pp is required.
Varying control bandwidth depending on the noise level of the signal, the arm was brought to the final configuration with the actuator amplitude of 800cnt_pp.
It looks like that ETMX have 2 sticky magnets.
KroneCrane Fred inspected and certified the 3 40m cranes for 2014. The vertex crane crane was load tested at fully extended position.
Off again. Restarted ntp on fb.
It was little bit surprising to me but Rana's professorial rock'n roll excitation released its sticking on the unconfirmed thing by unconfirmed reason.
I aligned the Xarm manually and via ASS.
Now we are back in the normal state.
I am really, really happy to hear that it was just a sticking situation. Really happy.
This recovery proceeder deserves a pattern
Note: IR shield glass position variations, Atm4