I installed a DC PD (Thorlabs PDA 520) in the beam path to AS55. I placed a 2" 90/10 BS on a flip mount that picks of enough light for the PD to spit out ~8V when the port is bright. Single arm continuous signal will be ~2V. While most of the light still continues towards AS55, the displacement from the BS moves the beam off AS55, so I used the flip mount in case anyone needs to use AS55. The current configuration is UP.
When we're done with loss investigations the flip mount should be removed from the bench.
I hooked the PD up to an ethernet-enabled scope and started scripting the loss map measurement (scope can receive commands via http so we can automate the data acquisition). The scope that was present at the bench and had been used for the MC ringdown measurements had a 'scrambled' screen that I couldn't fix so I had to retrieve another scope ("scope1"). I'll try to find out what's wrong with it but we may have to send it in for repair.
After Koji's leap second fix, we were playing around with the X arm locking. In particular, we were playing around with the limit value on the X arm LSC filter bank - the nominal value is 4000, we wanted to see if we could increase this without kicking the optic while acquiring arm lock. We initially increased it to 8000, and then turned it off altogether. Then we rapidly turned the output of the servo ON/OFF, and looked at the arm transmission to see if it came back to the level before unlocking, as an indication of whether the optic was kicked.
These trials suggested a value of 8000 for the limiter was OK, so we left the LSC mode on with the limiter set to 8000. But just as we were about to leave for the night, I noticed on the wall Striptool that the X arm was unlocked. Investigating, we found that the green wasn't even locking to a HOM. Further investigation of the Oplev spot showed that ETMX had received a large kick (both pitch and law errors were ~200urad). ITMX was unaffected.
We initially tried lowering the LSC limit value back to 4000, then used first the Oplev spot and then the green to align the arm. But turning on LSC misaligned the arm after acquiring lock. So we decided to leave LSC off, thinking that the notorious ETMX suspension problems have resurfaced. As a diagnostic, we figured we'd leave the watchdog tripped, and use the Oplev to see if the optic was getting kicked. But the act of turning the watchdog off kicked the optic again (WHY?!).
Looking at the ETMX sus screen, turning off all the damping and LSC (but watchdog on) still leaves a non-zero offset in the "Vmon" field, between 0.02-0.05V depending on the coil. Turning the watchdog OFF takes all these to 0.009V, although I can see the LR value fluctuating between 0.004V and 0.009V. I went to the Xend and squished all the cables on the Sat. Box, but the problem persisted.
At this time, I can't think of any explanation, so I am giving up for the night. To avoid unnecessarily kicking the optic, I am going to unplug the suspension from the Sat. Box and leave one of our tester boxes plugged in, lets see if that sheds any light on the situation...
Last night, I plugged the ETMX suspension coils back into the satellite box. Tonight, we turned on the damping loops for ETMX. Rana centered the Oplev so we can use that as an additional diagnostic to see if the optic gets kicked around overnight. We will re-assess the situation tomorrow.
Sometime earlier today, Lydia noticed that the +/- 5V Sorensens at the X end were not displaying their nominal voltage/current values (as per the stickers on them). She corrected this.
Summary pages show no kicking in the ETMX watchdogs from midnight to 6 AM (0800 - 1400 UTC):
Brief Summary: I am currently looking at the acoustic noise around both arms to see if there are any frequencies from machinery around the lab that stand out and to see what we can remove/change. I am using a Bluebird microphone suspended with surgical tubing from the cable trays to isolate it from vibrations. I am also using a preamp and the SR875 spectrum analyzer taking 6 sets of data every 1.5 meters (0 to 200Hz, 200Hz to 400Hz, 400z to 800Hz, 800Hz to 3200Hz, 3.2kHz to 12kHz, 12kHz to 100kHz).
· Attachment 1 is a PSD of the first 3 measurements (from 0 to 12kHz) that I took every 1.5 meters along the x arm with the preamp and spectrum analyzer
· Attachment 2 is a blrms color map of the first 6 sets of data I took (from 2.4m to 9.9m)
· Attachmetn 3 is a picture of the microphone set up with the surgical tubing
Problems that occurred: settings on the preamp made the first set of data I took significantly smaller than the data I took with the 0dB button off and the last problem I had was the spectrum analyzer reading only from -50 to -50 dBVpk
This AmScope microscope would have 3.5x-180x magnification, calibratable measurement function, 5MP picture and good working distance to work on printed circuit boards.
received this note: at 4:11pm Tuesday, Feb 7, 2017
Date: Wednesday, February 8, 2017
Time: 7:30 AM – 8:30 AM
Contact: Rick Rodriguez x-2576
Pasadena Water and Power (PWP) will be performing a switching operation of the
Caltech Electrical Distribution System that is expected to be transparent to Caltech,
but could result in a minor power anomaly that might affect very sensitive equipment.
IMPACT: Negligible impact......?
There may be temporary power interruption tomorrow!
PS:we did not see any effect
http://www.amscope.com/3-5x-180x-boom-stand-trinocular-zoom-stereo-microscope-with-144-led-ring-light-and-10mp-camera.html will be ordered today.
The actual unit we are getting has lockable zoom for better repeatability after calibration: SM-3NTPZZ-144
I'd like to fix a few things at 1X1 when we plug in the new amplifier for the 29.5MHz modulation signal.
Steve has ordered rolls of pre-twisted wire to run from 1X1 to the PSL table, so that part can be handled later.
But at 1X1, we need to tap new paths from +/- 24V to the DIN connectors. I think it's probably fine to turn off the two Sorensens, do the wiring, and then turn them back on, but is there any procedure for how this should be done?
Craig and I have been trying to put together a Simulink diagram of the proposed alternative calibration scheme. Each time I talk the idea over with someone, I convince myself it makes sense, but then I try and explain it to someone else and get more confused. Probably I am not even thinking about this in the right way. So I am putting what I have here for comments/suggestions.
What's the general idea?
Suppose the PSL is locked to the MC cavity, and the AUX laser is locked to the arm cavity (with sufficiently high BW). Then by driving a line in the arm cavity length, and beating the PSL and AUX lasers, we can determine how much we are modulating the arm cavity length in metres by reading out the beat frequency between the two lasers, provided the arm cavity length is precisely known.
So we need:
To be able to sense a 1kHz line being driven at 1e-16 m amplitude, I estimate we need a beat note stability of ~1mHz/rtHz at 1kHz.
Requirements and what we have currently:
On the hardware side of things, we need:
Koji and I briefly looked through the fiber inventory we have yesterday. We have some couplers (one mounted) and short (5m) patch fibers. But I think the fiber infrastructure we have in place currently is adequate - we have the AUX light brought to the PSL table, and there is a spare fiber running the other way if we want to bring the PSL IR to the end as well.
I need to also think about where we can stick the EOM in given physical constraints on the EX table and the beam diameter/aperture of EOM...
Question for Craig: What does the SNR of our lines have to be? IF we're only trying to calibrate the actuator in the audio band over long time scales, it seems we could get by with more frequency noise. Assuming we want a 1% calibration at 50-500 Hz, what is the requirement on the frequency noise PSD curve?
Koji, Gautam, Johannes
We quickly checked the situation of the projector in the control room.
- We found that the proejctor was indicating "lamp error".
==> Steve, could you remove the projector from the ceiling and check if it still does not work?
If it still does not work, send it back to the vender. It should be covered by the previous service.
- Zita seemed happy with the DVI output. We tried the dual display configration and VGA and DVI are active right now.
The DVI output (from RADEON something video card) is somewhat strange. We probably need to look into the video display situation.
We get SNR in two ways: the amplitude of applied force and the integration time. So we are limited in two ways: stability of the lock to applied forces and time of locklosses / calibration fluctuations.
At the sites, you probably know that we blow our spectrum out of the water with the calibration lines, with SNRs of about 100 on the scale of about 10 seconds. For us this might be impossible, since we aren't as quiet.
If we want 1% calibration on our sweeps, we'll need 0.01 = Uncertainty = sqrt( (1 - COH^2)/(2 * Navg * COH^2) ), where COH is the coherence of the transfer function measurement and Navg is the number of measurements at a specific frequency. This equation comes from Bendat and Piersol, and is subject to a bunch of assumptions which may not be true for us (particularly, that the plant is stationary in time).
If we let Navg = 10, then COH ~ 0.999.
Coherence = Gxy^2/(Gxx * Gyy), where x(t) and y(t) are the input signal and output signal of the transfer function measurement, Gxx and Gyy are the spectral densities of x and y, and Gxy is the cross-spectral density.
Usually SNR = P_signal / P_noise, but for us SNR = A_signal / A_noise.
Eric Q and Evan H helped me find the relationship between Coherence and SNR:
P = Pn + Pc, Pn = P * (1 - Coh), Pc = P * Coh
==> SNR = sqrt( Pc / Pn ) = sqrt( Coh / 1 - Coh )
From Coh ~ 0.999, SNR ~ 30.
This bulb was blown out on Feb 4, 2017 after 2 months of operation.
OK, but the questions still stands: "Assuming we want a 1% calibration at 50-500 Hz, what is the requirement on the frequency noise PSD curve?"
The microscope shipped back to the vendor for credit yesterday.
16 years old Lightwave NPRO M126-1064-700, sn 415 power output is tripping continously to zero.
The Lightwave Controller 125/126-OPN-POS sn516 was used in this test. Settings were lowered to close to nominal values without any success.
One can not determine what is broken: head or controller. This NPRO head was under Manasa's desk.
Property tag found.
As per Steve's request, I've checked the alignment of the IMC and the arms. These three cavities are locked and aligned.
I removed the video monitoring can and replaced it with Olympus SP-570UZ camera. It has no IR blocker. The OSEM light are dominant because I can not zoom in more.
I left the camera in place so you can try it. Leave the LEXAN plate on the glass window so no accident can happen. The illuminator is on and you can turn it off-on with the manual switch, close to the camera. Camera manual is on my desk.
The attached is the ETMY image with the single arm locked. This was the best I could do. Here is the recipe
Your technique works Koji
We spent some time trying to get the noise-budgeting code running today. I guess eventually we want this to be usable on the workstations so we cloned the git repo into /ligo/svncommon. The main objective was to see if we had all the dependencies for getting this code running already installed. The way Evan has set the code up is with a bunch of dictionaries for each of the noise curves we are interested in - so we just commented out everything that required real IFO data. We also commented out all the gwpy stuff, since (if I remember right) we want to be using nds2 to get the data.
Running the code with just the gwinc curves produces the plots it is supposed to, so it looks like we have all the dependencies required. It now remains to integrate actual IFO data, I will try and set up the infrastructure for this using the archived frame data from the 2016 DRFPMI locks..
I looked through the lab area to do a fast photodiode inventory check, as we may need to buy some for the higher order mode spectroscopy SURF project. I looked on the following optical tables: ETMY, ITMY, BS, AS, PSL, SP, ITMX, Jenne laser table, and ETMX, as well as the photodiode cabinet, and could only find two 1611s. Here is a summary of the inventory:
I have not yet checked if these photodiodes are in working order.
Dataviewer wouldn't launch on pianosa - it seemed to work fine on Donatella though. Rana suggested using the ipcs -q command. The complete fix can be found in this elog. This did the trick, dataviewer runs fine on Pianosa now...
Since we'd like to get back to DRSE locking, I tried locking the DRMI tonight. I did the following:
GV 26 April 2017, 3pm: Forgot to note yesterday that I re-connected the suspect Satellite box, which has been connected to the SRM signal chain, back to the SRM suspension. I did not see any instances of glitching during my work last night. Also added pictures showing shifted spots on ITMs when PRC is locked relative to when arms are locked...
I got a couple of ~30min long DRMI lock stretches today. The settings I used are essentially the same as what I had back in November. Though we have since made some changes to the IMC RF signal chain, I guess it is not unreasonable that the LSC Demod phases that worked then work now as well.
In the lock stretches, I did the following:
On the side, I'm also looking at whether the PRC angular feedforward filters, last trained in October 2016, remain valid. Even post midnight, I am unable to lock the DRMI without turning on the FF, and looking at the POP QPD PIT and YAW signal spectra with the FF on vs FF off, there is definitely some improvement in the 1-4Hz band (plot to follow), question is whether we can do better and hence improve the DRMI duty cycle/ make the lock acquisition easier. To this end, I centered the beam on the POP QPD after locking and dither aligning the PRC on carrier, and have taken some data to look at.
So, much data analysis to follow - the idea is to put together a DRMI noise budget with Evan's NB code. For now, here are the uncalibrated control signal spectra.
one of these signals does not look like the others: explanation?
I took a closer look at the POP QPD/ PRC angular feedforward situation yesterday. I thought it would be useful to have a POP QPD MEDM screen. Looking at the PIT and YAW channel filter modules, the anti-whitening filters seemed different from what we have for other channels that are connected to the Pentek interface board (e.g. MCL). So I copied over the 150:15 (z:p) filter, and also turned on a 60Hz comb. The LSC offsets script does not set the dark offsets for this QPD, so I manually put in the dark offsets for the PIT, YAW and SUM channels as well. For the locking, I first locked the arms on IR an dither aligned them. Then I locked the PRMI on carrier, ran the PRC dither alignment, and went over to the ITMX pickoff table and centered the beam on the QPD by making the PIT and YAW channel timeseries oscillate around approximately zero.
After these tweaks, I collected ~40mins of data with the angular FF OFF/ON. I did not DC couple the ITM Oplev servos, but Eric tells me that this did not make a difference to the achievable subtraction in the past. Here is the frequency domain multicoherence analysis - I used the BS_X and BS_Y seismometer channels as witnesses. I've also put a plot with what the raw FF filter coefficients look like (no fitting yet).
Looks like we can do better for both DOFs - it even seems like we are injecting noise with the current FF filters in some bands, perhaps we can do a better job of rolling off the filters outside the band of interest. Eric and I were discussing MATLAB's "reduce" routine for this purpose, I will play around with it and see if I get a better fit.
Unfortunately, I encountered a strange error when trying to pull data with nds2 today, it kept complaining RuntimeError: Too many channels or too much data requested. even though I have pulled longer stretches of data for more channels with 16k sampling rate as recently as last week. Shorter duration requests (<600 seconds) seemed to work fine though... So I had to use cds.getdata to pull the data, and they're much too large to attach. Has anyone else encountered a similar error?
The mystery of the spots on the ITMs when the PRC is locked on carrier remains - after talking this over with Koji, we figured that even with the carrier resonant, the spot will be much dimmer than the spots when the arms are locked, but what I see on the cameras is still a pretty beefy spot. The real cavity mode is actually visible where it should be (I marked the locations of the spots with arms well-aligned with a marker on the monitors), as given away by some twinkling that is visible only when the cavity is locked. But what ghost beam is so intense it looks almost as bright as when the arm is locked?
GV 10pm 28 April 2017: Turns out this is the spot from the single bounce off the ETM transmitting back through the ITM and hitting the suspension cage (hence the bright spot). Johannes and I confirmed by moving the ETM, the spot moved with it. I just never paid attention to this spot before.
For the traces I posted, I had not turned on the whitening for the SRCL sensing PD (REFL55). However, I took a spectrum on a subsequent lock, with the analog whitening + digital dewhitening turned on for all 3 PDs (AS55, REFL11 and REFL55), and the HF part of the SRCL spectrum still looked anomalous. I'm putting together the detailed NB, but here's a comparison between the signals from the 3 RFPDs with the PSL shutter closed (but whitening engaged, and with the analog gains at the same values as used during the locking).
To convert the y-axis into m/rtHz, I used data from a sensing matrix measurement I took yesterday night during a DRMI lock - I turned on lines between 300 Hz and 325 Hz for the 3DOFs for ~5 minutes, downloaded the RFPD error signal data and did the demodulation. I used numbers from this elog to convert the actuator drive from cts to m. The final numbers I used were:
MICH (AS55_Q): 8.706 * 10^11 cts/m
PRCL (REFL11_I): 2.757 * 10^12 cts/m
SRCL (REFL55_I): 1.995 * 10^10 cts/m
So it looks like there may be something weird going on with the REFL55 signal chain. Looking at the LSC rack (and also suggested by an elog search), it looks like the demodulation is done by a demod board labelled "POP55" - moreover, the demodulated outputs are taken not from the regular output ports on this board, but from the "MON" ports on the front panel.
I forgot we had done this last year already, but we updated the control room network switch labels and double checked all the connections. Here is the status of the connections and labels as of today:
There are a few minor changes w.r.t. labeling and port numbers compared to the Dec 2015 entry. But it looks like there was no IP clash between Rossa and anything (which was one of the motivations behind embarking on this cleanup). We confirmed by detatching the cable at the PC end of Rossa, and noticed the break in the ping signals. Plugging the cable back in returned the pings. Because Rossa is currently un-bootable, I couldn't check the MAC address.
We also confirmed all of this by using the web browser interface for the switch (IP = 192.168.113.249).
One is broken, two are ready to steer green and 3 available in un known condition
I also have a functional one on my desk, which has one of the wires repaired.
I've been playing around with Evan's NB code trying to put together a noise budget for the data collected during the DRMI locks last week. Here is what I have so far.
Attachment #1: Sensing matrix measurement.
Attachment #2: MICH OLTF measurement vs model
Attachment #3: Noise budget
I think I did the various conversions/calibrations/loop algebra correctly, but I may have overlooked something. Now that the framework for doing this is somewhat set up, I will try and put together analogous NBs for PRCL and SRCL.
GV 22 August 2017: Attachment #4 is the summary of my demod board efficiency investigations, useful for converting sensing measurement numbers from cts/m to W/m.
I think the most important next two items to budget are the optical lever noise, and the coil driver noise. The coil driver noise is dominated at the moment by the DAC noise since we're operating with the dewhitening filters turned off.
In order to do so, I took a swept sine measurement with a few points between 50 Hz and 500 Hz. The transfer function between C1:LSC-MICH_OUT_DQ and the Oplev Servo Output point (e.g. C1:SUS-BS_OL_PIT_OUT etc) was measured. I played around with the excitation amplitude till I got coherence > 0.9 for the TF measurement, while making sure I wasn't driving the Oplev error point too hard that side-lobes began to show up in the MICH control signal spectrum.
I was also looking at the Oplev servo shapes and noticed that they are different for the ITMs and the BS (Attachment #1). Specifically, for the ITM Oplevs, an "ELP15" is used to do the roll-off while an "ELP35" is employed in the BS servo (though an ELP35 also exists in the ITM Oplev filter banks). I got lost in an elog search for when these were tuned, but I guess the principles outlined in this elog still hold and can serve as a guideline for Oplev loop tweaking.
Coil driver noise estimation to follow
GV 10 May 12:30pm: I've uploaded another copy of the NB (Attachment #3) with the contributions from the ITMs and BS separated. Looks like below 100Hz, the BS coupling dominates, while the hump/plateau around 350Hz is coming from ITMX.
That's a good find.
I first shutdown the SRM watchdog, noted cabling between these boards and also the AI board as well as output to Sat. Box. I also needed to shutdown the MC2 watchdog as I had to remove the DAC output to MC2 in order to remove the SRM Dewhitening board from the rack. This connection has been restored, MC locks fine now.
I believe the ETMs and ITMs are different from the others.
I've added marked-up schematics + high-res photographs of the SRM coil driver board and dewhitening board to the 40m DCC Document tree (D1700217 and D1700218).
In the attached marked-up schematics, I've also added the proposed changes which Rana and I discussed earlier today. For the thick-film -> thin-film resistor switching, I will try and make a quick LISO model to see if we can get away with replacing just a few rather than re-stuff the whole board.
Another change I think should be made, but I forgot to include on the markups: On the dewhitening board, we should probably replace the decoupling capacitors C41 and C52 with equivalent value electrolytic caps (they are currently tantalum caps which I think are susceptible to fail by shorting input to output).
I've made the LISO models for the dewhitening board and coil driver boards I pulled out.
Attached is a plot of the current noise in the current configuration (i.e. dewhitening board just has a gain x3 stage, and then propagated through the coil driver path), with the top 3 noise contributions: The op-amps (op3 and op5) are the LT1125s on the coil driver board in the bias path, while "R12" is the Johnson noise from the 1k input resistace to the OP27 in the signal path.
Assuming the OSEMs have an actuation gain of 0.016 N/A (so 0.064 N/A for 4 OSEMs), the current noise of ~1e-10 A/rtHz translates to a displacement noise of ~3e-15m/rtHz at ~100Hz (assuming a mirror mass of 0.25kg).
I have NOT included the noise from the LM6321 current buffers as I couldn't find anything about their noise characteristics in the datasheet. LISO files used to generate this plot are attached.
I first set the bias sliders to 0 on the MEDM screen (after checking that the nominal values were stored), then shut down the watchdogs, and then pulled out the boards for inspection + photo-taking.
I've uploaded high-res photos + marked up schematics to the same DCC page linked in the previous page. I've noted the S/Ns of the ITM, BS and SRM boards on the page, I think it makes sense to collect everything on one page, and I guess eventually we will unify everything to a one or two versions.
To take the photos, I tried to reproduce the "LED light painting" technique reported here. I mounted the Canon EOS Rebel T3i on a tripod, and used some A3 sheets of paper to make a white background against which the board to be photographed was placed. I also used the new Macro lens we recently got. I then played around with the aperture and exposure time till I got what I judged to be good photos. The room lights were turned off, and I used the LED on my phone to do the "painting", from ~a metre away. I think the photos have turned out pretty well, the component values are readable.
I got some hands-on-experience on using RF photodetectors and the Network Analyzer from Koji. There were newly purchased RF photodetectors from Electro-Optics Technology, Inc.. These were InGaAs Photodetectors with model no.: 120-10050-0001(ET-3010) and 120-10056-0001(ET-3040). The User Guide for the two detectors can be found here. This is the first time we bought the ET-3010 model PD for the 40m lab. It has an operation bandwith >1.5GHz(not tested yet), much higher than other PDs of its kind. This can be used for detecting the output as we 'sweep' the laser frequency for getting data on the optical cavities and the resonating modes inside the cavity. We just tested out the ET-3040 model today but will test out the ET-3010 next week.
Tools and Machines Used:
We worked on the optical bench right in front of the main entrance to the lab. We put the cables, power chords, etc. to their respective places. We used screws, poles, T's, I's, multimeter, Network/Spectrum Analyzer(along with the moving table), a lab computer, Oscilloscope, power supply and the aforementioned PDs for our testing. We took these items from the stack of tools at the Y-arm and the boxes of various different labelled palced near the X-arm. We moved the Network Analyzer(along with the bench) from near the Y-arm to our workplace.
I will include a rough schematic of the setup later.
We alligned the reference PD(High Speed Photoreceiver model 1611) and the test PD(ET-3040 in this case) to get optimal power output. We had set the pump current for the laser at 19.5mA which produced a power of 1.00mW at the output of the fiber couple. At the reference detector the measured voltage was about 1.8V and at the DUT it was about 15mV. The DC transimpedance for the reference detector is 10kOhm and its responsivity to 1064 nm is around 0.75A/W. Using this we calculate the power at the reference detector to be 0.24mW. The DC transimpedance for the DUT is 50Ohm and the responsivity of about 0.9A/W. This amounts to a power of about 0.33mW. After measuring the DC voltages, we connected the laser input to the Network Analyzer and gave in an RF signal with -10dBm and frequency modulation from 100 kHz to 500 MHz. The RF output from the Analyzer is coupled to the Reference Channel(CHR) of the analyzer via a 20dB directional coupler. The AC output of the reference detector is given at Channel A(CHA) and the output from the DUT is given to Channel B(CHB). We got plots of the ratios between the reference detector, DUT and the coupled refernce for the Transfer Function and the Phase. We found that the cut-off frequency for the ET3040 model was at arounf 55 MHz(stated as >50MHz in the data sheet). We have stored the data using the lab PC in the directory .../scripts/general/netgpibdata/data.
The bandwidth of the ET-3040 PD is as stated in the data sheet, >50 MHz.
These PDs have an internal power supply of 3V for ET-3040 and 6V for ET-3010. Do not leave these connected to any instruments after the experiments have been performed or else the batteries will get drained if there is any photocurrent on the PDs.
A similar procedure has to be followed in order to test the ET-3010 PD. I will be doing this tentatively on Monday.