The fibres carrying the beams from the ETMX as well as the ETMY have been routed to the PSL table now.
A part of the PSL beam has to be superposed on the fibre-outputs to obtain a beat signal. We have located a stray beam on the PSL(which is currently being dumped) which we plan to redirect for the same. The layout of the plan is attached herewith.
You are right Jamie! Thank you for the correction! I will now use the Teflon sheet instead of the PCB piece.
The photodiodes do have three legs, but I imagined the third one lying on a different plane, since it is spaced apart from the two I have drawn.
I should include this third leg in my drawing?
Ah! I see! Thank you!
I should put the LEDs and photodiodes closer together so that more of the reflected light falls on the photodiodes and the photodiodes have a higher response.
Also the reflectivity of the mirror will be optimized if the incident light is normal to the mirror surface. We will be setting up the photosensor and mirror so that the LEDs
emit light normal to the mirror surface. During displacement, this light may be slightly off-normal but still close to normal incidence. We want the photodiodes to be close to the LED since we want
them to detect light that is close to the path of normal incidence (small angles of reflection). [Thanks to Jenne for helping me figure this one out!]
Thank you for the suggestion ^___^
The power of the beam which is being coupled into the optical fibre is measured to be between 159 mW to 164 mW (The power meter was showing fluctuating readings).
The power out of the beam coming out of the fibre far-end at the PSL table is measured to be 72 mW. Here, I have attached a picture of the beam paths of the ETMY table with the beams labelled with their respective powers.
For the phase locking or beat note measuring we only need ~1 mW. Its a bad idea to send so much power into the fiber because of SBS and safety. The power should be lowered until the output at the PSL is < 2 mW. In terms of SNR, there's no advantage to use such high powers.
Well,the plan is to put in a neutral density filter in the beam path before it enters the fibre. But before I could do that, I set up the camera on the PSL table to look at the fiber output . I will need it while I realign the beam after putting in the Neutral Density Filter. I have attached the ETMY layout with the Neutral Density filter in place herewith.
In addition to the OL quadrants, you need to plot the OPLEV_PERROR and OPLEV_YERROR signals since these are the real signals we use for finding the mirror motion. If they're not in the Dataviewer, Jamie should add them as 256 Hz DAQ channels (using these names so that we have the continuity with the past). These DAQ channels correspond to the IN1 channels for the OL filter banks.
Also JPG are banned from the elog - you should put all of the plots into a single, multipage PDF file in honor of the new Wagonga.
Nicole: I thought we had decided to use teflon as the insulator between the PCB (yellow) and the LED/PDs? I don't think you should use another circuit board with copper on it. The copper will short the LED/PD heads to the metal box, which might be problematic.
Otherwise the design looks pretty good. I think the PDs have three leads each, yes?
Rotate the PDs and the LED so that you can put them as close as possible.
This is to increase the sensitivity of the sensor. Think why the closer the better.
Today I tested the photosensor head combination (2 Hamamatsu S5971 photodiodes and 1 Hamamatsu L9337 LED). I discovered that I had burnt out the LED and the photodiodes when I soldered them to the PCB board.
After looking up soldering information on Hamamatsu photodiodes, I learned that I need to solder at least 2 mm away from the head. I checked the pins of my burnt-out photodiodes and I had soldered 1.5 mm away from the head. To prevent this problem from happening again, Suresh suggested that I clip a lead onto photodiode/LED pin while I solder on connections to help dissipate some of the heat.
Today I was able to get a single photodiode (not attached to the PCB) to measure light emitted from an LED and I observed how voltage fluctuated as I moved the photodiode around the LED.
Suresh and Jamie also helped me to fix my photosensor head design (to make it more electrically-stable). Originally, I had planned to solder the LED and photodiodes onto a PCB and to mount that PCB to the front of a small metal Pomona Electronics box (with a whole cut out for the photodiodes and LED) using spacers, screws, and nuts. However, the PCB I am using to solder on the LED and photodiodes has metal connections that may cause problems for the LED and photodiodes lying on the surface. Now, the plan is to have the LED and photodiodes mounted to the PCB with an insulatory PCB in between. Below is an explanatory picture. I will determine the placement of the LED and photodiodes after making screws holes in the two PCBs to attach to the metal face of the box. I want to attach the screw holes first to make sure that the PCBs (and attached photosensor) are centered.
Since we are using Wiener filtering in our project, we studied the derivation of Wiener-Hopf equations. Whatever we understood we have written it as a pdf document which is attached below...
Healthy BS oplev
I repeated the BS oplev spectrum today and I do not understand why it does look different. I did it as Kiwamu describes it in entry#4948 The oplev servo was left ON!
It is working today! Finally I repeated the BS spectra, that we did with Kiwamu last week
The optical levers were centered during these measurements without the reference of locked cavities. They have no reference value now.
SRM sus need some help. ITMX is showing pitch/yaw modes of the pendulum .....OSEM damping is weak?
In order to test this preliminary circuit, I need to build the photosensor heads. Yesterday, Suresh helped me to open one of the professionally-build photosensors in the lab to understand how to arrange my photosensor heads. I now understand that I need to rigidly-mount the PCB to photosensor head box. I plan to use the PCB below. It will be sufficient for the lower-frequency range (below 10Hz) that I am interested in.
I would like to use a metal box like the one below to make each photosensor head. I looked in the lab last night for similar boxes but could not find one. Does anyone know where I can find a similar metal box?
I am now working on accelerometer. I am working on attaching these metal wires to the pins of the accelerometer so that I can use clip leads to power and extract voltage measurements from my circuit.
The LSC model has been updated:
We now take the filter state bit from the first filter bank in all RF PD I/Q filter banks (AS55_I, REFL11_Q, etc) as the controls for the binary analog whitening switching on the RF PD I/Q inputs. The RF_PD part was also modified to output this control bit. The bits from the individual PDs are then combined into the various words that are written to the Contec BO part.
Yesterday Suresh posted an updated LSC wiring diagram, with correct channel assignments for the RF PD I/Q and DC inputs. Upon inspection of the physical hardware we found that some of LSC the wiring was incorrect, with I/Q channels swapped, and some of the PDs in the wrong channels. We went through and fixed the physical wiring to reflect the diagram. This almost certainly will affect the EPICS settings for some of the input channels, such as offsets and RD rotations. We should therefore go through all of the RF inputs and make sure everything is kosher.
I also fixed all of the wiring in the LSC model to also reflect the diagram.
Once this was all done, I rebuilt and restarted the LSC model, and confirmed that the anti-whitening filter banks in the PD input filter modules were indeed switching the correct bits. I'll next put together a script to confirm that the LSC PD whitening is switching as it should.
Yesterday I found the C1:DAQ-FB0_C1???_STATUS lights to be red for the SUS, MCS, SCX, and SCY controllers. I know this has something to do with model communication with the framebuilder, but I unfortunately don't remember exactly what it is. I decided to try restarting the affected models to see if that cleared up the problem. It did. After restarting c1scx, c1scy, c1sus, and c1mcs everything came back up green.
We need some better documentation about what all of these status indicators mean.
Alberto is visiting us from Australia. He brought some terrific presents. It is going to be very demanding task to wait for the rest of the 40m team
to return from Wales to taste coffee: PNG Peaberry of Wagonga, Monsooned Malabar of Jindebah and Signature Blue Blend of Cosmorex.
The AA board shown in attachment 1 will be used in the seismometer hardware setup. A cartoon of this setup is shown in attachment 2.
BNC connectors are required for the seismometer breakout boxes. So the four-pin LEMO connectors present in the AA board were removed and panel mount BNC connectors were soldered to it. Red and blue colored wires were used to connect the BNC connectors to the board. Red wire connects the center of the BNC connector to a point on the board and that connection leads to the third leg (+IN) of the IC U### and the blue wire connects the shield of the BNC connector to the second leg (-IN) of the IC U###.
All the connections (including BNC to the AA board and in the AA board to all the filters) were tested using a multimeter by the beeping method and it was found that channel 10 (marked as C10) had a wrong connection from the point where the red wire (+ve) was connected to the third leg (+IN) of IC U91 and channel 32 (marked as C32) had opposite connections meaning the blue wire is connected to the third leg (+IN) of IC U311 and red wire is connected to the second leg (-IN) of IC U311.
The ETMY laser was operating at 1.5 A current and 197 mW power.
For the efficient frequency doubling of the AUX laser beam at the ETMY table, a higher power is required.
Steve and I changed the current level of the laser from 1.5 A to 2.1 A in steps of 0.1 A and noted the corresponding power output . The graph is attached here.
The laser has been set to current 1.8 Amperes. At this current, the power of the output beam just near the laser output is measured to be 390 mW.
Next we are going to adjust the green alignment on the ETMY and then measure the power of the beam.
At the output end of the fibre on the PSL, a power meter has been put to dump the beam for now as well as to help with the alignment at the ETMY table.
We looked at the ADC channel assignments in the LSC model and wanted to make sure that the LSC rack wiring and the LSC model are in agreement with each other. So the plan is to wire the rack as shown below. I will also post this file on svn so that we can keep it updated in case there are changes.
A copy of my summer progress report 1 has been uploaded to ligodcc 7/711 and I have just added a copy to the TTsuspension wiki
PDF copy of Summer Progress Report
During the daytime either tomorrow or Friday I'll adjust the actual dewhitening filters to match the measured zpk values.
I made a handy-dandy table showing the zpk values for each whitening filter in the wiki: New whitening filter page
Next on the whitening filter to-do list: actually put these values into the dewhitening filters in foton.
Just tying up a loose end. The next day Kiwamu and I checked to see what the trouble was. We concluded that the PRM had not moved during my measurement though I had 'Misaligned' it from the medm screen. So all the power levels measured here were with the PRM aligned. The power level change was subsequently measured and e-logged
The measured change in the REFL DC power with and without PRM aligned seems unacceptably small. Something wrong ?
The difference in the power with and without PRM aligned should be more than a factor of 300.
[difference in power] = [single bounce from PRM] / [two times of transmission through PRM ]
= (1-T) / T^2 ~ 310,
where T is the transmissivity of PRM and T = 5.5% is assumed in the calculation.
Also the reflectivity of MICH is assumed to be 1 for simplicity.
We now have (with the PRM misaligned):
REFL11: Power incident = 7.60 mW ; DC out = 0.330 V => efficiency = 0.87 A/W
REFL55: Power incident = 23 mW ; DC out = 0.850 V => efficiency = 0.74 A/W
and with the PRM aligned::
REFL11: DC out = 0.35 V => 8 mW is incident
REFL55: DC out = 0.975 V => 26 mW is incident
I found baked allen keys on the top of the clean optics cabinet. Somewhat heavy box that can come down in an earthquake on our heads.
NOTHING SHOULD GO ON THE TOP OF THE CABINETS OR RACKS except small plastic boxes that storing our clean clothing.
Please ask the owner unless it is rotten. Do not put food into garbage can inside. Take them outside so you are not inviting ants !
I have fit all of the LSC whitening filters using vectfit4.m
All the data is in my folder ..../users/jenne/LSC_WhiteningTest_29June2011/
The zpk info is saved with each plot of the fit. The pdfs are kind of huge to stitch together (or rather my computer doesn't want to do it), so I'll just post a representative one for now.
[Jenne / Kiwamu]
Last night we modified the locking scripts, that were called from C1IFO_CONFIGURE.adl, to adapt them to the new "PRCL" and "SRCL" convention.
So far they work fine and quitted dumping some error messages about inexistence of these channel names.
P.S. The locking scripts have been summarized on the 40m wiki
- Now the power and signal recycling cavity lengths are named "PRCL" and "SRCL" in stead of three letter names without "L".
We should change the locking script to accomodate these changes.
[Steve / Kiwamu]
Since the oplevs were the ones we haven't carefully tested, so the oplevs need to be checked.
This checking is also a part of the suspension optimizations (see the minutes of the last 40m meeting).
In this work Steve will check two things for all the oplevs :
1. Noise level including the dark noise, electrical noise and ADC noise to just make sure that the noise are blow the signal levels below ~ 30Hz.
2. The spectra of the signals to make sure there are no funny oscillations and unexpected structures
To check the things listed above, we take two kinds of oplves' spectra :
1. "dark noise" when the He-Ne beam is blocked.
2. "signals" when the optics are damped by only OSEMs
We did these checks on the BS oplev today (see the last entry).
All of them are fine, for example the dark noise (including electrical noise and ADC noise) are below the signal levels.
And no oscillation peak was found. Steve will go through all of the oplevs in this way.
So after talking to Kiwamu about it, I understand now that since the damping loops need all of this extra gain when the high-pass corner is moved up, it's more convenient to put that gain in the control filter itself, rather than having to crank the overall DC gain up to some inconveniently high value.
I'm attaching a screenshot of some of the problems I see so far with MC3.
I tried to fix all of the problems that I could identify in this screen shot:
We found the 30 Hz high pass filters had lower gain than what they used to be at low frequcnies.
So we increased the gain of the high pass filters called '30:0.0' by a factor of 10 to have the same gain as before.
I'm not convinced that this is what you want to do, or at least I wouldn't do it this way. The "k" in the zpk filter was set such that the filter had unity gain above the high-pass cut-off frequency. For a 30 Hz high-pass the k needs to be a factor of 10 smaller than it would be for a 3 Hz high-pass to achieve this high frequency unity gain.
As it is now these HP filters have 20 dB of gain above 30 Hz. If the open loop transfer function needs to more gain I would have done that by adjusting the overall DC gain of the filter bank, not by increasing the gain in this one filter. Maybe you guys have been doing it differently, though. Or maybe I'm just completely off base.
[Jenne / Rana/ Kiwamu]
We found the 30 Hz high pass filters had lower gain than what they used to be at low frequcnies.
Now all the suspension shows some kind of damping. Needs more optimizations, for example Q-adjustments for all the suspensions...
This is getting closer, but with the whitening left OFF and the cts2um filter also OFF, none of the suspensions are working correctly.
This is getting closer, but with the whitening left OFF and the cts2um filter also OFF, none of the suspensions are working correctly. I'm shutting down all the watchdogs until someone gets around to setting the damping gains and filters correctly.
I'm going to try to get the MC suspensions working OK for tonight so that we can use them for the PRMI locking work.
Update #1: None of the MC SUS DAQ channels are found by dataviewer....SUS debugging speed reduced by 10x. Tue Jul 05 21:38:17 2011
Update #2: POS/PIT/YAW BIAS sliders now seem to work, but are ~1000x too weak to do anything. Tue Jul 05 21:41:38 2011
Based on Rana's comment I have gone through and moved all of the corner frequencies for the high pass filters in the SUS damping controllers to 30 Hz. I did this for all optics (MC1, MC1, MC3, BS, ITMX, ITMY, PRM, SRM, ETMX, ETMY) all degrees of freedom (POS, PIT, YAW, SIDE).
Rana also suggested I turn off all of the BounceRoll filters until we get a chance to tune those individually for all the suspensions.
Finally, I normalized the MC SUSXXX filter banks to look just like all the other suspensions.
All damping filter banks for all degrees of freedom for all single suspensions should all be the same now (modulo the differences in the BounceRoll filters, which are now turned off).
In this past weekend the ABSL laser was successfully frequency-locked to the PSL laser with a frequency offset of about 100 MHz.
In the current setup a mixer-based frequency discriminator is used for detection of the beat-note frequency.
Setup for frequency locking
The diagram below shows the setup for the frequency locking.
Here I show two photos of the latest ABSL (ABSolute Length measurement) setup.
Figure.1 : A picture of the ABSL setup on the AP table.
The setup has been a little bit modified from the before (#4923).
As I said on the entry #4923, the way of sampling the ABSL laser wasn't so good because the beam, which didn't go through the faraday, was sampled.
In this latest configuration the laser is sampled after the faraday with a 90% beam splitter.
The transmitted light from the 90% BS (written in pink) is sent to the PSL table through the access tube which connects the AP and PSL table .
FIgure.2: A picture of the ABSL setup on the PSL table.
The 10% sampled beam ( pink beam in the picture) eventually comes to the PSL table via the access tube (the hole on the left hand side of the picture).
Then the ABSL beam goes through a mode matching telescope, which consists of a combination of a concave and a convex lens.
The PSL laser (red line in the picture) is sampled from a point after the doubling crystal.
The beam is combined at a 50 % BS, which has been setup for several purposes( see for example #3759 and #4339 ) .
A fast response PD (~1 GHz) is used for the beat-note detection.
The PRM sus damping was restored. It's side rms motion came down from 35 to 4 mV immediately. Lab air quality is back to normal.
The fireworks of yesterday showing up in the lab. Pasadena out side air 6.6 million cfm for 0.3 micron particles and 1.5 million cfm for 0.5 micron size.
Summary of the week ending July 3rd. Number of elog entries = 44
This CSHRC mangling on Feb 4 did more than re-arrange FB binaries.
It broke the path to MEDM for the 32-bit machines in the lab (e.g. mafalda) and stopped the MEDM snapshots from being posted onto our MEDM Status Web Page.
This is because, in addition to the paths mentioned in the above elog, the paths to the EPICS directories were also commented out. I've re-inserted them into our
.cshrc file in the 32-bit section; the statScreen CRON that Yoichi set up is now back in business.
* for some reason, the 'cronjob.sh' script is wiping out its own log file. It would be great if someone who understands stderr output re-direction can fix it so that the log-file from each run is retained until the next time cron runs.
MC1 MC2 MC3 ETMX ETMY ITMX ITMY PRM SRM BS mean std
Pitch 0.671 0.747 0.762 0.909 0.859 0.513 0.601 0.610 0.566 0.747 0.698 0.129
Yaw 0.807 0.819 0.846 0.828 0.894 0.832 0.856 0.832 0.808 0.792 0.831 0.029
Pos 0.968 0.970 0.980 1.038 0.983 0.967 0.988 0.999 0.962 0.958 0.981 0.024
Side 0.995 0.993 0.971 0.951 1.016 0.986 1.004 0.993 0.973 0.995 0.988 0.019
There is a large amount of variation in the frequencies, even though the suspensions are nominally all the same. I leave it to the suspension makers to ponder and explain.
Actually, ETMY was the only good one. They should all have the 30 Hz High pass as the damping filter. I think these details are in the elog entry that we originally made while doing ETMY.
They should all also have a 3:30 in the XXSEN to compensate the whitening. The logic is supposed to be that FM1 is ON when the hardware whitening is ON. This is the opposite of the old logic and its why the damping filter has to be moved from 3 to 30 Hz.
After finally figuring out what was messed up with ETMY I was able to get good measurements of the binary whitening switching on ETMY to determine that it is in fact working now:
ul : 3.2937569959 = 10.3538310999 db
ll : 3.28988426634 = 10.3436124066 db
sd : 3.34670033732 = 10.4923365497 db
lr : 3.08727050163 = 9.7914936665 db
ur : 3.27587751842 = 10.3065531117 db
I'm not sure what happened to ETMY SUS, but it was in a pretty bad state. Bad burt restore, I would guess.
Most egregiously, the inputs to all of the coil output filters were switched off. This is a bit insidious, since these inputs being off doesn't show up on the overview screen at all. This explains why ETMY had not been damping for the last couple of day, and why my binary whitening switching measurements were nonsense.
I also found that ETMYs damping filter was a 30 Hz high pass, instead of the 3 Hz high pass in all the other suspension controllers. Unfortunately a messed up burt restore can't explain that.
I normalized the ETMY controller to match all of the other controllers (ie. gave it a nice new 3 Hz high pass), adjusted gains accordingly, and now ETMY is behaving nicely.
I found many of the core optic (ETMs, ITMs, BS, PRM, SRM) suspension DOF damping controllers (SUSPOS, SUSPIT, SUSYAW, SUSSIDE) to be in various states of disarray:
I went around and tried to clean things up, by "normalizing" all of the DOF damping filter banks, ie. giving them all the same filters and clearing out unused filters, and then turning on all the appropriate filters in all core optic damping filter banks ("3:0.0", "Cheby", "BounceRoll"). I also went sure that all the outputs were properly on, and the oplev servos were on.
A couple of the optics had to have their gains adjusted to compensate for filter changes, but nothing too drastic.
Everything now looks good, and all optics are nicely damped.
I didn't touch the MC sus damping controllers, but they're in a similar state of disarray and could use a once-over as well.
I have fixed the binary whitening switching for the ETMs (ETMX and ETMY). See below for a description of what some of the issues were.
The ETMX whitening/no-whitening response (same measurements performed in my previous post on checking vertex sus whitening switching) looks as it should. The ETMY response seems to indicate that the switching is happening, but the measurements are very noise. I had to up the averaging significantly to get anything sensible. There's something else going on with ETMY. I'll follow up on that in another post.
ul : 3.28258088774 = 10.3243087313 db
ll : 3.31203559803 = 10.4018999194 db
sd : 3.27932572306 = 10.3156911129 db
lr : 3.28189942386 = 10.3225053532 db
ur : 3.31351020008 = 10.4057662366 db
ul : 2.9802607099 = 9.4850851468 db
ll : 1.46693103911 = 3.3281939600 db
sd : 2.19178266285 = 6.8159497462 db
lr : 2.2716636118 = 7.1268804285 db
ur : 3.42348315519 = 10.6893639064 db
One of the big problems was that the most up-to-date end rack cable diagrams (that I can find) are inconsistent with the actual binary mapping. The diagram says that:
In fact, the binary outputs are switched, such that output A carries the OSEM signals, and output B carries the QPD whitening signals.
I SWITCHED THE CABLES AT THE BINARY OUTPUT ADAPTER CHASSIS so that:
The rest of the wiring remains the same.
I made the same transformation for ETMY as well.
What is implicit in Suresh's entry is that we decided to run the WFS with the 10 dB internal attenuation set to ON as the nominal. In the past, we have always had all the attenuation OFF for max gain. The layout of the WFS is such that we get that nasty 200 MHz oscillation due to crosstalk between the 2 MAX4106 opamps for each quadrant. The 10 dB attenuator is able to reduce the positive feedback enough to damp the oscillation.
In principle, this is still OK noise-wise. I think the thermal noise of the resonant circuit should be ~2-3 nV/rHz. Then the first opamp has a gain of 5, then the -10 dB attenuator, then another gain of 5. The noise going to the demod board is then ~10-15 nV.
The real noise issue will be the input noise of the demod board. As you may recall, the output of the AD831 mixer goes to a AD797. The AD797 is a poor choice for this application. It has low noise only at high frequencies. At 10 Hz, it has an input voltage noise of 10 nV/rHz and a current noise of 20 pA/rHz. If we wanted to use the AD797 here, at least the RC filter's resistor should be reduced to ~500 Ohms. Much better is to use an OP27 and then choose the R so as to optimize the noise.
We should also be careful to keep the filter frequency low enough so as not to rate limit the OP27. From the schematic, you can see that this circuit is also missing the 50 Ohm termination on the output. There ought to be the usual high-order LC low pass at the mixer output. The simple RC is just not good enough for this application.
As a quick fix, I recommend that when we next want to up the WFS SNR, we just replace the RC with an RLC (R = 500 Ohms, L = 22 uH, C = 1 uF).