Those 'peaks' for the oscillations seem ridiculously broad. I think you should look again, really quickly, with smaller bandwidth at, say, the 2kHz oscillation, to make sure it looks reasonable.
I did just this, and it looks okay to me:
I took POP QPD calibration data with a new method, on Rana's suggestion. I locked the PRMI, and engaged the ASC servo, and then used awggui (x8) to put dither lines on all of the PRMI-relevant optic's ASCPIT and ASCYAW excitation points. I then took the transfer function of the suspensions' oplev signals (which are already calibrated into microradians) to the POP_QPD signals (which are in counts). This way, we know what shaking of any optic does to the axis translation as seen by the POP QPD. We can also infer (from BS or PRM motion for PR3, and ITMX motion for PR2) what the folding mirrors do to the axis translation. Note that we'll have to do a bit of matrix math to go from, say, PRM tilt effect to PR3 tilt effect on the axis motion.
The data is saved in /users/jenne/PRCL/July152013_POP_TFs.xml . There is also a .txt file with the same name, in the same folder, listing the frequencies used by the awg.
I'll analyze and meditate tomorrow, when my brain is not so sleepy.
The X arm whitening filters of the beatbox were modified.
Now we have about 10 times better floor level above 100Hz and ~3 better at 1Hz.
- The previous whitening was zero@1Hz, pole@10Hz, and the DC gain of the unity.
When the Marconi signal (~30MHz -25dBm) was given to the beatbox (via ZFL-1000LN),
the DC output of the beatbox was only 140mV (lame). This corresponded to 220 counts in
the CDS. (BTW the signals were calibrated by giving frequency deviation of 1kHz is applied at 125Hz.)
- If you compare the analog measurement of the beatbox output and what we see in the I phase signal,
you can see that we were completely dominated by the ADC noise (attachment 2, blue and red).
- The new whitening is email@example.comHz, pole@159Hz, and the DC gain of 10.
- This improved the sensing noise by a factor of ten above 100Hz.
- We are stil llimited by the digitizing noise between 3Hz to 100Hz.
We need steeper whitening like 2nd order from 1Hz to 100Hz. (and probably at DC too).
Now the DC amplitude is about 1.4V (and 2200 counts in the CDS).
So, it is interesting to see how the sensing limit changes by increasing
the overall gain by a factor of 3, and have (zeros@1Hz & poles@10Hz)^2.
This can be implemented on a proto-daughter board.
- By the way, the performance below 2Hz is now better than the analog one with the previous whitening.
This improvement might have come from the replacement of the thick film resistors by thin-film resistors.
(See the circuit diagram)
About the nominal power of the beatbox input.
- Marconi (-20dBm 30MHz) was directly connected to the beatbox. The RF output of -15dBm was observed at the delayline output.
- According to the beatbox schematic, the mixer LO and RF inputs were expected to be -9dBm and -19dBm.
- The nominal mixer LO level is supposed to be 7dBm. Therefore the nominal beatbox input should be -4dBm.
- Assuming 23dB gain of the preamp, the PD output is expected to be -27dBm.
- When the PD out is -27dBm, the RF mon is expected to be -5dBm. This is the level of the RF power expected to be seen in the control room.
- The output of the beatbox was measured as the function of the input to the preamp (before the beatbox input).
With the nominal gain, we should have observed amplitude of ~170. And it is now 1700 because of the whitening modification.
Keven and Steve,
The 3 cranes tested and wiped off as preparation for upcoming vent.
I tried shifting the notch frequencies on the D000186-revision D board given to me by Koji. The existing notches were at ~16 kHz and ~32 kHz. I shifted these to notches at ~64 kHz and ~128 kHz by effecting the following changes (see schematic for component numbering) on Channel 8 of the board-I decided to check things out on one channel before implementing changes en masse:
=> New notches should be at 66.3 kHz and 131.7 kHz.
I then measured the frequency response of the modified channel using the SR785, and compared it to the response I had measured before switching out the resistors. The SR785 only goes up to 102 kHz, so I cannot verify the 128 kHz notch at this point. The position of the 64 kHz notch looks alright though. I think I will go ahead and switch out the remaining resistors in the evening.
Note 1: These plots are just raw data from the SR785, I have not tried to do any sort of fitting to poles and zeros. I will do this at some point.
Note 2: All these smts were taken from Downs. Todd helped me locate the non-standard value resistors. I also got a plastic 25-pin D-sub backshells (the spares are in the rack), with which I have fashioned the required custom ribbon cables (40 pin IDC to 25 pin D-sub with twisted ribbon wire, and a short, 10pin IDC to 10pin IDC with straight ribbon wire).
c1sus, c1ioo, c1iscex and c1iscey were down. Why? I was trying to lock the arm and I found that around this time, several computers stopped working mysteriously. Who was working near the computer racks at this time???
I did an ssh into each of these machines and rebooted them sudo shutdown -r now
But then I forgot / neglected/ didn't know to bring back some of the SLOW Controls computers because I am new here and these computers are OLD. Then Rana told me to bring them back and then I ignored him to my great regret. As it turns out he is very wise indeed as the legends say.
So after awhile I did Burtgooey restore of c1susaux (one of the OLD & SLOW ones) from 03:07 this morning. This brought back the IMC pointing and it locked right away as Rana foretold.
Then, I again ignored his wise and very precious advice much to my future regret and the dismay of us all and the detriment of the scientific enterprise overall.
Later however, I was forced to return to the burtgooey / SLOW controls adventure. But what to restore? Where are these procedures? If only we had some kind of electronics record keeping system or software. Sort of like a book. Made of electronics. Where we could LOG things....
But then, again, Rana came to my rescue by pointing out this wonderful ELOG thing. Huzzah! We all danced around in happiness at this awesome discovery!!
But wait, there was more....not only do we have an ELOG. But we also have a thing called WIKI. It has been copied from the 40m and developed into a thing called Wikipedia for the public domain. Apparently a company called Google is also thinking about copying the ELOG's 'find' button.
When we went to the Wiki, we found a "Computer Restart Procedures" place which was full of all kinds of wonderous advice, but unfortunately none of it helped me in my SLOW Controls quest.
Then I went to the /cvs/cds/caltech/target/ area and started to (one by one) inspect all of the targets to see if they were alive. And then I burtgooey'd some of them (c1susaux) ?? And then I thought that I should update our 'Computer Restart Procedures' wiki page and so I am going to do so right now ??
And then I wrote this elog.
We added our reference photodetector (Newport 1611, REF DET) to the southern edge of the AS table, as pictured. The detector's power supply is located under the southwest corner of the table, as pictured. We have connected the detector to its power supply, and will connect the detector's fiber input and RF output tomorrow.
The proto-ASC now includes triggering. I have updated the hacky temp ASC screen to show the DoF triggering. I have to go, but when I get back, I'll also expose the filter module triggering. So, for now we may still need the up/down scripts, but at least the ASC will turn itself off if there is a lockloss.
I have modified the settings on the router that connects our Martian network to the outside world so that one can access the NDS2 server running on megatron:31200.
To get at the data you point your data getting client (Matlab, ligoDV, DTT, etc.) at our router and the megatron port will be forwarded to you:
is what you should point to. Now, it should be possible to run DetChar jobs (e.g. our 40m Summary pages) from the outside on some remote server. You can also grab 40m data on your laptop directly by using matlab or python NDS software.
For the RFPD frequency response project, we routed the fiber that will connect our REF DET (on the AS table) to our 1x16 optical splitter (in the OMC_North rack), as pictured. (The new fiber is the main one in the picture, which ends at the right edge near REF DET) Note that we secured the fiber to the table in two places to ensure the fiber would remain immobile and out of other optical paths already in place.
At 2:00 we plan to run fiber from our laser module (in rack 1Y1) to our 1x16 optical splitter (in the OMC_North rack) and measure the power output at one of the splitter's output ports. We plan to keep the output power limited to less than 0.5 mW per optical splitter output.
We decided that the POY Table would be a better home for our REF DET (Newport 1611 FC-AC) than the AS Table. We moved the PD to the POY Table (1st attachment) and routed a fiber from our 1x16 Optical Splitter in the OMC_North rack to the POY Table. REF DET's power supply is now located under the POY table (2nd attachment). We left the fiber described in the previous post on the AS Table.
Afterwards, we hooked a fiber up to our laser module to test it (3rd attachment). The laser was not being distributed, just going to one fiber with a power meter at its end. Everything turns out, but we realized we need to read the power supply's manual before continuing.
We did the same mod of the beatbox for the Y arm too. See
The new whitening filters improved the out-of-loop ALS stability of the Y arm down to 300Hz (20pm_rms in displacement).
- After modifying the whitening filters, the out-of-loop stability of the arms were tested with the IR PDH signals.
- The X arm showed non-stationarity and it made the ALS servo frequenctly fell out of lock.
- For now we decided to use the Y arm for the PRMI+one arm trial.
- The performance of the ALS was tested with several measurements. (attachment 1)
Cyan: Stability of the beatnote frequency with the MC and the arm freely running. The RMS of the day was ~6MHz.
Blue: Sensing limit of the beat box was tested by giving a signal from Marconi. The same amplitude as the X arm beat was given as the test signal.
This yielded the DC output of ~1200 counts.
Green: Out-of-loop estimation of the beatbox performance. This beat note stability was measured by controlling the arm with the IR PDH signal.
Assuming the PDH signal has better SNR than the beat signal, this gives us the out-of-loop estimation of the stability below 150Hz, which is the
unity gain frequency of the ALS loop.
Above 150Hz the loop does not force this noise to the suspension. Just the noise is injected via a residual control gain (<1).
Black: In-loop evaluation of the ALS loop. This becomes the left over noise for the true stability of the arm (for the IR beam).
Red: The arm was brought to the IR resonance using the ALS offset. The out-of-loop stability was evaluated by the IR PDH signal.
This indeed agreed with the evaluation with the other out-of-loop evaluation above (Green) below 150Hz.
Attachment 2 shows the time series data to show how the arm is brought to the resonance.
1 count of the offset corresponds to ~20kHz. So the arm started from 200kHz away from the resonance
and brought to the middle of the resonance.
(Manasa downloaded the 2k sampled data so that we can use this for presentations.)
[Koji, Jenne, Manasa, Annalisa, Rana, Nic]
- After we checked the functionarity of the Yarm ALS, both arms were locked with the IR, and aligned by ASS.
- Disengaged the LSC feedback. Approximately aligned the PRM.
- Recorded the current alignment biases. Turned off all of the oplevs.
- Went into the lab, aligned all of the oplevs on the QPDs (except for the SRM).
- Check the locking of the PRMI.
- Once it is locked, go into the lab again and align the POP QPD.
- Check everything of the PRMI LSC/ASC works.
- Misalign PRM by 0.2
- Lock the arm again. Run ASS again.
- Miaslign ETMX.
- Lock the Xarm with green. Adjust the beat freq between 30-50MHz.
- Reset Phase Tracker history.
- Check if there is any offset for the ALS. If there is, adjust it to zero.
- Stabilize the arm with the ALS. We should check the sign of the servo before it is cranked up to the nominal.
- Confirm if the offset FM has LPF (30mHz LPF).
- Run excastep for the ALS offset until we find the TEM00 resonance of the IR
- Record the offset at the resonance.
- Step back by 5 count (=100kHz)
- Started from the offset of -5.
- Aligned the PRM and the PRMI was locked by REFL165I(x0.8)nadQ(x0.2).
- PRM ASC engaged
- Moved the offset to -4 by ezcastep C1:ALS-OFFSETTER2_OFFSET +0.01,100 -s 0.1
ezcastep C1:ALS-OFFSETTER2_OFFSET +0.01,100 -s 0.1
- Moved to -3, -2, -1.5, -1. During the sweep PRCL/MICH gain was tweaked so that the gain is reduced.
Nominal locking gain was PRCL x+2.5/MICH -30 . During the sweep they were +2.2 / -12
PRCL FM2/4/5 ON, Later FM3/6 turned on and no problem.
- Moved to -0.9, .... , and finally to 0.
- Automation of the PRMI+one arm
- PRMI locking with BS/PRM
- Better sensing matrix
- PRMI+two arms
- Use of the DC signals form the transmission monitors. (High power /low power transmon).
AWESOME! You guys rock.
Our RF Switch arrived today, and we mounted it in rack 1Y1 (1st attachment).
We connect our input fiber and all of our output fibers to our 1x16 optical splitter (2nd attachment). Note that the 75 meter fiber we are using for the splitter's input is in a very temporary position (3rd attachment - it's the spool).
We successfully turned our laser on and tested the optical splitter by measuring output power at each fiber using our Thorlabs PM20 power meter. Data was taken with the laser running at 67.5 mA and 24 degrees Celsius:
Detector name Power
Last night, I took sensing matrix data at various different offsets for the Yarm. The sensing matrices I measured were of the PRMI, while the Yarm was (a) Held off resonance, (b) Held at ~50% peak power, and (c) Held on resonance.
The dither lines were clear in the MICH and PRCL spectrum, so I think I'm driving hard enough, but something else seems funny, since clearly the REFL165 I and Q signals were not completely overlapping last night. If they were, we wouldn't have been able to lock the PRMI using REFL 165 I&Q.
Anyhow, here's the data that was taken. Data folder is ...../scipts/LSC/SensingMatrix/SensMatData/
Yarm off resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_012848.dat
Yarm at ~50% resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013937.dat
Yarm on resonance, SensMat_PRMI_1000cts_580Hz_2013-07-18_013619.dat
Hmm. I agree that something was funny.
Let's take the matrix without the arms and confirm the measurement is correct.
I have been working on setting up a QPD which can eventually be used to calibrate the PZT, and also orient the PZT in the mount such that the pitch and yaw axes roughly coincide with the vertical and horizontal.
The calibration constants have been determined to be:
X-axis: -3.69 V/mm
I initially tried using the QPD setup left behind by Chloe near MC2, but this turned out to be dysfunctional. On opening out the QPD, I found that the internal circuitry had some issues (shorts in the wrong places etc.) Fortunately, Steve was able to hand me another working unit. For future reference, there are a bunch of old QPDs which I assume are functional in the cabinet marked 'Old PDs' along the Y-arm.
I then made a circuit with which to read out the X and Y coordinates from the QPD. This consists of 4 buffer amplifiers (one for each quadrant), and 3 summing amplifiers (outputs are A+B+C+D = sum, B+C-A-D = Y-coordinate, and A+B-C-D = X-coordinate) that take the appropriate linear combinations of the 4 quadrants to output a voltage that may be calibrated against displacement of the QPD.
The output from the QPD is via a sub-D connector on the side of the pomona box enclosing the PD and the circuitry, with 7 pins- 3 for power lines, and 4 for the 4 quadrants of the QPD. It was a little tricky to figure the pin-out for this connector, as there was no way to use continuity checking to map the pins to quadrants. Therefore, I used a laser pointer, and some trial and error (i.e. shine the light on a given quadrant, and check the sign of the X and Y voltages on an oscilloscope) to map the pin outs. Steve tells me that these QPDs were made long before colour code standardisation, but I note here the pin outs in any case for future reference (the quadrant orientations are w.r.t the QPD held with all the circuitry above it, with the active surface facing me):
Green = GND
Blue = Upper Left Quadrant
White = Upper Right Quadrant
Purple = Lower Left Quadrant
Grey = Lower Right Quadrant
Chloe had noted that there was some issue with the voltage regulators on her circuit (overheating) but I suspect this may have been due to the faulty internal circuitry. Also, she had used 12 V regulators. I checked the datasheet of the QPD, Op-Amp LF347 (inside the pomona box) and the OP27s on my circuit, and found that they all had absolute maximum ratings above 18V, so I used 15V voltage regulators. The overheating problem was not a problem anymore.
I then proceeded to arrange a set up for the calibration (initially on the optical bench next to MC2, but now relocated to the SP table, and a cart adjacent to it). It consists of the following:
Having set everything up and having done the coarse alignment using the mirror mount, I proceeded to calibrate the X and Y axes of the QPD using the translational stage. The steps I followed were:
The plots are attached, from which the calibration values cited above are deduced. The linear fits for the orthogonal axis were done using cftool. There is some residual coupling between the X and Y motions of the QPD, but I think this os okay my purposes.
My next step would be to first tweak the orientation of the PZT in the mount while applying a small excitation to it in order to decouple the pitch and yaw motion as best as possible. Once this is done, I can go ahead and calibrate the angular motion of the PZT in mrad/V.
Yesterday, I mounted the first PZT in one of the modified mounts, and then glued a 2-inch Y2 mirror on it using superglue.
-The mirror is a 2-inch, Y2 mirror with HR and AR coatings for 532 nm light.
-The AR side of the mirror had someone's fingerprint on it, which I removed (under Manasa's guidance) using tweezers wrapped in lens cleaning paper, and methanol.
-Before gluing the mirror, I had to assemble the modified mount. Manasa handed over the remaining parts of the mounts (which are now in my newly acquired tupperware box along with all the other Piezo-related hardware). I took the one labelled A, and assembled the holder part. I then used one of the new mounts (2.5 inches, these are with the clean mounts in a cardboard box in the cupboard holding the green optics along the Y-arm) and mounted the holder on it.
-Having assembled the mount, I inserted the piezo tip-tilt into the holder. The wedge that the machine shop supplied is useful (indeed required) for this.
-I then cleaned the AR surface of the mirror and the top-surface of the tip-tilt.
-The gluing was done using superglue which Steve got from the bookstore (the remaining tube is in the small fridge). We may glue the other mirror using epoxy. I placed 4 small drops of superglue on the tip-tilt's top surface, placed the mirror with its AR face in contact with the piezo, and applied some pressure for a short while until the glue spread out fairly evenly. I then left the whole setup to dry for about half an hour.
-Steve suggested using a reference piece (I used two small bolts) to verify when the glue had dried.
-Finally, I attached the whole assembly to a base.
Here it is in action in my calibration setup (note that it has not been oriented yet. i.e. the two perpendicular axes of the piezo are for the time being arbitrarily oriented. And maybe the spreading of the glue wasn't that even after all...):
Yesterday, while setting stuff up, I tested the piezo with a 0.05 Hz, 10Vpp input from the SR function generator just to see if it works, and also to verify that I had set up all my electronics correctly. Though the QPD was at this point calibrated, I did observe periodic motion of both the X and Y outputs of my QPD amp! Next step- calibration...
I carried some further modifications and tests to the AI Board. Details and observations here:
I think the board is okay to be used now.
Here I have included the full schematic (so far) of the proposed ISS. There are two sheets: the first schematic details the filter stages and their accompanying circuitry while the second schematic details the RMS threshold detection and subsequent triggering.
The first schematic is fairly self explanatory as to what different portions do, and I have annotated much of the second schematic as there are some non-traditional components etc.
I have not yet included some mechanism to adjust the threshold voltage in real time or any of the power regulation, but these should follow fairly quickly.
I have managed to orient the PZT in the mount such that its axes are approximately aligned with the vertical and the horizontal.
In the process, I discovered that the 4 screws on the back face of the PZT correspond to the location of the piezoelectric stacks beneath the tip-tilt platform. The PZT can therefore be oriented during the mounting process itself, before the mirror is glued onto the tip-tilt platform.
In order to verify that the pitch and yaw motion of the mirror have indeed been roughly decoupled, I centred the spot on the QPD, fed to the 'pitch' input of the PZT driver board (connected to channel 1 of the PZT) a 10 Vpp, 1 Hz sine wave from the SR function generator (having turned all the other relevant electronics, HV power supply etc ON. The oscilloscope trace of the output observed on the QPD is shown. The residual fluctuation in the Y-coordinate (blue trace) is I believe due to the tilt in the QPD, and also due to the fact that the PZT isnt perfectly oriented in the mount.
It looks like moving the tip-tilt through its full range of motion takes us outside the linear regime of the QPD calibration. I may have to rethink the calibration setup to keep the spot on the QPD in the linear range if the full range is to be calibrated, possibly decrease the distance between the mirror and the QPD. Also, in the current orientation, CH1 on the PZT controls YAW motion, while CH2 controls pitch.
Path to data (retreived using getdata)
Data retrieved using getdata (30 minutes trend) saved at
I found CDS rt processes in red. I did 'mxstreamrestart' from the medm. It did not help. Also ssh'd into c1iscex and tried 'mxstreamrestart' from the command line. It did not work either.
I thought restarting frame builder would help. I ssh'd to fb. But when I try to restart fb I get the following error:
controls@fb ~ 0$ telnet fb 8088
telnet: connect to address 192.168.113.202: Connection refused
daqd was restarted.
- tried telnet fb 8088 on rossa => same error as manasa had
telnet fb 8088
- tried telnet fb 8087 on rossa => same result
telnet fb 8087
- sshed into fb ssh fb
- tried to find daqpd by ps -def | grep daqd => not found
ps -def | grep daqd
- looked at wiki https://wiki-40m.ligo.caltech.edu/New_Computer_Restart_Procedures?highlight=%28daqd%29
- the wiki page suggested the following command to run daqd /opt/rtcds/caltech/c1/target/fb/daqd -c ./daqdrc &
/opt/rtcds/caltech/c1/target/fb/daqd -c ./daqdrc &
- ran ps -def | grep nds => already exist. Left untouched.
ps -def | grep nds
- Left fb.
- tried telnet fb 8087 on rossa => now it works
The StripTool plot attached below shows various arm signals measured with the Y arm cavity swept using ALS.
Blue: ALS additive OFFSET to the error signal
Red: Raw PDH error signal (POY11I)
Purple: Linearized PDH error (POY11/TRY)
Green: 1/Sqrt(TRY)-5 (No normalization)
Inverse Sqrt of the TRY had been implemented when this LSC controller was first coded.
It is confirmed that the calculation is working correctly.
I mounted the second PZT in a modified mount, and then glued a 1-inch Y2 mirror on it using superglue.
-The mirror is a Laseroptik 1-inch, Y2 mirror with HR and AR coatings for 532 nm light.
-The procedure for mounting the mirror was the same as detailed in elog 8874. This time, I tried to orient the Piezo such that the four screws on the back face coincided with the horizontal and vertical axes, as this appeared to (somewhat) decouple the pitch and yaw motion of the tip-tilt on the first PZT.
-One thing I forgot to mention in the earlier elog: it is best to assemble the mount fully before inserting the tip-tilt into it and gluing the mirror to the tip-tilt. In particular, the stand should be screwed onto the mount before inserting the tip-tilt into the holder, as once it is in, it will block the hole through which one can screw the stand onto the mount.
I recalibrated the QPD today as I had shifted its position a little. I then identified the linear range of the QPD and performed a preliminary calibration of the Piezo tip-tilt within this range.
-I recalibrated the QPD as I had shifted it around a little in order to see if I could move it to a position such that I could get the full dynamic range of the piezo tilt within the linear regime of the QPD. This proved difficult because there are two reflections from the mirror (seeing as it is AR coated for 532nm and I am using a red laser). At a larger separation, these diverge and the stray spot does not bother me. But it does become a problem when I move the QPD closer to the mirror (in an effort to cut down the range in which the spot on the QPD moves). In any case, I had moved the QPD till it was practically touching the mirror, and even then, could not get the spot motion over the full range of the PZTs motion to stay within the QPD's linear regime (as verified by applying a 20Vpp 1Hz sine wave to the PZT driver board and looking at the X and Y outputs from the QPD amplifier.
-So I reverted to a configuration in which the QPD was ~40cm away from the mirror (measured using a measuring tape).
-The new calibration constants are as follows (see attached plots):
X-Coordinate: -3.43 V/mm
Y-Coordinate: -3.41 V/mm
-I then determined the linear range of the QPD to be when the output was in the range [-0.5V 0.5V].
-Next, at Jenne's suggestion, I decided to do a preliminary calibration of the PZT within this linear range. I used an SR function generator to supply an input voltage to the PZT driver board's input (connected to Channel 1 of the piezo). In order to supply a DC voltage, I set a DC offset, and set the signal amplitude to 0V. I then noted the X and Y-coordinate outputs, being sure to run through the input voltages in a cyclic fashion as one would expect some hysteresis.
-I did this for both the pitch and yaw inputs, but have only superficially analysed the latter case (I will put up results for the former later).
-There is indeed some hysteresis, though the tilt seems to vary linearly with the input voltage. I have not yet included a calibration constant as I wish to perform this calibration over the entire dynamic range of the PZT.
-There is some residual coupling between the pitch and yaw motion of the tip tilt, possibly due to its imperfect orientation in the holder (I have yet to account for the QPD's tilt).
-I have not included a graphical representation here, but there is significantly more pitch to yaw coupling when my input signal is applied to the tip-tilts pitch input (Channel 2), as compared to when it is input to channel 1. It is not clear to me why this is so.
-I have to think of some smart way of calibrating the PZT over its entire range of motion, keeping the spot in the QPD's linear regime throughout. One idea is to start at one extreme (say with input voltage -10V), and then perform the calibration, re-centering the spot to 0 on the QPD each time the QPD amp output reaches the end of its linear regime. I am not sure if this will work, but it is worth a shot. The other option is to replace the red laser with a green laser (from one of the laser pointers) in the hope that multiple reflections will be avoided from the mirror. Then I will have to recalibrate the set up, and see if I can get the QPD close enough to the mirror such that the spot stays within the linear regime of the QPD. More investigation needs to be done.
QPD Calibration Plots:
Piezo tilt vs input voltage plots:
Yaw Tilt Pitch Tilt
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.
Yesterday and today I was in the lab doing many cavity scan.
First I did many measurement with the cavity aligned in order to get the position of the 00 modes, then I misaligned the beam in many different ways to enhance the higher order modes.
In particular, I first misaligned the mode cleaner to make the beam clipping into the Faraday. To do this, I set to 0 the WFS gain, but I left the autolocker still enabled. In this way, the autolocker couldn't bring the mirrors back to the aligned position.
Then I misaligned also the TT2 to get even more HOMs.
Eventually, Rana came and we misaligned TT1 to clip the beam, and using TT2 we aligned back the beam to the arm.
To increase the SNR, we changed the gain of the TRY PD, setting it to 20dB (which corresponds to a factor 100 in digital scale)
I attached one scan that I did with Rana on Sunday night. I could not upload a better resolution image because the file size was too big, but here's the path to find all of the scans:
There are many folders, one per each day I measured. In each folder there are measurements relative to aligned cavity, Pitch and Yaw misalignment.
The PDA520 used for TRY was set to 0 dB analog gain. This corresponds to ~500 counts out of 32768. The change to 20 dB actually increases the gain by 100. This makes the single arm lock saturate at ~25000 counts (obviously in analog before the ADC). The right setting for our usual running is probably 10 dB.
For the IMC WFS, we had disabled the turn on in the autolocker to use the IMC to steer the beam in the FI, but that was a flop (not enough range, not enough lever arm). In the end, I think we didn't get any clipping.
Trying to take an image or movie of the ETMY Transmon cam, we got instead this attached image.
I think it is just some scattered green light, but others in the control room think that it is a message from somewhere or someone...
It is not an angel, it is clearly a four leaf clover (also known as "quadrifoglio"). It is very rare, it brings good luck!
[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
The results of today's MC spot position measurements:
spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[2.3244717046516197, -0.094366247149508087, 1.6060842142158149, -0.74616561350974353, -0.67461746482832874, -1.3301448018100492]
MC1 and MC3 both have spots that are a little high in pitch, but everything else looks okay.
I have just centered IPPOS, as well as PSL POS and PSL ANG (also called IOO POS and IOO ANG on the screens). Annalisa is working on placing mirrors to get the IPANG beam to its QPD, so that one will be centered later.
Green steering mirrors have been swapped with PZT mirrors at the X end table. We aligned the green to the X arm.
X arm green transmission +PSL green ~ 0.95
That's better than before the swap...woohooo
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.
I have some data for how much motion of any PRMI-relevant optic affects the beam seen by the POP QPD.
For this, I am using the QPD calibration from the micrometer (elog 8851) to get me from counts to mm of motion. Note that the pitch calibration hasn't been redone (I tried locking the PRMI this afternoon, but ITMX kept drifting away from me**, so I didn't get any more data.) The pitch calibration is obviously very rough, since I only have 2 points defining my fit line.
Anyhow, if we assume that's close enough to get us started, I now have a calibrated QPD spectrum:
As detailed in elog 8854, I took single frequency transfer functions, to determine the effect at the QPD from shaking any single PRMI optic. These transfer functions gave me a conversion factor between the optics' oplev readings (in microradians) to the counts seen at the QPD. I used this number, as well as the QPD calibration from the micrometer data, to convert each optics' oplev spectra to motion that one would expect to see at the QPD.
I have not yet completely figured out how to make an estimate of the PR folding optics' affect on the POP QPD spot position, if I know their motion. The current plan is to do as Den did in elog 8451, and infer the PR2/3 motion from the ITMX/BS motion measured by the oplevs. My plan was to take the spectra of the oplev signals while the BS/ITMX are undamped, divide by the SOS pendulum transfer functions, then multiply by the TT transfer functions (which I finally wrote down in elog 8564). I'm planning on using the undamped data, since the oplev signals are still within the linear range of the oplev QPDs, and I won't have to take the SUS damping into account. Anyhow, after I do that, I'll have an idea of how much the tip tilts are moving, but not what that does to the cavity axis.
However, after looking at the plots below, it seems like the PRM is the main culprit causing the PRC axis motion, although the BS (and to a smaller extent the ITMs) are not innocent. Since the plots get very busy very quickly, I have many plots, each plot comparing one of the above QPD spectra (either pitch or yaw) with a single optics' oplev inferred motion.
EDIT: After talking with Koji, I realize that, since the ASC was engaged during the PRM oplev spectrum measurement, I cannot yet say whether the motion is due to PRM, or if it is from PR2 or PR3, and imprinted on the PRM via the ASC servo. The lump where the PRM-caused motion is greater than the QPD spectra is entirely in the region where the ASC is active. So, the QPD motion I expect without the ASC would be something like the green trace in the PRM comparison plots. The blue trace is then the closed loop measurement. Since the ITMs and BS are below the closed loop values, they aren't the ones causing the big lump. I should retake all of these spectra at a time when the PRMI is locked, but the ASC is not engaged. I'm not sure if I'll have a chance to do that tonight or not. If I can find some GPS times when the PRMI was locked, before we had ASC, I can get the oplev data.
I think part of the reason PRM is dominating is that it's damped motion is ~10x greater than any other optics', most noticeably the BS'. I'll write a quick separate elog about this. Also, note that the ~3Hz resonant gain had been turned off in the PRM oplev loop, but not in any other loops. This is why there isn't the sharp dip in the PRM's oplev motion. Also, since the PRM ASC was engaged for this measurement, and the ASC pushes on the PRM to minimize the QPD motion, it isn't totally crazy that the PRM's motion is greater than what we actually see at the QPD, if it is compensating for the motion of other optics.
** Re: PRMI locking this afternoon, it was almost as if ITMX were bi-stable. I aligned both arms, to set the ITM positions. Then, I would lock and tweak up the michelson to get the AS port nice and dark (usually touching ITMX today, since it seemed like the drifter....ITMX at this point was usually between -7 and -15 microradians in pitch from the center of the oplev QPD). When I then brought the PRM back into alignment, ITMX was starting to drift away. As soon as I hit the LSC Enable switch, and looked back over to the OpLev screen, ITMX was misaligned, usually around -65 urad in pitch. I did this circus probably 3 or so times before giving up. Koji said that he had seen this bi-stability before, but he didn't remember what fixed it. The drifting that Koji mentioned in elog 8801 seems to have been fixed by centering all the PRMI oplevs every day, but I had already done that, and was still seeing ITMX drift.
Centering of the oplev beams: done
Recording the OSEM values: done
There seems to be an unexplained oscillation in X arm cavity transmission for IR when the cavity is locked using the POX error signal.
Their origin is not related to the oplevs because the oscillation does not exist when LSC is OFF and the arms are controlled only by the oplevs and OSEMs.
In light of recent events and the decision to test the piezo tip-tilts for green beam steering on the X-end table, I have set up 8 excitation points to channels 8 through 15 of the DAC on c1scx (as was done earlier for the DAC at 1Y4 with Jenne's help) in order to verify that the pin-outs of the DAC interface board. I have not yet compiled the model or restarted the computer, and will do these tomorrow, after which I will do the test. The channels are named YYY_CHAN9 etc.
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