[Manasa, Jenne, Annalisa]
I was going to find the beat note to start the cavity scan, but I couldn't.
These are the steps I followed:
After spanning the temperature by approximately 4degC, we started be suspicious that I couldn't find the beat in the range of temperature where it was supposed to be found, and we started making several trials:
The same trials were done also for the X arm, but we didn't succeed in finding the beat for the X neither.
I found the beat note for X arm. I did not change anything this morning (to the best of my knowledge). Hooking up the spectrum analyzer, I could find the beatnote signal at the PD RF output, after the amplifier and also at the MON port of the beatbox. I still don't know what changed from the last night set of trials
I found the beat note for the Y arm. Nothing was changed with respect to yesterday night, but the beat is back!
Craig, Gautam and Steve,
Single mode fiber 50m long is layed out into cable tray that is attached to the beam tube of the Y arm.
It goes from ETMY to PSL enclosure. It is protected at both ends with " clear- nylon slit corrugated loom tubing " 1.5" ID
The fiber is not protected between 1Y1 and 1Y4
Installed 0.5" ID 10 ft long protective tubing at the PSL end of the ETMY fiber this morning. Here I had to cable tie a bunch of cables at the east side of the PSL enclosure.
They were hanging off the table blocking space were the sliding doors move.
At the ETMX end of the X-arm fiber received the same protective tubing.
I ran a series of diagnostics on the X arm ALS to look at how the beatbox behaves after the makeover.
Diagnostic tests run:
1. X arm ALS in-loop spectrum
2. X arm ALS out-of loop spectrum
3. X ALS scan of the X arm cavity
The noise suppression looks better after the makeover at the lower frequencies. To suppress the noise at high frequencies, we would have to add more whitening filters.
[Annalisa, Jenne, Nic]
After having troubles with the Xarm earlier (maybe Manasa can write/say something about this? Something about perhaps seeing the phase tracker jump, and cause it to lose lock?), we moved on to the Y arm.
Annalisa locked the Yarm green, and closed the ALS loop. I believe that earlier today, she tuned the gain such that we don't start getting gain peaking at a few hundred Hz. We would like to get a script going, so that it's not so labor intensive to reclose the ALS loop after an MC lockloss....but that's a daytime task.
We then found the IR resonance, using only the Yarm ALS system. After Manasa's work yesterday, the Yarm was very stable while locked with the ALS. We took a power spectrum of POY11_I_ERR, which I have calibrated using the number in elog 6834 of 1.4e12 cts/m, or 7.14e-13 m/ct. See the figure below.
After that, we changed the offsetter2 offset such that the arm was off resonance, but not so far off that we crossed any significant resonances (in particular, we wanted to not go as far as the 55MHz resonance).
Then, I tried to lock the PRMI for a while, but the alignment wasn't very good. We knew that the Yarm was well aligned, since our IR resonance was > 0.98, but it had been a while since we had aligned the X arm. I tweaked the ITMX position to make the Michelson dark, and then tried acquiring PRMI lock. At first, I tried with REFL165 I and Q, but with the non-ideal alignment and the offset in the 165 diode (LSC offsets was not run this evening), I wasn't catching any locks. I then switched to AS55Q and REFL33I, but wasn't able to catch lock there either.
The MC lost lock, which made us lose the ALS loop, but the ALS had been locked for more than 30 minutes, at least. I tried locking the PRMI with the current alignment (after having misaligned ETMY), but was only able to get lock stretches of 1 second at maximum.
We are calling it a great success for the night, since we have confirmed that, at least for the Yarm, Manasa's beatbox work has improved things. Also, we have a pretty solid plan for trying the PRMI+arm tomorrow, even though it didn't work out tonight.
We knew that the Yarm was well aligned, since our IR resonance was > 0.98, but it had been a while since we had aligned the X arm.
The X arm was locked with TRX>0.98 earlier last night while I was measuring the out of loop noise of the phase tracker.
ETMY optical table top was grounded to the ETMY chamber through 1 Mohms this morning. I also strain releifed relieved a few cables that were pulling on components directly.
There are 4 oscilloscopes left on the AP optical table top.... It's only 25 lbs... Do not leave anything on the optical table tops!
We mounted our Laser Module and Laser Power Source in rack 1y1. We plan to add our RF Switch and Transformer Module to the rack, as pictured. (Note: drawn-in boxes in picture are approximately to scale.) Note that the panel of knobs which the gray boxes overlap is obsolete and will soon be removed.
There are essentially two major portions of the ISS I am designing. One system has the voltage reference, differential amplifier and filtering servo (schematic attached) while the other has a comparator circuit and a triggering mechanism. The first system amplifies an error signal obtained from the PD output and the voltage reference, which is then fed back through the AOM. I've done a lot of work designing/prototyping this first half and now I'm starting to design the second half.
The second system's main purpose is to maintain loop stability as the ISS is engaged. Let's assume a user has decided they want noise suppression. They would first close the ISS feedback loop and an error signal would pass through three unity-gain buffers, providing minimal noise reduction. The user can then send a signal to theTRIGGER 1 port to switch the first stage from its unity-gain position to its filtering position and reduce the intensity noise further. This signal will most likely be digital in origin. Alternatively, when the user first closes the ISS loop, the first stage can already be in its filtering position rather than necessitating two commands.
A test channel (not drawn in the included schematic) will monitor the RMS level of the incoming signal from the PD. This noisy AC signal will first be amplified and then passed through an RMS-to-DC converter. The resulting DC signal is used as a part of the triggering mechanism for later stages. Once the first stage has been switched manually, and the DC signal corresponding to RMS noise of the PD output drops below a certain threshold, stages 2 and 3 will be internally triggered with a short delay between them. Toward being able to detect this threshold, I have designed a simple comparator circuit with an LT1016. The circuit has a fairly low-level output when the input voltage is larger than the threshold (about 1.6 V for my simple prototype), but when the input passes below the threshold, the comparator puts out almost 4 V, a number limited by the supply voltage. The schematic is shown below.
The component V2 and the various voltage dividers serve to establish the reference/threshold voltage. Note that although the LT1016 is not powered in the schematic, it requires ±5 V (a max of 7 V). The above circuit was also prototyped on a breadboard and I characterized it with an oscilloscope. Using a CFG253, I made a low frequency (~0.3 Hz) triangle wave with an amplitude and DC offset such that it oscillates between 0 and 5 V. This was applied to the IN node in the above schematic. The input waveform and the circuit's response (voltage at the OUT node) are shown below. As expected, R2 serves to establish hysteresis. The comparator switches to 'high' output until the input drops below 1.6 V, and then it doesn't switch back to the 'low' output until the input goes up to ~3.4 V.
This behavior is ideal for our application as we can detect when the DC signal from the RMS-to-DC converter drops below a certain level (i.e. the first stage that has been activated does some amount of filtering to lower RMS noise), and then we can trigger subsequent filter stages off of the comparators high-level output.
This circuit could easily be used to drive the MAX333a switches shown in the first schematic attached. I believe the low-level output is not sufficient to switch the MAX333a although the ~4 V high-level output is quite sufficient. Regardless, these exact values (thresholds, outputs etc) will be determined after I have a better idea of the RMS noise of the laser without any intensity stabilization as well as a solid understanding of how the AD8436 RMS-to-DC converter works. This was simply a proof of concept for lower threshold detection using basic Schmitt trigger topology.
Yesterday I did a cavity scan with IR while holding the Yarm with green.
ALS servo tuning:
The gain of the loop is set such that BEATY_FINE_Q_ERR x GAIN = 120k. This is a kind of "empirical low" in order to have the UGF around 1kHz.
Start with FM5 [1000:1] enabled, determine the sign of the gain increasing it in small steps and making sure that the mirror doesn't get a kick. Then gradually raise it while looking at the BEATY_PHASE_OUT power spectrum.
Enable FM7 [RG16.5], FM6 [RG3.2], FM3 [1:5], FM2[0:1], FM10 [40:7].
Plot 1 shows the power spectrum of BEATY_PHASE_OUT (calibrated in Hz).
Offset setting and cavity scan
The C1ALS_OFFSETTER2 was used to set an offset for ALS scan.
Many scans have been done to find the optimal offset conditions, I only attached one (Plot 2).
I also misaligned the END mirror in pitch to enhance the HOMs peaks, but it turned out that it was not enough, because I didn't see a very big difference between the "aligned" and the "slightly misaligned" measurements (Plot 3).
Increase the cavity misalignment both in pitch and in yaw and repeat the measurement.
[Koji, Manasa, Annalisa]
I made several trials to scan the arm on the IR TEM00 resonance while the PRMI was held with REFL165I&Q.
It was so hectic to keep multiple systems running correctly. We talked about how it should be automated.
We'll gradually offload the switching works on scripts.
In a good alignment condition, when I swept on the resonance, everytime the PRMI lost the lock. It reacquired
once the arm passed the resonance.
Lately I got difficulty to acquire lock of the PRMI while the arm is waiting at its off resonance.
If I change the ALS offset I got a stable lock in a certain offset, and did not get in another offset
so there could be something systematic. (The arm was in between the carrier resonance and the next sideband (55MHz) resonance).
- Run LSCoffset script.
- Misalign PRM. Lock and align the arms with ASS.
- Go into the tables. Align the oplevs for ETMX/Y, ITMX/Y, and BS. (Very important for alignment stability)
- Align PRMI and lock PRMI. Unlock once.
- Go into the BS/PRM table. Align the oplev for PRM.
- Misalign PRM by -0.2
- Find the beat note at around 50MHz by changing the Yarm SLOW control. Today the PSL SLOW was ~0.24, and the Yarm SLOW was -10981.
- Reset Phase Tracker History (Important)
- Engage Yarm ALS with FM5. Tested the sign of the servo by giving 0.01 or -0.01. In my case, the negative number worked fine.
Gradually increase the gain up to -10. Turn on FM2/3/6/7/10.
- Use Filter module "C1ALS-OFFSETTER2" to give the ALS sweep. I used FM1 (30mHz LPF). Change the offset while looking at the IR TRY and POY11 error signal.
- Once the resonance is found, shift the beat note by giving +10 or -10 offset.
- While the arm is kept off resonance, align PRM.
- Lock PRMI with REFL33I and AS55Q. Turn on PRM ASC.
- Once the stable lock is obtained, switch the input signals to REFL165I&Q. I used REF33I x1.0->REFL165I x0.8 and AS55Q x1.0 -> REFL165Q x0.5
[PRMI + one arm]
- Revert the ALS offset by 10 to bring the arm on the resonance the see what happens.
Alex and Steve,
Old halogen chamber illuminator cabling disconnected and potenciometer board removed at 1Y1 in order to give room for pd calibration fibre set up.
During the process, they had also removed the power cable to the ITMY camera. Steve and I fixed this...so the camera is back.
I went out on the floor to look at the transmitted signal from the PMC to get a rough idea of the noise of the unstabilized laser. There was already a scope hooked up so I just used the measurement features to find the following:
Signal average = 875 mV. Peak-to-Peak noise = 45 mV
Assuming the noise can be approximated as Gaussian noise, the heuristic for converting to RMS noise of the signal is RMS = Peak-to-Peak / 8 (or Peak-to-Peak / 6, I've used both...)
-> RMS Noise ~ 6.5 mV
When designing my filtering stages and RMS detection/triggering, I'll use relative RMS, i.e. 6 mV / 875 mV = 0.007, as a measure of unstabilized laser noise.
We talked about how it should be automated.
We'll gradually offload the switching works on scripts.
Here is the list of automations that we need to work on for less hectic PRMI+ALS trials.
1. Enable/Disable ASC when PRMI is locked/unlocked.
2. Smooth transfer from REFL33/AS55 to REFL165 when PRMI is locked.
3. Change actuation from the ITMs to BS and PRM after PRMI lock.
4. Enable ALS.
5. IR resonance scan using ALS.
It would be better to measure the power spectrum density of the fluctuation.
The RMS does not tell enough information how the servo should be.
In deed, the power spctrum density gives you how much the RMS is in the entire or a specific frequency range.
It would be better to measure the power spectrum density of the fluctuation.
The RMS does not tell enough information how the servo should be.
In deed, the power spctrum density gives you how much the RMS is in the entire or a specific frequency range.
I wanted the RMS noise simply to establish a very rough estimate of thresholds on RMS detectors that will be part of my device. If you refer to elog 8830, I explain it there. Essentially, when the ISS is first engaged, only one of the 2 or 3 filter stages will be active. Internal RMS threshold detection serves to create a logic input to switch subsequent filters to their 'on' stage.
These are the data, one plot for when the vertical QPD position was changed, and one for when the horizontal (yaw) QPD position was changed.
The micrometer is in inches, so 1 unit is 0.1 inches, I believe.
Clearly, I need to redo the measurement and take more data in the linear region.
[Annalisa, Koji, Manasa]
In order to improve the ALS stability we went ahead to check if we are limited by the sensor noise of ALS.
What we did:
RF signals similar to the beatnote were given at the RF inputs of the beatbox.
The frequency of the RF signal was set such that I_OUT was zero (zero-crossing point of the beatbox).
We measured the noise spectrum of the phase tracker output.
Plot 1: X ALS noise spectrum
Plot 2: Y ALS noise spectrum
The X arm ALS noise is not limited by the sensor noise...which means we shoudl come up with clever ideas to hunt for other noise sources.
But this does not seem to be the case for the Y arm ALS. The Y arm part of the beatbox is noisy for frequencies < 100Hz.
After looking into the details and comparing the X and Y arm parts of beatbox, it looks that amplitude of the beat signal seem to affect the Y arm ALS noise significantly and changes the noise spectrum.
Investigate the effect/limitations of amplitude of the beatnote on the X arm and Y arm beatbox.
I started doing a scan of the Y arm cavity with IR with ALS enabled.
The servo tuning procedure is basically the same as described in elog 8831.
This time I had a stronger beat note(-14 dBm instead of -24 dBm of the last measurement) thanks to a better alignment.
Plot1 shows the Power spectrum of the BEATY_PHASE_OUT. The RMS is smaller by a factor of 2 (400Hz), corresponding to a residual motion of about 25 pm.
Offset setting avity scan
In order to give an offset linearly growing in time, I used the ezcastep script instead of giving the offset in OFFSETTER2. If the ramp time is long enough, it is not necessary to enable the 30mHz filter.
To span 2 FSR, I started from an offset of 450 and I gave a maximum value of 1600 with a delay of 0.2s between two consecutive steps.
I did a first scan with the cavity well aligned, basically to know the position of the 00 peaks and choose the best offset range (Plot2)
Then I misaligned the TT2, first in PITCH and yhen in YAW, in order to enhance the HOMs. (Plot3 and Plot4)
More investigation and measurements needed.
Annalisa notified me that the MC autolocker could not keep the MC locked.
I found the initial alignment was not good and the MC was too much excited when the WFS kicked in.
There might have been the WFS offset issue due to the miscentering of the spots on the WFS diodes.
I used the usual procedure of the maintenance and it looked OK if I followed the switching procedure the mc autolocker suppoed to do.
I still could not get the autolocker running smoothly. I opened mcup script and compared what was the difference
between my manual sequence and what the script did. The only difference was the lines related to MCL.
It was still turning on the filter module. I checked the MCL path and found that the gain was not zero but 1.0.
So now the MCL gain is set to zero. This solved all the remaining issue.
Yesterday evening Nic and me were in the lab. The Mode Cleaner was unlocked, but after many attempt we could fix it and we did many scans of the Y arm cavity.
Today I was not able to keep the MC locked. Koji helped me remotely, and eventually the MC locked back, but after half an hour of measurements I had to stop.
I made some more scan of the Y arm though. I also tried to do the same for the X arm, but the MC unlocked before the measurement was finished. I'll try to come back in the night.
Pumpdown 75, vacuum normal condition at day 144
We are planning on testing our laser module soon, so we have added aluminum foil and a safety announcement to the door of OMC North. The safety announcement is as pictured in the attachment.
I tried to retake POP QPD calibration data again today. The MC was mostly fine, but whenever the PRMI unlocked, both ITM watchdogs would trip. I'm not sure what was causing this, but the ITM alignment wasn't perfect after this kind of event, so I felt like I was continuously locking and realigning the arms to get the alignment back. Then, after turning on the ASC and tweaking up the PRM alignment for maximum POP110I signal, I had to recenter the QPD, so none of my previously taken data was useful. Frustrating. Also, I had recentered the PRMI-relevant oplevs, but I had these weird locklosses even with nicely centered oplevs.
I have given up for the daytime, and will come back to it if there's a spot in the evening when arm measurements aren't going on.
Here is the data from last week, and the data from today. The micrometer readings have been calibrated into mm, and I have fit a line to the linear-looking region. Obviously, for the Pitch calibration, I definitely need to take more data.
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 firstname.lastname@example.orgHz, 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.
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.
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.
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.
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.
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
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.
[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