You have to correct this transimpedance ratio by correcting for the different levels of DC photocurrent in the two devices.
For the dark noise, you must always include a trace showing the noise of the measurements device (i.e. the analyzer noise must be less than the dark PD noise) with the same input attenuation setting.
Also, we still need to get a 32GB SD card for the new camera. It only has an 8GB one.
That seems like easily enough range; as long as we can put the TT into the middle of their range to start with we should be OK.
We should consider instrumenting the leakage transmission through all TT with a bare QPD on a stick. We can then use those sensors to monitor the spot positions within the input mirrors as well as the PRC / SRC.
Why would we use such a bad optic in our recycling cavity? Is 1.5% the spec for these mirrors? Is this the requirement that Kiwamu calculated somehow? Did anyone confirm this measurement?
I can't believe that we'll have low noise performance in a RC where we dump so much power.
During our 'Women in Physics' tours today, we were reminded that there are several bench power supplies being used as permanent inside.
Some are being used to power PZTs, AOMs, VCOs, RFPDs, etc. On Wednesday, after the meeting, we will all go inside and remove one and replace it with a fused, professional wiring to the rack power supplies. The temporary ones must be removed.
After sshing into several machines and doing 'sudo shutdown -r now', some of them came back and ran their processes.
After hitting the reset button on the RFM switch, their diagnostic lights came back. After restarting the Dolphin task on fb:
"sudo /etc/init.d/dis_networkmgr restart"
the Dolphin diagnostic lights came up green on the FE status screen.
iscex still wouldn't come up. The awgtpman tasks on there keep trying to start but then stop due to not finding ADCs.
Then power cycled the IO Chassis for EX and then awtpman log files changed, but still no green lights. Then tried a soft reboot on fb and now its not booting correctly.
Hardware lights are on, but I can't telnet into it. Tried power cycling it once or twice, but no luck.
Probably Jamie will have to hook up a keyboard and monitor to it, to find out why its not booting.
P.S. The snapshot scripts in the yellow button don't work and the MEDM screen itself is missing the time/date string on the top.
I have two questions:
1) Are we sure that the T measurement is not being compromised by some systematic? i.e. some leakage is making the apparent T appear too high.
2) IF the T is really so high, how should we decide whether or not to use this one rather than the G&H? Is the 532 nm property more important than the high recycling gain?
Gouy not Guoy:
pronounced Goo-eee, with the emphasis on the second syllable.
Very exciting result, if true. I suppose we should try to reconfirm this result by doing another phase map of PRM03.
Is it possible that PR2 is not flat? How would we test to see if the tip-tilt frame screw gives it a curvature? Perhaps we can check with COMSOL.
Getting closer, but need to use the real measured AR reflectivity values, not the 1500 ppm guess. These should be measured at the correct angles and pol, using an NPRO.
I would guess that either flipping PR2 or PR3 would give nearly the same effect (g = 0.9) and that flipping both makes it even more stable (smaller g). But what we really need is to see the cavity scan / HOM resonance plot to compare the cases.
The difference of 0.5% in mode-matching is not a strong motivation to make a choice, but sensitivity to accidental HOM resonance of either the carrier or f1 or f2 sidebands would be. Should also check for 2*f2 and 2*f1 resonances since our modulation depth may be as high as 0.3. Accidental 2f resonance may disturb the 3f error signals.
Use the trick I suggested:
Focus the beam so that the beam size at the detector is smaller than the beam separation. Use math to calculate the beam size and choose the lens size and position. You should be able to achieve a waist size of < 0.1 mm for the reflected beam.
I will check out the AS55 situation tomorrow. Just put it on my desk.
MC Autolocker was disabled - I enabled it.
For the F2P.py, you should look at how we did this with the script written 8 years ago in csh. There we stored the initial values in a file (so they don't get blow away if someone does CTRL-C). Your python script should have a trap for SIGINT so that it dies gracefully by restoring the initial values. In order to have the smooth value adjustment, you must first set the TRAMP field for all the coil gains to 2 and then switch. Make sure that the lockin ignores the first few seconds of data after making this switch or else it will be hugely biased by this transient.
For the PRM OL use as a F2A reference, you also have to take into account that the OL beam is hitting the PRM surface at non-normal incidence. IF it is a large angle, there will be a systematic error in the setting of the F2Y values.
Please confirm the SRM OL beam is not too bad and also find where the mis-aligned SRM puts its beam. WE want to be sure that there is not too much unwanted scattering from SRM into the PRFPMI.
Is the beam going towards the OMC going to cause backscatter because of uncontrolled OMC or can we park that beam somewhere dark?
This plot shows the trend of the OL during the past several hours of roughing pumping.
The big steps at the start of the pump down is NOT due to the pumping, but is instead the "recentering" that Yuta did. Looks like he was unable to find zero on the ETMY.
Some of the rest of the drift is probably just the usual diurnal variation, but there does seem to be some relation to the pumping trend. I guess that the shift of ~0.3 in the ITMX and ITMY pitch is real and pressure related.
We need to figure out how to put the OL calibration factor into the SUS-OL screens.
According to Google, you can add a line in the crontab to backup the crontab by having the cronback.py script be in the scripts/ directory. It needs to save multiple copies, or else when someone makes the file size zero it will just write a zero size file onto the old backup.
This looks pretty good already. Not sure if we can even measure anything reasonable below 0.1 Hz without a lot of thermal shielding.
The 10-20 kHz oscillation may just be the loop shape of the opamp. I think you saw similar effects when using the AD743 with high impedance for the OSEM testing.
I asked John Z to talk with Jamie and then install a new NDS2 server software for us. Jamie may know if this happened or was foiled by the linux1 RAID failure.
In any case, our pyNDS stuff ought to be able to talk to NDS2 or our old NDS1 stuff, I hope.
That's good news. I was ready to give up and say we should vent and remove the baffles. It will be interesting if you can find out how much the sensors and OL and IPANG are off from their pre-pump values. We should think about how to have better references.
Also, what is the story with the large drift we are seeing in IPANG?
If its true that there have been large flashes, then there indeed might be beer. But first I'd have to see a calibrated plot. And make sure that the flashes are not overamplified due to a whitening filter imbalance.
Is it the readout of a PD with no whitening/antiwhitening? IF so, its much easier to believe.
At first I thought that this was goofy, but then I logged in and saw that Megatron only has 8GB of RAM. I guess that used to be cool in the old days, but now is tiny (my laptop has 8 GB of RAM). I'll see if someone around has some free RAM for a 4600; in the meantime, I've killed a MEDM that was running on there and using up a few hundred MB.
Run your ssh-MEDMs elsewhere or else I'll make a cronjob to kill them periodically.
Don't use resonant gain - it can lead to a loop instability since it makes the loop have 3 UGFs.
Just use a elliptic bandstop filter at this harmonic frequency separately for each test mass. There are many detailed examples of this in elog entries from Rob and I over the past ~10 years. This bandstop should get clicked on automatically after lock acquisition.
I took the two 'flat' 2" mirrors over to Downs and Garilynn showed me how to measure them with the old Wyko machine.
The files are now loaded onto our Dropbox folder - analysis in process. From eyeball, it seems as if the RoCs are in the neighborhood of ~5 km, with the local perturbations giving ~10-15 km of curvature depending upon position (few nm of sage over ~1 cm scales)
Koji's matlab code should be able to give somewhat more quantitative answers...
Ed: Here you are. "0966" looks good. It has RoC of ~4km. "0997" has a big structure at the middle. The bump is 10nmPV (KA)
Whereas the sensing matrix coefficients for ITMX/ITMY in REFL_I indicate an actuation imbalance, the disparity in the ITMX/ITMY to AS_Q elements does not. However, they do indicate why there is a PRM to AS_Q coupling at all.
I would recommend setting up the triggering so that the REFL & AS whitening is turned on AFTER lock acquisition and using a frequency of ~100-300 Hz for the sensing matrix measurement to fix these issues.
How about posting a logic flow diagram? Is the idea to trigger only on the power signals to determine the lock state? Is the hysteresis going to be done in the same way as the main filter bank triggers?
Please stop power cycling computers. This is not an acceptable operation (as Jamie already wrote before). When you don't know what to do besides power cycling the computer, just stop and do something else or call someone who knows more. Every time you kill the power to a computer you are taking a chance on damaging it or corrupting some hard drive.
In this case, the right thing to do would be to hook up the external keyboard and monitor directly to c1sus to diagnose things.
NO MORE TOUCHING THE POWER BUTTON.
I doubt that it has truly disappeared. Can you please make a measurement of it and quantify the hysteresis using some angle sensor?
I measured the dark noise and regular intensity noise in MC trans tonight to get some estimate for the free running spectrum that the Chas ISS must overcome. PDF is attached.
XML file is /users/rana/dtt/MC-trans_130325.xml
The RIN normalization was done by using the mean of the SUM time series. The dark noise was measured by misaligning MC2 and making the same measurement with the bright normalization.
Please attach the data file of the measurement - its hard to get the real information out of picture. In general, WE should always include the code / explanation of how to reconstruct the plot and get the scientific information out.
A key step was turning off the whitening filters. With the previous setting (G = 15 dB, white on), the error signals (post anti-whitening) had amplitudes of ~500 counts. This means that they can go as high as (150/15)^2 * 500 = 50000 counts on the ADC.
The purpose of the whitening filter is to match the noise / range of the signal to the ADC. What we would like to do is use the minimum gain so as to make the RFPD electronics noise + shot noise be ~equal to the ADC noise. i.e.
sqrt(V_PD^2 + v_shot^2) * G_white = V_ADC
The RFPD noise is ~3 nV before the internal preamp. The MAX4107 has a gain of 10. There is a factor of 1/2 from the voltage division of the RFPD's 50 Ohm series resistor and the input impedance of the mixer. There is also a power splitter between the PD output and the mixer which gives us a 3 dB loss. The mixer has a conversion loss of ~5-6 dB depending upon the LO level.
V_PD = 3e-9 * (10 * 1/2 * 1/sqrt(2) * 1/2) = 5e-9 V/rHz (this is already bad; the signal coming out of the mixer needs to be amplified by x10 before going out to the whitening board).
In any case, its clear that we need something like 60 dB of gain for the PD noise to match the ADC noise. This is why increasing the whitening gain improves the error signal's SNR, reduces the hash driving the optics, and improves the locking. We should run with 45 dB gain and the switch on whitening after the lock.
Even better would be to modify the LT1128 input stage of the card to have the single stage of fixed whitening as we did for iLIGO. Then we can have triple whitening in lock.
Our first move has to be fixing the whitening switching for REFL55. That's the configuration we need to start and then move onto REFL165 to get to FPPRMI.
Very good - now you need to just put the cal factor into the filter banks so that the PERROR and YERROR signals are in microradians all the time.
EDIT JCD: In progress.
I changed the default shell on our control room iMac to bash. Since we're really, really using bash as the shell for LIGO, we might as well get used to it. As we do this for the workstations, some things will fail, but we can adopt Jamie's private .bashrc to get started and then fix it up later.
We could not find a power supply slot for the amplifiers on the LSC rack. We had to put a temporary power supply in contradiction to our 'no temporary power supply' policy.
After 1 month, its hard to imagine that this could not have been fixed by putting in a proper fuse and fuse block. I will remove this tomorrow if I still find it this way in the bottom of the rack.
There are also 2 Sorensen switching supplies in the bottom of the LSC rack (with all of our sensitive demod boards). These should also be moved over to the old 'digital' LSC rack tomorrow for the post meeting lab cleanup.
Use fuse blocks with fuses with appropriate ampacity.
For the 110 MHz demod boards, we would ideally have a plugin bandpass filter. If you have some specs in mind, you can email mini-circuits or pulsar microwave about making a custom part; its not too expensive usually.
For the meantime, you should remove the onboard one and replace with a combination of low/high pass filters from Mini-Circuits. If you put a SLP-150 and a SHP-100 in series, the insertion loss should be less than 1 dB.
I think the ERA amps are OK for now, but they die with time, so they just need to be tested and replaced if necessary.
There are some tips for how to appy nail polish on YouTube from MKNails and MissJenFABULOUS. Their tips on how to prepare the site for a strong bonding strength are probably helpful for our gold/nickel coated tools. For chrome tools we may need to abrade the surface with a stone or fine sandpaper for it to take the layer better. IF the YouTube videos don't do it for you, then I suggest contacting Tom Evans at LLO to find out what kind of nail polish he uses.
1) We still need to drill and install the thumbscrew latches which secure the lids to the table. We cannot use the tables as an acoustic enclosure with loose lids.
2) For the camera issue, the idea is to put the longpass filters on the front of the cameras: then they are only sensitive to light with wavelength > 800 nm.
3) Whenever any interferometer work is happening the light switches must be in the positions which have been marked on them (and which most everyone ignores foolishly). We have never been insensitive to the room lights; the black table enclosures just give us a false sense of security. Room lights impact the interferometer noise.
The MC seemed to be losing lock recently quite a bit. I noticed that the PC Drive RMS signal was red.
This means that the high frequency drive to the Pockels cell was too high by a factor of 2-3 and sometimes saturating and breaking the lock.
I fiddled with the gains on the FSS screen until this value went down. It looks like there is some kind of high Q oscillation; it takes a couple minutes for the PC Drive RMS to settle to its new position after changing the gains.
The attached trend plot show the last 2 hours. The mean is now back to ~1 V and seems OK. We should really examine the FSS or MC error point spectra with the RF analyzer while exploring this gain space.
Listening to the free swinging Y-arm, its clear that the fringe velocity is higher with the MCL path off, than on. I checked that the default gain of -300 was too high and changed it to -100 in the mcup script. With the higher gain value, there was clear gain peaking at just under 60 Hz (where the 60 Hz comb filter starts). We basically want the UGF to be between 20 and 60 Hz so that we can have the Bounce mode RG at 16.25 Hz and also the notch filter at 60 Hz.
Den is measuring and setting the UGF to be ~45 Hz.
With the MCL path on there is a high frequency horn-like noise in the Yarm when it locks. Its reduced a little by reducing the loop gain, but clearly this is just noise introduced by the MCL loop as Den noted before (and also tonight). He is cleaning up the whole MCL MEDM situation so that its useable by us. At the moment I've re-enabled it in the mcup.
My belief is that the frequency noise from the unstabilized MC is making the PRC locking harder. This will be investigated by tuning the shape of the MCL/MCF crossover so that we can turn it on without ruining the arm cavity spectra. Since the PRC length is ~2x smaller than the MC, we would expect it to be less sensitive to the MC frequency noise. But, since there is some common mode rejection in there, this may not be true. We'll only know by measuring PRC control signal with MCL on/off.
How is the cavity g-factor accounted for in this calculation?
Maybe its equivalent, but I would have assumed that the input beam is fixed and then calculate the cavity axis rotation and translation. If its small, then the modal expansion is OK. Otherwise, the overlap integral can be used.
For the ETM motion, its a purely translation effect, whereas its tilt for the ITM. For the PRM, it is also a mostly translation effect as calculated at the PRC waist position (ITM face).
For the PRM, it is also a mostly translation effect as calculated at the PRC waist position (ITM face).
I made another estimation assuming that PRCL RIN is caused by translation of the cavity axis:
In order to get translation to RIN, we need to know the offset of the input beam from the cavity axis...
This should be possible to calibrate by putting a pitch and yaw excitation lines into the PRM and measuring the RIN.
See secret document from Koji.
Why use the PSL beam as a reference? Don't we want to keep the MC pointing in a good direction through the Faraday instead???
controls@rosalba:/users/rana/docs 0$ svn resolve --accept working nancy
Resolved conflicted state of 'nancy'
Due to the recent addition of cal factors in the OL error points, the OLPIT_GAIN and OLYAW_GAIN have been reduce to tiny numbers (e.g. 0.002).
Since our MEDM only shows 3 digits past the decimal point by default, it makes more sense to have the gains around 1.
So I reduced the gains in all of the FM1 filters from 1000 to 1 and multiplied the GAIN values by 1000 (using ezcastep) to compensate.
All of the active optics seem to be behaving as before. Haven't tested ETMs or SRM yet.
Koji and I went into "Update Manager" on several of the Ubuntu workstations and unselected the "check for updates" button. This is to prevent the machines from asking to be upgraded so frequently - I am concerned that someone might be tempted to upgrade the workstations to Ubuntu 12.
We didn't catch them all, so please take a moment to check that this is the case on all the laptops you are using and make it so. We can then apply the updates in a controlled manner once every few months.
controls@rosalba:/opt/rtcds/caltech/c1/medm/c1ioo/master/master/master 0$ ls
C1IOO_LKIN_OUT_MTRX.adl C1IOO_MC_ASS_LOCKIN5.adl C1IOO_WFS1_I.adl C1IOO_WFS_LKIN.adl
C1IOO_LOCKMC.adl C1IOO_MC_ASS_LOCKIN6.adl C1IOO_WFS1_Q.adl C1IOO_WFS_MASTER.adl
C1IOO_LOCKMC_BAK.adl C1IOO_MC_ASS_PIT_LOCKIN.adl C1IOO_WFS1_SETTINGS.adl C1IOO_WFS_MASTER.adl~
C1IOO_MC_ALIGN.adl C1IOO_MC_ASS_YAW_LOCKIN.adl C1IOO_WFS1_SETTINGS.adl.old C1IOO_WFS_MASTER_BAK.adl
C1IOO_MC_ALIGN.adl~ C1IOO_MC_LOCKINS.adl C1IOO_WFS2_I.adl C1IOO_WFS_OUTMATRIX.adl
C1IOO_MC_ALIGN_BAK.adl C1IOO_MC_SERVO.adl C1IOO_WFS2_Q.adl C1IOO_WFS_QPD.adl
C1IOO_MC_ASS.adl C1IOO_MC_TRANS_QPD.adl C1IOO_WFS2_SETTINGS.adl C1IOO_WFS_QPD.adl.old
C1IOO_MC_ASS_LOCKIN1.adl C1IOO_Mech_Shutters.adl C1IOO_WFS2_SETTINGS.adl.old fmX
C1IOO_MC_ASS_LOCKIN2.adl C1IOO_MODECLEANER.adl C1IOO_WFS_HEADS.adl junk
C1IOO_MC_ASS_LOCKIN3.adl C1IOO_QPDS.adl C1IOO_WFS_HEADS.adl.old master
C1IOO_MC_ASS_LOCKIN4.adl C1IOO_QPDS_BAK.adl C1IOO_WFS_INMATRIX.adl svn-commit.tmp~
controls@rosalba:/opt/rtcds/caltech/c1/medm/c1ioo/master/master/master 0$ cd master
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controls@rosalba:/opt/rtcds/caltech/c1/medm/c1ioo/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master 0$ cd master
controls@rosalba:/opt/rtcds/caltech/c1/medm/c1ioo/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master/master 0$ cd master
controls@rosalba:/opt/rtcds/userapps/trunk/isc/c1/medm/c1ioo 0$ cd master
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controls@rosalba:/opt/rtcds/userapps/trunk/isc/c1/medm/c1ioo/master/master/master/master 0$ helppp
helppp: command not found
controls@rosalba:/opt/rtcds/userapps/trunk/isc/c1/medm/c1ioo/master/master/master/master 127$ help me
bash: help: no help topics match `me'. Try `help help' or `man -k me' or `info me'.
All of these changes were committed to the SVN.
Pfft. Why 500 usec delay? We should be using the known parameters for the hardware and software AA/AI.