None of the links here seem to work. I forgot what the story is with our special apache redirect
in addition to Koji's words I feel like we should also thank those who made small but positive contributions. Its hard not to notice that this locking only happened after the new StripTool PEM colors were implemented...
From the times series plot I guess that the fuzz of the in-loop DARM is 1 pm RMS (based on memory). This means that the ALS was holding the DARM at 10 pm from the RF resonances.
There is no significant shift in the DRMI error signals, so new weird CARM effect. Would be interesting to see what the 1f signals do in the last 60 seconds before RF lock.
For documentation, perhaps Gautam can post the loop gain measurements of the 5 loops on top of the Bode plots of the loop models.
The OSEMs cannot be used for coil balancing above ~10 Hz. The main coupling path from OSEM drive to sensor is not through the mirror motion, but instead direct electrical coupling of the drive wires to the sensing wires.
I put this in the elog every ~1-2 years since people keep trying it, but it keeps coming back like a zombie.
Better to use the MC angular sensors for L2A decoupling. Not perfect, but better than OSEMs. For the TMs we can use the OLs.
How many volts does it take to pitch the ETM by 5 urad?
Although this noise is bad, we have always had these kind of humps around the bounce mode. Our interpretation in the past was that this was due to poor alignment of the OSEM in the frame, leading to a large vertical to horizontal coupling. Once you implement the BLRMS for the SUS channels, we'll be able to trend the noise over long periods of time.
controls@nodus|~ > df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/nodus2--vg-root 355G 69G 269G 21% /
udev 5.9G 4.0K 5.9G 1% /dev
tmpfs 1.2G 308K 1.2G 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 5.9G 0 5.9G 0% /run/shm
/dev/sda1 236M 210M 14M 94% /boot
chiara:/home/cds 2.0T 1.5T 459G 77% /cvs/cds
fb:/frames 13T 11T 1.6T 88% /frames
OMG. Please try to use larger fonts and PDF so that we can read the plots.
Based on elog 1403, I calibrated the oplevs for ITMY/ETMY.
I'm not sure that these calibration measurements are reliable. I would feel better if Steve can confirm them using our low accuracy method of moving the QPD by 1 mm and doing trigonometry.
On the demod board there is a 10 dB attenuator (AT1), which lowers the level to -10 dBm before the ERA-5. Then it should be 10 dBm before going to the rest of the parts. But I guess the ERA-5 chips which come later on in the circuit could be decaying like the ones in the PMC LO board.
Later at home, I thought this nominal LO level of 0dBm could have been wrong.
Hmmm. Very non-standard demod. From the photo, looks like someone did some surgery with the attenuators (AT1, AT2, AT3) in the LO path. (might be me from a long time ago).
-8 dBm input to a circuit is a not a low noise situation. It would be best to remove the amplifiers in the I&Q paths and just have a single amplifier in the main path. Ideally we want the LO to never go below -3 dBm and certainly not below 0 dBm while outside of the board.
I doubt that all of the LSC demods were modified in this way - this one ought to get some sharpie or stickers to show its difference.
Perhaps we can replace T1 with a mini-circuits hybrid 0-90 deg splitter and then remove the trim caps. (JSPQ-80, JYPQ-30, SCPQ-50)
I need some more hints to understand the improvement, although its generally good to re-build it considering the sad state of the assembly/installation that you found.
I see that the current design brings the 11 MHz signal to -2 dBm before intering the first ZHL-2+, but since that has a NF of 9 dB, that seems to only degrade the phase noise to -2 - (-174 +9) = -163 dBc. That seems OK since we only need -160 dBc from this system. Probably the AM noise is worse than this already (we should remember to hook up a simple AM stabilizer in 2016, as well as the ISS).
What else are the main features of this improvement? I can reward a good summary with some Wagonga.
Let Loren help you make your Oplev data readable to humans.
NDS2 and the usual ports so that we can use optimus as a comsol server.
I don't think there are any other ports we need open, but I could be wrong. Let me know if I broke something you need!
Here's how we should diagnose the EX laser:
This LHO log indicates that EPICS slow down could be due to NFS activity. Could we make some trend of NFS activity on Chiara and then see if it correlates with EPICS flatlines?
I wonder if our EPICS issues frequency is correlated to the Chiara install.
The EOM upstream of the PMC is used as the phase corrector for the FSS/IMC servo. It is also used to apply the 35.5 MHz PDH RF sidebands for the PMC locking. There is a Pomona box which is used to merge the two signals onto a single cable for the EOM.
Does this circuit make sense to anyone?
Fire alarm went off several minutes ago. Talked to security and they said there was no fire. It beeped twice again just now. No one has been working on the IFO today.
The problem here is that the MC displacement noise is leading to large frequency excursions of the PSL beam. Options
In the modern times, people use glue traps to catch rats instead of springs. They are less hazardous to people and don't spread rat fluid on the floor.
Unless this is the limit from the way you guys set up the PLL, it seems like there's no difference between the two lasers that's of any import. So then the locking problem has been something else all along - perhaps its noise in the X-PDF lock somehow? PDH box oscillations?
Just not just pedagogical ! Freq domain MISO coherence based subtraction estimation is much faster than calculating MISO WF. And since each bin is independent of each other, this gives us an estimate of how low the noise can go, whereas the Wiener filter is limited by Kramers-Kronig. We should be able to use this on the L1 DARM channel to do the noise hunting as well as estimating the subtraction efficacy of the pseudo channels that you and Rory come up with.
If you can code up a noise hunter example using DARM + a bunch of aux channels, we could implement it in the summary pages code.
Is the black ref spectrum from this year or from May of 2015 or ?
I wonder if the noise is a bunch of fast spikes or if its a true broadband rumble. Maybe we can tell by looking at the analog DFD or PLL outputs?
The PDA photodetectors are DC coupled, so you cannot use them to go directly into the analyzer. Must use the DC block so that you can reduce the input attenuation on the B channel and then lower the drive amplitude.
Good policy for TF measurements: drive as softly as you can and still measure in a reasonable amount of time, but no softer than that.
I didn't really appreciate this measurement until just now. IF you can save the DTT .xml file with all the traces in it (i.e. NOT just the plots), we should save this data for comparison plotting later. Perhaps Gautam can post the gzipped xml file for you into the log.
The accelerometers don't read any real noise below ~3 Hz, so we can't judge the difference down low, but this seems like a good measurement in the 5 - 100 Hz band.
I don't think there's any evidence that the noise eater is bad. That would change the behavior of the relaxation oscillation which is at 1 MHz ?
Sorry, that was me; taking some photos of the PSL and EX mirrors.
PSL Table doors were open, and the laser shutter was closed.
Doors have been closed, laser has been opened.
Why is the transmission of X green so low? Perhaps you can phase lock the IR and then scan the X frequency, using the X arm as the analyzer. i.e. put a slow ramp into MC2 to pull the PSL frquency and thus the green frequency. You can record a movie of the scan using the framegrabber and record the green transmission peaks to see how big the mode match is exactly (which modes are so big)
Its not a good idea to use green mounts with green lasers. Steve should be able to get another copy of the EY doubler mount made up if we really don't have another one sitting in the Manasa end table box which Koji mentioned.
Found it locked on TEM01 mode.
Sweets in the fridge for non-PhD holders, courtesy of the highest levels of Caltech.
Something seems not right. The Guralp response should be flat in velocity from 0.05-30 Hz. Why is there any feature at 1 Hz? Saturation of some kind?
Bah, we need ruby slippers for all future suspensions. Prism with curved backside and smooth grooves.
No aluminum, no cry.
Earth quake stops need viton tips.
Wirestandoffs are still aluminum.
OK - but give us a circuit diagram and the expected before/after loop plots. Got to make sure we keep the right impedance from PD to mixer. Some of the Thorlabs PDs have a 50 Ohm instead of 0 Ohm source impedance. Maybe you can try it out now since the green arm is ready.
Steve sent 4 of our 1" diameter G&H HR mirrors to Josh Smith at Fullerton for scatter testing. Attached photo is our total stock before sending.
Antonio/Gautam are now developing a more up to date Finesse model of our recycling cavities to see what we can have there before our power recycling gain or cavity geometric stability is compromised. Expect that we will here a progress report on the model on Wednesday.
All seems very fishy. Its not good to put attenuators and filters in nilly-willy.
Seems weird to design a PD lowpass with a corner at the modulation frequency. Recall what our strategy is with the other photodetectors we use for PDH servos: bandpass, not low-pass, and the band has to be wide enough to not effect the phase of the servo.
Indeed. This is why the LSC PDs have a 2f notch in addition to the 1f resonance. In recent versions, we also put a 2f notch in the feedback of the preamp which comes after the diode but before the mixer. The overall 1f to 2f ratio that we get is in the 50-60 dB region. I don't think we have to go that far with this thing; having a double LC already seems like it should be pretty good, or we could have a single LC bandpass with a 2f notch all in one Pomona box.
What about ETMY? and are these really microradians or just some made up cal?
That sounds weird. If the ETMY RoC is 60 m, why would you use 57.6 m in the simulation? According to the phase map web page, it really is 60.2 m.
So, it seems that changing the ETMX for one of the spares will change the contrast defect from ~0.1% to 0.9%. True? Seems like that might be a big deal.
Below 100 Hz, I suppose this means that the X arm is now limited by the quadrature sum of the X and Y arm seismic noise.
Found PMC unlocked for many hours so I relocked it. IMC relocked by itself, but the input switch seems to be flickering to fast. Also the Keep Alive bit is not flashing.
I'd suggest clamping and moving it to the flow bench so you can inspect with a bright light. Then remove the wire and inspect the standoff, but hurry up with getting it in the soak bath so you can start on the cleaning of the other ones.
I wonder if we're really sure that its a mechanical problem with ETMX.
Gautam tells me that the local damping was always ON when looking for the jumps. This means that the coil driver was still hooked up and we can't rule out glitches in the DAC or the coil driver.
The UL OSEM shows the biggest movement (10 microns). The LR shows the second most (6-7 microns). The others are 2x less. So its consistent with a voltage change on UL,
Is this consistent with a slip in one of the wire standoffs? I think no.
Comments on the schematic:
Looks pretty great. However, there's two problems:
1) Some of the MEDM screens don't show the time. You can fix this by editing the screens and copy/paste from screens which have working screens.
2) The snapshot script seems to not grab the full MEDM screen sometimes.
These are not a very big deal, so you can get the microphones working first and we can take care of this afterwards.
Steve, please look into getting some plated magnets (either SmCo or NdFeB is OK) of this size so that we can install cleaner magnets by the next vent.
For the rest of this vent, at least, we need to start using the EQ stops more frequently. Whenever the suspension is being worked on clamp the optic. When you need it to be free back off the stops, but only by a few hundred microns - never more than a millimeter.
Best to take our time and use the stops often. With all the magnets being broken off, its not clear now how many partially cracked glue joints we have on dumbells which didn't completely fall off.
I'd recommend replacing the wire and grinding down the clamp to prevent cutting the wire. Since we have almost never replaced clamps, many of them probably have grooves from the wires and can make unpleasant cuts. Better safe than sorry in this case.
I cleaned up the south Electronics bench today.
The other two, as well as several of the desks are in some chaotic state of degradation. Please clean up your areas and put away projects which do not need to remain staged for several months. Try to eliminate "that's not mine" and "I don't know who's that is" from your vocabulary. Fight back against entropy!