EOM was aligned to minimize the 11 and 55 MHz peaks in the RAMmon PD the other day (elog 6089), and was left with just the temperature sensor attached, no heater, no foam box.
Here is a 4 day trend:
I don't have a whole lot to say about this, other than there's a lot of stuff going on. The craziness at the end is me realigning the PMC and MC since, as you can see, MC trans was way down. The foam box was put on earlier today (elog 6104), so we'll see how that changes things over night.
Now we've got another day of data, with the foam box on for the last 24hrs.
First plot is a 5 day trend so you can see that the RAM has gotten a little bit smaller, as has the temperature drift, but not by a whole lot.
Second plot is the last 19 hours (so excluding much of the time while I was realigning beams on the PSL table yesterday), to zoom in on just the time when the foam box was installed.
After lunch Zach and I are going to engage the heater to temperature stabilize the system, to see how that affects things.
In other news, the MC looks like it was fine for a good long time, and ~3 hours ago it went bad. The mode that's flashing is really bad in both pitch and yaw. I don't know what happened, but something is not so awesome. Edit: Steve said that he opened the PSL table at some point this morning to look around but not touch, and also it's Janitor Day, and Kevin comes in around 8ish. That doesn't mean I know the actual cause, but those are the only things that happened in the IFO room this morning that anyone is aware of.
The Rich demod box wants 10dBm for the local oscillator inputs, so I measured the values that we have coming out of the distribution box. I'm using the "Spare 55MHz" and the "POP11" outputs, both of which had terminators so were not in use.
The 55MHz had ~600mV peak, so between 5 and 6 dBm.
The 11MHz had ~800mV peak, so about 8 dBm.
This is not enough dBm for either. Going in search of RF amplifiers now...
Actually, the LO inputs to the IQ boards have AP1053 (Cougar) amps on them. These are 10 dB amps and so putting 10 dBm in puts us on the very maximum of the LO range at 20 dBm.
I think the distribution box levels are fine.
I'm not sure I agree with your conversions, BUT:
The IQ boards use a PE4140, fancy MOSFET array as the mixer, and according to Peregrine (manufacturer), they can be operated with 0-20 dBm LO drive. I'm not recommending we drive them at 0 dBm, but perhaps the numbers you mentioned are OK.
Yeah, I looked and saw that it's a semiconductor mixer, so it doesn't have to be as perfect.
Everything is plugged in now to the new demod board. More details soonly...
The I & Q outs are plugged into whitening filter #3, channels 5-8. 11MHz I = chan 5, 11MHz Q = chan 6, 55MHz I = chan 7, 55MHz Q = chan 8. These channels are probably already recorded, but I haven't checked yet. Hopefully I'll have time tonight after I pack for my trip. But Zach, can you look into it tomorrow just to check?? Backup plan is to just go back to using the AS11 and POP55 boards and channels if the new board isn't doing what it's supposed to.
I disconnected the 3rd and 4th channels of the demod box since they were drawing unnecessary current, and making the box hot. Now the box is just warmish.
Is there a reason the framebuilder status light is red for all the front ends?
Also, I reenabled PRM watchdog.
I realigned the incident beam to PMC at 23:30. The transmitted light went up from 0.78 to 0.83.
Do we have PSL pos and ang QPD trends? We should start watching them, because the PMC drifted back down to 0.76 transmission, ~3.5 days after Kiwamu realigned it (his elog is from last Thurs). Not so awesome.
I walked through the control room just now and found both PMC and MC unlocked. They're both locked now, but with PMC transmission 0.76, MC transmission ~24,500.
Bob, Callum and Daphen noted that our keeping a JDSU HeNe (max power <4mW) is against somebody's SOP. So I cleared everything that relates to 40m SOS suspending to the bottom shelf of the 2nd cabinet in the cleanroom (the back set of cabinets nearest the flow benches). The door has a nifty label. Things that are in there include:
QPD and micrometer mount
microscope and micrometer mount
Al beam block
Magnet gluing fixture
dumbbell gluing fixture
The electronics that we use (HeNe's power supply, 'scope, QPD readout) are still on the roll-y thing under the flow bench.
The mode cleaner is super unhappy. It's rocking around at ~1Hz.
I turned off the WFS and turned them back on after the MC was locked, and it seems a little happier now. At least it's not falling out of lock ~1/minute.
Sitting down to start cavity measurements, I found both ITMs tripped. It must have happened a while ago (I didn't bother to check dataviewer trends) because both had rms levels of <5 counts, so they've had a while to sit and quiet down.
The Yarm green laser really wanted to lock on a 01/10 mode, so Kiwamu suggested I go inside and realign the green beam to the arm. I did so, and now it's much happier locked on 00 (the Yarm is resonating both green and IR right now).
The mode cleaner is a little misaligned in pitch, and is very misaligned in yaw. The lowest order mode that is flashing is TEM11.
I had a look-see at the SUS sensors, to see if there were any big jumps. There were moderately sized jumps on all 3 mode cleaner optics.
The MC's lockloss was at ~8:22am this morning, and went along with a giganto kick to the optics. Steve tells me that Den might have been kicking up optics while doing computer things this morning, before Steve reminded him to shut off the watchdogs. However, Steve was also taking phots/measuring things near MC Refl, so maybe he's not totally absolved of blame. But this really looks like the optics settled to different places after big kicks.
I'm going to try to align the MC mirrors to get back to the sensor numbers from early this morning before chaos began.
Reminder / Moral: Everything cannot be considered to be "working fine" if the MC isn't locking. See if you can figure out why, and especially if it's something that you screwed up, either fix it, or better yet, ask for help and learn how to fix what you broke.
We moved the MC approximately back to where the sensors for each optic used to be (mostly touching MC2, but a little bit of MC1 to help the refl get back to its max value). MC is now locked, and with the help of the WFS it's back to nominal. I forgot to disable the WFS, so I think we aren't perfectly aligned, but we're close enough for the WFS to get us the rest of the way. We're heading over to JClub right now, so we're going to leave it as-is.
Kiwamu and Steve maybe don't know about how to trend seismic noise. If you just take the mean of the time series, you don't prove that the seismic noise got any higher. The STS has a nominally zero DC output, so the long period level shifts that you see tell you just that there was a DC offset.
This is NOT an increase in seismic noise. To see a seismic trend you should plot the trend of the BLRMS channels that we made especially for this purpose.
So, none of our PEM BLRMS channels are recorded as of right now. All we have for long-term record is the StripTool on the wall. The 0.1-0.3Hz and 0.3-1 Hz traces both show these weirdo things, but the 1Hz and up BLRMS don't have any unusual noise.
Seems like a problem to solve on Monday so that we don't end up without trends like this again.
Tragically, this is more tricksy than I would have thought. The channels we need are "cdsEpicsOutput"s in the model. They don't show up in Dataviewer (fast or slow channels) or the regular fast channel .ini file. Jamie and I don't remember where these channels live and how to get them saved to frames. I'm on top of it though.
I did notice however, that the striptool for seismic trends is showing the wrong channels for 3-10 and 10-30 Hz. The other 3 channels are correctly the output after the sqrt is taken, but those two (orange and red on striptool) are before the sqrt, but after the bandpass and low pass. I'll fix that now...
We extracted the fiber that Suresh and Sonali laid over the summer, for the IR beat for the Ygreen laser, and Frank took it back to Bridge to be used in the new fiber distributed reference laser setup.
Power Spectral Density plot using PyNDS, comparing 5 fast data channels for ETMX.
Is there any stuff to install, etc? Y'know, for those of use who don't really know how to use computers and stuff....
Xarm is aligned for both IR and green.
Here is a photo of the beam paths of the PSL beat setup. I want to make sure that the X-green BBPD sees a nice beam from both the PSL and the Xarm, without disturbing the currently working Y setup. I keep getting confused with all the beamsplitters, especially the green PBSes, which operate at ~56deg, not 45deg, so I made a diagram.
Meh. I've searched in steps of 20 counts in C1:GCX-SLOW_SERVO2_OFFSET units (16 bit +\- 10V DAC, and 1GHz/V coeffecient for the Xgreen aux laser means this is ~0.6MHz per 20 count step). I went from -400cts to +800 cts and haven't found the beatnote yet. Meh.
Both PSL green and Xgreen beams are going to the Xgreen BBPD. Both beams are easily visible, so while I didn't actually measure the power, it should be sufficient. The arm is being re-locked in green for each step, but it's not locked in IR, but that doesn't matter for just finding the beatnote.
I've got the output of the BBPD directly connected to the 50 ohm input of the HP8591E spectrum analyzer, with the freq span from 10MHz to 120MHz. The BBPD is supposed to be good up to ~100MHz, so I should catch any beatnote that's there. I have to head out, so I guess I'll continue the search tomorrow.
One of Kiwamu's suggestions was that, since no one is using the Ygreen concurrent with my fiddling, I rotate the waveplate after the PSL doubling oven so that max power goes to the Xgreen path, thus giving myself a bigger signal. I'll try that tomorrow. Today, I didn't ever touch the waveplate.
The actual temperature of the Xend laser is 0.02 C higher than anticipated based on the formula in elog 3759. Both the PSL and the Xend laser are at their nominal diode currents (2.100 A for the PSL, 2.003 A for Xend), so the curves should be used as they are. The PSL temp (when the slow servo offset is ~0) is 31.71 C. Using curve 2 from elog3759, the Xend laser should be 37.78, which I found was +10 counts on the Xgreen slow servo offset.
Right now the Xend laser is at 37.80 C, and the beat is around 30 MHz. This is +80 counts on the Xgreen slow servo. +60 counts gave me ~80 MHz. When (a few minutes ago) the MC unlocked and relocked, it came back to a slightly different place, so the temp of the Xend laser had to go up a few 10's of counts to get the same beat freq. Right now the PSL slow servo offset is 0.076 V.
The HP8591E is set with ResBW=100kHz, Ref Level= -39dBm (so I'm not attenuating my input signal!). The largest peak I see for the beatnote is -66dBm. The nose floor around the peak is -83dBm. Trace (trace button!) A is set to MaxHoldA, and Trace B is set to ClearWriteB, so B is giving me the actual current spectrum, while A is remembering the peak value measured, so it's easier to see if I went past the peak, and just didn't see it on the analyzer.
Also, I went back and realigned the beams earlier, to ensure that there was good overlap both near the BS which combines the PSLgreen and Xgreen beams, and at the PD. The overlap I had been looking at was okay, but not stellar. Now it's way better, which made the peak easier to see. Also, also, the waveplate after the doubling oven on the PSL table is still rotated so that I get max power on the Xgreen side of things, and not much at all on the Ygreen side. I'll need to rebalance the powers, probably after we make sure we are seeing the beatnote with the BeatBox.
Lay a cable from the BBPD to the BeatBox in 1X2, make the BeatBox do its thing.
Use the dichroic locking to do a sweep of the Xarm.
ND filter ND3 (which is at the REFL port to the REFL OSA) is removed. Don't forget to put it back when you restore PRM!!!
I don't know what tripped the PRM watchdog, but it was unhappy. I manually moved the sliders on the IFO align screen away from the positions of the save file before turning on the damping, to make sure that I wouldn't be sending oodles of power to the REFL port, since the ND filter is still removed. So PRM is damped now, but misaligned.
Has default inmat:
Has fancy inmat:
BS, ITMY, SRM (but side is non-fancy), ETMX, ETMY, MC1, MC2, MC3
So it's likely that the MICH problems (giganto 1Hz peak) Keiko and Kiwamu were seeing last night had to do with ITMX having the non-optimized input matrix. I'll try to figure out where the data from the last freeswing test is, and put in a fancy diagonalized matrix.
The Xgreen PD now has a cable going over to the beatbox. Once beatbox characterization is done I can re-find the beat, and we can do some stuff with the beatbox.
Here is a picture of the small black breadboard on which I have put together the PD characterisation setup. It would be great if we can retain this portable set up as it is, since we keep reusing it every couple of weeks. It would be convenient if we can fiber couple the path to the PD under test with a 2m long fiber. Then we will not have to remove the PD from the optical table while testing it.
This is totally sweet Suresh! I don't remember how much more fiber is coiled up under the plate that has the "Jenne Laser" label, but there's a reasonable amount. It's not 2m, but maybe we can just extend the blue snakey thing some?
I'd like to know what we expect for these numbers. I've added to Kiwamu's drawing some more distances, so I can calculate the expected beam size at the IPPOS port.
I'm meditating over the mode matching from the mode cleaner to the ITMs, and I had another thought:
Have we changed the pointing of the MC significantly enough that we are no longer on the center of the MMT mirrors? To be this significant, we would probably also have had to scoot the Faraday a bit too, since it's skinny like a straw. It looks like our measurements of the input beam have been the following:
MC waist, 21 May 2010
After MMT2, 18 June 2010 (a few days before this, we flipped the MMT2 mount to 'perfect' the mode matching up to 99.3%, so I don't think the MMT has moved since then.)
After MMT2, 26 March 2012
There's a big o' ~2 year gap between our measurements, and we've been in and out of the vacuum a few times since then. I'll flip through the elog, but does anyone have any memory of us moving the Faraday after June 2010? When was the last time we made sure that we were at least close to the center of the MMT mirrors?
This is wrong! See following elog for corrected plot (and explanation)
I'm not done meditating on what's going on, but here's what I've got right now:
This is a beam profile, using the distances from the combined Kiwamu / Jenne sketch earlier today.
0 meters along the horizontal axis is meters from the Mode Cleaner waist. (Yes, I was bad and forgot to label it. Get over it.)
The pink and green dots to the left of the plot are the MC fitted waist measurements that we made in May 2010.
The pink and green dots in the ~center of the plot are the fitted waist measurements that Suresh and Keiko took yesterday, of the IPPOS path, so after the MMT.
The black dot is where we would like our non-astigmatic beam to be. This is the calculated waist size of the cavity mode, using the new ~37.76m distance, after we moved the ETMs to their current positions. The black dot indicates 3.036 mm at the ITM (averaged between the BS-ITMX and BS-ITMY distances).
The moral of the story that I'm getting from this plot: something funny is going on.
The distances Kiwamu quoted on the sketch are very close to the ones that I used for designing and checking the MMT in the first place, which were based off of measurements using rulers etc to measure distances. Steve said he looked at photos today, and agreed that Kiwamu's numbers looked reasonable also.
Something that we haven't done lately is measure the position of each optic from every other optic, along the beam path. I propose we come up with a clever way to put a target on top of / next to mirrors, and then a way to hold the laser distance measure-er at an optic, so that we can go thorough systematically and measure the actual path that our beam is seeing. Maybe this is too much work, and not worth it, but it would make me happier. In my head, these 'fixtures' are just small pieces of cleaned aluminum, one that can sit on a mirror mount, and one which we can use to align the laser ruler to approximately the front of an optic. Nothing fancy.
Yup, something funny was going on. Nic's MM code that I used, "a la mode", calls for the focal length of the optics, whereas the code that I wrote and used for ages called for the radius of curvature. f = R/2. Fixing that factor of 2 I get something more like:
This is obviously much better, in that the beam profile goes through (within some error) both of the measured sets of points - the MC waist measured in May 2010, and after the MMT measured yesterday.
So, what does it all mean? That I'm not sure of yet.
As I was a little dissatisfied with the inaccuracy in the distance numbers in Kiwamu's sketch, I went back to the 18 Dec 2010 table layout drawing for more accurate numbers. These are now included in this round of plots.
Also, I include astigmatism due to the incident angles on MMT1 (~3.5 deg) and MMT2 (~1 deg).
First plot, IPPOS path, using the recent (fixed) measurements from Suresh to fix the beam width. Note that the old 2010 measurements of the MC waist are consistent with this measurement.
Second plot, Main IFO path all the way to the ITM (average) position, using the 2010 MC waist measurements to fix the beam width.
Third plot, Main IFO path all the way to the ITM position, but with PRM flipped (negative RoC), using the 2010 MC measurement to fix beam width.
With the PRM correctly oriented (2nd plot), I get beam waists of (x = 2.529 mm, y = 2.646 mm), which corresponds to a mode matching to the arm cavity of (eta = 97.43%, PRM correct).
With the PRM flipped (3rd plot), I get beam waists of (x = 3.176 mm, y = 3.3 mm), which corresponds to a mode matching to the arm cavity of (eta = 99.55%, PRM flipped).
Second plot (this is how the MMT was designed to be, before the ETMs were moved, which made the ideal waist larger):
For both the 2nd and 3rd plot, we can't look at the post-MMT waist measurements, since that distance on the plots is after the PRM, which is a curved optic. So the fact that the post-MMT measurements match the correct-PRM plot better than the flipped-PRM plot can't be taken to be meaningful.
Moral of the story: I'm not sure how to interpret any of this to tell us if the PRM is flipped or not, since the measurements are all of the beam profile before the beam sees the PRM. We'd have to measure the profile after the PRM somehow in order to get that information. We have okay but not great mode matching to the arm if the PRM is correct, but I don't know that we readjusted the MMT after we moved the ETMs. I don't remember recalculating any optimal telescope lengths after the arm length change. If we need better mode matching, I can do that calculation, although given how much space we don't have, it would be hard in practice to move the MMT mirrors by much at all.
Game Plan: Using MC waist measured beam as the starting point of beam propagation, move MMT mirrors around until the beam profile fits with the IPPOS measurements from Monday.
Plot 1: Allow MMT mirrors to move as much as they want to. Note that the Y-beam goes through the IPPOS measured point. (This implies we put the MMT in the wrong place by ~half a meter. Unlikely)
Plot 2: Using MMT locations from plot 1, what does the beam look like at the ITMs?
Plot 3: Allow MMT mirrors to move as much as 2cm. Note that the Y-beam doesn't quite go through IPPOS measured point.
Plot 4: Using MMT locations from plot 3, what does the beam look like at the ITMs?
For all of the above, I was optimizing the propagation of the Y-beam profile. Since the X-beam profile measurement is so different, if I want to optimize to X and let the MMT mirrors move as much as they want, MMT1 ends up inside the MC. Unlikely. So I'm just looking at Y for now, and maybe Suresh or someone needs to rethink the error bars on their measurements or just remeasure.
I fitzed by hand with the numbers for the incident angles on MMT1 and MMT2, and then let the code optimize the position of MMT1 and MMT2.
Here I have set the incident angle for MMT1 = 25deg, and MMT2 = 12deg (should be 3.5deg, 1deg by design). The length of the telescope doesn't want to change by more than 7mm, but the position of the telescope wants to change by 1.3meters. Is it possible that the distances on the Monday IPPOS measurements aren't actually correct?
I installed a NETGEAR Wireless Router (WPN824N) today on the 131 network. The admin password for it as well as the wireless access password are in the usual places.
The SSID is 40EARTH. I have set it to allow WPA as well as WPA2 access, so the speed is only 54 Mbps for now. In a year or so, we can turn off the WPA support and up the speed.
This router was confiscated by the GC guys this morning around ~10am. They barged in and said that someone at the 40m had connected a new router, and we had magically taken down half of the GC network. The cable was plugged in to the wrong port on the back of the router.
Junaid / Christian said that they would "secure" the router, and then reinstall it. Apparently just having a password didn't satisfy them. This was the compromise, versus them just taking the router and never bringing it back.
Suresh noted that I never wrote down the waist positions of the beam propagated through the MMT (based on where we think it is from ruler-based measurements). This uses the MC waist measured beam as the starting point, and just propagates through the MMT, out to the IPPOS port.
q: 2.2488 +23.8777i
waistSize: 0.0028 (at z = 13.2676 meters)
waistZ: 2.2488 (relative to z = 13.2676 meters)
So, to sum up, the vertical beam waist is 2.8438 mm at 11.0188 meters from the MC waist.
q: 5.1953 +24.7342i
waistSize: 0.0029 (at z = 13.2676 meters)
waistZ: 5.1953 (relative to z = 13.2676 meters)
So, to sum up, the horizontal beam waist is 2.8943 mm at 8.0723 meters from the MC waist.
In pictorial form,
I've run static and adaptive filters simultaneously. AA32 filters rotate the phase of the witness signals GUR1X and GUR1Y and now the performance of the static filter is worse. Next time I'll recalculate Wiener filter coefficients taking this into account. But still 2 filters together can deal with a stack better.
This is super awesome! I'm totally excited!!
Suresh reported to Den, who reported to me (although no elogs were made.....) that something was funny with the FB. I went to look at it, and it's actually the RAID array rebuilding itself. I have called in our guru, Jamie, to have a look-see.
We were wondering why the STS-2 signal was funny. When I went to look at it, the X-axis indicator was pointing ~45deg from the x-axis, so that it was pointing between the arms of the IFO. Also, the bubble in the level was totally stuck on one side. We locked the masses, and I put the seismometer back to the correct orientation, and then leveled it. We unlocked the masses and turned the power back on, and hit the auto-zero button a few times. Right now the X-axis signal is fine, but Y and Z are still railed, but it's been like 24 seconds, not 24 hours since we last hit auto zero, so there's still some time to wait.
Also, GUR2 was unplugged on both ends of the cable. We plugged it back in. However, it looks like the *seismometer* labeled #1 is now plugged into *channels* GUR2, and the seismometer labeled #2 is plugged into channels GUR1. Recall that Den has only modified X, Y, Z for GUR1 channels, not any other channels in the breakout box.
I was going to try some locking, but things are a little too noisy.
Just so Kiwamu knows what I did today, in case he comes back....
I ran LSCoffsets, and aligned both X and Y arms and saved their positions, and aligned MICH, and saved the BS position.
I'll play with it more later, when there aren't trucks driving around outside that I can hear / feel in the control room.
After giving up on locking, the MC is getting unlocked every now and again (2 times so far in the last few minutes) from transient seismic stuff.
I don't know why, but they're looking around on the roof, and inside our ceiling above the bathrooms.
...Mostly just recollections at this point.
I re-looked at the mode matching's sensitivity to misplaced optics. Here is the plot that the original MMT code from 2010 spits out:
What this plot is telling us is that we should lose no more than 0.1% of mode matching "goodness" if we messed up the curved optic's positions by up to 2 cm. If we can't place optics to within 2 cm, we might as well go back to optics kindergarten, because that's pretty lame.
UPDATE: Here is a histogram using the new code, which definitely includes the non-unity index of refraction for the transmissive optics and the Faraday. The only optics which are permitted to move are the 2 curved optics, and they are allowed a stdev of 20mm. Again, we shouldn't be doing worse than ~99% mode matching, even if we're 2cm off from the MMT positions that we measured with a ruler. This histogram only has 300 iterations, since it takes quite a while (~0.5sec) to calculate each iteration. Note this is mode overlap using the measured MC waist, propagated through optics, compared to the ideal arm mode. This is completely ignoring the IPPOS measurements so far.
UPDATE 2: Allowed 5 degrees of incident angle motion for both curved optics, which changes the astigmatism of the beam downstream. Still, no big change from ~99% mode matching efficiency. Again, this doesn't include any information from the IPPOS measurements. 3000 iterations this time around, since I didn't need my computer. Curved optics still allowed to move back and forth by 2cm.
More meditations and conclusions to follow... currently running hist code to allow tilt of optics, to account for astigmatism changes also.
Suresh and I are going to do some beam measurements tomorrow with the beamscanner, and then we will do a few measurements with the razor blade technique, to confirm that we're doing things okey dokey.
Bob tells me that the carpenter is going to move the nitrogen bottles to the other side of the outside door, so that the plumbers can install a safety shower / eyewash right outside our door.
Also, the carpenter just mounted a new glass door cabinet from Bob's lab in the IFO room, so we have some new storage space.
Action Items from Last Week:
Action Items this Week and LEAD PERSON:
Assemble and ship 4 TTs from LHO - SURESH
Prepare electronics for TTs (coil drivers) - JAMIE
In-air TT testing to confirm we can control / move TTs before we vent (starting in ~2 weeks) - SURESH
Connect TTs to digital system and controls, lay cables if needed - JAMIE with SURESH
OAF comparison plot, both online and offline, comparing static, adaptive and static+adaptive - DEN
Static-only OAF noise budget (Adaptive noise budget as next step) - DEN
Black glass: big baffle pieces to clean&bake, get small pieces from Bob, put into baskets, make new basket for 1" pieces, get to clean&bake - KOJI
IPPOS beam measurement - SURESH with JENNE
AS beam measurement (if beam is bright enough) - SURESH and JENNE
Mode matching calculations, sensitivity to MC waist measurement errors, PRM position - JENNE
Summary of IFO questions, measurements to take, and game plan - JENNE
Think up diagnostic measurement to determine mode matching to PRC while chambers are open, while we tweak MMT - JAMIE, JENNE, KOJI, SURESH
Power recycling gain
* It should be ~40, but we observe/measure it to be ~7. Even if mode matching of ~50% is assumed, gain is calculated to be ~15
* Would like to measure PR gain independent of mode matching, if possible
Power recycling cavity mode matching
* Reflectivity of PRMI was measured to be ~50%. That's pretty high. What's going on?
* Even if we're mode matched to the arm, are we appropriately mode matched to the PRC?
Is beam from MC clipped in the Faraday?
* We had to use MC axis for input pointing since PZTs aren't totally working.
* Need to measure IPPOS beam for different MC alignments to see if horizontal waist measurement stays constant.
* Not likely, but it can't hurt to confirm for sure.
* Want to know, since it could give us a different plan for MMT moving than if the PRM is correct.
Thick optic non-normal incidence in IPPO - does this exaggerate astigmatism, which would help explain IPPOS measurement?
Is PRC waist same size / position as arm cavity waist, given the current "known" positions of all the optics?
* How is this effected by moving the PRM?
Measurements to take and what information they give us:
IPPOS beam scan, with MC as-is
* Confirm (or not) IPPOS measurements from last week
IPPOS beam scan with different MC alignments
* Will tell us about Faraday clipping, if any
AS beam scan, misaligned PRM, misaligned SRM, misaligned ITMX, single bounce from ITMY
* Can only take this measurement if beam is bright enough, so we'll just have to try
* Will confirm IPPOS measurement, but includes going through the thick PRM, so can compare to calculated intra-PRC mode
REFL beam scan (already done....is the data satisfactory? If so, no need to redo), single bounce off of PRM
* Will tell us about the potential PRM flipping
* Need to compare with calculated mode at REFL port for flipped or non-flipped PRM
Look at POP camera, see 2nd pass through cavity
* Try to match 1st and 2nd pass. If they don't match, we're not well matched to PRC mode
Look at beam directly on ETMY cage, then beam from ETM, bounce off ITM, back to ETM cage
* If the beams are the same size, we're well matched to arm cavity mode
* Use fancy new frame-grabber.
MMT code things to calculate, and what information it gives us:
REFL beam path, for PRM flipping comparison
Thick IPPO non-normal incidence - I'm not sure how to do this yet, since I only know how non-normal incidence changes effective radii of curvature, and this is a flat optic, so *cos(theta) or /cos(theta) won't do anything to an infinite RoC
Compare PRC waist to arm cavity waist, using "known" optic positions
Mode matching sensitivity to MC waist measurements
Mode matching sensitivity to PRM position
Another histogram. This one allows the MMT mirror positions to move, the MMT incident angle for both curved optics to change, and the MC waist size and position to change. The error quoted for the MC waist size measurement from 2010
was +\- 0.01mm, and the MC waist position was +\- 28mm.
This histogram is showing that we're pretty sensitive to the MC waist measurement, which is used to define the beam. We can be up to ~2% off in our ideal mode matching to the arms if we're using the incorrect initial beam for the telescope design.
Mode Cleaner doesn't want to stay locked. Seismic is coming down from an earthquake ~20min ago.
We're in the process of measuring IPPOS, so this is obnoxious.
EDIT: Followed by a 6.2 and a 7.1 at 07:06UTC and 07:15UTC in the same area.
We're following the tried and true tradition of going home when there's an earthquake big enough that the MC won't stay locked.
Several optics have rung up, PRM is the only one which has tripped so far, because the side sensor has the extra gain, but the watchdog threshold is set for the face OSEMs.
There's a beam dump after the HeNe on the BS oplev table, since the IPPOS measurement optics (steering mirrors) are in the way of the oplev beams.
Don't enable the BS or PRM oplevs!!!! We'll post a notice in the elog when the oplevs are back to normal.
Self, remember to disable the oplevs manually if they come on with any restore scripts.
I am locking some things, and have the PRM aligned, and it will stay locked for short periods of time, but as Kiwamu warned me, when the PRM alignment is better, the lock is more "crazy" and unstable. This should go on our list of mysteries.
It's been a while since I think anyone has done it, and several optics were pretty far from centered, so I centered all of the oplevs except for SRM.
I am confident about my arm alignment, MICH and PRC (so BS, ITMX, ITMY, PRM, ETMX and ETMY), but I wasn't sure if I was getting SRC right, so I didn't touch the SRM's oplev.
Suresh removed all of the IPPOS measurement optics, so there was nothing blocking the BS and PRM oplevs.
However, the PRM oplev was ridiculously bad, and I don't know how long it's been that way. Some of the optics shooting the beam into the chamber weren't optimally aligned, so the beam coming out of the chamber was hitting the lowest edge of the optic mount, for the first optic the beam encountered. I adjusted the mirror launching the beam into the chamber by a teeny bit, so that the outcoming beam was ~horizontal and hitting the center of the first steering mirror in pitch. I had to move that steering mirror a little to the right (if you are staring at the HR face of the mirror), to get the beam to come close to the horizontal center of the optic. Then I proceeded to do normal oplev alignment.
Also, I've noticed lately that ITMX is noisier than all the other optics. It's kind of annoying. The sensor RMS values reported for the ITMX watchdogs for UL and LL are rarely below 2, and are often (~70% of the time?) above 3. The SD RMS is a normal 1-ish.
Already not for the first time I notice that GUR2 readjusts its X zero position
As a result the coherence between GUR1X and GUR2X is lost, but between GUR2X and GUR2Y shows up. It seems that these two signals mix at some point.
Can you go back in time before the X-position jumped to plot the x1-x2 and x2-y2 coherences? Just to see what things look like?
None of the 3 MC optics have oplevs, so there shouldn't be any oplev signals. Although MC2 has the trans QPD, which was once (still is??) going through the MC2 oplev signal path.
PRM was noisy last week too. But turning on his oplev shouldn't make him crazy. That's not so good. Try restoring PRM (the ! near the PRM label on the IFO align screen), then checking if his oplev is ~centered. Maybe PRM wasn't in the nominal position at the time you restored from.
None of the 3 MC optics have oplevs, so there shouldn't be any oplev signals. Although MC2 has the trans QPD, which was once (still is??) going through the MC2 oplev signal path.
Duh. Unawake brain. The MCs look fine.