I think the crane repair guy accidentally stepped on the BS support beam.
PRM side is not coming down.
Seems fine now.
PRM was released from the fixuture without any trouble. This was the last magnet gluing until ETMs are delivered.
The below is the up-to-date Jenne stat table.
The clean room is getting too narrow. I am thinking that we should install ITMs to the chamber so that we can accommodate SRM/PRM suspensions.
I'm starting to lock for the night, and I noticed that PRM is very, very pitched. Why? The PRM pitch slider is 5 full integer units higher than the backup (and the backup value is about where I like it, around -0.2).
I am not aware of any scripts that touch the PRM slider values. The PRM ASS (which I haven't used in ages) offloads the biases to the SUS screen fast channels, so even if someone turned that on and then saved the values, it wouldn't leave the PRM so very, very misaligned.
I have restored it, and relocked the PRMI, so all is well, but it's very weird to have found it so misaligned.
The standoff glued. The incandescent lamp set for curing the epoxy.
Jenne and Suresh did the balancing job. The next job was to glue it.
They ran out of the clear epoxy, and tried to use the grey epoxy which we used on the other suspensions for the upgrade.
They found that the solution A with grey color one was dried out and grainy.
We made a test piece of the grey epoxy (mixed with the solution B) in order to see the glue is still usable or not.
After the PMA party, we found that the glue was not stiffening but brittle. We judged that the grey epoxy is no longer useful.
Steve found a pack of Vac Seal in the chemical fridge. We decided to use this one for the gluing of the standoff.
After the gluing, we set an incandescent lamp to make the glue warm.
Finally, we wrapped the suspension tower with Al foils and turned the HEPA fans again.
The PRM got tripped ~5AM this morning. The cause is unclear - the seismometer reports elevated activity ~10 minutes before the ringdown starts (as judged using the OSEMs). But the other optics didn't seem to receive as much of an impulse (I only show the BS sensors here as it sits on the same stack as the PRM). Anyway it certainly wasn't me trying to make life difficult for the morning team.
I was able to restore the damping with reEnableWatchdogs.py. I am now running some suspension tests on the PRM by letting it swing freely so please let that finish. I plan to attempt some locking this evening.
- Upon arrival, MC is locked, and we can see light in MON5 (PRM) (usually dark).
I just saw the PRM watchdog tripped at ~15:20 local (23:20UTC). I restored the PRM but I saw only the side watchdog tripped.
Again at 15:27
17:55 I found the PRM was oscillating while the watchdogs were not tripped. I turned off the OPLEV servos and this made the PRM calmed down. But I didn't turn on the OPLEVs for the past two trips. How were the OPLEVs turned on???
Ah, I'm sorry, I missed the line that Gautam was running the free-swinging test on the PRM.
The two kicks starting from 23:08:50 and from 23:26:31 were spoiled. Did it make the measurement completely waisted?
While I was trying to lock the PRMI this evening, I noticed that I couldn't move the REFL beamspot on the CCD field of view by adjusting the slow bias voltages to the PRM. Other suspensions controlled by c1susaux seem to respond okay so at first glance it isn't a problem with the Acromag. Looking at the OSEM sensor input levels, I noticed that UL is much lower than the others - see Attachment #1, seems to have happened ~100 days ago. I plugged the tester box in to check if the problem is with the electronics or if this is an actual shorting of some pins on the physical OSEM as we had in the past. So PRM watchdog is shutdown for now and there is no control of the optic available as the cables are detached. I will replace the connections later in the evening.
Since I couldn't find anything wrong, I plugged the suspension back in - and voila, the suspect UL PD voltage level came back to a level consistent with the others! See Attachment #2.
Anyway, I had some hours of data with the tester box plugged in - see Attachment #3 for a comparison of the shadow sensor readout with the tester box (all black traces) vs with the suspension plugged in, local damping loops active (coloured traces). The sensing noise re-injection will depend on the specifics of the local damping loop shapes but I suspect it will limit feedforward subtraction possibilities at low frequencies.
However, I continue to have problems aligning the optic using the slow bias sliders (but the fast ones work just fine) - problem seems to be EPICS related. In Attachment #4, I show that even though I change the soft PITCH bias voltage adjust channel for the PRM, the linked channels which control the actual voltages to the coils take several seconds to show any response, and do so asynchronously. I tried restarting the modbus process on c1susaux, but the problem persists. Perhaps it needs a reboot of the computer and/or the acromag chassis? I note that the same problem exists for the BS and PRM suspensions, but not for ITMX or ITMY (didn't check the IMC optics). Perhaps a particular Acromag DAC unit is faulty / has issues with the internal subnet?
Sigh... hard loch
The procedure is that the optic is kicked to excite it, and allowed to ring down for ~1ksec, with damping turned off. The procedure is repeated 15 times for some averaging.
Attachment #1 - sensor spectra from yesterday.
Attachment #2 - peaks using the naive diagonalization matrix from yesterday.
Attachment #3 - Data from ~1 year ago.
The y-axis in all plots is labelled as "cts/rtHz" but these are the DQed channels, which come after a "cts2um" CDS filter - so if that filter is accurate, them the y-axes may be read as um/rtHz.
I wonder if the September 2020 earthquake somehow damaged the PRM suspension, as this experiment would suggest that the problem is not only with the actuation. The data was gathered with the neutral position of the PRM (between kicks) being well aligned for PRMI, and the DC values of all the shadow sensors in this position is close to half-light (~1V, except for side which was more like 4V). Hard to say what exactly is happening since only the PIT DoF has the weird asymmetric peak shape instead of the expected Lorentzian - I would have thought that a damaged wire or broken magnet would affect all 4 DoFs but the F.C. spring experience on ETMY showed that anything is possible.
The PRM violin filter seems very suboptimal - the gain peaking shows up in the MICH OLTF, presumably due to the MICH-->PRM LSC output matrix. I plot the one used for the BS in comparison in Attachment #1, seems much more reasonable. Why does the PRM need so many notches? Is this meant to cover some violin modes of PR2/PR3 as well? Do we really need that? Are the PR2/PR3 violin modes really so close in frequency to that for the 3" SOS? I suppose it could be since the suspension wire is thinner and the mass is lighter, and the two effects nearly cancel, but we don't actuate on PR2/PR3? According to the earlier elog in this thread, this particular filter wasn't deemed offensive and was left on.
Indeed, as shown in Attachment #2, I can realize a much healthier UGF for the MICH loop with just a single frequency notch (black reference trace) rather than using the existing "PRvio1,2" filter (FM2), (live red trace). The PR violins are eating so much phase at ~600 Hz.
We turned off many excessive violin mode bandstop filters in the LSC.
agreed, seems excessive. I always prefer bandstop over notch in case the eigenfrequency wanders, but the bandstop could be made to be just a few Hz wide.
Koji and I have the PRMI locked right now, and we hear a very strong violin mode ringing up, at 628Hz. This is, according to Koji's elog 9634, what we expect the PRM's violin mode to be. However, the current PRM violin mode notch is really more of a bandstop filter, between 622-670Hz. At 628Hz, it has a suppression of about -20dB. If I try to increase the width of this notch by making it 612-670Hz, the PRMI won't hold lock.
We're leaving this as a daytime task for tomorrow, since we're in the middle of taking data to show that Koji's new ASC filter design (slightly tuned from his elog 9769) works well.
Edit: I have moved the PRM violin notch frequency over to 612-660 Hz, and after letting it sit for a while (while locked on PRMI), the violin mode has settled down. Interestingly, if I compare the spectrum with and without the 1st order violin mode notch, it looks like the 2nd order mode changes from 1256Hz to 1303Hz. I don't know what is going on here, but we already have notches for both of those frequencies.
Earlier this afternoon, while locking PRMI, I saw a big peak at 1883.48 Hz. This comes closest to the PRM's 627.75 Hz *3, so I infer that it is the 3rd order harmonic of the PRM violin mode.
While putting this in, I noticed that my addition of ETM filters the other day (elog 10746) had gotten deleted. Koji pointed out that Foton can do this - it allows you to create and save filters that are higher than 20th order, but secretly it deletes them. I went into the filter archive and recovered the old ETM filters, and split things up. I have now totally reorganized the filters, and I have made every single optic (ETMs, ITMs, PRM, SRM, BS, MC2) all the same.
FM1 is BS 1st and 2nd harmonics, and FM6 directly below that is a generic 3rd order notch that is wide enough that it encompases 3*BS.
FM2 is the PRM 1st and 2nd order, and FM7 below it is the PRM 3rd order.
FM3 is the SRM 1st order, FM4 is the ETMs' 1st order, and FM5 is the MC2 1st and 2nd order filters.
All of these filters are triggered on if any degree of freedom is triggered. They all have a ramp time of 3 sec. We may want to consider having separate trigger options for each optic, so that we're not including the PRM notch on the ETMs, for example, and vice versa.
When all of these filters are on, according to Foton we lose 5.6 degrees of phase at 100 Hz.
[Koji, Steve, Jamie, Yuta]
So, PRM was NOT flipped......
We opened the BS chamber and quickly checked the arrow on the PRM pointing HR. It turned out to be correct, the arrow was pointing towards the arm cavity. We opened the ITMX chamber, too, to check PR2 later.
BS chamber and ITMX chamber is now closed with the light door.
But it was a one step forward anyway, because we could prove PRM was innocent.
What to do next:
We know that the mode-matching of the incident beam and both arms are pretty good. So, dirty modes come from PRC.
We will check beam clipping, mirrors, suspensions in PRC.
I expect the chambers to be closed on Monday(July 2) afternoon and start pumping on Tuesday(July 3) morning.
We noticed that the PRM watchdog was tripping frequently. This is a period of enhanced seismic activity. The reason PRM in particular trips often is because the SIDE OSEM has 5x increased transimpedance. We implemented a workaround by modifying the watchdog tripping condition to scale the SD channel RMS by a factor of 0.2 (relative to the UL and LL channels). We restarted the modbus process on c1susaux and tested that the new logic works. Here is the relevant snippet of code:
# PRM Side is special, see elog 14745
field(DESC,"Tests whether RMS too high")
field(INPA,"C1:SUS-PRM_ULPD_VAR NPP NMS")
field(INPB,"C1:SUS-PRM_PD_MAX_VAR NPP NMS")
field(INPC,"C1:SUS-PRM_LLPD_VAR NPP NMS")
field(INPD,"C1:SUS-PRM_SDPD_VAR NPP NMS")
The db file has a note about this as well so that future debuggers aren't mystified by a factor of 0.2.
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.
PRM watchdog was tripped around 7:15am PT today morning. I restored it.
See Feb 2012 PRM yaw transferfunctions, also check Valera's modified side sensor may effect yaw motion
Koji spent some time earlier this evening exploring where the excess RIN that we see in the PRC is coming from.
He did this by locking the PRMI (MICH on AS55Q, PRCL on REFL33I, Pnorm for MICH = sqrt(POP110) with 0.1, Pnorm for PRCL = sqrt(POP110) with 10, MICH gain = -30, PRCL gain = 8), and then exciting each relevant optic, one at a time, in yaw. The excitation was always using the ASCYAW excitation point on each of the optics (BS, PRM, ITMX, ITMY), with a frequency of 4.56 Hz, and an amplitude of 30 counts.
He also took reference traces with no optics excited.
Here, I plot (for each excited optic separately) the reference traces and traces during excitation for POP110_I_ERR, POPDC, and the OPLEV_YERROR for the optic that is being excited.
What we are looking for (only in yaw, since we see on the cameras that the dominant motion is in yaw) is an increase in POPDC and POP110 at the same frequency as an optic's excitation.
We see that neither ITM is contributing a noticeable amount to either POPDC or POP110. BS is contributing a little bit, but PRM is clearly contributing. No this entry should be read. (KA)
A week or two ago, I calculated in elog 8489 that the angular motion that we see does not explain the RIN that we're seeing, unless our cavity is much more unstable than Jamie calculated in elog 8316.
I think that I need to install one of the T240's on the new granite slab, and see what kind of coherence we have between seismic and PRM yaw motion, and if FF can get rid of it.
BS is contributing a little bit, but PRM is clearly contributing.
While the peak in the PRM OPLEV was more than 10 times higher than the spectrum level without the excitation,
we only saw small peaks in the RIN spectra. This suggests that the PRM angular motion did not contribute to the RIN spectra.
You should divide the POP110I and POPDC spectra by 400 and 450, which was the DC values of these channels, in order to convert them into RIN (1/rtHz)
The OPLEV spectra is calibrated to be urad/rtHz (is this true?) so you can obtain the conversion factor from OPLEV to RIN (1/urad)
by matching the peaks. This way you make a angular noise projection.
Yes we should do that. BTW what should be pushed?
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.
PRM and ITMY were found with their watchdogs shutdown this afternoon (cause unknown). I re-engaged them.
I fitzed with the PRM and SRM briefly, and I now believe that they're both ready to go into the chambers.
For each optic, I used the microscope on a micrometer to check that the scribe lines on each side of the optic were at the same height. Basic procedure was to center the microscope on one scribe line, move the microscope to the other side, to see how far the line was from center, and try to (very gently!!) rotate the optic in the wire about the z-axis about half the distance that the one scribe line needed to be. Rinse and repeat several times until satisfied.
I then checked that our HeNe oplev was still at 5.5" beam height, and that the beam traveled straight across the table. I put the SRM in the oplev, unclamped the EQ stops, and waited for it to settle. The HEPA filters were turned off, to minimize the breeze. While the SRM settled, I worked on the height/rotation for the PRM on the other table.
After checking the SRM balance, I clamped it and moved it, and checked the PRM balance, then turned off the HeNe and rewrapped everything in foil, and turned on the HEPAs.
Both the SRM and the PRM seem a little off in Pitch. The beam returning to the QPD (placed just next to the laser) was always ~1cm above the center of the QPD. The beam travel distance was ~3m (vaguely) from laser to optic to QPD. This effect may be because the optics were originally balanced with OSEMs in place, and I didn't have any OSEMs today. Koji and I found several months ago that the OSEMs have some DC affect on the optics.
Anyhow, since our optics are so small, I think the OSEMs and coils can handle this small DC offset in pitch, so I think we're ready to rock-n-roll with putting them in the chambers.
Still on the to-do list......Tip Tilts!
The photo shows the oplev beam position on (kind of) the QPD, for the SRM. The PRM was basically the same.
I don't know why (I'm just leaving the lab right now....) but BS, PRM, SRM all have no light on their oplev PDs. I have turned off the oplev servos for now, and will get back to them tomorrow, before redoing the BS table oplev layout.
Can't we somehow hook up this camera to the MUX with the movie mode?
I think both the MUX and the sensoray are compatible with the color video signal.
Only the old CRT is B/W.
Watek 902H ccd with Tamron M118FM50 lens is hooked up to MUX Please be careful! In this set up the lens is close to the view port glass window!
Can't we somehow hook up this camera to the MUX with the movie mode?
I think both the MUX and the sensoray are compatible with the color video signal.
Only the old CRT is B/W.
Watek ccd with Tamron lens is hooked up to MUX
This set up close to the viewport glass! Please be careful!
Video captures when power recycling cavity is locked (videos 1 & 2) and flashing (video 3). Arms stayed misaligned.
1. CH1 and CH2 are loooking at PRM front and back faces. CH3 and CH4 are looking at POP and REFL
2. CH1 and CH2 are loooking at PRM front and back faces. CH3 and CH4 are looking at the ITMs
3. CH1 and CH2 are loooking at PRM front and back faces. CH3 and CH4 are looking at POP and REFL
I'm getting ready change the Newport Ultima U100-AC to SS-Polaris-K1 LOW DRIFT MIRROR MOUNTS
Note: there is only one lens in the PRM lunching path ( only realized later ) , so the spots are large ~ 3 mm at PRM qpd and ~4.5 mm at BS qpd
The spots are well centered.
Atm3, the spots were well centered yesterday ( the PRM is misaligned in pitch and retsore does not work today )
I re-adjusted coil gains and f2a filters for PRM and BS.
I'm not sure what happened to PRM since I balanced on Feb 16(elog #8093).
Let's see if it helps PRMI locking or not.
========== PRM ==========
- Original DC coil gains
- New DC coil gains
multiplier factors are :
UL = 0.928167
UR = 1.061448
LR = 0.941659
LL = 1.068726
Set C1:SUS-PRM_ULCOIL_GAIN to 0.974482231437
Set C1:SUS-PRM_URCOIL_GAIN to -1.04382410014
Set C1:SUS-PRM_LRCOIL_GAIN to 0.898628670041
Set C1:SUS-PRM_LLCOIL_GAIN to -1.03811466772
- New f2p filters
- measured coupling coefficients are :
P2P(POS=>PIT) = 0.023968
P2Y(POS=>YAW) = 0.007075
========== BS ==========
- Original DC coil gains
- New DC coil gains
multiplier factors are :
UL = 1.017855
UR = 1.023207
LR = 0.956184
LL = 1.002755
Set C1:SUS-BS_ULCOIL_GAIN to 1.0562177496
Set C1:SUS-BS_URCOIL_GAIN to -1.03985422464
Set C1:SUS-BS_LRCOIL_GAIN to 0.923750146975
Set C1:SUS-BS_LLCOIL_GAIN to -0.981880297098
- New f2p filters
- measured coupling coefficients are :
P2P(POS=>PIT) = 0.038251
P2Y(POS=>YAW) = -0.014677
Tonight we made a non-folded cavity between the PRM and PR2 as follows. I put down two dog clamps to constrain the original position of the PR2 mount. I then loosened the dog clamps holding the mount to the table and nudged the mount until we saw a few reasonably well-aligned bounces in the cavity. I then dogged down the mount.
We played with the PRM and TT2 steering until we saw flashes of TEM00. However, the resonance is not clean so we couldn't lock.
Since we changed the PRM alignment, we had to redo the last bit of steering for the PRM oplev into the photodiode. We also put a few ND filters on the POP camera.
Wow! What's happened?
As the video showed good quality of resonances, I stopped by at the 40m on the way back home.
I looked at the error signals and found that they indicate high finesse and clear resonance of the sidebands.
The lock was immediate once the gain is set to be -0.004 (previous 0.05ish). This implies the optical gain is ~10 times larger than the previous configration.
The alignment was not easy as POPDC was saturated at ~27000. I leave this as a daytime job.
As I misaligned the PRM, I could see that the lock hopped into the next higher order. i.e .from TEM00 to TEM01, from TEM01 to TEM02, etc
This means that the modes are closely located each other, but sufficiently separated to sustain each mode.
I definitely certify that cavity scans will give us meaningful information about the cavity.
I replaced the BS1 between the POPDC PD and the camera with a 98 reflector, and moved the 50 up before the BS to dump half the light. Still saturating POPDC, but hopefully the ratio between POPDC and the camera should be better. We just need to dump more of the power before we get there. I'll come back to this after C&D if no one else has already gotten to it.
I don't know why I didn't pay more attention last night, but things look way WAY better. The beams are much cleaner and the power level is much much higher.
After Jamie did all the work this morning on the POP table, I was able to get the cavity to lock. It's not very stable until I engage the boost filters in the PRCL loop. After locking, I tuned up the alignment a bit more. Now we're taking mode scan data. Look for results hopefully shortly after Journal Club!
[Jamie, Koji, Jenne]
We are looking at the mode scan data, and have some preliminary results! We have data from when the cavity was aligned, when it was slightly misaligned in pitch, and slightly misaligned in yaw.
Inverting the equation for transverse mode spacing, we infer (for pitch misalignment) a cavity g-factor of 0.99, and from there (assuming the G&H mirror is flat and so has a g-factor of 1), we infer a PRM radius of curvature of 168 meters which is ~50% longer than we expected.
More results to come over the weekend from Jamie.
During the scanning we were riddled by the fact the PDH error and the transmission peaks do not happen simultaneously.
After a little investigation, it was found that "LP100^2" filter is left on in the POPDC filter.
Moreover, it was also found that the whitening filter switches for the POPDC does not switch the analog counterpart.
These were the culprit why we never saw accidental hitting of the max transmission by the peaks when the cavity was not locked.
I know that the most of the whitening filter in the RF paths were checked before (by Keiko?), but the similar failure still exists in the POX path.
We should check for the whitening filters in the DC path as well and fix everything at once. I can offer assistance on the fixing part.
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.
Kiwamu and Koji
The PRM/SRM were balanced with the standoffs. We glued them to the mirror.
This was the last gluing so far until we get new PRM/ETMs.
[Masayuki, Jenne, Rana]
We have, for the past hour and a few minutes, had PRMI + 2 arms locked. Yup, that's right, we did it! (We never gave control of the arms to the IR LSC system, so it's kind of cheating, but it was still cool.)
A little after midnight, we felt that the Yarm was behaving well enough that we could give PRMI + 2 arms a try. So we did. Probably around 1am-ish, or maybe a little bit before, we had the system locked.
How did we do it?
* Locked arms in IR to help find green beatnotes.
* Misalign ETMs, lock and align PRMI.
* Misalign PRM.
* Restore ETMs, find arm resonances, then step away (I did +3 counts, which is 29 kHz).
* Restore PRM, lock PRMI.
* Brought Xarm back close to resonance using ALS (-3 counts). It seems like this may not actually have gotten us back to perfect resonance, but that actually made bringing in the other arm easier.
* Brought Yarm back close to resonance using ALS (-3 counts).
* Turned on Sensing Matrix notches and oscillators (10,000 counts for MICH, actuating on BS and PRM at 562.01 Hz, 200 counts for PRCL actuating on PRM at 564.01 Hz).
* Stepped arms back and forth to see how things responded.
During this process, particularly during the various arm steps, the PRMI lost lock many times. However, the ALS system never lost lock for either arm, for an hour and a half or so. Good work, ALS team!! The PRMI would reaquire lock (sometimes we'd have to undo whatever arm step we just took, to get farther away from resonance) without any intervention. It seemed that as we came closer to full arm resonance, we were never able to hold PRMI locked. This is what is instigating some of our investigations for tomorrow.
Also, Rana reported to me that he turned the c1tst model back off, and opened the door(s?) to the ETMY rack to allow more air flow sometime before midnight, which seems to have reduced the rate of the CPU going over 61 microseconds, as well as reduced the number of times the ETMY suspension glitches. We definitely need to make some changes so that we're not so close to the edge. This may have been one of the big things that allowed our success tonight.
The transmission PDs at the ends of the arms are saturating around 50 counts (they have gains of 2e-3 so that they are roughly normalized to 1 being the max power in a single arm). We need to commission the end transmission QPDs.
All of the signals looked a little ratty, and we heard lots of noise - Rana suggests that we recommission our CARM servo.
ALS beat info: [Xarm 40.9 MHz, -11.4 dB], [Yarm 50.5 MHz, -17.7 dB]
Things to look at tomorrow:
Data! I should be able to extract sensing matrix information, even though my sensing matrix software isn't totally ready yet. I know what the oscillators were doing, and I can look at the PD error signals. We also save the Offsetter numbers, so I can kind of tell what the PRMI+arms situation was.
Can we tell by looking at the end laser PZT feedback signals whether we're making our arms longer or shorter? So that we can tell if we're putting on DARM or CARM offsets.
Spectrum and time series of REFL 165 (our PRMI LSC locking PD) to see if we're saturating while we bring the arms into resonance. Basically, does anything bad happen, particularly since the PD is not a resonant PD, so there are some 1f signals floating around in addition to the 3f signals. We want to put in a directional coupler after the PD, before the demod board, and send that signal to a spectrum analyzer and a 'scope. Hopefully we can use the power of the internet to not need to sit in the IFO room saving data as we move the arms around. Do we need to put bandpass filters on the PD signal before it goes to the demod board?
Optickle model of 1f vs. 3f signals in the different ports, as the CARM offset is reduced.
Violin notches for the arms - should be put into ALS and LSC models. It looks like the modes are around 631 Hz, but we should check.
Hardware for end low gain transmission QPDs.
Software (schmidt triggering) for end transmission QPDs.
Modifying / preparing a matrix in the ALS system so that we can give CARM and DARM offsets conveniently.
Nice work. Congratulation
Just in case people were confused, although the PRMI + 2 ALS arms were controlled, we weren't able to bring them in to resonance. They were in some unknown off-resonant state.
We can try to calculate the expected recycling gain (ignoring losses in the PRM) following section F.2.1 of my Manifesto:
T_PRM = 5.6%, R_ARMS ~ 98%, G_PRC ~38.
So the full TRX/TRY powers should be G_PRC/T_PRM = 690.
In our stable configuration, we were sitting at TRX/Y powers of ~5-10. Once in awhile we could get a state where the power was saturating the detectors at ~50 and possibly would have gone up to 100, but it was all oscillation at that point. (we've got to find and notch the ETM violin mode frequencies in the ALS feedback servos.
As we move in towards resonance, we have to now consider all of complications of handing off to various error signals and CARM optical spring compensation and RF saturation that have been discussed in Rob's thesis and Lisa's lock acquisition modeling.
> all of complications of handing off
- ALS error signals transfered to the LSC input matrix.
- Handing off from the ALS to the 1/sqrt(TRX)+offset signal
- Handing off to the RF signal
- And, of course, CM servo.
PRCL Open Loop Transfer Function. PRMI locked on REFL 165 I&Q, Xarm held on IR resonance using ALS, ETMY misaligned:
MICH Open Loop Transfer Function. PRMI locked on REFL 165 I&Q, Xarm held on IR resonance using ALS, ETMY misaligned:
Time series data during our PRMI + 2 arm attempt:
its time to get the CM servo hardware turned back on. We're going to want to switch it on when we're about ~1/50th of the way up the CARM fringe.
A good way to re-commission it is to lock it to the single arm, using a Pomona box filter to move the arm pole down to the coupled cavity pole frequency.
Koji reminded me that we should also save the data from the PRMI+Xarm, just in case we want to look at it later.
Here is the time series, in which you can see us finding the Xarm IR resonance, moving the arm off resonance, locking PRMI, and bringing the arm back into resonance. At the very end, the arm is still held on resonance, but I had disabled the LSC locking, so we see very large flashes at TRX (of order 40, rather than 1).
The data is in the same folder as the 2arm data: /users/jenne/PRCL/PRMI_Xarm_ALS_16Oct2013/
The text files have been differentiated, so that the 2arm data has "_2arms" at the end of the filename, while the Xarm data had "_Xarm" appended to the filename. Since we left the cavities locked for many minutes (during which transfer functions were taken), the data set for the PRMI+Xarm is very long.
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.
X arm stabilized using ALS while PRMI stayed locked
[Rana, Lisa, Jenne, Manasa]
Time series : ALS enabled at t = 0 and disabled at t = 95s
What we did:
1. Jenne will elog about ASC (POP QPD) updates.
2. Found the beat note between Xarm green and PSL green.
3. Stabilized arm fluctuation by enabling ALS servo.
4. Scanned the arm for carrier resonance by ramping on the offset and set the offset such that we had IR resonating (TRX fluctuated between 0.1 and 0.8 counts).
5. Disabled the ALS servo and locked PRMI using AS55 for MICH and REFL33 for PRCL.
6. Enabled ALS.
Enabling ALS to detune the arm out of resonance kept PRMI locked (currently for a span of few tens of seconds). However we could not see PRMI locked as stably compared to when the arms are misaligned. Everytime the offset was set IR to resonate, the PRMI was kicked out of lock.
Also there is some leakage at the arm transmission when PRMI was locked. The leakage was visible at ETMX transmission as flashes in different higher order modes indicating the not-so sufficient ALS stability. The leakage sets an offset at TRX measuring 0.01-0.05 counts.
To do list:
The ALS_OFFSETTER1 has to be calibrated in FSR. We were giving random offsets to do the offset scan.
Installed a filter before ETMXT camera to remove the refl green. (Note to myself: The filter needs to go on a better mount/adapter).