40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  40m Log, Page 189 of 341  Not logged in ELOG logo
ID Date Authorup Type Category Subject
  10802   Tue Dec 16 00:20:06 2014 diegoUpdateOptical LeversBS & PRM OL realignment

[Rana, Diego]

We manually realigned the BS and PRM optical levers on the optical table.

  10805   Tue Dec 16 20:49:25 2014 diegoUpdateComputer Scripts / ProgramsStatus of the new nodus

Quote:

Quote:

 Nodus (solaris) is dead, long live Nodus (ubuntu).

Diego and I are smoothing out the Kinks as they appear, but the ELOG is running smoothly on our new machine. 

SVN is working, but your checkouts may complain because they expect https, and we haven't turned SSL on yet...

 [Diego, EricQ]

SSL, https and backups are now working too!

A backup of nodus's configuration (with some explaining) will be done soon.

 Nodus should be visible again from outside the Caltech Network; I added some basic configuration for postfix and smartmontools; configuration files and instructions for everything are in the svn in the nodus_config folder

  10806   Tue Dec 16 20:51:18 2014 diegoUpdateLSCPRMI loops need help

Quote:

[...]

Diego is going to give us some spectra of the MC error point at various levels of pockel's cell drive.  Is it always the same frequencies that are popping up, or is it random?

 I found out that the Spectrum Analyzer gives bogus data... Since now is locking time, tomorrow I'll go and figure out what is not working

  10817   Fri Dec 19 14:25:48 2014 diegoUpdateComputer Scripts / Programselog restarted

elog was not responding for unknown reasons, since the elogd process on nodus was alive; anyway, I restarted it. 

  10822   Fri Dec 19 19:21:04 2014 diegoUpdateCDSSOS!!! HELP!! EPICS freeze 45min+ so far!

Quote:

[Jenne, Diego]

The EPICS freeze that we had noticed a few weeks ago (and several times since) has happened again, but this time it has not come back on its own.  It has been down for almost an hour so far. 

 So far, we have reset the Martian network's switch that is in the rack by the printer.  We have also power cycled the NAT router.  We have moved the NAT router from the old GC network switch to the new faster switch, and reset the Martian network's switch again after that.

We have reset the network switch that is in 1X6.

We have reset what we think is the DAQ network switch at the very top of 1X7.

So far, nothing is working.  EPICS is still frozen, we can't ping any computers from the control room, and new terminal windows won't give you the prompt (so perhaps we aren't able to mount the nfs, which is required for the bashrc).

We need help please!

[EricQ]

 

EricQ suggested it may be some NFS related issue: if something, maybe some computer in the control room, is asking too much to chiara, then all the other machines accessing chiara will slow down, and this could escalate and lead to the Big Bad Freeze. As a matter of fact, chiara's dmesg pointed out its eth0 interface being brought up constantly, as if something is making it go down repeatedly. Anyhow, after the shutdown of all the computers in the control room, a  reboot of chiara, megatron and the fb was performed.

 

[Diego]

Then I rebooted pianosa, and most of the issues seem gone so far; I had to "mxstream restart" all the frontends from medm and everyone of them but c1scy seems to behave properly. I will now bring the other machines back to life and see what happens next.

  10823   Fri Dec 19 20:32:11 2014 diegoUpdateCDSSOS!!! HELP!! EPICS freeze 45min+ so far!

[Diego, Jenne]

 

Everything seems reasonably back to normal:

Notes:

  • the machines in the control room have been rebooted;
  • the c1iscey frontend now behaves;
  • I saw on nodus, which remained up and running the whole time, a bunch of   nfs: server chiara is not responding, timed out  messages, belonging to the freezing time; it may be that the sync option for the nfs share is too resource demanding, or some other network issue;
  • the FSS was doing strange stuff and the MC couldn't recover the lock; the MCautolocker script wasn't running because of the lock loss of the MC and the lack of communication between the machines; so we did a sudo initctl start MCautolocker on megatron and recovered the MC too.
  10826   Sun Dec 21 18:46:06 2014 diegoUpdateIOOMC Error Spectra

The error spectra I took so far are not that informative, I'm afraid. The first three posted here refer to Wed 17 in the afternoon, where things were quiet, the LSC control was off and the MC was reliably locked. The last two plots refer to Wed night, while Q and I were doing some locking work; in particular, these were taken just after one of the locklosses described in elog 10814. Sadly, they aren't much different from the "quiet" ones.

I can add some considerations though: Q and I saw some weird effects during that night, using a live reading of such spectra, which couldn't be saved though; such effects were quite fast both in appearance and disapperance, therefore difficult to save using the snapshot measurement, which is the only one that can save the data as of now; moreover, these effects were certainly seen during the locklosses, but sometimes also in normal circumstances. What we saw was a broad peak in the range 5e4-1e5 Hz with peak value ~1e-5 V/rtHz, just after the main peak shown in the attached spectra.

Attachment 1: SPAG4395_17-12-2014_170951.pdf
SPAG4395_17-12-2014_170951.pdf
Attachment 2: SPAG4395_17-12-2014_172846.pdf
SPAG4395_17-12-2014_172846.pdf
Attachment 3: SPAG4395_17-12-2014_175147.pdf
SPAG4395_17-12-2014_175147.pdf
Attachment 4: SPAG4395_18-12-2014_003414.pdf
SPAG4395_18-12-2014_003414.pdf
Attachment 5: SPAG4395_18-12-2014_003506.pdf
SPAG4395_18-12-2014_003506.pdf
  10840   Tue Dec 23 18:43:33 2014 diegoUpdateComputer Scripts / ProgramsFSS Slow servo moved to megatron

Quote:

I ssh'd in, and was able to run each script manually successfully. I ran the initctl commands, and they started up fine too. 

We've seen this kind of behavior before, generally after reboots; see ELOGS 10247 and 10572

In the plot it is shown the behaviour of the PSL-FSS_SLOWDC signal during the last week; the blue rectangle marks an approximate estimate of the time when the scripts were moved to megatron. Apart from the bad things that happened on Friday during the big crash, and the work ongoing since yesterday, it seems that something is not working well. The scripts on megatron are actually running, but I'll try and have a look at it.

  10856   Tue Jan 6 03:09:17 2015 diegoUpdateLSCPRFPMI status & IFO status

 [Jenne, Rana, EricQ, Diego]

Tonight we worked on getting the IFO back in a working status after the break, and then tried some locking.

  • the MC is behaving better, it could stay in a stable condition for hours, even if a couple of times it lost lock, and one of them persisted for a little time;
  • we managed to get to arm power of 20ish, before losing lock (this happened a couple of times);
  • the main thing seems to be that we have only ~ 20 degrees of phase margin at UGF for DARM, which is evidently too little;
  • one hypothesis is that DARM may change sign due to some weird length/angular interaction, and that this messes up the actuation causing the lockloss;
  • one other possibility is that maybe, when arm power rises, there are some weird flashes that go back to the MC and then cause the locklosses, but this has to be verified;
  • attached there is a plot of the last lockloss (and a zoom of it), which seems to point at DARM as the culprit;

 Lockloss_20150106_074552.png

 

Lockloss_20150106_074552_zoom.png

 

We left the IFO uncontrolled and in a "flashy" state so that tomorrow we can look into the "back-flashing to the MC" hypothesis.

  10861   Wed Jan 7 02:56:15 2015 diegoUpdateLSCUGF Servo for DARM

 [Jenne, Diego]

Today we began implementing the UGF Servos. Things we did:

  • we updated the LSC model with both DARM and CARM servos, and moved them from after the control system to before it, at the level of the error signal;
  • we updated the medm screens; new buttons are located in the main LSC screen;
  • we started commissioning the DARM servo, at first using DARM for the lock of the single Y arm, then we moved on to the PRFPMI lock and the usual transition from ALS to Transmission;
  • although we had several lock losses during the night, we managed to tweak the parameters of the DARM UGF servo (phases, excitation, gains), which now seems to work sufficiently fine;
  • the filters added to the I and Q filter banks are a single lowpass in each, while the only filter in the main servio is a standard integrator;
  • we don't have a step response at the moment, but we can say that the settling time of the servo is in the range of 10 seconds;
  • we updated the ALSdown.py and ALSwatch.py scripts with a call to a new UGFdown.py script; this script, located in the scripts/PRFPMI folder, takes care of disabling the servos and putting the excitation to zero in case of a lock loss; re-enablement of such things must be done manually;
  10870   Wed Jan 7 14:35:44 2015 diegoUpdateSUSSUS Drift Monitor

The SUS Drift Monitor screen has been updated:

  • removed the old dead channels from the MEDM screen;
  • updated the SUS models with new 'mute' channels where the expected values should be put;
  • updated the MEDM screen with the new channels
  • values are still 0 since I don't know what these expected values should be, at this time

 150107_SUS_DRIFTMON_screen.png

  10881   Thu Jan 8 23:02:30 2015 diegoUpdateSUSSUS Drift Monitor

The MEDM screen has been updated: the new buttons, one for each optic, call the scripts/general/SUS_DRIFTMON_update_reference.py script, which measures (and averages) for 30s the current values of the POS/PIT/YAW drifts, and then sets the average as the new reference value.

 

  10888   Tue Jan 13 01:11:51 2015 diegoUpdateLSCResponse of error signals to MICH EXC

For several MICH offsets, I measured the response of REFL33Q, ASDC and the ratio ASDC/POPDC to a MICH EXC. It appears that there is no frequency-dependent effect. The plots for MICH_OFFSET = 0.0 and 2.0 are slightly lower in magnitude: the reason is they were the first measurements done, and after that a little realignment of BS was necessary, so probably that is the reason.

 

 

Attachment 1: MICH_to_REFL33Q_ASDC_12Jan2015_1.pdf
MICH_to_REFL33Q_ASDC_12Jan2015_1.pdf
Attachment 2: MICH_to_REFL33Q_ASDC_12Jan2015_2.pdf
MICH_to_REFL33Q_ASDC_12Jan2015_2.pdf
Attachment 3: MICH_to_REFL33Q_ASDC_12Jan2015_3.pdf
MICH_to_REFL33Q_ASDC_12Jan2015_3.pdf
  10896   Tue Jan 13 15:11:30 2015 diegoUpdateLSCTransitioned to ASDC MICH (PRMI and PRFPMI)

These are the parameters of the UGF servos we used last night:

DOF / Parameters Exc. Frequency (Hz) Exc. Gain Loop Gain
DARM 110.1 0.025 -0.03
MICH n/a n/a n/a
PRCL 150.001 2.0 -0.03
CARM 115.1 0.01 -0.03

 

Some tweaking of such parameters and the commissioning of the MICH servo will be done soon; an elog post about the UGF scripts/medm screens also will be done soon.

  10902   Thu Jan 15 03:18:11 2015 diegoUpdateLSCUGF servo now linear again

The UGF servos were recommissioned today:

  • suitable values of frequency, excitation, phases and gain were found;
  • the phases were chosen in order to maximize the I signal and suppress the Q one;
  • the servos seemed sufficiently stable when in a quiet state, but they didn't performed well in other cases;
  • I also found out that DARM & CARM and MICH & PRCL are maybe too much coupled, but that could be actually due to the main loops rather than the UGF ones;
  • however, after some weird rampings with no apparent reasons, and after some quite bad and glitchy step responses, I found out that the effect of the chosen phases vanished: the I and Q signals were of the same order of magnitude again, probably causing the bad performance;
  • Jenne and I tried to increase che SINGAINs and COSGAINs (but keeping them equal to each other): this has the good effect of separating more the I and Q signals, but it's just a zoom effect: there still are mixing effects and, more important, some zero-crossings into negative values that cause the signal going into the servo to go crazy.

Our idea is that we need with some thinking about these servos and most of all try to figure out all this phase thing before we can start to trust the servos to be used for locking.

  10911   Fri Jan 16 04:14:05 2015 diegoUpdateLSCUGF servo now linear again

UGF Servos' commissioning still going on, updates of today:

  • on Rana's suggestion, we don't use anymore the Q-signal rejection at the level of Phase 1 and Phase 2; instead, a proper complex division is made between those two signals (with a check in case of zero); then the resulting signal is demodulated with a new Phase 3, which is the one used to select the I signal while zeroing the Q one; changes to the model and the screens have been made;
  • a new evaluation of all the parameters for the four servos has been made; aside for the new phase, and the zeroing of the other phases (because they are not used anymore for the selection), the parameters are not dissimilar from the prevoius ones
  • the PRCL and MICH servos seem sufficiently stable;
  • CARM and DARM are stable only for a short amount of time; what usually happens is that one of the two starts drifting in one random direction, and usually the other one follows shortly after; it is not clear if there is a relation or if they stop being stable after a similar amount of time; I still noticed a few lowest limits appearing in the input signal, which should be avoided; I'll check the model again tomorrow;
  • the weird thing about CARM and DARM is that at the same time when one of them starts drifting, its I and Q signals begin to be comparable; when the servo is shut off, they resume their normal state;
  • an increase in the excitation gain improves the separation of I and Q and also reduces their variations, but a high peak in the loop due to this might not be a good idea.

 

  10916   Fri Jan 16 20:37:52 2015 diegoUpdateLSCUGF servo now linear again

I found an error in the model of the UGF servos, I have now corrected it; for future reference, now the division between TEST2 and TEST1 is properly done with complex math: given

TEST1 = a + i b\hspace{.5cm},\hspace{.5cm}}TEST2 = c + id

we have that TEST3:

 

TEST3 = \frac{TEST2}{TEST1} = \left(\frac{ac+bd}{a^2+b^2}\right) + \left(\frac{ad-bc}{a^2+b^2} \right)i

 

TEST3 is the actual signal that is now phase rotated to select only the I signal while rejecting the Q one.

 

All the updates to the model, the screens and the script have been SVNed.

  10926   Tue Jan 20 21:58:04 2015 diegoUpdateLSCSome locking, may need to modify UGF part again

 

Quote:

I have been playing with the IFO tonight.  Mostly, I wanted to make sure that all of the scripts for the carm_cm_up sequence were working, and they seem to all be fine. 

I also turned on all 4 UGF servos.  My big ah-ha moment for the night is that the excitation is multiplied by the gain multiplier.  This means that if the UGF servo is multiplying by a small number (less than 1), the excitation will get smaller, and could get small enough that it is lost in the noise.  Now the error signal for the UGF servo is very noisy, and can dip to zero.  Since we can't take the log of zero, there are limiters in the model, but they end up giving -80dB to the error point of the UGF servo.  This makes it all freak out, and often lose lock, although sometimes you just get a weird step in the UGF servo output. 

Anyhow, we need to be mindful of this, and offload the UGF servos regularly.  I think the better thing to do though will be to divide the excitation amplitude by the gain multiplier.  This will undo the fact that it is multiplied by that number, so that the number of counts that we put into the excitation amplitude box is what we expect. 

 

After some brainstorming with Jenne and Q, both the model and the medm screen have been modified: the entire block "Test1 - injection of the excitation - Test2" has been moved after the servo output. In this way we avoid completely the multiplication problem without having to perform divisions that could lead to division-by-zero problems. Because of how the logic is done now, one UnitDelay block had to be inserted before each one of Test1 and Test2.

 

Since the UGF Servo has been heavily modified lately, I'll post the current status of the model (as an attachment, as inpage images lose too much quality).

 

Attachment 1: UGF_SERVO_MDL.png
UGF_SERVO_MDL.png
  10930   Thu Jan 22 15:35:41 2015 diegoUpdateSUSBounce/Roll Measurements

I measured the bounce/roll frequencies for all the optics, and updated the Mechanical Resonances wiki page accordingly.

I put the DTT templates I used in the /users/Templates/DTT_BounceRoll folder; I wrote a python script which takes the exported ASCII data from such templates and does all the rest; the only tricky part is to remember to export the channel data in the order "UL UR LL" for each optic; the ordering of the optics in a single template export is not important, as long as you remember it...

Anyhow, the script is documented and the only things that may need to be modified are:

  • lines 21, 22: the "starting points" FREQ_B and FREQ_R (to accomodate noisy or bad data, as ETMX was for the Roll part in both the measurements I took);
  • line 72: the parameters of the slepian window used to average the data: the first one is the most important and indicates how much averaging will happen; more averaging means less noise but broader and lower peaks, which shouldn't be a big issue since we care only about the peak position, not its amplitude; however, if the peak is already shallow, too much averaging will make things worse instead of better;
  • lines 110, 118: the initial guess for the fit parameters;

The script is in scripts/SUS/BR_freq_finder.py and in the SVN. I attach the plots I made with this method.

Attachment 1: BR_Jan2015.tar.bz2
  10931   Thu Jan 22 18:36:11 2015 diegoUpdateIOOMC Flashes

I've been looking into the data of Jan 06 and Jan 15 taken during daytime, as the night before we left the PRC aligned in order to allow the IFO to flash; the purpose is to find out if some flashes from the IFO could propagate back to the IMC and cause it to lose lock; I will show here a sample plot, all of the others are in the archive attached.

My impression is that these locklosses of the IMC are not caused by these flashes: the signals MC_[F/L] seem quite stable until the lock loss, and I don't see any correlation with what happens to REFLDC that could cause the lockloss (apart from its drop as a consequence of the lockloss itself); in addition, in most occasions I noticed that the FSS started to go crazy just before the lock loss, and that suggests me that the lockloss source is internal to the IMC.

I can't see anything strange happen to MC_TRANS either as long as the IMC is locked, no fluctuations or weird behaviour. I also plotted the MC_REFL_SUM channel. but it is too slow to be useful for this kind of "hunt".

Attachment 1: 1104612646_zoom_1.png
1104612646_zoom_1.png
Attachment 2: elog.tar.bz2
  10932   Thu Jan 22 22:15:30 2015 diegoUpdateSUSCentered OpLevs

[Diego, Jenne]

We centered the OpLevs for ITMX and ITMY.
 

  10944   Tue Jan 27 15:45:26 2015 diegoUpdateLSCSmall tweaks to the locking

The UGF Servo medm page has been updated to reflect the last changes, namely the return of the sum of squares and the disappearance of Test3.

 

  10960   Fri Jan 30 03:12:15 2015 diegoUpdateLSCCARM on REFL11I

[Jenne, Diego]

Tonight we continued following the plan of last night: perform the transition of CARM to REFL11_I while on MICH offset at -25%:

  • we managed to do the transition several times, keeping the UGF servos on for MICH and PRCL but turning off the DARM and CARM ones, because their contribution was rather unimportant and we feared that their excitations could affect negatively the other loops (as loops tend to see each other's excitation lines);
  • we had to tweak the MICH and PRCL UGF servos:
    • the excitation frequency for MICH was lowered to ~41 Hz, while PRCL's one was lowered to ~50 Hz;
    • PRCL's amplitude was lowered to 75 because it was probably too high and it affected the CARM loop, while MICH's one was increased to 300 because during the reduction of the CARM offset it was sinking into the noise; after a few tries we can say they don't need to be tweaked on the fly during the procedure but can be kept fixed from the beginning;
    • after the transition to REFL11_I for CARM, we engaged also its UGF servo, still at the highest frequency of the lot (~115 Hz) and with relatively low amplitude (2), to help keeping the loop stable;
    • as DARM was still on ALS, we didn't engage its UGF servo during or after the transition, but we just hold its output from the initial part of the locking sequence (after we lowered its frequency to 100 Hz;
  • however, at CARM offset 0 our arm power was less that what we had yesterday: we managed to get higher than ~8, but after Koji tweaked the MC alignment we reached ~10; we still don't understand the reason of the big difference with respect to what the simulations show for MICH offset at 25% (arm power ~50);
  • after the CARM transition to REFL11_I we felt things were pretty stable, so we tried to reduce the MICH offset to get us in the ~ -10% range, however we never managed to get past ~ -15% before losing lock, at arm power around 20;
  • we lost lock several times, but for several different reasons (IMC lost lock a couple of times, PRCL noise increased/showed some ringing, MICH railed) but our main concern is with the PRCL loop:
    • we took several measurements of the PRCL loop: the first one seemed pretty good, and it had a bigger phase bubble than usual; however, the subsequent measurements showed some weird shapes we struggle to find a reason for; these measurements were taken at different UGF frequencies, so maybe it is worth looking for some kind of correlation; morever, in the two weird measurements the UGFs are not where they are supposed to be, even if the servo was correctly following the input (or so it seemed); the last measurement was interrupted just before we lost lock because of PRCL itself;
    • we noticed a few times during the night that the PRCL loop noise in the 300-500 Hz range increased suddenly and we saw some ringing; at least a couple of times it was PRCL who threw us out of lock; this frequency range is similar to the 'weird' range we found in our measurements, so we definitely need to keep an eye on PRCL on those frequencies;
  • in conclusion, the farthest we got tonight was CARM on REFL11_I at 0 offset, DARM at 0 offset still on ALS and MICH at ~ 15% offset, arm power ~20.

 

Attachment 1: PRCL_29Jan2015_Weird_Shape.pdf
PRCL_29Jan2015_Weird_Shape.pdf
Attachment 2: ArmPowers20_MICHoffsetBeingReduced_0CARMoffset_29Jan2015.pdf
ArmPowers20_MICHoffsetBeingReduced_0CARMoffset_29Jan2015.pdf
  10965   Mon Feb 2 22:59:49 2015 diegoUpdateLSCCM board input switched to AS55

[Diego, Jenne]

We just changed the input to the CM board from REFL11 to AS55.

 

  10966   Tue Feb 3 04:01:55 2015 diegoUpdateLSCCM servo & AO path status

[Diego, Jenne]

Tonight we worked on the CM board and AO path:

  • at first we changed the REFL1 input to the CM board from REFL11 to AS55, as written in my previous elog; we tried following Koji's procedures from http://nodus.ligo.caltech.edu:8080/40m/9500 but we didn't get any result: we could lock using the regular digital path but no luck at all for the analog path;
  • then we decided to follow the procedure to the letter, using POY11Q as input to the CM board;
    • we still couldn't lock following the Path #2, even after adjusting the gains to match the current configuration for the Yarm filter bank;
    • we had some more success using Path #1, but we had to lower the REFL1 Gain to ~3-4 (from the original 31) because of the different configuration of the Yarm filter bank, in order to have the same sensing in both of them; we managed to acquire lock a few times, it's not super stable but it can keep lock for a while;
    • when we tried to increase the gain of the MC filter bank and the AO Gain, however, we immediately had some gain peaking, and we couldn't go further then 0.15 and 9db respectively. We currently don't have an answer for that.
    • anyhow, we took a few measurements with the SR785:

 

The BLUE plot is at MC Gain = 0.10 and REFL1 Gain = 4dB; the GREEN plot is for MC Gain = 0.10 and REFL1 Gain = 3dB, which seemed a more stable configuration; after this last configuration, we increased the MC Gain to 0.15 and the AO Gain from 8dB to 9dB and took another measurement, the RED plot; this is as far as we got as of now. We also couldn't increase the REFL11 Gain because it made things unstable and more prone to unlock.

So, some little progress on the AO path procedure, but we are very low on our UGF and we have to find a way to increase our gains without breaking the lock and avoiding the gain peaking we have witnessed tonight.

 

Notes:

  • is the REFL1 Gain dB slider supposed to go to negative dBs? During the night we also tried to use negative dBs, but it seemed it wasn't doing anything instead;
  • when we plugged POY11Q to the CM board, we noticed that it wasn't connected to anything at the moment; since we phase rotate POY11, we were assuming that we were using that signal somewhere. We are confused by this...
  • we remind that REFL11 is no more connected to the CM board input, as POY11 is.
Attachment 1: CARM_03-02-2015_031754.pdf
CARM_03-02-2015_031754.pdf
  10971   Wed Feb 4 04:51:14 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Jenne, Eric]

Tonight we kept on following our current strategy for locking the PRFPMI:

  • the first few tries were pretty unsuccessful: the PRMI lock wasn't much stable, and we never managed to reduce CARM offset to zero before losing lock;
  • then we did some usual manteinance: we fixed the X arm green beatnote, fixed the phase tracker and given much attention to ASS alignment, since the X arm wasn't doing great;
  • the last few locks were consintently better: we managed to get to CARM offset zero "easily", but the arm power was not very high (~8);
  • then we tried to transition CARM to REFL11, both with the usual configuration and using CM_SLOW, using REFL11 as input for the Common Mode Board;
    • with the usual configuration, we lost lock right after the transition, because of MICH hitting the rail;
    • we did a very smooth CARM transition directly to REFL11 on the CM_SLOW path; we managed to take a spectrum with the SR785, but we couldn't take any more measurements before losing lock because of some weird glitch, as we can see from the lockloss plot;
  • another thing that helped tonight was changing the ELP of the MICH filter bank: it went from 4th order to 6th order, and from 40 dB suppression to 60 dB suppression;

both of the last two locks, the most stable ones (one transition to usual REFL11 and one transition to "CM_SLOW" REFL11) were acquired actuating on MC2;

 


EDITs by JCD:  At least one of the times that we lost PRMI lock (although kept CARM and DARM lock on ALS), was due to MICH hitting the rail, even after we increased the limiter to 15,000 counts.


 Here is the transfer function between CARM ALS (CARM_IN1) and REFL11 coming through the CM board (CARM_B), just before we transitioned over.  Coherence was taken simultaneously as usual, I just printed it to another sheet.

CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf

CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf


Here is the lockloss plot for the very last lockloss.  This is the time that we were sitting on REFL11 coming through the CM_SLOW path.  A DTT transfer function measurement was in progress (you can see the sine wave in the CARM input and output data), but I think we actually lost lock due to whatever this glitch was near the right side of the plots.  This isn't something that I've seen in our lockloss plots before.  I'm not sure if it's coming from REFL11, or the CM board, or something else.  We know that the CM board gives glitches when we are changing gain settings, but that was not happening at this time.


Q: Here's the SR785 TF of CARM locked through CM board, but still only digital control; nothing exciting. Excitation amplitude was only 1mV, which explains the noisy profile. 

Attachment 1: CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf
CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS.pdf
Attachment 2: CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf
CARM_3Feb2015_CarmBwasCMslow_CarmAwasLiveALS_Coh.pdf
Attachment 3: Glitch_in_CARM_and_PRCL_3Feb2015.png
Glitch_in_CARM_and_PRCL_3Feb2015.png
Attachment 4: slowCM_04-02-2015_042805.png
slowCM_04-02-2015_042805.png
  10979   Thu Feb 5 04:35:14 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Eric]

Tonight was a sad night... We continued to pursue our strategy, but with very poor results:

  • before doing anything, we made sure we had a good initial configuration: we renormalized the arm powers, retuned the X arm green beatnote, did extensive ASS alignment;
  • since the beginning of the night we faced a very uncooperative PRMI, which caused a huge number of locklosses, often just by itself, without even managing to reduce the MICH offset before reducing the CARM one;
  • we had to reduce the PRCL gain to -0.002 in order to acquire PRMI lock, but keeping it such or restoring it to -0.004 once lock was acquired either didn't improve the PRMI stability at all;
  • we also tweaked a bit the PRCL and MICH UGF servos (namely, their frequencies to ~80 Hz and ~40 Hz respectively) and that seemed to help earlier during the night, but not much longer;
  • we only managed to transition CARM to REFL11 via CM SLOW twice;
    • the first time we lost lock almost immediately, probably because of a non-optimal offset between CARM A and B;
    • the second time we managed to stay there a little longer, but then some spike in the PRCL loop and/or the MICH loop hitting the rails threw us out of lock (see the lockloss plot);
    • both times we transitioned at arm power ~18;
  • during the night we used an increased analog ASDC whitening gain, as from Eric's elog here http://nodus.ligo.caltech.edu:8080/40m/10972 ; even with this fix, though, MICH is still often hitting the rails and causing the lock losses;
  • the conclusion for tonight is that we need to figure what is going on with the PRMI...

 

Attachment 1: 4Feb2015_Transition_CARM_REFL11_CM_SLOW_AP_18.png
4Feb2015_Transition_CARM_REFL11_CM_SLOW_AP_18.png
  10982   Fri Feb 6 03:21:17 2015 diegoUpdateLSCCARM Transition to REFL11 using CM_SLOW Path

[Diego, Jenne]

We kept struggling with the PRMI, although it was a little better than yesterday:

  • we retuned the X Green beatnote;
  • we managed to reach lower CARM offsets than yesterday night, but we still can't keep lock long enough to perform a smooth transition to CM SLOW/REFL11;
  • we tweaked MICH a bit:
    • the ELP in FM8 now is always on, because it seems to help;
    • we tried using a new FM1 1,1:0,0 instead of FM2 1:0 because we felt we needed a little more gain at low frequencies, but unfortunately this didn't change much MICH's behaviour;
    • now, after catching PRMI lock, the MICH limiter is raised to 30k (in the script), as a possible solution for the railing problem; the down/relock scripts take care of resetting it to 10k while not locked/locking;

So, still no exciting news, but PRMI lock seems to be improving a little.

  10990   Mon Feb 9 17:23:17 2015 diegoUpdateComputer Scripts / ProgramsNew laptops

I forgot to elog about these ones, my bad... The new/updated laptops are giada, viviana and paola; paola is already in the lab, while giada and viviana are in the control room waiting for a new home. The Pool of Names Wiki page has already been updated to reflect the changes.

  10991   Mon Feb 9 17:47:17 2015 diegoUpdateLSCCM servo & AO path status

I wrote the script with the recipe we used, using the Yarm and AS55 on the IN2 of the CM board; however, the steps where the offset should be reduced are not completely deterministic, as we saw that the initial offset (and, therefore, the following ones) could change because of different states we were in. In the script I tried to "servo" the offset using C1:LSC-POY11_I_MON as the reference, but in the comments I wrote the actual values we used during our best test; the main points of the recipe are:

  • misalign the Xarm and the recycling mirrors;
  • setting up CARM_B for POY11 locking and enabling it;
  • setting up CARM_A for CM_SLOW;
  • setting up the CM_SLOW filter bank, with only FM1 and FM4 enabled;
  • setting up the CARM filter bank: FM1 FM2 FM6 triggered, only FM3 and FM5 on; usual CARM gain = 0.006;
  • setting up CARM actuating on MC2;
  • turn off the violin filter FM6 for MC2;
  • setting up the default configuration for the Common Mode Servo and the Mode Cleaner Servo; along with all the initial parameters, here is where the initial offset is set;
  • turn on the CARM output and, then, enable LSC mode;
  • wait until usual POY11 lock is acquired and, a bit later, transition from CARM_B to CARM_A;
  • then, the actual CM_SLOW recipe:
    • CM_AO_GAIN = 6 dB;
    • SUS-MC2_LSC FM6 on (the 300:80 filter);
    • CM_REFL2_GAIN = 18 dB;
    • servo CM_REFL_OFFSET;
    • CM_AO_GAIN = 9 dB;
    • CM_REFL2_GAIN = 21 dB;
    • servo CM_REFL_OFFSET;
    • CM_REFL2_GAIN = 24 dB;
    • servo CM_REFL_OFFSET;
    • CM_REFL2_GAIN = 27 dB;
    • servo CM_REFL_OFFSET;
    • CM_REFL2_GAIN = 31 dB;
    • servo CM_REFL_OFFSET;
    • CM_AO_GAIN = 6 dB;
    • SUS-MC2_LSC FM7 on (the :300 compensating filter);

I tried the procedure and it seems fine, as it did during the tries Q and I made; however, since it touches many things in many places, one should be careful about which state the IFO is into, before trying it.

The script is in scripts/CM/CM_Servo_OneArm_CARM_ON.py and in the SVN.

 

  150   Fri Nov 30 20:13:57 2007 dmassSummaryGeneralHeNe UniPhase Laser
Data for the Uniphase 1.9 mW HeNe laser (labeled: "051507 From ISCT-BS") SN: 1284131 Model: 1103P

I used the Photon Beamscanner to obtain all data, then fit w(z) as shown on the plot with parameters w_0, z_R, and hidden parameter delta,
where z = delta + x, z is waist distance, x is distance from the laser.

Copies of the matlab code used to fit (/plot) are attached in .zip below.
Attachment 1: Matlabcode.zip
Attachment 2: UniPhaseWaist.jpg
UniPhaseWaist.jpg
  192   Sun Dec 16 16:52:40 2007 dmassUpdateComputersComputer on the end Fixed
I had Mike Pedraza look at the computer on the end (tag c21256). It was running funny, and turns out it was a bad HD.

I backed up the SURF files as attachments to their wiki entries. Nothing else seemed important so the drive was (presumably) swapped, and a clean copy of xp pro was installed. The username/login is the standard one.

Also - that small corner of desk space is now clean, and it would be lovely if it stayed that way.
  4978   Fri Jul 15 19:00:18 2011 dmassMetaphysicselogCrashes

Elog crashed a couple times, restarted it a couple times.

  15387   Tue Jun 9 15:02:56 2020 eHangUpdateBHDAstigmatism and scattering plots

Using the updated AOI's for the LO path: (4.8, 47.9, 2.9, 4.5) deg for (LO1, LO2, LO3, LO4), we obtain the following results. 

First two plots are scattering plots for the t and s planes, respectively. Note that here we have changed to 0.5% fractional RoC error and 3 mm positional error. We have also changed the meaning of the colors: pink:MM>0.98; olive 0.95<MM<=0.98, and grey MM<=0.95. It seems that both planes would benefit statistically if we make the LO3-LO4 distance longer by a few mm. 

We also consider how much we could compensate for the MM error in the last plot. We have a few mm window to make both planes better than 0.95. 

Attachment 1: LO_MM_t_scat_stock.pdf
LO_MM_t_scat_stock.pdf
Attachment 2: LO_MM_s_scat_stock.pdf
LO_MM_s_scat_stock.pdf
Attachment 3: LO_MM_adj_stock.pdf
LO_MM_adj_stock.pdf
  7294   Tue Aug 28 11:28:31 2012 ericqUpdatePSLPMC alignment going bad

Quote:

PMC transmission started going down this afternoon, around 3pm-ish.  Right now it's 0.775, which is very, very low.  The new MC locking stuff is engaged, so it's not the FSS slow servo's fault. 

EDIT: I just realized that the limit of 0 counts output of the MC2 MCL filter bank was still engaged, from a time earlier this afternoon when I had switched back to the old servo, so there was no feedback going back to keep the slow drift of the laser in check.  PMC trans isn't coming back instantly, so I'll check it again when I come in tomorrow.

 

By adjusting the PMC steering mirrors, Jenne and I realigned the PMC input beam. Transmission is at 0.829 now. 

  7295   Tue Aug 28 16:27:22 2012 ericqUpdatePSLPBS and Half Wave plates introduced

[Jenne, Eric]

We installed a Half Wave Plate -> Polarized Beam Splitter -> Half Wave Plate in the PSL beam line, immediately after the EOM, to be used for attenuating the beam when we vent, as in Entry 6892.

It was illuminating to discover that the optics labeled QWP0-1064-10-2 are indeed half wave plates, instead of quarter wave plates as QWP suggests. 

The PBS transmits "P"/Horizontal polarization, but the beam coming from the EOM is "S"/Vertically polarized, and we want to keep that, since we do not want the beam attenuated quite yet. 

So, we use the HWP to rotate the P from the EOM to S, so that the majority of the power passes through the PBS. The second HWP then rotates the transmitted S back into P, which continues to the mode cleaner. When we want to attenuate, we will simply rotate the first HWP to change the proportion of S polarized light that will pass straight through the PBS and towards the mode cleaner. 

After setting the proper HWP angles, we aligned the PBS via minimizing the MC reflection.

Since we have not yet attenuated the power, we have not yet changed the BS for the MC reflection, since this would damage the PD. The beam splitter will be changed out for a 100% reflectivity mirror to increase the power to the PD when we do.

 

  7297   Tue Aug 28 17:16:54 2012 ericqUpdatePSLPower reduced!

We have now reduced the power being input to the MC from 1.25W to 10mW, and changed out the MC refl BS for a mirror. 

The power was reduced via the PBS we introduced in Entry 7295.

While we were in there, we took a look at the AS beam, which was looking clipped on the monitor. Jenne felt that it appears that the clipping seems to be occurring inside the vacuum, possibly on the faraday. This will be investigated during the vent. 

  7306   Wed Aug 29 11:47:21 2012 ericqUpdateVACVenting

 [Steve, Eric]

I've been helping Steve vent this morning. The following things were done (from Steve's logbook):

  • Particle counts: 0.5 micron particles, 4200 counts per cubic ft
  • Vertex crane drive checked to be ok
  • Optical Levers set for local damping only
  • Saved some screens
  • PSL shutter and green shutters closed
  • HV Off checked, JAM nuts checked
  • Vac: Close V1, VM1, ans - VA6, open VM3 - RGA, cond: chamber open mode
  • 8AM: VV1 open to N2, regulator set  to 14 psi
  • 8:23AM: 35psi Instrument grade Air

(At this point, I took over the air canisters, while Steve made preparations around the lab. 

  • 9:00AM: 2nd air cylinder, 14 psi 
  • 9:40AM: 3rd air cyl
  • 10:20AM: 4th air cyl
  • 11:00AM: 5th air cyl

With the 5th cylinder, we began approaching 1 atm, so we slowed the regulator down to 5psi. Around 750 torr, Steve opened VV1 to air.

According to Steve, we will be at atmospheric pressure at  ~12:30pm.

  7308   Wed Aug 29 17:02:41 2012 ericqUpdatePSLPower reduced!

Quote:

We have now reduced the power being input to the MC from 1.25W to 10mW, and changed out the MC refl BS for a mirror. 

The power was reduced via the PBS we introduced in Entry 7295.

While we were in there, we took a look at the AS beam, which was looking clipped on the monitor. Jenne felt that it appears that the clipping seems to be occurring inside the vacuum, possibly on the faraday. This will be investigated during the vent. 

 The power has been increased to 20mW. We got the 10mW number from the linked elog entry above. However, after venting we were having problems locking the MC. Upon investigating past elog posts, we found that 20mW was actually the power used in the past. The MC will now autolock. 

  7337   Tue Sep 4 13:50:26 2012 ericqUpdatePSLPMC Realigned, power adjusted

 I adjusted the PMC alignment this morning, brought the transmission up to 0.83V.

After the lunch meeting, we found the the MC transmission was higher than recently seen. Turned out the HWP had drifted, causing 30mW to be input to the MC. I adjusted it back down to 20mW. 

  7377   Wed Sep 12 20:08:51 2012 ericqUpdateElectronicsAS beam scan

Quote:

We conducted a beam scan on the AP table of the AS beam. We used a lens to focus the beam onto a power meter, and slowly moved a razor blade across the beam using a micrometer, vertically and horizontally both in front of and behind the beam. We also had to block the beam next to the AS beam in order to do this, but is unblocked now. Mike will begin curve fitting the data to try and see if there is a different spot size given by the x-axis vs. the y-axis, and if the lens has any effect.

 [ericq, mikej, some input from zach]

After realigning the MC, the measurement was repeated this afternoon. This time, however, we isolated the beam from ITMY by misaligning ITMX. The beam looked somewhat elliptical to me, and Mike should have fits up tonight. Afterwards, ITMX was returned to the position I found it in, and the PMC shutter and access connector were closed. (Sorry about last night!)

  7958   Tue Jan 29 20:28:11 2013 ericqUpdateGeneralEarly work on Mirror Mounts

 [Q, Chloe]

Chloe has been to the lab twice to start up her investigations in acoustic noise coupling to mirrors. The general idea for the setup is a HeNe laser bouncing off a mirror and onto a QPD, whose signal provides a measure of beam displacement noise. The mirror will be mounted and excited in various ways to make quantitative conclusions about the quality of different mounting schemes.

We have set up the laser+mirror+QPD on the SP table, and collected data via SR560s->SR785, with the main aim of evaluating the suitability of this setup. The data we collected is not calibrated to any meaningful units (yet). For now, we are just using QPD volts.

Chloe collected data of vertical displacement noise for the following schemes: Terminated SR785 input, Terminated SR560 inputs, Laser centered directly onto the QPD, Laser shining on mirror centered on QPD, laser/mirror/qpd with some small desktop speakers producing white noise from http://www.simplynoise.com. Data shown below. 

early.pdf

 

 

  9442   Wed Dec 4 21:41:09 2013 ericqUpdateGreen LockingGreen PDH Characterization

 My job right now is to characterize the green PDH loops on each arm. Today, Jenne took me around and pointed at the optics and electronics involved. She then showed me how to lock the green beams to the arms (i.e. opening the shutters until you hit a TM00 shape on the transmitted beam camera). Before lunch, the y arm was easiest to lock, and the transmitted power registered at around 0.75. 

After lunch, I took a laptop and SR785 down to the y end station. I unhooked the PDH electronics and took a TF of the servo (without its boost engaged, which is how it is currently running) and noise spectrum with the servo input terminated.

I then set up things a la ELOG 8817 to try and measure the OLTF. However, at this point, getting the beam to lock on a TM00 (or something that looked like it) was kind of tough. Also, the transmitted power was quite a bit less than earlier (~0.35ish), and some higher order modes were higher than that (~0.5). Then, when I would turn on the SR785 excitation, lock would be lost shortly into the measurement, and the data that was collected looked like nonsense. Later, Koji noted that intermittent model timeouts were moving the suspensions, thus breaking the lock. 

We then tried to lock the x arm green, to little success. Koji came to the conclusion that the green input pointing was not very good, as the TM00 would flash much less brightly than some of the much higher order modes. 

Tomorrow, I will measure the x arm OLTF, as it doesn't face the same timeout issue that is affecting the y arm.

  9447   Fri Dec 6 12:45:51 2013 ericqUpdateGreen LockingGreen PDH Characterization

Yesterday, made a slew of measurements on the X-arm when locked on green. By tweaking the temperature loop offset and the green input PZT pointing, I was able to get the transmitted green to around 1.0. The PDH board gain was set to 4.0. I had trouble making swept sine measurements of the OLTF; changing the excitation amplitude for different frequency ranges would result in discontinuities in the measured TF, and there was only a pretty narrow band around the UGF that seemed to have reasonable coherence.

So, I used the SR785 as a broadband noise generator and measured the TF via dividing the spectra in regions of coherence. Specifically, I used the "pink noise" option of the SR785. I also used a SR560 as a low pass to get enough noise injected into the lower frequency range to be coherent, while not injecting so much into the higher frequencies that the mode hopped while measuring. 

The servo board TF was easily fitted to a 4th order zpk model via VFIT, but I'm having trouble fitting the OLTF. (There is a feature in the servo TF that I didn't fit. This is a feature that Zach saw [ELOG 9537], and attributed to op amp instability) Plots follow. Also, while these need to be calibrated to show the real noise spectrum of the cavity motion, I'm attaching the voltage noise spectra of the error and control signals as a check that electronics/PD noise isn't dominating either signal. 

LoopTF.pdfServoTF.pdf

MixerOutput.pdfServoOutput.pdf

  9459   Thu Dec 12 21:23:15 2013 ericqUpdateGreen LockingBetter Xarm OLTF

With the newly repaired PDH board, I spent some time with the x arm green PDH loop. I found it SO MUCH EASIER to measure the OLTF by injecting before the servo, instead of after it. (i.e. I added a swept sine from the SR785 to the mixer output (error signal) before the servo input). This is likely because the error signal is much flatter. I used a 10mV excitation across the whole frequency range (30-100kHz). 

Here's the OLTF. I'm working on fitting it and breaking it up into its constituent TFs, then making a rudimentary noise budget. 

Dec12_Xarm_OLTF.pdf

  9496   Thu Dec 19 19:45:12 2013 ericqUpdateGreen LockingX-Arm Green PDH Loop Stuff
With the fixed servo box, I remeasured the OLTF, the servo, and the low pass filter between the mixer output and servo input. Dividing the OLTF by the servo and LPF transfer functions should just leave the the [laser PZT->cavity->PD] transfer function, which should have the shape of the cavity pole plus any delay in the loop, up until the PZT is no longer linear / the measurement has bad SNR.

I'm missing a few pieces of the loop. While I know the PD gain in V/W, I don't know how much power is in the sideband, which affects the slope of the PDH error function. Also, I've found old ELOG posts mentioning either 1 or 5MHz/V being the NPRO PZT response, but am not sure how to determine what it actually is. These are essentially just scalars though, so finding the reason for low phase margin doesn't depend on them.

Here are the TFs I've measured ("residual" refers to OLTF/(servo*LPF)):



The teal "residual" TF presumably owes its shape to the cavity pole + the time delay around the loop. Messing around with the data, the shape fits very well to a real pole at 27kHz and a ~3usec delay. I have no real way to back that up as the unique truth behind it, however. Is there a good way to measure the delay? Without assuming any delay, the shape is best fit by a real pole at 26kHz and some funky complex zeros.

Another thing to look at is the CLG implied by the measurement of the OLTF, given by 1/(1-G). I plotted this quantity for the measured loop, and also for G/2 and 3G/2 to get an idea for how it changes as you turn the servo gain knob. I measured with the knob at 4.0. There seems to be quite a bit of gain peaking!



Also, I drew up a simple block diagram sort of thing to show how everything is connecting down at the green electronics rack at the end of the X arm (while totally glossing over the optical elements involved). This hopefully helps anyone who wants to inspect/take apart/massacre the setup.

  9539   Wed Jan 8 16:08:52 2014 ericqSummaryLSCEffect of PRC length mismatch on error signals

 [ericq,Gabriele]

So, we want an relatively quick measurement of the PRC length error (with sign!) at the order of .5 centimeter or so. Rana suggested the "demodulation phase method," i.e. lock the simple Michelson, measure what demodulation phase brings the 1F signal entirely within the phase quadrature, then lock the PRMI and measure the demodulation phase again. This tells you something about the length of the PRC. 

Gabriele and I worked through a simulation using MIST to determine how to actually do this. We simulated the case of injecting a line at 1kHz in the laser frequency via the laser's PZT and looking at the transfer function of the 1kHz signal to the I and Q at the 1F AS demodulated signal when locked. (Michelson locked on the dark fringe, PRC locked on 11MHz sideband) With the I and Q in hand, we can measure some demodulation phase angle that would bring everything into I. 

When the PRC length is in the ideal location, the demodulation phases in the two cases are the just about the same. Sweeping the length of the PRC around the ideal length gives us a monotonic function in the difference in the demodulation phases:

phaseVlength.pdf

So, with this simulation, we should be able to calibrate a measured difference in demod phase into the length error of the cavity! We will proceed and report...

  9544   Thu Jan 9 17:58:31 2014 ericqSummaryLSCEffect of PRC length mismatch on error signals

[ericq, Gabriele, Manasa]

 We wanted to perform the PRC length measurement today with an AS11 signal, but such a signal didn't exist. So, we have temporarily connected the AS110 PD signal (which is some Thorlabs PD, and not a resonant one) into the REFL11 demod board. 

We then proceeded with the goal of locking the PRC with REFL165. A few parameters that were changed along the way as we aligned and locked things:

  • the XARM gain was increased from 0.4 to 0.5 to help it acquire lock
  • the MICH gain was decreased from -10 to -5 since there was some gain peaking in its servo output
  • the REFL165 demodulation phase was changed from 155 to 122, to place a PRCL excitation entirely within I (we did this while locked on the carrier)

Sadly, in the end, we couldn't lock the PRC on a sideband in a stable manner. The alignment would drift faster than we could optimize the alignment and gains for the PRC. I.e. we would lock the PRC on the carrier, align PRM (and maybe touch ITMX) to maximize POPDC, switch to sideband locking, try to lock, and things would start looking misaligned. Switching back to carrier locking, the beam spots on REFL (for example) would have moved.

Manasa noted the MC_TRANS_Y has been substantially drifting along with small drift in MC_TRANS_P as well. So we need to fix the source of the mode cleaner beam drifting if we want to make this measurement. 

  9560   Thu Jan 16 21:38:13 2014 ericqUpdateLSCRepeat of PRC length measurement

[ericq,Jenne]

Since we don't have agreement between the measurements we made the other day and the earlier estimations, I wanted to repeat the demodulation angle measurement. We had to do a few things to keep the PRMI locked, since in the last few days, it hasn't been stable enough.

The mode cleaner had been very fussy lately; the WFS were pushing in a way that caused fast oscillations of the transmission and reflection powers. I turned off the servos, manually aligned the mode cleaner to transmission of about 15k and refl of about .4, centered the beams on the WFS QPDs, and turned the loops back on. Things were much stable after that. Also, Jenne noticed that the PMC loop had walked the laser PZT temperature to a bad place, and fixed it.

After aligning the carrier locked PRMI, the last piece needed to get things stable enough for sideband locking was turning off the angular damping on the PRM suspension screen (this was turned back on when we were done). Waiting until evening noise levels probably helped too. We used a 1000 count MICH excitation in the PRMI case, and recorded data for about a minute in one degree steps around the demodulation phase that looked to put the excitation entirely within the Q of the PD. Also, we notched out the excitation frequency in the MICH servo bank for today's measurement; I think it's outside of the loop bandwidth anyways, but it's good to be sure. 

Jenne and I pondered a bit whether changing the AS55 demodulation phase while it (AS55 Q) is being used as the MICH control signal introduces subtleties that we haven't anticipated, but couldn't come up with anything concrete. Changing the angle from the what maximizes the Q just looks like a slight change in MICH gain, and shouldn't affect the phase of the excitation signal on the PD...

In any case, the data have been recorded, and the results will follow soon. 

  9566   Wed Jan 22 16:36:45 2014 ericqUpdateElectronicsRF distribution box power button fail

Quote:

Rana, Gabriele and I are trying to measure the FSR of the PRC (elog about that later), and we turned off the power to the RF generation box so that we could switch cables at the EOM combiner.  However, as in elog 9101, the power button won't latch when we try to turn the power back on.  All 3 of us tried, to no avail.  For our measurement, poor Gabriele is standing holding the button pushed in, so that we can have some RF sidebands. 

Tomorrow, we'll have to pull the RF generation box, and put in a better switch.

I replaced the stupid broken fancy button with a simple sturdy switch. I had to file out the hole in the chassis a bit, but the switch is pressed in tightly and securely. I put the box back in the rack, but the power cable was coming directly from the power supplies with no fuses. The box was drawing ~.9 and 1.5 Amps from two supplies, so I put 2A fuses on both. Plugged everything back in, and the mode cleaner locks, so it looks like all is well.

RXA: When its so close, I prefer to size it up by 1 step. Please change to 5A fuses. Otherwise, we may blow them from power glitches.

Q: 5A fuses have been swapped in

ELOG V3.1.3-