The other night (before the holidays), I tried ALS offset tuning with IR POX/POY signals and it worked pretty good.
I didn't need to tune the offset after the scanning script stopped.
Once we are at the foot hill of the main resonance, I ran something like
ezcaservo -r C1:LSC-POX11_I_MON C1:LSC-ALSX_OFFSET -g -0.003 &
ezcaservo -r C1:LSC-POY11_I_MON C1:LSC-ALSY_OFFSET -g -0.003 &
(... I am writing this with my memory. I could be wrong but conceptually the commands looked like these)
I borrowed the Olympus and forgot to leave a note - I should have it for at most a day. dmassey@ligo if you need it urgently
These spectra were taken with the arm cavity length locked to the PSL frequency using POX as an error signal, and the EX laser frequency locked to the XARM cavity length by the analog PDH servo at EX, so there is no feedback control with the ALS beat signal as an error signal.
My goal was to do some further characterization of the IR ALS system tonight. With POX as an OOL sensor, I measured an RMS displacement noise of 8 pm with the arm under ALS control. I calculated the CARM linewidth to be 77 Hz (=10.3 pm) for the 40m parameters, assuming 30ppm arm loss. Fuurthermore, this number is 3x better than the 24 pm RMS quoted in the Izumi et. al. paper. Of course I am quoting the best results from my efforts tonight. Conclusions:
Since the stability and noise seemed quite good, I decided to collect some arm scan data to give to our modeSpec SURFs to practice fitting (which is the short dip in TRX in Attachment #4). Although after the discussion with Rana today, I think it may be that we want to do this measurement in reflection and not transmission, and look for a zero crossing in the PDH signal. In any case, I was able to scan 7 FSRs without any issues. I will upload the data to some git repo. GPS start time is 1208850775, sweep was 3mins long.
I think the next step here is to noise-budget this curve. At least the DFD noises
To start the noise budgeting, I decided to measure the "DFD noise", which is really the quadrature sum of the following terms:
According to past characterizations of these noises, the ADC noise level, which is expected to be at the level of a few uV/rtHz, is expected to be the dominant noise source.
The measurement was made by disconnecting the NF 1611 free space photodiode from the input to the RF amplifier on the PSL table, and connecting a Marconi (f_carrier = 40 MHz, signal level=-5dBm) instead. The phase tracked output was then monitored, and the resulting digital spectrum is the red curve in Attachment #1. The blue curve is the ASD of fluctuations of the beatnote between the PSL and EX IR beams, as monitored by the DFD system, with the X arm cavity length locked to the PSL frequency via the LSC servo, and the EX green frequency locked to the X arm cavity length by the analog PDH servo.
Assuming the Marconi frquency noise is lower than the ones being budgeted:
Next noises to budget:
Updated the noise budget to include the unsuppressed frequency noise from the EX laser. It does not explain the noise between 10-100 Hz, although the 1-3 Hz noise is close.
Actually, I think the curve that should go on the budget is when the X arm length is locked to the PSL frequency, whereas this is when the X arm is just locally damped. I will update it later tonight.
Update 1010pm: I've uploaded the relevant plot as Attachment #2. Predictably, the unsuppressed frequency noise of the EX laser is now higher, because the MC length is a noisier frequency reference than the arm cavity. But still it is a factor of 10 below the measured ALS noise.
My goal tonight was to lock the PSL frequency to be resonant in the XARM cavity, using the PSL+EX beat as the error signal. I was not successful - mainly, I was plagued by huge BR mode coupling in the error signal, and I could not enable the BR notch filter in the control loop without breaking the lock. Need to think about next steps.
Anyway, now that I have a workable set of settings that gets me close to the ALS lock of the XARM, I expect debugging to proceed faster.
Update 2019 July 23: I looked at the control loop shape today, see Attachment #3. I'm not sure I understand why the "BounceRoll" filter in this filter bank looks like a resonant gain rather than a notch, as it does for the Oplev or SUSPOS loops for example - don't we want to not actuate at these frequencies because the reason the signal exists is because of the imperfect OSEM/magnet positioning? This does not explain the spectrum shown in Attachment #2 however, as that filter was disabled.
The new K6XS mounts I ordered have arrived. I want to install one of them at the Y-end. I can't find a picture of the current layout but it exists as there is a hardcopy affixed to the ETMY chamber door, Steve, can we dig this up and put it in the wiki? In any case, the current beam going into the fiber is the pickoff from the post-SHG harmonic separator. I'd like to change the layout a bit, and use a pickoff before the doubling oven, but looking at the optical table, this seems like a pretty involved task and would probably require large scale optical hardware rearrangement. In any case, the MM of the green beam into the Y-arm is <50%, so I would like to redo that as well. Does anyone know of a measurement of the mode from the Lightwave NPRO that is installed at EY? I think Annalisa is the one who installed this stuff, but I can't find an actual NPRO mode measurement in her elog thread.
Found it: elog4874, elog8436. I updated the laser inventory page to link the lasers in use to the most recent mode measurements I could find on the elog. I guess ideally we should also link the AM/PM response measurements.
SV ETMY optical table layout
as of 3-31-2016
The oplev path was optimized with AR coated lenses and new He/Ne laser Jan 24, 2017
A cable for IP_POS has been disconnected at the LSC rack, 1Y2. Due to it currently no IP_POS signal shows up on the digital side.
It looks like we disconnected the cable together with some unused cables when we were cleaning up the wiring of the LSC rack.
The cable, a shielded flat-cable, is supposed to send DC power to the QPD and send the signals from the QPD to an interface board on the LSC rack.
I will check how it used to be and reconnect it.
A cable for IP_POS has been disconnected at the LSC rack, 1Y2. Due to it currently no IP_POS signal shows up on the digital side.
I found the disconnected cable, but I do not see the interface board at the LSC rack
I found that the ADC channels for IP_ANG had been assigned to a wrong machine.
IP_ANG is supposed to be acquired at c1auxey (east end), but actually it had been at c1auxex (south end).
This is the reason why we couldn't see any signals from IP_ANG.
So I fixed it by editing the db files (i.e. ETMXaux.db and ETMYaux.db). Now it seems working fine.
This mistake obviously came from the X-Y name swapping business. Something else might be still wrong.
I've suspected that the TTs are drifting significantly over the course of the last couple of days, because despite repeated alignment efforts, the AS beam spot has drifted off the center of the camera view. I tried looking at IPPOS, but found that there was no data. Looking at the table, the QPD was turned backwards, and the DAQ cable wasn't connected (neither at the PD end, nor at 1Y2, where instead, a cable labelled "Spare QPD" was plugged in). Fortunately, the beam was making it out of the vacuum. So as to have a quantitative diagnostic, I reconnected the QPD, turned it the right way round, and adjusted the steering onto it such that with the AS spot on the center of the CCD monitor, the beam is also centered on the QPD. The calibration is uncertain, but at least we will be able to see how much the spot drifts on the QPD over some days. Also, we only have 16 Hz readback of this stuff.
I leave it to Chub to take the high-res photo and update the wiki, which was last done in 2012.
Already, in the last ~1 hour, there has been considerable drift - see Attachment #2. The spot, which started at the center of the CCD monitor, has now nearly drifted off the top end. The ITMX and BS Oplev spots have been pretty constant over the same timescale, so it has to be the TTs?
The input matrix of IPPOS were fixed so that the horizaontal motion correctly shows up in X and the vertial is Y.
(what I did)
+ The data base file, QPD.db, were edited.
QPD.db is a part of the c1isxaux slow machine and it determines the input matrix for deriving the X/Y signals from each quadrant element.
+ The previous input matrix was :
X = (SEG1 + SEG4) - (SEG2 + SEG3)
Y = (SEG1 + SEG2) - (SEG3 + SEG4)
+ The new matrix which I set is :
X = (SEG1 + SEG2) - (SEG3 + SEG4)
Y = (SEG1 + SEG4) - (SEG2 + SEG3)
The new matrix is a just swap of the previous X and Y.
+ Then c1isxaux was rebooted by :
+ The I did the burt restore it to this morning.
The channels for IPPOS had been assigned in a wrong way.
I centered IPPOS. I do not find any IPANG beam on the ETMY table, even waving the IR card in the black beam tube.
I took photos of the PZT2 HV supplies with the new camera, but I can't figure out how to get the pictures off the camera. I guess the camera is smarter than I am.
Dataviewer wouldn't launch on pianosa - it seemed to work fine on Donatella though. Rana suggested using the ipcs -q command. The complete fix can be found in this elog. This did the trick, dataviewer runs fine on Pianosa now...
When signals are transmitted between the models running at different rates, no AI or AA filters are automatically applied. We need to fix our models.
This is known, but we just haven't fully groked it yet. We need to look closely at every place we have IPCs between models running at different rates. The sender has no information about receivers, so it can't reasonably do anything to pre-filter the signal on it's own.
So for transmission from:
*sigh* This is one of those things that I meant to take care of months ago, but haven't yet. I agree that it needs doing. It's been on my whiteboard to-do list for a long time now. Bad Jenne for not taking care of it.
I've set up two IPC channels that take the output from the digital frequency counters and send them to the end front-ends (via the RFM model). A summary of the steps I followed:
I've set things up such that we can select either the "PZT IN" or the frequency counter as the input to the slow servo, via means of a EPICS variable called "FC_SWITCH" (so C1:ALS-X_FC_SWITCH or C1:ALS-Y_FC_SWITCH). If this is 0, we use the default "PZT IN" signal, while setting it to 1 will change the input to the slow servo to be the frequency readout from the digital frequency counter. I've not updated the MEDM screens to reflect the two new paths yet, but will do so soon. It also remains to install appropriate filters for the servo path that takes the frequency readout as the input.
Tangentially related to this work: I've modified the FC library block so that it outputs frequency in MHz as opposed to Hz, just for convenience..
I was having trouble centering IPANG using the PZTs, and I suspected something funny was going on at the end. I went down there, and the beam was focused right on the PD, and the spot was very very small. I think this means that when I was trying to center the beam, I was falling into the gap between the pieces of the diode. Also, as Koji pointed out to me the other day, if the PD is at the focal point of the beam, any parallel rays hitting the lens just before the PD will all go to the same place, no matter how the input beam has moved. This means we're not getting as much info out as we'd like.
So. I moved the lens a little bit farther from the PD such that we are just beyond the focal point of the beam. The beam size is now ~1mm on the QPD.
This means, however, that I moved the beam on the QPD such that IPANG is no longer a reference of the input pointing. Ooops. I think this adjustment needed to be done though. Right now, the PZTs are set to where we had them yesterday, when we moved them slightly to center the IPANG QPD, and I've recentered IPANG.
[Jenne, Evan Hall]
Both IPPOS and IPANG beams are (after turning on the input and output PZTs) hitting their QPDs. However IPANG was saturating. We went down to take a look, and we had ~2.8mW incident on the QPD. There was an ND filter sitting unmounted, next to the diode, and an empty fork directly in front of the diode. Since IPPOS also has an ND filter in front, we stuck this ND filter back in. Now we are no longer saturating.
We're not hitting (yet) the center of these 2 PDs, but we're at least hitting the diodes, so it shouldn't be too hard to steer the input PZTs.
Whomever took away this ND filter without elogging it was BAD!!! (Jamie, when we first found IPANG coming out of the vacuum during this vent, we moved some of the mirrors on the out-of-vac table in the IPANG path. Was the ND filter removed at that time? Or has it been out for much longer, and we never noticed because IPANG wasn't coming nicely out of the vacuum / was clipping on the oplev lens?)
[Whomever took away this ND filter without elogging it was BAD!!! (Jamie, when we first found IPANG coming out of the vacuum during this vent, we moved some of the mirrors on the out-of-vac table in the IPANG path. Was the ND filter removed at that time? Or has it been out for much longer, and we never noticed because IPANG wasn't coming nicely out of the vacuum / was clipping on the oplev lens?)
I do not remember removing anything from that setup. We just moved some mirrors and lenses around
IP-ANG is coming out of ETMY without clipping. The beam is very high on the pick off mirror at the end table but it is still missing the qpd .
Initial pointing or IP-ANG is a pointing monitor of the MC. This beam is launched after the second pzt steering mirror.
IP-ANG is missing the pick up mirror by a few inches at ETMYchamber
1000 days plot show last appearance in Feb 2010
Pointing stability of 4 days. Initial pointing does not go through suspended optics. It is launched right after the Piezo Jena steering mirrors in the BS chamber.
IP-ANG on epics screen is C1:ASC-IBQPD_X and Y in dataviewer were recentered. This beam is clipping a bit in ETMX chamber pick off mirror.
IP-POS pick off is in the BS chamber and it's qpd on the BS_ISCT This beam is also clipping just a little bit. This is easy to fix. We'll have to remove an iris from the BS optical levers table.
note: arms were not locked when I recentered
IP-ANG clipping can be traced back to our last vent of Aug. 18, 2008 See elog entry #845
This was an after earth quake - sus repair vent
After locking the arms (after the MC alignment work), Manasa and I aligned IP POS, IP ANG, and both end transmission QPDs.
We noticed that IP ANG is clipping in yaw as it comes onto the end table. It looks to me like it's clipping on the edge of the plastic box's aperture, but I can't guarantee that it's not also clipping elsewhere.
Its back in and re-centered. Our next move on IPPOS should be to replace its steering mirror with something bigger and more rigid.
20K -> 3.65 K (R6, R20, R42, R31) (unused)
20K -> 3.65 K (R7, R21, R32, R43, R11, R24, R35, R46)
If you look in the schematic (D990272), you see that its an AD797 transimpedance stage with a couple of LT1125 stages set to give some switchable gain. It looks like some of these
switches are on and some are not, but I am not sure where it would be controlled from. I've attached a snapshot of one quadrant of the schematic below.
The schematic shows the switches in the so-called 'normally closed' configuration. This is what the switches do with zero volts applied to the control inputs. As the schematic also shows,
just disconnecting the 'switch' inputs cause the switch's control inputs to go high (normally open configuration, i.e. pins 2-3 connected, pin4 open). For the record, the default positions of the IPPOS switches are:
** EDIT (Nov 2, 2009): I forgot to attach the before and after images; here they are:
I tried to compare the IP_POS time series with the IPANG and MC_TRANS but was foiled at first:
1) The IPANG scan rate was set to 0.5 second, so it doesn't resolve the pendulum motions well. Fixed in the .db file.
2) Someone had used a Windows/DOS editor to edit the .db file and it was filled with "^M" characters. I have removed them all using this command: tr -d "\r" <ETMXaux.db > new.db
3) The MC_TRANS P/Y channels were on the MC Lock screen but had never been added to the DAQ. Remember, if there's a useful readback on an EPICS screen. its not necessarily in the frames unless you add it to the C0EDCU file. I have done that now and restarted the fb daqd. Channels now exist.
4) Changed the PREC of the IPPOS channels to 3 from 2.
5) changed the sign for the IBQPD (aka IPANG) so that bigger signal is positive on the EPICS screen.
IPPOS is back. A cable had been disconnected at the 1Y2 rack. So I put it back to place.
The cartoon below shows the current wiring diagram. I think this configuration is exactly the same as it it used to be.
+ Fixing IPPOS (volunteers)
Jamie went out to look at IP POS, and the beam was *way* off. Even though our alignment is still rough, we're kind of close right now, so Jamie put the beam back on the QPD, but we need to recenter IPPOS after we get good alignment.
The MC is happy (but only for this tiny snapshot in time and most probably will go dysfunctional again as it has been for several months, as of this writing)
I shutdown the +/-15V and the +/-24V sorensons on the IOO rack to connect the FOL RF PDs to the rack power supply.
They were turned back ON after the work. PMC and MC were relocked.
We ran power cables and sma cables for the FOL fiber module from the PSL table to the IOO rack.
The RF amplifier panel on the IOO rack (Attachment 1) will be used to also hold the RF amplfiers for the frequency counters. The amplifiers mounted on it right now are getting +15 (orange wire) and GND (black wire) from the rack power supply (Attachment 2).
Proposed plan to install RF amplifiers:
1. Disconnect the D sub connector that powers the amplifiers and pull out the panel. The rack power supplies will NOT be shut down for this.
2. Mount the RF amplifiers with bypass capacitors. There will be 4 amplifiers ZFL-500LN mounted on the same panel (2 for each frequency counter).
3. While putting back the panel on the IOO rack, we will need to shut down the +15V and -15V sources to connect the amplifiers to the rack power supply.
I will do this over this weekend so that we dont lose any locking time. If anybody has any concerns, let me know
The power supply to the ADC box on the IOO rack (that reads the beat I & Q signals) was pulled out because it did not run through any fuse and was connected directly to the power supply.
There were already connections running from the +/-5 V power supply. They were powering the mode cleaner demod board rack. In order to remove the ADC power connectors from the power supply, I notified Jenne in the control room because turning off the power supply would affect the MC. I switched off the +/-5V power supplies at the same time. The ADC power connectors were removed. The +/-5V power supplies were then turned ON again at the same time. Jenne relocked the MC after this.
I have still not connected the ADC to the fuse rack power supply because this requires the +/-5V power supplies to be turned OFF again in order to pull out new connections from the fuse rack and I need to make a new ADC power connector with thicker wires.
I switched OFF the +/-5V power supplies on the IOO rack to hook up the ADC power connectors through 250mA fuses to +/-5V. Since these power supplies were powering the MC demod boards, MC remained unlocked during the process. I turned the power supplies back ON and MC relocked itself after this.
The IMC has not been behaving well since this morning and totally not happy when Q was finishing his measurements. The WFS servo had large offsets in pitch. Looking back at the trend and using ezcaservo to restore the suspensions did not help.
I realigned the IMC and brought TRANS SUM to ~18000 and MCREFL to < 0.5. The spot positions are not very good; nearly 2 mm off in pitch on MC1 and MC3. But after the alignment of MC, the WFS servo offsets were below +/-20.
The MC has been locked stably with WFS servo ON for the last few hours.
P.S. I did not touch the WFS pointing or reset the WFS offsets.
MC remained locked with WFS enabled all through last night and this morning. Koji dropped by and looked at the MC. The MC WFS servo, though stable, was at the edge of becoming unstable. This was because I did not touch the WFS pointing on the QPDs yesterday after realigning. So I recentered the WFS, reset the WFS filterbank offsets and reenabled the servo.
I measured the spot positions on MC mirrors for reference.
Spot positions in mm (MC1,2,3 pit MC1,2,3 yaw): [1.405767579680834, 0.79369009503571208, 1.3220430681427462, -1.2937873599406551, -1.1704264340968924, -1.2518046122798692]
Morning seconds without adjustment.
C1:IOO-QPD_ANG_VERT beam movement in 1 degree C temp change in 3 hrs
This moring I centered the IOO Angle QPD. The IOO Pos QPD was not centered. The existing layout does not allow the beam centering of the Pos qpd without misaligning the MC
input. We have to add an aditional steering mirror. I will do that tomorrow morning.
I added the steering mirror for Pos and centered both qpds
In order to activate the slow actuator servo for the MC locking,
the threshold level for this servo (C1:PSL-FSS_LOCKEDLEVEL) was changed from 10000 to 700.
Now the servo started to move the PZT fast out to be controlled to 5V.
after re-aligning the beam into the PMC, I touched up the steering mirros into the IOO QPDs so that the beams are now centered again. Please don't adjust these references without prior authorization and training.
This plot shows the 10-minute trends for these QPDs over the last 400 days.
Looking at the summary page trends from today, you can see that the MC transmission is pretty flat after I zeroed the MCWFS offsets. In addition, the transmission from both arms is also flat, indicating that our previous observation of long term drift in the Y arm transmission probably had more to do with bad Y-arm initial alignment than unbalanced ETMY coil-magnets.
Much like checking the N2 pressure, amount of coffee beans, frames backups, etc. we should put MC WFS offset adjustment into our periodic checklist. Would be good to have a reminder system that pings us to check these items and wait for confirmation that we have done so.
Here is the suggested layout of the MC health check web page layout. I will update the Omnigraffle file as people comment and suggest changes. If you want the file let me know.
The front end timing was not working properly for 2 of the IO chassis. They were not being synced to the 1 PPS signal.
This prevented the use of RFM for communication between front ends because time stamps on the transmitted data did not match the cycle on the receiving machine.
We took one of the incorrectly working chassis over to Downs. Rolf said he would take a look at it tomorrow morning.
Joe will be going over tomorrow morning to talk with Rolf and see what needs to be done to fix it.
As per Steve's request, I've checked the alignment of the IMC and the arms. These three cavities are locked and aligned.