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ID Date Author Typeup Category Subject
  10564   Fri Oct 3 13:03:05 2014 ericqUpdateIOOIMC WFS measurements

Yesterday, Koji and I measured the transfer function of pitch and yaw excitations of each MC mirror, directly to each quadrant of each WFS QPD. 

When I last touched the WFS settings, I only used MC2 excitations to set the individual quadrant demodulation phases, but Koji pointed out that this could be incomplete, since motion of the curved MC2 mirror is qualitatively different than motion of the flat 1&3. 

We set up a DTT file with twenty TFs (the excitation to I & Q of each WFS quadrant, and the MC2 trans quadrants), and then used some perl find and replace magic to create an xml file for each excitation. These are the files called by the measurement script Koji wrote. 

I then wrote a MATLAB script that uses the magical new dttData function Koji and Nic have created, to extract the TF data at the excitation frequency, and build up the sensing elements. I broke the measurements down by detector and excitation coordinate (pitch or yaw).

The amplitudes of the sensing elements in the following plots are normalized to the single largest response of any of the QPD's quadrants to an excitation in the given coordinate, the angles are unchanged. From this, we should be able to read off the proper digital demodulation angles for each segment, confirm the signs of their combinations for pitch and yaw, and construct the sensing matrix elements of the properly rotated signals. 

WFS1PIT.pdfWFS2PIT.pdf

WFS1YAW.pdfWFS2YAW.pdf

The axes of each quadrant look consistent across mirrors, which is good, as it nails down the proper demod angle. 

The xml files and matlab script used to generate these plots is attached. (It requires the dttData functions however, which are in the svn (and the dttData functions require a MATLAB newer than 2012b))

Attachment 5: analyzeWfs.zip
  10565   Sun Oct 5 10:09:49 2014 ranaUpdateIOOIMC WFS measurements

It seems clever, but I wonder why use DTT and command line perl, instead of using the FE lockins or just demod the offline data or all of the other sensing matrix scripts made for the LSC (at 40m) or ASC (at LLO) ?

  10566   Sun Oct 5 23:43:08 2014 KojiUpdateIOOIMC WFS measurements

There are several non scientific reasons.

  10567   Mon Oct 6 10:04:58 2014 manasaUpdateGeneralUnexpected power shutdown

We had a unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

  10568   Mon Oct 6 10:23:43 2014 SteveUpdateVACUnexpected power shutdown

Quote:

We had an unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

PSL Innolight laser and the 3 units of IFO air conditions turned on.

The vacuum system reaction to losing power: V1 closed and Maglev shut down. Maglev is running on 220VAC so it is not connected to VAC-UPS.  V1 interlock was triggered by Maglev "failure" message.

Maglev was reset and started. After Chiara was turned on manually I could bring up the vac control screen through Nodus and opened V1

"Vacuum Normal" valve configuration was recovered instantly.

 

Chiara needs UPS 

It is arriving Thursday

  10569   Mon Oct 6 10:28:18 2014 manasaUpdateGeneralUnexpected power shutdown

Quote:

We had a unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

 The last time we had a power failure IFO recovery elog

  10570   Mon Oct 6 11:09:52 2014 JenneUpdateGeneralUnexpected power shutdown: slow computers

As per other slow computers, which Chris figured out in elog 10189, I added all the rest of the slow computers to Chiara's /etc/hosts file, so that they would come up when Manasa went and keyed the crates. 

Computers that were already there:

  • c1auxex
  • c1psl
  • c1iscaux

Computers that I added today:

  • c1susaux
  • c1auxey
  • c1iscaux2
  • c1pem1
  • c1aux
  • c1iool0
  • c1vac1

Manasa keyed all of these crates *except* for the vac computer, since Steve said that the vacuum system is up and running fine.

  10571   Mon Oct 6 17:04:51 2014 ericqUpdateGeneralUnexpected power shutdown

I brought back the PMC, MC and Arms.

PMC:

  • Same as when we replaced the busted sorensen, the kepco regulators in 1X1 (which power the FSS HV amp, PMC PZT and WFS) needed to be brought back up in the proper order. (Middle two are  + and - for the FSS, need to be rolled up in unison). Also the same as that occasion, sticky sliders prevented the full voltage range on the PMC PZT from being accessible. I touched every button on the PMC and FSS screens, which seemed to fix it. 
  • I then realigned the PMC to ~0.80 transmission

MC:

  • Needed to do some hand alignment to get a lock
  • Measured spot positions, they were all under 2mm
  • Despite centering the beams on the WFS and setting the offsets, WFS would not turn on successfully
  • Also, the autolocker on megatron isn't doing anything but blinking
  • Also also, MC2 is exhibiting some intermittent alignment wandering. The SUSDOF traces look like flat ramps lasting a few minutes. 

Arms:

  • No green was evident anywhere, but it didn't take to much alignment tweaking to get IR flashes
  • No signals were evident on RFPDs, confirmed light on PDs and power to demod boards. 
  • Turned out the 11MHz Marconi was not doing anything, and needed to be reset to the modulation frequency in ELOG 10314 (which reminds me that I need to update the sticker on the marconi)
  • Locked arms, ASS'ed, oplev spots were acceptable. 

 

  10572   Mon Oct 6 17:36:17 2014 ericqUpdateGeneralUnexpected power shutdown

The autolocker is now working, but I didn't change anything to make it so. I was just putting in some echo statements, to see where it was getting hung up, and it started working... This isn't the first time I've had this experience. 

It turns out IOO had a bad BURT restore. I restored from 5AM this morning, the WFS are ok now. 

  10573   Mon Oct 6 18:15:12 2014 manasaUpdateGeneralUnexpected power shutdown: end green alignment

After Q brought back the IR, I went to check the green situation.

1. The end lasers had to be turned ON. 
2. The heaters for the doubler crystals had to be enabled. The heaters are at the set values.
3. The X arm PZTs for the steering mirrors had to be powered up (Set voltage 100V and current 6.7mA)
4. I aligned the green to the already IR-aligned arms.

Green PSL alignment has to be done after Q finishes his work on the MC WFS.

  10574   Tue Oct 7 00:18:12 2014 JenneUpdateLSCYgreen PSL alignment, ETMX strain relief

No exciting progress today.  I did PSL green alignment for the Yarm, although I now think that the Xarm green needs realigning too.

Also, I was foiled for a while by ETMX jumping around.  I think it's because the adapter board on the Xend rack didn't have any strain relief.  So, I zip tied the heavy cable in a few places so that it's no longer pulling on the connector.  Hopefully we won't see ETMX misbehaving as often now, so we won't have to go squish cables as often.

  10575   Tue Oct 7 10:09:07 2014 manasaUpdateGeneralChiara not responding

Chiara doesn't seem to be responding and I guess something happened 7 hrs ago.

I tried to hook up chiara to a monitor to reboot or atleast look for error messages; but it is not even detecting the external monitor (Tried changing monitors and vga cables; still see nothing).

I tried to ssh into it and only received errors :
NFS lookup failed for server XXX.XXX.XXX.XXX : error 5 (RPC: Timed out)
ssh: chiara: host/servname not known

Steve had the vacuum checked and everything seems fine with the status of the vacuum system atleast.

  10576   Tue Oct 7 16:17:15 2014 SteveUpdateGeneralreason for 8 sec power outage

Quote:

We had a unexpected power shutdown for 5 sec at ~ 9:15 AM.

Chiara had to be powered up and am in the process of getting everything else back up again.

Steve checked the vacuum and everything looks fine with the vacuum system.

 

There was an equipment malfunction in one of Pasadena's substation that caused the outage. After about an 8 second delay, back up circuits restored power. This affected about 1/2 of the campus.

Mike 

-----Original Message-----
From: Steve Vass [mailto:steve@ligo.caltech.edu] 
Sent: Tuesday, October 07, 2014 2:18 PM
To: Anchondo, Michael
Subject: 5s

Hi Mike,

Can you tell me about yesterday's power outage?

Thanks, Steve
  10577   Tue Oct 7 16:19:50 2014 ericqUpdateGeneralChiara not responding

We're back! It was entirely my fault.

Some months ago I wrote a script that chiara calls every night, that rsyncs its hard drive to an external drive. With the power outage yesterday, the external drive didn't automatically mount, and thus chiara tried to rsync its disk to the mount point, which was at the time just a local folder, which made it go splat. 

I'm fixing the backup script to only run if the destination of the rsync job is not a local volume. 

  10578   Tue Oct 7 16:41:12 2014 JenneUpdateGeneralChiara not responding

I put a little script into ...../scripts/Admin that will check the fullness of Chiara's disk.  We only have the mailx program installed on Nodus, so for now it runs on Nodus and sends and email when the chiara disk that nodus mounts is more than 97% full.

  10579   Tue Oct 7 16:55:16 2014 SteveUpdateVACUnexpected sweaty valves

 Pump  spool valves V5, V4, V3 sweating a lot. VM3 and VC2 not so much.

They are VAT valves F28-62887-03, 11, 14 and so on ~15-16 years old.

 I'm speculating that some plastic is aging-braking down at the atmospheric-pneumatic side of valves.
The vacuum side is not effected, according to vacuum pressure readings.

May be some condensation from the small turbos? No

I'm looking for an identical valve to examine, but I can not find one.

We are using industrial grade 99.96% Nitrogen to actuate these valves.

Valves are not effected are  dry: VA6, V6, V7 and all annuloses.

 

Attachment 1: sweatyV5.jpg
sweatyV5.jpg
Attachment 2: sweatyV5f.jpg
sweatyV5f.jpg
  10580   Tue Oct 7 19:40:58 2014 ericqUpdateLSCCM, REFL11 Wiring

I've changed the LSC rack wiring a little bit, to give us some flexibility when it comes to REFL11. 

Previous, the REFL11 demod I output was fed straight to the CM servo board, and the slow CM board output was hooked up to the REFL11I ADC channel. Thus, it wasn't really practical to ever even look at sensing angles in REFL11, since the I and Q inputs were subject to different signal paths/gains. (Also, doing LSC offsets would do wonky things to refl11 depending on the state of the switches on the CM board screen.)

Thus, I've hooked up the CM board slow output into the the previously existing, aptly named, CM_SLOW channel. The REFL11 demod board I output is split to IN1 of the CM board, and the REFL11 I ADC channel. 

So, there is no longer hidden behavior in behind the REFL11 input filters, channels are what they claim to be, and the CM board output is just as easily accessible to the LSC filters as before. 

  10581   Wed Oct 8 03:20:46 2014 JenneUpdateLSCDo we need AO for acquisition?

As part of trying to determine whether we require the AO path for lock acquisition, or if we can survive on just digital loops, I looked at the noise suppression that we can get with a digital loop.

I took a spectrum of POX, and calibrated it using a line driving ETMX to match the ALSX_FINE_PHASE_OUT_HZ channel, and then I converted green Hz to meters. 

I then undid the LSC loop that was engaged at the time (XARM FMs 1,2,3,4,5,8 and the pendulum plant), to infer the free running arm motion. 

I also applied the ALS filters (CARM FMs 1,2,3,5,6) and the pendulum plant to the free running noise to infer what we expect we could do with the current digital CARM filters assuming we were not sensor noise limited.

In the figure, we see that the free running arm displacement is inferred to be about 0.4 micrometers RMS.  The in-loop POX signal is 0.4 picometers RMS, which (although it's in-loop, so we're not really that quiet) is already better than 1/10th the coupled cavity linewidth.  Also, the CARM filters that we use for the ALS lock, and also the sqrtInvTrans lock are able to get us down to about 1 pm RMS, although that is not including sensor noise issues. 

EstimatedNoisePerformance.png

For reference, here are the open loop gains for the LSC filters+pendulum and ALS filters+pendulum that we're currently using.  The overall gain of these loops have been set so the UGF is 150Hz.

 BodeLSCvsALS.png

It seems to me that as long as our sensors are good enough, we should be able to keep the arm motion down to less than 1/10th or 1/20th the coupled cavity linewidth with only the digital system.  So, we should think about working on that rather than focusing on engaging the AO path for a while.

Attachment 3: CARMnoise_7Oct2014.zip
  10582   Wed Oct 8 03:37:44 2014 ericqUpdateLSCPRFPMI, other sign of CARM offset

 [ericq, Jenne]

We attempted some of the same old CARM offset reduction tonight, but from the other direction. (We have no direct knowledge of which is the spring and which is the anti-spring side)

We we able to get to, and sit at, arm powers on the order of 5. Really, we kind of wanted just to push things to try and inform our current ideas of what our limiting factor is, so as to appropriately expend our efforts. 

Candidates include:

  • ALS noise causing excess DARM motion
    • Means we need to DRMI to widen DARM linewidth, avoid sign flip in AS55, IR lock DARM sooner
  • Intolerable sensor noise makes CARM wander too much, changing our plant more than our loops can handle
    • We should work on having live calibrated CARM spectra during lock attempts, to compare with Jenne's noise estimates, and see where/how/why we exceed it. 
  • detuned CARM pole causes loop instability
    • Maybe some sort of notching can get us by
    • AO path could extend bandwidth, getting the pole into the control band 
  • SqrtInv signals losing low frequency sensitivity due to radiation pressure, or DC sensitivity due to transmission curve flattening out
    • Bring in AO path for supplementary bandwidth, which lets us turn up loop gain / engage big boosts
    • Or, switch to REFLDC in digital land, which is nontrivial, due to different optical plant shapes.

We took many digital CARM OLTFs at different offsets; it never really looked like a burgeoning pole was about to make things unstable. The low frequency OLTF data had bad SNR, so it wasn't clear if we were losing gain there. We weren't at arm powers where we would expect the DC transmission curve to flatten out yet, from simulations (which is above a few tens).

My impression from at least our last lock loss was a DARM excursion. However, using the DRMI won't get rid of the second two points.

 

  10583   Wed Oct 8 03:49:42 2014 JenneUpdateLSCPRFPMI, other sign of CARM offset

Other thoughts from talking with Rana earlier:

  • Is it possible to suppress CARM motion enough that we can use just a digital loop?  Can we do without the AO path?  What would said digital loop have to look like?
  • Q points out that there is a zero in the relative transfer function between CARM to transmission, and CARM to REFLDC.  Is that zero invertible?
  • We should look at some limits, like saturation limits.  How much will we need to actuate?
  • Rana is looking at making a more detailed CARM loop model in simulink to see if we can stay stable throughout our CARM offset reduction journey.

Also, Q and I squished on the suspension connectors earlier tonight.  MC2 was going wonky, which we feared might be because we were in that area working on Chiara earlier.  Then, after squishing the MC connectors, the PRM started misbehaving, so we went and gave all the corner suspension connectors another squish.  No suspension glitching problems since then.

  10584   Wed Oct 8 08:46:57 2014 SteveUpdateVACVAT valves actuator lubricant

Quote:

 Pump  spool valves V5, V4, V3 sweating a lot. VM3 and VC2 not so much.

They are VAT valves F28-62887-03, 11, 14 and so on ~15-16 years old.

 I'm speculating that some plastic is aging-braking down at the atmospheric-pneumatic side of valves.
The vacuum side is not effected, according to vacuum pressure readings.

May be some condensation from the small turbos? No

I'm looking for an identical valve to examine, but I can not find one.

We are using industrial grade 99.96% Nitrogen to actuate these valves.

Valves are not effected are  dry: VA6, V6, V7 and all annuloses.

 

VAT's answer:

Yes, our engineers are aware of this issue.  They say:

The pneumatic actuator needs lubricant as the O-ring (Viton) slides in the cylinder. Without grease the O-ring would be abraded and leaking after only a relatively few cycles.  The lubricant used in our pneumatic actuators is an emulsion of oil and Teflon flakes.   Vibration, many cycles and sometimes high temperature lead to the separation of the oil and Teflon.   That is apparently the issue you are seeing.

VAT is and has been testing and qualifying new lubricants, and this is one of the factors we are always looking to improve.  The formula we used 15 years ago in these valves seems to have performed reasonable  well.  Our formula today should perform even better.

We realize this explanation does not help you with these existing valves, but 15 years of service is not too bad is it? 

Steve -NOTE:bonnet seal is metal so there is no way this oil can get into our vacuum ( only if the bellow leaks )

  10585   Wed Oct 8 15:31:31 2014 JenneUpdateCDSComputer status

After the Great Computer Meltdown of 2014, we forgot about poor c0rga, which is why the RGA hasn't been recording scans for the past several months (as Steve noted in elog 10548).

Q helped me remember how to fix it.  We added 3 lines to its /etc/fstab file, so that it knows to mount from Chiara and not Linux1.  We changed the resolv.conf file, and Q made some simlinks.

Steve and I ran ..../scripts/RGA/RGAset.py on c0rga to setup the RGA's settings after the power outage, and we're checking to make sure that the RGA will run right now, then we'll set it back to the usual daily 4am run via cron.

EDIT, JCD:  Ran ..../scripts/RGA/RGAlogger.py, saw that it works and logs data again.  Also, c0rga had a slightly off time, so I ran sudo ntpdate -b -s -u pool.ntp.org, and that fixed it.

Quote:

 

In all of the fstabs, we're using chiara's IP instead of name, so that if the nameserver part isn't working, we can still get the NFS mounts.

On control room computers, we mount the NFS through /etc/fstab having lines like:

192.168.113.104:/home/cds /cvs/cds nfs rw,bg 0 0
fb:/frames /frames nfs ro,bg 0 0

Then, things like /cvs/cds/foo are locally symlinked to /opt/foo

For the diskless machines, we edited the files in /diskless/root. On FB, /diskless/root/etc/fstab becomes

master:/diskless/root                   /         nfs     sync,hard,intr,rw,nolock,rsize=8192,wsize=8192    0 0
master:/usr                             /usr      nfs     sync,hard,intr,ro,nolock,rsize=8192,wsize=8192    0 0
master:/home                            /home     nfs     sync,hard,intr,rw,nolock,rsize=8192,wsize=8192    0 0
none                                    /proc     proc    defaults          0 0
none                                    /var/log        tmpfs   size=100m,rw    0 0
none                                    /var/lib/init.d tmpfs   size=100m,rw    0 0
none                                    /dev/pts        devpts  rw,nosuid,noexec,relatime,gid=5,mode=620        0 0
none                                    /sys            sysfs   defaults        0 0
master:/opt                             /opt      nfs    async,hard,intr,rw,nolock  0 0
192.168.113.104:/home/cds/rtcds         /opt/rtcds      nfs     nolock  0 0
192.168.113.104:/home/cds/rtapps        /opt/rtapps     nfs     nolock  0 0

("master" is defined in /diskless/root/etc/hosts to be 192.168.113.202, which is fb's IP)

and /diskless/root/etc/resolv.conf becomes:

search martian

nameserver 192.168.113.104 #Chiara

 

 

 

  10586   Thu Oct 9 10:52:37 2014 manasaUpdateGeneralPower outage II & recovery

Post 30-40min unexpected power outage this morning, Steve checked the status of the vacuum and I powered up Chiara.

I brought back the FE machines and keyed all the crates to bring back the slow machines but for the vac computers.

c1vac1 is not responding as of now. All other computers have come back and are alive.

  10587   Thu Oct 9 11:56:35 2014 SteveUpdateVACPower outage II & recovery

Quote:

Post 30-40min unexpected power outage this morning, Steve checked the status of the vacuum and I powered up Chiara.

I brought back the FE machines and keyed all the crates to bring back the slow machines but for the vac computers.

c1vac1 is not responding as of now. All other computers have come back and are alive.

 

 IFO vacuum, air condition and PMC HV are still down. PSL out put beam is blocked on the table.

  10588   Thu Oct 9 13:29:14 2014 JenneUpdatePSLPower outage II & recovery

Quote:

 

 IFO vacuum, air condition and PMC HV are still down. PSL out put beam is blocked on the table.

 PMC is fine.  There are sliders in the Phase Shifter screen (accessible from the PMC screen) that also needed touching. 

PSL shutter is still closed until Steve is happy with the vacuum system - I guess we don't want to let high power in, in case we come all the way up to atmosphere and particulates somehow get in and get fried on the mirrors. 

  10589   Thu Oct 9 16:31:53 2014 ericqUpdateLSCCARM W/N TFs

In my previous simulation results, I've always plotted W/m, which isn't exactly straightforward. We often think about the displacement that a given mirror actuator output will induce, but when we're locking the full IFO, radiation pressure effects modify the mechanical response depending on the current detuning, making the meaning of W/m transfer functions a little fuzzy.

So, I've redone my MIST simulations to report Watts of signal response due to actual actuator newtons, which is what we actually control with the digital system. Note, however, that these Watts are those that would be sensed by a detector directly at the given port, and doesn't take into account the power reduction from in-air beamsplitters, etc.

As an example, here are the SqrtInv and REFLDC CARM TFs for the anti-spring case:

carm2SQRTinv.pdfcarm2REFLDC.pdf

 

The units of the SqrtInv plot are maybe a little weird, these TFs are the exact shape of the TRX W/N TFs with the DC value adjusted by the ratio of the DC sweep derivatives of TRX and SqrtInv. 

All of the results live in /svn/trunk/modeling/PRFPMI_radpressure/

 

  10590   Thu Oct 9 17:33:28 2014 SteveUpdateVACPower outage II & recovery

Quote:

Quote:

Post 30-40min unexpected power outage this morning, Steve checked the status of the vacuum and I powered up Chiara.

I brought back the FE machines and keyed all the crates to bring back the slow machines but for the vac computers.

c1vac1 is not responding as of now. All other computers have come back and are alive.

 

 IFO vacuum, air condition and PMC HV are still down. PSL out put beam is blocked on the table.

 We are pumping again. This is a temporary configuration. The annuloses are at atmosphere. The reset reboot of c1Vac1 and 2 opened everything except the valves that were disconnected.

TP2 lost it's vent solenoid power supply and dry pump during the power outage.

They were replaced but the new small turbo controller is not set up as the old TP2 was so it does not allow V4 to open. 

Tomorrow I will swap back the old controller,  pump down the annuloses and close off the ion pumps.

I removed the beam block from the PSL table and opened the shutter. CC4 has the real pressure 2e-5 Torr  

CC1 is not real.

Attachment 1: pumpingAgain.png
pumpingAgain.png
  10591   Thu Oct 9 18:30:59 2014 JenneUpdateLSCCARM W/N TFs

Okay, here (finally) is the optickle version.

I have the antispring case, starting at 501pm and going roughly every 10pm down to 1pm.  I also have the spring case, starting at -501pm and going down every 10pm to roughly -113pm.  Rossa crashed partway through the calculation, which is why it's not all the way.

In the .zip is a .mat file called PDs_vs_CARMoffset_WattsPerNewton.mat, which has (a) a list of the 50 CARM offsets, (b) a frequency vector, and (c) several transfer function arrays.  The transfer function arrays are supposed to be intuitively named, eg. REFLDC_antispring. 

In the .zip file are also the original .mat files that are a result of the tickle calculations, as well as a .m file for loading them and making the plots, etc.  For anyone who is trying to re-create the transfer function variables, I by-hand saved the variable called PD_WperN to the names like REFLDC_antispring.  Just kidding.  Those original mat files are over 100Mb each, and that's just crazy.  Anyhow, I think the .zip has everything needed to use the data from these plots.

Anyhow.  Here are plots of what are in the various transfer function arrays:

 TRX_antispring.pngTRX_spring.png

REFLDC_antispring.pngREFLDC_spring.png

REFL11I_antispring.pngREFL11I_spring.png

Attachment 6: ForElog.zip
  10592   Thu Oct 9 19:14:04 2014 ericqUpdateGeneralPower outage II & recovery

I touched up the PMC alignment. 

While bringing back the MC, I realized IOO got a really old BURT restore again... Restored from midnight last night. WFS still working.

Now aligning IFO for tonight's work

  10593   Fri Oct 10 00:20:37 2014 ranaUpdateLSCCARM W/N TFs

 

 Assuming that these Watts/Newtons TFs are correct, I've modeled the resulting open loop gain for CARM. The goal is to design a loop that is stable under a wide range of offsets and also has enough low frequency gain.

The attached PDF shows this. I used a CARM OLG Simulink model:

carm40.png

I've replaced the 'armTF' block with a digital gain of zero. After measuring the open loop gain of all but this piece, I multiply that 'OLG' with the W/N that Jenne extracted from Optickle for CARM->TR (not sqrtInv)

I plot the resulting estimate of the actual OLG in the following plot. Since the CARM-RSE peak is moving down, we use the LP filter that Den installed for us several months ago. To account for the radiation pressure spring, we use some low frequency boosts but not the crazy FM4 filter.

As you can see, the loop is stable from 500 to 200 pm, but then goes unstable around 110 pm. I expect that we will want to do some fancy shaping there or switch from TRX+TRY into something else.

This assumes we have filters 0, 1, 3, 5, and 7 on in the CARM filter bank - still need to add the digital AA/AI to make the loop phase lag a little more accruate, but I think this is looking promising.

 

Attachment 2: carm.pdf
carm.pdf
  10594   Fri Oct 10 03:05:09 2014 ericqUpdateLSCWhich side of optical spring are we on?

 I made some measurements to try and see if any difference could be seen with different CARM offset signs. 

Specifically, at various offsets, I used a spare DAC channel to drive IN1 of the CM board, as an "AO Exciter." I used CM_SLOW to monitor the signal that was actually on the board. I used the CARM_IN1 error signal to see how the optical plant responded to the AO excitation. Rather than a swept sine, I used a noise injection kind of TF measurement. 

Here are plots of CARM_IN1 / CM_SLOW at different CARM FM offsets; I chose to plot this in an attempt to divide out some of the common things like AA and delays and make the detuned CARM pole more evident). The offsets chosen correspond roughly to powers of 2, 2.5, and 3. I tried to go higher than that, but didn't remain locked for long enough to measure the TF. 

comparison.pdf

By eye, I don't see much of a difference. We can zpk fit the data, and see what happens. 

 

  10595   Fri Oct 10 03:25:11 2014 JenneUpdateLSCWhich side of optical spring are we on (simulation)

I have a simulated version of the differences that we expect to see between the 2 different sides of the CARM resonance.  The point is that we can try to compare these results with Q's measured results (elog 10594) to see if we know if we are on the spring or antispring side.


I calculated the same transfer functions vs CARM offset again, although tonight I do it in steps of 20pm because I was getting bored of waiting forever.  Anyhow, this is important because my previous post (elog 10591) didn't have spring side calculations all the way down to 1pm.

This is similarly true for that elog 10591, but here are some notes on how I am currently getting the W/N units out of Optickle.  First of all, I am still using old Optickle1.  I don't know if there are significant units ramifications for that, but just in case I'll write it down.  Nic tells me that to get [W/N] out of Optickle1, I need to multiply sigAC (units of [W/m]) by my simple pendulum (units of [m/N]).  Both of these "meters" in the last sentence are "mevans meters", which are the meters you would get per actuation if radiation pressure didn't exist.  So, I guess they're supposed to cancel out?  I need to camp out in Nic's office until I figure this out and get it untangled in my head.

Plots of transfer functions for both sides of CARM resonance (same as prev. elog), as well as the ratio between the spring and antispring transfer functions at each CARM offset:

TFs_TRX_vsCARMoffset_PRFPMI_antispring.pngTFs_TRX_vsCARMoffset_PRFPMI_spring.pngTFs_TRX_vsCARMoffset_PRFPMI_differentials.png

 

TFs_REFLDC_vsCARMoffset_PRFPMI_antispring.pngTFs_REFLDC_vsCARMoffset_PRFPMI_spring.pngTFs_REFLDC_vsCARMoffset_PRFPMI_differentials.png

TFs_REFL11I_vsCARMoffset_PRFPMI_antispring.pngTFs_REFL11I_vsCARMoffset_PRFPMI_spring.pngTFs_REFL11_vsCARMoffset_PRFPMI_differentials.png

The take-away message from the 3rd column is that other than a sign flip, we don't expect to see very much difference between the 2 sides of the CARM resonance, particularly above a few hundred Hz.  (Note that we do not see the sign flip in Q's measurements because he is looking at CARM_IN1, which is after the input matrix, and the input matrix elements have opposite signs between the signs of the CARM offsets.  So, the sign flip between spring and antispring around the UGF is implied in the measurements, just not explicit).

Also, something that Rana pointed out to me, and I still don't know why it's true:  The antispring transfer functions (at least for the transmission) don't have all the phase features that we expect to see based on their magnitudes.  If you look at the TRX antispring plot, blue trace (which is about 500pm from resonance), you'll see that the magnitude starts flat at DC, has some slope in an intermediate region, and then at high frequencies has 1/f^2.  However, the phase seems to not know about this intermediate region, and magically waits until the 1kHz resonance to flip the full 180 degrees. 

Attachment 10: ForElog_9Oct2014.zip
  10596   Fri Oct 10 14:27:44 2014 SteveUpdateCDSc1Vac1 and c1vac2 reboot was a failure

Quote:

Quote:

 

 I have brought back c1auxex and c1auxey.  Hopefully this elog will have some more details to add to Rana's elog 10015, so that in the end, we have the whole process documented.

The old Dell computer was already in a Minicom session, so I didn't have to start that up - hopefully it's just as easy as opening the program.

I plugged the DB9-RJ45 cable into the top of the RJ45 jacks on the computers.  Since the aux end station computers hadn't had their bootChanges done yet, the prompt was "VxWorks Boot" (or something like that).  For a computer that was already configured, for example the psl machine, the prompt was "c1psl", the name of the machine.  So, the indication that work needs to be done is either you get the Boot prompt, or the computer starts to hang while it's trying to load the operating system (since it's not where the computer expects it to be).  If the computer is hanging, key the crate again to power cycle it.  When it gets to the countdown that says "press any key to enter manual boot" or something like that, push some key.  This will get you to the "VxWorks Boot" prompt. 

Once you have this prompt, press "?" to get the boot help menu.  Press "p" to print the current boot parameters (the same list of things that you see with the bootChange command when you telnet in).  Press "c" to go line-by-line through the parameters with the option to change parameters.  I discovered that you can just type what you want the parameter to be next to the old value, and that will change the value.  (ex.  "host name   : linux1   chiara"   will change the host name from the old value of linux1 to the new value that you just typed of chiara). 

After changing the appropriate parameters (as with all the other slow computers, just the [host name] and the [host inet] parameters needed changing), key the crate one more time and let it boot.  It should boot successfully, and when it has finished and given you the name for the prompt (ex. c1auxex), you can just pull out the RJ45 end of the cable from the computer, and move on to the next one.

 

 Koji, Jenne and Steve

 

Preparation to reboot:

1, closed VA6, V5 disconnected cable to valves ( closed all annuloses )

2, closed V1, disconnected it and stopped Maglev rotation

3, closed V4, disconnected its cable

   See Atm1,  This set up is insured us so there can not be any accidental valve switching to vent the vacuum envelope if reboot-caos strikes.[moving=disconnected]

4, RESET c1Vac1 and c1Vac2 one by one and together. They both went at once. We did NOT power recycled.

    Jenne entered the new "carma" words on  the old Dell laptop and checked the good answers. The reboot was done.

    Note: c1Vac1 green-RUN indicator LED is yellow. It is fine as yellow.

5, Checked and TOGGLED valve positions to be correct value ( We did not correct the the small turbo pumps monitor positions, but they  were alive )

6,  V4 was reconnected and opened. Maglev was started.

7,  V1 cable reconnected and opened at full rotation speed of 560 Hz

8,  V5 cable reconnected,  valve opened..............VA6 cable connected and opened........

9,   Vacuum Normal valve configuration was reached.

 

 Yesterday's  reboot was prepared as stated above with one difference. 

  c1Vac1 and c1Vac2 were DOWN before reset. The disconnected valves stayed closed (plus VC1) . This saved us, so the main volume was not vented.

  All others OPENED. PR1 and PR2  rouphing pumps turned ON.  Ion pumps gate valve opened too. The ion pumps did not matter either because they were pump down recently.

  We'll have to rewrite how to reboot vacuum.

  

 

 

 

Attachment 1: c1vac1resetReboot.png
c1vac1resetReboot.png
Attachment 2: c1Vac1&2down.jpg
c1Vac1&2down.jpg
  10597   Fri Oct 10 14:41:04 2014 SteveUpdateVACPower outage II & recovery

Quote:

Quote:

Quote:

Post 30-40min unexpected power outage this morning, Steve checked the status of the vacuum and I powered up Chiara.

I brought back the FE machines and keyed all the crates to bring back the slow machines but for the vac computers.

c1vac1 is not responding as of now. All other computers have come back and are alive.

 

 IFO vacuum, air condition and PMC HV are still down. PSL out put beam is blocked on the table.

 We are pumping again. This is a temporary configuration. The annuloses are at atmosphere. The reset reboot of c1Vac1 and 2 opened everything except the valves that were disconnected.

TP2 lost it's vent solenoid power supply and dry pump during the power outage.

They were replaced but the new small turbo controller is not set up as the old TP2 was so it does not allow V4 to open. 

Tomorrow I will swap back the old controller,  pump down the annuloses and close off the ion pumps.

I removed the beam block from the PSL table and opened the shutter. CC4 has the real pressure 2e-5 Torr  

CC1 is not real.

 Tp2 is controlled by old controller. Annuloses pumped down. Valve configuration: "vacuum normal "

  Ion pumps closed at  <1e-4 mT

Attachment 1: recovery_poweroutage.png
recovery_poweroutage.png
  10598   Mon Oct 13 12:01:28 2014 ericqUpdateLSCWhich side of optical spring are we on?

 I went back into the DQ channels to look at the TF from AO injection to REFLDC (which is easy to do with this kind of noise injection TF).  

AOInjection_SqrtInv_REFLDC.png

I fear that REFL does not seem to have as much phase under the resonance as we have modeled, lacking about 10-20 degrees. This could result from the zero in the REFL DC response that we've modeled at ~200ish Hz is actually higher. I'll look into what affects the frequency of that feature. 

It is, of course, possible, that this measurement doesn't properly cancel out the various digital effects, but the REFLDC phase curves do seem to settle to (+/-) 90 after the pole as expected. 

DTT XML file is attached. 

Attachment 2: AOinjection_SqrtInv_REFLDC.xml.zip
  10599   Mon Oct 13 14:44:52 2014 SteveUpdateVACRGA scan pd78 -day 13

 Our first RGA scan since May 27, 2014 elog10585

 The Rga is still warming up. It was turned on 3 days ago as we recovered from the second power outage.

 

Attachment 1: RGAscan13Oct2014.png
RGAscan13Oct2014.png
  10600   Mon Oct 13 16:08:49 2014 JenneUpdateCDSFrame builder is mad

I think the daqd process isn't running on the frame builder. 

Daqd_problem_maybe.png

I tried telnetting' to fb's port 8087 (telnet fb 8087) and typing "shutdown", but so far that is hanging and hasn't returned a prompt to me in the last few minutes.  Also, if I do a "ps -ef | grep daqd" in another terminal, it hangs. 

I wasn't sure if this was an ntp problem (although that has been indicated in the past by 1 red block, not 2 red blocks and a white one), so I did "sudo /etc/init.d/ntp-client restart", but that didn't make any change.  I also did an mxstream restart just in case, but that didn't help either. 

I can ssh to the frame builder, but I can't do another telnet (the first one is still hung).  I get an error "telnet: Unable to connect to remote host: Invalid argument"

Thoughts and suggestions are welcome!

  10601   Mon Oct 13 16:57:26 2014 KojiUpdateCDSFrame builder is mad

CPU load seems extremely high. You need to reboot it, I think

controls@fb /proc 0$ cat loadavg
36.85 30.52 22.66 1/163 19295

  10602   Mon Oct 13 17:09:38 2014 ericqUpdateCDSFrame builder is mad

 

This CPU load may have been me deleting some old frame files, to see if that would allow daqd to come back to life. 

Daqd was segfaulting, and behaving in a manner similar to what is described here: (stack exchange link). However, I couldn't kill or revive daqd, so I rebooted the FB. 

Things seem ok for now...

 

  10603   Mon Oct 13 21:20:56 2014 JenneUpdateLSCWhich side of optical spring are we on? (No progress)

[Jenne, Diego]

In order to distinguish between the spring and antispring sides of the CARM resonance, we need to have transfer function measurements down to at least 100 Hz (although lower is better). 

We tried to get some transfer functions the same way Q did, but noticed that (a) we couldn't get any low frequency coherence, and (b) that when we increased the amplitude of the white (well, lowpass at 5kHz) noise, the coherence between the AO injection and REFL DC went down.  Not clear why this is.

Anyhow, we tried taking good ol' fashioned swept sine transfer functions, although eventually the lightbulb came on that the AO path has a highpass in it.  Duh, Jenne.  So, we started trying to actuate on MC2 position rather than the AO path laser frequency.  We didn't get too far though before El Salvadore decided to have a few 7.4 earthquakes.  We're bored of aftershocks knocking us out of lock, so we're going to come back to this tomorrow.

 

  10604   Mon Oct 13 21:59:47 2014 ranaUpdateComputer Scripts / ProgramsWhich side of optical spring are we on? (No progress)

 

 Since no one was here, I started the Ubuntu 10 - 12 upgrade on Rossa. It didn't run at first because it wanted to remove 'update-manager-kde' even though it was on the blacklist. I removed it from the command line and now its running. Allegra, OTOH, refuses to upgrade. Someone please ask Diego to wipe it and then install Ubuntu 12 LTS on there in the morning...its a good way to learn the Martian CDS setup.

  10605   Tue Oct 14 17:38:31 2014 ericqUpdateComputer Scripts / ProgramsRossa and Allegra wiped, Ubuntu 12.04 installed

When I came in, Rossa was booted to Ubuntu 10. I tried rebooting to select 12, but couldn't ever successfully boot again. Since Diego was setting up Allegra from scratch, I've wiped and done the same with Rossa. 

  10606   Tue Oct 14 23:44:42 2014 diegoUpdateComputer Scripts / ProgramsRossa and Allegra wiped, Ubuntu 12.04 installed

Allegra and Rossa wiped and updated to Ubuntu 12.04.5 by me and Ericq; the following procedure was followed:

1) create "controls" user with uid=1001, gid=1001
2) setup network configuration (IP, Mask, Gateway, DNS), .bashrc, /etc/resolv.conf
3) add synaptic package manager (Ubuntu Software Center used by default)
4) add package nfs-common (and possibly libnfs1) to mount nfs volumes; mount nfs volume adding the line "chiara:/home/cds/       /cvs/cds/       nfs     rw,bg   0    0" in /etc/fstab
5) add package firmware-linux-nonfree, needed for graphics hardware recognition (ATI Radeon HD 2400 Pro): due to kernel and xorg-server versions of 12.04.5, and because ATI dropped support for legacy cards in their proprietary driver fglrx the only solution is to keep Gallium drivers
6) add packages libmotif3 grace, needed by dataviewer
7) add repository from https://www.lsc-group.phys.uwm.edu/daswg/download/repositories.html (Debian Squeeze); install lcssoft-archive-keyring as first package or apt-get will complain
8) add package lscsoft-metaio libjpeg62, needed by diaggui/awggui (Ericq: used lalmetaio on rossa)
9) add packages python-numpy python-matplotlib python-scipy ipython
10) change ownership of /opt/ to controls:controls
11) add csh package
12) add t1-xfree86-nonfree ttf-xfree86-nonfree xfonts-75dpi xfonts-100dpi, needed by diaggui/awggui (needs reboot)
13) add openssh-server

 

Ubuntu creates the first user during installation with uid=1000 and gid=1000; if needed, they could be changed afterwards using a second user account and the following procedure (twice, if the second users gets the 1001 uid and gid):

sudo usermod -u <NEWUID> <LOGIN>   
sudo groupmod -g <NEWGID> <GROUP>
sudo find /home/ -user <OLDUID> -exec chown -h <NEWUID> {} \;
sudo find /home/ -group <OLDGID> -exec chgrp -h <NEWGID> {} \;
sudo usermod -g <NEWGID> <LOGIN>

  10607   Wed Oct 15 02:58:03 2014 JenneUpdateLSCWhich side of optical spring are we on?

Some measurements.  Unclear meaning.  

We tried both positive and negative numbers in the CARM offset, and then looked at transfer functions at various arm powers. The hope is to be able to compare these with some simulation to figure out which side of the CARM resonance we are on.

The biggest empirical take-away is that we repeatedly (3 times in a row) lost lock when holding at arm powers of about 5 with negative CARM offsets.  However, we were repeatedly (2+ times tonight) able to sit and hold at arm powers of 10+ with positive CARM offsets.

 

 

 

I am not sure that we get enough information out of these plots to tell us which side of the CARM resonance we are really on.  Q is working on taking some open loop CARM measurements (actuating and measuring at SUS-MC2_LSC) to see if we can compare those more directly to Rana's plots.

Positive number in the digital CARM offset:

PRFPMI_MC2injection_PosCARMoffset_REFLDC_TRX_response_14Oct2014_TRX.pdf

PRFPMI_MC2injection_PosCARMoffset_REFLDC_TRX_response_14Oct2014_REFLDC.pdf

Negative numbers in digital CARM offset:

PRFPMI_MC2injection_NegCARMoffset_REFLDC_TRX_response_14Oct2014_TRX.pdf

PRFPMI_MC2injection_NegCARMoffset_REFLDC_TRX_response_14Oct2014_REFLDC.pdf

  10608   Wed Oct 15 02:59:04 2014 ranaUpdateLSCCARM W/N TFs

 In my previous elog in this thread, I showed the CARM OLG given some new digital filters and the varying CARM plant (spring side, not anti-spring). Jenne has subsequently produced the TFs for all of the rest of the CARM offsets.

These attached plots for several CARM offsets show that the anti-spring side is much more stable than the spring side and so we should use that. Annecadotedally, we think that positive CARM offsets are more stable when going to arm powers of > 10, so perhaps this means that +CARM = -SPRING.

The first PDF shows the spring OLGs and the 2nd one shows the antispring OLGs. I have put in some gain changes to keep the UGF approximately the same as the offset is changed.

The PDF thumbnails will become visible once Q and Diego install the new nodus.

 UPDATE OCt 16: this is all wrong! bad conversion of filters within the invbilinear.m function.

Attachment 1: spring.pdf
spring.pdf
Attachment 2: antispring.pdf
antispring.pdf
  10609   Wed Oct 15 13:38:33 2014 JenneUpdateLSCCARM W/N TFs

Here are the same plots, but the legend also includes the arm power that we expect at that CARM offset.  


Here is what the arm powers look like as a function of CARM offset according to Optickle.  Note that the cyan trace's maximum matches what Q has simulated in Mist with the same high losses.  For illustration I've plotted the single arm power, so that you can see it's normalized to 1.  Then, the other traces are the full PRFPMI buildup, with various amounts of arm loss.  The "no loss" case is with 0ppm loss per ETM.  The "150 ppm loss" case is with 150 ppm of loss per ETM.  The "high loss" case is representative of what Q has measured, so I have put 500 ppm loss for ETMX and 150 ppm loss for ETMY.

ArmPower_vs_Loss.png


And, the transfer functions (all these, as with all TFs in the last week, use the "high loss" situation with 500ppm for ETMX and 150ppm for ETMY).

TFs_TRX_vsCARMoffset_PRFPMI_antispring.pngTFs_TRX_vsCARMoffset_PRFPMI_spring.png

TFs_REFLDC_vsCARMoffset_PRFPMI_antispring.pngTFs_REFLDC_vsCARMoffset_PRFPMI_spring.png

TFs_REFL11I_vsCARMoffset_PRFPMI_antispring.pngTFs_REFL11I_vsCARMoffset_PRFPMI_spring.png

  10610   Wed Oct 15 17:09:49 2014 manasaUpdateGeneralDiode laser test preparation

[EricG, manasa]

The He-Ne laser oplev setup was swapped with a fiber-coupled diode laser from W Bridge. The laser module and its power supply are sitting on a bench in the east side of the SP table. 

  10611   Wed Oct 15 17:18:10 2014 JenneUpdateComputer Scripts / ProgramsDataviewer fix with Ubuntu 12.04

 

 I have modified the Dataviewer launcher (which runs when you either click the icon or type "dataviewer" in the terminal).  

A semi-old problem was that it would open in the file /users/Templates, but our dataviewer templates start in /users/Templates/Dataviewer_Templates.  Now this is the folder that dataviewer opens into.  This was not related to the upgrade to Ubuntu 12, but will be overwritten any time someone does a checkout of the /ligo/apps/launchers folder.

A problem that is related to the Ubuntu 12 situation, which we had been seeing on Ottavia and Pianosa for a few weeks, was that the variable NDSSERVER was set to fb:8088, which is required for cdsutils to work.  However, dataviewer wants this variable to be set to just fb.  So, locally in the dataviewer launcher script, I set NDSSERVER=fb.  NB: I do not export this variable, because I don't want to screw up the cdsutils.  This may need to be undone if we ever upgrade our Dataviewer.

  10612   Wed Oct 15 19:56:38 2014 JenneUpdateLSCWhich side of optical spring are we on? Meas vs Model

 I have plotted measured data from last night (elog 10607) with a version of the result from Rana's simulink CARM loop model (elog 10593).

The measured data that was taken last night (open circles in plots) is with an injection into MC2 position, and I'm reading out TRX.  This is for the negative side of the digital CARM offset, which is the one that we can only get to arm powers of 5ish.

The modeled data (solid lines in plots) is derived from what Rana has been plotting the last few days, but it's not quite identical.  I added another excitation point to the simulink model at the same place as the "CARM OUT" measurement point.  This is to match the fact that the measured transfer functions were taken by driving MC2.  I then asked matlab to give me the transfer function between this new excitation point (CARM CTRL point) and the IN1 point of the loop, which should be equivalent to our TRX_OUT.  So, I believe that what I'm plotting is equivalent to TRX/MC2.  The difference between the 2 plots is just that one uses the modeled spring-side optical response, and the other uses the modeled antispring-side response.

AntispringModel_NegOffsetMeas_comparison.pdf

SpringModel_NegOffsetMeas_comparison.pdf

I have zoomed the X-axis of these plots to be between 30 Hz - 3 kHz, which is the range that we had coherence of better than 0.8ish last night in the measurements.  The modeled data is all given the same scale factor (even between plots), and is set so that the lowest arm power traces (pink) line up around 150 Hz. 

I conclude from these plots that we still don't know what side of the CARM resonance we are on. 

 I have not plotted the measurements from the positive side of the digital CARM offset, because those transfer functions were to sqrtInvTRX, not plain TRX, whereas the model only is for plain TRX. There should only be an overall gain difference between them though, no phase difference.  If you look at last night's data, you'll see that the positive side of the CARM offset measured phase has similar characteristics to the negative offset, i.e. the phase is not flat, but it is roughly flat in both modeled cases, so even with that data, I still say that we don't know what side of the CARM resonance we are on.

 

 

  10613   Wed Oct 15 20:10:29 2014 ericqUpdateLSCInterim DARM Signal

I've done some preliminary modeling to see if there is a good candidate for an IR DARM control signal that is available before the AS55 sign flip. From a DC sweep point of view, ASDC/(TRX+TRY) may be a candidate for further exploration. 


As a reminder, both Finesse and MIST predict a sign flip in the AS55 Q control signal for DARM in the PRFPMI configuration, at a CARM offset of around 118pm.

dcAS55_DARM.pdfAS55Flip.pdf

The CARM offset where this sign flip occurs isn't too far off of where we're currently losing lock, so we have not had the opportunity to switch DARM control off of ALS and over to the quieter IR RF signal of AS55. 


Here are simulated DC DARM sweep plots of our current PRFPMI configuration, with a whole bunch of potential signals that struck me. 

Although the units of most traces are arbitrary in each plot (to fit on the same scale), each plot uses the same arbitrary units (if that makes any sense) so slopes and ratios of values can be read off. 

dcDARMSweep-300.pdfdcDARMSweep-120.pdfdcDARMSweep-50.pdfdcDARMSweep-0.pdf

In the 300 and 120pm plot, you can see that the zero crossing of AS55 is at some considerable DARM offset, and normalizing by TRX doesn't change much about that. "Hold on a second," I hear you say. "Your first plots said that the sign flip happens at around 120pm, so why does the AS55 profile still look bad at 50pm?!" My guess is that, probably due to a combination of Schnupp and arm length asymmetry, CARM offsets move where the peak power is in the DARM coordinate. This picture makes what I mean more clear, perhaps:

2dSweep.pdf

Thus, once we're on the other side of the sign flip, I'm confident that we can use AS55 Q without much problem. 


Now, back to thoughts about an interim signal:

ASDC by itself does not really have the kind of behavior we want; but the power out of AS as a fraction of the ARM power (i.e. ASDC/TRX in the plot) seems to have a rational shape, that is not too unlike what the REFLDC CARM profile looks like.

Why not use POPDC or REFLDC? Well, at the CARM offsets we're currently at, POPDC is dominated by the PRC resonating sidebands, and REFLDC has barely begun to decline, and at lower CARM offsets, they each flatten out before the peak of the little ASDC hill, and so don't do much to improve the shape. Meanwhile, ASDC/TRX has a smooth response to points within some fraction of the DARM line width in all of the plots. 

Thus, as was discussed at today's meeting, I feel it may be possible to lock DARM on ASDC/(TRX+TRY) with some offset, until AS55 becomes feasible.

(In practice, I figure we would divide by the sum of the powers, to reduce the influence of the DARM component of just TRX; we don't want to have DARM/DARM in the error signal for DARM)

Two caveats are:

  • The slope of this signal actually looks more quadratic than linear. Is this ok/manageable?
  • I have not yet made any investigation into the frequency dependent behavior of this thing. Transmission in the denominator will have the CARM pole in it, might get complicated. 

[Code and plots live in /svn/trunk/modeling/PRFPMI_radpressure]

 

ELOG V3.1.3-