Measurement with FPMI

i)By locking the FPMI with AS55Q and arms using POX,POY we measured  the OLTF on AS55Q, the response from BS actuation to error signal on AS55Q  for H_mich. The fitted,  measured OLTF and the residual function is in attachment1. I fitted two parameters and they are time-delay and the gain. The time delay is -275 usec. The time delay in three different control are almost same. The response from BS to AS55Q is in attachment 2.

With these two measuremets, I calclated the H_mich in FPMI. This H_mich should be different from simple MI because the cavity  refrectivity is different from the front mirror. Acrually it changed and the value was
Hmich = 4.4026e7

ii) I excited the ETMX and ETMY and measure the response from actuation to the error signal of MICH on AS55Q. The response is in attachment 3 and 4. from these result I calculated the H_L-l by using the formula as I mentioned. The value was
H_Lx-l = 175.7650 (XARM)
H_Ly-l = 169.8451 (YARM)

iii) I measured the error signal of MICH and XARM and YARM and with measured H_L-l, I estimated the FPMI noise caused by ARM locking. You can see in the higher frequency region than 10 Hz is dominated by noise caused by ARM control in-loop noises. 150 Hz and 220Hz are the UGF of each arms, so the two peaks are caused by arm control. You can see the small difference between FPMI noise and  noise from arms. There are two possibilities, one is that these measurement is not same time measurement so they should have small difference. and  other possibility is the error of the caliculation. But I think it doesn't look so bad estimation.

Next step

We will do same measurement with lock the arms the ALS system on tomorrow. Then we will check the PDH servo or other noise source and investigate the ALS system

 Yesterday and this morning's slow NFS disk access was caused by 'svndumpfilter' being run at linux1 to carve out the Noise Budget directory. It is being moved to another server; I think the disk access is back to normal speed now.

Max and I started upgrading megatron to Ubuntu 12.NN today. We were having some troubles with getting latest python code to run to support the Summary pages stuff.

Its also a nice test to see what CDS tools fail on there, before we upgrade the workstations to Ubuntu 12.

Since its Linux, none of the usual upgrading commands worked, but after an hour or so of reading forums we were able to delete some packages and all the 3rd party packages and get the upgrade to go ahead. We'll have to re-install the LSC, GDS, LAL repos to get it back into shape and get NDS2 working. The upgrade is running in a 'screen' command on there.

Wed Oct 02 14:50:16 2013 

Update #1: The upgrade asks a couple dozen questions so it doesn't proceed by itself. I've been checking in to the 'screen' every couple hours to type in 'Yes' to let it keep going.

Update #2: It finished a few hours ago:

controls@megatron:~ 0$ uname -a
Linux megatron 3.2.0-54-generic #82-Ubuntu SMP Tue Sep 10 20:08:42 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
controls@megatron:~ 0$ date
Wed Oct  2 18:33:41 PDT 2013

The attached plot shows the spectra of all the REFL signals with the PRMI SB lock.

We excited the ITMY_LSC with 3000 counts. We used the Masayuki calibration of ITMY (5 nm / count * (1/f^2)) to estimate this peak in the REFL spectra.

To correctly scale the REFL spectra we account for the fact that the DTT BW was "0.187 Hz" and we turn off the "Bin" radio box before measuring the peak height with the cursor.

Since the ITMY motion is 3000 * 5e-9 / (580.1 Hz)^2 = 44.6 pm_peak, we want the DTT spectrum of the REFL spectra to report that too.

i.e. to convert from peak height to meters_peak, we use this formula:

meters_peak = peak_height * sqrt(BW) * sqrt(2)

I *think* that since the line shows up in multiple bins of the PSD, we should probably integrate a ~0.5 Hz band around the peak, but not sure. Need to check calibration by examining the time series, but this is pretty close.

Mystery: why are the REFL_I 3f signals nearly as good in SNR as the 1f signals? The modelling shows that the optical gain should be ~30-100x less. Can it be that our 1f electronics are that bad?

Bonus: notice how we have cleverly used the comb of bounce frequencies around the calibration line to determine that REFL11 is clipping!

MC unlocked over the weekend and also got severely mis-aligned. It all started around midnight on Saturday.

At first I thought that this was due to the MCS CPU meter being railed at 60 us, so I deleted a bunch of filters in MC1,2,3 that are unused and left over from Den's quantization noise investigations. This reduced the CPU load somewhat, but didn't make any real improvements. Turning on the ASC filter banks in the MC SUS still mis-aligned the MC.

With the MC WFS and MC ASS turned off, there is still some digital junk coming in and misaligning things. Plot attached.

Similar stuff coming in on ITMX, but not ITMY.

Tried restarting various FEs, but there was no effect. Also tried rebooting c1lsc, c1ioo, & c1sus. Finally did 'shutdown -r now' on all 5 computers on the CDS overview screen and simultaneously (almost) pressed the reset button on the RFM switch above the old c1pem crate. Everything came back OK except for c1oaf (I had to manually button his BURT button) and now the ASC inputs on all the SUS are zero when they should be and MC is well locked and aligned.

Rob and I used to do this trick when he thought that a cosmic ray had corrupted a bit in the RFM network.

MC3 watchdog gets tripped sometimes when lock is lost. I noticed that there were no limits set in the MC WFS drive. The attached plot shows that over 40 days, the OUT16 channels from the WFS don't exceed 1000 counts. So I've set the limit to be 2000 in all 6 of the MC ASCPIT/YAW filter banks. Please don't turn them off.

OUT16 is really not the right way to measure this, but for some reason, we don't have any DQ channels from the MC WFS screen ??? So we're not able to measure the trend of the high frequency drive signal.

So I added the WFS(1,2)_I_(PIT,YAW)_OUT_DQ and WFS(1,2)_(PIT,YAW)_OUT_DQ channels to the c1ioo.mdl at 2048 Hz. I used Jamie's excellent 'rtcds' utility to build and install:

1) after making the edits to c1ioo.mdl I saved the file/

2) sshing to c1ioo

3) rtcds stop c1ioo

4) rtcds make c1ioo

5) rtcds install c1ioo

6) rtcds start c1ioo

7) telnet fb 8087

8) daqd> shutdown

That seemed to do it OK.

Unfortunately, all of the instructions that we have in the Wiki for adding channels and model building are misleading and don't mention any of this. There are a few different methods listed which all instruct us to do the whole make and make install business in a bunch of non existent directories.

The upgrade of megatron broke the nds2 service. I have fixed things by

  1) installing the latest version of framecpp (1.19.32) from the lsc debian repository (this was necessary because I couldn't link to the existing version)

  2) built nds2-server-0.5.11 and installed it in the system directories (/usr/bin)

  3) there were a few scripts/links/etc that didn't seem to be set up correctly and I fixed them to correspond with my preious message.

 nds2 is now running and the channel list should be updated regularly and the service restarted as appropriate.

 Rana and I noticed last week that it looked like the REFL11 beam was clipping.  This afternoon, I locked the PRMI with REFL 165 I&Q, and checked the REFL 11 path.  The beam looks fine through all of the optics going to the diode, so I just realigned the beam onto the diode using the itty bitty steering mirror.  I have not yet checked the change (hopefully improvement) in the REFL11 spectrum.

I hooked up the 4395 to the MC servo board test out (TP2A) and looked at the spectrum using our new SPAG4395.py script. We noticed a huge peak at ~3.8 MHz and correctly guessed that it was due to the beat between the MC modulation frequency 29.5 MHz and 3*f1 (~33 MHz).

So we tuned the Marconi for the main mod. from 11065910 to 11066099 Hz and saw the beat note disappear (to within the 1 Hz tuning precision of our Marconi).

New MC length tuning method! Alert the LA Times!

My conjecture is that this temperature dependent mismatch between the modulation frequency (f1) and the MC length  is what leads sometimes to our nasty saturating PC DRIVE signal. TBD.

 I simulated how the 3f signal is affected by the resonance condition of the arms.

To keep it simple, I only simulated a double cavity. The attached plot shows the result. In x there is the arm cavity detuning from resonance (in log scale to show what happens close to the 0 value). In the y axis there is the PRC detuning. So every vertical slice of the upper plot gives a PDH signal for a given arm detuning. The bottom plot shows the power build up inside the arm, which is dominated by the carrier.

The 3f signal is not perturbed in any significant way by the arm resonance condition. This is good and what we expected.

However, in this simulation I had to ensure that the 1f sidebands are not perfectly anti-resonant inside the arms. They are indeed quite far away from resonance. If the modulation frequency is chosen in order to make the 1f sidebands exactly ant-resonant, the 2f will be resonant. This screws up the signal: REFL_3f is made of two contributions of equal amplitude, one on the PRC sidebands resonance and the other on the PRC carrier resonance. When the arm tuning goes to zero, these two cancels out and there is no more PDH...

However, this is a limit case, since the frequency show match perfectly. If the modulation frequency is few arm line widths away from perfect anti-resonance, we have no problem.

Yes, the resonance of the 2nd-order sidebands to the IFO screws up the 3f scheme.

2f (~22MHz) and 10f (~110MHz) are at x 5.6 and x 27.9 FSR from the carrier, so that's not the case.

Could we also see how much gain fluctuation of the 3f signals we would experience when the arm comes into the resonance?

Right near the end of summer, I had an ISS board that was nominally working, but had a few problems I couldn't really sort out. Since I've been back, I've spent a lot of time just replacing parts, trying different circuit topologies and generally attempting to make the board function as I hoped it might in all those design stages. Below is a brief list of some of the problems I've been fixing as well as the first good characterization of the board transfer function that I've been able to get.

We'll start with some of the simple problems and proceed to more complicated ones.

• The 5V reference I was using to obtain an error signal from some arbitrary DC photodiode readout was only producing ~2.5 V. 
  • Turns out I just need a FET type op-amp for the Sallen-Key Filter that I was using to clean up any noise in the reference output, as the leakage current in a AD829 was causing a significant voltage drop. I put in an OPA140 and everything worked marvelously.
• The way I set up input grounding (i.e. send a ~0 amplitude signal through the board as an input) passed a few Amps through one of my chips causing it to burn out rather fantastically.
  • There isn't a good way to fix this on the current board (besides just getting rid of the functionality altogether) so my solution so far has just been to redesign that particular sub-system/feature and when we implement the second version of the ISS, the input grounding will be done correctly
• One of the ICs I'm using, specifically the AD8436 RMS-to-DC converter, causes some super strange oscillations in -5V power line. When this chip is soldered onto the board, the -5V supply jumps between -3V and -10V rather sporadically and the DC power-supply used to provide that -5V says that board is drawing ~600 mA on that particular power line.
  • To date, I don't really have any idea what's going with this chip, and I've tried a lot of things to remedy the problem. My first thought was that I had some sort of short somewhere so I took the chip off the board, cleaned up all the excess solder and flux around the chip's footprint and then meticulously soldered a new chip on (when I say meticulously, it took over an hour to solder 20 little feet. I really really didn't want to short anything accidentally as the chip only comes in a package with ridicously small spacing between the leads). Lo and behold, nothing happened. I still saw the same oscillations in power supply and the board was still drawing between >500 mA on that line. Just to be sure, I soldered on a third chip taking the same amount of care and had the same problems.
  • I went over the schematic in Altium that we used to order the board, and unless the manufacturer made a mistake somewhere, there aren't any incorrectly routed signals would cause, say, two active devices to try setting the voltage of a particular node to different values.
  • I got some QSOP-to-DIP package converters so that I could mess around with the AD8436 on a breadboard to make sure it functioned correctly. I set up an identical circuit to the one on the PCB and didn't see any oscillations in the power supply, both for +-5V and +-15V as the chip can handle both supply voltages. I'm not really sure how to interpret this...
  • I'm still actively trying to figure this particular problem out, but I'm shooting in the dark at this point. 
• Initial attempts to measure the transfer-function of the board were wrought with failure.
  • I figured out, with Nic's help, that the board needs the 'loop closed' with a significant broadband attenuator (to simulate the plant optics discussed in elog 9331) in order to not have constant railing of the high gain op-amp filter stages. Even after I did this, the measured transfer functions were not at all consistent with simulation. I wasn't sure if it was just a part issue, a design issue or a misunderstanding/bad data collection on my part so I just redesigned the whole servo and stuffed the board with entirely new components from around the 40m. Turns out the newly designed servo behaved more properly, as I will show below.

The above list encompasses all the issues I've had in making the ISS board function correctly. No other major problems exist to my knowledge.

I was able to measure both the open- and closed-loop transfer functions of the servo with the SR785. The results are shown below.

The transfer function with the boosts on caps at a particular value set by op-amp railing, i.e. below 100 Hz, the op-amps are already putting out their max voltage. This is the usual physical limitation when measuring the transfer function of an integrator. We can also see that the measured phase follows the simulated phase above ~300 Hz. The 'phase matching' at low frequency is again do to the op-amp railing in the servo output..

The closed-loop gain is shown below,

The measured closed-loop gain with the boosts on again matches the LISO simulation quite well except at low frequency where we are limited by op-amp railing. We compare the measured closed-loop transfer function to the desired noise suppression stipulated in my previous elog 9331,

 And we might hopefully conclude that my servo functions as desired. One should note that the op-amp railing seen in these measurements is not indicative of limitations we might face in some application of the ISS for the following reason. These transfer functions were measured with a 100 mV excitation signal (it is necessary to keep this signal amplitude large enough so that the inherent signal-to-noise ratio of the excitation source is large enough for accurate measurement) which leads to somewhat prompt railing of the op-amps. When the ISS operates to actually stabilize a laser, the input error signal will be much smaller (on the order of a few 10's of mV or less) and will decrease significantly assuming correct operation of the ISS. This means we won't see the same type of gain limitations.

What now, you ask?

Aside from the problem with the AD8436 chip, the ISS board seems to be functioning correctly. The transfer functions we have measured are correct to within the component tolerances and all of the various subsystems are behaving as they were designed to. Moving toward the goal of having this system work in situ for the CTN experiment, I need to do the following things,

• Design a housing for the board -> order said housing and the front panel previously designed
• Make sure the power supply daughter PCB boards are compatible with the ISS board and can provide power correctly
• Talk to Evan and Tara about integrating the ISS with their experiment and make sure my board can do everything it needs to in that context.

So close, or so I say all the time 

 From the simulation there is no visible change in the gain.

The Phase tracker outputs (= ALS X/Y error signals) are now conveyed to the LSC model.

Their entry points at the LSC model are C1:LSC-ALSX_IN1 and C1:LSC-ALSY_IN1.
They are connected to the signal matrix (28th and 29th signals) via signal conditioning filters (C1:LSC-ALSX and C1:LSC-ALSY).

The main LSC screen has not been updated. The conventional ALS servos are still remains as they were.

This renovation required the recompilation of c1als, c1rfm, and c1lsc. Two PCIe-RFM bridge paths were added resulting in
increase of the c1rfm timing budget from 38 to 44.

Last week, Koji cleaned up the LSC model to make it much more readable, while he was working on piping the ALS signals to the LSC model.  However, somehow the DAQ Channels block got deleted before the model was committed to the svn.  Since there were 2 months between svn checkins for c1lsc.mdl, it's possible that someone had the model open just to look at, and the block got deleted, and that's the version that Koji started with. 

Anyhow, thankfully we have the svn, so Koji and I found that the DAQ Channels block was (as expected) in the previously checked-in version of the LSC model.  I put a copy of the old model onto my desktop, opened it up, copied the DAQ Channels block, and then pasted it into the new cleaned-up version of the model.  (Jamie - is there a way to conveniently download a previous version through the web interface?)

I have checked it in, compiled and restarted the lsc model.  The _DQ channels are back now.

From Linda and Bram:

Measurement 

Looking back at what I did in april (see log #8411) I realized that it is possible to get an estimate of how much the PRC length is wrong looking at the splitting of the sideband resonant peak as visible in the POP_110_I signal. With the help of Jenne the PRMI was aligned and left swinging. The first plot shows a typical example of the peak splitting of 55MHz sidebands. This is much larger than what was observed in April.

When the sidebands resonate inside the PRC they get a differential dephasing given by 

dPhi = 4*pi*f_mod/c * dL

where dL is the cavity length error with respect to the one that makes the sidebands perfectly resonant when the arms are not there. This is not exactly the error we are interested in, since we should take into account the shift from anti-resonance of the SBs in the arm cavities.

Nevertheless, I can measure the splitting of the peak in units of the peaks full width at half maximum (FWHM). I did this fitting few peaks with the sum of two Airy peaks. Here is an example of the result

The average splitting is 1.8 times the FWHM. Knowing the PRC finesse, one can determine the length error:

dL = c / (4 * f_mod * Finesse) * (dPhi / FWHM)

Assuming a finesse of 60, I get a length error of 4 cm.

To get another estimate, we kicked the PRM in order to get some almost linear sweeps of the PRC length. Here is one of the best results:

The distance between consecutive peaks is the free spectral range (FSR) of the PRC cavity. Again, I can measure the peak splitting in units of the FSR and determine the length error:

dL = c / (4 * f_mod) * (dPhi / FSR)

The result is again a length error of 4 cm.

Simulation

An error of 4 cm seems pretty big. Therefore I set up a quick simulation with MIST to check if this makes sense. Indeed, if I simulate a PRMI with the 40m parameters and move the PRC length from the optimal one, I get the following result for POP_110_I, which is consistent with the measurement.

 Therefore, we can quite confidently assume that the PRC is off by 4 cm with respect to the position that would make the 55 MHz sideband resonant without arms. Unfortunately, it is not possible with this technique to infere the direction of the error.

My hunch is that the PRC is SHORT by a few cm, not long. 

In my Optickle simulation, the sidebands are not perfectly co-resonating in the PRMI when the arms are not locked.  See Fig 1, which is the fields in the PRMI using the design PRC length.  If I add 5cm to the PRC length, I get Fig 2, where the peaks are about the same separation, but the upper and lower sidebands have swapped sides of the 0 mark.  However, if I remove 5cm from the PRC length, I get Fig 3, where the peaks are much farther apart than in Fig 1.  This case looks more similar to the data that Gabriele plotted in his elog entry, where the peaks are separated by at least a linewidth.  This is not at all conclusive, but it's a guess for which direction we need to move.  Obviously doing an actual measurement will be better. 

My tummy feelings also agree with this simulation:  When we flipped PR3 (the only optic change in the PRC since Gabriele and I measured the 55MHz peak separation in April), since the HR side of the optic is now at the back, we had to push the whole suspension cage forward to get the beam aligned to the Yarm.  Conversely, however, transmitting through the glass substrate adds to the optical path length.  So, my tummy feelings may be wrong.

Figure 1, PRC at design length, PRMI sweep:

Figure 2, PRC 5cm longer than design length:

Figure 3, PRC 5cm shorter than design length:

Maybe I'm getting confused, but I still believe there is no way to decide the direction from yesterday's measurement.

Let's say for example that the arm sideband detuning from antiresonance is equivalent to a PRC length change of +1cm away from the position of ideal resonance of the sidebands without arms. Then we can get a measured separation of the sidebands, without arms, corresponding to 5cm both if the PRC is off by +4cm or by -6cm...

A while ago, I noticed that the most significant bits of the LSC whitening DOs are not toggling.
I track this issue down and found what is happening. I need experts' help.

To illuminate the issue, terminators are connected to Bit15 of the Bit2Word blocks in the LSC model (attached screen shots).

The corresponding source file is found in c1lsc.c at the following location.
The last channels of the Bit2Word are connected to lsc_cm_slow (the filter module).
This is the source of the issue. This wrong assignment of the connections
can't be changed by connecting Go-From tags to the chennels.

/opt/rtcds/caltech/c1/rtbuild/src/fe/c1lsc/c1lsc.c

3881// Bit2Word:  LSC_cdsBit2Word1                                                                                                              
3882{
3883double ins[16] = {
3884        lsc_as110_logicaloperator4,
3885        lsc_as110_logicaloperator1,
3886        lsc_refl11_logicaloperator4,
3887        lsc_refl11_logicaloperator1,
3888        lsc_pox11_logicaloperator4,
3889        lsc_pox11_logicaloperator1,
3890        lsc_poy11_logicaloperator4,
3891        lsc_poy11_logicaloperator1,
3892        lsc_refl33_logicaloperator4,
3893        lsc_refl33_logicaloperator1,
3894        lsc_pop22_logicaloperator4,
3895        lsc_pop22_logicaloperator1,
3896        lsc_pop110_logicaloperator4,
3897        lsc_pop110_logicaloperator1,
3898        lsc_as165_logicaloperator4,
3899        lsc_cm_slow
3900};
3901lsc_cdsbit2word1 = 0;
3902for (ii = 0; ii < 16; ii++)
3903{
3904if (ins[ii]) {
3905lsc_cdsbit2word1 += powers_of_2[ii];
3906}
3907}
3908}

3946// Bit2Word:  LSC_cdsBit2Word2                                                                                                              
3947{                                                                                                                                           
3948double ins[16] = {                                                                                                                          
3949        lsc_as55_logicaloperator4,                                                                                                          
3950        lsc_as55_logicaloperator1,                                                                                                          
3951        lsc_refl55_logicaloperator4,                                                                                                        
3952        lsc_refl55_logicaloperator1,                                                                                                        
3953        lsc_pop55_logicaloperator4,                                                                                                         
3954        lsc_pop55_logicaloperator1,                                                                                                         
3955        lsc_refl165_logicaloperator4,                                                                                                       
3956        lsc_refl165_logicaloperator1,                                                                                                       
3957        lsc_logicaloperator_cm_ctrl,                                                                                                        
3958        ground,                                                                                                                             
3959        ground,                                                                                                                             
3960        lsc_logicaloperator_popdc,                                                                                                          
3961        lsc_logicaloperator_poydc,                                                                                                          
3962        lsc_logicaloperator_poxdc,                                                                                                          
3963        lsc_logicaloperator_refldc,                                                                                                         
3964        lsc_cm_slow                                                                                                                         
3965};                                                                                                                                          
3966lsc_cdsbit2word2 = 0;                                                                                                                       
3967for (ii = 0; ii < 16; ii++)                                                                                                                 
3968{                                                                                                                                           
3969if (ins[ii]) {                                                                                                                              
3970lsc_cdsbit2word2 += powers_of_2[ii];
3971}
3972}
3973}

I submitted a bug report for this:

https://bugzilla.ligo-wa.caltech.edu/bugzilla3/show_bug.cgi?id=553

However, given how old our RCG version is (2.5 vs. 2.8 current deployed at the sites) I don't think we're going to see any traction on this.  Even if this is still a bug in 2.8, they'll only fix it in 2.8.  There's no way they're going to make a bug fix release for 2.5.

We need to upgrade.

The bug is still there but the incorrect bits are now overridden.

Dec 22 between 6AM and 7AM, physical or logical failure has occure on the 4th disk in the RAID array on linux1.
This caused the RAID disk fell into the readonly mode. All of the hosts dependent on linux1 via NFS were affected by the incident.

Today the system has been recovered. The failed filesystem was restored by copying all of the files (1.3TB total) on the RAID to a 2TB SATA disk.
The depending hosts were restarted and we recovered elog/wiki access as well as the interferometer control system.

Recovery process

o Recover the access to linux1

- Connect an LCD display on the host. The keyboard is already connected and on the machine.
- One can login to linux1 from one of the virtual consoles, which can be switched by Alt+1/2/3 ...etc
- The device file of the RAID is /dev/sda1
- The boot didn't go straightforward as mounting of the disks accoding to /dev/fstab doesn't go well.
- The 40m root password was used to login with the filesystem recovery mode.
- Use the following command to make the editing of /etc/fstab available

# mount -o rw, remount /

- In order to make the normal reboot successfull, the line for the RAID in /etc/fstab needed to be commented out.

o Connect the external disk on linux1

- Brought a spare 2TB SATA disk from rossa.
- Connect the disk via an USB-SATA enclosure (dev/sdd1)
- Mount the 2TB disk on /tmpdisk
- Run the following command for the duplication

# rsync -aHuv --progress /home/ /tmpdisk/ >/rsync_KA_20131229_0230.log

- Because of the slow SCSI I/F, the copy rate was limited to ~6MB/s. The copy started on 27th and finished 31st.

o Restart linux1

- It was found that linux1 couldn't boot if the USB drive is connected.
- The machine has two SATA ports. These two are used for another RAID array that is not actually used. (/oldhome)
- linux1 was pulled out from the shelf in order to remove the two SATA disks.
- The 2TB disk was installed on the SATA port0.
- Restart linux1 but didn't start as the new disk is recognized as the boot disk.
- The BIOS setting was changed so that the 80GB PATA disk is recognized as the boot disk.
- The boot process fell into the filesystem recovery mode again. /etc/fstab was modified as follows.

- Another reboot make the operating system launched as usual.

o What's happen to the RAID?

- Hot removal of the disk #4.
- Hot plug of the disk #4.
- Disk #4 started to get rebuilt -> ~3hours rebuilding done
- This made the system marked as "clean". Now the raid (/dev/sdb1) can be mounted as usual.

o Nodus

- Root password of nodus is not known.
- Connect an LCD monitor and a Sun keyboard on nodus.
- Type Stop-A. This leads the nodus transition to the monitor mode.
- Type sync.
- This leads the system rebooted.

IFO restart after the recovery of linux1

Machine recovery in the following order
- Start fb
- Start the following machines: mafalda, megatron, op340m
- Start c1ioo, c1lsc, c1sus, c1iscex, c1iscey

CDS recovery / burtrestore

- Confirm all of the RT systems are running in "green". If not, restart corresponding model.
- c1iscaux, ciscaux2 didn't have response (white boxes). Went to the LCS digital rack and power cycled these targets
- burtrestore: The snapshots at Dec 19 05:07 were used. For c1iscaux and c1iscaux2 the snapshots at Dec 22 05:07 were used.

fast machines
c1alsepics.snap
c1assepics.snap
c1asxepics.snap
c1calepics.snap
c1iooepics.snap
c1lscepics.snap
c1lspepics.snap
c1mcsepics.snap
c1oafepics.snap
c1pemepics.snap
c1rfmepics.snap
c1scxepics.snap
c1scyepics.snap
c1spxepics.snap
c1supepics.snap
c1susepics.snap
c1tstepics.snap

slow machines
c1auxex.snap
c1auxey.snap
c1aux.snap
c1iool0.snap
c1iscaux2.snap
c1iscaux.snap
c1psl.snap
c1susaux.snap

IFO recovery

- Reload watchdogs => restore sus damping
- MC misaligned but TEM00 was locked
- Gave a small touch on MC2 yaw => IMC almost aligned
- Autolocker wasn't running => Manually launched rather than wait for an hour for cron to launch it
- PMC was largely misaligned. => Aligned on the PSL table (PSLTRANS 0.640->0.753)
- MC WFS ON
- IFO X/Y arm locked and aligned with ASS.
- PRMI mode: manually aligned PRM. The PRMIsb momentally locked.

Well done Koji!  I'm very impressed with the sysadmin skillz.

 Events of the power supply swap:

1, Tested 24V DC ps from Todd

2, Closed V1, VM1 and all annulos valves to create safety net for the reboot. Turbo pumps left on running.

3, Turned computer off

4, Swap power supplies and turned it on

5, Turning the power on of c1vac2 created caos switching of valves. This resulted in a air vent as shown below.

6, VM1 was jammed and it was unable to close. The IOO beam shutter closed and the IFO was venting with air for a few minutes. Maglev did an emergency shut down. TP2's V4 and TP3' V5 closed. RP1 and RP3                           roughing         pumps turned on, their hose was not connected as usual. The RGA shut down to protect itself.

7, Closed annulos valves, stoped the vent at P1 27 torr as the vacuum control was  manually recovered

8, The Maglev and the annuloses were roughed out 500 mtorr . The Maglev was restarted.

9, The IFO pump down followed std procedure from 27 torr. VM1 was moving again as the pressure differential was removed from it.

 Remember: next time at atm .....rough down the cryo volume from 27 torr !

 This is a 10-minute trend of the last 60 days of the pointing of the PSL beam.

The main fluctuation seems to be at the ~30 day time scale (not 24 hour) and its all in the vertical direction; the horizontal drift is ~10x less (as long as we believe there is no calibration error).

So what's causing all of this vertical shift? And why is there not just as much horizontal??

 I went to the PSL table to re-align the input pointing to the IMC. After trying to optimize the pointing into the PMC and not succeeding I also then touched the wrong mirror and messed up our IOO QPD reference pointing.

The IMC is locking again, but I'll have to fix the pointing on Monday.

I'm not sure which pointing Rana wanted to fix today, but here's a measurement of the MC spots.  They actually look pretty good.  There is some room for improvement, but not a lot, so I'm leaving it alone for now, while I play with other things in the IFO.

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
[0.63368182839757914, 1.3004245778952557, 0.33621668795755993, -1.5585578137597658, -3.1344594013487286, -1.0533063060089816]

Since this configuration change, the daily backup was speeded up by factor of more than two.
It was really limited by the bandwidth of the RAID array.

/cvs/cds/rtcds/caltech/c1/scripts/backup/rsync.backup.cumlog:

...
rsync.backup start: 2013-12-20-05:00:00, end: 2013-12-20-07:04:28, errcode 0
...
rsync.backup start: 2014-01-05-05:00:00, end: 2014-01-05-05:55:04, errcode 0

(The daily backup starts from 5:00)

I ran a simulation of a double cavity with a PRC length mismatched w.r.t. the modulation frequency. I summarized the results in the attached PDF. I think it would be important to have a cross check of the results.

In brief:

A mismatch between PRC length and modulation frequency do have an effect on error signals

Multiple zeros appear in REFL_3f/PRCL that can be removed by careful tuning of the demodulation phase (however, the shape of the signal makes difficult to understand which phase is good…)

No visible effect on REFL_1f/CARM

But a large PRCL signal appears in REFL_1f_I, which is used to control CARM. This is not good.

A mismatch of the order of 0.5 cm has a small effect.

 [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:

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...

 [Gabriele, EricQ]

Actually it is difficult to see any laser frequency line in the dark fringe signal, since the Schnupp asymmetry is small. It is much better to use a differential MICH excitation which gives a better signal at the dark port.

We repeated the simulation explained before. We can use both the AS55 or the AS11 signals, bout the first one has a limited linear range and the expected 4cm value is very close to saturation.

[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. 

 Its very doubtful that the MC yaw drift matters for the IFO. That's just a qualitative correlation; the numbers don't hang together.

 Then there must be something else slowly drifting. It was very clear that the good alignment of the IFO was every time lost after few minutes...

[Gabriele, EricQ]

We wanted to try the PRC length measurement,but we ended up spending all the afternoon to lock the PRMI on sidebands. Here are some results

• Lock of PRM on carrier is easy with MICH on AS55_Q and PRCL on REFL55_I. The optimal gains to avoid correction gain peaking are MICH=-5 and PRCL=0.012. The alignment today was must more stable over time than on Friday
• We wanted to move MICH on REFL55_Q. After a few trials we discovered that REFL55_Q is not seeing any MICH signal at all. This is quite strange and we don't understand this.
• Locking PRMI on carrier using REFL165_I and Q was difficult. We thought that was due to a RF amplifier installed in December. We tried to remove it, but since this did not help, we put it back
• We could lock PRMI on carrier and sidebands using REFL11 signals. The optimal demodulation phase is 155. Lock on carrier was achieved with gains MICH=5, PRCL=0.7. Lock on sidebands with MICH gain=-10 and PRCL gain=-0.3. The MICH correction is very high and exciting a tone at few hundreds Hz. Maybe a violin mode of the ITMs?
• Finally we could tune the REFL165 phase to 118.5 and lock on carrier. The lock was not very stable. Gain are: lock on carrier MICH=-0.5, PRCL=0.05. The error signal has a very big offset: to get a dark fringe we had to add a MICH offset of 500 counts. We also had to engage the CLP400 filter to avoid saturating ITMs corrections with MICH.

[Gabriele, EricQ] 

Finally, we managed to lock PRMI on sidebands:

• MICH locked on AS55_Q with gain -10. Demod phase of AS55=18
• PRCL locked on REFL55_I with gain -0.04. Demod phase of REFL55=88
• Triggering on POP110_I at 50/10
• Filter "1:5" of MICH engaged, this improved a lot the stability

 [EricQ, Gabriele]

We could carry out the measurement of PRC length. The AS110 photodiode was plugged into REFL11. So REFL11 is giving us the AS11 signal. Here is the procedure.

1. Lock MICH.
2. Add a line in MICH (amplitude 20000 counts)
3. Tune AS11 demod phase to have the line in I.
4. Change the demod phase by steps of 1 degree around the rough optimum, taking one minute of data at each point
5. Lock PRMI on sidebands
6. Add a line in MICH (amplitude 500 counts)
7. Tune AS11 demod phase to have the line in I.
8. Change the demod phase by steps of 1 degree around the rough optimum, taking one minute of data at each point

We repeated the same measurement also using AS55, with the same procedure.

Roughly, the phase difference for AS11 was 11 degrees and for AS55 it was 23 degrees. A more detailed analysis and a calibration in terms of PRC length will follow.

 I analyzed the data we took yesterday, both using AS11 and AS55. For each value of the phase I estimated the Q/P ratio using a demodulation code. Then I used a linear regression fit to estimate the zero crossing point.

Here are the plots of the data points with the fits:

The measurements a re more noisy in the PRMI configuration, as expected since we had a lot of angular motion. Also, the AS11 data is more noisy. However, the estimated phase differences between PRMI and MICH configurations are:

• AS11 = -10.9 +- 1.0 degrees
• AS55 = -21.1 +- 0.4 degrees

The simulation already described in slogs 9539 and 9541 provides the calibration in terms of PRC length. Here are the curves

The corresponding length errors are

• AS11 = 1.44 +- 0.13 cm
• AS55 = 0.59 +- 0.01 cm

The two results are not consistent one with the other and they are both not consistent with the previous estimate of 4 cm based on the 55MHz sideband peak splitting.

I don't know the reason for this incongruence. I checked the simulation, repeating it with Optickle and I got the same results. So I'm confident that the simulation is not completely wrong.

I also tried to understand which parameters of the IFO can affect the result. The following ones have no impact

• Beam matching
• ITM curvatures
• Schnupp asymmetry
• Distance PR-BS
• ITM and PRM misalignments

The only parameters that could affect the curves are offsets in MICH and PRCL locking point. We should check if this is happening. A first quick look (with EricQ) seems to indicate that we indeed have an offset in PRCL. However, tonight the PRMI is not locking stably on the sidebands. 

If possibile, we will repeat the measurement later on tonight, checking first the PRCL offset.

 I analyzed the data taken yesterday. 

The AS11 data in PRMI configuration is very bad, while the AS55 seems good enough:

The phase differences are 

AS11 = 21 +- 18 degrees (almost useless due to the large error)

AS55 = 11.0 +- 0.4 degrees

The AS55 phase difference is not the same measured in the last trial, but about half of it. The new length estimates are:

AS11 = 3.2 +- 2.8 cm

AS55 = 0.47 +- 0.01 cm

We can probably forget about the AS11 measurement, but the AS55 result is different from the previous estimate... Maybe this is due to the fact that Eric adjusted the PRCL offset, but then we're going in the wrong direction....

[Jenne, Steve]

Steve noticed that the RGA was not logging data and that not all the correct connection lights were on, and he wasn't able to run the "RGAset.py" script (in ...../scripts/RGA/) that sets up the proper parameters. 

I looked, and the computer was not mounting the file system.  I did a remote shutdown, then Steve went in and pushed the power button to turn the machine back on.  After it booted up, it was able to talk to the file system, so I started ..../scripts/RGA/RGAset.py .  The first 2 times I ran the script, it reported errors, but the 3rd time, it reported no communication errors.  So, now that the computer can again talk to the file system, it should be able to run the cronjob, which is set to take data at 4am every day.  Steve will check in the morning to confirm that the data is there.  (The last data that's logged is 22Dec2013, 4am, which is right around when Koji reported and then fixed the file system).

 We are venting tomorrow. This give us an opportunity to fix sick vacuum controller computer. Jamie volunteered.

Remember to rough down cryo and ion pump volumes. Their pressure can be at 1 Torr range after years of accumulated outgassing.  Without total valve controls it is dangerous to have these air pockets. Some of their  gate valves can be leaking and that would explane the slower pumpdown speed. 

[Rich, Jay, Koji]

We blasted the aLIGO RF PD with a 1W IR beam. We did not find any obvious damage.
Rich and Jay brought the PD back to Downs to find any deterioration of the performance with careful tests.

The power modulation setup is at the rejection side of the PBS in front of the laser source.
I checked the beams are nicely damped.
As they may come back here tomorrow, a power supply and a scope is still at the MC side of the PSL enclosure.

 [Manasa, EricQ, Gabriele]

We managed to measure the PRC length using a procedure close to the one described in slog 9573.

We had to modify a bit the reference points, since some of them were not accessible. The distances between points into the BS chamber were measured using a ruler. The distances between points on different chambers were measured using the Leica measurement tool. In total we measured five distances, shown in green in the attached map.

We also measured three additional distances that we used to cross check the results. These are shown in the map in magenta.

The values of the optical lengths we measured are:

LX    = 6828.96 mm
LY    = 6791.74 mm
LPRC  = 6810.35 mm
LX-LY = 37.2196 mm  

The three reference distances are computed by the script and they match well the measured one, within half centimeter:

M32_MP1  = 117.929 mm   (measured = 119 mm)
MP2_MB3  = 242.221 mm   (measured = 249 mm)
M23_MX1p = 220.442 mm   (measured = 226 mm)

See the attached map to see what the names correspond to.

The nominal PRC length (the one that makes SB resonant without arms) can be computed from the IMC length and it is 6777 mm. So, the power recycling cavity is 33 mm too long w.r.t. the nominal length. This is in good agreement with the estimate we got with the SB splitting method (4cm).

According to the simulation in the wiki page the length we want to have the SB resonate when the arms are there is 6753 mm. So the cavity is 57 mm too long.

Attached the new version of the script used for the computation.

 [Manasa, EricQ, Gabriele]

Today we changed the PRC length translating PR2 by 27 mm in the direction of the corner. After this movement we had to realign the PRC cavity to get the beam centered on PRM, PR2, PR3, BS (with apertures) and ITMY (with aperture). To realign we had to move a bit both PR2 and PR3. We could also see some flashes back from the ETMY . //Edit by Manasa : We could see the ETMY reflection close to the center of the ITMY but the arm is not aligned or flashing as yet//. 

After the realignment we measured again the PRC length with the same method of yesterday. We only had to change one of the length to measure, because it was no more accessible today. The new map is attached as well as the new script (the script contains also the SRC length estimation, with random numbers in it).

The new PRC length is 6753 mm, which is exactly our target!

The consistency checks are within 5 mm, which is not bad.

We also measured some distances to estimate the SRC length, but right now I'm a bit confused looking at the notes and it seems there is one missing distance (number 1 in the notes). We'll have to check it again tomorrow.

 Today we measured the missing distance to reconstruct SRC length.

I also changed the way the mirror positions are reconstructed. In total for PRC and SRC we took 13 measurements between different points. The script runs a global fit to these distances based on eight distances and four incidence angles on PR2, PR2, SR2 and SR3. The optimal values are those that minimize the maximum error of the 13 measurements with respect to the ones reconstructed on the base of the parameters. The new script is attached (sorry, the code is not the cleanest one I ever wrote...)

The reconstructed distances are:

Reconstructed lengths [mm]:
LX    = 6771
LY    = 6734
LPRC  = 6752
LX-LY = 37
LSX   = 5493
LSY   = 5456
LSRC  = 5474

The angles of incidence of the beam on the mirrors are very close to those coming from the CAD drawing (within 0.15 degrees):

Reconstructed angles [deg]:
aoi PR3 = 41.11 (CAD 41)
aoi PR2 = 1.48  (CAD 1.5)
aoi SR3 = 43.90 (CAD 44)
aoi SR2 = 5.64  (CAD 5.5)

The errors in the measured distances w.r.t. the reconstructed one are all smaller than 1.5 mm. This seems a good check of the global consistency of the measurement and of the reconstruction method.

NOTES: in the reconstruction, the BS is assumed to be exactly at 45 degrees; wedges are not considered.

• Adjusted the PMC alignment
• Adjusted the IMC length offsets for the MC servo and the FSS servo
• Adjusted the MC alignment. Ran /opt/rtcds/caltech/c1/scripts/MC/WFS/WFS_FilterBank_offsets
 
• The Yarm servo was oscillating. Reduced the servo gain from 0.2 to 0.08.
 
• AS Camera & AS port alignment was adjusted. Now the spot is at the center of the AS camera.
• Cleaned up the ASC offsets on the suspensions (i.e. C1:SUS-***_(PIT|YAW)_OFFSET) by replacing them by the BIAS adjustment.
• Saved the alignment values
• Locked the PRMI with SB with REFL55I for PRCL and AS55Q for MICH
• Aligned the PRM, then checked the alignment of the REFL PDs
• The best POP110I was 500cnt.
• Found REFL165 output was disconnected. It is now restored.
   
• Used the LSC lockins to figure out the demod phases and the signal amplitudes (relative)

PRCL: 100cnt -> PRM 567.01Hz

Signal in demod Q ch were minimized

REFL11I -19.2deg demod I, Lockin I out (C1:CAL-SENSMAT_PRCL_REFL11_I_I_OUTPUT) 12.6 cnt
REFL33I +130.4deg 1.70cnt
REFL55I +17.0deg 2.30cnt
REFL165I -160.5deg 27.8cnt

MICH: 1000cnt -> ITMX(-1) & (ITMY +1.015 => Minimized the signal in REFL11I to obtain pure MICH)

REFL11I   +0.0     REFL11Q   +0.119
REFL33I   +0.023 REFL33Q   -0.012
REFL55I   +0.023 REFL55Q   -0.113
REFL165I +0.68   REFL165Q +0.038

It seems that REFL165 has almost completely degenerated PRCL and MICH.

• Try to replace ITMX/Y with BS (+0.16) / PRM (-0.084)

 ITMX(-1)/ITMY(+1.015) actuation was cancelled by BS (+0.16). This introduces PRCL in REFL11I. This was cancelled by PRM (-0.084)

REFL11I   +0.0     REFL11Q   +0.13
REFL33I   -0.012  REFL33Q   0.025
REFL55I   +0.041 REFL55Q   -0.45
REFL165I +0.69   REFL165Q +/-0.02

Again, It seems that REFL165 has almost completely degenerated PRCL and MICH.

Locking info:

PRCL:
[Signal source] REFL11I (-19.2deg) x 0.16, OR REFL33I (+130.4deg) x 2.0, OR REFL55I (+17.0deg) x1.0, OR REFL165I (-160.5deg) x0.05
[Trigger] POP110I(-81deg) 100/10, FM trigger 35/2, delay 0.5sec FM2/3/6/9
[Servo] FM4/5 always on. G=-0.02, Limitter ON
[Output] PRM x+1.00

MICH:
[Signal source] AS55Q (-5.5deg) x 1, OR REFL11Q x 0.25, OR REFL55Q x-0.06
[Trigger] POP110I 100/10, FM trigger 35/2, delay 5sec FM2/3/9
[Servo] FM4/5 always on. G=-10, Limitter ON
[Output] ITMX -1.0 / ITMY +1.0 (or +1.015), OR PRM -0.084 / BS +0.16

Jenne and I noticed high pitch sound from our acoustic interferometer noise diagnostic system.
The frequency of this narrow band noise was 1256Hz, which is enough close to twice of the PRM violin mode freq.
After putting notch filter at 1256+/-25Hz at the violin filters, the noise is gone. Just in case I copied the same filters to all of the test masses.

Later, I found that the 4th violin modes are excited. Additional notch filters were added to "vio3" filter bank to mitigate the oscillation.

1) Fixup REFL165: remove ND filters, get box for PD, dump diode reflections, put less light on diode, change DC transimpedance (?), max power dissipation on BBPD < 0.5 W w/ 25 V bias. Perhaps replace OP27 with TLE2027.

2) Make plan for fixing fiber layout up and down the arms. Need tubing for the whole run. Don't make it cheesy. Two fibers per arm.

3) Fix LSC model to allow user switching of whitening. Get back to working on AutoLock scripts (not Guardian).

4) Manasa, Q, Jenne, tune Oplev servos Tuesday morning/afternoon.

5) Reconnect the other seismometers (Steve, Jenne). For real.

6) Balance PRMI coils at high frequency.