Today the frequency drift of the auxiliary laser was much slower, I was able to lock it the the PSL and sweep it across 2MHz a few times before the SR560 output railed.  I moved the 1611 photodiode  back a few cm to where the beam is more tightly focused, increasing the beat note power from -42dBm to -33dBm.

I will switch from using the SR560 to the New Focus LB1005 servo controller.  I also plan to add an amplifier with gain 25 output voltage +/- 125 V after the LB1005, to increase the voltage driving the PZTs.

10Hz single pole, combined with a integration of PLL, means that the OLG phase is already -135deg at 10Hz, so the UGF could not possibly be much more than 10Hz.

But it easily acquires lock and stays locked until the output rails. Anyway this is just the first setting that worked while I was changing things non-systematically. Students will improve it to perfection.

As for the 5V output rail of SR560, using something else to go 10V would only be a marginal improvement as the drift is big. The frequency shifted by at least 200MHz while I was watching and it was not slowing down.

According to Evan, offloading to temperature was attempted without much success in the past, but it seems to me that it is still the way to go.

In preparation of allowing a larger offset frequency, I gave Elli a ZFM-2 that is a level 7 mixer for 1MHz to 1GHz.

We should have a New Focus/Newport LB1005 in the lab which is a proper PI controller for laser locking. We also should have +/-120V PZT driver for the JDSU NPROs.

J. Kissel, D. Barker

I've grounded and committed the M3_LOCK banks RC_MASTER.mdl as requested, and committed the new version to userapps repo. Dave confirms that these now compile with RCG 2.9 as expected.

After some feedback, I rearranged the script and commited it into:

/ligo/svncommon/SeiSVN/seismic/HAM-ISI/Common/Misc/HAM_gain_matching_calculation.m

What it does now:

 HAM_gain_matching_calculation(IFO,Chamber,start_time,duration)
 
. Grab the ground seismometer and GS13 data in X, Y, Z from start_time to start_time+duration.
. Calculate and plot the calibrated TF between Ground and GS13
. Take the mean of the amplitude for a [0.1Hz and 0.4Hz] bandwidth

Remember. before running this process, the ISI needs to be in High blend mode (750mHz) on all DOFs with sensor correction OFF.

I put HAM4, 5, 6 in this configuration last night and calculated the new matching gains.

I'll put this new numbers in the MEDM screens in a minute.

Added the changes to the safe.snap files in userapps, by hand,  for the respective optics above. Also committted to SVN.

Entry by Kyle.

Dewpoint of blow-down air measured  -20C

This morning, the VE crew (Kyle, Gerardo, Bubba) held the BSC9 door open a few feet for me while I popped into the chamber and:

- Inspected the ETMx optic HR face with green flashlight - looked just as "dirty" as ~2weeks ago (lots of speckle), no obvious giant particles apparent.

- Inspected the test mass EQ stops.  I found that the barrel ones were on the tighter side of the ~0.5-1mm gap setting, compared to the ERM ones which looked a tad on the looser side of the "spec".  Face stops all looked good still.  No stops were touching (we didn't expect to find any touching since the vent lifted the QUAD back up).

- Carefully unlocked the barrel stop nuts and adjusted the stops to be ~0.75-1.25mm for the top 4 stops and 1.25-1.75mm for the bottom 4 stops.  Note, the way I gauged this was via the usual technique of "by eye".  I tried to do the tap-optic-and-count-turns-of screw method on a few of them to confirm that my by-eye technique seemed calibrated. (On a 1/4-20 EQ stop screw 1.27mm of gap setting is acheived with 1 full turn of the screw, so I did 1 and a quarterish turn to get to ~1.5mm).  It is impossible to use a tool on one of the top barrel stop screws (the top left), so I had to attempt to turn it a smidge with 1 finger.  Carefully relocked the nuts.

- Inspected the optic HR again - still looked the same. 

- Attempted to N2 dI blow (~10psi) to discharge/remove particulate - not alot of movement observed in ~1min.

- Removed tools, took a few pictures, exited chamber.

- Took quick V and P TFs - both looked healthy as expected.  (ISI had to be redamped for this since I tripped it.)

- Door went on, pumpdown began, as per alogs.

Particle counts from the hand-held particla counter were 30 or under in all sized particles sampled before and after the door removal.  I sampled at the door interface near the central bottom of the door opening.

I did the subtraction between HAM2 and HAM3 ISI channels.  I have attached the cartesian results for Z, which was the most interesting. The first plot attached is with sensor correction ON. The second plot attached is with sensor correction OFF.  The residual with sensor correction OFF shows nothing at 0.66 Hz.  

It might worth to have another look at the coherence between the output of the FIR filters of HAM2 and HAM3 (someone one site will have to do it, I can't access those remotely, thanks)

Distinguishing glitch and operator initiated actions in PIT and YAW signals:

  We  can distinguish the glitch and operator actions by looking at their spectral signatures.   A glitch would cause a rise in spectral amplitude right across the entire frequency range.  This would then appear as a white line running vertically (across all frequencies) in the spectrogram.  Where as an operator initiated action would have a subsequent suspension damping motion at low frequencies (only). 

   We can see examples of both in the PIT spectrogram.  There are no glitches in the red trace (the spectrogram for that is in bottom panel). This was after about 7PM and folks had already started using the BS oplev for damping.  So their initial alignment efforts show up as small steps with an associated low frequency spectral signature. 

    The blue trace has the classic glitch related signals showing up in pitch.  They can be seen starting at 1.3 hrs and going on till 1.4 hrs.  I dont think anyone was using the IFO at that time.  Since the BS oplev is used for local damping continuously, it is likely that the gliches kicked the optic and caused the activity we see around that time.

  The picture is more messy in the case of YAW as we can see from the blue trace and its associated spectrogram (middle panel).  The yaw signal seems to be continuously affected by the glitching however the event we saw in pitch at 1.3 hrs can also be seen in yaw.  Once again there is no operator related activity in the blue trace while the red trace shows some steps which have an associated low frequency spectral signature (bottom panel).  I concluded that they were associated with the initial alignment activity which was going on at that time.

I looked at whether the improvement in the laser quality has resulted in an actual improvement in the BS local damping.  There is a tangible improvement in YAW.

1) The Spectrogram of YAW motion shows that the injection of broadband noise into the optic motion in YAW due to glitching has disappeared after the swapping of lasers

2) the Coherence between the witness channel and Oplev channel in YAW shows that we can now extend the servo bandwidth to about 10Hz reliably.

3) The spectrum of yaw motion dropped by a factor of two in the range 1 to 20 Hz. This probably has nothing to do with the laser per se.  Probably the pier motion decreased between the two data segments.

Performance check after a week of operation

    To see if the laser is still operating safely within the glitch free region, I checked the 1s trend over the past two days.  The laser power has a slow drift of about 1% in a day.  This is probably a LVEA average temperature related effect.   The long term spectrum shows a 1/f shape down to 10^-4 Hz.

And to see the broad band noise I looked at raw signal over the past four hours (256 samples/sec)

The 4hr stretch of raw data spans a period when the oplevs were not used for first 1.4 hour stretch and then were turned on.  We can see the suspension resonances damp in the witness channels.  

The spectrograms show that there is broad band noise in the optic motion, but it is not due to the laser glitching. 

The top panel shows the laser spectrogram and it does not show any broadband noise.

Conclusion:

     The laser is performing well, without glitches.   All the action we see in the Pitch and Yaw is associated with either human intervention or lock loss events which have kicked the optic.

After looking at the oplev spectra with the OL damping loops on and off, I turned down the yaw gain from 650 ct/ct to 500 ct/ct to reduce the amount of extra noise injected between 1 and 10 Hz. The pitch gain is still 300 ct/ct.

In the attached plot, blue is the spectrum without damping, and red is the spectrum with the new damping gain.