This message was sent to LHO-all at 13:46:

All,

With deteriorating weather conditions, personnel are advised to leave early today, especially before it gets dark and temperatures fall. Please exercise extreme caution with roads, traffic and weather.

Best Regards,

Jeff

--

Jeffrey D. Jones, Operations Manager
LIGO Hanford Observatory
P.O. Box 159
Richland, WA
U.S.A.  99352

phone 509-372-8136
http://www.ligo-wa.caltech.edu/

Using the optical path distortion measured by the HWS (provided by Aidan, see also 46127 and 46888) I simulated the mode content at various ports in a dual recycled Fabry-Perot Michelson interferometer. The simulation is done with MIST, using Hermite Gauss modes up to order 10, and locking the interferometer using simulated error signals. 

Only the optical path distortion in the ITM is included, there is no deformation of the HR surface.

Each of the attached plots show the distribution of power into each modes, assuming 26 W of input power, 60ppm or round trip losses per arm. The orange traces are there for comparison, to show that in a ideal IFO, all power is in the fundamental TEM00 mode.

Interestingly, the point absorber seems to create some 9MHz sideband power in modes of order 9 at the AS port, which we believe are the culprit for the high RF9 modulation noise coupling.

[Aidan, Danny VDH]

In order to determine how the H1ITMY mask should be used, I wanted to determine how much CO2 power was currently used at different power levels. To do this, I looked back over about 45 days worth of data and plotted the delivered CO2 power vs the power into the IMC. 

There is a significant amount of fluctuation in the applied CO2 power from lock-to-lock, perhaps 100mW. This means that the amount of thermal lensing will also vary from lock to lock by. We should look more closely at the functioning of the rotation stage.

The two plots show the same set of data, but the top plots had isolated the regions around 10W, 20W, 25W and 30W for clarity.

ITMY_ST2_CPSINF_V3 and ITMX_ST2_CPSINF_H3 both have higher than usual noise from around 1 Hz up

With the recent PSL chiller work going on (46939), I ended up adding 0 mL to the crystal chiller, as it seems recently filled. Filters look clean.

Addressed TCS Chillers (09:55 - 10:05 AM PST today/Thurs)

• TCSx Chiller:  Had level of 29.6 cm.  Filled it to 30.0 with 175mL.
• TCSy Chiller:  Had level of 7.6 cm.  Filled it to 10.0 with 750mL.  (mentioned this to TJ)

The CW injections appear to have crashed on Tuesday Feb 12 at 20:04:46 UTC. I have restarted them as of Thursday Feb 14 at 16:19:56 UTC (GPS 1234196414). See attached graph for turnon confirmation.

Tweaked alignment into the reference cavity.

    When I exited the enclosure, as soon as the air shower door closed, all HEPA fans and the make up air fan died
and the controller indicated that the air conditioning units were off.

    An observation I have noticed is that with the change made to the air conditioning set temperature, the heater
drive for the pre-modecleaner behaves quite differently - most likely because it no longers sits as high above
ambient temperature as it once did.  As a result it limits the time that can be spent in the enclosure to about
half an hour before a dance between the pre-modecleaner losing lock and the reference cavity losing lock.  As the
FSS is trying to re-acquire, the pre-modecleaner PZT voltage heads towards the low end causing a delay as to
when the FSS re-acquires because the pre-modecleaner drops out of lock.  All of which makes re-alignment an exercise
in patience.

Sheila, Jamie

• The reference cavity alignment has been drifting, the trans diode is around half of what it was when Peter King adjusted the alignment last week 46841  This level of transmitted power was low enough that we get an error on the ALS locking to get around this I set the low power limit on the fiber launch diode down, H1:ALS-C_FIBR_INTERNAL_DC_LOW went from 0.05 to 0.04.  This allows us to lock ALS, but Rick and Peter have talked about possibly tweaking the alignment in the morning. 
• On Friday Jamie and Rana found that they could use some DRMI ASC, the guardian now engages MICH, PRC2 and SRC1 in DRMI. This has been working well.
• We changed PIT5 settings in the guardian so that it will now be engaged with the dither line at 20.78Hz, which Jamie tested in low noise on Friday.  This is working OK when we have followed all the guardian steps manually, we were a bit confused by where all the gains are.  The guardian as it is worked once in ENGAGE_SOFT_LOOPS.  Caution might be required when the ADS gains get reset in CHARD_BLENDS and LOWNOISE_ASC. 
• We lost lock three times when trying to increase power because the of a problem with the ISS, the first attached screenshot shows what this lockloss looked like when we had the ISS second loop engaged.  We took the second loop engagement out of the guardian, but that didn't solve the problem which seems to show up as glitches in the first loop when we try to increase the power.  The ISS diffracted power was around 3%, which it was closer to 2.2-2.4%% before the chiller problems started.  We adjusted the REFSIGNAL from -2.03 to -2.05, which brought the diffracted power back, but the next time we tried to power up we still had huge glitches in the input power (3rd attachment)  
• We tried to lock the IMC only with the ISS on and power, that was fine. 

There was a small water leak at one of the (blue) plastic fittings at one end of the deionizer cartridge (gray cylinder in attached photo) in the Crystal chiller.

Re-seating and carefully tightening (trying to make sure not to over-tighten) the connection seems to have fixed the leak.

Topped off the water, installed the stopper, then re-started the laser.  All the servos locked on their own and the MC locked right away.

Seems we are back in business.

The PSL is offline again.  Seems the chiller tripped again.  XTALTEMP started rising about 5 minutes ago.

Yesterday Craig asked if there were any recent spectral measurements of the FSS mixer output - there weren't any.
This morning I set out to do the measurements.

    With the input modecleaner locked, a transfer function measurement was made (CG20FG9.jpg, data file has .txt
extension).  There was nothing unusual with the measurement.  A noise measurement was made (mxr.png, data files
are mxr0?.txt).  Whilst the measurement was done the spectrum was moving as if a sweep was being done, even though
the network analyser was physically disconnected (see DSCN0648.MOV).  I had noticed that the IMC MEDM screen
flashed the message that the IMC WFS were not centred.  Even with the IMC in the down state this behaviour did not
stop.

    Not long afterwards I noticed at the PZT monitor strip chart on the FSS MEDM screen was wall to wall black
and that reducing the common gain had no effect.  The mixer monitor signal was constantly greater than 1.2 Vpp.
I then remembered that work was being done on HAM2 and thought what I was seeing might be related.  However when
that work was completed, the behaviour remained.  I then noticed that the metal block over the PA85 was stone cold,
whereas it is normally warm to the touch.  A quick check of its output voltage indicated that it was almost always
close to zero suggesting a blown PA85.

    The spare FSS was deployed.  It locked readily enough, however for unknown reasons the common gain could not be
increased much beyond -6 dB without the PZT railing.  Clearly there is some difference between the two units,
although I seem to remember bringing them to the same hardware level 4 years ago.  The PA85 was replaced in the
original FSS, and things locked up straight away.  The PZT was not oscillating, gain sliders were restored.  The
transfer function with the repaired FSS is in PA85.jpg (data file PA85.txt).

    It was there I left things, since the input modecleaner needed to be back online by 08:30 am local.

    It is not obvious why the PA85 died.  One possible reason is due to overheating.  With the FSS located under
the PSL table not as much air gets blown over the PCB.  With the lid off the FSS box, the conducting surface area
is reduced somewhat.  Unfortunately accessing the test points requires removing the lid.



  Peter / Richard / Ed