Plots are found in SeiSVN: HEPI/H1/Common/2015-03-18_H1HPI_PumpControllerNoise.xml

The reference traces are from Monday 17 March 0900utc before the Tuesday Maintenance Accumulator Charging.  The current traces are 24 hours later after the charging effort (BSC2SupplyNorth not done.)

My assessment is this assessment is a bit too noisy and this didn't make much difference.  All the controller improvements have made things pretty good already.  The largest coherence was in the BS RZ which shows some broadband signal between 10 and 100mhz and that is reduced a good bit.  However, there are spikes of greater coherences in other dofs.  I would never say this is not worth doing.  Jeff may have some suggestions to better assess this is worhwhile.

I added the plots now.

Summary: The twin bumps at around 3300Hz comes from the OMC LSC loop, which has a 100Hz UGF.

Of course OMC length dither at 3300Hz should make some sidebands in the DC readout by design, but these twin bumps look really unnecessarily big.

We can reduce these by making the OMC length bandwidth much smaller.

Details:

In the attached, Red is with nominal setting (H1:OMC-LSC_SERVO_GAIN=60 and H1:OMC-LSC_OSC_CLKGAIN=6).

Blue is with 50% servo gain but with nominal dither amplitude (SERVO_GAIN=30, CLKGAIN=6), so it has half the open loop transfer function of red.

Green is is with nominal servo gain and 50% dither (SERVO_GAIN=60, CLKGAIN=3), so again it has half the OLTF of red.

IF the OMC length signal is sensing the true OMC length as opposed to just some noise that is not proportional to the dither amplitude, the OMC length control signal (middle row) for green and blue should be the same. But in reality they're 6dB apart from 8Hz and up.

Also you will expect that the OMC length error signal (bottom row) for blue and green have the same shape but different by 6dB, as the OLTF is the same but the sensing is 6dB different. That's only the case for f<8Hz.

So it's all noise for f>8Hz, and probably that's just  the noise floor of DC readout at 3300+-f Hz downcoverted by the demodulator (not dither) to f Hz, fed back to the OMC length, and upconverted by the dither back to 3300+-f. See the left column. Blue and green on the top left are the same because the sideband amplitude around 3300Hz produced by this mechanism is proportional to the product of the feed back gain and the upconversion gain (dither), the sensing part is independent of the dither amplitude.

In summary,

• OMC length signal is dominated by some noise, probably DC readout noise floor, not length fluctuation, from 8Hz and up.
• We can reduce the BW of the length control to maybe a few Hz to make the bump smaller and see if there's any ill effect on the DC signal.
• We can also filter out the feedback to make the width of the bumps smaller.

Later Dan will try some low BW filters.

(John W, Gerardo M)

Turned on the ion pumps at 9:05 am local time with both pump carts valved in, both pump carts were on the low 10^-06 torr

At 11:40 am I valved out the pump carts, but left the pump carts ON (connected to the annulus system and running).

Yeah :)

Obtained an alternate head to the charging hose.  Took down corner SEIs (Guardians to ready), turned Pressure servo to 0 psi.  Charged accumulator to 70psi.  Returned pressure servo to nominal and brought SEI back on via guardian.  Couple platforms tripped while deisolating and a couple (HAM2 & HAM3) tripped a couple times on the way back up.  All nominal now.

CDS
Filiberto moving SEI teststand from staging building to H2 building

Facilities
Bubba working by metal recycling container
Bubba looking at possibility of moving crates at mid X
Beam tube washing continues
Gerardo working on vacuum pumps by HAM1 and HAM2

3IFO
Corey working in squeezer bay
Other work on floor TBD

Operations
Suresh is giving training on optical levers at 11 in the large conference room

There has been an intermittent issue with the OMC_LOCK Guardian in which it runs a portion of code twice.  I've observed this most often in the OMC_LSC_ON state, where the LSC controls for the OMC are ramped up.  It's easy to notice, because if the gain steps are repeated for the OMC length servo the loop quickly becomes unstable and the cavity unlocks.  I've noticed this happen a handful of times in the past few weeks.  I've also seen lines of code in other main() function get executed twice, although I don't have screenshots to prove it.

Attached are screenshots of the OMC_LOCK log, from an event last week (March 14), and another tonight.  In both screencaptures, the OMC guardian enters the OMC_LSC_ON state, completes the instructions in main()...and then starts all over again.  In both cases the requested state was well downstream of OMC_LSC_ON, the guardian should not have looped there.  (And anyways, how does it repeat the main() function?)

I've committed the latest version of the OMC_LOCK guardian to the SVN, if experts want to check the code to make sure I'm not doing something heinous in the function calls or definitions.

In other locking notes from tonight...

• Kiwamu and I investigated the source of BS/SRM saturations, and a few locklosses, in the analog CARM handoff.  These saturation events had been variously blamed on the DRMI_ON_POP transition or the ASC loops turning back on, all of which happen in a short window of time.  Tonight we discovered it's due to the analog CARM handoff, specifically when input 2 of the REFL CM servo board is enabled with a large (14dB) input gain.  (This is the input of REFLAIR9I from the summing board to the CM board.)  When the input is enabled there is a big kick to the DRMI optics, and the MICH ASC loops (still engaged in this state) experience a large transient that rings for several seconds due to the inverse BS plant filter.  Screenshot of a typical lockloss is attached.  We've smoothed out the transition by putting a 10-second sleep in after the REFL_SERVO_IN2EN step.  No more locklosses from analog CARM.
• Violin mode damping is nearly finished.  There's one very tricky mode on ETMX that is a very problematic phase.
• We've continued to use Kiwamu's gains from Monday night to damp the ETMY and ITMX roll modes using AS_A_RF45Q, although I inserted a -100dB gain stage for ETMY to make the value more human readable.  Gain for ETMY_M0_DARM_DAMP_R is +40, gain for ITMX_M0_DARM_DAMP_R is +20.  These settings have not been propagated to the Guardian yet, I'd like to see if they continue to be robust after we touch up the ITM alignment to increase the recycling gain.
• We've been locking at 10W with the new DHARD_P filter.  Seems legit.

Dan, Keita, Kiwamu, Sheila

During a long, patient lock this evening I was able to measure the DHARD pitch loop down to 0.2Hz.  This follows Keita and Sheila's filter modifications to get some additional phase around the 3Hz UGF.  The attached plot is a record of the measurement (look at the RED trace), I have saved the xml file with the filename at the top of the plot.

The phase margin at the UGF is good (~40deg), and the loop does not cross unity gain at higher frequency.  There is almost a unity gain crossing at lower frequency, we have about 3dB of gain margin at 0.9Hz. 

Sheila, Nutsinee

This is the follow up from alog17278. I have attached five day worth of correlation plots between PEM wind channel, ALS control signal, and ground motion from two different sensors. Both ground and ALS correlate with the wind starting around 10 mph. The data point where PEM, ALS, and ISI are zeros and when ALS is constant has been removed in the correlation plots.

Todat we have two small changes to the initial alingment procedure:

there is now a clear history script that works for the arms, it can be used by clicking the button on the ALS OVERVIEW SCREEN or the end station screens.  

The X arm green transmission has been normalized, so now a transmission of 1 really does mean that the arm power is maximized.  

Also, as we have seen several times the OFFLOAD GREEN WFS doesn't really work for the Y arm. 

The status started reading low battery around 3:05 UTC 3/18.

Quiet day

09:42 Bubba running forklift outside by metal recycling container
09:45 Jody and Gary to mid Y, then transferring stuff to mid X
13:27 Hugh to BSC2
13:34 Hugh back

Scott L. Ed P. Chris S.

58 meters of tube cleaned today towards X-1-6 double doors.
Continuous monitoring of beam tube pressures by control room during cleaning operations.

Today we saw the second instance of what seems like a serious guardian bug, where the guardian executes the line of code above a return True statement, but doesn't return True and exit the state.  Screen shots of both incidents are attached.  After the first inicident (shown in the first attached screenshot) Jamie suggested that possibly the requested state could have been erroneously set to be the state LOCK_DRMI_1F.  

Today I am sure that the requested state was DRMI_ON_POP, so it should have changed states after returning true. 

Dan, SHeila, Jeff K remotely

The coil driver for ETMY L1 shut itself off this afternoon, this might have been while I was trying to measure the L2P coupling there.  We switched the rocker switch and things are fine.  The symptom was that we didn't seem to be drivig even though everything on the medm screen looked fine, the OSEM readback all had low values.  This is the same situation we had at End X a while ago alog 16511

This is one of the "errors" that we probably need better monitorinng of.  As a short term solution maybe we could add this to TJ's list, to check if all OSEM readbacks are low for a certain stage.