Now that the ISS is back working after re-aligning into the pre-modecleaner, it makes sense to do a measurement.

The measurement looks better than the one performed on August 12th in that the hump out beyond 1 kHz is cleaner now than before.  The low frequency relative power noise appears to be a little better from 1-3 Hz.  One difference to note is that the diffracted light level is ~2% higher than before.  Also the first loop gain is lower at 8 dB versus 17 dB (old).  With the improved alignment, the power on the photodetector is ~10V versus ~8.6V.

Jameson, Nicolas

We spent some time today porting the L1 OMC Autolocker/Guardian to H1.

We changed the way it handles grabbing lock, it used to sweep the PZT with the loop open looking for a 00 resonance, we've changed it to sweep with the loop turned on, waiting for the transmission to trigger the loop. This makes the locking quite robust and fast.

We are currently skipping the fancy GigE camera 00 mode identifier, but this should be re-commissioned and used. Also, we can't test the violin mode detection because we don't have the full IFO.

So right now it is basically an automated way to get the single bounce beam resonating with the dither alignment loops on (or lower states if those are desired).

Kiwamu, Nic, Jamie, Lisa

After  peeking down the X arm and fixing the  ITMX isolation loops , the plan for tonight was:

1) re-establish the corner alignment after the X arm was locked and aligned today;
2) make sure that with this new alignment we have a POP beam;
3) re-lock PRMI on the carrier;
4) evaluate effectiveness of new BS baffles;
5) lock DRMI on sidebands

Status
------

1) DONE 
2) DONE
3) Not quite - With the new alignment, locking the PRMI on carrier was not as easy as it was last Friday. The power in POP is higher than before and POPAIR_B, currently used for PRCL normalization, was saturating (see plot attached, every time POP AIR saturates there is a glitch in the control signals). Kiwamu reduced the BBPD electronic gain by a factor of 10, but then the normalized signal became too noisy. So the current plan is to bring back to life the POPAIR_A diode, which, according to Kiwamu, is currently blocked by a camera.



Notable event:

* 6.15 UTC, Sep 4 - Earthquake - SEI and SUS didn't trip, but the corner optics moved like crazy for ~20 minutes

Sheila, Kiwamu,

We locked the infrared main laser to the X arm this evening in order to improve the alignment of the input poointing.

Here are some settings we used for future reference:

• REFL_A_RF45_I is used
• demod phase = 6.9 deg
• whitening gain = 12 dB
• stage 1 and 2 whitenings are on.
•  REFL_A_RF45_I(Q)_GAIN = 0.275
• FM3 and FM4 of LSC-XARM are used. FM3 = p0:z1, FM4 = z41:p1e3.
• XARM_GAIN = 0.2. This gave us a UGF of 80-ish Hz according to a kink point in a spectrum of the error signal
• Once it grabs a fringe, FM1 boost, p0:z3 can be engaged, MCL can be turned off.
• disabled all the notches in MC2 SUS INF in order to have stable loop.
• I could not bring the UGF below 40 Hz by reducing the gain. This maybe because of a phase mergin, or not enough supression or perhaps something else.
• SInce the UGF was higher than a vertical mode of SUS_MC2 at 40 Hz, the locking loop kept rinring up this mode. It is visible in the attached dtt screenshot.
• The X arm trans sum stayed at about 800 counts, seen by ASC-X_TR_A_NSUM

Jamie, Kiwamu

We tried engaging isolation loops in the stage 1 of ITMX ISI, but kept failing for some reason. In both robust- and high- isolation cases, we saw L4Cs ringing up at 10 Hz at the end of the auto-isolation processes and tripping the watchdog.

Checking each step of the guardian isolation process, we finally found that the instability was due to the X isolation loop. In particular, every time when it engages the 3rd boost, this makes the system unstable. Even though, we don't really know what the loop shape is for the X direction, we tried different gains in order to find a OK-stable gain. We ended up with a gain factor of 2. This seems to give us a OK-ish ISI performance in ITMX ISI. We did not try engaging the stage 2 isolation loops.

J. Kissel

Yet more measurements of charge -- I've taken two more data points on H1 SUS ETMY and one on H1 SUS ETMX. 

I managed to start and complete the measurement of ETMX exactly as the EX Ion pump was turned on and the arm was opening. Note, that the green laser had been injecting ~30 [mW] into the vacuum system since last night. The results show little-to-no charge, clustered around zero. We'll get a few more measurements over the next day to see how an open arm, with green light is affected. Remember, we didn't see much charge change between ion pumps valved in vs. valved out, or with green light for ETMX.
      P [V]       Y [V]
UL   42.6    41.6
LL   46.4    40.9
UR   40.3    20.6
LR   28.9    30.6

For the two ETMY measurements, the configuration has remained identical since Tuesday Aug 26, namely with the ion pump open. Indeed, as suspected, the three measurements over the past 48 hours show significant variation in charge, unlike with the pump valved out. I'm still waiting for Borja to get me the previous data in an easily digestible form so I can make a nice comparison plot over time, but for now, I just report the charge over time via the table below.
Pitch
       2014-09-02    2014-09-03    2014-09-03
        1937UTC       1550UTC      2339UTC
UL [V]    104          101           119
LL [V]    129         -5.51         -15.9
UR [V]    110         -22.4         -76.6
LR [V]    104         97.8          101

Yaw
       2014-09-02    2014-09-03    2014-09-03
        1937UTC       1550UTC      2339UTC
UL [V]    149          160          196
LL [V]    72          13.3         -13.1
UR [V]    13.6        -32          7.17
LR [V]    117         112          91.4

(Alexa, Sheila, Keita)

• X-arm locked on green (see Keita's alog 13740 for more detail on alighment).
• We had to realign Green REFL B on ISCTEX.
• We plugged the 24.407079 MHz RF oscillator source back to the RF Amp, with the demod phase at 120.6deg. The ifr was set to some wrong value, and we didn't bother resetting it for now. For reference, the HIFOX configurartion was Mod Freq: 24.407363 MHz, Demod phase: 120.7 deg (alog 10227).
• COMM beat note was well aligned on ISCT1, we measured 1.5Vppk.
• DIFF and COMM demod controls cable was plugged into the wrong slot in the back of the concentrator. (We moved from slot 3 to slot 1).  This is now consistent with the pull list.
• There is a LO mon error for COMM demod. Will investigate tomorrow.

Now they output negative signal when there's light. That's opposite of what I remember, and that's opposite of ITMX baffle PDs.

This is to get a good reference for the corner station alignment.

Prcedure:

Align TMSX, then ITMX, then ETMX, using arm baffle PDs.

Then steer PR3 to get the green transmission in ISCT1.

Then align IR light using PR2 and IM4/IM3 to the arm.

Results:

Green beam locked to the arm, and the green beam was steered to the right location in ISCT1 using PR3.

Good alignment slider values are:

PR3 slider offset used to be (P,Y)=(-279, -80) until this morning, now it's (-245, -178.9), the difference is (34, -98.9) urad.

Due to ITMX motion, the ITMX number might be off by a few urad, and the errors in PR3, PR2 and IM4 should follow ITMX via some ABCD matrix.

The message is still the same as before (without TCS, the mode matching to the OMC in single bounce is expected to be worse for ITMX than ITMY), but for posterity I add here the alamode files I made with the mode propagation from the IMC to the AS port for ITMX and ITMY single bounce configurations. The IO parameters come from previous measurements and models that Paul did. 

~1100 - 1200 hrs. local
Valved-in IP12, valve-out X-end turbo, dumped GV20's unpumped gate annulus volume into pump cart and opened GV20  

~1200 - 1315 hrs. local 
Valved-in IP1, IP2, IP6, valved-out YBM turbo, valved-out XBM turbo, dumped GV7's unpumped gate annulus volume into pump cart and opened GV7

08:41 Hugh to HAM5 to unlock HEPI
09:07 Fire department on site
09:24 Jason starting optical lever work
09:43 Hugh out of LVEA
10:08 Betsy and Travis to quad test stand
11:30 Jeff K. to end Y to check status of illuminator
~13:00 Karen to mid Y
13:30 Fire department on site
13:40 Karen done at mid Y
13:50 Richard and fire department to LVEA
14:05 Richard and fire department out of LVEA
15:00 Safety meeting

- X arm opened (WP 4826)

At the request of local commissioners, I have modified the SUS guardian code to go back to handling the setting of alignment offset values for the ALIGNED state, and have re-introduced the MISALIGNED state which sets the alignment offset to saved misaligned values.  This all was originally in the SUS guardian code, but was removed at LLO due to precieved problems with the SUS guardians handling the offsets.  The LHO commissioners, on the other hand, prefer the SUS guardians to have separate ALIGNED and MISALIGNED states.

SUS guardians have not been restarted yet.  Only SR2 for testing.  We're waiting until after the arm alignment tests are done.

NOTE: ALIGNED and MISALIGNED offset values MUST BE SAVED in order for the SUS guardians to restore to them! This is the big change by going back to this configuration.  When the SUS guardians were not touching the offsets, there was no worry that they would accidentally be reset.  Now that they are being set by guardian, we have to remember to always save the offsets appropriately after tweaking them.  Forgetting to save them could result in the current alignment being lost if the suspension trips or the alignment state is cycled.

As a bonus, the SUS guardians will use the notification USERMSG to notify you if the alignment has been changed and not saved.

Here's the current SUS state graph:

This is all just a stop-gap until we get a better comprehensive solution to the alignment offset problem.  This will likely be discussed in the next SYS meeting, on 9/9/2014.

I noticed that the anti-whitening filter for the LF signal of the resonant RFPDs were all consistently inaccurate. So I fixed it.

before: zpk([2.4], [0.24], 1, "n")

after: zpk([2.4], [0.2], 1, "n")

I did this for all the resonant RFPDs, including REFL_A, REFLAIR_A, POP_A, POPAIR_A,  ASAIR_A and IMC_REFL. This seems to have fixed the issue of ASAIR_LF going below zero watts.

I have updated the GUARD_OVERVIEW screen to reflect the addition of the new node OK bits.  The change can be summarized with the new legend.  Note the third indicator on the right:

The last indicator will be green if the node is OK, or orange if it is not.  This change has been propogated throughout the GUARD_OVERVIEW screen:

Note that most all SUS and SEI nodes are OK, while we still need to set NOMINAL stages for the ALS and IAS ("initial alignment system") nodes.

The white panels are nodes that are currently being commissioned, and should be available imminently (the H1 "IMC" node will be renamed to "IFO_IMC" to match LLO).

Unlocked the WHAM5 HEPI and then ran Range of Motion measurement.  1mm for most DoFs, V1 0.9 & V4 0.8mm.  Elected to not run linearity test, looked good in April.  Attempted to run through commissioning scripts to close the position loops but there is a bad L4C and I'll need to replace that and rerun the transfer functions.

Meanwhile I updated the Cartesian position targets to the more recent stopped time, although these saw only small changes since I updated the targets in July.  And, I've driven the outputs (Cartesian basis in the Isolation filter section) to the target positions.  The rotational DoFs are all within a few 100nrads and the translationals are within a few umeters.  Feel free to tweek the OFFSETs on the Isolation filters if further tuning is needed.

I did some math to figure out how much ITMX, ITMY and BS may have been moving (in a frequency band of 0.1-1 ish Hz) in their angles according to fluctuation of the DC light observed at the dark port when the Michelson was locked.

(Summary)

Wednesday night (August 27th)

• The dark port DC (ASAIR_B_LF) flucutated by 16% of the bright fringe when the Michelson was locked on a dark fringe.
• ITMX(Y) may have been moving by 11 urad or 22 urad in peak-to-peak.
• BS may have been moving by 5.7 urad or 11 urad in peak-to-peak.

Friday night (August 29th)

• The dark port DC (ASAIR_B_LF) flucutated by 1% of the bright fringe when the Michelson was locked on a dark fringe.
• ITMX(Y) may have been moving by 2.8 urad or 5.6 urad in peak-to-peak.
• BS may have been moving by 1.4 urad or 2.8 urad in peak-to-peak.

(Some math behind it)

Suppose the Michelson is locked on a dark fringe. If an ITM is misaligned by Ψ, this introduces a displacement and tilt in the reflected beam with respect to the one from the other ITM at the BS. The displacement is x = 2 L Ψ and the title is ϑ = 2 Ψ where L is the distance from the BS to the ITM. So we get a small amount of 01 or 10 mode at the dark port on top of the 00 modes. Since the effect on the resultant 00 mode in its power is proportial to 4th power of the displacement and tilt, we assume the 00 mode to vanish because of the locking loop. The only residual we obtain at the dark port is the 01 or 10 mode whose field can be written as

E₁₀ = 1/sqrt(2) ( x/w₀ + i * ϑ / ϑ₀),

where w₀ is the waist size and ϑ₀ is the divergence angle respectively. A factor of 1/sqrt(2) upfront comes from the BS reflection. If we plug the definition of x and ϑ into the equation, we get

E₁₀ = sqrt(2) ( L/w₀ + i / ϑ₀)  Ψ.

Squaring the above, one can get the dark port power as

P = 2 ( (L/w₀)²+ (1/ ϑ₀)²)  Ψ²

Note that P is already normalized by the input beam power or equivallently the bright fringe. The Rayleigh range of the beam around the BS is roughly 210 m (if my math is correct). This gives a waist size of 8.4 mm and divergence angle of 40 urad.  The ITM-BS distance L is about 5.34 m where I averaged out the Schnupp asymmetry. So the dark port power can be now explicitly written as

P = 1.24 x 10⁹  Ψ²

This is the equation I used for deriving the numbers listed at the very top.

For example, if one wants to explain a 16% DC light fluctuation observed at the dark port by an angle deviation in ITMX(Y), the misalignment should be Ψ = sqrt(0.16 / 1.24 x 10⁹ ) = 11.4 urad. In the case of the BS, the effect gets twice bigger due to the fact it affects both X and Y beams at the same time in a constructive manner.