Damping Stronger

With the help of the SUS folks, I increased by a factor of 3 the gain on the quad yaw and vertical (both M0 and R0 on ITMY and ETMY).  I also added 0.45Hz boosts to L and T for the transmon damping.  All of these changes are aimed at making sure that the ISI does not see sharp resonant features from the suspensions.

HEPI Tripped, cavity misaligned

I started the evening with the PLL unlocked, and the cavity badly aligned.  The cavity alignment problem came from the HEPI, which had tripped and thus let go of its 1M count RZ offset.  It turns out to be surprising difficult to restart HEPI without the watchdog tripping;

1. remove the RZ offset (set gain to zero)
2. open all filter inputs
3. clear all filters
4. set output gain to 0.05
5. close all filter inputs
6. slowly ramp output to 1
7. set 60s TRAMP on RZ offset
8. restore RZ offset (set gain to 100)

Or maybe we should just consider making the WD less sensitive.

Slow Controls Don't BURT, CM settings wrong (again)

The PLL was not working because the CM board was not set properly.  The compensation filter was off, and the boost was 1.  I guess these should be {on, 0}, or at least it works like this.  Similarly the PDH CM board had the common option on, which made it not work either.  We should really find a better solution.

Locking Well, small power fluctuations

After fixing these problems, and tweaking the alignment with the ITM and ETM, the cavity locked and was very stable.  We should check the state of the ISIs during this time.

After a false start wich for some reason tripped the watchdogs, I managed to start the driven tests on the ISI around 12am local time.  The HEPI was also tripped... I'm not sure if this happened before the ISI tripped, or because it tripped.  Please check filters and switches on the ISI isolation filter banks, as they seemed to be in an odd state.

These are some reference data from a long lock on the weekend.  There are 3 hours of continuous lock between 14:00 and 17:00 UTC (2012-07-08).  The long locks show a full tidal cycle; 1450 counts on the BOSEMS sensors ~ 580um ~ 50k counts of drive at the top mass.  It also shows very little residual L2Y coupling, and a little L2P (which I later tried to remove with an L2P coefficient of 3e-4).

Attached are plots of dust counts > .5 microns in particles per cubic foot.

The continuing tales of HAM6 purge have found the lonely ISI near the end of adventures ... Or is it‽  The dew point numbers seem to be hanging out at the -32 range for the most part. I'm going to turn the flow rate up to 15-20 liters/minute and see if this will urge another drop.

Thomas V. Szymon S. John W.

We installed the receiver enclosure fully with the viewport protector, reducer (temporary, used from ILIGO) and bellows.

During the transmitter enclosure installation, John noticed that we are extremely close to the bare viewport, approximately 3.75 inches between the enclosure face and the viewport.  There isn't enough room between the enclosure and the viewport to fully fit the standard protector, reducer and bellow. For the one arm test sake, a possible makeshift connection might be made. More work on this to continue.

Dave and Jim

The problem of the missing H1 test points was tracked down to a configuration issue in the core switch. The entry for the OPS VLAN needed to have the H1 subnet added to permit the UDP broadcast routing onto the H1 FE LAN.

Now low level test points diagnostics will show both H1 and H2 AWGTP processes. We discovered that h2pemeyaux was using a duplicated DCUID as h1sush34. We have powered down h2pemeyaux for now, and will give it new DCUID numbers during tomorrow's Tue Morning Maintenance.

Greg Mitchell & Hugh

Back on Friday a week ago, the SEI was floated on HEPI and then locked down, see aLog 3315.  Today we released the stops and adjusted the HEPI springs to level the Optical Table.  We are very close and basically ready for horizontal adjustments in response to IAS.

*** The Table remains free and is floating  ***

J. Kissel, P. Fritschel

After all the investigations into the SUS loop performance to find the source of the excess motion Pitch and Longitudinal motion at 0.43 (, 0.56, and 1.0) [Hz], Peter suggested perhaps it's merely the expected coupling between L and P, with the large not-yet-awesome input motion from the BSC-ISIs. So, following the same prescription used to generate the curves in G1200712, I produced the predicted QUAD test mass motion due to the measured (BSC8-ISI, ITMY) motion on June 26th, i.e. E1200668, in both L and P.

Attached are the results.

We see that indeed, given the (BSC8-ISI, ITMY) input motion, the predicted motion is on the order of 2.4e-6 [m RMS] and 5e-6 [rad RMS], with the expected first L and P modes at 0.43 Hz and 0.56 Hz, which have (modeled) damped amplitudes of 1e-5 [m/rtHz] and 2e-5 [rad/rtHz], reasonably consistent with results reported in LHO aLOG 3363, LHO aLOG 3302, and LHO aLOG.

There are several ways in which this model isn't perfect:
- The input motion is representative of BSC8-ISI (ITMY), which has been commissioned further than BSC6-ISI (ETMY), so one might expect the input motion to ETMY to be somewhat worse (It only has damping, No HEPI, No Level 0 Isolation Loops). Fabrice is working on getting me BSC6 data.
- I took the input motions in X, Y, Z, RX, RY, and RZ -- which are defined about the center (in X and Y) of the ISI, and at the lower-zero-moment-actuation-plane of ST2 of the ISI -- as direct inputs to the suspension point of the QUAD: (Y->) L, (X->) T, (Z->) V, (RY->) R, (RX->) P, (RZ->) Y, which means that the estimate for P does not account for the ~0.5 [m] lever arm between the ISI ST2 origin and the SUS point origin. See T1100617 for details (B. Lantz, C. Kucharcyzk, and I are working on getting the correct transform.)

The bonus attachments, relevant to the discussion, are as follows
- [2012-07-09_testmassmotion_bscinput.pdf] A plot of the motion used as input (identical to what is shown in E1200668)
- [2012-07-09_modeltf_*toP.pdf] The rarely-looked-at transfer functions between all degrees of freedom input to pitch in [rad/m] or [rad/rad].
- [2012-07-09_testmassmotion_P_resgndbudget.pdf] A break down of the predicted residual P motion from all degrees of freedom.

One VERY interesting revelation from these bonus plots: 
- T @SUS point transmission to P @ test mass becomes comparable to L to P in [rad/m] above ~1 Hz
- R @SUS point transmission to P @ test mass becomes roughly a factor of 10 greater to P to P in [rad/rad] above ~0.5 Hz
These mean we'll have to focus on reducing the T and R motion *just as much* as reducing the L and P motion.

HAM-ISI Unit #6 was balanced, and CPS readouts were within acceptable range, on 07/03 when we left it for long TF measurments. When checked this morning, CPS readouts featured an offset of approximately +/-3000 counts:

There is no drive/offset on MEDM channels.

Coil drivers were turned off. The CPS readouts remained unchanged.

CPS interface chassis were turned off, and then turned back on. The CPS readouts remained unchanged.

Dataviewer plots are attached. They show the drifting of the CPS readouts.

We experienced high temperatures over the last few days.

ALS Input Pointing QPD->PZT Loops

I started this fine Saturday checking the PZT alignment loops while JeffK measured SUS TFs.  The idea was to make sure that the loops were fast enough to ensure that sub-Hertz alignment loops would not be bothered by sluggish PZT response.  I found all of the loops in good working order with UGFs between 3 and 10Hz.  While I was there I added cut-off and boost filters (loops are still unconditionally stable) and set all the UGFs a little closer to 10Hz.

SUS Damping

In search of something to blame for our large angular motion, much of which appears at 0.43Hz (the first longitudinal resonance), I measured the Transverse loop (side OSEM), which also has a resonance around 0.43Hz.  It wasn't doing much, so I broght it up to speed with the Longitudinal loop boost filter.  I also changed the cut-off somewhat, as there was very little phase margin for the highest resonance (near 4Hz).  The result was a much more damped T DOF, but not much else that was obvious.

Slow Length Loop

After figuring out that the PHASE and PDH fast monitor signals are switched in digital land, I was able to close a slow loop (< 100mHz UGF) which off-loads the VCO signal for locking the arm cavity to the ETM.  At the moment, the locking filter is in the SUS-ETMY_M0_LOCK_L filter bank rather than the ALS_EY_ARM_LONG bank.  This is because ETMY_M0_LOCK_L_IN1 is recorded at 2kHz, which is useful for making spectra (see below).

Calibrated Spectrum

By stepping the gain of the slow loop after a large output had accumulated (with the input switch off), I was able to modulate the length of the cavity without unlocking.  This modulation is visible in the signal send to the VCO for cavity locking, and in the ETMY M0 OSEMS, so I cross-calibrated teh VCO signal using 40nm/cnt as round number for the OSEMS (see fig 1).  This gave 0.8nm/cnt for FMON, which might be 40kHz/V for the VCO if I got all of my conversions right... not so far from the 100kHz/V I would have guessed.  I made 3 spectra from locks separated by ~1 hour, all of which overlap nicely (see fig 2).

Lock Stability

The main threat to lock stability was a large Long -> Yaw coupling that would misalign the cavity as the slow length loop pushed on ETMY_MO_LOCK_L.  I fixed this with a small element in the drive align matrix (L2Y gain = 0.0036), indicating that we will probably have this problem with all of the suspensions just due to small magnet strentgh mismatches and BOSEM misalignments.  With this in place, the cavity will stay locked for hours with ~10% power flucutions (see fig 3, 4).  For reference, I include the alignment slider values in fig 5.

The EY ISI was also tripped.  I reset it, so we have damping, but I don't know the secret handshakes for turning on the isolation, so we will live without.