Elli, Thomas, Stefan

After Jeff redid the PR3 M3 P2P and Y2Y transfer function measurements, we designed actuation filters for high bandwidth feed-back to PR3.
We decided to use M3 on PR3, offloaded to M1 (top).

The filters we used are:
PIT PR3^-1: zpk([0.1+i*0.82;0.1-i*0.82;0.5+i*3.4;0.5-i*3.4],[0.5+i*3.02;0.5-i*3.02;11.1111+i*38.4258;11.1111-i*38.4258],1,"n")
YAW PR3^-1: zpk([0.2+i*1.23;0.2-i*1.23;0.3+i*2.95;0.3-i*2.95],[0.3+i*2.5;0.3-i*2.5;11.1111+i*38.4258;11.1111-i*38.4258],1,"n")

In both filters the design philosophy was to compensate the mechanical poles with a slightly lower Q digital zero,but such that we never run out of phase for unconditional stability. The resulting transfer function works as resonant gain, suppressing the motion on resonance.

Attached are loop transfer functions, both measured (red) and calculated based on Jeff's measurement times the applied filter.

The ITMx HWS is ready to take measurements.  I have left it off for now. 

The ITMy HWS SLED is clipping the periscope before entering HAM4.  I will adjust it when we have green light from ETMx again.

Jim, Hugh, Krishna, Fabrice:

we have been chasing problems in HAM3:

- one aspect of the problem is that the Z sensor correction doesn't perform well. A large peak at 0.6 Hz appears in the spectra, in all directions, when the sensor correction is ON.

- another aspect of the problem, related, is that there is low coherence from the ground seismometer to HAM 3 geophones. This is more a broadband effect.

- another puzzling effect is that the Z sensor correction makes X, Y performance better.

We have been investigating to find out whether this is a CPS sensor noise issue, a mechanical issue (rubbing, hitting, mechanical shortcut....), and/or a loop shaping issue.

Some comments and results of the investigation:

- page 1, the sensor correction is off, the ISI is damped, the coherence from ground to HAM3 is excellent.

- page 2, isolation loops and sensor correction are ON. The coherence drops at 0.6 Hz.

- page 3, the sensor correction is off. Coherence between ground to ISI is no good. But the coherence between ground and HEPI is good. So HEPI is likely not introducing the noise.

- page 5, I ran harmonic tests to see if something is hitting. We did not find anything obvious.

- page 6, I compare all units, in damping mode. HAM 3 looks fine.

- page 7, I turn ON the isolation on all units. HAM 3 still looks fine.

- page 8, I turn ON sensor correction on all units. The peak appears on HAM3.

- page 9, I turn off the Z sensor corretcion on HAM3. The peak is gone, but the X motion is much higher...

- page 10, I also turn ogg the Z sensor correction on HAM2, to verify it has no effect in the X direction for this "good" unit.

- page 11, I put HAM 2 and 3 vertical loops in high blend (Z, RX,RY), and turn off the sensor correction. HAM3 is fine.

- page 12, I turn on the sensor correction (X,Y,Z), HAM3 shows a slight peak at 1.2 Hz.

- page 13, I put Z back in low blend (01_28), sensor correction is still ON, HAM3 is still fine.

- page 14, I put RX and RY in low blend (250mHz), HAM 3 looks fine. So the problem shows up only with certain combinations of sensor correction and blend filters.

- page 15, I put RX and RY back in the standard 01_28 blend configuration, the peak at 0.6Hz is back...

- page 16, I repeat the test in page 14 (using 250 mHZ filters on RX and RY), the peak is gone again....

So at that stage I started to check loop shapes.

- page 17, I checked the blends installed. All seem fine. 0.6 Hz turns aout to be frequency where the CPS complementary filter crosses unity, but I think it's just a coincidence.

- page 18 to 22, I checked the open loops. Rx seemed to have a drop near 0.6 Hz. But the measurement was not repeatable, as shown in page 23 which looks fine.

- page 25, 26, I check the super-sensors. They don'y look nice at 0.5 Hz, but it may not be related.

Did not find anything abvious in the loop shapes, so back to sensor noise hunting:

- page 27, HAM 3 in damping mode. No problem in the local sensors.

- page 28, back to standard config (01_28 blends, and sensor correction...) , we can see the peak at 0.6 Hz in most local sensors.

- page 29, I put RX and RY of HAM3 in high blend, the peak now shows up at 1.12 Hz.

Summary:

the problem really depends on which blend filters are engaged for RX and RY.  Depending on the  blend filter used, the peak can show up at .6 Hz (using 01_28), 0.12Hz (high blend), or very little (using 250 mHz). THis set of blend filters however is too agressive at low frequencies. Despite the measurements we have performed today, it is still difficult to assess wheter this a a CPS issue, a mechanical issue, or a loop issue. We keep investigating.

Fabrice Krishna Hugh.

Krishna was suspecting that RX tilting on ITMY and the BS was impacting the HEPI Z Sensor correction results.  Sure enough, when checked it was most coupled on the BS Z to RX and next on ITMY HEPI Z to RX.  The other couplings, that is, HEPI Z to RY, and for ITMY both HEPI Z to RX & RY, where less by about a factor of 10.

The Measurement

HEPI Z is driven with a 0.001 to .1 band pass excitation (see attachment 1) looking for coherence with ISI Stage1 T240 X & Y.

The HEPI is in normal configuration, Lvl1 position loops but with sensor correction off.

The ISI Stage1 all dofs are put into high blend (T750) and its sensor correction is also off.

Once a baseline of the existing HEPI Z to ISI Stage1 T240 to RX & RY coupling is established as seen by the T240 Y & X, the HEPI is then Tilted in RX & RY with a smaller magnitude but similar bandpass to see the actual tilt of the ISI Stage1 when HEPI is tilted.  The Decoupling factor is computed by the ratio of the former to the latter: RX_z/RX_rx.  This correction goes into the IPS Align matrix.

Results

See attachment 2 for ITMY.  The left three plots are the TF data for inline tilt on ITMY, this is the Y direction caused by RX; the three right plots are for the crossline tilt RY showing on X. The first step is shown in blue: the area below 0.1 to 0.01hz with good coherence is our tilt coupling.  Notice on the right side, there is poor coherence and the TF magnitude is 10x smaller than the tilt in the Ydirection seen on the left side.

The green traces are the direct tilt measurement HEPI RX(RY) to ISI RX(RY).  Picking a few magnitude points from the blue & green traces in the area of interest and averaging the ratios gives the decoupling factor blue/green= 0.23/46(e.g.) == -0.0049 with the sign coming from the phase which are ~180 out of phase.

The brown trace (only on the left side) shows the reduction with the decoupling factor in the matrix (see last attachment) when the first measurement is repeated. (I failed to save the coherence for this but it was reduced just above 0.8 from the near 1 at the start (blue.)  This indicates there may be more improvement to be made but it will be time consuming and may not be worth it.  The improvement though is clear, about a factor of 10.

Time constraints (commissioners) prevented a brown results curve measurement for the Z to RY tilting but I have the data to calculate the ratio.  We expect the improvement to be minimal as the coupling is already low.

Rick and Dave:

We moved the MSR mac minis to EY and EX this afternoon to pair them up with their respective PCAL cameras via a local USB cable (procedure is https://dcc.ligo.org/LIGO-T1400755). The mac minis were returned to the MSR and reinstalled. The Y arm computer can ping the Y arm camera but image software does not connect. Rick will see if the camera/UT-1 are still trying to connect when he goes to EY tomorrow.

(Filiberto, Gerardo)
Installed two viewport protector assemblies on BSC9, ports G2 and G3.  Took the opportunity to inspect both viewports, they look good.
Installation included mounting an illuminator on port G3 and a camera housing on G2.
The camera is not connected, will revisit tomorrow.

Kyle, Gerardo, Bubba -> ~0930 hrs. local -> Removed BSC9 West door 

Kyle -> ~1350 hrs. local -> Started pumping BSC10 annulus 

Kyle -> ~1500 hrs. local -> Decoupled pump cart from HAM1/HAM2 annulus (Climbed on and around HAM1 and HAM2)

LVEA: Laser Hazard
Observation Bit: Commissioning  

07:15 Karen & Cris – Second cleaning at End-X
08:15 Jim – Testing BSC10
08:25 Cris & Karen – Back from End-X
08:33 Krishna – Going to End-X to shutdown BRS ahead of door removal 
08:57 Kyle, Gerardo, & Bubba – End-X door removal
09:00 Gerardo – Installing viewport protectors at BSC10
08:58 Richard – End-X to verify Laser Safe and to test interlock
09:03 Mitch – In LVEA west bay 
09:15 Richard – Transition End-X to laser safe
09:18 Cris & Karen – In LVEA for cleaning
09:45 Betsy & Travis – Going to End-X
09:49 Filiberto – End-Y taking pictures ESD in-air cables
10:08 Rick & Jason – Going to End-X
10:15 Filiberto – Going to End-X to drop off power supply
11:00 Gerardo – LVEA HAM1 & 6 to check vacuum comp
11:00 Doug – Working on HAM4 OpLev alignment
11:20 Gerardo – Out of LVEA
11:31 Vending machine delivery
11:37 Kyle – Back from End-X
13:15 Kyle – Pumping the BSC10 annulus at End-Y
13:30 Power cycle Video4 monitor 
14:05 Kyle – Start pumping BSC10 chamber at End-X  
14:15 Dave & Rick – Going to End-Y to work on cameras
14:43 Kiwamu – Cleaning up tools at HAM1 
14:49 Kyle – Disconnecting pump cart from HAM1
15:02 Kyle – Out of LVEA
15:30 Dave & Rick – Back from End-Y

F. Matichard, K. Venkateswara

On Tuesday (12/16/2014), Fabrice and I got an opportunity to test the ETMX ISI in different configurations. The wind speed was in the 7-12 mph range at EX. The configurations I tested were:

A) ISI Damped

B) ISI isolated with High (T750) blends. Inertial isolation happens only at frequencies above ~750 mHz.

C) Nominal LLO blend configuration. Inertial isolation happens above ~45 mHz.

D)  (C) + sensor correction using LLO filter.

E)  (C) + sensor correction using Rich's Z sensor correction filter and the tilt-subtracted super-sensor.

The first page of the first pdf shows the ground seismometer (RED) and the tilt-subtracted super-sensor output (BLUE) in displacement units. It shows factors of ~5 subtraction below ~50 mHz. The second page shows the T240 on Stage 1 under the different configurations. The following page shows the CPS and the final page shows the T240 RY.

Looking at Page 2, Configuration E appears to improve over D, roughly by factors of 2-4 below 0.5 Hz, while showing no excess amplification at low frequencies, as measured by the CPS. This is in agreement with modeling predictions described here. Unfortunately, I couldn't make a measurement in (E) but with BRS off for comparison, because someone walked into EX VEA and drove up the BRS amplitude.

Measuring this improvement interferometrically has not been possible using the ALS (green laser system). It is likely that ALS is noise limited in this frequency range as described here. Measuring it using the IR laser needs much more dedicated time which is not easy to come by.

So far, we have not tried using different blends for the inertial sensors. Some improvement may be possible by blending higher in X on Stage 1. But so far, it looks like BRS can improve ISI performance by factors of 2-5 in the 50-500 mHz range. Improving performance at the microseism might significantly improve detector robustness as seen during ER6 at LLO.

The other two attachments show the coherence between various sensors when the ISI was damped and when ISI was in the (E) state.

Secretary notes from BSC9 today:

• The chamber door was pulled by Gerardo/Kyle/Bubba.
• ~20 mins later, with the billowing C3 door cover on, I reached in and took particle counter counts of 30 - 0.3um, 20 - 0.5um, 10 - 0.7um.  A pretty clean sample.
• I reached in an wiped ~2/3 of the floor.
• Jim locked the HEPI.
• Jim locked the ISI.
• Travis, Jason and I went into the chamber.
• We attached the locking bracket to the ACB and let it swing back to it's natural hanging position, giving us a bit of room to work, yet not occulting the pcal camera view.
• We removed the vertical witness plate that was hanging from the bottom of QUAD structure.
• We inspected the ETMx-HR - We saw no dead-ringer particle that was a more obvious "scatterer" than any other particles on the surface of the mirror.  We also did not see any large bits of left over FirstContact or other debris.  We put the green lantern onto the suspension structure and counted ~5-10 particles per sq. inch roughly everywhere in the central 8" circle area of the mirror - higher than what we counted on the ETMy.  We spent a few minutes blowing with the deionizing N2 Top Gun blower - not much moved.
• We decided we should FC clean the surface given that the particle count level was higher than the ETMy level, even though we did not find the one we were looking for.  We also noticed that more particulate was floating around in the flashlight beams than we noticed at ETMy.  See my particle count data below, though.
• Rick took quite a few pictures of the surface in an attempt to capture the particulate condition - pictures will be available tomorrow when we post final results.
• We clamped the optic with the TFE rail tooling.
• We applied brush-on FC in the same manner as yesterday (thick short dabs/strokes, 3 coats) and put the PETG cap on.
• WE wiped more of the floor.
• We removed all of the extra tooling/blow gun/lights from the chamber and exited for the day.

We will pull the FC sheet ~9:30 am tomorrow and hopefully get the door back on by lunch.

The Ops Overview screen that shows the graphic representation of the IFO (OPS_OVERVIEW_CUSTOM.adl) had been previously unable to report individual suspension stage watchdog trips. According to the models, the discreet watchdog stages are "ANDED" into an EPICS channel called $(IFO):SUS-$(LOC)_DACKILL_TRIG_STATE which was the only conditional channel included for the Visibility Calculation in MEDM. This channel will never show it's alarm state unless all upstream watchdogs have been tripped therefore making said "trips" invisible in this overview, which has become a popular one with operators and others as well (imo). Discreet watchdog channels have been added and tested for BS and all Quad suspensions. This overview screen can now be relied on  for accurate reporting on the status of any suspension watchdog trips.

[Alexa, Mackenzie, Paul]

This morning with some free time on the IMC, we were going to re-run the alignment offset calibration procedure in preparation for a beam jitter measurement (a la aLOG 9870 and aLOG 10016). However, I found that the script failed when looking for the channel H1:IMC-WFS_SWTCH. The IMC_WFS_MASTER medm screen still has a button that should be controlling this switch.

Alexa dug around in the IMC_WFS_MASTER.adl file to find out what that switch was linked to and found that it actually calls the scripts "/opt/rtcds/userapps/release/ioo/h1/scripts/imc/mcwfson" and "wfsoff". 

Looking into the mcwfson script, we saw that the script sets the WFS gain to 0.25 (writing to H1:IMC-WFS_GAIN), and attempts to switch the missing channel H1:IMC-WFS_SWTCH to 1. 

Running the script from the terminal gives the error: channel H1:IMC-WFS_SWTCH not accessible. A quick caget gives the same result. 

Does anyone know where this channel went? 

K. Venkateswara

Due to the preparation for the vent at EX, the clean-room fans and lights are on which have increased the temperature in the VEA by ~1.5 deg C. Also, the cranes and sundry equipment has been moved around which has also changed the gravity gradients around BRS. Both of these changes have signficiantly changed the DC position of the beam-balance and it is almost out of range as seen in the attached graph. The Driftmon signal can be interpreted as the DC position of BRS.

I've temporarily turned the system OFF for the vent. Jim or I will turn it back on once conditions return to normal at EX.

Richard transitioned End-X to laser safe. 

Krishna, Sheila, Hugh, Fabrice:

We have been chasing  large amplifications at low frequencies (in the range of 10mHz to 30mHz) caused by the Z zensor correction of HEPI, which is necessary to reduce the Z to RZ coupling on Stage 1. It looks like the Z HEPI inertial isolation is causing rotations (RX, RY), that are causing tilt signal in the Stage 1 horizontal seismometers, that couple to X and Y as we blend at 45 mHZ, and then shows up into the cavity signal.

The problem was mostly  visible on the BS unit.  We convinced ourself that Z to tilt  was the problem by moving Stage 1 in high blend, which very significantly reduced the Mich amplification around 20 mHz (which exist only when the Z sensor correction is ON)

It seems that the excessive Z to tilt coupling in the BS was caused by off centered  vertical position sensors (up to 24000counts). We recentered them by applying  a HEPI vertical force. The Z to Mich coupling is now much lower. So I guess that the gain of the sensors was affected by the large offsets and thus creating excessive Z to RX and RY couplings.

Comparison with high blend configurations show that there is probably room to further reduce this coupling. We need the measure the Z to RX and RY coupling and apply corrections.

Evan, Alexa

Following the preparation described in alog 15524, we made a ringdown measurement of both the x- and y-arm. For each arm, we locked the IR beam and ran the wfs to ensure maximum build up. We then turned the wfs off, and switched the input polarity of the MC common mode board to unlock the MC quickly (based on LLO's alog 11727 the MC has about a 15usec ringdown time). We used the relfected signal at the AS port to capture the ringdown. We repeated this measurement 10 times to have ample data for our uncertainities. We also measured the "off-resonance" ringdown, by unlocking the arm and misaligning the respective ETM. All the data can be found in /ligo/home/alexan.staley/Public/Ringdown/EX(Y)data (these folders are then split into locked and unlocked times).  From this data we calculated the total loss:

X arm: 14310(100) ppm

Y arm: 15000(100) ppm

Based on the galaxy ITMY transmissivity (1.42%) this amounts to 800ppm of loss in the y-arm. Meanwhile, for the x-arm, the ITMX transmissivity is 1.39 % corresponding to a 410ppm loss in the arm. We are in the process of calculating the transmissivity of the ITMs based on our ringdown fit. Our code can be found in /ligo/home/alexan.staley/Public/Ringdown/proccess.py. The y-arm losses seems consitent with our scan measurements; however the x arm does not. These numbers are very sensitive to the transmissivity we use; so before we make an conclusion with this we should inprove our confidence in the transmissivity values.