Summary of the activities from the last night:

• The main PSL light was locked to the X arm. The servo needed some tune-ups.
• Subsequently, IM4 and PR2 were aligned to the new ITMX angle while keeping the infrared locked on the X arm.
• The in-air POPAIR was realigned again because the new alignment let the POP beam fall off from the diodes.
• I confirmed that the PRMI could still lock under this new alignment. The RF18 build up in POP was 150 uW at highest.
• I let the simple Michelson freely swing. This is a part of the modulation depth study.

Below are some details:

(X arm locking)

The PSL light was locked to the X arm by feeding the signal back to MC2. This configuration gives us a situation where we can steer IM4 and PR2 such that the input pointing matches the cavity axis of the X arm. In prior, I moved the bounce and roll filters in MC2 from ISCINF to M2_LOCK_L such that the notches are applied only to the M2 stage. This is a suggestion from Ryan of LLO in order for a HSTS suspension to avoid ringing up the modes without sacrificing the length control bandwidth. This seemed to help the stability a lot. I did not see a too-prominent peak at these bounce and roll frequencies when it was locked. Good.

I followed the procedure described in a previous alog (alog 13747) except for the sensor. This time I used ASAIR_RF45_I instead of a REFL detector because ASAIR seemed to have a larger signal level without extra whitening amplifications. Also I tailored the demodulation phase to -98.6 deg which maximized the in-phase signal. The LSC gain needed to be 0.01 in this case which gave a UGF of 50 Hz. Measuring the open loop transfer function, I found that the phase margin at around the UGF was about 10 deg or so. So I put a lead filter in FM5 of LSC_XARM to bring the phase up by approximately 30 deg around the UGF. The measured open loop with the lead filter on is attached below.

Though, I still don't understand why the phase had been so bad in the first place. According to the digital filters we have, the phase between 40 and ~200 Hz should be about 90 deg as it falls as 1/f. But the open loop looked falling as 1/f².

(POPAIR realignment)

After I touched up IM4 and PR2 (mainly in pitch), I could not get reasonable signals from both POPAIR_A and _B at all. I went to ISCT1 and checked the beam in the path. Indeed the beam was off from both diodes. Similarly to the other day (alog 14055), I could not precisely evaluate the beam position on the top periscope mirror. The beam was too high on the bottom periscope mirror while the horizontal looked centered. I steered the top periscope mirror and realign the down-stream again. Also, I moved the POP camera position to a point close to the last steering mirror in order to get a bigger beam image.

After the realignment, I did not see an apparent sign of clipping in the POP beam image. Good.

(Michelson free swing)

See the attached below:

Note that the incident power on IMC at this point was 10 W.

Daniel and I have found that the optical lever sign convention for ETMs and ITMs was changed in May/2013, and now it's opposite of what I remember.

I'd like to know why it is/was a good idea.

Right now, the dot on the screen goes up when the OL beam goes down.

The circuit breaker for the motor starter on Supply Fan 5 was replaced. This fan is the cold deck fan for the OSB lab area.  The breaker failed to turn on after shutting it off for greasing of the fans.  This is an odd failure for a Circuit breaker but not unheard of.

The in-air cable for the Picomotor (PM5) was pulled.  Labelled H1PSL-ISS_PM5.  Goes from HAM2 flange D6-F12 to Picomotor controller #5, channels 5-8.

This Picomotor steers the beam before the mode matching telescope to the ISS photodetector array.

See D1002873 for flange nomenclature.

Work permit 4868.


Fil, Peter

The x1work computer has been rebooted following patches for the bash security bug. It hung on reboot, and shows a tendency to not want to mount partitions in a timely manner.

New software:  A new version of root 5.34.00 has been installed as the default which has the python interface enabled.  Also a new version of gds tools, branch gds-2.16.12.2, is installed as the default for testing.  These software packages are for Ubuntu 12.04.  

For the past few days the ISS actuator has been swinging around more than it should.  This was remedied by adjusting the
REFSIGNAL slider.  This setpoint indirectly sets the power incident on the PMC.  in some sense there should be no reason
to change the setting unless the power out of the laser has increased or decreased.

The REFSIGNAL slider was adjusted from -2.03 to -1.98.  Which implies a 2.5% decrease in power ((2.03 - 1.98) / 2.03 x 100).
Prior to that the output power of the laser only decreased by less than 1%.  The power transmitted by the PMC varied by ~2.8%.
The reference cavity transmission decreased by ~14%.  We already know there is a drift in the optical path to the reference
cavity.  The ISS railings are due to fluctuations in the PMC transmission.

We should examine the performance of the PMC more closely to see if we can decrease the power fluctuations out of the PMC.
Alternatively we can diffract more light to compensate for the drifts in PMC transmission.

model restarts logged for Wed 24/Sep/2014
2014_09_24 09:41 h1hpibs
2014_09_24 09:41 h1iopseib2
2014_09_24 09:41 h1isibs
2014_09_24 13:41 h1fw0
2014_09_24 14:27 h1fw1

restart of h1seib2 after unexpected crash. unexpected restarts of h1fw[0,1]

Looking at the dark port camera, I found that the infrared beam looked clippy and also off from the center by half of its beam size toward right in the camera view.

Then I found that the HAM5 had been tripped most of the time today. I untripped it. It looks like GS13s triggered the watichdog.Untripping the HAM5 ISI steered the beam toward the center. The ITMX reflection still looks bit off toward right, and the ITMY is apparently too low by half of its beam size. The attached is the python plot of the trigger event.

Keita, Sheila, Gabrielle

• We have a single shot beam from TMSY onto ISCT1, with 10uW of light, we have a beam from the ITM in the end station, and we have a second beam from ETMY on ISCT1. 
• Positive pitch is in the opposite direction on the ETMY alignment slider than on the TMSY alignment slider (I believe that TMS is the incorrect one).
• There seems to be a mix up with the baffle PD cabling.
• The ALS Y GigE camera has a softaware problem: the exposure cannot be changed from 2168317875, even though auto exposure is off.

Now, in chronological order:

result of TMSY to IMTY baffle PD search:

Based on D1200657-v4, (assuming the view shown is looking at it from the BS), this does not make sense with the arrangement of baffle PDs.  These votlages are low compared to what we see on the X arm, so we suspected that this was a second bounce or ghost beam, however, they do not move when the ITM or ETM are moved, so they are not reflections off of those optics.  If we think that if these are the real beam, the baffle PDs are mislabeled somewhere, so we used the TMS suspension alingment sliders to try to figure out which PD is which.  (Unfortuately, the TMS alignment slider also seems to be wrong.)

Based on our reinterpreation of the labels, we thought that the beam should be roughly centered on the optic when TMS is at -35 PIT, -31 Yaw.  However, we saw no sign of our beam at this location, nothing on ISCT1 and nothing returning to the ETM when we scan the ITM.  Keita trended the old values, and we saw the beam go by on SRM when he restored them.  Gabriele and I went to ICT1, and found a badly clipped beam by exciting the BS.  Later Keita and I returned and moved the TMSY alignment to get a somewhat better beam, with a TMS alignment of -87 PIT and -51.4 YAW and BS at 187 PIT and -258 YAW, we have 10 uW on ISCT1.  this was the same in the spring (alog 11296)  giving us some confidence that we really have the single shot beam on ISCT1.  (This is our first clue that the TMS alingment slider is wrong)

We went through the baffle PD game by moving ITMY and looking at the ETMY baffle PDs, using this TMS pointing which isn't necessarily centered on ITMY:

This seems to make sense, but the power is low again.  We think this beam should be roughly centered on the ETM with the ITM slider at 156.5 PIT -123 Yaw. 

Since exciting the ETM (around its saved alignment) and watching on the MC1 camera and at ISCT1 didn't show us any return beam, we redid the baffle PDs for the ETM pointing:

This beam also did not make sense with the baffle PD arrangement, or our interpretation of the actual PD arrangement based on the TMS alingment sliders.  This means that either ETMY or TMSY has a sign flip in the pitch alignment slider (our second clue): 

Once we understood this I decided that our ETMY interpretation of the cabling must be the correct one, since the TMS pointing that actually gets a beam through the optic is very different in pitch than the pointing we calculated based on the baffle PDs.  Using this information, our original TMSY centered pointing should have been -113 PIT, -35 Yaw.  Indeed, this pointing does result in a beam that doesn't look clipped on ISCT1.  I can also see two other beams on ISCT1 which come from the ETM, but haven't been able to easily align the arm cavity.  Although I see some fringing, the mutliple bounce beams seem to get clipped as I try to align them.  I think the next step is to start fresh with baffle PDs, now that we think we know which one is which.

Aidan. Greg.

Good news first:

Using the periscope, we got the green ALS beam aligned to the on-table irises that were pre-aligned to the HWS probe beam. This, nominally, mated the in-vacuum and in-air axes. To test this, we turned on the probe beam and recorded a frame with the HWS camera to see if there was a return beam. And ...

There was a return beam from ITMX. It looks clean (as clean as possible with the Hartmann plate on). The next steps are to remove the plate and

1. Tweak the position of the probe beam on the ITM using the shadow of the baffles as a guide.

2. Move the HWS along the optical axis until it is imaging the ITMX HR surface.

Bad news second:

The in-vacuum lens for the Y-arm Hartmann sensor is not correct (I'm 99% sure of this). It appears to be a concave lens when it should, in fact be a convex lens (PLCX-50.8-360.6-UV). There are two things that indicate this.

1. The green ALS leakge field is quite large (vs the X arm green beam which is quite small). The beams are designed to be small coming out of the viewports and should be, roughly, the same size.

2. The lens is close to the viewport and you can see objects through it. For instance, the SR2 triple, about 3 or 4 feet away) can be seen through the lens off-axis. It appears smaller when viewed through the lens. We I take a spare PLCX-50.8-360.6 (what should be in there) and look through it, objects that are 3 or 4 feet away look bigger.

So I'm pretty convinced the in-vacuum lens is concave when it should be convex. We'll continue investigating how occured (it looks like some typos in a design change have propagated through a few documents). The more important thing is what to do about it. We won't get it working this week, but it may be possible to correct this using additional in-air optics in, what Eric G has dubbed, a Hubble Space Telescope optical fix.

FYI: Livingston has the correct lenses installed in the vacuum system.

I rebooted h1digivideo2 to add the new green ITM cameras to the config.  This is the quickest way to ensure that the cameras will continue to work in the future after unintended/intended restarts.

Ran a first set of TFs for 3IFO-QUAD09. The undamped plots look OK (pitch is a bit off). The damped plots measurements do not match the model between .1 and 20Hz very well, for both the Main and Reaction chains. Will investigate the cause. Plots are attached.  

As Betsy noted in aLOG 14128 the second pitch mode shift is present as for the other 3IFO Quads tested to date. 

All files, plots, and scripts have been commited to SVN.     

Jeff and Andres finished the transfer functions of the 3IFO Q9 QUAD.  Attached is the TF plot compared to the other 2 3IFO QUADs.  Infact, this unit ALSO has the elusive 2nd pitch mode shifted up in frequency.  In summary, so far all 3 of the 3IFO all-metal QUAD builds have this "feature".

Continuing the HAM6 HEPI Trouble shoot.  Checked sensor readings against visual position and raange of motion.  2 vertical sensors readings where offset wrt their actual positoin enough to allow the sensor to touch its flag.  This had to be corrected so I did that.

This shifted the computed cartesian position.  I looked before and after the adjustments (Loops open all through out) and then adjusted the Target positions appropriately.

WHAM6 is back to Position control but without boost.

The V2 IPS continues to behave and I even jiggled the wires a bit this morning--Periodic maintenance: unplug & plug in cables repeatedly, fun!

QUAD 06 (Q6) Phase 1B transfer function plots are attached.   We had a hard time obtaining good coherence in the Transverse TF, so it is a bit hashy.  Will try again.  

Most notably is that, like Q8, the second pitch mode frequency is unexpectedly pushed upward on the main chain.  Recall, we never found the mechanism to fix it on Q8.  Interestingly, both the Q8 and Q6 assemblies are of the same batch of wires and are fresh builds, but by 2 different assembly teams, and on 2 different solid stack/test stand units.  Q8 is an ETM type of QUAD while Q6 is an ITM QUAD, but both main chains have the same pendulum parameters - both are detailed in the 'wireloop' model.

The Q6 data is plotted as QUADTST.