Using ~1/2 of the ITMY pitch bias range, the green beam gets back to the ETMY.

After enabling the ITMY HEPI + ISI, I scanned the ITMY bias sliders and looked at the ETMY face camera. The ITMY EUL2OSEM matrix has gains of ~5-10 (unlike the TMSY ?) and so the +/-15000 cts of the slider screen is enough to go full scale...and consequently, I tripped the watchdogs a couple times.

The yaw alignment was really good - the return beam to the ETM was nearly centered horizontally, but needed ~1/2 of the ful pitch range of the ITMY TOP stage.

With the illuminator off, it was easy to see the beam flashing around after the watchdog tripped. With the illuminator ON, but turned down to 0.5 Amps, I could see the stuff in the chamber as well as the green beam. Then I used the usual method of putting the beam on the 4 compass points of the ETMY cage and centering it on the mirror by averaging.

Moving the yaw slider to the right moves the beam on the cage to the right. Moving the pitch slider to the right moves the beam down. It takes +1000 slider units of torque to move the beam from top to bottom of ETMY.

The values of ITMY bias that center the beam on ETMY are P = +6300 & Y = +900.

So the ITMY alignment was off by ~6 mirror diameters =>  (0.210 m / 4000 m) / 2 = 25 micro radians.

Now that the beam goes both ways, the next thing to do is to align the ETMY to center the beam on ITMY using the baffle PDs as before. Then perhaps we'll be able to hear the cavity flashes if we can route the audio from the baffle PDs or the ALS green PDs into the control room.

The attached plot shows the control filter, the existing boost filter, and a proposed filter addition to the HEPI controls.

As we had at LLO, I think we should have a true integrator on the HEPI loops to compensate for long term drifts introduced by hydraulic pressure, thermal expansion, etc. so that the HEPI platforms  can be considered to be stable alignment-wise.

Also, why is there so much high frequency gain? It seems like the actuator watchdogs will trip due to acoustic noise or EMI with this kind of design. Perhaps a little low passing can be done without too much harm to the 10 Hz phase margin.

The SR570 (not 560) current preamp that we had been using since yesterday afternoon for channel 27 of the baffling diodes, ran out of batteries today at around 1330 today (so we know that a fully charged one will last just under 24 hours).

At that point it started producing glitches of ~30000 cts in channel 27 with a steady ~4 second period. Because of some grounding issue somewhere, it also produced smaller glitches in the other 3 channels. These glitches looked somewhat like a widly swinging green beam, so I spent a little while investigating the health of the various seismic filtering servos for the ETMY/ITMY before guessing that it was too regular to be mechanical.

Preamp has been switched back to the Melles Griot 13AMP003 "Large Dynamic Range" Amplifiers that the other channels are read out with. The SR570 on batteries was nicer than these; with a little bit of thought, I guess we could figure out how to adapt the ISC QPD readout board into one that can be used for this application (FET preamps, high transimpedance, some low pass fitlering) and then switched out to a lower gain one once we get into real interferometer locking.

After swapping, I used ezcaservo to remove the offsets on all the channels using commands like this one:

ezcaservo -r H2:PEM-CS_CHAN_27_OUT16 -g -0.21 H2:PEM-CS_CHAN_27_OFFSET -t 20

Daniel, Keita, Rana, Aidan, Dale, Dick

Using the ITMY baffle PDs, we were able to get the green beam from EY to ITMY today! The aLIGO beam tubes are able to transmit light.

We spent hours today trying out various ideas about how the beam might be missing, but in the end we found it by moving the EY Transmon Suspension.

The MEDM screen for the TMS had a range of +/- 15000 cts. In fact, the TMS has an 18-bit DAC and so its full range is +/- 2^17 = +/- 131072 cts.

With the current ALS table alignment, the TMS biases which give the maximum voltage on each baffle PD channel are:

				chan name

				P

				Y

				CS_CHAN_27

				-10000

				+2900

				CS_CHAN_28

				-69000

				+1200

				CS_CHAN_29

				-48000

				+1000

				CS_CHAN_30

				-46700

				+17800

We used these numbers to "triangulate". Then we used the ITMY spool cam to further center the beam on the ITM. It is not at all visible on the ITM surface, but can barely be seen on the gate valve behind the ITM as well as a little glint on the edge of the hole in the baffle where the cavity axis is. Our random search pattern initially just gave flashes of ~50 cts, so the new digital filters helped after all. Eventually, the signal on each PD can separately be made to saturate at 32768 cts as we align the beam onto it.

The final TMS settings for "good alignment" to the ITM are P = -16000 and Y = +9250.  Correction: there were some digital offsets in the 'test' filter bank. After zeroing those out, the new numbers are P = -42800 & Y = +59200.

Vincent has turned on the ETMY HEPI with low frequency boosts (although no integrators yet) so the pointing should be more immune to the HEPI hydraulic pressure fluctuations. Still need to fix up the ITMY HEPI. There's some seismic measurements going on overnight, but we can next align the ITMY to get the beam back to EY and then lock the green laser to the arm.

M. Barton & S. Steplewski

Today we characterized an advanced LIGO AOSEM (Serial Number 003, without an IR filter) using a 3-axis translation stage in the electronics shop. The voltage from the photodiode was recorded as a function of position in each of the three different axes. As shown in the attached graphic, the X axis goes through the circular coil (longitudinal to the OSEM) the Y axis is along the LED beam path, and the Z axis is vertical.

We found the expected sigmoidal curve by moving the flag in the longitudinal (X) direction, and computed a rough slope of about -19.4 Volts/mm in the central linear region. We also saw that moving the flag along the Z axis gives a flat response over about 1 mm of range, even when we moved to different X offset values. This means that the Z position can be slightly off-center and the OSEM will still work well as a longitudinal sensor. However, when the Z position of the flag is moved to a larger offset the longitudinal sensing is reduced, as can be seen in the first graph green and yellow curves. We also looked at the Y axis and found pretty flat responses, even when varying X.

Three versions running around LHO:

D080366-00
D080366-v1
D080366-v2 - taller than -v1

All are AR Polycarbonate, AR just means abrasion-resistant.

None found without DCC and serial numbers, though the big stash that's rumored to be here also not found (at 4PM on a Friday, go figure).

FYI: MSDS I found online, so not delivered with any of our orders, but still AR Polycarbonate, shows:
Softening Point: 150 - 160 °C (302 - 320 °F)
Melting Point: 220 - 230 °C (428 - 446 °F)

[Aidan, Jeff G, Thomas, Elli]

We've been running the HWS without the Hartmann plate in place to simply measure the position of the return beam from the ETM on the sensor. We have been yawing L1 on the ETM quad suspension with a 0.35Hz sine wave excitation of 5000 counts into H2:SUS-ETMY_L1_TEST_Y.

We measured the ratio of the 0.35Hz signals on the HWS to the excitation (in magnitude and phase). The intent is to move the HWS along the optical axis (or adjust F1) such that the ETM HR surface is imaged on the HWS CCD (if this is the case, then a yawing of the ETM HR surface should produce no motion on the HWS CCD).

With a ruler bolted next to the HWS the following measurements were taken. Smaller values of position are closer to the lens F2. The 18 degree phase delay corresponds to about 140ms time delay (most likely associated with recording images, analyzing them and writing HWS data to EPICS - which occurs at roughy 7Hz).

This implies that we need to move the HWS to the position 189mm to be imaging the ETM HR surface. Alternatively, we could move the lens F1 by apprxoimately 3.5mm (increasing the distance between it and F0).

• Keita and team projecting beam in EY VEA to check quality of green beam
• Eric craning seismic equipment by HAM4
• Apollo craning ISCT4 over to HAM2 area
• Keita and Rana at EY to install lexan cover on viewport and check baffles for beam clipping. Kyle briefly soft closed GV17 for this work, beam tube is again open.

I've put a loose foil cover over the illuminator at EY, where John took the Lexan out yesterday.  The official dust cover for the lexan slit that we do have, D0902791-v1, doesn't fit tightly over the slit, so flops back and forth leaving a gap, so not an improvement.  That part is on -v2 (D0902791-v2), which I believe will fit tightly, and modifying -v1 would be a good short-term fix.  However, the better plan is to beef up the dust cover into a part that fits into the slit, and thus holds itself in place, which can then be secured with a couple screws.  In the mean time, I was uncomfortable leaving the slit uncovered, and folded a piece of foil to prevent something small, like a screw, from falling through the slit and hitting the viewport.  I called John and talked it over, so he's aware of the very temporary solution.

Attached is an RGA scan of the Y-end taken this morning (RGA parameters are not optimized for current conditions but, rather, are left unchanged from initial scans for comparison purposes).   

I changed the programmed pump current value at which point IP11 "steps" from 7000V to 5000V from 5x10-4 amps to 1.5x10-3 amps.  Prior to this change the pump current was 1.4x10-3 amps @ ~8.5x10-8 torr.  The result is that IP11 is now at 5000V.

[Stuart A, Betsy B, Deepak K, Andres R, G2]

After taking an initial set of M1-M1 transfer functions earlier in the week on PR2 (HSTS), it was observed by Jeff B that somehow a magnet had become detached from the M2 mass (see LHO aLog entry 3157). 

Thanks to the efforts of the assembly team, this magnet was rapidly re-attached and left to cure for a period of 24 hrs. PR2 was re-suspended yesterday, and a small pitch offset corrected. AOSEMs were then adjusted to their final operating positions and aligned. The canopy/cover was fitted over PR2. Following this re-work, it was prudent to take another M1-M1 transfer function with damping loops OFF for all degrees of freedom, which can be found below (see 2012-06-21_1700_X1SUSPR2_M1_ALL_TFs.pdf). 

Damping loops were then turned ON and a further complete set of M1-M1 transfer functions taken overnight. All the transfer functions obtained have now been plotted against all other HSTS suspensions previously measured on both LLO and LHO test-stands (see allhstss_2012-06-22_AllHSTS_ALL_ZOOMED_TFs.pdf).

n.b. 
Yellow trace = X1 PR2 M1 (2012−06−21_1700) with damping loops OFF
Purple trace = X1 PR2 M1 (2012−06−21_2120) with damping loops ON

The transfers functions obtained again demonstrate good agreement with the model and the spread of all HSTS measurements obtained thus far. 

Power spectra have been taken with damping loops both ON and OFF for each stage (012-06-22_0800_X1SUSPR2_M*_ALL_Spectra.pdf).

Power spectra plots, with both damping ON and OFF have been produced, which compare LHO PR2 and LHO MC2 measurements (allhstss_2012-06-22_ALL_Spectra_Don.pdf and allhstss_2012-06-22_ALL_Spectra_Doff.pdf).

In addition, power spectra for specific degrees of freedom (L, P and Y) can be more conveniently compared across multiple stages (M1, M2 and M3) of the same suspension in the final plots found below (allhstss_2012-06-22_X1SUSPR2_M1M2M3_Spectra_ALL_Don.pdf).

A BURT snapshot has been taken of the current functioning environment "20120622_x1sushxts27_PR2.snap", which has been stored in the following directory:-
opt/rtcds3/tst/x1/cds_user_apps/trunk/sus/x1/burtfiles. This BURT snapshot directory has also been tidied to remove old or incomplete snapshots.

All of the above data, plots, scripts, and snapshots have been committed to the SUS svn as of this entry.

This should now provide sufficient measurements to complete Phase 1b testing of the PR2 suspension and allow it to progress to Phase 2 (chamber-side) testing.

Elli, Rana.   We connected a low-pass filter to the common mode servo input, to simulate the feedback response of the green laser inside the cavity. The transfer function of this loop confirmed the location of the pole and zero of the first boost filter. We removed common mode servo B and will change out some of the boost filter components in order to improve the servo transfer function.

This PDF shows that the RMS of the PD signals is dominated by 60 Hz + harmonics as we suspected. Unfortunately, it looks like we would have to notch out many, many harmonics to appreciably reduce the RMS. Perhaps we should use a low pass in combo with some comb filters?

We set up a CCD camera looking at ITMY and the entire baffle and some more, sent a green beam from EY, modulated its angle by using PZTs, and found nothing on the camera. No luck with the baffle diode, either.

It seems like the beam is not getting to the corner station at all.

One (or more) of three things should be true:

1. The ETMY is not pointing to the ITMY. The beam from ALS table is very close to retro-reflection by the ETM when TMS and MCL PZTs are in a neutral position.
2. Because of a factor of 20 reduction in angle in the telescope, we're not wiggling the angle enough (however I doubt this).
3. Mode matching is so bad that, by the time the beam reaches the corner, the beam diameter is 4m or something.

Tomorrow we should use HEPI and/or ISI to move everything by a milli radian or so in YAW.

The reason why I think we're already wiggling enough is because, when we wiggle MCL PZTs, I can see on the CCD camera monitoring ETMY that the motion is so big the beam falls off of the primary.  It's not impossible that this is all in translation and not in angle, but we used both PZTs that are placed at different Gouy phase positions and we didn't see anything at IY.

On behalf of Gerardo and Danny:

Both ears were silicate bonded to the LLO ITM (ITM-08) this week.  The mass has been stowed back in it's cake tin and await shipment out to LLO. 

One of the GS13s of HAM-ISI unit #6 (Pod #94) appeared to be defective this week (see aLog 3183).

Greg and I opened it this morning. Two flexures were broken.

• D0901318-v3, s/n 124 (Pic. 1)
• D0901319-v4, s/n 199 (Pic. 2)

One can see wear on the non-broken side of D0901319-v4, s/n199  (Pic. 3,4). The pattern is very similar to what Jim reported in the SEI Log a few months ago.

We also found a small flexure debris. This debris was identified as being part of D0901318-v3 s/n 124 (see black line on pic. 5).

The pod was tested at reception on a leveled surface. Nothing abnormal could be seen on its response at that time. It was then installed in the ISI. No major event was reported (drop/shock/…). Spectra were taken with the ISI tilted and the pod appeared defective. Any spectra, even with the ISI leveled showed it defective after that.

As it already happened, it is possible that the shocks, endured by the instrument during its shipment, damaged the flexures. In these conditions, tilting the pod back and forth to install it, and/or tilting the ISI for testing purposes, could have lead to the breakage.

We have shockwatch data for this shipment. Greg will post it later on.