gerardo.moreno@LIGO.ORG - posted 18:25, Thursday 07 August 2014 (13277)
X-End Purge Air Off
Turned off purge air at X-End station. Metal vent/purge valve is closed.
Turned off purge air at X-End station. Metal vent/purge valve is closed.
Rai was able to inject ionized gas into the YEND station chambers today. It took about 15 minutes to reach 42 torr where we ended the experiment.
The chamber is roughing down again and will transition to turbo this afternoon.
Pirani gauge plot attached.
Y-End is now on turbo, CC is ON, pressure is at 1.34x10-06 torr.
Cooling lines open for the turbo.
It actually took 29 minutes to get to 42 torr, faster than I had calculated.
The LVEA pumpdown has stalled at 10^-4 torr. There are many possible suspects with vented annuli on 8 chambers, and many new viewports and electrical feedthroughs. We will be busy restoring these systems in the upcoming weeks and probably spraying helium.
Day's Activities
This morning I adjusted the I-Q balancing of all the demodulators at the AS port (i.e. the ones in ISC R3 rack).
I did the same technique as described here. I did not turn on any of the whitening stages. The gain of the whitening filters were set 21 dB (although I am not sure if this is close enough for the future operational condition.) except for ASAIR_B_RF18 which I set the gain to be 45 dB. The beatnote were ajusted such that they are in between 40-50 Hz. Since the amplitude imbalance were typically smaller than 0.5 % or so, I did not try to correct the amplitude imbalance. Therefore only parameters I adjusted were the phase difference btween the I and Q signals. Here are the results:
= = =
At the very bottom of the rack, there is a quad demodulator which takes care of 18, 90 and 45 MHz LSC signals. From channel 1 to 4, the order of the demodulation frequencies should be 18, 90 and 45 MHz in order to satisfy the planned cable layout (see for example D1200666). However, this quad demodulator (S1001003) has these signals in order of 45, NAN, 18 and 90 MHz. The point is that this is a special mod version, where it has a fancy diplexer in it. So you can not easily swap the modulation frequencies between the channels unless one opens up the box and physically allocates the position of the boards. Because of that, the signal at the ADC were screwed up. For example, I obtained a signal from 18 MHz demodulator at a digital channel which was dedicated for 45 MHz (i.e. LSC-AS_A_RF45). In order to quickly fix it, I decided to swap the two ADC cables that were connected to the back side of the whitening filter. This pf course lead to another modification -- I had to swap the BIO cables.
RichardM, PeterK A few pictures were taken of ETMY in order to see if any dust particles could be spotted prior to Rai's vacuum test. The pictures were taken from the viewport under the beam tube as this appeared to offer the best view and allow some manner of support for a camera. A number of shots were taken with a 30 sec exposure. The illuminator was on for these photos. Even when zooming in on the images, it is not clear if there are any dust particles present because of the images becoming pixelated. One of the images shows a black spot near the centre of the optic but I think this is an artifact of using a smaller aperture.
Alexa, Sheila
We went into the PSL to understand the calibration of the power into the chamber. The first step was to remove temporary half wave plate alog 12710.this changed the splitting ratio for the monitor PD, causing our monitor to not be accurate. .We also updated the calibration of the rotation stage, the max power we set to 20.7 Watts based on a measurement with the water cooled power meter head before the rotation stage; we found that the minimum power was 17 mW at an angle of -24 degrees so we also updated those values.
As a check we requested 1 Watt from the rotation stage, we measured 1.12Watts, and our monitor readback report 1.15 Watts. We have left this setting, the light pipe shutter is closed.
model restarts logged for Wed 06/Aug/2014
2014_08_06 02:01 h1fw0
unexpected restart of h1fw0
Minutes from Morning Meeting
Safety valve set points @ 5 x 10-1 torr -> will change to nominal value of 5 x 10-2 torr tomorrow
(Borja)
Several issues has not allowed me to drive the ETMY ESD until late afternoon today. At this point I was able for the first time to test, with real data, the automation code for the ESD charge measurements develped at Livingston. I did have previously adapted it for Hanford's slightly different configuration but this was the first time I was able to test its results. Unfortunately the automation on the injection, data request and analysis is not robust, not allowing for the whole process to finish several times. Also the code does not take into consideration conversion factors on the V BIAS from Voltage to counts and viceversa. I assume this is taken care in Livingston outside of the code but certainly that solution does not make it universal.
Looking at the procedure with Rai I realized that we have to be careful on the level of the driving signal amplitude to be below the minimum V BIAS used in the analysis otherwise linear approximation assumptions in the methodology are no longer valid.
Rai is leaving on Saturday and we need to apply his discharging technique before then (optimally tomorrow). Before this takes place we need to have some ESD charge measurement data so that we can compare with data taken after the discharge and see the effects observed. This time constrains has made me decide to do the measurements manually tonight. I may be able to run the automation code afterwards and compare it tomorrow with the manual measurements but this may not be possible. See manual measurements in the attached document.
We are going to use the manual measurements as a basis for comparison before and after the discharge procedure
which we hope to do today.
I cannot comment on the automation program but urge several things:
1) The absolute value of the bias voltage needs to be greater than the absolute control voltage.
2) The phase and amplitude of the motion needs to be used.
3) The linearization routines should NOT be used.
If these simple considerations are observed the algebra to fit for a charge dependent force
coefficient is straightforward and linear.
Vbias + Vcharge = deflection angle*a where a is an unimportant constant
The feeling of the LLO charging people is "Yes!" to all these points. Regarding the automation scripts, it *should* be a simple matter of setting up the desired biases and measurement parameters and hitting go. The scripts take the measurement in exactly the same way one would if doing the measurement manually, with all the amplitudes and bias offsets user-configurable and the signals are injected directly at the individual ESD quadrants (i.e. not through any linearization).
There is an important point which although I did not mention explicitly in the aLog entry is highlighted in the document attached to it. This is that the excitation driving each of the 4 quadrants provided a good SNR (of between 4 and 15 depending on the BIAS Voltage) of the oplev deflection values at the injection frequency with the exception of the LL quadrant which only showed noise (evidenced by the random values of the measurement points in magnitude and phase and by the low coherence of the between the excitation and the oplev deflection at the injection frequency). This issue, I have found, has a long and complex history which I will deal with in another aLog entry on the 9th August. I have also added to this comment the plots of the measurement results, an updated version of the measurements pdf and a table with final values of slope and Veff for each measured quadrant.
| UL | UR | LR | |
| Veff PITCH [urad] | 122 | 52 | 123 |
| PITCH slope [V] | 2.6e-7 | 1.9e-7 | -2.65e-7 |
| Veff YAW [urad] | 125 | 103 | 144 |
| YAW slope [V] | -2.2e-7 | 2.34e-7 | 2.3e-7 |
As suspected and reported earlier while doing coil balancing (cf logs 1 and 2), SR2 M2 UL actuation appears to be non functioning. An in-chamber cable would be disconnected.
First, in order to confirm the problem, an old range-of-motion matlab script was resurected and used : it ramps positive then negative offsets (+/- 132000 cts) to each coils of M2 stage, and looks at the motion response. The plots of the results are attached and are clearly showing a difference with the UL response, moving less than 0.1um whereas the other osems show more than 1um range of motion.
Then, to see if the problem was in-chamber/in-air, the resistance of the four coils of middle mass was measured at the satellite box and the in-air side of the feedthru - in both cases a breakout board was used, plugging it to the sat-box side of cable H1:SUS_HAM4-31 in the first case, and the HAM4-D6-3 feedthru connector in the second case (wiring ref : D1000599). Measurements with the multimeter at the two ends roughly gave the same results described below :
LR (pins 1-14)~= 17 Ω
UR (pins 4-17) ~= 17 Ω
LL (pins 7-20) ~= 17 Ω
UL (pins 10-23) = ∞ Ω
The resistance of UL shows the circuit is open between the flange connector and the coil, somewhere in the chamber.
SR2 was tested by Stuart after HAM4 doors closeout and wasn't showing any actuation issues.
Since Borja balanced the coils with a non functional actuator yesterday, I will run undamped M2-M2 TFs overnight using the gain values he found, and see how the dynamic response is affected.
Correction to Arnaud's statement: in the closeout measurements that Stuart made (see LHO aLOG 12950), there are signs of badness: you can see in the transfer function data for the individual suspension (2014-07-23_1500_H1SUSSR2_M2_ALL_TFs.pdf), in the last few pages which show the individual OSEM basis response to each Euler basis drive, UL shows a particularly odd-ball response at high-frequency. Its response does *not* fall as 1/f^2, and the magnitude is much larger that other sensors. Other measurements of similar stages show no such features.
Stefan, Sheila, Alexa, Kiwamu
We locked the IMC on a 00-mode this evening. The next step is to wait for the pump-down to finish and perform a ring-down measurement to check if the absorption is not too high.
Preparation:
After talking to Mike and John, we agreed that we can do an IMC-related interferometry with a low power laser even though we are not yet on the turbo pump.The pressure at that time was below 10 torr according to John. The PSL power was decreased to 56 mW by using the rotational stage because we needed to be lower than 100 mW which is the limit for the in-air IMC locking. We then locked the rotational stage such that we won't accidentally exceed the limit. Also I had a chance to talk to Dennis about this laser power issue and he agreed that we can do some interferometry with a low power laser. Thank you for the discussion, Mike, John and Dennis !
Initial Alignment:
To recover a good alignment, we started from the PZT input pointing. We checked the spot position of the scattered beam from the HAM1 viewport, projected on the wall of the PSL enclosure. The beam was lower than the previous marking, by 5 mm or so. We then touched up the input PZT to bring the beam back to the previous making position. The PZT count in PIT had been 679.6 and after this alignment it became 683.6 counts. The we checked the alignment on the table, but surprisingly, we did not have to touch any optics at this point. This means that Bubba and company placed the IOT2L table very precisely, maybe with a precision of a few mm. Thank you, Bubba !
We then placed an analog camera in the transmission path because the GigE was not functioning for some reason. At the beginning the alignment seemed off largely in pitch. So we started tweaking the things. Starting with the PZT again, we could not get a decent 00-mode. We decided to touch the MC mirrors. We touched MC2 in pitch and was able to see a decent 00-mode flash. Good.
Locking and further tweak:
As soon as we turned on the IMC board with a high gain, it grabed a 00-mode. We then did a futher alignment on MC2 to coarsely maximize the power-buildup. The visibility was 75 %. In lock, the reflection was about 40 and unlocking We then re-centered the WFSs beam by hand on the table and tried the ASC servo. But, after an hour of struggling, we realized that the MC2 TRANS QPD did not have a good enough signal-to-noise ratio. So we need to crank up the laser power once the pumping is over. This is now preventing us from engaging the ASC loops.
An enigma:
Signals from the IMC_REFL_DC signal occasionally behaved quite funny -- the REFL_DC signals went up by a facto of 5 or so, while the WFS DC signals remained the same. At this point, we have no idea what was going on. We will investigate a bit more tomorrow.
Great to see the IMC being locked again. For reference I've just attached some plots taken from the IMC summary pages (https://ldas-jobs.ligo-wa.caltech.edu/~detchar/summary/day/20140807/imc/#all) showing the locking activities. First is a normalised spectrogram of IMC-F. It seems the majority of the noise features correspond to changes in the WFS alignment (2nd plot).
Similar to HAM2 & HAM3 but the shift in position wasn't enough to trip the ISI but the outputs were decidedly large. So, I reset the target position to the free hang position. Unable to safe.snap as SUS folk are using platform.
Safe.snap done for HAM4 HPI & ISI. Committed the snaps for HAM2 3 & 4 for ISI & HEPI to the SVN.
model restarts logged for Tue 05/Aug/2014
2014_08_05 10:16 h1hpietmy
2014_08_05 10:16 h1iopseiey
2014_08_05 10:16 h1isietmy
2014_08_05 10:20 h1iopsusey
2014_08_05 10:20 h1susetmy
2014_08_05 10:20 h1sustmsy
2014_08_05 13:02 h1fw1
Unexpected freeze of h1seiey, unexpected dolphin glitch of h1susey during recovery, unexpected h1fw1 restart.
sorry, wrong date. Should be Tuesday 5th August.
model restarts logged for Mon 04/Aug/2014
2014_08_04 12:39 h1lsc
2014_08_04 12:42 h1lsc
2014_08_04 12:45 h1broadcast0
2014_08_04 12:45 h1dc0
2014_08_04 12:45 h1fw0
2014_08_04 12:45 h1fw1
2014_08_04 12:45 h1nds0
2014_08_04 12:45 h1nds1
no unexpected restarts. LSC ipc work plus related DAQ restart.
Sorry, got the dates wrong and skipped Sunday:
Sunday 3rd August: no restarts reported
Monday is actually the 4th of August.