SR3 oplev was realigned to the new SR3 angle.

We've found that this oplev had a clipping problem even before SR3 angle was changed. OPLEV SUM used to be about 30000 counts, and after we were done the SUM jumped up to about 66000 counts without changing the whitening setting. Doug thinks that this might be a bit too high a count, but ADC is not railing so we'll leave it as is.

Details:

SR3 oplev had two serious problems that are not related to SR3 angle.

• There was a large clipping inside the beam launcher enclosure (first picture). This was fixed by moving the launcher inside the enclosure.
• The receiver enclosure and the viewport are connected by a metal pipe, but the bellows at the end of the pipe was not strong enough and the thing was sagging badly, making the aperture much smaller than it should be (second picture). This was temporarily fixed by putting some material under the pipe (third picture). This is not a real fix, I think.

After these were fixed, Doug aligned the launcher such that the return beam comes through the receiver viewport/pipe cleanly. Due to the beam angle shooting up from HAM5, in order to avoid clipping by the receiver viewport, bellows and the pipe, the beam was positioned much higher than the center of the pipe opening at the receiver box.

At this point, we recognized that the oplev sensor couldn't be moved high enough to receive the beam as the vertical stage doesn't have enough range. Actually the vertical stage has a huge range, but at least 3/4 of that range is wasted to be able to lower the sensor to the position where there is no possibility of receiving any beam with any SR3 alignment.

We removed the aluminum part on which the sensor is mounted, Doug made new holes, we remounted the sensor at a higher position (4th picture) and the translation stages were moved until the beam was roughly centered (5th picture), and we used the MEDM screen to fine tune. 

A cell phone camera with selfie mode turned out to be quite useful to monitor the beam position when there's no light on the sensor, and that's what was used to take the 5th picture.

(Alexa, Nic, Sheila)

We measured the ALS COMM OLTF and found the UGF to be ~400 Hz, with a crossover at ~70 Hz. In September we had changed filters in MC2, and CARM as reported in alog 14214  to increase the crossover frequency. I also noticed we had changed our configuration in the LSC_REFL_SERVO CM board relative to what was in model (alog 11109). Now we have:

• In1 gain: 6dB, POS, DISABLE
• In2 gain: -4 dB, POS, ENABLED
• NO common compenstations or boosts turned on
• Additionally, we have COMM PLL Boost on in the path to CM.

9:17 Fil to pick stuff up at EX, then to EY PEM cabling

9:56 Doug to LVEA for SR3 OpLev work

9:58 Jeff and Andres to LVEA staging for SUS storage

10:22 Jeff and Andres exit LVEA

10:28 Krishna and Jim to EX for BRS checkup

11:03 Mitch and Jeremy out of LVEA

11:11 Cris to EX

12:02 Sheila and Nic to ISC electronics racks in LVEA

12:04 Fil back from EY

12:32 Doug out of LVEA

15:45 Doug to SR3 for more OpLev work

There has been some concern that there might be excess cps noise in some of the channels. So i looked at 20 minutes of data at 1am sunday night/monday morning.

Looking only above 30Hz where the sensors have hit the noise floor, all of the coarse channels are similar and between 3.5-4.5E-10m/rrtHz about what we expect.

The stage 2 channels show two outliers, ITMX H2 and ITMX V1, maybe BS H2 also but that is close enough so that it could just be at a large offset (we expect the noise floor to go as the gap squared) I'll check that.

  The first thing to do is for me to look at another time, and to check the cables and connections for those sensors

I looked at a second data set calling it "B" (24 hours later)  ST2 ITMX H2 and ST2 ITMX V1 still show excess noise BS H2 is down to 4.5-5E-10m/rtHz which is a little bit noisy, but probably within what we are calling acceptable. I attached the data because Jeff asked to see the ADC noise on the plot

When I say large offset I mean > 10000 counts, so 1200 counts is centered for this discussion 

(Alexa, Evan, Sheila)

We roughly centered the EX IR QPDs; the beam is now on all four quadrants, however, more fine tuning could be done. The beam was slightly off in yaw common to both QPDs, and already fairly well aligned in pitch.  I adjusted picomotor M14 by ~200 steps in yaw to bring the beam center on the QPDs. I did not have to adjust M4, which would affect the IR transmitted beam onto  ISCTEX, and potentially clip the green beam. The current picomotor positions are:

M14: X = 53045, Y = -38603, M4: X = 9267, Y = 1665

The sum show about 1000 cnts on QPDA, and 700 cnts on QPDB. This is consistent with the power budget (alog 10006), so I believe this is the real beam and it is now centered enough.

I did something similar for EY.  QPDA was farily well centered, with the beam on all four quadrants. QPDB was off a bit; so I adjusted M14 in both pitch and yaw, to get this beam better centered and on all four quadrants. This adjustment did not move QPDA all that much. There does not seem to be a picomotor position readback for EY ???? They are all zero. The sum show about 840 cnts on QPDA, and 760 cnts on QPDB.

J. Warner, K. Venkateswara

Jim installed Rich's SC filters to all sensor correction filter banks. This afternoon, I turned on ETMX SC to Stage 1 using the tilt-subtracted ground sensor and then for ITMX using the normal ground sensor (STS) along X. For Z, SC to HEPI was enabled for both chambers. Sheila then aligned the arms and locked them using ALS.

The aim was to observe if SC reduced arm motion between~ 50 to 500 mHz as indicated by the local sensors while keeping the low frequency motion small. The noise in this band seemed lower, but unfortunately activity at ITMX increased ground motion as measured by the seismometers which ended up re-injecting excessive noise at low frequencies. This test should be repeated later in the evening or night when activity at the corner is reduced.

For the moment, I have left tilt-subtracted SC on at ETMX and SC off at ITMX.

As per Aidan, I set all 4 of the LOWER RH RTD channel calibration gains and offste to their nominal setting.  Likely these were not input after the summer vent or they were over written sometime since.  Settings for all 4 should be:

LOWERRTD_GAIN = 50 (K/V)

LOWERRTD_OFFSET = -257 (C)

One arm RH calibration medm screen shot is attached.

Gabriele, Sudarshan

We were able to close and open the ISS Second Loop with attached python script.

Some details about the script:

• Initially, it makes sure the loop is open, integrator and boost are off, gain is at 0dB and second loop servo is on.
• It sets the ref signal value so that it is not too far away from the nominal value; this value is determined by looking at the average in loop PD value. 
• It then calculates the average of second loop output and compares it to the user defined  threshold to move the ref level signal such that the second loop output is less than the threshold.
• After that, it waits for second loop signal to be around zero crossing to switch on the second loop. This was done because the timing of switching-on the second loop mattered. If the second loop output value was far off from zero, it threw the mode cleaner out of lock.
• At the end it checks if the ref signal is within the threshold. If it is, the boost and integrator are turned on and the loop remains closed, if not, the loop opens.

These python script will be eventually implemented on the IMC Guardian.

Note: We tested it 10 times in a row  and it never failed.

I've been asked to investigate the proper (or not so proper) operation of the SUS AUX /  monitor channels. It appears that, in particular, the L1 stage of ETMY has some questionable counts in the NOISEMON (all 4), the FASTIMON (LR) and the VOLTMON (UL).  I've done an excitation of 4Hz with an amplitude of 10 cts on all stages (Pitch) of ETMY and taken measurements. Below are the results. 

K. Venkateswara

Attached plot shows the various temperature sensors at EX. The thermistor temperature sensors temporari;y use the PEM tiltmeter channels as described in 14825. The two left plots show the thermistors and the top right plot shows the PEM temperature sensors. The very low frequency position of the beam-balance is also a sensitive thermometer as seen in the lower right plot.

There seems to be some oscillation in the temperature control loop for the VEA seen in the last 1-2 days. May need some tuning.

Nic, Sheila, Alexa

We pulled the CM summing junction from R4 (in the ISC racks by the PSL, the one closest to HAM1).  The OK light was not on and the measured transfer function was -80 when it should have been 0dB.  The TF from the excitation to the output was also garbage.

To have maximum power transmitted by the IMC, I had to move the beam on WFS_A a bit out fo the center (WFS_A_DC_PIT = 0.1, WFS_A_DC_YAW = 0.23).  I was not able to recover the same power with centered WFS and an offset on DOF1/2. But maybe just because I didn't have much time to try. Right now, I'm leaving the IMC angular control runnng without any offset. Intensity noise should be good enough.

In a previous report I showed that the beam can wander on the IMC WFS by something like 0.1 in QPD normalized units. To understand how much this can affect the optimality of the IMC alignment, I moved the beam on WFS using the picomotors, and tracked the change of jitter to RIN coupling.

I injected a 11 Hz pitch line on the PZT (amplitude 0.5) and a 17 Hz yaw line on the PZT (amplitude 2) and looked at the amplitude of induced RIN, both in the second loop signals and in IM4_TRANS. All signals gave consistent result, so here I'm quoting only one value.

Here are the raw results. The first four columns give the deviation of the beam position with respect to the initial one (which was not centered)

The effect is not so small, in particular a pitch miscentering of the beam can increase by as much as a factor 3 the coupling of jitter to RIN.

So it seems that the normal wandering of the beam on the long period can give some IMC misalignment that will cause a significant worsening of intensity noise. One solution would be to implement the beam size modification already done at Livingston.

re 15131, attached are pdfs of spectra for the ITMY HEPI L4Cs around 1am Tuesday and Wednesday before and after I made these changes Tuesday morning.  The first two pages are the individual runs and the third crowds things up and puts them on the same plot to maybe improve the comparison.

Bottom line--some places better some not as good even considering the differing ground motion.  I think these controller could be more aggressive if we want.

Alexa, Dan, Nic, Sheila, Evan

Tonight we made some improvements to our automation, and we reduced the CARM offset with DRMI locked on 3F.

• We measured some open loop gains with DRMI 1F + arms off resonance (by 1000 Hz at 532).  They seem to have about the same UGF as wihout the arms, for PRCL we change the gain from 22 to 11 when adding arms, and for MICH we changed it from 5 to 4, SRCL we did not change.
• We turn on the DRMI ASC, it brings AS 90 positive, then if we leave it on we start mode hopping.  For now we are just turning the ASC off once we get a decent build up in AS 90.
• We have not changed the ratio between the 3F and 1F signals in the input matrix.  Evan got a measurement of the sensing matrix.
• Then we decreased the CARM offset without any problems. 

A second round of testing on the all-metal 3IFO QUAD unit Q7 is attached.  After we saw a few cross coupling terms and struggled with coherence in the prior measurement set, we made a few adjustments to the QUAD mechanics.  However, readjusting the lacing cabling and retuning the sensor mounting tablecloth seemed to not help much.  There is still L and R bleeding into P on the reaction chain.  We were able to improve the coherence by building a fort around the test stand however.  The main chain looks to be in pretty good shape though.

The first attachement below is of Q7 with damping on and off.