[Sudarshan, Gabriele]

We tried to better dump the beams on IOT2R with a piece of black glass (and dumping the glass reflections with the razor blades).

The PRM was aligned, but to avoid disturbing too much the locking activities, we left the two arms and the BS aligned as well. The PRC flashes made very difficult to get any conclusive result. We think that the 18 Hz bump was not there anymore, but at the end we were not completely sure, since there was too much more noise due to the flashes. We'll try again tomorrow morning, with only PRM aligned.

For the moment we put back the upper mirror and dumped the beams with two razor blade dumps just before the two bottom mirrors. The situation is back as before. 

In the meanwhile, we noticed that the periscope was not propely clamped to the table, and we accidentaly moved it. This shouldn't be important. Now we clamped it securely.

Intensity noise vs PRM position

The first plot compares intensity noise as measured on the ISS (in and out of loop) signals, on IM4_TRANS and on MC2_TRANS:

• BLUE = second loop off, PRM misaligned
• GREEN= second loop off, PRM aligned
• BROWN = second loop on, PRM aligned
• RED = second loop on, PRM misaligned

The conclusion is that the noise added by the PRM reflection is still there, even though it's not as bad as before. However, in the present configuration, closing the second loop does not give us good performance, since for example on MC2_TRANS we can measure intensity noise as large as 8e-6, worse than when the second loop is open at some frequencies (18 Hz).

Tapping on IOT2R

To better understand the origin of this noise, I aligned the PRM, misaligned the BS to avoid any IFO fringes, and closed the second loop. The attached figures 2 to 4 shows the out-of-loop ISS signal (SUM58) and another measurement of intensity noise using MC2_TRANS (both calibrated in units of RIN, but MC2 is sensor noise limited at 1e-7 /rHz level).

• In figure 2, I'm tapping with one finger on IOT2R enclosure, without opening it. The effect is very large, and in particular the 18 Jz bump and harmonics are rang up
• In figure 3, I openend the enclosure and I'm tapping gently with one finger on the bench, far from the beam dumps that are on the path. Still, there is quite an increase of noise
• In figure 4, I'm gently patting the top mirror of the periscope, without touching anything else. The noise is cleary increased, especially the 18 Hz peak and harmonics

In conclusion, there is still a lot of scattered / backreflected light coming from this bench, likely already at the level op the upper periscope mirror. We must dump these beam properly.

In the last figure, I misaligned the PRM mirror and I stroke the bench much strongly than before. There is no visible effect. So it's the REFL beam that causes the problem. In addition, we can conclude that the noise that we normally see in the out-of-loop signal is not coming from this bench, but it's something else, still unidentified. One interesting observation from the first plot, is that hen the PRM is aligned, some of the structures visible in the out-of-loop ISS signal are not there. So maybe they are again light from the REFL beam, which is scattered in-vacuum.

Hanford hauling through the Wye barricade will occur on swing shift on Friday 11/21 starting near 2:00 PM but not on day shift, meaning that LHO 1-10Hz seismic should be quieter than usual on Friday until mid-afternoon.  ERDF will operate a day shift on Friday.

no restarts reported.

conlog frequently changing channel report attached.

Nic ran Jim's script. 

Earlier tonight, we had a large drift in ETMX pitch (1 urad over about 7 minutes).  I turned off the sensor correction (ETMX ISI X only) for the last several hours, this seemed to help.  Now I've turned it back on so we can see if this continues to happen overnight.  

We are leaving the arms locked in green, and the mode cleaner locked.  This should give a chance to see if the mode cleaner is really stable when there is no actuation on it.  

Sheila, Alexa, Dan, Nic, Evan

EX/EY:

• Sheila and I went to EX and EY to assess the state of the LSC-X/Y_TR photodiodes. At EX we didn't do anything. At EY, we turned down the preamp gain on the ThorLabs PD from 20 dB to 0 dB. We hope this will prevent saturating the ADC when there is significant IR light in the arm.
• Over a period of 10 minutes, we can see the ETMX oplev drifting significantly; this degrades the built-up light in the arm when locked.

Setting up sqrt(TRX+TRY):

• Our goal was to send the sqrt(TRX+TRY) signal to REFLBIAS which is connected to the second input of the CM board, and replace the COMM PLL CTRL signal which is used for ALS COMM. The COMM PLL CTRL signal passes through a low pass (40 Hz) and boost (1.6/40 Hz p/z). So we copied these filters into the digital filter of REFLBIAS (FM3). We also installed an integrator with a zero at 50 Hz (FM5), so that the sqrt(TRX+TRY) signal crosses over the ALS COMM OLG at low frequencies as we increase it's offset. We also have some calibration filters (FM4) installed. Meanwhile, the normalized sqrt(TRX+TRY) filter, LSC-TR_CARM had an offset of -1.4 and a calibration filter to pm. We had set up a trigger on REFLBIAS and the integrator, so that REFLBIAS only engages when TRX is above a threshold of 1.0.

Attempt at sqrt(TRX+TRY):

• Several times tonight we were able to lock DRMI on 3f with the arms held off resonance by ALS. We were able to bring in the CARM resonance to about 800 Hz_green, at which point REFLBIAS engaged and blew the lock. So we will have to try a different stragety for the handoff of ALS to sqrt(TRX+TRY).
• In order to get DRMI to lock with arms, we needed to increase the MICH gain to 6 (up from 4 yesterday).
• This afternoon, Nic and I realigned the ASAIR A and B diodes, and the ASAIR camera.
• Sometimes, we lose lock because the endstation VCOs are running out of range. Some kind of offloaded slow feedback would be helpful here.

Guardian improvements:

• There have been miscellaneous improvements to the ALS and DRMI guardians to improve the lock acquisition time. We were able to get DRMI+arms to lock more frequently tonight than in previous nights.
• Alexa and Nic implemented a state in the ISC_DRMI guardian that offloads the ASC WFS to the M2 lock offsets in PRM, SRM, and BS.

Using the L1 screen as a template, I increased the number of matrix elements in the input matrix screen. I couldn't just copy the L1 screen for 2 reasons. First they don't use a ramping matrix but H1 does. Second, they have an additional signal coming into their input matrix. 

Their extra signal is the so-called "TR_DARM" signal. One nasty time bomb is that their signal would need to be inserted in the matrix at position 36, in between the TR_CARM and TR_REFL9 signals, shifting those down. So this screen will change all around if that difference is incorporated from L1.

screenshot attached

Sheila, Nic, Evan

The refcav power has steadily declined over the last 10 days. Tonight it got so low that the modecleaner could not maintain lock for longer than a few minutes.

Sheila and Nic have realigned the pointing to the refcav in order to recover the power.

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