Bubba and I have stabilized the LVEA and VEA temperatures.

We still have known mechanical issues which are probably impacting the control loops so we should be able to improve things - especially XEND.

The one degree spike at XEND on the 19th was due to my attempt to outsmart the system.

Motorized variac heater controls are being ordered for the two end stations which should allow for better control and transient behavior.

We may be asking to raise the set point at XEND - so if anyone has thoughts on this please let us know.

Kiwamu, Stefan, Nic, Evan

First, some troubleshooting:

• The ALS DIFF guardian kept blowing the arms out of lock while trying to engage. We changed the ETMX feedback from distributed to offloaded (see LHO#15208), which fixed the problem.
• I think we can get DRMI to acquire lock more frequently by turning the POP18 trigger thresholds up for MICH; right now the guardian values are 1.7 and 0.8 for upper and lower, but I've found that 20.0 and 3.0 seem to give slightly better results. Maybe it's just statistical fluctuation.
• An open question is whether we can soften the ALS lock losses so that the mode cleaner is not kicked out of lock.

After troubleshooting, we were able to get to DRMI3f+arms with a reasonable duty cycle, so we moved on to the problem of the CARM handoff.

Instead of pursuing sqrt(TRX+TRY), we looked at REFL9I. Surprisingly, we found no response in this signal in response to different CARM offsets. We thought this might be due to bad IR alignment into the arms, so we unlocked everything, then locked the Y arm in IR, and adjusted ETMY to maximize the transmitted IR power. This improved the buildup in Y by a factor of 3, but REFL9I continued to be nonresponsive. While locked, we tried some further tweaking of the ETM alignments, with no success. Relevant UTC times: 2014-11-21, from 09:00:00 to 09:30:00.

(Stefan Evan Kiwamu Nic)

We found the ETMX suspension was changed back to distributed control on Tuesday Nov 18, 2014 at 19:14. There was no elog documenting this. We expect this was an error (or maybe a BURT restore?). It's very surprising that we were still able to do ALS control at all in the interim.

The ETMs had been distributed for a long while, but were changed to offloaded while diagnosing ALS DIFF issues.

We've now changed it back to offloaded.

I just tripped ETMX ISI (and suspension watchdogs) by sending a too large signal to M0.  

[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.

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.

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, 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.