[Sudarshan, Gabriele]

Following up on yesterday's activity, today we properly dumped the beams on IOT2R. We tried different configurations: beam dump directly in place of the first mirror of the periscope, razor beam dumps, black glass plate, black galss beam dump. Finally, the best configuration is the one that lets the beams go through the periscope (recentering all three mirrors) and dump the REFL beam far away with a  black glass angled beam dump, and the IMC trans beam with a razor blade dump. See the attached pictures for more details.

With this configuration, we measured the out-of-loop intensity noise with MC2_TRANS, as before with the PRM aligned and the BS misaligned to avoid flashes. After many trials, we could geth the 18 Hz peak down by a factor 10, as shown in the 5th figure. Green is PRM aligned, ISS second loop off, before our modification. Brown is PRM aligned, ISS second loop on, before our modification. Red same as the last one, but aftr the modification.

The IMC transmission beam is not critical, and even leaving it undamped doesn't change much. Instead, the dumping of the REFL beam is critical. By simply tilting the beam dump of a very small angle (order of one degree), we could change significantly the amount of intensity noise. We tried many times to tweak the angle. Once we could make the 18 Hz completely disappear, but then just the action of clamping down the beam dump wornsed the situation. We think it's not really worth to spend more time on this, since a small change of the PRM alignment will in any case move the beam and probably spoil the noise reduction. The last figure shows a comparison of the intensity noise with different beam dump positions. Blue is before the modification, the other traces correspond to sligthly different beam dump positions. We also tried to rotate the beam dump 90 degrees, to have the black glass plates oriented "horizontally', but this didn't help either.

In conclusion, now the situation is much better than before, but the REFL beam transmitted by IM4 and collected on IOT2R is very critical. We should consider a better solution for the long term. For future reference, the last picture shows which beam we are talking about: the purple beam is the REFL beam transmitted through IM4 and sent otto IOT2R where it is reflected/scattered back to IM4, then reflected off the IM4 HR face and finally going to the ISS aray (green beam)

Attached are 30 day trends of the ITM and ETM Vertical, Pitch, Yaw, and VEA temperature drifts.  Yep, they drift. 

These are the results of the ETMX excitations to test for working channels. Again, 4hz/10cts/pitch

re 15205,

Attached are trends from the last 20 hours.  There is the ALS REFL CTRL OUTPUT(um I believe) which Nic's servo is attempting to keep zero, next is the HEPI Longitudinal Location (nm,) the servo is on when this is changing unless HEPI has tripped and is reacquiring (which did not happen.)  Third plot is the Horizontal pringle of HEPI(not sure of units) giving some indication of platform(or maybe just actuator) distortion required to move in one dof while keeping the others where they started.  Last is the OpLev Yaw, the HEPI RZ will not be informative as that loop is closed and will appear to be perfect.  The OpLev Yaws appear to move some but I don't think more than when the servo is not on.  You can certainly see the tidal effect on the REFL CTRL when the servo is not operating.

Scheduled today:

ISS beam work
CDS end Y PEM work
U.S. Linen on site
Warehouse construction work continues

no restarts reported.

conlog reporting of frequently changing channels attached

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.  

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.