[Sheila, Gabriele]

As suggested by Keita during the morning meeting, we checked the IM4 transmitted beam coming from the PRM reflection, on the in-air table. We dumped both beams on the table, and this improved a lot the situation. When the PRM is aligned, the noise on the ISS diodes doesn't increase much anymore. However, there is still a small worsening at 18 Hz, so maybe in the future we might want to better dump the beam at the level of the upper mirror into the enclosure.

SEI - plans to do some upgrading/standardiing on Tuesday (maintenence day). Otherwise, standing by to assist with commsissioners.

SUS - plans to work in W bay in the mornings for the entire week

PSL - working on issues with ISS second loop. Also, issues with an apparent 30% power fluctuation that may have something to do with an errant reflection??

3IFO - gearing up for SUS baffle build. Working in VPW to clean up for Contractors

CDS - X-end work - power up and checks

           Y-end work - cabling

Facilities - bring palette jack from MX to staging building. Working to maintain temperatures everywhere. Apolllo may be here this week. Their work will include sawing asphalt which will be conidered invasive.                        operators should be kept informed as to all activities of this nature.

Op Lev - re-alignment work of SR3 (work permit #4946). This will neccessitate transitioning to full LASER SAFE at some point.

Commissioning schedule to remain the same; 12:00 cutoff for noisy work in VEAs unless otherwise granted

grouting in the LVEA discussed as imminent in the not-so-distant future.

Laser Status: 
SysStat is good
Output power is 33.3 W (should be around 30 W)
FRONTEND WATCH is RED
HPO WATCH is RED

PMC:
It has been locked 3 day, 23hr 40minutes (should be days/weeks)
Reflected power= 2.5W and PowerSum =25.7W
(Reflected Power should be <= 10% of PowerSum)

FSS:
It has been locked for 0h and 4 min (should be days/weeks)
Threshold on transmitted photo-detector PD = 0.74V (should be 0.9V)

ISS:
The diffracted power is around 8% (should be 5-15%)
Last saturation event was 1d 16h and 38 minutes ago (should be days/weeks)

model restarts logged for Sun 16/Nov/2014
2014_11_16 08:27 h1fw1

unexpected restart

Sheila, Dan, Evan

Yesterday and today we have tried to get the interferometer into a state where we can lock ALS with a CARM offset, lock DRMI on 3f, and then reduce the offset while staying locked. The lesson learned this weekend is that it is taking too long to get DRMI and ALS locked so that offset reduction can begin.

On the ALS side:

1. Yesterday the ALS DIFF guardian was a little too agressive in turning on the DARM loop, so Sheila and I have added some timers so that the full gain and the boots are engaged more softly.
2. We quickly remeasured the OLTF of ALS DIFF yesterday, and it looks almost identical to what was measured in LHO#15025 (i.e., a UGF of 8 Hz with 60° of phase).
3. Locking ALS seems to be straightforward, but a bit slow. The biggest time sinks here seem to be (1) initial alignment of the arms, and (2) finding the IR resonances. For (1), Alexa, Kiwamu, and I have been working on some modified LLO scripts that use baffle PDs to align the TMSs. We want to expand these so that the ITMs are also aligned using baffle PDs. For (2), we need a better strategy for finding the resonances. Although the ALS DIFF and ALS COMM guardians have "find IR" states, they weren't successful this weekend.

On the DRMI side:

1. Although DRMI was well-behaved yesterday, today we saw a reappearance of modehopping in the SRC. We tried realigning the corner optics several times (and the Y arm once), but this issue kept appearing and throwing DRMI out of lock. After unlocking and then relocking DRMI, it went away, for no reason apparent to us.
2. When DRMI was stable on 1f, we were able to transition to 3f with no issue. However, the mode-hopping issue continued to reappear intermittently.
3. We tried turning on the ASC with DRMI on 1f. It initially improved the POP18 buildup, but then overshot, so we had to turn it off.
4. The POP18 buildup in both PRMI and DRMI varies between 190 and 270 cts. This has been true for at least a week, despite multiple realignments. Previously, we've been getting buildups in excess of 300 cts.

ALS+DRMI, other:

1. Yesterday we were able to get ALS locked with a CARM offset. We tried getting DRMI to lock, but it refused. According to Sheila, this may mean we need to turn down the DRMI loop gains during locking to compensate for the increased optical gain from the arms.
2. Today (like Friday), work was completely stopped by a long earthquake. It started nearly 3 hours ago (ca. 2014-11-16 22:30:00) and continues to prevent us from locking.

Patrick, Dave

We have been scouring the houly conlog reports of EPICS PVs which change more than 500 times an hour for a reoccurrence of the rapid (many times a second) setting of the LSC ramped mux matrix which was observed last weekend. Unfortunately we have not seen anything yet, we will continue our vigilance.

FYI: here is the report from the last hour. (Remember that a 16Hz front end slow channel, if constanly changing, will give 16*3600 = 57,600 changes per hour.)

Process variables in conlog that have changed more than 500 time(s) in the last 3600 second(s):

H1:SUS-ETMY_L1_LOCK_L_RSET        57541        
H1:SUS-ETMX_L1_LOCK_L_RSET        57541        
H1:ALS-Y_CAM_ITM_SUM               2361        
H1:ALS-Y_CAM_ITM_YAW_POS           2361        
H1:ALS-Y_CAM_ITM_PIT_POS           2361        

model restarts logged for Sat 15/Nov/2014
2014_11_15 21:27 h1fw1

unexpected restart.

The IMC perturbation created by the PRM reflection reported before was bad enough, but the worst news had still to come.

The first attached plot shows a comparison of  the intensity noise as measured by the ISS diodes in three different configurations, in particular with the PRM mirror aligned or misaligned. Sadly, the intensity noise gets as much as 50 times larger when the PRM is aligned. The most prominent features are the 15 and 17 Hz peaks with harmonics.

To add more bad news, look at the second plot. The increase of intensity noise is visible in IM4_TRANS and all ISS photodiodes (showing here SUM14 and SUM58 for simplicity). But it is not visible in MC2_TRANS, so it's not real laser intensity noise into the IMC. All the signals in the plot are calibrated in the same units of RIN.

This means that the PRM alignment does not introduce additional real intensity noise, but just sensing noise on IM4 and ISS diodes. The bottom right panel shows the coherence between different pairs of signals, when the PRM is aligned. SUM14 and SUM58 has very high coherence, so they see the same noise. Coherence with IM4 is algo good, while there is almost not coherence with the MC2 TRANS diode, as expected since it's not real intensity noise.

In summary, so far we know that:

• When the PRM is aligned, some stray / scattered light goes into the IM4 TRANS path and pollutes the ISS signals.
• When we close the ISS loop, we can get a good out-of-loop supression, since SUM14 and SUM58 are very coherent
• But this suppression will not be real, since it's coming from "sensor noise"

To test the latter conclusion, I compared the intensity noise as measured by MC2_TRANS, when the ISS second loop is closed and the PRM aligned. 

In the third plot, the blue traces show the situation when the PRM is misaligned and the ISS second loop is open: all sensors agree on the level of intensity noise. The green traces then show what happens when the PRM is still misaligned, but the ISS second loop is closed: again the level of intensity noise is comparable in the four sensors. However, when the ISS second loop is closed, things get different: the ISS out-of-loop sensor shows some good suppression, but MC2_TRANS shows a large increase of intensity noise (up to 1e-4 /rHz).

So, we are re-injecting the ISS second loop noise (due to PRM reflection) into laser intensity. The ISS is not actually stabilizing the intensity noise, but making it worse, at least inside the IMC. We still can't exclude that the spurious beam is creating real intensity noise in the main beam out of the IMC, and therefore the stabilization is doing a good job to proide us a less noise beam into the IFO. We'll have to check using some other out of loop monitors from the IFO.

Some side comments. Both IM4 and the ISS diodes see a very similar excess of noise. Since they are quite far apart in the table, it seems that the spurious beam must be pretty well aligned with the main beam (can it be the reflection from the last Faraday waveplate, which is not well separated from the main beam?). Moreover, when the PRM is aligned, fluctuations of the power measured by IM4_TRANS can be as large as 20-30%, meaning that the spurious beam must have quite a lot of power.

[Sheila, Evan, Gabriele]

Since yesterday night the IMC has behaved in a strange way. It transitioned from a good state with high and stable IM4_TRANS power, to a bad state with lower and fluctuating power. The IMC remained for all the night in the bad state, and this morning it jumped back to the good one a couple of times. One interesting observation was that IM4_TRANS gets very unstable (30% fluctuations) but the power seen by the ISS second loop PDs is almost unchanged: same mean values and only slightly larger RMS. When transitioning from one state to the other, the MC mirrors are also slightly tilted, but is is cleraly an effect and not the cause of the transition.

We finally discovered that the bad state is triggered when the PRM mirror is aligned (see the plot). Apparently, there is some ghost / stray / scattered beam that reaches IM4 QPD when the PRM is aligned. In addition, this light also affects to some extent the IMC alignment signals, since the MC1, MC2 and MC3 mirrors are clearly moving after the PRM is re-aligned.

model restarts logged for Fri 14/Nov/2014
2014_11_14 20:41 h1fw0

one unexpected restart

Keita, Kiwamu,

This is a follow up of the previous investigation for the input pointing issue (alog 15028). We are concluding that the IM2 is the one which messed up the input pointing the other day before the temperate issue hit us.

According to a back-of-envelop calculation, this well explains why we had to move IM4 by 88 urad in pitch to get back to good alignment (alog 15063). Also, from the OSEM spectra, there is no obvious indication of the mirror sticking to the cage or something. Therefore we don't think this is an issue.

Here are summary:

• IM2 suddenly moved when HAM2 ISI was restored at around 22:00:00 on Nov 11 (alog 15032)
• The move was mainly in pitch by 60 urad. Yaw moved by only 5 urad and longitudinal was almost nothing.
• After the move, it stayed at the new angle and never came back to where it was.
• So it looks as if the IM2 mirror slipped in pitch.
• The other IMs showed a similar behavior at the same time, but they are smaller than IM2 did.
• We checked the ASC and some other dignal paths, but there had been no signals other than the alignment biases. So we think it happened mechanically.

The attached is trend of various relevant signals:

Here is the spectra of the OSEMS before and after the slip. The bold curves are the ones taken on Nov 10 and the thin curves are the ones from today. All the spectra from today are consistenly lower at low frequencies supposedly due to different seismic level. Also we are having a small bump at around 2 Hz today for some unknown reason. In any case, we don't see an obivous indication of the mirror touching the cage or OSEMs. Therefore we are concluding that IM2 is still healthy. 

Potentially related to the M7.1 earthquake in Indonesia.

Even a simple MICH is continually thrown out of lock.

Evan, Keita, Kiwamu, Alexa

It had appeared that the temperature in the LVEA had stablized (alog 15054) so we went about realigning in the IFO. Here is the original alignement we started with:

Here are the initial steps we took:

1. Align/lock X and Y arm on green. Note: this required a big adjustment since the temperature had also drifted in the end station.
2. Adjust PR3 to get COMM beatnote back to nominal of about 0dBm; I adjusted PR3 by +2.5urad in pitch, and +0.3urad in yaw
3. Lock the IR to the X arm; this required an adjustment of PR2 in pitch by -34urad.
4. Run the wfs feedback to IM4, PR2 to get full build of IR in the x-arm

At this point, we noticed that the WFS had brought IM4 to a bad alignment. Keita has measured the PR2 baffle clearance (alog 15063); and IM4 was not within range in YAW. So we basically started from scratch, and did the following:

1. X,Y arm locked on green
2.  X arm locked on IR
3. Run wfs to keep IR build up at a maximum and adjust PR3 until IM4 was at a good position. I had to adjust PR3 by +2.5 urad in pitch, and -76.1 urad in yaw.
4. Adjust HAM 3 pico's to get the green beams on ISCT1; i.e. to restore our usual values for ALS-Y, ALS-X_TR_A_LF_OUT  ~ 1 cnt each
5. Adjust the DIFF and COMM beatnote on ISCT1. Evan had to move the BS in the DIFF path because the X-arm was almost completely off the BS (he will post more about this).

Now we have the following:

COMM beatnote: 6dBm, DIFF beanote: -1.6dBm. When I get a chance again I will take a snap shot of the ALS camera images, but for reference these image is a bit clipped for both beams; however the transmission is good and the beatnotes are good so it's just the image.

Apparently, the end station temperatures are still drifting. This will affect the DIFF beatnote. Unfortunatly if EX drifts a lot we will need to re-do this input alignment again ...

I've added the archive image settings to the camera MEDM, and updated the INI files to make it work.  Currently, the archiving on all cameras is disabled by setting the interval to 0.  To enable archiving, set this value to 60 to save an archive image every hour (do not use a value less than this without good reason - we don't have infinite amounts of disk space available).  Archive images are saved to /ligo/data/camera/archive/YYYY/MM/DD when enabled.