Ah... no, I didn't. That explains why there were loose dogclamps on the table. I wrapped them in foil and put them on the clean cart. Can this wait until the next time we open the tank (i.e. to measure the beam profile), or should I go over there and clamp it down today?

Fixing at the next time is absolutely OK.

PDA255 at the MC transmission end is missing and whoever had removed it earlier has left the beam undamped.

It could be less than a mW beam...but it is still not acceptable to leave it that way.

On the other note, I have cleared up the unwanted optics from the same table.

As usual, I noticed several bad things within 30 seconds of sitting in front of the workstation. Today its that there are OFF or missing filters on the MC TRANS.

is this the normal state? Screenshot attached.

I was looking at the trends from the RAMmon, since I did the EOM alignment yesterday, and wanted to compare them to the MC trans, just to make sure the MC was locked during the times I'm examining.  I was dismayed to discover that the MC has lost its oomph, starting around 11:30 this morning.  Den was the only person in the lab to my knowledge at that time, and he claims that he didn't touch the MC until well after lunch.  As you can see from the 8 hour trend attached, we went from normal ~26000 counts to ~15000, and we're slowly decaying from there.

MC refl looks pretty bad on the camera, particularly in YAW.  Investigations are beginning now....

Edit, ~10min later...  I enabled the WFS (I don't know why they were off...when the MC fell out of lock and relocked itself, the WFS didn't come on), and things went basically back to how they should be.  However, the sans-WFS alignment is still totally crappy, so the PSL beam probably needs to be aligned to the MC.  I don't really want to touch the alignment though without an okay from Kiwamu, so I'll wait for him to come in and confirm that he's happy with the current MC.

 Kiwamu and I discussed, and looking at the AS camera with the PRM and SRM misaligned, but MCWFS engaged, things look good.  This means that it's probably the MC that has drifted, and we want to align the MC back to the PSL beam.

When dialing up the current, I went up to 2.01 A on the front panel display, which is what I remember it being. The label on the controller is from when the laser was still putting out 2W, and says the pump current should be 2.1 A. Anyhow, the MC transmission is ~7% lower now (14500 cts compared to the usual 15000-15500 cts), even after tweaking the PMC alignment to minimize PMC REFL. Potentially there is less power coming out of the NPRO. I will measure it at the window tomorrow with a power meter.

Jan and I wanted to measure the ringdown at the IMC. Since the QPD at the MC trans is not fast enough for ringdown measurements, we decided to install a pickoff to include a faster PD while not disturbing much of the current MC trans configuration. The initial configuration had very little space to accommodate the pickoff. So the collimating lens along with the QPD were moved 2 inches closer to the incoming beam. A 50-50 BS was put in front of the QPD and the steering mirror was moved behind to reflect MC trans output to the new PD. The current configuration is shown below with the MC autolocker threshold mentioned in Jenne's elog

The hunt for a faster PD wasn't satisfactory and we found a couple of PDs that were good for measurements actually didn't work after installing them. The one currently installed is also not satisfactorily fast enough for ringdown measurements. We'll hunt for faster PDs at Bridge tomorrow and replace PDA400. Also the IMC unlocked from time to time....may be we were noisy and didn't master the 'interferometer walk' very well.

  The PDA255 is a good ringdown detector - Steve can find one in the 40m if you ask him nicely.

 We found a PDA255 but it doesn't seem to work. I am not sure if that is one you are mentioning...but I'll ask Steve tomorrow!

 I double checked the PDA255 found at the 40m and it is broken/bad. Also there was no success hunting PDs at Bridge. So the MC trans is still in the same configuration. Nothing has changed. I'll try doing ringdown measurements with PDA400 today.

Can you explain more what "broken/bad" means?  Is there no signal?  Is it noisy?  Glitch?  etc.

 The PD saturates the oscilloscope just by switching on the power; with no real signal at all. But Steve helped locating a PD that is not being used at the AP table. So I will check it and replace the current one if it works!

Koji opened up the PD and found that the screw connecting the PD to the pole was doing an additional job as well; connecting the power cable to the PD output in the inside. The PD is now fixed! Yippie...we have two PDA255 s at 40m now!!

I re-aligned the beam onto the MC TRANS QPD since Kiwamu had centered the spots on the mirrors. However, I then inspected the MC2F camera. After coming back into the control room I noticed that the MC transmission had gone down by 50% and that the MC2 OSEMs showed a large step. My guess is that somehow the opening and closing of the can shifted the suspension. So I adjusted the MC2 alignment biases to recover the transmitted power (its now ~50000 instead of the ~33000 from Friday).

We moved the MC-trans pick-off mirror (= the beam splitter between the input of the Faraday and the steering mirror located right after MC3). Now the beam goes through the Farady without getting clipped.

This is the list of the things that have to be done next:

1. take pictures of the beam spot just before and after the Faraday
2. lock down to the table the MCTrans pickoff mirror with its screws
3. measure the beam profile after the first MC telescope mirror (MMT1)
4. remove Jenne's extra steering mirror from the MC table
5. re-level the MC table with the bubble level
6. align the MC-trans beam to its photodiode on the PSL table
7. align the REFL beam to its photodiode on the AP table

I found MC unlocked this morning. I looked at the 2 day trend of the MC suspensions and found MC2 suspensions have been misaligned.

I used Rana's ezcaservo trick to recover MC lock. This brought the MC_REFL down to 0.7 counts. I did the rest of the alignment by moving the MC2 suspension sliders only. MC_REFL is down to 0.45-0.5 counts and TRANS_SUM is at ~16300.

Also, I found the WFS servo was left turned OFF. I re-enabled them as well.

I tilted the periscope beam and aligned the MC.  Now the spot at the Faraday entrance is near the center of the aperture in up/down space.  The arm powers are only going up to ~0.8, though.  Maybe we should try a little bit of left/right. 

I looked at the IP POS spot with a viewer card, and it looked round, so no obvious egregious clipping in the Faraday.  Someone might take a picture with one of the GigE camera and get us a beam profile there.

We no longer have an MC1 and MC3 camera view.

I can see a bright scatterer that can be seen from the east viewport of the BSC, but I can't tell what it is.  It could be a ghost beam. 

It would be nice to get an image looking into the north viewport of the IOO chamber.  I can't see in there because the BS oplev table is in the way. 

I've asked Manasa and Q to have a look at the MC in the morning.  Rana and I have found it to be slightly uncooperative in relocking after a lockloss.

We have found that just letting the autolocker go doesn't seem to work very well, and sometimes the MC just doesn't want to re-lock.  Closing the PSL shutter or disabling the autolocker for a few minutes (5ish) doesn't do anything, but leaving it closed for a long time (30 ish minutes) helps a lot.  The MC  will relock immediately after a nice long break. 

Friday afternoon the mode cleaner got unlocked. Then some adjustment of the MC1 bias sliders locked it again. The driftmon showed the excursion for pitch and yaw of MC1 becasue it wasn't updated after the change.

Tonight Rana found the MC unlocked and simply touched the sliders to bring the OSEMs back to the driftmon values.

MC1 Yaw remains different from the driftmon. If brught back to htat value, the MC would get unlocked.

More investigation is needed to understand why the MC lock hasn't been stable for the last few days.

 The mode cleaner is still unlocked. I played with the cable at the MC2 satellite to enusre they were all plugged in.

Then I tweaked the the mirrors alignment by the sliders and eventually I could get it locked stably with 1.3 reflection. Then I rebooted C1IOO because the WFS wouldn't engage. After that the cavity wasn't locked anymore. Trying to adjust the mirrors around their position didn't restore the lock.

More work is necessary.

I'll be back on it in a while.

MC is unlocked to measure the free swing of the MC mirrors with the local sensors.

Autolocker is disabled.

MC fell out of lock and was then quite badly misaligned. Mostly in pitch. I realigned it and it locked ok.

Turns out the MC falls often out of lock when the WFS servo comes on. I think the MC2_Trans history is not cleared on lockloss. I cleared it manually and realigned. Seems fine for now.

Actually, do we need to reset the filter history at every lock loss of the MC?

Those DC offsets were necessary to keep the alignment good just until the MC is unlocked.
So if we keep the history, we can maintain the good alignment.

 I suspect the integrators get fed a huge wrong signal on lockloss. Clearing the history on the trans DOFs when the MC was badly aligned gets it nicely aligned again. I switched off the alignment transmission DOFs for now.

I have modified the 'mcwfson' and 'mcwfsoff' scripts to include the Clear History step for the MC2_TRANS_PIT and _YAW filters.  

These scripts can be run, by hand, from LOCKMC screen or from the WFS_MASTER screen.  Use the 'Turn WFS ON/OFF' button. 

The mcautolockmain script will now clear history on all ASC filter banks when the MC unlocks.

I have turned on ASC loops on the MC2_TRANS (= alignment transmission DOFs of the above elog) paths.

Came in at ~ 9 PT this morning to find the IFO "down". The IMC had lost its lock ~ 6 hours before, so at about 03:00 AM. Nothing seemed like the obvious cause; there was no record of increased seismic activity, all suspensions were damped and no watchdog had tripped, and the pressure trends similar to those in recent pressure incidents show nominal behavior (Attachment #1). What happened?

Anyways I simply tried reopening the PSL shutter, and the IMC caught its lock almost immediately. I then locked the arms and everything seems fine for now .

The MC became crazy again.

It seems that there were corresponding steps in the OSEM signals. Look at the one-day trend posted below.

As we've been seeing a bit lately, the MC will be locked happily for several hours, but then it will start misbehaving. 

Today, I measured the spots on the MC mirrors, and found that the MC2 spot was quite far off in yaw (about -3.5 cm).  I recentered the MC2 spot, and then (with the MCWFS on), moved MC1 and 3 until their WFS outputs were close to zero (they had gone up to 100+).  In the ~15 minutes since doing that, the MC refl signal is not oscillating like it was, the transmission is up, and the MC has not unlocked. 

To reiterate, I did not touch any settings of anything, except the alignment of the MC mirrors to center the MC2 spot, and then offload the WFS.  Next time the MC starts acting up, we should measure the spots, and roughly center them, before messing with any other settings.  Note however, that this is a ~10 minute procedure (including the fact that one spot measurement takes a little less than 5 minutes).  This need not be a several hour endeavour. 

Not sure why it was so poorly aligned, since the misalignment "event" happened while we were all away at lunch, but I steered the MC optics until their SUSYAW and SUSPIT values were about the same as they were before they got misaligned.  MC autolocker took over, and things are back to normal.

The MC was not damping earlier this morning around 11:45AM.  The reason was that the INMATRIX on all the three MC1, 2 and 3 were zero.   This was seen earlier when autoburt did not restore this.

This got fixed when I Burt-Restored c1mcsepics.snap

In the afternoon we had to restore c1mcs again to restore the MC_TRANS channels because its INMATRIX was also zero.

Can we do something to make sure this gets done in the autoburt properly?

[Kiwamu, Suresh]

The MC was realigned to readjust the input beam direction in pitch such that the clipping of the beam at the PSL table reduced and the railing of the PZT1 is avoided.

The current spot positions are given below on the last row:

We have quite a lot of decentering in the MC which we must try to remove by parallel transporting the beam in Pitch and Yaw..

At the current settings we might be clipping on the Faraday Isolator as we had estimated that we can allow atmost a 2mm offset in spot positions due to this constraint.

[Rana / Mirko / Kiwamu]

 The watchdogs on the MC suspensions are not working.

Switching off the watchdogs doesn't stop feeding signals to the suspensions.

For tonight, we will leave the controller of the MC suspensions switched off so that the computer won't smash the optics accidentally.

It seems as if someone was looking into this on Wednesday, but as there's no elog, I think probably not.

Tonight we noticed that, in fact, the watchdogs don't work for any of the corner optics (I confirmed that they do work for the ETMs).

Whether the switch for the coil drivers is enabled or disabled, the voltage monitor on the coil drivers responds to the digital signals.

I tried restarting the c1susaux process, hitting reset on the crate, and also keying the crate. The +5V light on the front of the crate is flickering somewhat, but I'm not sure if this is new or not since the power outage. The next step is to track the Xycom signal from the card over to the coil driver to find where the signal is failing to happen.

Since its not working for any of the corner optics, I suspect the crate and not the cards. If that's the issue this will be a painful fix. We are sort of assuming that this is due to the power outage, but in fact, I cannot tell when the last time was that someone rigorously verified the working of these switches. [

I][B]We had better get ready for upgrading our SLOW controls, Jamie.[/B][/I]

~20 minutes ago, maybe right around the time the fb's RAID died (elog 8274) the mode cleaner started behaving weirdly again.  The reflected value is very high, even with the WFS on.  Earlier this evening, I saw that with the WFS off, the MC reflection was high, but the WFS brought it back down to ~0.7 or 0.8.  But now it's ~1.3.  With the WFS off, the reflected value is ~1.1.  I don't really understand.

Also, the PMC has been drifting in alignment in pitch all day, but a lot more later in the day. The PMC trans is 0.800 right now, but it was as high as 0.825 today, and spent most of the day in the high 0.81xxx range today.

I would provide plots, but as mentioned in elog 8274, we can't get data right now.

[Manasa, Annalisa, Jenne]

The MC wasn't locking on TEM00 this morning, and the WFS kept pulling the MC out of alignment.  The MC was realigned, and the WFS spots are back to being roughly centered (all of this only touching the MC sliders), but the WFS keep doing bad things.  They're okay, and improve the alignment slightly at first, but as soon as the FM1 integrator comes on, the MC alignment immediately starts going bad, and within a second or so the MC has unlocked.

The WFS are off right now, and we'll keep investigating after LIGOX.

[Jenne, Manasa, Yuta]

Since we levelled IMC stack, we had to center beam spots on MC mirrors again.
We did this by steering PSL mirror in yaw (about same amount but opposite direction to what we did in elog #8077)
Residual beam tilt compared with a line through MC1 and 3 actuator nodes is ~ 15 mrad, mainly in yaw.

The mode cleaner is super unhappy.  It's rocking around at ~1Hz.

I turned off the WFS and turned them back on after the MC was locked, and it seems a little happier now.  At least it's not falling out of lock ~1/minute.

Regarding http://nodus.ligo.caltech.edu:8080/40m/5867 and http://nodus.ligo.caltech.edu:8080/40m/5869 :

MC_F signal:

The measurements on p. 5867 were done using the ADC attached to the PEM computer. There was a big difference between the MC_F signal recorded directly after the server board and the signal just before the FSS board as recorded by a PEM channel.
To understand how this happens we measured the signal at different places with a spec. analyzer:

1. WIth a locked MC measuring the signal just before the PEM ADCs (meaning after a 60ft BNC cable)
2. Same position, but unlocked and seemingly dark MC
3. Locked MC, signal just before the FSS box
4. MC_F signal that is usually going into the Pentek Generic board and is recorded in C1:IOO

=> The 60ft BNC cable adds a considerable amount of noise, but doesn't fundamentally change the signal. It is weird that the signal is white from approx. 4Hz on.
Due to Jenne's measurement ( http://nodus.ligo.caltech.edu:8080/40m/5848 ) we know the TF from MCL through PD, mixer Pentek and into C1:IOO looks like this:

This is with the double HP from 15Hz on that should be in the Pentek. So one might expect a less white signal going into the FSS board...

 PEM ADCs

The dark noise in the PEM ADCs is actually a factor 10 higher than in the IOO ADCs. Still ok wrt the the seismometers.
We also tried to measure essentially the dark noise of the whole seismometer readout (seismometer box, then ADC). That seemed ok, but is of limited value since the seismometer electronics behave a bit strange when there is no seismometer connected.

I tried unsuccessfully to relock the MC this afternoon.

I came in to find it in a trouble state with a huge amount of noise on C1:PSL-FSS_PCDRIVE visible on the projector monitor. Light was reaching the MC but it was unable to lock.

• I checked the status of the fast machines on the CDS>FE STATUS page. All up.
• Then I checked the slow machine status. c1iscaux and c1psl were both down. I manually reset both machines. The large noise visible on C1:PSL-FSS_PCDRIVE disappeared.
• After the reset, light was no longer reaching the MC, which I take to mean the PMC was not locked. On the PSL>PMC page, I blanked the control signal, reenabled it, and attempted to relock by adjusting the servo gain as Gautam had showed me before. The PMC locks were unstable, with each one lasting only a second or so.
• Next I tried restoring the burt states for c1iscaux and c1psl from a snapshot taken earlier today, before the machine reboots. That did not solve the problem either.