I went push all the possible connectors for the MC3 shadow sensors including the SCSIs, flat cables and satellite box.

Also I put screws on them so that they won't become loose any more.

As a result UL_PDMON dropped from 0.6 V to 0.490 V and it becomes stable so far.

I didn't strain relief the cables but we must do it at some point before going into the full locking test.

It stacked again . We should take a closer look at it.

This was certainly my fault, probably left over from early debugging of my BO switch check script.  I've turned the ITMX whitening all off, to match the other suspensions.

Again, this was my fault.  Sorry.  I just accidentally left this off when I finished yesterday.  Much apologies.  I've turned the ETMX watchdog back on.

I resumed the pumping down. It started from 9:55 am.

I stopped the pumping at 14:50 pm because I was going back home. I did the same procedure as Koji wrote down (see here).

The P1 pressure reached 32 Torr.

Koji will take over the pumping shift tonight. 

I talked with Zach. So this is just a note for the others.

The setup I suggested was totally equivalent with the setup proposed in the entry http://131.215.115.52:8080/40m/1721, except that the PLL PD sees not only 29.501MHz, but also 1kHz and 59.001MHz. These additional beating are excluded by the PD and the PLL servo. In any case the beating at 1kHz is present at the camera. So if you play with the beamsplitter alignment you will see not only the perfect Gaussian picture, but also distorted picture which is resulted by mismatching of the two wave fronts. That's the fun part!

The point is that you can get an equivalent type of the test with fewer optics and fewer efforts. Particularly, I guess the setup would not be the final goal. So, these features would be nice for you.

I guess the ETMY suspension is still fine. Their OSEM DC voltage and the free swinging spectra look healthy.

It could be a failure in the initial guess for fitting.

 Turns out I was missing a critical step in the process...running makeSUSspectra.m  After I do that, everything is back under control, and ETMY looks fine. 

I'm almost done doing the peak-fitting and matrix inversion for all optics.

I believe that the 17 Hz broad structure on SIDE is just because of a bad rotational angle of the SIDE OSEM.

The same structure had been observed on the EMTY_UR, and the structure became narrower after we repositioned/rotated the OSEM yesterday.

My guess is that the SIDE OSEM is now in a place where the OSEM is quite sensitive to the bounce mode

and creating the broad structure due to a bi-linear coupling between the bounce mode and low frequency signals.

Here are the free-swinging spectra for the BS, ETMX, ETMY, ITMX, ITMY, MC1, MC2, MC3, and PRM chambers.  Kiwamu left the suspensions free for 5 hours this weekend, starting at Sat Apr 30 00:15:26 2011.

This is GPS time 988 182 941.  Quick tip: you can do local to GPS time conversions using lalapps_tconvert, which is a lot like tconvert but with special powers.  It is installed on pianosa.

$ lalapps_tconvert Sat Apr 30 00:15:26 2011

988182941

I generated these figures with the attached Python script, measure.py.

Notice that the C1:SUS-ITMX_SENSOR_UL and C1:SUS-MC3_SENSOR_UL spectra fall as 1/f.  Jenne suggested that this might indicate that there is a loose electrical connection.

Also, notice that C1:SUS-ETMY_SENSOR_LR, C1:SUS-ITMY_SENSOR_LL, and C1:SUS-PRM_SENSOR_SIDE are a lot noisier above 10 Hz.

Jenne went through all the suspension racks and pushed all the connectors.

After pushing them, we had a quick look at those spectra and found no funny noise spectrum except for C1:PRM-SENSOR_UL.

We then checked connection around the SCSI cables and eventually found the connection between ADC_card_0 and a SCSI was loose.

We put short standoffs on the ADC card so that the screws from the SCSI can nicely reach to the ADC card. Now everything looks fine.

SUS diagnostic is quite useful !

The Xarm is currently in its original state, all cables are connected and c1auxex is hosting the slow channels.

[Steve / Kiwamu]

Motivation:

 Since the oplevs were the ones we haven't carefully tested, so the oplevs need to be checked.

This checking is also a part of the suspension optimizations (see the minutes of the last 40m meeting).

 In this work Steve will check two things for all the oplevs :

    1. Noise level including the dark noise, electrical noise and ADC noise to just make sure that the noise are blow the signal levels below ~ 30Hz.

    2. The spectra of the signals to make sure there are no funny oscillations and unexpected structures

Measurement :

  To check the things listed above, we take two kinds of oplves' spectra :

     1. "dark noise" when the He-Ne beam is blocked.

     2. "signals" when the optics are damped by only OSEMs

 We did these checks on the BS oplev today (see the last entry).

All of them are fine, for example the dark noise (including electrical noise and ADC noise) are below the signal levels.

And no oscillation peak was found. Steve will go through all of the oplevs in this way.

I think the precision due to the loop gain uncertainty is something like 0.1% at 0.1 Hz. It's not the issue.

The real issue was the loud motion of MICH, which degrades the coherence of the measurement.

Also last night I tried the fringe hopping technique and gave it up for several reasons.

(uncertainty due to the loop gain)

(Effect from the MICH motion)

Indeed it was suspenseful.

We tried finding where the clipping happened, but we couldn't find any obvious clippings.

So we checked centering of the beams on all the optics associated with the AS path, starting from BS, SR3,... to the AS optical bench.

And during the work some of them were recentered.

At the end we found no clipping. To make sure we tested the available range (no clipping range) by exciting the angular motion of BS with AWG (f ~ 1Hz, a ~ 1000).

The beam looked successfully coming out at the most of the angular oscillation point.

[Keiko / Suresh / Anamaria / Kiwamu]

 The AM components do exist also on the beam after the EOM.

The peaks were found at 11, 29 and 55 MHz, where the PM are supposed to be imposed.

Suresh and Keiko minimized them by rotating the HWP, which is in front of the EOM.

Also Anamaria and I tried minimizing them by adjusting the EOM crystal alignment.

However everytime after we minimized the AM peaks, they grew back in a time scale of ~ 1 min.

Potentially it could be a problem of the HWP and/or EOM alignment.

Since we wanted to proceed the in-vac work anyways, we stopped investigating it and decided to postpone it for tomorrow.

We again adjusted the incident power to 20 mW.

-- P.S.

 The incident power going to MC went down to 7 mW for some reasons. This was found after ~ 6 hours from our works on the PSL table.

We haven't touched anything on the PSL table since the daytime work.

Possibly the angle of the HWP is drifting (why?) and changed the amount of the P-polarizing beam power.

Suresh locked the angles of two HWPs, which are the one just after the EOM and the one after the attenuation PBS.

2. Weighted screw rod at the bottom for tilting the mirror-holder:

The screw length selected here (2") is not interfering with any part of the assembly.

The 'weights' I have here are just thumb nuts from Mcmaster, so their weight is fixed (1.65g each, btw).

Problem I'd like to solve: Find an assortment of weighted, symmetric nuts with caps on one end to fix position on shaft. 

3. Set-screws on both side of wire clamp to adjust its horizontal position:

Thanks for pointing out the mismatch in travel distance of protrusion and clamp screws. To match them, the clamp screw slot now sticks out of the profile (by 1.5mm). The range of the clamp motion is +/- 3 mm.

Also, here's a screenshot of the slot in the mirror holder:

--

- Excluding the weighted screw rod assembly, the height gap between assembly COM and wire release point is 3.1 mm.

3.
- Do we need this much of extended range of the clamp location? How much range will we need if we use either 3/8 or 1/4 inch mirrors?
- This slot on the mirror holder ring is not machinable.

About the CoM height
- Include the angle adjustment screw and adjust the wire releasing point to have comparable pitch resonant freq to the SOS suspension.

P.S. There is a document about the 80MHz VCO box. This may be helpful. 

link to LIGO DCC

{Yehonathan, Anchal, Paco}

Yesterday, Anchal and Paco removed AS1 from the vacuum chamber and moved it into the cleanroom. The suspension wires were cut and the AS1 optic was put on the table.

Two things were noticed:

1. One of the wires was not sitting inside the side block groove (attachment 1)

2. One of the face magnets was grossly tilted (attachment 2). Probably due to uneven polishing of the dumbbell.

We put new wires into the side blocks making sure they sit in their grooves and we removed the tilted magnet. A different, more straight magnet was picked from the remaining spare magnets. The dumbbell and adapter were cleaned from glue residues and a batch of glue was prepared.

In the process of gluing a different magnet was knocked off. We cleaned that magnet too. The 2 magnets were glued on the adapter.

Today I came and saw that the gluing failed completely. One of the magnets was completely away from its socket and the other one wasn't glued at all.

I prepared a new batch of glue and glued the two magnets.

Yesterday, I rebuilt the OpLev setup in the cleanroom in order to suspend AS1. It took me a while to find all the necessary parts but I found them in the end.

The HeNe laser was placed on the optical table and turned on. The beam was aimed to bounce off a folding mirror to the SOS tower.

The beam's height was controlled by the HeNe laser stage and made to be 5+14/32". The beam from the folding mirror was made parallel to the table, first with an iris and then with the QPD connected to a scope.

Preparing the SOS tower for the suspension I noticed that the wire clamp is scratched on both sides from previous suspensions. I discarded that wire clamp but couldn't find the spares. Time ran out and I had to stop.

[Anchal, Paco]

Wire clamp spare was installed, furthermore AS1 was reinstalled on adapter, attached wire clamps, and cleaned using ionized air gun. Finally, we suspended it on the SOS tower and left it resting on the bottom earthquake stops; ready for balancing.

{Paco, Yehonathan}

We tried to roughly balance the adapter with two counterweights at the front, like with the other thin optics using an iris. As before, we couldn't get the beam above the iris hole no matter how much we inserted the counterweights into the adapter. We noticed that one of the side blocks is actually the one where the clearance for the wire was made on the wrong side. So there was clearance on both the up and bottom sides of the side block (see attachment 1).

Could this be the cause of the balancing issue? Running out of ideas on how to fix it we gave it a try and replaced it with a spare side block. We also found that the wire on the other side block was kinked so we replaced the wire on this one as well.

After inserting new wires into the side blocks, we hung the adapter on the winches and the beam was above the iris aperture! How could this tiny amount of missing mass make this much difference?

We were able to roughly balance the adapter.

We then tried to balance the roll of the adapter but accidentally knocked off the side magnet 😫.

We usually glue several side magnets together and they all together support the metallic plate on which the magnets are magnetically attached to. This time we had only one side magnet to glue so instead of trying to glue the magnet vertically we are trying to glue it horizontally using a flat surface and a stage to clamp it (attachments 2,3).

BTW, the HeNe was not working when we came into the cleanroom. We realized it was the old HeNe that we already determined to be broken but there was no sign on it. I attached a "BAD" sign on it and replaced it with the new HeNe. The OpLeve beam was realigned. All of this happened before all the things described above

Not sure if that small difference can cause the alignment inability. Particularly, the removed metal was just below the wire. This means that there is no misalignment effect at the first order.

Here is my idea:
You may be able to assist the alignment by adding washers on one side of the four holes to this "H" shaped parts. The holes are away from the center line, adding some weight definitely do some misalignment.

The gluing seemed to be successful. I assembled the side block with the magnet on the adapter. Paco helped me hang the adapter on the SOS tower.

The height and roll of the adapters were balanced (attachment 1,2).

The QPD was placed at the beam reflection. The beam was centered horizontally on the QPD and then measured vertically. The pitch DOF was balanced using the counterweights. The counterweight was locked. Balance was retained.

I tried to assemble the upper mirror clamp on the tower but for some reason, one of its tap holes was not able to accept screws. I gave it to Jordan for retapping. I measured the motion spectrum using the QPD connected to a scope (attachment 3).

Major peaks are at 668mHz, 942mHz, and 1029mHz.

Since I will need to do transfer function measurements in order to implement FF for the arms and the MC2's yaw and pitch channels, I decided to practice this by replicating the transfer function measurement Eric did for MC2 to MCL. I followed his procedure and the data that I aquired for the TF looked as shown below,

About five minutes of data were taken (0.05 Hz resolution, 25 averages) by injecting noise from 1 to 100 Hz. The TF coherence looked as below,

Thanh and I re-glued the magnet to the PRM following the procedure outlined by Jenne

The PRM in the gluing fixture has been placed in the little foil house and left to cure for a day.

If all goes well the balancing the PRM will be done tomorrow.

[Paco]

Installed AS1 in vacuum, near the center of the table, and installed the OSEMs. All OSEMS are "balanced" nominally, i.e. their shadow is at the halfway point optimum, but fine tuning is required, which I will attempt tomorrow after restoring the AS1 suspension screen settings. Today, I tried damping the SIDE DOF, but didn't succeed, although there was definitely some oscillating behaviour with high (> 5) gains on the damping, so I believe this is a matter of patience. For now, all OSEMs are looking ok, the SOS is in place, and hopefully it will soon be damped. 

[Paco]

AS1 is installed, OSEMs balanced, and the optic damped successfully. We should run the free swinging test overnight to validate this re-installation.

Fb is in a bad situation. It needs a MANUAL fsck to fix the file system.

HELP US, Jamieeeeeeeeeeee !!!

When Suresh and I connected a display and tried to see what was going on, the fb computer was in a file system check.

This was because Suresh did a hardware reboot by pressing a power button on the front panel.

Since the file checking took so long time and didn't proceed fast, we pressed the reset button and again the power button.

Actually the reset button didn't work (maybe ?) it just made some light indicators flashing.

After the second reboot the reboot message said that it needs a manual fsck to fix the file system. This maybe because we interrupted the file checking.

We are leaving it to Jamie because the fsck command would do something bad if unfamiliar persons, like us, do it.

In addition to it, the boot message was also saying that line 37 in /etc/fstab was bad.

We logged into the machine with a safe mode, then found there was an empty line in 37th line of fstab.

We tried erasing this empty line, but failed for some reasons. We were able to edit it by using vi, but wasn't able to save it.

fb was requiring manual fsck on it's disks because it was sensing filesystem errors.  The errors had to do with the filesystem timestamps being in the future.  It turned out that fb's system date was set to something in 2005.  I'm not sure what caused the date to be so off (motherboard battery problem?)  But I did determine after I got the system booting that the NTP client on fb was misconfigured and was therefore incapable of setting the system date.  It seems that it was configured to query a non-existent ntp server.  Why the hell it would have been set like this I have no idea.

In any event, I did a manual check on /dev/sdb1, which is the root disk, and postponed a check on /dev/sda1 (the RAID mounted at /frames) until I had the system booting.  /dev/sda1 is being checked now, since there are filesystems errors that need to be corrected, but it will probably take a couple of hours to complete.  Once the filesystems are clean I'll reboot fb and try to get everything up and running again.

fb is now up and running, although the /frames raid is still undergoing an fsck which is likely take another day.  Consequently there is no daqd and no frames are being written to disk.  It's running and providing the diskless root to the rest of the front end systems, so, so the rest of the IFO should be operational.

I burt restored the following (which I believe is everything that was rebooted), from Saturday night:

/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1lscepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1susepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1iooepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1assepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1mcsepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1gcvepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1gfdepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1rfmepics.snap
/opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Aug/27/23:07/c1pemepics.snap
 

I think you made a simple mistake in your diagram -- the mixer must be replaced by a summer circuit. Otherwise you cannot do the PDH lock.

Nulling the slow actuation offset fixed the issue. Now PMC is back to normal.

The reflected beam on the CCD was quite symmetric (it looked very TEM00 mode !) for some reasons, I somehow suspected the mode matching to PMC.

One possibility I thought of was the laser temperature because it could change the laser spatial mode.

So I looked at the slow actuation offset on the FSS screen and found it was at -4.0 which sounds somewhat big.

Then I zeroed the offset by the slider and relocked PMC.

Then the spatial pattern of the reflected beam became usual (i.e. junk light looking) and the transmitted light wet up to 0.83 which is normal.

[Jenne / Rana/ Kiwamu]

 We found the 30 Hz high pass filters had lower gain than what they used to be at low frequcnies.

So we increased the gain of the high pass filters called '30:0.0'  by a factor of 10 to have the same gain as before.

Now all the suspension shows some kind of damping. Needs more optimizations, for example Q-adjustments for all the suspensions...

I'm not convinced that this is what you want to do, or at least I wouldn't do it this way.  The "k" in the zpk filter was set such that the filter had unity gain above the high-pass cut-off frequency.  For a 30 Hz high-pass the k needs to be a factor of 10 smaller than it would be for a 3 Hz high-pass to achieve this high frequency unity gain.

As it is now these HP filters have 20 dB of gain above 30 Hz.  If the open loop transfer function needs to more gain I would have done that by adjusting the overall DC gain of the filter bank, not by increasing the gain in this one filter.  Maybe you guys have been doing it differently, though.  Or maybe I'm just completely off base.

So after talking to Kiwamu about it, I understand now that since the damping loops need all of this extra gain when the high-pass corner is moved up, it's more convenient to put that gain in the control filter itself, rather than having to crank the overall DC gain up to some inconveniently high value.

Figure.1  I-Q relative phase measurement as a function of LO power.

 Blue curve : relative phase of AS55 that I have modified today (#4572).

 Red curve : relative phase of AS11 that I had modified a week ago (#4554). Just for comparison.

 The relative phase of AS55 agrees approximately what we expected according to the datasheet of PSCQ-2-51W. We expected 85 degree.

Figure.1  I-Q amplitude imbalance as a function of LO power.

From - 5 dBm to 5 dBm in LO power the imbalance is within 3 %.

But the precision of the measurement is also about 2 % (because I used an oscilloscope). Even so the imbalance is still good.

I took a look at the data from the middle of the night to see if it was significantly quieter than the data from the day, but it doesn't seem to be. The plot shows data from yesterday around 12:30pm and from this morning around 2am. It's a bit quieter at low frequencies, but not by much.

Purpose

To use a razorblade to measure beam waist at multiple points along the optical axis, so as to later extrapolate the modal profile of the entire beam. This information will then be used to effectively couple AUX laser light to fibers for use in the frequency offset locking apparatus.

Data Acquisition

1) Step the micrometer-controlled razorblade across the beam at a given value of Z, along optical axis, in the plane orthogonal to it (arbitrarily called X).

2) At each value of X, record the corresponding output of a photodiode, (Thorlabs PD A55) here given in mV.

3) Repeat process at multiple points along Z

Analysis

Data from each iteration in the X were fitted to the error function shown below.

V(x) = A*(erf((x-m)/s)+c)

In the Y, they were fitted to:

V(x) = -A*(erf((x-m)/s)+c)

'A' corresponds to an amplitude, 'm' to a mean, 's' to a σ, and 'c' to an offset.

(Only because in Y measurements, the blade progressed toward eclipsing the beam, as opposed to in the X where it progressively revealed the beam.

These fits can be solved for x = (erf^-1((V/A)-c)*s)+m1  which can be calculated at the points (V_max/e²) and (V_max*(1-1/e²)). The difference between these points will yield beam waist, w(z).

Conclusion

Calculations yielded waists of: X1=66.43um, X2=67.73um, X3=49.45um, Y1=61.20um, Y2=58.70, Y3=58.89

These data seem suspect, and shall be subjected to further analysis.

 Eric Q and I set up the optical configuration for razorblade beam analysis on SP table for future use.

It has been aligned, and will be in use on Monday.

The beam will be characterized for future characterization of optical fibers.

Harry will update this elog with details about his beam waist measurements for the old NPRO on the SP table.

 see http://nodus.ligo.caltech.edu:8080/40m/10098 for the update

Reconfigured razorblade analysis setup on the PD table as per instructions. Used it to collect data to calculate beam waist with, analyses to follow.

See attached schematic for optical setup.

There is an intermittent rattling sound coming from the HEPA in the NE corner of the PSL table (right above the PMC, all of our input optics).

Steve says it might be a bad bearing, but he'll check it out in the morning and get it fixed.

 MC was having a hard time staying locked, with no discernable reason from the control room (i.e. no big seismic, no PMC PZT railing).    The HEPA was on 100%, so I turned it down to 50% to hopefully reduce the rattling, if that was what was wrong. 

The PSL HEPA stopped working while it was running at 80%. I have closed the PSL enclosure.

Steve is working to fix this.

A small rat / large mouse just ran through the control room. Ugh.

Two mechanical and two sticdky traps were set to catch univited visitor.

Absolutely no food or food remains into inside garbage cans!!!!!!!!!!!!!!!!!!!!!!!!!