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ID Date Author Type Categoryup Subject
  770   Wed Jul 30 15:12:08 2008 ranaSummaryIOOHistory of the MC abs length
> I was notified by Rob and Rana that there were many measurements of the MC abs length (i.e. modulation
> frequencies for the IFO.) between 2002 and now.

I will just add that I think that the Marconi/IFR has always been off by ~150-200 Hz
in that the frequency measured by the GPS locked frequency counter is different from
what's reported by the Marconi's front panel. We should, in the future, clearly indicate
which display is being used.
  829   Tue Aug 12 19:48:24 2008 JenneUpdateIOOPRM standoff is in....mostly
Yoichi, Jenne

The missing PRM standoff is now partially installed. The standoff is in, and the wire is in the groove, but we have not finished adjusting its position to make the PRM stand up straight. It turns out to be pretty tricky to get the position of the standoff just right.

We have set up a HeNe laser as an oplev on the flow bench (which we checked was level) in the clean assembly room, and are using it to check the pitch of the mirror. We set a QPD at the height of the laser, and are looking at the single-reflected light. When the single-reflected light is at the same height as the center of the QPD, then the mirror is correctly aligned in pitch. (Actually, right now we're just trying to get the single-reflected light to hit the diode at all...one step at a time here).

We'll continue trying to align the PRM's standoff in the morning.
  837   Thu Aug 14 19:35:54 2008 JenneSummaryIOOPRM in the chamber, ready to pump!
Rob, Yoichi, Jenne, Steve

Summary: Everything is back in the chamber, we just need to put on the big doors, and start pumping in the morning.

After letting the PRM's standoff epoxy cure overnight, it was time to put the optic back in the BS Chamber. Rob put the optic cage back in the chamber, as close to the guide points that Rana had placed as possible. A handy technique was discovered for pushing the cage into place: put a long screw into the table, leaving an inch or so above the table, then use that as a push-off point so that you can push the base of the cage with your thumb. According to Rob, this is probably just about as effective as using a pusher-screw.

The guides were helpful in getting the PRM back to its original position, but one of them was placed in such a way that it could move when pushed against. The clamp that was used as a guide point was placed with one of the screws half on the edge of a hole, so that when the cage was pushed against the guide point, that screw could wiggle around, causing the clamp to rotate thus no longer being a definite guide point.

Just after putting the PRM in place, Rob found the standoff that had gone missing. (see elog #835)

Once the PRM was back in place, we put the OSEMs back, and reinstalled the satellite boxes that had been removed (PRM's, which Ben has fixed - an op-amp was blown, and BS's, which we used over in the clean room with the spare OSEMs). We found a problem with the LR PRM OSEM reading on Dataviewer. It was saturating when the OSEM was just sitting on the table, with nothing between the LED and the sensor. We measured the output from the satellite box with the octopus cables, and measured 2.3 volts, which is too much for the DAQ. It seems fine when we install it in the cage, and the magnet is blocking part of the light. We should investigate the gain of the satellite box when convenient. This is not something that needs to be done prior to pump-down. Also, when we put an allen wrench to block the light while checking which OSEM was which, we noticed that the Dataviewer reading would go down to -2V, then come back to 0V when the light was completely blocked. This may be some incorrect compensation for some whitening. Again, we should look into this, but it is not terribly time-sensitive.

Once the OSEMs were centered, we tried to turn on the damping for the PRM. This was successful, so we are confident that we have put all of the OSEMs back in their correct places.

We found that we were easily able to get the PRM's oplev back on the QPD, so we ~centered the oplev, and then centered all of the PRM's OSEMs. This assumes that the oplev was in a good place, but I think we've determined that this is the case.

We did the same thing for the SRM and the BS, to check the OSEM values before we close up for good. We found that some of the SRM OSEMs were reading low (magnet too far in), and that all of the BS OSEMs were low, perhaps as if the table were tilted a tiny bit after removing and replacing the weight of the PRM. We recentered all of the OSEMs for both of these optics.

We checked that all of the pigtails for the PRM OSEMs were anchored to the PRM cage using some copper wire as tie-downs.

We checked that all of the earthquake stops were within 1mm or so of each of the 3 optics in the BS chamber. The SRM's earthquake stops were fairly far out. One of the bottom ones was far enough that when Yoichi turned it the wrong way (accidentally), it fell out. He put it back in, and adjusted all of the earthquake stops appropriately. This 1mm distance comes from Seji, and the specs for the optics' cages.

We did a look-through of the chamber, and took out all of the tools, and other things that were not bolted down to the table.

We have left the damping of the PRM off for the night.

To do: put the doors back on, and start the pump down.
  849   Mon Aug 18 22:47:12 2008 YoichiUpdateIOOMC unlock study
As rob noted, the MC keeps unlocking in a few minutes period.
I plotted time series of several signals before unlocks.
It looks like the MC alignment goes wrong a few hundred msec before the unlock (the attached plot is only one example, but all unlocks
I've looked so far show the same behavior).
I will look for the cause of this tomorrow.

The horizontal axis of the plot is sec. The data values are scaled and offset-removed appropriately so that all curves are shown
in a single plot. Therefore, the vertical axis is in arbitrary units.
  856   Tue Aug 19 18:55:41 2008 YoichiUpdateIOOMC unlock study update
In entry 849, I reported that the MC transmitted power drops before the sudden unlocks.
However, because C1:IOO-MC_TRANS_SUM is a slow channel, we were not sure if we can believe the timing.
So I wanted to use C1:IOO-MC_RFAMPDDC, which is a fast channel, to monitor the transmitted light power.
However, this channel was broken. So I fixed it. Details of the fixing work is reported in another entry.
The attached plot shows a recent unlock event. It is clear that in the fast channel (i.e. C1:IOO-MC_RFAMPDDC),
there is no delay between the drop of the MC power and the crazy behavior of control signals.
So it was concluded that the apparent precedence of the MC power drop in the slow channels (i.e. C1:IOO-MC_TRANS_SUM)
is just an artifact of timing inaccuracy/offset of the slow epics channels.

Sometime around 5PM, the MC started to be unwilling to even lock. It turned out that the PC drive of the FSS was going
crazy continuously. So I changed the normal values of the common gain and the fast gain, which the mcup script uses.
Now with this new setting, the MC locks happily, but still keeps unlocking.
  864   Wed Aug 20 18:09:48 2008 YoichiUpdateIOOMC still unlocks
Being suspicious of FSS PC path as the culprit of the MC unlocks, I opened the FSS box and connected a probe to the TP7,
which is a test point in the PC path (before high voltage amplifier).
The signal is routed to an unused fast DAQ channel in the IOO rack. It is named C1:IOO-MC_TMP1 and recorded by the frame
builder. You can use this channel as a generic test DAQ channel later.

By looking at the attachment, the PC path (C1:IOO-MC_TMP1) goes crazy at the same time as other channels. So probably
it is not the trigger for the MC unlock.

Then I noticed the WFS signals drift away just before the unlock as shown in the attached plot. So now the WFS is the
main suspect.
Rob tweaked MC1 pitch to center the WFS QPDs while the MC is not locked. It improved the shape of the MC reflection.
However, the sudden MC unlock still happens. We then lowered the WFS gain from 0.5 to 0.3. Did not change the situation.
It looks like the MC length loop starts oscillating after the WFS signals drift away.
We will measure the WFS and MC OPLTF to see the stability of the loops tomorrow.

  867   Thu Aug 21 17:55:14 2008 ranaHowToIOOMC WFS DC Offsets
I ran the McWFS_dc_offsets script to trim out the DC offsets on the MC WFS DC signals.

Rob says "who cares?"
  868   Thu Aug 21 18:13:24 2008 ranaUpdateIOOMC WFS Control signals not responsible for lock losses
This is a 4 hour, second-trend of the MC WFS error and control signals.

There is no sign that the MC loses lock because of feedback signal saturations.
  872   Fri Aug 22 17:03:41 2008 YoichiUpdateIOOMC open loop TF
I measured the open loop TF of the overall MC loop using the sum-amp A of the MC board.
I used the Agilent 4395A network analyzer and saved the data into a floppy disk. However, the data was corrupted when
I read it with my computer. I had the same problem before. The floppy is not reliable. Anyway, I have to re-measure the TF.
From what I remember, the UGF was around 25kHz and the phase margin was less than 15deg.
Above this frequency, the open loop gain was almost flat and had a small bump around 100kHz.
This bump has a gain margin of less than 4dB (the phase is more than 180deg delayed here).
So the MC is marginally stable and either decreasing or increasing the gain will make it unstable easily.
Probably, the broken FSS is responsible for this. We have to fix it.

During the measurement, I also found that the input connectors (IN1 and IN2) of the MC board are freaky.
These are TNC connectors directory mounted on the board. Gently touching the cables hooked up to those connectors
caused a large offset change in the output.
When Rana pulled the board out and pushed it in firmly, the strange behavior went away. Probably, the board was
not correctly inserted into the backplane.
This could have been the reason for the MC unlocks.
  877   Mon Aug 25 11:43:55 2008 YoichiFrogsIOOMC REFL PD cable had been disconnected through out the weekend
Most of my morning was wasted by the MC REFL PD cable, which was disconnected on the generic LSC PD interface board.
I know who did this. *ME*. When I pulled out the MC board, which is sitting next to the PD interface, on Friday, I must have
disconnected the PD cable accidentally. The connector of the PD cable (D-Sub) does not have screws to tighten and easily comes off.
I wrote this entry to warn other people of this potential problem.
  920   Thu Sep 4 07:46:10 2008 YoichiUpdateIOOMC is now happy
The MC has been locked for more than 12 hours continuously now !
Changes I made yesterday were:
(1) Removed the 20dB attenuator before the EOM.
(2) Reduced the Fast Gain from 21dB to 16dB, which made the PC to be a little bit more loaded (~0.6Vrms).

As Rana pointed out in the meeting, setting the Fast Gain a bit lower may have put the FSS in a stabler state.
  921   Thu Sep 4 10:13:48 2008 JenneUpdateIOOWe unlocked the MC temporarily
[Joe, Eric, Jenne]

While trying to diagnose some DAQ/PD problems (look for Joe and Eric's entry later), we unlocked the PMC, which caused (of course) the MC to unlock. So if you're looking back in the data, the unlock at ~10:08am is caused by us, not whatever problems may have been going on with the FSS. It is now locked again, and looking good.
  928   Thu Sep 4 17:17:03 2008 YoichiUpdateIOOMC open loop TF
I measured open loop transfer functions of the MC servo.
The UGF was about 30kHz. Since there was some gain margin at higher frequencies, I increased
the input gain of the MC servo board from 19dB to 22dB. Now the UGF is 40kHz and we have more
phase margin (~30deg).
  935   Mon Sep 8 10:57:49 2008 steveUpdateIOOthe psl and mc are back to normal
The alarm handler is silent this morning.
This is almost unbelievably pleasant after two mount of harassment.
The MC did not lose lock for three days.

Atm1: the new fss layout
Atm2: PMC with lead brick
Atm3: 3 days plot
  952   Wed Sep 17 12:55:28 2008 robConfigurationIOOMC length
I measured the mode cleaner length last night:

SR620                Marconi
                     199178070
165981524            165981725
                     132785380
                      33196345


I did the division in Marconi-land, rather than SR620-land.
If someone wants to do this in SR620-land, feel free to do it and post the numbers.
  968   Fri Sep 19 00:06:54 2008 ranaUpdateIOOMC_F: Too much frequency noise around 100 Hz
WE noticed this excess again in MC_F. We tried recentering the WFS, but no effect.

Also no effect from changing the FSS gain, PMC gain, or ISS gain.

Actually, there IS a change when changing the PMC gain -- the ISS can be made to saturate
by lowering the PMC gain by 10 dB. Jenne and I need to finish off the PMC loop.

10 kHz UGF or bust!
  993   Thu Sep 25 15:24:05 2008 YoichiUpdateIOOMC_F VCO calibration
I calibrated the VCO driving the AOM for the AO path of the MC feedback.

I injected DC voltage to the VCO and measured the output frequency with the SR620.

The attached plot shows the relation between the input voltage to the VCO and the output frequency.
The coefficient is 1.75MHz/V. Since the AOM is double path, the actual actuation efficiency is 3.5MHz/V.
We can use this value for the calibration of the MC_F. However, the MC_F DAQ channel is sampling the VCO input voltage through a 10Hz high-pass filter.
This filter has to be taken into account to convert the MC_F counts to frequency.
I will measure the transfer function from the VCO input to the MC_F counts tomorrow.
  999   Fri Sep 26 16:13:57 2008 ranaUpdateIOOMC_L / MC_F crossover
We were trying to understand why the FAST_F signal had such large excursions (~1V ~ 5 MHz).

Some of this is due to the seismic noise and the resulting MC_F signals. Increasing the MCL
gain reduces it somewhat. But as you can see from the attached loop gain measurement, the
crossover is a healthy 90 Hz with the MCL digital gain = 1. But what's going on in the MC loop
in the 10-20 Hz band? That looks like bad news.

Then I noticed that changing the ISS gain slider puts a large step (~1V) into the FAST. My guess
is that the board has large DC offsets and also much of the switching supply noise. Not sure why
this would be worse than before though.

To prevent large noise in the FAST, I've changed the mcup script to set this gain to -5 dB. Our
intensity noise is now presumably 10-15 dB worse than the nominal good levels we had a year ago.
Needs investigation.
  1002   Fri Sep 26 19:18:39 2008 JenneUpdateIOOMC2 is having a bad day
As Steve mentioned earlier in today's elog, MC2 keeps ringing up for no clear reason. It is definitely only MC2 that is ringing up, since it's sensors will read several hundreds of counts, while all the other optics are at regular 2 counts and below on the Watchdog screen.

Preliminary investigation results: Around the time of these "kick up" events, the Ranger seismometer does not see any motion, nor does the set of accelerometers under the MC1 chamber. The set of accelerometers under the MC2 chamber do see activity that is at the same time as these events. These events are not caused just by someone walking around, since Rana went inside and clunked around near MC2 while I watched the sensor levels. MC2's watchdog did not trip.

For further investigation: Why is it that only the MC2 accelerometers are seeing the motion? Similarly, why is MC2 the only optic being kicked? Has anyone done anything lately to the MC2 stack?
  1012   Wed Oct 1 02:10:03 2008 ranaUpdateIOOMZ is going bad
Here's a 2 day trend of the MZ. You can see that there is something bad with ERR - it should really be going to zero.

Also LODET is dead. We need to rejuvinate LODET somehow.

The next plot is a 90 day hour-trend of the same signals. You can see that LODET came back to us between
September 10 and 19 ??? I looked at a 4 year trend and it seems that this signal has always been zero
(nice use of disk space) except for a few days in Nov of 06 and then whatever happend on Sep 10.
  1022   Fri Oct 3 12:15:21 2008 AlbertoConfigurationIOOC1iool0 rebooted
This morning, in order to update the threshold values of the alarm handler for the StochMon, I rebooted the C1iool0 computer following the procedure in the wiki, that is telnetting on it and typing CTRL+X. Apparently everything went well in the process.
  1032   Tue Oct 7 21:19:40 2008 YoichiUpdateIOOMC_F calibrated spectrum
I updated the plots because I did not take into account the double path AOM effect, which doubles the frequency actuation efficiency. (2008/10/8)

I determined the MC_F counts to the PSL frequency change calibration.
The attachment 1 is the calibrated MC_F spectrum, which is, above the cross over frequency, equivalent to the frequency noise seen by the MC.

The calibration method is the following:

1) I picked spare AD and DA channels (C1:IOO-MC_TMP1 and C1:OMC-SPARE_DAC_CH_16_EXC). C1:OMC-SPARE_DAC_CH_16_EXC is labeled C1:OMC-OSC_FM on the cable.

2) C1:IOO-MC_TMP1 was calibrated by injecting a sine wave of known amplitude and measuring the amplitude in counts in dataviewer.
It was 63uV/cnt.

3) C1:IOO-MC_TMP1 was connected to the feedback BNC connector of the MC board, that is the direct monitor of the feedback voltage to the VCO.

4) C1:OMC-SPARE_DAC_CH_16_EXC was connected to the channel B excitation input of the MC board, which adds the signal to the fast feedback path.

5) Using DTT a swept sine signal was injected to the MC board through C1:OMC-SPARE_DAC_CH_16_EXC, and the transfer function from C1:IOO-MC_TMP1 to the
C1:IOO-MC_F was measured.

6) Using the calibration of C1:IOO-MC_TMP1, the transfer function from the MC_F count to the actual voltage applied to the VCO input was obtained.
(attm2)

7) Using the DC calibration of the VCO input voltage to the VCO frequency change (1.75MHz/V elog:993) and the fact that there is a 1.6Hz pole and a 40.8Hz zero between the VCO input connector and the actual input of the VCO chip, the final calibration transfer function from the MC_F count to the frequency change of the PSL (that is twice the frequency change of the VCO within the bandwidth of the FSS) can be obtained (attm3).

8) The analytic form of the calibration TF is, poles at [1.6Hz, 11.42Hz, 11.42Hz] and zeros at [40.8Hz, 113Hz, 113Hz] with the DC gain of 110Hz/cnt.
  1081   Fri Oct 24 10:06:16 2008 YoichiConfigurationIOOMC gain and FSS gain changed
Following the measurements of MC and FSS loop gains, I modified mcup script to set the MC VCO gain to 2dB (it was -4dB before).
I also changed the normal value of the FSS common gain to 7dB. The open loop transfer functions posted in the previous two entries
were measured with those settings.
  1093   Mon Oct 27 11:16:23 2008 AlbertoConfigurationIOOStochMon Calibration
I implemented the calibration for the four channels of the StochMon in the ioo EPICS database. Now the output of those channels, as shown in the medm screen, gives the peak-to-peak amplitude in voltage of each frequency from the RFAMPD at the transmission of the MC, normalized by the DC output from the same photodiode.

Basically the calibration takes into account the following factors:
- two in series RF preamplifiers, currently laying on the PSL table near the RFAMPD, with gains of 19 dB and 17 dB, respectively
and, inside the StochMon blue box:
- a resonant band-pass filter with the following gains h_f(f) for each of the frequencies of interest: 33MHz -39.5 dB; 133MHz -40.8 dB; 166MHz -49.0 dB; 199MHz -45.0 dB
- a power detector that provides an output voltage linearly proportional to the input power in dBm, with a factor alpha of proportionality equal to an average value of -0.0271 V/dBm for all the frequencies

The calibration that relates the output voltage from the PD to the output voltage from the StochMon is then obtained as:

V_pd(f) = sqrt(2*R*P0)/h_f(f) * 10^( (Vo-q)/(20*alpha) )

where R=50ohm, P0=1mW and q=0.772 V, the latest being the offset in the calibration of the power detector (that is its output for a 0 dBm input).
  1125   Mon Nov 10 11:06:09 2008 robHowToIOOmode cleaner locked

I found the mode cleaner unlocked, with (at least) MC1 badly mis-aligned. After checking the coil alignment biases and finding everything there looking copasetic, I checked the trends of SUS{PIT,YAW,POS} and found that both MC1 and MC3 took a step this morning. The problem turned out to be loosed/jiggled cables at the satellite amplifiers for these suspensions. Giving them a good hard push to seat them restored the alignment and the mode cleaner locked right up.
  1143   Tue Nov 18 13:28:08 2008 CarynDAQIOOnew channel for MC drum modes
Alberto has added a channel for the Mode Cleaner drum modes.
C1:IOO-MC_DRUM1
sample rate-2048
chnum-13648
  1144   Tue Nov 18 19:37:23 2008 YoichiUpdateIOOMC1 OSEM signals sign flipped and c1susvme1 restart problem
Around 2PM, MC1 started to swing crazily.
The damping feedback was not working and it was actually exciting the mirror wildly.
It turned out that the sign of the UR and UL OSEM signals flipped at that time.
Restarting c1sosvme fixed the problem.

While I was looking for the cause of the problem, c1susvme1 and c1susvme2 failed several times.
I don't know if it is related to this problem.
Now it is not trivial to restart c1susvme1. It fails to restart if you just power cycle it.
Alberto and I had to connect an LCD and a keyboard to it to see what was going on. After pushing the reset button on the front panel,
I had to press Ctrl+x. Otherwise, the state LED of c1susvme1 stays red and nothing happens.
After Ctrl+x, the boot screen came up but the boot sequence failed and an error message something the following was shown:
"PXE Boot failed, check the cable"
So I swapped the network cable with c1susvme2, which was already up and running.
This time, c1susvme1 started fine and surprisingly, c1susvme2 stayed alive.
Currently, both c1susvme1 and c1susvme2 are up and running with the LAN cables swapped.
We have to check the LAN cables.
  1148   Wed Nov 19 18:12:35 2008 ranaConfigurationIOOnew channel for MC drum modes
I set up the lockin to take the MC Demod Board's Qmon signal, demodulate it at 27.5 kHz, and
put the output into a DAQ channel (I think its either MC_DRUM1 or MC1_TEMPS). However,
the MC_DRUM channel doesn't look like its getting anything in the DTT although it looked fine
on a scope. I used the 'sensitivity' setting of the lockin to make the demodulated signal
large enough but not so large that it would saturate the ADC (+/- 2V).
  1158   Sat Nov 22 10:55:51 2008 CarynConfigurationIOODrum modes Lock-In settings changed
I unhooked the MC Demod Board's Qmon signal from the Lock-In. Set the demodulation frequency to 31.11Hz with 1V amplitude, and
put the output into MC_DRUM1. DTT showed a ~30Hz peak. Dataviewer showed signal with amplitude ~20,000.
Otherwise the settings were as Rana had them: Time Constant-100us,24dB/Sensitivity-200us/Low Noise
Want to check if Lock-In frequency drifts.
  1176   Thu Dec 4 17:42:23 2008 carynUpdateIOOdrum modes observable without excitation
So, the mode cleaner was evidently aligned better and now the drum modes are observable using DTT.
The Lock-In was set to 27.8kHz and the drum mode frequencies were previously observed to be 28.039kHz(MC2), 28.222kHz(MC3) and 28.221kHz(MC1). So, we might expect peaks at ~239Hz,421Hz,422Hz.
Peaks have been observed around the expected frequencies in channel IOO-MC-DRUM1.
Note that it is possible to resolve the separate MC1 and MC3 peaks which are so close together.
(sorry these are pdf's and not png's)
  1179   Fri Dec 5 09:29:59 2008 ranaUpdateIOOdrum modes observable without excitation
Not sure what the y-scale is since there aren't any y axis labels in the plot, but it seems like we
now get an SNR of a ~few with a BW of 0.1 Hz. IN principle, the frequency noise out of the PSL ought
to be limited by the VCO phase noise at these frequencies (sort of) so the broadband MC_F level
is very roughly equal to 20-100 mHz/rHz.

Since dnu = dL*(c/lambda)/L_MC, the thermal peaks have a height of ~10^-15 m_RMS. We (Caryn) should check
that these numbers are true and then see if this is the correct amount of energy for thermally excited
mirror modes.
  1180   Fri Dec 5 14:13:41 2008 ranaSummaryIOOMC trend for the last 4 days
The MC has stayed locked for ~3 days! I just broke it to reset the MZ.
  1182   Fri Dec 5 21:31:11 2008 YoichiUpdateIOOdrum modes observable without excitation
The calibration of the MC_F feedback is posted in elog:1032.
I'm not sure where Caryn took MC signal, but if you take the signal from the servo out BNC on the MC board, it
directly corresponds to the voltage sent to the FSS VCO.
The DC calibration of the VCO is 1.75MHz/V. Since the AOM is the double-pass, the PSL frequency
change is 3.5MHz/V. At frequencies above 40Hz, the VCO calibration drops by a factor of 39/1000,
because of the pole/zero at 1.6Hz/40Hz in the VCO box.
So at the frequencies of interest (around 30kHz), the servo out voltage can be converted to the PSL frequency
change by 0.137MHz/V.
Since 30kHz is still within the bandwidth of the MC servo, the feedback signal should correspond to the actual
length change of the MC. So the above calibration factor can be used to calibrate Caryn's measurement and check
what Rana suggested.
  1196   Fri Dec 19 14:35:58 2008 Yoichi AlbertoUpdateIOOMC WFS and IOO-POS QPD re-centering
For the past two days, the MC alignment has kept drifting.
This morning, the MC alignment was so bad that it wouldn't lock to the TEM00 mode.
We aligned the MC mirrors manually until the reflection looks like a nice bull's-eye (the WFSs were off at this moment).
Then we un-locked the MC and centered the beams on the WFS QPDs.
Since the QPDs were saturated with the full laser power falling on them, I reduced the PSL power by turning the HWP after the MOPA.
After this, we turned on the WFSs and everything looks normal now.
We will see the trend of the MC related channels to monitor the drift.

Although unlikely, it might be caused by the drift of the input beam to the MC.
We found that the IOO-POS QPD was mis-centered and saturating.
We replaced the BS picking up the beam for the QPD from 33% reflection to 10% one. The QPD was still saturated.
So we put the 33% BS in the beam path to the QPD to further reduce the power. The beam kicked by the 33% BS
is dumped to a black aluminum plate. We should use a better beam dump later.
Now the IOO-POS QPD should tell us some information about the beam pointing of the PSL, though it has no sensitivity
to the relative motion of the PSL table to the vacuum chambers.
  1229   Thu Jan 15 09:19:32 2009 steveUpdateIOOMC locking
MC2 sus damping was found tripped at the morning the second time this week.

Damping was restored, ISS gain lowered to avoid saturation, MZ manually locked
and MC locking was back.
  1236   Fri Jan 16 18:45:20 2009 YoichiConfigurationIOOMC_L gain increased by a factor of 2
Rana, Yoichi

Since we fixed the FSS AOM double-pass, which used to be a single-pass, the MC_L gain was too low for
making the cross-over at 100Hz.
Rana increased it by a factor of two. Now it seems that the cross over is ok (attachment 1).

We also noticed that the MC_F spectrum is noisier than before (attachment 2).
The reference is from 6/24/2008.
  1300   Fri Feb 13 08:38:03 2009 steveUpdateIOOMC2 damping restored
  1312   Mon Feb 16 20:47:48 2009 ranaConfigurationIOOMode Cleaner WFS Loop Gain change
I found the MCWFS gain slider down at 0.012. In this state the UGFs are probably around 10-30 mHz
and so there is no reduction of seismic noise. It is mainly a DC alignment tool in this state.

We often have reduced the loop gain thusly, to prevent the dreaded "MCWFS eating CM loop gain" disease.
That disease is where there are CM loop instabilities at ~5-30 Hz because of loop cross-couplings
who's exact nature has never been understood (TBI).

Today, I implemented a 4th order, 7 Hz low pass (RLP7) into the loops and turned up the gain by a factor
of 30 to 0.3. In this state, the damping time constants seem to be ~0.5-2 seconds as shown in the first
PDF. I didn't have enough patience to do the interminable swept sine measurements down to 0.1 Hz.

The second PDF shows the Bode plot of the RLP7 filter compared to the pre-existing but unused ELP10.

The third PDF shows my estimate of the OLG TF. This is made by just putting a "Pendulum" filter into the
MCWFS bank and then plotting all the filters together using FOTON. The BLUE curve shows the old TF but
with the new high gain and the RED curve shows the new TF with the new gain.

With this new filter, I bet that we can get away with the higher WFS gain, but if there's any problem during the
handoff, the gain should be reverted to the low value.


In the 4th PDF file, I plot the spectra of 4 of MC2's control signals so that you can see what is bigger than what.
ASCPIT is the one that has the feedback from the WFS's in it. These are all just in units of counts and so to compare
them in some sort of displacement units you have to take into account the pitch moment of inertia, the mirror mass,
and the mis-centering of the beam from the center of rotation of MC2...
  1313   Mon Feb 16 21:49:06 2009 Kakeru, RanaUpdateIOOWFS

We centerd the input of WFS QPD.

  1322   Wed Feb 18 21:10:21 2009 ranaUpdateIOOMC Drumhead mode lost again
In early December, Caryn and I noticed that the MC Drumhead mode was visible at the Qmon point of
the MC demod board using a spectrum analyzer and no external excitation of the MC mirrors. We then
started tracking the MC Drumhead modes.

Today I found that it is gone again. It also wasn't there when I looked for it in 2007. Mad

I looked at the MC error point spectrum and it seemed reasonable. Changing the gains in the MZ, ISS, PMC, & FSS
had no good effect on the noise spectrum.

The voltage noise above 10 kHz in the MC error point is increasing like ~f. I think that this means that
the leftover is the noise from the FSS. Below 10 kHz it is the noise of the VCO (10 mHz/rHz).

One possibility is that the high frequency noise changes with the mood of the NPRO. There should be no
frequency noise induced by the decay of the PA diode power. We can do an NPRO SLOW scan to see if there
is some kind of mode hop noise happening.
  1358   Thu Mar 5 00:06:32 2009 Kakeru, RanaUpdateIOOWFS centering
We found that the MC REFL image was no longer round and that the MCWFS DC quadrant spots were mostly
in one quadrant. So we re-centered the MCWFS beams in the following way:

1) We unlocked the MZ and adjusted the PZT voltage to keep the beam on the WFS from saturating.
2) Re-aligned the black hole beam dump to center its beam in its aperture.
3) centered the beam on the MCWFS optics and MCWFS QPD displays.
4) Relocked MC.

Below is the image of the IOO Strip tool. You can see that the MC REFL DC is now more flat. The
MC pointing has also been changed (see the MC TRANS HOR & VERT channels). The MC transmitted
light is also now more stable and higher.

We tried to center the QPD, and we found that there were a few hundred mV of dark offset for each 
quadrant of QPD. We adjusted them with this scripts:
/cvs/cds/caltech/scripts/MC/WFS/McWFS_dc_offsets
  1363   Fri Mar 6 01:04:49 2009 Kiwamu IZUMIConfigurationIOO!! lock-in amp disconnected !!

The power supply of a lock-in amp, which is on the Y-arm side of PSL clean room, was pulled out by my mistake.

Then I reconnected it, but I don't know whether it is re-adjusted properly.

I'm sorry about this. If you are using that amp, it should be checked.

  1383   Wed Mar 11 01:16:40 2009 ranaSummaryIOOrogue trianglewave in the MC Servo offset slider

On Monday evening, I ran this command: trianglewave C1:IOO-MC_REFL_OFFSET 0 4 120 600;ezcawrite C1:IOO-MC_REFL_OFFSET 1.76

which I thought (from the syntax help) would move that offset slider with a period of 120 seconds for 600 seconds. In actuality, the last argument is the

run time in number of periods. So the offset slider has been changing by 8 Vpp for most of the last day. Oops. The attached image shows what effect

this had in the MC transmitted power (not negligible). This would also make the locking pretty difficult.

 

In the second plot you can see the zoom in view for ~30 minutes. During the first part, the MCWFS are on and there are large fluctuations

in the transmitted power as the WFS offset changes. This implies that the large TEM00 carrier offset we induce with the slider couples into

the WFS signals because of imbalances in the quadrant gains - we need someone to balance the RF gains in the WFS quadrants by injecting

an AM laser signal and adjusting the digital gains.

 

Since there is still a modulation of the MC RFPD DC with the WFS on, we can use this to optimize the REFL OFFSET slider. The third plot

shows a 8 minute second trend of this. Looks like the slider offset of zero would be pretty good.

  1386   Wed Mar 11 14:51:01 2009 Kakeru, Joe, RobUpdateIOOMC alignment

This morning, MC alignment was gone and MC wasn't lock.

We checked old value of pitch, yaw, and position offset of each MC mirror, and found they were jumped.

We don't know the reason of this jump, but we restore each offset value and MC backed to lock.

  1389   Wed Mar 11 21:03:51 2009 Kakeru and KiwamuUpdateIOOPSL angle QPD

Kakeru and Kiwamu

We placed a QPD on the PSL bench for PSL angle monitor.

 

Quote:

I checked a broken QPD, which was placed for PSL angle monitor, and finally I cocluded one segment of the quadrant diode was broken.

The broken segment has a offset voltage of -0.7V after 1st I-V amplifier. It means the diode segment has a current offset without any injection of light.

Tomorrow I will check a new QPD for replacement.

Kiwamu IZUMI

 

 As we mentioned before, old QPD which used to be placed is broken.

 And we put broken QPD into the "photodiodes" box under the soldering table.

 

 

  1391   Wed Mar 11 23:41:33 2009 Kakeru, YoichiUpdateIOOWFS centering

We found the MC reflection was distorted . And WFC beam went to upward of QPD

We recentered WFC beam and these problems were fixed

  1394   Thu Mar 12 15:57:53 2009 YoichiUpdateIOOMC drift is terrible
Yoichi, Osamu,

Last night's locking work was totally interrupted by the sabotage by the MC.

First, after I measured the RF_AM, the MC alignment was somehow shifted largely and the MC did not lock to TEM00 mode.
I only mis-aligned MC2 to measure the RF_AM, but the MC reflection beam was also shifted (looking at the WFS QPD), that means MC1 was mis-aligned somehow.
Moreover, even when the MC is not locked, i.e. no feedback to the mirrors, the OSEM values of the MC mirrors (all of them) drift a lot in 10min scale.
I was totally puzzled. So I rebooted c1iovme and c1sosvme. Then this strange drift of the OSEM values stopped.
Even though, the MC tended to lose lock within ten minutes because the WFS QPDs were not centered.
We did several iterations of re-centering and finally the MC started to stay locked happily. The MC reflection beam was symmetric.

Then this morning when I came in (to be honest, afternoon), the MC reflection looked asymmetric again. The WFS QPDs were mis-centered again.
The attached files show an 8-hour trend of various MC related signals.
There was a half-degree temperature change starting from around 11AM. Corresponding to that, the IOO-QPD signals drifted indicating that the PSL beam pointing
was shifted. The MZ PZT signal shows a similar trend, so the beam pointing may have been shifted by the MZ (not sure).
The MC WFS, transmission QPD signals show the same trend.
This is too bad.

Right now, the PSL beam pointing is monitored by the QPDs detecting the transmitted beam through the first mirror of the periscope.
This means even if we can track the beam pointing drift with the QPDs, we can't correct the beam pointing using the periscope mirrors.
I don't want to touch the MZ mirrors for this purpose.
I propose to put a pick-off mirror after the second mirror of the periscope to send light to the IOO-QPDs. This way, we can use the periscope
mirrors to restore the beam pointing screwed up by the MZ.
  1396   Thu Mar 12 18:48:37 2009 YoichiUpdateIOOMC aligned but ...
After the MZ alignment, I aligned the MC with the periscope mirrors.
It looked like the MC mis-alignment was mainly caused by the input beam change.
So I left the MC mirrors as they were to keep the output beam pointing.
However, after I finished the alignment, the MC output beam was too low on the Faraday.
Also the X-arm did not lock to TEM00 mode. So the MC mirrors must have also shifted to a weird alignment state.
I should have restored the MC mirror alignment to a good state using the OSEM DC signals.

Rana came in and restored the MC mirror alignment using the SUS drift mon.
He and Kakeru is now working on the periscope to align the beam into the MC.
  1397   Thu Mar 12 19:11:27 2009 ranaUpdateIOOMC drift is terrible
Kakeru, Rana, Yoichi

We used the SUS DRIFT MON screen to set the MC biases such that the mirrors were returned to the old OSEM values.
To do this, we set the nominals and tolerances using the appropriate scripts in the mDV/extra/C1/ directory.

We then used the MC_ALIGN screen to set the angle bias sliders.

Then Kakeru and I went to the PSL table to the periscope magic and maximize the MC transmission. Kakeru seems to
have the careful Japanese alignment touch and I am hungry, so I am leaving him to optimize the power. After he
finishes he is going to align the beam to the WFS and turn the MC autolocker back on. The x-arm is locked on a
TEM00 mode so the MC alignment is maybe OK.
  1398   Thu Mar 12 20:59:04 2009 KakeruUpdateIOOMC drift is terrible
After Rana went for his dinner, I aligned periscope to make the MC output 3.2 (Attachment 1).

After that, to align WFS, I unlocked the MC, unlocked the MZ and decrease the beam power to WFS QPD, and re-centerd WFC beam.
I restored MZ and MC lock.
I enabled MC autolocker, and change C1:IOO-WFS_Gain_Slider from 0 to 0.02 to lock WFS.


Quote:
Kakeru, Rana, Yoichi

We used the SUS DRIFT MON screen to set the MC biases such that the mirrors were returned to the old OSEM values.
To do this, we set the nominals and tolerances using the appropriate scripts in the mDV/extra/C1/ directory.

We then used the MC_ALIGN screen to set the angle bias sliders.

Then Kakeru and I went to the PSL table to the periscope magic and maximize the MC transmission. Kakeru seems to
have the careful Japanese alignment touch and I am hungry, so I am leaving him to optimize the power. After he
finishes he is going to align the beam to the WFS and turn the MC autolocker back on. The x-arm is locked on a
TEM00 mode so the MC alignment is maybe OK.
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