The present plan to go with clear cast acrylic plexiglass 1" thick side wall  and  two  clear  1/2 thick top cover.

The inside would be lined with light braun YAG safety window sheets 0.14"  VLT ~25%  OD 4 @ 532nm & OD 5 @ 1064nm

On Tue, Dec 20, 2011 at 11:37 PM, Rana Adhikari wrote:
Steve,

We are thinking of replacing a few metal parts in the suspension with sapphire/ruby. We want to replace the standoff (which is Al) with sapphire and also the top plate where the wire is clamped.

For the top, we should make a cutout for a little plate in the existing crossbar. In the cutout would go a little mounting plate. Then the clamping plate (which is now steel) we would also replace with a Sapphire one.

I don't think it matters whether its sapphire or ruby, just has to be very hard.

Can you please get some quotes on the parts?

rana

[John / Valera / Kiwamu]

 We installed a new weapon, an optical spectrum analyzer in the AS port.

Like we used to do in the old days, two BNC cables were newly laid down and they bring the output of the OSA to the control room to monitor the spectrum with an oscilloscope.

(Some notes)

The photo diode of the OSA was replaced by a Thorlab PDA100A to amplify the signals.

The carrier peak is at about 6.9 V and the f1 and f2 sidebands peaks are at about 40 mV when the beam is in straight shot (everything is misaligned except ITMY and BS).

According to a rough calculation, those numbers correspond to a modulation depth of about 0.16 or so.

The depth agree with what Mirko measured before (#5519)

I finished mounting the new projector. The projector and computer monitor now display information.

 This may or may not be general knowledge already, but Jamie and I added a HowTo explaining how to retrieve channel data from the frame builder via NDS, but off site on one's own computer.  See the Wiki page:

https://wiki-40m.ligo.caltech.edu/How_To/NDS

[John / Kiwamu]

 We tried to figure out what is causing spikes in the REFL33 signal, which is used to lock PRCL.

No useful information was obtained tonight and it is still under investigation.

(Background)

 One thing preventing us from doing smooth measurements of the noise budget and the sensing matrix is some sharp spikes in the LSC error signals.

For example when we lock PRMI with REFL33 and AS55 fedback to PRCL and MICH respectively, both the REFL33 and AS55 signals show some spikes in time series.

Those spikes then bring the noise spectra higher than how they should be.

So for the reason, taking the noise budget doesn't give us much information about the interferometer rather than there are spikes.

Also the sensing matrix measurement has been suffered from those spikes, which excite the impulse responses of the low pass filters in the LOCKIN detection systems a lot.

(What we did)

 We looked into the actual analog signals to see if there are indeed spikes or not before they are acquired to the ADCs.

But we didn't find any corresponding spikes in the signals that are after the mixers.

It maybe because the signals we looked into didn't have high enough SNR because they were coming out from the monitor lemo outputs on the demod boards.

 Then we thought the spikes are from the whitening circuits, due to some kind of saturation.

We decreased the gain of the whitening filters by a factor of 10, but it didn't help and the spikes were still there.

[John / Kiwamu]

 We found that some of the suspensions channels (for example C1:SUS-BS_POS_IN1 and etc) were not accessible from dataviewer for some reasons.

So far it seems none of the channels associated with c1sus are accessible from dataviewer.

No we can't do that because the c1scx model is not working properly.

If you look into the real time controller screen you will find what I mean.

ETMX sus damping restored

 You (Jamie) should talk with Rolf and Alex to find out what framebuilder they will support for > 3 years. Then we should buy that along with the adapter card which allows us to use the same RAID we now have for the frames.

I mounted the new projector to the pipe where the old projector was attached. The mounting hardware wasn't designed for attaching to a pipe, but with Steve's help I mounted the projector. The projector is angled away from the area of the wall designated as the screen, and I am going to meet with Steve Monday to fix this.

The framebuilder is back online now, minus it's symmetricom GPS card.  The card seems to have failed entirely, and was not able to be made to work at downs either.  It has been entirely removed from fb.

As a fall back, the system has been made to work off of the system NTP-based time synchronization.  The latest symmetricom driver, which is part of the RCG 2.4 branch, will fall back to using local time if the GPS synchronization fails.  The new driver was compiled from our local checkout of the 2.4 source in the new to-be-used-in-the-future rtscore directory:

controls@fb ~ 0$ diff {/opt/rtcds/rtscore/branches/branch-2.4/src/drv/symmetricom,/lib/modules/2.6.34.1/kernel/drivers/symmetricom}/symmetricom.ko
controls@fb ~ 0$ 

The driver was reloaded.   daqd was also linked against the last running stable version and restarted:

controls@fb ~ 0$ ls -al $(readlink -f /opt/rtcds/caltech/c1/target/fb/daqd)
-rwxr-xr-x 1 controls controls 6592694 Dec 15 21:09 /opt/rtcds/caltech/c1/target/fb/daqd.20120104
controls@fb ~ 0$ 

We'll have to keep an eye on the system, to see that it continues to record data properly, and that the fb and the front-ends remain in sync.

The question now is what do we do moving forward.  CDS is not supporting the symmetricom cards anymore, and have moved to using Spectracom GPS/IRIG-B cards.  However, Downs has neither at the moment.  Even if we get a new Spectracom card, it might not work in this older Sun hardware, in which case we might need to consider upgrading the framebuilder to a new machine (one supported by CDS).

Alex and I have taken the framebuilder offline to try to see what's wrong with the symmetricom card.  We have removed the card from the chassis and Alex has taken it back to downs to do some more debugging.

We have been formulating some alternate methods to get timing to the fb in case we can't end up getting the card working.

Both the c1scx and its IOP realtime processes became out of sync.

Initially I found that the c1scx didn't show any ADC signals, though the sync sign was green.

Then I software-rebooted the c1iscex machine and then it became out of sync.

For tonight this is fine because I am concentrating on the central part anyway.

After running into more problems with the upgrade, I eventually decided to abort todays upgrade attempt, and revert back to where we were this morning (RTS 2.1).  I'll try to follow this with a fuller report explaining what problems I encountered when attempting the upgrade.

However, when Alex and I were trying to figure out what was going wrong in the upgrade, it appears that the fb symmetricom card lost the ability to sync with the GPS receiver.  When the symmeticom module is loaded, dmesg shows the following:

[  285.591880] Symmetricom GPS card on bus 6; device 0
[  285.591887] PIC BASE 2 address = fc1ff800
[  285.591924] Remapped 0x17e2800
[  285.591932] Current time 947125171s 94264us 800ns 
[  285.591940] Current time 947125171s 94272us 600ns 
[  285.591947] Current time 947125171s 94280us 200ns 
[  285.591955] Current time 947125171s 94287us 700ns 
[  285.591963] Current time 947125171s 94295us 800ns 
[  285.591970] Current time 947125171s 94303us 300ns 
[  285.591978] Current time 947125171s 94310us 800ns 
[  285.591985] Current time 947125171s 94318us 300ns 
[  285.591993] Current time 947125171s 94325us 800ns 
[  285.592001] Current time 947125171s 94333us 900ns 
[  285.592005] Flywheeling, unlocked...

Because of this, the daqd doesn't get the proper timing signal, and consequently is out of sync with the timing from the models.

It's completely unclear what caused this to happen.  The card seemed to be working all day today, then Alex and I were trying to debug some other(maybe?) timing issues and the symmetricom card all of a sudden stopped syncing to the GPS.  We tried rebooting the frame builder and even tried pulling all the power to the machine, but it never came back up.  We checked the GPS signal itself and to the extend that we know what that signal is supposed to look like it looked ok.

I speculate that this is also the cause of the problems were were seeing earlier in the week.  Maybe the symmetricom card has just been acting flaky, and something we did pushed it over the edge.

Anyway, we will try to replace it tomorrow, but Alex is skeptical that we have a replacement of this same card.  There may be a newer Spectracom card we can use, but there may be problems using it on the old sun hardware that the fb is currently running on.  We'll see.

In the mean time, the daqd is running rogue, off of it's own timing.  Surprisingly all of the models are currently showing 0x0 status, which means no problems.  It doesn't seem to be recording any data, though.  Hopefully we'll get it all sorted out tomorrow.

RTS/RCG/DAQ UPGRADE TO COMMENCE

I will be attempting (again) to upgrade the RTS, including the RCG and the daqd, to version 2.4 today.  The RTS will be offline until further notice.

Dataviewer is recovered after heavy new year party.

Communication between the front end models and the framebuilder has been restored.  I'm not sure exactly what the issue was, but rebuilding the framebuilder daqd executable and restarting seems to have fixed the issue.

I suspect that the problem might have had to do with how I left things after the last attempt to upgrade to RCG 2.4.  Maybe the daqd that was running was linked against some library that I accidentally moved after starting the daqd process.  It would have kept running fine as was, but if the process died and was attempted to be started again, it's broken linking might have kept it from running correctly.  I don't have any other explanation.

It turns out this was not (best I can tell) related to the new year time sync issues that wer seen at the sites.

The dynamic power normalization system has been modified such that the normalization happen after the LSC input matrix.

Remember that we don't use /cvs/cds/rtcds anymore.  Everything should be in /opt/rtcds now.

For systems using the Spectracom IRIG-B cards for timing information, the code did not properly roll over the time for
2012 (still thinks it is 2011 and get reports from DAQ of timing errors (0x4000)). I have made a temporary fix for this
in the controller.c code in branch-2.3, branch-2.4 and release 2.3.1. 

 The problem is the same as yesterday.

       Locking plan            

Here is a plan in my mind and these are basically the details of the gantt chart (#6143):

• (1 day task) Measurement of the recycling gains of the RF sidebands with the PRMI and DRMI configuration, using POP22/110 RFPD.
  • I need to have confidence that I am really locking the DRMI with SRC resonating to 55 MHz.
  • Also those values will enable us to estimate losses and mode matching again (maybe ?).
• (3-4 days task) Measurement of the sensing matrix using the multiple-LOCKIN system.
  • Write a script to automatically measure the sensing matrix. This must be easy.
    • The results will enable us to diagonalize the input matrix and therefore it eventually gives more solid lock of the DRMI
    • Also it will give us the optical gains of 3f signals. So this is actually a step toward the 3f signal check.
• (3-4 days task) Noise budgeting on the 3f signals
  • This is a very important part of the DRMI characterization because the results will tell us whether we can hold the DRMI lock with a sufficient SNR or not.
  • If it turns out that they don't have good SNRs, we then have to come up with some ideas to improve the SNRs.
• (Extra fun task depending on schedule) 3f DRMI lock + Y arm ALS
  • If the beat-box electronics are not available by the time when the work above are completed, I will do this fun task.
  • Probably it is better to start preparing the common mode servo electronics because it will be needed anyway.

 Time to lower your expectations!

Do we really need 40 microns at 500 Hz? Or perhaps should there be a frequency dependent displacement requirement?

I don't know what exactly is going on, but MC became flaky and it's been frequently unlocked.

I have turned off the MC WFS servo to check if the WFSs are doing something bad. But it still tends to be unlocked without the WFS servo.

Right now it doesn't stay locked for more than 10 min.

 I checked on the two single-axis shakers that are present at the 40m that Steve pointed out:

• Brüel & Kjær type 4809, rated for 45 N peak, and
• Brüel & Kjær type 4810, rated for 10 N peak.

Neither of these meet the force requirement of 2.04 kN peak.

 I moved the following old and obsolete MEDM directories to an archive /cvs/cds/rtcds/caltech/c1/medm

• c1vga
• c1vgl
• c1gpt
• c1gpv
• c1nio
• c1spy
• c1spx

None of these models were present in /cvs/cds/rtcds/caltech/c1/target

I updated the design requirements for the Stewart platform.  I weighed the unloaded "dirty" SOS that was sitting on the workbench in the control room; its mass is 11 kg.  Steve suggested that the OSEMs (not installed on this model) would add another 0.5 kg.  From the specs in the final SOS design document, LIGO-T970135, I added 0.25 kg for the optic itself; I am therefore taking the total payload mass to be 11.75 kg.  (Now, the upper stage of the Stewart platform itself will likely add a nontrivial amount, but I am not worrying about this yet.)

I have e-mailed Janeen Romie to obtain the actual center of mass and principal moments of inertia of the platform.  I also cooked up a simple scheme to measure both quantities, should this information not be available.  It would involve rigidly mounting the dirty SOS to a rigid bar hung from a pivot.  By translating the mount point in two dimensions and measuring the period of the pendulum, I ought to be able to find the center of mass and moments of inertia by multilinear regression.  However, this elaborate scheme is not necessary to just compute some ballpark figures; it could wait until a later stage in the design.  For the time being, I just rescaled the moment of inertia proportional to the increase in mass, such that the torque-to-force ratio is unchanged.

As such, the design requirements are now 

• linear travel: 40 microns peak to peak (based on SOS design requirements in LIGO-T950011)
• angular travel: 3 mrad peak to peak (based on SOS design requirements in LIGO-T950011)
• payload mass: 11.75 kg (measured unloaded mass, plus educated guesses about combined mass of OSEMs and optic)
• payload moment of inertia: 0.0232 kg m^2 (wild guess)
• bandwidth: 500 Hz (suggestion of Rana and Koji: ~kHz)

From these assumptions, the revised actuator requirements and dimensions are:

• peak actuator force: 2.04 kN
• minimum radius of top platform: 15 cm
• minimum radius of bottom platform: 30 cm
• minimum height: 26 cm

See the attached PDF document.

It appears that the actuator that I had originally nominated, PI's model P-225.80, would very nearly meet the actuator force requirement.  Steve also pointed out the following single-axis shakers that are already in use in the 40m:

• Brüel & Kjær type 4809
• Brüel & Kjær type 4810

I want to find out if either of these would meet the present need, but I'm waiting on a response from the manufacturer to get access to the data sheets.

I found the PSL laser has been off for four hours. Nobody seemed to know why.

I just turned it on and it is now providing about 10% lower power compared with one before the shutdown.
Let's keep the eyes on the power if it can recover as the housing gets warm.

Apparently there is a bug in the timing cards having to do with the new year roll-over that is causing front-end problems.  From Rolf:

For systems using the Spectracom IRIG-B cards for timing information, the code did not properly roll over the time for
2012 (still thinks it is 2011 and get reports from DAQ of timing errors (0x4000)). I have made a temporary fix for this
in the controller.c code in branch-2.3, branch-2.4 and release 2.3.1. 

I was going to check to see if the 40m is suffering from this. I'll be over to see if that's the problem.

It turned out that the power normalization need a modification.

I will work on it tomorrow and it will take approximately 2 hours to finish the modification.

     Concept of Power Normalization         

1.  Static power normalization, which should be placed before the input matrix.
2.  Dynamic power normalization, which should be placed after the input matrix.

Is there a reason the framebuilder status light is red for all the front ends?

Also, I reenabled PRM watchdog.

Now a power normalization is doable for the LSC error signals.

It is working fine, but at some point we may want to have some kind of a saturation filter or limiter to avoid dividing a signal by a small number.

 (How to set the normalization)

•   Click a small matrix panel on the LSC OVERVIEW window (shown in the attached screen shot below).
  •     This will give you a pop-up-window, which shows a matrix to route the normalization signals

•   Choose a numerator channel, which you want to divide, and choose denominator channels, which you want to use as a power normalization factor.
•   Put some number in the corresponding matrix elements.
•   Once you put a non-zero element in the matrix, the corresponding numerator channel will be divided by the specified denominator channels.
  •     Otherwise the static normalization factors (e.g. C1:LSC-AS55_POW_NORM, etc.,) will be used for the denominator.

The high frequency noise, which has been a dominant noise above 30 Hz in the Y arm ALS (#6133), decreased by a factor of 5.

This reduction was done by increasing the modulation depth at the Y end PDH locking. Now the noise floor at 100 Hz went to 0.2 pm/sqrtHz.

However the noise source is not yet identified and hence it needs a further investigation.

 (Increasing the modulation depth)

I added an ALS feedback path on the MC2 suspension and this path will enable us to stabilise the MC length using the ALS scheme.

I have realigned the steering mirrors for PMC because the transmitted light had been at ~ 0.741

After the alignment it went back to ~ 0.850.

Some new screens have been made for the new multiple-LOCKIN system running on the LSC realtime controller.

The medm screens are not so pretty because I didn't spend so long time for it, but it is fine for doing some actual measurements with those new screens.

So the basic works for installing the multiple-LOCKIN are done.

 The attached figure is a screen shot of the LOCKIN overview window.

As usual most of the components shown in the screen are clickable and one can go to deeper levels by clicking them. 

      An example              

      How to set the thresholds         

1. Open the trigger matrix window, which is accessible from the C1LSC overview screen as usual.
2. Then type the desired upper and lower thresholds into the column.

The below is a screenshot of the trigger matrix screen. The thresholds column is pointed by a big white arrow.

 

Of course, DO NOT set the upper threshold value to be smaller than that of the lower threshold. Otherwise it won't correctly work.

Also if you want to have the usual trigger rather than the Schmitt trigger, simply put the upper and lower thresholds at the same values.

      Details         

(Some details)

The picture below is a screen shot of the LSC real time model, zoomed in the new LOCKIN part.

The LOCKIN module consists of three big components:

1. A Master oscillator
   • This shakes a desired DOF through the LSC output matrix and provides each demodulator with sine and cosine local oscillator signals.
   • This part is shown in the upper side of the screen shot.
   • The sine and cosine local oscillator signals appear as red and blue tags respectively in the screen shot.
2. An input matrix
   • To allow us to select the signals that we want to demodulate.
   • This is shown in the left hand side of the screen shot.
3. Demodulators
   • These demodulators demodulate the LSC sensor signals by the sine and cosine signals provided from the master oscillator.
   • With the input matrix fully diagonalized, one can demodulate all the LSC signals at once.
   • The number of demodulators is 27, which corresponds to that of available LSC error signals (e.g. AS55_I, AS55_Q, and etc.).
   • This part is shown in the middle of the screen shot.

I have edited c1scx.ini by hand in order to acquire some green locking related channels.

Somehow c1sus.ini, c1mcs.ini, c1scx.ini and c1scy.ini are not accessible via the daqconfig script.

As far as I remember it had been accessible via daqconfig a week ago when I edited c1scy.ini.

Anyway I had to edit it by hand. They need to be fixed at some point

Often people say "I don't use conlog because its real slow". Its a little like not driving because your car has no gas.

I looked into what's going on with conlog. No one has fixed its channel list in ~1 year so it didn't make much sense. Also since Oct 1 of this year, it expired the leap seconds epoch and has been waiting for someone to look at the log file and update the list of leap seconds.

Some issues:

• Don't use the phrases like OUTPUT, OUTMON, OUT16, or INMON as the usual part of a channel name. These are filter modules words which use to exclude channels from conlog. Please fix ALL of the LOCKIN screens to get rid of the OUTPUT filter banks.
• If you use an EPICS channel in a servo so that its getting changed 16 times a second, make sure to add it to the conlog exclude list.

There are a bunch of bad channels which are screwing up various tools (DV, DTT, etc.):

Examples: C1:LSC-Subsystem_NPRO_SW1, C1:-DOF2PD_MTRX_0_0_SW1, C1:BAD-BAR_CRAZY_2_RSET, C1:C1L-DOF2PD_MTRX_3_14_SW2, C1:DUB-SEIS_GUR2_Z_LIMIT, etc.

• There are a bunch of old, unused directories in c1/medm/. EVERYONE take a look in there and delete the OLD dead ones so that we don't keep recording those channels.

 To fix up some of these issues, I have deleted several MEDM directories which I thought were old (there are several extras left from Aidan's Green time). I also have put a bunch of exclude variables into the conlog 'scan_adls' script to prevent it from adding some of the new worthless channels. Finally, I have started this command

../bin/strip_out_channels '.*STAT.*','.*_ALIVE.*','C1:PEM.*','.*_Name.*','C1:UCT.*','C1:MCP.*','C1:SP.*','C1:DU.*','C1:RF.*','C1:NIO.*','C1:TST.*','C1:SUP.*','C1:X.*','C1:FEC.*','.*_LFSERVO.*','.*FSS_SLOWDC.*','C1:LSC-LA_MTRX_21','C1:LSC-PD.*OFFSET','C1:LSC-ETM.*OFFSET' conlog*.log

which should strip lots of the excess conlog data out of the conlog directory. The only downside is that its setting all of the timestamps of the .log files to today instead of the historical times but I don't think we'll care about this too much. Hopefully it will speed things up to have less than 450 GB of conlog files...

update: 12 hours later, its still running and has removed ~100 GB so far. It will probably take the rest of the weekend to finish.

After I did a fine alignment of the X green beam path on the PSL table, the X arm beat-note was also obtained.

Here is a picture of the latest setup. The blue lines represent S-polarizing green beams.

During I was working on the PSL table HEPA was at 80 %, and after the work I brought it to 20 %.

I set the limitters of the MC WFS servos not to inject the feedback more than 2000.

The residual of the WFS shakes the MC SUSs at every lock loss.

         Assumptions on the parameter estimations          

Here is the Gantt chart we discussed in the 40m meeting today.

Based on the discussions we had, I applied a little bit of corrections on the chart but the main stream remains the same.

While discussing the suspension hysteresis measurements, Koji, Kiwamu, and I realized that the suspension wire standoff is aluminum, whereas the standoff for the LIGO LOS are using quartz.

Using a soft aluminum standoff is bad. The movement of the suspension will slowly wear the groove and produce opportunities for mechanical upconversion and hysteresis.

In fact, the wire standoff as well as the clamping block on the top should be made of sapphire or ruby to prevent any such wearing issues. Steve is hot on the case.

I made the first trial of locking a Power-recycled single arm.

 This is NOT a work in the main stream,

but it gives us some prospects towards the full lock and perhaps some useful thoughts.

      Optical Configuration         

• Y arm and PRM aligned. They become a three-mirror coupled optical cavity
  • Power Recycling Cavity (PRC) is kept at anti-resonance for the carrier when the arm length is off from the resonance point
  • Hence bringing the arm length to the resonance point lets the carrier resonate in the coupled cavity
  • BS behaves as a loss term in PRC and hence results a low recycling gain
• Everything else are misaligned, including ITMX, ETMX, SRM and BS
  • Therefore there are neither Michelson, X arm nor Signal Recycling Cavity (SRC)

   Lock Acquisition Steps    

1. Misalign PRM such that there is only Y arm flashing at 1064 nm
2. Do ALS and bring the arm length to the resonance point
3. Record the beat-note frequency such that we can go back to this resonance point later
4. Displace the arm length by 13 nm, corresponding to a frequency shift of 200 kHz in the green beat note
5. Restore the alignment of PRM.
6. Lock PRC to the carrier anti-resonance condition using REFL33I. At this point the arm doesn't disturb the lock because it is off from the resonance anyway
7. Reduce the displacement in the arm and bring it back to the resonance

     Actual Time Series     

Below is a plot of the actual lock acquisition sequence in time series.

• The data starts from the time when the arm length was kept at the resonance point by the  ALS servo.
  • At this point PRM was still misaligned.
• At 120 sec, the arm length started to be displaced off from the resonance point.
• At 250 sec, the alignment of PRM was restored and the normalized DC reflection went to 1.
  • Error signals of PRC showed up in both REFL33 and POOY11
• At 260 sec, PRC was locked to the carrier anti-resonance point using the REFL33_I signal.
  • Both REFL33 and POY11 became quiet.
  • REFLDC started staying at 1, because the carrier doesn't enter to the cavities and directly goes back to the REFL port.
• At 300 sec, the arm length started to be brought to the resonance point.
• At 400 sec, the arm length got back to the resonance point.
  • The intracavity power went to 3.5 or so
  • REFLDC went down a bit because some part of the light started entering in the cavities
  • REFL33 became noisier possibly because the Y arm length error signal leaked to it.

Scripting of the single arm automated lock script is 80% done.

The remaining 20 % is not something immediately needed and I start decreasing the priority on the Y arm ALS.

(Remaining stuff)

• Automated optimization of I/Q phases at the frequency discriminator's signal.
  • this part will be done after we install Jamie's new beat box
• A routine function which checks if the beat note is within a reasonable bandwidth
  • This part can be done with the frequency-divided signal and the digital delay line frequency discriminator
  • Another approach is to install a frequency counter, which doesn't have to be so precise
• A state bit which tells us how far the script goes
• An exit handler.
  • This should run whenever the script is unexpectedly force-quite, to gently bring the ALS system down.
• A servo which brings the beat frequency to exactly a point where the infrared light is on a resonance point
  • Currently this part is partially human-aided. I put a little bit of correction in the frequency offset by looking at time series
  • To automate this part, we need another LOCKIN system to shake the arm length and demodulates the transmitted light