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ID Date Author Type Category Subject
  6258   Tue Feb 7 03:05:08 2012 ZachUpdateSUSOSEM sat amp measurements

I did some more investigation on the OSEM box today.

Troubleshooting:

After removing some capacitors and still finding that the +15V rail was at over +20V, I decided to see if the TO-3 7815 that I removed behaved properly all by itself. It did. After some more poking around, I discovered that whoever assembled the board isolated the case of the regulator from the board. It is through the case that this package gets its grounding, so I removed the mica insulator, remounted the regulator, and all worked fine.

Since I had gotten a spare from Downs, I also replaced the LT1031 (precision 10-V reference), for fear that it had been damaged by the floating voltage regulator.

 

Noise measurements:

sat_amp_measurement_setup.png

LED Driver

With the above out of the way, I was finally able to take some measurements. The first thing I did was to look at the LED drivers. I fixed the one stage that I mentioned in my last post by adding two 820-ohm resistors in parallel with the 1k, such that it was very close to all the others (which are 806 || 806 || 1k). With that, using a red LED, I measured a current of 34.5 mA (+/- 0.1) out of each of the 5 stages (UL, UR, LL, LR, S).

I then measured the current noise of each one by monitoring the voltage across the 287-ohm resistor in series with the LED. The driver works by putting the LED in the feedback path of an inverting amp. There is a 10-V input from the LT1031, and the values of the input and feedback resistors determine the current drawn through the LED. There is a buffer (LM6321) in the path to provide the necessary current.

The LISO model I made according to that description seems to make sense. I simply modeled the LED as a small resistor and asked LISO for the current through it. The transfer function shows the proper DC response of -49.15 dB(A/V) -->  34.8 mA @ 10 V, but, the estimated current noise doesn't add up with the measured levels:

LED_driver_vs_liso.png

I have to get to the bottom of this. Two possibilities are: 1) The buffer adds noise, and/or 2) I am modeling this invalidly.

PD Amp

I also began measuring the PD amplifier noise levels, though I only measured two of them for lack of time. I find it odd that there is a 100-ohm input series resistor on what I thought would be just a transimpedance amplifier. For that reason, I want to look into how the OSEMs are connected to this guy.

In any case, I measured the output noise of two of the PD amps by shorting the input side of the 100-ohm resistors to ground, and then I divided by their TF to get the input noise level. Here it is compared with the LISO estimate. I have plotted them in units of voltage noise at the input side of the resistors for lack of a way to infer the equivalent photocurrent noise level.

pd_amp_vs_liso.png

Above 2 Hz or so, the measured level agrees with the prediction. Below this, the measured noise level increases as 1/f, while it should go as the standard 1/sqrt(f) (the manufacturer-quoted 1/f corner is at 2 Hz). Another thing to get to the bottom of.

  6257   Mon Feb 6 17:06:11 2012 steveUpdateSUSoplev transferfunction of PIT: ETMY & ETMX

Kiwamu showed me how to do transferfunction of oplev pitch

Attachment 1: ETMX_PIT.png
ETMX_PIT.png
Attachment 2: ETMY_PIT.png
ETMY_PIT.png
  6256   Mon Feb 6 11:07:21 2012 steveUpdateSUSOplev QPD Sum Trends are suspicious

Quote:

The attached trend shows a problem with the QPD sums.

Why are ETMX and ITMX so much lower than ETMY and ITMY? Are the laser's dying? Or is it the gain inside the QPD? Or the reflectivity of the coatings?

Steve - please check on Monday the laser powers and the ETM/ITM reflectivity for HeNe lasers. Maybe we have to increase the transimpedance gain in the heads.

ETMX and ETMY have 0.2 mW returning to their QPDs........so the gain must lower at  ETMX

ITMX laser 1103P has only 0.67 mW output and 0.025 mW returning to the QPD.

ITMX and ETMX oplev lanching paths  have lenses without AR coating. This is my fault. I will buy them.

          ETMX   0.2 mW           900 counts

         ITMX     0.025           1300

         SRM      0.04            2600

          BS      0.05            3500

          PRM     0.06            4000

         ETMY     0.2             9000

        ITMY      0.3            14500

Attachment 1: oplevsums.png
oplevsums.png
  6255   Fri Feb 3 23:19:22 2012 ZachUpdateSUSOSEM testing begins

I took one of the spare OSEM satellite amps (schematic) from the cabinet down the Y arm this afternoon to begin testing. I spent most of the day amassing the melange of adapters and connectors I needed to talk to the relic. The most elusive was the über-rare 64-pin IDE connector, for which neither the 40m nor Downs or Bridge had a breakout (despite there being several Phoenix boxes on each electronics rack at the 40m---hmm...). The solution I came up with was to make a breakout cable myself, only there was no 64-pin ribbon. So, I carefully fed a 50-pin and most of a 16-pin ribbon side by side into one push-down connector, and that was that:

IDE64_homestyle.png

I also finally found a 25-pin D-sub breakout just after figuring out the proper pinout for a 25-to-9 adapter, which I thought I was going to have to use. OH WELL.

Science

The first thing I figured I'd do is measure the LED drivers' current noise and see how it compared with LISO. I powered the box up and found that the TO-3 7815 regulator was putting out +20V---bad. I assumed it was broken, so I got another one from Downs and replaced it. Powered it up again and the output was still at +20V (WTF?). My suspicion is that one of the shielding capacitors has failed in some bizarre way, but I didn't have time to check this before I was beckoned to another task. This is where I'll start again next.

Another thing Frank and I noticed as we were figuring out how the driver worked was that the current-specifying resistor of one of the driver stages had not been properly modified along with the others, so it was forcing the feedback loop to rail. This mod was done precariously by adding two perpendicular sandwiched "Radd" resistors on top of the main one, so it's also possible that the ones for this stage had just been knocked off somehow (perhaps by the massive gender-switching ribbon chain hanging down on it). Steve and I noticed that there was a label on the box complaining that some part of the amp for one of the OSEMs wasn't working, but we peeled it off and threw it away because he figured it was outdated.

Anyway, in short, the plan going forward is as follows:

  • For this box
    • Measure the LED driver and PD transZ amp noises with dummy components
    • Compare with LISO to make sure they make sense
    • Measure the noise again with an OSEM connected
    • Based on the above and more LISO modeling, decide if it's a good idea to replace the LT1125's with OP497's
    • Increase the dynamic range by allowing +/-10V output, rather than +/-2V as was needed for old ADCs
  • After
    • Systematically mirror the changes in all other boxes by switching one out at a time

Comments welcome.

  6254   Fri Feb 3 20:58:56 2012 SteveConfigurationGeneralIlluminator Picture
Attachment 1: P1080526.JPG
P1080526.JPG
  6253   Fri Feb 3 20:19:38 2012 ranaUpdateSUSOplev QPD Sum Trends are suspicious

The attached trend shows a problem with the QPD sums.

Why are ETMX and ITMX so much lower than ETMY and ITMY? Are the laser's dying? Or is it the gain inside the QPD? Or the reflectivity of the coatings?

Steve - please check on Monday the laser powers and the ETM/ITM reflectivity for HeNe lasers. Maybe we have to increase the transimpedance gain in the heads.

Attachment 1: a.png
a.png
  6252   Fri Feb 3 19:57:26 2012 ranaConfigurationSUSPSL Shutter closed for SUS hysteresis test

Fri Feb 03 19:57:20 2012

Fri Feb 03 20:25:19 2012 :   Aligned all SUS to center their OL beams

Fri Feb 03 20:29:21 2012:    Aligned all SUS to make OL_PIT = 0.5

  6251   Fri Feb 3 19:54:21 2012 ranaConfigurationIOOMC trans awry

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.

Attachment 1: mctrans.png
mctrans.png
  6250   Fri Feb 3 17:31:09 2012 steveUpdateGeneralgreen welding glass

Schott, green welding glass, shade 14, 3 mm thick  was measured in the beam path of 1.2W, S polarization of 1064nm at ~1 mm diameter size as MC reflected path.

Absorption 95%, R 5% at incident angle 25-50 degrees. It looks like the perfect material for beam trap.

 

Attachment 1: 02031202.JPG
02031202.JPG
  6249   Fri Feb 3 17:29:28 2012 DenUpdateComputersc1lsc kernel

The reason I've killed the c1lsc kernel was the following - when the code starts to run, it initializes some parameters and this takes ~0.2 msec per dof. Now, the old code did nothing with a DOF if C1:OAF-ADAPT_???_ONOFF == OFF. My code still initialized the parameters but then does nothing because no witness channels are given. But it spends 8*0.2 = 1.6 msec for initializing all 8 dof. As the code is called with frequency 2k, this was the reason for crashing. Now I've corrected my code, it compiles, runs and does not kill c1lsc. However, the old code would also kill the kernel if all DOF are filtered. So, when we'll use all 8 DOF, we'll have to split variable initialization.

But this is not the biggest problem. C1OAF model must be corrected, because, as for now, all 8 DOF call the same ADAPT_XFCODE function. As this function uses static variables, they will be all messed up by different DOF signals.

  6248   Fri Feb 3 17:17:47 2012 DenUpdateIOOMC SUS misalignment

Quote:

Reminder / Moral:  Everything cannot be considered to be "working fine" if the MC isn't locking.  See if you can figure out why, and especially if it's something that you screwed up, either fix it, or better yet, ask for help and learn how to fix what you broke.

When I left this morning, Steve was still working with the MC and it was unlocked anyway, I could not check it. By "fine" I meant only watchdogs. The thing is that before starting to work with c1lsc I turned off all the coils. Crazyness that Steve saw was after I turned them on back after reboot. This is a confusing thing - restarting models on c1lsc and burt restoring them is not enough. After I did it, everything at the STATUS MEDM screen was green, but the C1:SUS-???_??PD_VAR values went up after turning on coils. So sus and lsc communicated in a bad manner after the reboot. After restarting x02 model, the watchdogs were fine again.

  6247   Fri Feb 3 16:13:49 2012 steveUpdatePEMLED lights for chamber illumination

Cold LED lights replaced hot halogen ones. Flat LED MYAL 6S,  model #112560002  24VAC

This is a LATE ENTRY.  They were purchased  in Jan 2010 and installed 6 of them around May 2010

Attachment 1: P1080526.JPG
P1080526.JPG
  6246   Fri Feb 3 15:49:10 2012 JenneUpdateIOOMC SUS misalignment

[Jenne, Den]

We moved the MC approximately back to where the sensors for each optic used to be (mostly touching MC2, but a little bit of MC1 to help the refl get back to its max value).  MC is now locked, and with the help of the WFS it's back to nominal.  I forgot to disable the WFS, so I think we aren't perfectly aligned, but we're close enough for the WFS to get us the rest of the way.  We're heading over to JClub right now, so we're going to leave it as-is.

  6245   Fri Feb 3 14:47:51 2012 steveUpdatePEMlaser interlock drawing

 Rough draft of      updated interlock drawing by Ben is here.

 

  6244   Fri Feb 3 14:44:33 2012 JenneUpdateIOOMC SUS misalignment

The mode cleaner is a little misaligned in pitch, and is very misaligned in yaw.  The lowest order mode that is flashing is TEM11.

I had a look-see at the SUS sensors, to see if there were any big jumps.  There were moderately sized jumps on all 3 mode cleaner optics.

SUSjump_3Feb2012.png

The MC's lockloss was at ~8:22am this morning, and went along with a giganto kick to the optics.  Steve tells me that Den might have been kicking up optics while doing computer things this morning, before Steve reminded him to shut off the watchdogs.  However, Steve was also taking phots/measuring things near MC Refl, so maybe he's not totally absolved of blame.  But this really looks like the optics settled to different places after big kicks.

I'm going to try to align the MC mirrors to get back to the sensor numbers from early this morning before chaos began.

Reminder / Moral:  Everything cannot be considered to be "working fine" if the MC isn't locking.  See if you can figure out why, and especially if it's something that you screwed up, either fix it, or better yet, ask for help and learn how to fix what you broke.

  6243   Fri Feb 3 10:48:24 2012 DenUpdateComputersc1lsc kernel

This morning I killed again c1lsc kernel with the new realization of fxlms algorithm. It works fine with gcc compiler during the tests. However, smth forbidden for the kernel is going on. I'll spend some more time on investigatin it. Interesting thing is that I did not even pressed "On" at the OAF MEDM screen to make the code running. c1lsc suspended even before. May be there is some function-name mismatch.

After c1lsc suspention I recomiled back non-working code and rebooted c1lsc. c1sus is also bad after c1lsc reboot as they communicate. I killed x04, lsc, ass, oaf models on the c1lsc computer and sus, mcs, rfm, pem on the c1sus computer. Then I restarted x02 model and restored its burt snapshot from 08:07. After I started all models back and restored their burt snapshots from 08:07. Then I diag reset all started models.

Before starting new fxlms code I've shutted down all the optics so that possible c1lsc suspention would not make them crazy. After reboot I turned the coils back. Everything seems to work fine.

  6242   Wed Feb 1 17:00:57 2012 steveUpdateIOOlaser is back ON

Quote:

 

The 2W PSL laser is turned off.  The danger laser lights are not illuminated at the entry doors because of malfunctioning electronic circuit!!!

Laser safety glasses are still required!  Other lasers are in operation!

 BEN fixed the interlock.  The laser is turned ON. Thanks for all, Rich and Sam who came over to help. Atm1

All emergency shut- off switches, lights and door indicators are working at this moment. More about this tomorrow.

Atm2, PSL enclosure interlock jungle without REAL schematic drawing.....at this point.... We all agreed it is easier to redo the hole thing than find the problem

Atm3, Emergency shut off switches and illuminated signs from  entry doors to AC on-off box  ( Use this switches in emergency ONLY,  otherwise leave alone , even it is labeled obsolete !)

Summery: I still do not really know what was wrong.

 

Attachment 1: P1080525.JPG
P1080525.JPG
Attachment 2: P1080514.JPG
P1080514.JPG
Attachment 3: P1080518.JPG
P1080518.JPG
  6241   Tue Jan 31 17:13:49 2012 steveUpdateIOOonly the PSL laser is off

 

The 2W PSL laser is turned off.  The danger laser lights are not illuminated at the entry doors because of malfunctioning electronic circuit!!!

Laser safety glasses are still required!  Other lasers are in operation!

  6240   Tue Jan 31 14:58:30 2012 kiwamuUpdateIOOlaser shuts down

[Steve/ Kiwamu]

 We found that the laser had completely shut off for ~ 4 hours even with all the PSL doors closed.

We are guessing it is related to the interlock system and Steve is working on it to fix it.

Quote from #6239

 The 2W Innilight shutdown shut when I opened side door for safety scan. This was not a repeatable by opening -closing side doors later on. Turned laser on, locked PMC and MC locked instantly. The MC was not locked this moring and it seemed that the MC2 spot was still some high order mode

like yesterday. MC lock was lost when the janitor bumped something around the MC.

 

  6239   Tue Jan 31 08:44:10 2012 steveUpdateIOOlaser shuts down

 

 The 2W Innilight shutdown shut when I opened side door for safety scan. This was not a repeatable by opening -closing side doors later on. Turned laser on, locked PMC and MC locked instantly. The MC was not locked this moring and it seemed that the MC2 spot was still some high order mode

like yesterday. MC lock was lost when the janitor bumped something around the MC.

Attachment 1: laseroff.png
laseroff.png
  6238   Mon Jan 30 23:10:02 2012 kiwamuUpdateSUSdrift mon script needs to be fixed

[Rana / Kiwamu]

We tried to set some parameters for the suspension drift monitor but the old matlab script, which automatically sets the values, didn't run because it uses the old mDV protocol.

The attached link below is a description about the script.

https://wiki-40m.ligo.caltech.edu/Computers_and_Scripts/All_Scripts#Drift

It needs to be fixed or upgraded by pynds.

  6237   Mon Jan 30 16:18:51 2012 steveUpdatePEMRoscolux colored film transmittance at 1064 nm

 

 Roscolux filter films  #74 night blue,  0.003" thick  and  #26 light red, 0.002" thick  were measured in the beam path of  ~6 mm diameter,  1W 1064 nm .

T 90%  + - 5% at 0-30 degrees of  incident angles and R ~10 % 

These sandwitched thin films of policarbonate-polyester filters are not available in thicker forms. Rosco is recommending them to be cooled by air if used in high power beam.

These filters did not get warm at all in 1W, so absorption must be very small.

  6236   Mon Jan 30 08:17:06 2012 steveUpdateIOOPMC

Quote:

I have realigned the beam pointing to PMC. The transmitted light increased from 0.74 to 0.83.

The misalignment was mainly in pitch.

 The PMC pointing has changed, so MC is resonating in high order modes.

Attachment 1: sickPMC.png
sickPMC.png
  6235   Fri Jan 27 17:16:05 2012 kiwamuUpdateLSChypothetical glitch scenario

Here is a hypothetical scenario which could make the glitches in the LSC error signals. It can be considered as a 4 step phenomenon.

        (1) up conversion noise due to a large motion at 3 Hz

   => (2) rms level exceeds the line width (a.k.a. linear range) in some LSC sensors

   => (3) unlocks some of the DOFs  in a moment

   => (4) glitches due to the short unlock.

- - plan  - -

 In order to check this hypothesis the low finesse PRMI must serve as a good test configuration.

What I will do is to gradually decrease the offset in MICH such that the finesse of PRMI becomes higher.

And at each different finesse I will check the spectra, glitch rate, and etc.

Quote from #6231

        Low finesse PRMI      

In this configuration NO glitches ( a high speed signal with an amplitude of more than 4 or 5 sigma) were found when it was locked.

Is it because I didn't use AS55 ?? or because the finesse is low ??

Also, as we have already known, the up conversion noise (#6212) showed up -- the level of the high frequency noise are sensitive to the 3 Hz motion.

  6234   Fri Jan 27 16:55:28 2012 JenneUpdateGreen LockingY-green realigned

The Yarm green laser really wanted to lock on a 01/10 mode, so Kiwamu suggested I go inside and realign the green beam to the arm.  I did so, and now it's much happier locked on 00 (the Yarm is resonating both green and IR right now).

  6233   Fri Jan 27 13:13:03 2012 JenneUpdateSUSITMs tripped

Sitting down to start cavity measurements, I found both ITMs tripped.  It must have happened a while ago (I didn't bother to check dataviewer trends) because both had rms levels of <5 counts, so they've had a while to sit and quiet down.

  6232   Fri Jan 27 09:05:41 2012 steveUpdateSUSOSEM locking plunger

Quote:

Our existing 300 series SS plungers from McMastercar #8476A43 are silver plated as Atm2 shows.

Problems:  1, they become magnetized after years being close to the magnets

                     2, they oxidize by time so it is hard to turn them

                    

I looked around to replace them.

Titanium body, nose and beryllium copper spring. None magnetic for UHV enviorment.

Can be made in 7 weeks at an UNREASONABLE $169.00 ea at quantity of 50

 In order to get a better price from Vlier's Tom Chen I changed Ti body back to SS304L-siver plated and music wire spring. The price is still ~$120 ea. at quantity 50

I will talk to Mike G about modifying the  McMaster plunger with a hex nut.

  6231   Fri Jan 27 06:07:47 2012 kiwamuUpdateLSCglitch hunting

I went through various IFO configurations to see if there are glitches or not.

Here is a summary table of the glitch investigation tonight. Some of the cells in the table are still not yet checked and they are just left blank.

IFO configuration  Yarm
Xarm
MICH
Half PRMI
low finesse PRMI
PRMI (carrier)
PRMI (sideband)
DRMI
AS55 NO NO NO   up conversion noise glitch glitch glitch
REFL11 NO NO NO   up conversion noise
glitch glitch glitch
REFL33 NO NO NO   - glitch glitch glitch
REFL55 NO NO NO   up conversion noise
glitch glitch glitch
REFL165 NO NO NO   - glitch glitch glitch
POX11 - NO NO     glitch glitch glitch
POY11 NO - NO     glitch glitch glitch
POP55 - -            
                 

 

        Low finesse PRMI      

The low finesse PRMI configuration is a power-recycled MIchelson with an intentional offset in MICH to let some of the cavity power go through MICH to the dark port.

To lock this configuration I used ASDC plus an offset for MICH and REFL33 for PRCL.

The MICH offset was chosen so that the ASDC power becomes the half of the maximum.

In this configuration NO glitches ( a high speed signal with an amplitude of more than 4 or 5 sigma) were found when it was locked.

Is it because I didn't use AS55 ?? or because the finesse is low ??

Also, as we have already known, the up conversion noise (#6212) showed up -- the level of the high frequency noise are sensitive to the 3 Hz motion.

  6230   Fri Jan 27 05:21:43 2012 kiwamuUpdateGreen Lockingfine alignment of the Y end green setup

I did a fine alignment on the Y end green setup. The green light became able to be locked again.

Quote from #6227

 The alignment is finished after the realization that the 3rd steering mirror had to be adjusted too.

  6229   Thu Jan 26 19:28:02 2012 kiwamuUpdateIOOPMC low transmission

After I recovered the lock of PMC, I found that the PMC transmission was quite low. It was about 0.26 in the EPICS display.

I zeroed the PSL temperature feedback value which had been -2.3 and then the PMC transmission went back to a normal value of 0.83.

I believe it was because the PSL was running with two different oscillation modes due to the big temperature offset.

  6228   Thu Jan 26 15:35:23 2012 JenneUpdateIOOMC ~1Hz badness

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.

  6227   Thu Jan 26 10:17:01 2012 steveUpdateGreen Lockinggeen pointing into y arm is realigned

Quote:

I  placed an other Y2-LW-1-2050-UV-45P/AR steering mirror into the beam path of the green beam launching in order to avoid the ~30 degrees use of the 45 degrees mirror. The job is not finished.

 The alignment is finished after the realization that the 3rd steering mirror had to be adjusted too.

The input power increased from 1.2 to 1.4 mW

Attachment 1: P1080513.JPG
P1080513.JPG
  6226   Thu Jan 26 08:36:38 2012 steveUpdateSAFETYevacuation drill

It started with fire alarm test yesterday at 14:50 All alarms are  functioning VERY loud and their flashers are bright. Evacuation drill followed. We assembled at north west corner of the 40m building and counted 6 heads.

Nobody was left sleeping inside. Bob carried the success report of the drill to PMA office immediately.

  6225   Thu Jan 26 06:09:52 2012 kiwamuUpdateGreen Lockingnoisy AS55

During the Y arm ALS I found that the noise of the AS55 demod signal was worse than that of POY11 in terms of the Y arm displacement.

There is a bump from 500 mHz to 100 Hz in the AS55 signal while POY11 didn't show such a structure in the spectrum.

 

The plot below is the noise spectra of the Y arm ALS. The arm length was stabilized by using the green beat-note fedback to ETMY.

In this measurement, POY11 and AS55 were served as out-of-loop sensors, and they were supposed to show the same noise spectra.

In the plot It is obvious that the AS55 curve is louder than the POY curve.

Yarm_ALS_2012Jan25.png

  6224   Thu Jan 26 05:40:10 2012 kiwamuUpdateLSCglitch in the analog demodulated signals

Indeed the glitches show up in the analog demodulated signals. So it is not an issue of the digital processing.

With an oscilloscope I looked at the I/Q monitor outputs of the LSC demodulators, including REFL11, REFL33, REFL55, POY11, AS55 while keep locking the carrier-resonant PRMI.

I saw some glitches in REFL11, REFL55 and AS55. But I didn't see any obvious glitches in REFL33 and PO11 because the SNR of those signals weren't good enough.

 


(some example glitches)

The attached plot below is an example shot of the actual signals when the carrier resonant PRMI was locked.

The first upper row is the spectrogram of REFL11_I, REFL55_I, REFL33_I and AS55_Q in linear-linear scale.

The second row shows the actual time series of those data in unit of counts.

The bottom row is for some DC signals, including REFLDC, ASDC and POYDC.

 

glitch.png

You can see that there are so many glitches in the actual time series of the demod signals (actually I picked up the worst time chunk).

It seems that  most of the glitches in REFL11, REFL33 and AS55  coincide.

The typical time scale of the glitches was about 20 msec or so.

Note that the PRMI was locked by REFL33 and AS55 as usual.

  6223   Wed Jan 25 17:32:03 2012 steveUpdateGreen Lockinggeen pointing into y arm is misaligned

I  placed an other Y2-LW-1-2050-UV-45P/AR steering mirror into the beam path of the green beam launching in order to avoid the ~30 degrees use of the 45 degrees mirror. The job is not finished.

  6222   Wed Jan 25 15:04:41 2012 JenneBureaucracySAFETY40m SOS supplies moved off of cleanroom flow bench

Bob, Callum and Daphen noted that our keeping a JDSU HeNe (max power <4mW) is against somebody's SOP.  So I cleared everything that relates to 40m SOS suspending to the bottom shelf of the 2nd cabinet in the cleanroom (the back set of cabinets nearest the flow benches).  The door has a nifty label.  Things that are in there include:

HeNe

HeNe mount

QPD and micrometer mount

microscope and micrometer mount

iris

Al beam block

Magnet gluing fixture

dumbbell gluing fixture

The electronics that we use (HeNe's power supply, 'scope, QPD readout) are still on the roll-y thing under the flow bench.

  6221   Wed Jan 25 02:59:46 2012 kiwamuUpdateGreen LockingY arm ALS noise budget

Surprisingly increasing the gain of the whitening filter didn't improve the noise curve.

It suggests that the ADC noise is not the limiting factor below 10 Hz.

Quote from #6220

Though, it turned out that the MFD's ADC is now limiting the noise in a frequency band of 200 mHz - 5 Hz.

So tonight I will increase the gain of the whitening filter to push down the ADC noise more.

 

  6220   Tue Jan 24 18:11:13 2012 kiwamuUpdateGreen LockingY arm ALS noise budget

I did some more stuff for the Y arm ALS and updated the noise budget:

After the works, the rms displacement improved a little bit, so it is now at 24 pm in rms.

Though, it turned out that the MFD's ADC is now limiting the noise in a frequency band of 200 mHz - 5 Hz.

So tonight I will increase the gain of the whitening filter to push down the ADC noise more.

 

Yarm_ALS_2012Jan19.png

 

(What I did)

 + added the DAC noise and comparator noise based on measurements.

 + redesigned the servo filter shape to suppress the seismic noise below 10 Hz.

 The attached plot below shows the newly designed open loop transfer function together with the old one for a comparison.

UGF is at 120 Hz and the phase margin is about 27 deg.

  newservo.png

  • FM7 = resonant gain (17)
  • FM6 = resonant gain (3)
  • FM5 = zero(1) * pole(500)
  • FM4 = pole(1) * zero(40.) * 40.
  • FM3 = pole(1) * zero(40.) * 40.
  • FM2 = pole(0.001)*zero(1)*1000.
  6219   Tue Jan 24 13:36:05 2012 ZachBureaucracyGeneralIf I'm Peter Pan...

jamie_rufio.png

JA - MIE - RO!

  6218   Mon Jan 23 23:12:00 2012 kiwamuUpdateIOOPMC realignment

I have realigned the beam pointing to PMC. The transmitted light increased from 0.74 to 0.83.

The misalignment was mainly in pitch.

  6217   Mon Jan 23 15:43:47 2012 JenneUpdateIOOPMC realignment

Quote:

I realigned the incident beam to PMC at 23:30. The transmitted light went up from 0.78 to 0.83.

 Do we have PSL pos and ang QPD trends?  We should start watching them, because the PMC drifted back down to 0.76 transmission, ~3.5 days after Kiwamu realigned it (his elog is from last Thurs).  Not so awesome.

I walked through the control room just now and found both PMC and MC unlocked.  They're both locked now, but with PMC transmission 0.76, MC transmission ~24,500.

  6216   Fri Jan 20 17:05:59 2012 ranaUpdateGreen LockingY arm ALS : time series

                        One of my goals this week is to get people to make plots with physical units:

That ALS plot would be 5x cooler if the POY11 signal could be in meters instead of counts or cubits.

  6215   Fri Jan 20 16:24:50 2012 kiwamuUpdateGreen LockingY arm ALS : time series

Here is a new time series plot showing how stably ALS can control the arm length.

In the middle of the plot the cavity length was held at the resonance point for ~ 2 min. and then it passed through the resonance point to show the full shape of the PDH signal.

Apparently the PDH signal is now quieter than before (#6133)

time_series.png

Quote from #6214

One of my goals in this week is : measurement of the current best ALS noise budget.

 

  6214   Fri Jan 20 15:59:02 2012 kiwamuUpdateGreen LockingY arm ALS noige budget

One of my goals in this week is : measurement of the current best ALS noise budget.

Last night I took a new noise spectra of the Y arm ALS, which is shown in the attached figure below.

The displacement of the arm cavity observed from the IR PDH is at 66 pm in rms. In the measurement the arm length was stabilized with the ALS technique.

 

Yarm_ALS_2012Jan19.png

 

  6213   Thu Jan 19 23:34:52 2012 kiwamuUpdateIOOPMC realignment and HEPA

I realigned the incident beam to PMC at 23:30. The transmitted light went up from 0.78 to 0.83.

Also I decreased the HEPA level down to 20 % for the night time locking.

  6212   Wed Jan 18 16:31:10 2012 kiwamuUpdateLSCestimation of optical length between PRM and scattering object

I searched for a scattering body in the REFL path.

According to the result the REFL path on the AS table is innocent.

 

The idea of the search method is given as follows:

  •   Put a 1/10 ND attenuator at the origin of the REFL path on the AS table.
  •   Of course this reduces the signal level by the same factor of 10 in the REFL11_I demod signal.
  •   If the scattering body is in the REFL path the up conversion noise will be smaller by a factor of 100 because the scattered light go across the attenuator twice.

 

 The attached plot below is the spectra of REFL11 with the 1/10 attenuator at the origin of the REFL path when the beam is single-bounced from PRM.
In the measurement PRM_POS was driven at 10 Hz with an amplitude of 1700 all the time. This is exactly the same situation as that explained in the previous elog entry (#6211).
You can see that the up conversion noise level also decreased by the same factor of 10, which suggests there are no scattering object in the REFL path.
Note that the data with the attenuator in place is intentionally scaled by multiplying a factor of 10 for comparison.
ND1atten.png
 

Quote from #6211

Assuming that PRM is interfering with some other optics, I have estimated the optical distance between PRM and an object that interferes with PRM.

The optical distance is estimated to be 9.5 +/- 0.5 m.

If we believe this number the object is most likely outside of the vacuum chambers.

 

  6211   Wed Jan 18 14:28:36 2012 kiwamuUpdateLSCestimation of optical length between PRM and scattering object

Assuming that PRM is interfering with some other optics, I have estimated the optical distance between PRM and an object that interferes with PRM.

The optical distance is estimated to be 9.5 +/- 0.5 m.

If we believe this number the object is most likely outside of the vacuum chambers.

 

 (The measurement)

  In order to estimate the optical length between PRM and a scattering body, I swept the frequency of the main laser by actuating on the MC length.
With the sweep, the laser frequency go across some fringes and basically it allows us to estimate the FSR of a very low finesse cavity formed by PRM and the scattering body.
Therefore we get the the optical distance based on the resultant FSR.
 
  The measurement goes as follows:
  1.  Preparation : calibration of the MC2 actuator as a frequency actuator (for more details, see the next section)
  2.  Set the interferometer to the single-bounce configuration such that the beam directly is reflected back from PRM
  3.  Take spectra of REFL11_I without driving any optics. This spectra tells us how quiet the noise normally is.
  4.  Drive MC2_POS at 10 Hz with an amplitude of 10000 counts so that we can see the high frequency up conversion noise
    • The frequency was chosen such that the excitation is out of the local damping bands
    • The amplitude was chosen to be as big as possible until the MC unlocked
    • With this drive, the laser frequency should change by 20 MHz peak-peak at 10 Hz.
  5.  Record the noisy spectrum when the MC2_POS was driven.
  6.  Drive PRM instead of MC2 at 10 Hz.
    • Adjust the amplitude of the excitation such that the cut-off frequency of the up conversion noise matches with that of the MC2 driven case.
    • The amplitude was found to be 1700 - 2000 counts, this uncertainty is currently limiting the precision of the optical distance estimation.
    • With this amount of the drive, PRM moves by 0.8 um peak-peak at 10Hz.
  7. Estimate the optical length based on the amount of the drives for PRM and MC2.
    • Estimate the FSR using the following relation df/FSR = dx/ (lambda/2). => FSR = 17 MHz
    • Since FSR = c/ (2L),  L = c/(2 FSR) = 9.5 m or so
scattering.png

 

 

(Calibration of the MC2 actuator)

 To do the measurement described above, the MC2 actuator must be calibrated in terms of a frequency actuator.
I did the same old technique (#4721): lock a cavity, adjust the UGF as low as possible, and shake an actuator of interest.
This time I used the half-PRM (PRM + ITMY) for this measurement.
The actuator responses are calibrated from that of displacement to frequency by using df/f = dx/L and assumed that L = 6.760 (#4585).
Also the PRM actuator was measured such that we can use this as a reference since we already know the response in displacement (#5637).
 The attached plot below is the actual responses that I measured yesterday. The y-axis is calibrated to Hz/counts.
 

 

calibration.png

 

Quote from #6202

Is PRM making some fringes with some other optics ??

  6210   Wed Jan 18 12:38:44 2012 steveUpdatePEMAcrylic plexiglass transmittance

Acrylite-Gp.pptx

Transparent- clear plexyglass from tree different sources were measured in 1064 and 532 nm light.

Samples: a, clear Acrylic-GP 0F00  from Ridout Plastics in thickness 0.7" ,  made by  Evonic Ind

                   b, clear cast acrylic from Mc Master Carr in thickness 0.94" , likely  made by Reynolds-Cast

                   c, clear cell cast  plexyglass from Delvie's Plastics - Utah in thickness  0.93" , maker not known

PMC reflected beam was used at 92 mW and 6 mm diameter at incident angle 0-25 degrees.

All tree samples agreed on Transmittance of ~90%, Reflectivity ~3-4% and calculated Adsorption ~6-7%

 

Transparent Colored Acrylic orange-amber #2422   from www.eplastics.com in 0.12" thickness gave  T 96%,  R 1% and  Ab-calc ~3% in the beam of 92 mW 1064  nm at 6 mm diameter.

 

Transparent , colored   Light Red #26 thin film filter   policarbonate-polyester   0.002" thick   from Roscolux measured T 81% of 115 mW 1064 nm

 

Now I changed power meter FieldMate to Ophir and the light source to laser pointer 2.2 mW  ~532 nm  with 1-2 mm beam diameter.

Orange - amber #2422  sample, 0.12" thick,  T 1% ,  R 4%  and  Ab-calculated ~95%, estimated visibility  ~50% It does cut out the green at this low power level.

 Light red #26  sample  T 0.5%  at 2.5 mW of 532 nm . The transparent green is not visible.  The softening point of this sandwiched polycarbonate-polyecter filter is 160C. Estimated VLT of this film ~40%

 

SUMMERY:

Clear and colored acrylics'  @ 1064 nm  transmittance 90% or higher  regardless of thickness. Softenig point 115 degrees C

Colored acrylic and colored policarbonate film are adsorbing the low power green and they  transmit the 1064nm beam.

Options to consider: a, acrylic laser safety shield liner of  0.125" thick inside of 1" thick clear acrylic  box, OD +5 @1064 and OD +4 @ 532nm,  amber color VLT 27%,  150$/sqft

                                      b, thin metal liner for 1" wall acrylic box, VLT 0%

                                     

 

Attachment 2: roscogel_red#26_film.pdf
roscogel_red#26_film.pdf
  6209   Wed Jan 18 12:36:26 2012 kiwamuUpdateLSCwiped a steering mirror on the REFL path

I wiped both surfaces of the REFL second steering mirror.

However no improvements. The glitches still remain.

 

(Pic.1 before wiping, Pic.2 after wiping)

DSC_3861_small.jpgDSC_3863_small.jpg

Quote from #6206

 Last night I found that there were many dust particles on the second steering mirror in the REFL path on the AS table.

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