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ID Date Author Type Category Subjectup
  1709   Tue Jun 30 23:09:40 2009 AlbertoUpdateLockingchronicles of some locking attempts

Tonight I tried to lock the interferometer. At the first attempts the arm power didn't go above about 4. The mode cleaner seemed to be not well aligned and it lost lock or got stuck on a wrong mode. I had to run the MC_UP and MC_DOWN scripts to lock it again.

After that the locking proceed more smoothly; at least till a power level in the arms of about 60. Then again the mode cleaner lost lock and I had to run the scripts again. Without the MCWFS servo off the MC reflected power is still rather high (about 1.7); also even when the WFS servo is engaged the reflected power is about 0.5, versus 0.3 that it should be.

Those are both signs of a not very good alignment. Tomorrow I'll have to work on the injection periscope on the PSL table to try to fix that.

  12802   Mon Feb 6 10:05:28 2017 SteveUpdateSUSclamped cables

The bottom 5 cable connections from Sat-Amp to Whittering Filter at 1X5 were clamped today.

Attachment 1: clamped.jpg
  7146   Fri Aug 10 17:17:41 2012 Alex Masha DenUpdatePEMclassify seismic c code

Den and I installed a module in the c1pem model which has a feedforward neural network to classify seismic disturbance (10 means quiet, 20 truck, 30 earthquake). There is a channel SEIS_CLASS which should specify the class of the seismic signal. The code works for signals sampled at 256 Hz, so an anti-aliasing filter must be installed in order to decimate from the 2048 model.

The models were compiling slowly, so Alex removed the archiving feature (gzip and tar were taking a lot of time).

Den and I also had trouble with a simple for loop in our model, so we talked to Alex who noted that the -O3 compiler unravels for loops in a buggy way. Thus, we have compiled c1pem using the -O compiler.

PS: the Trilium seismometer now has legs.

  7147   Fri Aug 10 17:38:29 2012 DenUpdatePEMclassify seismic c code


Den and I also had trouble with a simple for loop in our model, so we talked to Alex who noted that the -O3 compiler unravels for loops in a buggy way. Thus, we have compiled c1pem using the -O compiler. 

Alex also modified RCG script to generate -O in the Makefile for c1pem model:

controls@pianosa:/opt/rtcds/rtscore/release/src/epics/util 127$ svn diff
feCodeGen.pl (revision 2999)
feCodeGen.pl (working copy)
@@ -3183,7 +3183,12 @@

print OUTM "\n";
print OUTM "ALL \+= user_mmap \$(TARGET_RTL)\n";
+# do not optimize c1pem
+if ($skeleton eq "c1pem") {
+print OUTM "EXTRA_CFLAGS += -O -w -I../../include\n";
+} else {
print OUTM "EXTRA_CFLAGS += -O3 -w -I../../include\n";
print OUTM "EXTRA_CFLAGS += -I/opt/gm/include\n";
print OUTM "EXTRA_CFLAGS += -I/opt/mx/include\n";

  11707   Thu Oct 22 08:52:04 2015 SteveUpdateVACclean RGA scan after sweaty Maglev

Clean comparable scan at vacuum normal. There was no backstreaming.

Attachment 1: clean_scan.png
  8004   Tue Feb 5 15:31:03 2013 SteveUpdateGeneralclean assembly room benches cleaned up

Manasa, Jamie and Steve,

Tip-Tilts and parts moved into the most north " 40m "  cabinet  in the assembly room.

Green-black glass and related components were moved to the 40m E0 cabinet in plastic boxes.

The north flow bench has a few items that belong to us: HE/Ne laser, qpd on translation stages, an iris and one red mirror.  These were moved to the north edge of this bench.

However this leveled table is still full with other people's stuff

Attachment 1: IMG_0057.JPG
Attachment 2: IMG_0061.JPG
  5158   Tue Aug 9 16:40:12 2011 steveUpdateGeneralclean room coat counts

I measured the particles coming off of new- unused clean room coat. Tyvek, Convertors, Allegiance #9393 measured  10 counts of 0.3 micron at 1 minute and 0 count at 7 minute.

The 0.5 micron size  measured 0 at both times. Jenne's used coat measured 20 counts of 0.3 micron  and 0 counts for 0.5 micron at 1 minute. ( counts / cf- min)

The HEPA tent background is consistently 0 when it's CP STAT 100 curtains are closed.

Attachment 1: P1080155.JPG
  5303   Thu Aug 25 17:14:49 2011 steveUpdateVACclean room fashion changes

Jamie is modeling our next generation  in-vac & clean room bonny suit that Jenne and myself already tested.

It is quite bearable with our traditional cleanroom beret-bouffant cap. Please use these in the future.

This will help to avoid the farther degradation of somewhat dusty 40m vac envelope.

It is the required dress code to enter the clean assembly room in the 40m.

 We have small, med, large and x-large in stock. I'm getting larger sizes.

It will not allow certain people to climb inside the vacuum chamber in dirty pants.

Attachment 1: P1080185.JPG
Attachment 2: P1080183.JPG
  4386   Tue Mar 8 15:23:16 2011 steveUpdatePEMclean room gloves

Ansell AccuTech 91-300 clean room gloves  ONLY in the 40m lab.

Cleaning and preparation must be carried out in these gloves also.

  3705   Wed Oct 13 11:09:28 2010 yutaUpdateComputersclean-installed CentOS 5.5 on mafalda

Dear mafalda,

Sorry for leaving you alone.
We put ethernet cable in you. You can talk to everyone now!
We created a user "controls" correctly. (UID: 1001)
We mounted linux1:/home/cds/ to your directory /cvs/cds.

Truly yours,
Joseph Betzwieser
Yuta Michimura



I clean-installed CentOS 5.5(32bit) on mafalda.
No firewalls, no SELinix.

 Yuta has removed my ethernet connection. Help me!!!

rossa:mDV>ping mafalda
PING mafalda.martian ( 56(84) bytes of data.
From rossa.martian ( icmp_seq=2 Destination Host Unreachable
From rossa.martian ( icmp_seq=3 Destination Host Unreachable
From rossa.martian ( icmp_seq=4 Destination Host Unreachable

--- mafalda.martian ping statistics ---
5 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3999ms
, pipe 3


  3585   Fri Sep 17 17:35:35 2010 steveUpdatePEMcleaned up at 1Y1 PSL rack

Cleaned up cables on the top and bottom. Vacuumed both areas. We still have some remaining shading from the MOPA umbilical and more unknown BNC cables hanging around.

  11388   Wed Jul 1 11:45:48 2015 SteveUpdatePEMcleaning around ETMX chamber

Keven is our regular janitor is out for a few weeks.

The sub is careful- gentel Mario. We wiped arouind the vertex cambers north side on the floor and east arm racks.


Mario wiped the floor around the ETMX chamber today.

  11372   Tue Jun 23 11:18:20 2015 SteveUpdatePEMcleaning around chambers

Keven is our regular janitor is out for a few weeks.

The sub is careful- gentel Mario. We wiped arouind the vertex cambers north side on the floor and east arm racks.


  9914   Tue May 6 09:46:50 2014 steveUpdatePEMcleaning day

 Keven and Steve,

We cleaned around the Vertex chambers, PSL and MC2 floor areas.


Attachment 1: 120d.png
  4952   Thu Jul 7 10:25:34 2011 steveHowToGeneralcleaning out refregerator

Please ask the owner unless  it is rotten. Do not put food into garbage can inside. Take them outside so you are not inviting ants !

  9092   Fri Aug 30 14:31:57 2013 SteveUpdateGeneralcleaning up

I cleaned up around MC2 and 1Y1 area this morning.

ETMY NPRO moved from the side to the center of the low shelf. Thorlab catalog " as spacer " removed after lunch.

The Lightwave Controller values: LT 40.4C,  LTEC +0.1V,  T 41.041C,  Pwr 239 mW,  Adj 0,  DC 1.82A,  DPM  0.0V,  Neon OFF,  Ldon OFF,  Display 5,  DT 21.0C,  Dtec +1.0V


Attachment 1: MC2areaCP.jpg
Attachment 2: 1Y1areaCleanedUp.jpg
Attachment 3: ETMY_NPROmoved.jpg
  13970   Fri Jun 15 08:09:15 2018 SteveBureaucracyGeneralcleaning up at the PSL enclousure

The cabeling was cleaned up a little bit yesterday morning. The upper back side is still massy.

Attachment 1: before.jpg
Attachment 2: after.jpg
Attachment 3: back_side.jpg
  8732   Thu Jun 20 09:33:42 2013 SteveUpdateGeneralcleanup

Office work benches were cleaned up yesterday. Anti-image filter boards were moved to north wall of the control room. Koji's pd- electronics box  placed next to water dispenser.

The removed ETMY optical table: TMC 4' x 2' x  4" with Aluminum enclosure was placed on table in the east arm.

Attachment 1: tmc3x2.jpg
  8518   Wed May 1 10:42:35 2013 SteveUpdateLSCcleanup


 Optics from the car were placed into glass door cabinet E0

  16796   Thu Apr 21 16:36:56 2022 TegaUpdateVACcleanup work for vacuum git repo

git repo - https://git.ligo.org/40m/vac

Finally incorporated the FRGs into the main modbusIOC service and everything seems to be working fine. I have also removed the old sensors (CC1,CC2,CC3,CC4,PTP1,IG1) from the serial client list and their corresponding EPICS channels. Furthermore, the interlock service python script has been updated so that all occurrence of old sensors (turns out to be only CC1) were replaced by their corresponding new FRG sensor (FRG1) and a redundnacy was also enacted for P1a where the interlock condition is replicated with P1a being replaced with FRG1 because they both sense the main volume pressure.

  2124   Tue Oct 20 10:46:18 2009 steveUpdateIOOclipping IP-ANG beam at ETMX chamber

Initial pointing beam is clearly clipping on 2" pick off mirror in  ETMX vacuum chamber.

Atm. 1  The pick off mirror is just north west of the ETMX test mass

Atm. 2 The camera is looking in from the north view port of ETMX chamber. The back side of pick off mirror is visible now with the face view of the "IP-ANG-OUT" mirror.


Attachment 1: PA200175.JPG
Attachment 2: PA200177.JPG
  12811   Wed Feb 8 10:16:39 2017 steveUpdateSUSclipping ITMX oplev

The ITMX oplev beam is clipping. It will be corected with locked arm


Attachment 1: ITMX_oplev_clipping.jpg
Attachment 2: ITMX_clipping.jpg
  13861   Fri May 18 07:41:01 2018 steveUpdateSUSclipping ITMX oplev

The ITMX oplev still clipping


The ITMX oplev beam is clipping. It will be corected with locked arm



  6902   Mon Jul 2 10:45:25 2012 JenneSummaryGeneralclipping at BS


No significant change was found inside the vacuum. We still see clipping at the Faraday, and also, we saw clipping by BS coil holder. Using PZT1, we could make it better, but this might be causing PRC problem -- BS is inside the PRC, too.

 Yuta just told Jamie and I that when he and Koji were looking at things yesterday, they saw that the beam spot was roughly at the center of the PRM, but was clipping on the lower OSEM holder plate on the BS.  This indicates that the beam spot on the BS is much too low.  The easiest way I can see this happening is poor pitch pointing with the tip tilts, which we unfortunately don't have active control over.

Recall elog 3425, where I mentioned some pretty bad pitch pointing after a TT was moved from the cleanroom, to the chamber, back to the cleanroom.  I think that we may need to check the pitch pointing at the chamber before installing tip tilts in the future.

  6900   Sun Jul 1 23:48:15 2012 yutaSummaryGeneralclipping at BS, my plan

[Koji, Yuta]

We aligned PRMI and inspected BS chamber. Last inspection by Jamie and I (see elog #6897) was done when nothing is aligned, so I wanted to see the difference.
Aligning PRMI at low power was difficult for me, because I see no fringe at ASDC PD nor REFLDC PD. I just aligned them by looking at AS/REFL camera. The beam shape at AS looked as bad as when the usual power.

No significant change was found inside the vacuum. We still see clipping at the Faraday, and also, we saw clipping by BS coil holder. Using PZT1, we could make it better, but this might be causing PRC problem -- BS is inside the PRC, too.

We also took some pictures of PR3 and PRM(attached). The arrow pointing HR is correctly pointing inside the PRC. Seeing is believing.

Yuta's plan:
  We might have to avoid clipping at BS (and Faraday) by aligning input optics inside the vacuum. If we are going to align them, I think we should start from centering MC beam spot positions and the whole alignment could take more than a week. I don't want to spend too much time on the alignment. Also, we are going to install tip-tilts on the next big vent, so we have to redo the alignment anyway.
  So, my plan is as follows;

1. Take lots of photos and close the door on Monday(June 2).

2. Pump on Tuesday(June 3).

3. Restart working on ALS. For example, demonstration of FPMI using ALS.

4. We also can do some characterization of PRC, like measuring power recycling gain for PRMI/PRFPMI, mode scan for PRC using AUX laser from AS port, and so on. We need some calculation for clipping tolerance, too.

  Any objections?

Attachment 1: PR3.JPG
Attachment 2: PRM.JPG
  6901   Mon Jul 2 00:41:13 2012 ranaSummaryGeneralclipping at BS, my plan


 Start pumping on Monday before Steve goes home.

  8114   Wed Feb 20 03:13:10 2013 yutaUpdateAlignmentclipping centering checklist

I attached clipping/centering checklist for the alignment.
Blue ones are the ones we checked today. Red ones should be checked tomorrow. Circles indicate centering on the optics, rectangles indicate clipping check, and arrows indicate retro-reflecting or bounces.
We found mis-centering on MMT1, PR2 and SR3 tonight (by ~0.5 beam diameter). They are also indicated.

I think we don't want to touch MMT1 and PR2 anymore, because they change input beam pointing.
I'm a little bit concerned about high beam on SR3, because we had PRC flashing in vertical higher order modes. We also see ETMX slider values high in pitch (~ 5.4).
Also, the diameter of ETMX reflected beam on ITMX looked larger and dimmer than ITMX transmitted beam, which doesn't seem reasonable.

Wednesday, Feb 20:
 - tweak TT1/TT2 and PRM so PRC flashes
 - re-check Yarm/Xarm bounces
 - center beam on all AS optics, starting from SR2
 - make sure REFL and AS is clear
 - check if TRY/TRX are coming out from the ends
 - check beam centering on mirrors in IMC/OMC chamber as far as you can reach
 - inject green from both ends
 - make sure green beams are not clipped by mirrors on BS chamber, IMC/OMC chamber
 - re-center all oplevs, with no clipping
 - check all OSEM values
 - take pictures of flipped PR2 and input TTs (and everything)
 - close all heavy doors and put the access connector back

Thursday, Feb 21:
 - make sure we can lock PRMI
 - start pumping down when Steve arrives

Attachment 1: ClippingCenteringChecklist.pdf
ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf
  8122   Wed Feb 20 20:58:37 2013 yutaUpdateAlignmentclipping centering checklist

Blue ones are the ones we checked yesterday.
Green ones are the ones we checked today.
Red ones are the ones we couldn't check.

We noticed mis-centering on green optics and partial clipping of higher order modes, but we did not touch any green optics in-vac. This is because green beam from Y end and X end has different spot positions on the green optics after periscopes. We confirmed that direct green beam from ends are not clipped.

I believe we have checked everything important. Any other concerns?

Attachment 1: ClippingCenteringChecklist.pdf
ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf ClippingCenteringChecklist.pdf
  8123   Wed Feb 20 21:12:37 2013 ranaUpdateAlignmentclipping centering checklist


 Is the beam going towards the OMC going to cause backscatter because of uncontrolled OMC or can we park that beam somewhere dark?

  8124   Wed Feb 20 21:56:08 2013 yutaUpdateAlignmentclipping centering checklist

I'm not sure about the OMC situation at 40m. I think there are no direct beam reflected back into IFO from OMC path. There must be some backscatter, but we have to open OMC chamber again to put a beam dump.
I don't think we want to put one in OMC path for this pump-down, but we can put a beam dump to dump reflected beam from mis-aligned SRM tomorrow, if available.

  9628   Wed Feb 12 14:59:36 2014 SteveUpdateSUSclipping removed from PRM oplev

 The input pointing of PRM oplev beam was streered just a touch to remove clipping from it's return. 

The spots  did not move visibly on these two lenses.  The spot diameter on the qpd is  ~1.5 mm,  65 micro W and 3440 counts.  

Attachment 1: PRMoplPointing.jpg
Attachment 2: PRMoplevReturn.jpg
  9629   Wed Feb 12 19:37:05 2014 JenneUpdateSUSclipping removed from PRM oplev

I'm not happy with the beam position on that first lens, but since it's so crazy in the BS chamber, and the PRM oplev has something like 5 in-vac steering mirrors, I'm hesitant to suggest that we do anything about it until our next vent.  But we should definitely fix it.

  5709   Thu Oct 20 04:47:37 2011 kiwamuUpdateLSCclipping search round 1

[Koji / Kiwamu]

  We tried finding a possible clipping in the vertex part.

We couldn't find an obvious location of a clipping but found that the recycling gain depended on the horizontal translation of the input beam.

We need more quantitative examination and should be able to find a sweet spot, where the recycling gain is maximized.


(what we did)

  + locked the carrier-resonant PRMI.

  + with IR viewers we looked at the inside of ITMX, ITMY and BS chambers to find an obvious clipping.

    => found two suspicious bright places and both were in the ITMY chamber.

      (1) POY pick off mirror : looked like a small portion of a beam was horizontally clipped by the mirror mount but not 100% sure whether if it is the main beam or a stray beam.

      (2) The top of an OSEM cable connectors tower : although this is in the way of the SRC path and nothing to do with PRC.

 + Made a hypothesis that the POY mirror is clipping the main beam.

 + To reject/prove the hypothesis we shifted the translation of the incident beam horizontally such that more beam hits on the suspicious mirror

 + Realigned and relocked PRMI.

    => Indeed the recycling gain went down from 6 to 0.8 or so. This number roughly corresponds to a loss of about 50%.

         However the MICH fringe still showed a very nice contrast (i.e. the dark fringe was still very dark).

         Therefore our conclusion is that the POY mirror is most likely innocent.

  3368   Thu Aug 5 16:18:37 2010 AlastairUpdateGeneralclocks still not locked fully - hut removed

The rubidium clocks are still not quite locked together, though it is clear that the beat frequency has dropped a lot since yesterday.

I checked on the clocks and the 1pps sync light is on.  The clocks are really hot again though despite the gap left at the bottom of the igloo.  The side of the clocks were hot enough to not be touchable.

I made the executive decision that I would remove the hut just now.  We can let the clocks lock together and then put the hut back on just before measuring.  This way the hut will isolate from temperature fluctuations during the measurement but it won't be running at the hotter equilibrium temperature.  I hope that the temperature won't change too much during the measurement if we put the hut back on.

RA: Attachment deleted because it was in Postscript format. Also not allowed here are the Stone Tablet and Cave Painting formats.

  3377   Fri Aug 6 16:20:08 2010 ranaUpdateGeneralclocks still not locked fully - phase shifted

 I tried to get the clocks to be closer to 90 deg for the relative phase by adding some cable length to one of the lines, but they are still wandering too much. We need to use the serial interface and up the gain in their 1PPS locking loops.

Attachment 1: Untitled.pdf
  5613   Tue Oct 4 15:43:10 2011 KojiUpdateIOOclosed the shutter before the MC

The shutter before the MC was closed at 3:30 as I started working on the RFAM.

MC REFL (INLOCK): 0.6~0.7
MC TRANS: 50000~52000

  5617   Tue Oct 4 19:06:46 2011 KojiUpdateIOOclosed the shutter before the MC

Finished the work at 6:30

MC REFL (INLOCK): 0.50-0.52
MC TRANS: 54400~547000

RFAM level

Before the work: -48.5dBm for 1.07VDC (both 50Ohm terminated)

Right after the work: -80dBm for 0.896VDC (both 50Ohm terminated)
10min after:   -70dBm
1hour after:   -65dBm
3hours after: -62dBm
1day after (Oct 5, 20:00):    -62.5dBm
2days after (Oct 6, 23:20): -72.5dBm
3 days after (Oct 7, 21:00): -57.8dBm


The shutter before the MC was closed at 3:30 as I started working on the RFAM.

MC REFL (INLOCK): 0.6~0.7
MC TRANS: 50000~52000


  12705   Thu Jan 12 10:14:49 2017 SteveHowTosafetyclosing a door

The door was not locked this morning.

Please do not use this door if you can not close it!

Last person leaving the lab should check that the latch is cut by the strike plate.

Attachment 1: odc.jpg
Attachment 2: howtocloseadoor.jpg
  12706   Thu Jan 12 13:43:02 2017 ranaHowTosafetyclosing a door

This is one of those unsolved door lock acquisition problems. Its been happening for years.

Please ask facilities to increase the strength of the door tensioner so that it closes with more force.

  12707   Thu Jan 12 13:45:58 2017 SteveHowTosafetyclosing a door

It was requested this morning.


This is one of those unsolved door lock acquisition problems. Its been happening for years.

Please ask facilities to increase the strength of the door tensioner so that it closes with more force.


  8785   Fri Jun 28 14:57:15 2013 SteveUpdateGeneralclosing lab doors

I found the south end emergency doors not latched completely. There was a ~ 3/8" vertical gap from top to bottom.

Please pull or push  doors harder if they not catch fully.

  6072   Mon Dec 5 19:21:55 2011 kiwamuUpdateLSCcoarse beat note signal : ADC limited above 30 Hz

The signal observed by the coarse frequency discriminator was actually dominated by the ADC noise above 30 Hz.

It means that once increasing the UGF more than 30 Hz the servo will feed the ADC noise to the test mass and shake it unnecessarily.

I guess this could be one of the reasons of the unstable behavior in the Y end PDH lock (#6071).

(But still it doesn't fully explain the instability).


 To improve the situation I am going to do the following actions:

   (1) Installation of a whitening filter (probably use of SR560s)

   (2) Redesign of the servo filter


Here is a brief noise budget of the coarse sensor.


Gray curve: free running noise when no servo is applied

Green curve : in-loop noise when the ALS loop is closed with the coarse frequency-discriminator. The UGF was at 30 Hz.

Red curve : ADC noise of the coarse discriminator

Quote from #6071

 So far I still kept failing to increase the UGF of the ALS servo for some reason (see #6024).

  3850   Wed Nov 3 02:37:39 2010 yutaSummaryGreen Lockingcoarse locked green beat frequency

(Kiwamu, Yuta)

We succeeded in coarse locking the green beat frequency, using a frequency counter and feeding back the signal to the X-end laser temperature.

  beat note -> RF PD -> SHP-25 -> SLP-100 -> ZFL-1000LN -> ZFL-1000LN -> ZFL-500LN -> ZFRSC-42 -> SBP-70 -> ZFRSC-42 -> SR620 -> c1psl(C1:PSL-126MOPA_126MON)
  c1auxey(C1:LSC-EX_GREENLASER_TEMP) -> X-end laser temp

  The frequency counter SR620 converts the beat frequency to voltage.
  We added some filters (SHP-25, SLP-100, SBP-70). Otherwise, SR620 doesn't count the frequency correctly.

What we did:

  1. Getting green beat note again
     Set PSL laser temp to 31.81 °C and X-end laser temp to 37.89 °C.
     Set PPKTP crystal temp to 37.6 °C, which maximizes output green beam power.

  2. ADC channel and DAC channel
     Disconnected one channel going into VME-3123 (at 1X1) and used c1psl's C1:PSL-126MOPA_126MON as ADC channel for the output from SR-620
     Made a new DAC channel on c1auxey named C1:LSC-EX_GREENLASER_TEMP, and disconnected one channel from VME-4116 (at 1X9) to use it as DAC channel for X-end laser temperature control.

  3. Coarse lock by ezcaservo
        ezcaservo C1:PSL-126MOPA_126MON -s 150 -g -0.0001 C1:LSC-EX_GREENLASER_TEMP
     "-s" option is a set value. The command locks C1:PSL-126MOPA_126MON to 150 (in counts), using 0Hz pole integrator.

  The beat frequency locked on to ~77MHz. The frequency fluctuation of the beat note during the servo is ~3MHz with ~10sec timescale.
  VCO has  ~+/-5MHz range, so this coarse locking meets the requirement.

  Here's a plot of the error signal and feed back signal;

  3851   Wed Nov 3 03:00:47 2010 KojiSummaryGreen Lockingcoarse locked green beat frequency

Wow! Great guys!!

Can I expect to see the spectra of the frequency counter output with and without the servo?

RA: I think the SBP-70 is a bad idea. It limits the capture range. So does the SHP-25. You should instead just use a DC-block; the SR620 should work from 1-200 MHz with no problems.

Also, we have to figure out a better solution for the DAC at the ends: we cannot steal the QPD gain slider in the long run and the 4116 DAC at the ends has all 8 channels used up. Should we get the purple box for testing or should we try to use the fast DAC in the EX IO chassis as the actuator?

  6779   Thu Jun 7 05:39:41 2012 yutaUpdateGreen Lockingcoarsely stabilized Y arm length with ALS

I coarsely stabilized Y arm length to off resonance point for IR using ALS.
Currently, ASL servo loop is unstable and oscillates so much that I can't hold the length to the resonance point.
We need more investigation on the servo loop before doing the mode scan.

Below is a snapshot of ALS medm screens and time series data of the error signal for ALS coarse loop (C1:ALS-BEATY_COARSE_I_ERR) and IR transmission for the Y arm (C1:LSC-TRY_OUT) when I turned the servo on.



  I took off amplifiers right after the beat PD on PSL table.
  Also, I reverted the gain change Jenne made last night (elog #6750), because they no longer show overload lights.

  9087   Wed Aug 28 23:09:55 2013 jamieConfigurationCDScode to generate host IPC graph
Attachment 1: hosts.png
Attachment 2: 40m-ipcs-graph.py
#!/usr/bin/env python

# ipc connections: (from, to, number)
ipcs = [
    ('c1scx', 'c1lsc', 1),
    ('c1scy', 'c1lsc', 1),
    ('c1oaf', 'c1lsc', 8),

    ('c1scx', 'c1ass', 1),
    ('c1scy', 'c1ass', 1),
... 96 more lines ...
  13140   Tue Jul 25 00:03:01 2017 ranaOmnistructureTreasurecoffee pot lid

I have recommissioned the Zojirushi coffee pot lid. You may, once again, align the dots in order to make the carafe pourable.


The Zojirushi lid is a two part mechanism:

  1. The top part of the lid must be removed for cleaning.
  2. When replacing the lid the two components must be aligned to < 3 mrad precision so that the "teeth" are able to land in the groove.
  3. There is a 4-fold degeneracy in this process. To break the degeneracy, align the dot on top with the spout gap (visible from the bottom view).
  4. After proper alignment and mating, the two parts should snap together and the relative alignment wiggle available should be < 2 mrad.
  5. After screwing the two-piece lid onto the carafe, ensure that the 2 dots are separated by < 170 deg in the closed position.
  5816   Fri Nov 4 21:52:58 2011 DenUpdateAdaptive Filteringcoherence

[Mirko, Den]

We still think about the coherence between seismic noise and mode cleaner length. We beleive that

1. Below ~0.1 Hz tilt affects on the seismometers as was simulated http://nodus.ligo.caltech.edu:8080/40m/5777

2. From 0.1 to 1 Hz is an interesting region. We try to figure out why we do not see any coherence here. Tilt does not seem to dominate.

At 1 Hz coherence might be lost because of the sharp resonance. For example, if the mirror is suspended to the platform by wires with f = 1 Hz and Q = 1000, then the coherence between platform motion and mirror motion will be lost as shown on the figure below.


For this reason we tried to "help" to the adaptive filter to guess transfer function between the ground motion and mirror motion by multiplying seimometer signal by the platform -> mirror transfer function. As we do not know exactly eigen frequency and Q of the wires, we did a parametric simulation as shown on the figure below


The maximum coherence that we could achieve with treak was 0.074 compared to 0.056 without. This was achieved at f=1.0011 Hz but with surprisingly high Q = 330. And though this did not help, we should keep in mind the tecnique of "helping" the adaptive filter to guess the transfer function if we partly know it.

Another unexpected thing is that we see come coherence between gur1_x and mode cleaner WFS pitch signal at frequencies 0.1 - 1 Hz




 From this we can suggest that either mode MC_F channel does not completely reflect the mc length at low frequencies or WFS2 shows weard signal.

  5825   Sun Nov 6 21:09:03 2011 ranaUpdateAdaptive Filteringcoherence


[Mirko, Den]

We still think about the coherence between seismic noise and mode cleaner length. We beleive that

The 'helping' trick is a good one: we should use our best guess for the stackTF and the pendulumTF and put it into the IIR filter bank to pre-filter the seismometer signals before they get to the MC mirrors. Also should remember that the signal we send to suppress the seismic motion is applied to the pendulum as a force, not a displacement.

The 3 Hz fast cutoff in the MC_F signal is a good clue. It means that at low frequencies, perhaps the noise source is going through a digital 3 Hz elliptic or Chebychev filter.

  6065   Sat Dec 3 18:29:20 2011 DenUpdateAdaptive Filteringcoherence

I've looked through the coherence between the MC length and seismometers after the if-statement problem was fixed. Coherence improved for all seismometers but is still not 1. It is possible that contribution from X, Y, Z directions split the coherence between them but at ~0.2-03 Hz we do not see much coherence for all these directions.


I looked at the coherence between MC2 OSEM signal and MC_F when the AUTO LOCKER is ON and OFF. I thought that we'll ses the same coherence for both regimes as laser is locker to the MC length. However, I figured out the coherence is worse when AUTO LOCKER is ON at frequencies 0.2-0.3 Hz.


The first idea that comes to mind is that when feedback to the laser is provided, the pressure to the mirrors from the laser beam is changed.

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