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ID Date Author Typeup Category Subject
  4937   Tue Jul 5 08:32:38 2011 steveUpdatePEMbad air quality in the lab

The fireworks of yesterday showing up in the lab. Pasadena out side air 6.6 million  cfm for 0.3 micron particles  and 1.5 million cfm for 0.5 micron size.

  4938   Tue Jul 5 13:35:56 2011 steveUpdateSUSPRM damping restored

The PRM sus damping was restored. It's side rms motion came down from 35 to 4 mV immediately.      Lab   air quality is back to normal.


  4939   Tue Jul 5 16:09:54 2011 kiwamuUpdateABSLsome photos for ABSL setup

Here I show two photos of the latest ABSL (ABSolute Length measurement) setup.


Figure.1 : A picture of the ABSL setup on the AP table.

  The setup has been a little bit modified from the before (#4923).

 As I said on the entry #4923, the way of sampling the ABSL laser wasn't so good because the beam, which didn't go through the faraday, was sampled.

In this latest configuration the laser is sampled after the faraday with a 90% beam splitter.

The transmitted light from the 90% BS (written in pink) is sent to the PSL table through the access tube which connects the AP and PSL table .



FIgure.2: A picture of the ABSL setup on the PSL table.

 The 10% sampled beam ( pink beam in the picture) eventually comes to the PSL table via the access tube (the hole on the left hand side of the picture).

Then the ABSL beam goes through a mode matching telescope, which consists of a combination of a concave and a convex lens.

The PSL laser (red line in the picture) is sampled from a point after the doubling crystal.

The beam is combined at a 50 % BS, which has been setup for several purposes( see for example #3759 and #4339 ) .

A fast response PD (~1 GHz) is used for the beat-note detection.

  4940   Tue Jul 5 17:38:46 2011 kiwamuUpdateABSLABSL laser frequency-locked

In this past weekend the ABSL laser was successfully frequency-locked to the PSL laser with a frequency offset of about 100 MHz.

In the current setup a mixer-based frequency discriminator is used for detection of the beat-note frequency.


Setup for frequency locking

 The diagram below shows the setup for the frequency locking.


  According to a brief check of the loop oscillation it implies that the UGF is around 40 kHz.
Of course I will measure the open-loop over a wide frequency range at some point.
The lock was quite robust and it was able to stay locked for more than an hour as far as I observed.
(Beat-note detection and its amplification)
 The fast RFPD, which is standing on the PSL table to detect the beat-note (see the picture on #4939), showed the signal level of -16 dBm.
Then the signal goes through the RF amplifier stage to have an appropriate power level at the mixer in the frequency detection stage.
Before the signal goes into the amp. stage I put a power splitter so that I can see a signal on a spectrum analyzer.
(Frequency detection)
 In the mixer-based frequency discriminator, the length difference between two coax. cable was chosen to be 1 m.
This length difference gives us a zero cross point (operation point) of ~100 MHz and linear range of ~ +/-100MHz, which can sufficiently cover the FSR of PRC: 22MHz.
(Control filter)
 After the signal goes through the freq. discriminator, a low noise amplifier, ITHACO 1201 was installed as a control filter.
The reason I chose ITHACO 1201 was that it has a larger output range than that of SR560.
ITHACO 1201 can go to +/- 15V, which means the ABSL laser should be able to track the frequency by about +/- 65 MHz without a thermal actuation.
Right now a single pole was put at 1 Hz for an easy lock.
The output from 1201 goes directly to the laser PZT, whose input is on the front panel of the laser controller.


Temperature setpoints

 During the work I found three temperature points, where we can observe the beat-note signal within a bandwidth of 1 GHz.
 Here is a summary of the temperature set points :
    PSL temperature = 31.71 deg
    ABSL temperature = 44.19 deg (not good),
                                       47.25 deg (chosen to be nominal set point),
                                       50. 23 deg
 The first one (44.19 deg) wasn't good because changing the temperature of the ABSL laser also changes the amplitude of the beat-note significantly.
In a worst case the signal completely disappeared when the ABSL laser was at a certain temperature close to 44.19 deg.
The other two temperature points seemed good. I eventually chose the second one (47.25 deg) for the nominal set point.
Note that the current readout has been 1.81 A on the laser controller.
  4941   Tue Jul 5 18:57:10 2011 JamieUpdateSUSMore normalization of all sus controllers

Based on Rana's comment I have gone through and moved all of the corner frequencies for the high pass filters in the SUS damping controllers to 30 Hz.  I did this for all optics (MC1, MC1, MC3, BS, ITMX, ITMY, PRM, SRM, ETMX, ETMY) all degrees of freedom (POS, PIT, YAW, SIDE).

Rana also suggested I turn off all of the BounceRoll filters until we get a chance to tune those individually for all the suspensions.

Finally, I normalized the MC SUSXXX filter banks to look just like all the other suspensions.

All damping filter banks for all degrees of freedom for all single suspensions should all be the same now (modulo the differences in the BounceRoll filters, which are now turned off).

  4942   Tue Jul 5 21:26:51 2011 ranaUpdateSUSMore normalization of all sus controllers

This is getting closer, but with the whitening left OFF and the cts2um filter also OFF, none of the suspensions are working correctly. I'm shutting down all the watchdogs until someone gets around to setting the damping gains and filters correctly.

I'm attaching a screenshot of some of the problems I see so far with MC3.

I'm going to try to get the MC suspensions working OK for tonight so that we can use them for the PRMI locking work.

Update #1: None of the MC SUS DAQ channels are found by dataviewer....SUS debugging speed reduced by 10x.  Tue Jul 05 21:38:17 2011

Update #2: POS/PIT/YAW BIAS sliders now seem to work, but are ~1000x too weak to do anything.   Tue Jul 05 21:41:38 2011


  4943   Wed Jul 6 02:12:36 2011 kiwamuUpdateSUSRe : More normalization of all sus controllers

[Jenne / Rana/ Kiwamu]

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

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

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

Quote from #4942

This is getting closer, but with the whitening left OFF and the cts2um filter also OFF, none of the suspensions are working correctly.


  4944   Wed Jul 6 10:35:35 2011 JamieUpdateSUSRe : More normalization of all sus controllers


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

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


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

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

  4945   Wed Jul 6 11:45:20 2011 JamieUpdateSUSMore normalization of all sus controllers


I'm attaching a screenshot of some of the problems I see so far with MC3.

I tried to fix all of the problems that I could identify in this screen shot:

  • Fixed the TO_COIL output filter matrix screen to correctly point to the matrix element filter screens (all SUS)
  • Removed MCL sections from SUS_XXX_POSITION screens, except for MC2.  I also modified the _POSITION screens for the ETMs to refer to ALS instead of MCL.
  • Zeroed out all of the lockin gains in the TO_COIL matrices (MC SUS)
  • Made sure all whitening filter were ON (all SUS)
  • Made sure all cts2um calibration filters were on (all SUS)
  • Made sure all oplev servos were on (all SUS)
  4946   Wed Jul 6 15:32:32 2011 JamieUpdateSUSRe : More normalization of all sus controllers

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

  4947   Wed Jul 6 16:44:37 2011 steve, kiwamuUpdateSUSBS oplev spectra

Healthy BS oplev

  4948   Wed Jul 6 18:15:26 2011 kiwamuUpdateSUSRe: BS oplev spectra

[Steve / Kiwamu]


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

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

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

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

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


Measurement :

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

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

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

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

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

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

Quote from #4947

Healthy BS oplev

  4949   Wed Jul 6 23:03:57 2011 kiwamuUpdateLSCmodified locking scripts

[Jenne / Kiwamu]

 Last night we modified the locking scripts, that were called from C1IFO_CONFIGURE.adl, to adapt them to the new "PRCL" and "SRCL" convention.

So far they work fine and quitted dumping some error messages about inexistence of these channel names.

  P.S. The locking scripts have been summarized on the 40m wiki

Quote from #4912

- Now the power and signal recycling cavity lengths are named "PRCL" and "SRCL" in stead of three letter names without "L".

We should change the locking script to accomodate these changes.

  4954   Thu Jul 7 14:27:16 2011 SureshUpdateIOOsomething wrong ? : Power incident on REFL11 and REFL55

Just tying up a loose end.  The next day Kiwamu and I checked to see what the trouble was.  We concluded that the PRM had not moved during my measurement though I had 'Misaligned' it from the medm screen.  So all the power levels measured here were with the PRM aligned.  The power level change was subsequently measured and e-logged


The measured change in the REFL DC power with and without PRM aligned seems unacceptably small.  Something wrong ?

The difference in the power with and without PRM aligned should be more than a factor of 300.

         [difference in power] = [single bounce from PRM] / [two times of transmission through PRM ]

                                          = (1-T) / T^2 ~ 310,

where T is the transmissivity of PRM and T = 5.5% is assumed in the calculation.

Also the reflectivity of MICH is assumed to be 1 for simplicity.

Quote from #4894

We now have (with the PRM misaligned):

REFL11:  Power incident = 7.60 mW ;  DC out = 0.330 V  => efficiency = 0.87 A/W

REFL55:  Power incident = 23 mW ;  DC out = 0.850 V  => efficiency = 0.74 A/W

and with the PRM aligned::

REFL11:  DC out = 0.35 V  => 8 mW is incident

REFL55: DC out = 0.975 V  => 26 mW is incident



  4957   Fri Jul 8 19:50:19 2011 SureshUpdateRF SystemLSC rack channel assignment

[Jamie, Suresh]

   We looked at the ADC channel assignments in the LSC model and wanted to make sure that the LSC rack wiring and the LSC model are in agreement with each other.  So the plan is to wire the rack as shown below.  I will also post this file on svn so that we can keep it updated in case there are changes.




  4958   Fri Jul 8 20:50:49 2011 sonaliUpdateGreen LockingPower of the AUX laser increased.

The ETMY laser was operating at 1.5 A current and 197 mW power.

For the efficient frequency doubling of the AUX  laser beam at the ETMY table, a higher power is required.

Steve and I changed the current level of the laser from 1.5 A to 2.1 A in steps of 0.1 A and noted the corresponding power output . The graph is attached here.

The laser has been set to current 1.8 Amperes. At this current, the power of the output beam just near the laser output is measured to be 390 mW.

The power of the beam which is being coupled into the optical fibre is measured to be between 159 mW to 164 mW (The power meter was showing fluctuating readings).

The power out of the beam coming out of the fibre far-end at the PSL table is measured to be 72 mW. Here, I have attached a picture of the beam paths of the ETMY table with the beams labelled with their respective powers.

Next we are going to adjust the green alignment on the ETMY and then measure the power of the beam.

At the output end of the fibre on the PSL, a power meter has been put to dump the beam for now as well as to help with the alignment at the ETMY table.

  4961   Tue Jul 12 10:18:05 2011 JamieUpdateCDSC1:DAQ-FB0_C1???_STATUS indicators red, restored after controller restarts

Yesterday I found the C1:DAQ-FB0_C1???_STATUS lights to be red for the SUS, MCS, SCX, and SCY controllers.  I know this has something to do with model communication with the framebuilder, but I unfortunately don't remember exactly what it is.  I decided to try restarting the affected models to see if that cleared up the problem.  It did.  After restarting c1scx, c1scy, c1sus, and c1mcs everything came back up green.

We need some better documentation about what all of these status indicators mean.

  4962   Tue Jul 12 11:52:54 2011 Jamie, SureshUpdateLSCLSC model updates

The LSC model has been updated:

Binary outputs to control whitening filter switching

We now take the filter state bit from the first filter bank in all RF PD I/Q filter banks (AS55_I, REFL11_Q, etc) as the controls for the binary analog whitening switching on the RF PD I/Q inputs. The RF_PD part was also modified to output this control bit. The bits from the individual PDs are then combined into the various words that are written to the Contec BO part.

Channel mapping updated/fixed to reflect wiring specification

Yesterday Suresh posted an updated LSC wiring diagram, with correct channel assignments for the RF PD I/Q and DC inputs.  Upon inspection of the physical hardware we found that some of LSC the wiring was incorrect, with I/Q channels swapped, and some of the PDs in the wrong channels.  We went through and fixed the physical wiring to reflect the diagram.  This almost certainly will affect the EPICS settings for some of the input channels, such as offsets and RD rotations.  We should therefore go through all of the RF inputs and make sure everything is kosher.

I also fixed all of the wiring in the LSC model to also reflect the diagram.

Once this was all done, I rebuilt and restarted the LSC model, and confirmed that the anti-whitening filter banks in the PD input filter modules were indeed switching the correct bits.  I'll next put together a script to confirm that the LSC PD whitening is switching as it should.


  4963   Tue Jul 12 17:30:24 2011 steve,UpdateSUSBS oplev spectra


Healthy BS oplev

 I repeated the BS oplev spectrum today and I do not understand why it does look different. I did it as Kiwamu describes it in entry#4948  The oplev servo was left ON!

  4964   Wed Jul 13 12:24:46 2011 NicoleUpdateSUSWeekly Update
This week, I have been working on the photosensor circuit box.  This photosensor box will contain the current-stabilizing power supply and
voltage readout for the two photosensors I plan to build.
Suresh helped to walk me through the design of the photosensor circuit (image below) so I now understand how the circuit works.
Jaimie helped me to reorganize the original circuit layout I had to make it easier to follow. I have now redone half of the circuit (enough for one LED and photodiode pair). I still need to put in the voltage-regulators to provide the + and - 15 V neeCto power the op-amps but I will do that after testing the circuit.

In order to test this preliminary circuit, I need to build the photosensor heads.  Yesterday, Suresh helped me to open one of the professionally-build photosensors in the lab to understand how to arrange my photosensor heads. I now understand that I need to rigidly-mount the PCB to photosensor head box. I plan to use the PCB below. It will be sufficient for the lower-frequency range (below 10Hz) that I am interested in. 


 I would like to use a metal box like the one below to make each photosensor head. I looked in the lab last night for similar boxes but could not find one. Does anyone know where I can find a similar metal box?



I am now working on accelerometer. I am working on attaching these metal wires to the pins of the accelerometer so that I can use clip leads to power and extract voltage measurements from my circuit.


  4965   Thu Jul 14 02:32:11 2011 sonaliUpdateGreen LockingPower of the AUX laser increased.


The power of the beam which is being coupled into the optical fibre is measured to be between 159 mW to 164 mW (The power meter was showing fluctuating readings).

The power out of the beam coming out of the fibre far-end at the PSL table is measured to be 72 mW. Here, I have attached a picture of the beam paths of the ETMY table with the beams labelled with their respective powers.

 For the phase locking or beat note measuring we only need ~1 mW. Its a bad idea to send so much power into the fiber because of SBS and safety. The power should be lowered until the output at the PSL is < 2 mW. In terms of SNR, there's no advantage to use such high powers.

  4966   Thu Jul 14 09:38:50 2011 steve,UpdateSUSBS oplev spectra



Healthy BS oplev

 I repeated the BS oplev spectrum today and I do not understand why it does look different. I did it as Kiwamu describes it in entry#4948  The oplev servo was left ON!

 It is working today! Finally I repeated the BS spectra, that we did with Kiwamu last week

  4967   Thu Jul 14 15:27:08 2011 steve,UpdateSUSSUS oplev spectras




Healthy BS oplev

 I repeated the BS oplev spectrum today and I do not understand why it does look different. I did it as Kiwamu describes it in entry#4948  The oplev servo was left ON!

 It is working today! Finally I repeated the BS spectra, that we did with Kiwamu last week

 The optical levers were centered during these measurements  without the reference of locked cavities.  They have no reference value now.

SRM sus need some help. ITMX is showing pitch/yaw modes of the pendulum .....OSEM damping is weak?

  4972   Fri Jul 15 09:25:02 2011 ranaUpdateSUSSUS oplev spectras

In addition to the OL quadrants, you need to plot the OPLEV_PERROR and OPLEV_YERROR signals since these are the real signals we use for finding the mirror motion. If they're not in the Dataviewer, Jamie should add them as 256 Hz DAQ channels (using these names so that we have the continuity with the past). These DAQ channels correspond to the IN1 channels for the OL filter banks.

Also JPG are banned from the elog - you should put all of the plots into a single, multipage PDF file in honor of the new Wagonga.

  4973   Fri Jul 15 13:48:56 2011 sonaliUpdateGreen LockingPower of the AUX laser increased.



The power of the beam which is being coupled into the optical fibre is measured to be between 159 mW to 164 mW (The power meter was showing fluctuating readings).

The power out of the beam coming out of the fibre far-end at the PSL table is measured to be 72 mW. Here, I have attached a picture of the beam paths of the ETMY table with the beams labelled with their respective powers.

 For the phase locking or beat note measuring we only need ~1 mW. Its a bad idea to send so much power into the fiber because of SBS and safety. The power should be lowered until the output at the PSL is < 2 mW. In terms of SNR, there's no advantage to use such high powers.


Well,the plan is to put in  a neutral density filter in the beam path before it enters the fibre. But before I could do that, I set up the camera on the PSL table to look at the fiber output . I will need it while I realign the  beam after putting in the Neutral Density Filter. I have attached the ETMY layout with the Neutral Density filter in place herewith.

  4976   Fri Jul 15 16:14:00 2011 steveUpdateSUSBS oplev error signal spectra
  4977   Fri Jul 15 17:42:21 2011 SonaliUpdateGreen LockingPSL layout for superposition of the PSL,ETMX and ETMY beams.

The fibres carrying the beams from the ETMX as well as the ETMY have been routed to the PSL table now.

A part of the PSL beam has to be superposed on the fibre-outputs to obtain a beat signal. We have located a stray beam on the PSL(which is currently being dumped) which we plan to redirect for the same. The layout of the plan is attached herewith.

  4980   Sun Jul 17 18:23:23 2011 JenneUpdatePSLFound the PMC unlocked

It was unlocked since ~4:30am.  No idea why.  It's relocked so I can try round N of measuring the PRC length.

  4982   Mon Jul 18 14:39:53 2011 JenneUpdateComputersLSC PD chans acquired

There's too much tromping around, so I'm not going to actually measure PRC length right now, but I did set some channels to be acquired (POPDC, POXDC, POYDC) in addition to ASDC which was already acquired, so that I can look at the resonance fringes when I sweep the ABSL laser (hopefully later tonight....)

  4983   Mon Jul 18 15:51:04 2011 steveUpdateSUSETMY spectra of oplev error signal
  4984   Mon Jul 18 20:59:19 2011 JenneUpdateLSCBig ol' mess

[Jamie, Jenne]

We decided to take on the deceptively easy-sounding task of checking that the LSC whitening switching was happening as anticipated.  We hoped to discover that when we clicked the "unwhitening" switches in FM1 of the LSC PDs, we would see the analog whitening turn on and off for the matching channel.  That is what is supposed to happen.

Tragically, it is instead one big giant crazy disaster of a mess.

What we did:

Made a 24tapus (octopus like last time, except more...), with a 50kOhm resistor as our white noise source (instead of using a DAC channel and AWG). 

We plugged our 24tapus into the 3 of 4 whitening boards on the LSC rack that are currently in use.  One of the boards just has 8 terminators on the input, so we left that one alone for now. 

We put the whitening gains to 0dB so that all the channels looked the same. 

We looked at the PD _IN1 channels in DTT, and monitored which signals had whitening switching when we clicked the "unwhitening" buttons on the PD filter banks. 

So far, we can find no rhyme or reason as to why some of the channels work (click unwhite on that PD, see that signal have whitening switching), and others don't.  Some channels we just can't get to switch no matter what, others are just mis-mapped.  There is no discernible pattern.

What we think (so far) is going on:

All of the cables from the PD demod boards are going to the Whitening board inputs, exactly as in Suresh's Diagram.  The only difference is that Refl33, AS165 and Refl165 demod boards don't exist in the rack at this time. 

The Whitening and AA boards in Suresh's Diagram labeled 0-7 are connected to Binary Output channels 0-7. This is a good thing.

The Whitening and AA boards in the diagram labeled 8-15 are connected to Binary Output channels 24-31. This is not so awesome.

This is all we are confident about at this time.

Next steps:

We are hoping that Ben has a secret stash (or can tell us who would) of LSC rack wiring diagrams.  We would like to find out, without the pain of tracing wires and cables by hand, how the Binary I/O information gets through the cross-connect on the LSC rack up to the whitening boards. 

We are leaving the 24tapus in place for now, so that we can carry on tomorrow, either with a wiring diagram in hand, or carefully tracing cables. 

  4986   Mon Jul 18 22:26:43 2011 NicoleUpdateSAFETYPainful Voltage Regulator and Circuit-Testing Lessons

Today I learned some important circuit-building lessons while testing my photosensor circuit box (i.e. how NOT to test a circuit and, conversely, things that should be done instead). 

I blew my first circuit today. The victim is in the photo below (bottom 7805 voltage regulator). The plastic covering fell off after I removed the fried regulator.  After checking various components, I figured out that I blew the circuit because I had forgotten to ground the regulator.  Although this was very unfortunate, I did make an important discovery. While testing the voltage output of the 7805 voltage regulator (I put a new one), I discovered that contrary to the claims of the datasheet, an input voltage of 5V will not produce a steady 5V supply. I found that at 5V, my regulator was only producing 4.117 V. I was using a 5 V supply because I wanted to use only 1 power supply (I was using a two-channel power supply that had a fixed 5V output to produce the +15, -15, ground, and 5 V I need for my photosensor circuit box).  After seeing this, I got a second power supply and am now using 10V to as an input for the regulator to produce 4.961V. I found that from a voltage range of 10V to 15 V, the regulator produced a steady  4.961 V supply. I have decided to use 10V as an input. My newly-grounded voltage regulator did not smoke or get hot at 10V.

After several more debugging trials (my LED was still not lighting up, according to the infared viewer), I learned another painful lesson. I learned DO NOT USE CLIP LEADS TO TEST CIRCUITS!!!! Initally, I was powering my circuit and making all of my connections between the photosensor head (2 photodiodes and 1 LED) with clip leads. This was a BAD IDEA BECAUSE CLIP LEADS ARE UNSTABLE AND IT IS VERY EASY TO SHORT A CIRCUIT IF THEY ACCIDENTALLY TOUCH! I did not realize this important lesson until my photosensor circuit was once again burning. Confused as to why my circuit was once again burning, I foolishly touched the voltage regulator. As you can see on the top voltage regulator in the photo below, my finger left its mark on the smoldering voltage regulator. As you cannot see the wincing on my face as I try to type this long elog, I will painfully type that the voltage regulator left its own mark on my finger (an ugly sore little welt).  Suresh has taught me a valuable lesson: WHEN DEALING WITH SOMETHING OF QUESTIONABLE/UNKNOWN TEMPERATURE, USE YOUR NOSE, NOT YOUR FINGER TO DETERMINE IF THAT COMPONENT IS HOT!!!! 



To make my circuit-testing safer, upon the suggestion of Suresh, I have since removed the clip leads and inserted a 12 pin IDC component (pictured below). There are 12 pins for the 6 inputs I will get from each of the 2 photosensor heads. I have requested orders for a 16 pin IDC connector, 15 pin Dsub male part, 15 pin Dsub feed-thru, 9 pin Dsub male part (2), and 9 pin Dsub feed-thru (2). After receiving these components, I should be able to safely test my circuit.


 In the meanwhile, I can explore SimMechanics and try to figure out how to use the accelerometer

  4987   Tue Jul 19 09:19:14 2011 steveUpdateSUSPRM damping restored

The PRM watchdogs were tripped. The side was kicked up to 180mV Damping was restored.

  4988   Tue Jul 19 10:18:24 2011 ranaUpdateLSCBig ol' mess

Remember, as per our marker board conversation, that the resistor noise as excitation method only works if the gain of all of the channels is set to something high (like 45 dB).

At 0 dB, the resistor noise is only 30 nV/rHz, whereas the ADC noise is more like 10000 nV/rHz...

  4989   Tue Jul 19 10:54:14 2011 steveUpdateGenerallarge sensor card can not be found

Please return sensor card to  laser log box so others can use it. We have only one larger fluorescent sensor card.

  4990   Tue Jul 19 13:45:22 2011 SureshUpdateSAFETYPainful Voltage Regulator and Circuit-Testing Lessons

There is should be a few IDC connectors in the lab (and some ribbon cable) using which you can proceed with the testing of the circuit, if you prefer.  If not we can get them from our ever helpful electronics division at Downs.  In any case there is no need to lose time waiting for parts to arrive.


  4991   Tue Jul 19 20:36:08 2011 ranaUpdateComputersVirtualBox + Windows 7 on rossa

I installed Virtual Box on rossa. Then I put Windows 7 in there and am now installing Altium.

You can run Windows on rossa by just clicking Applications -> System Tools -> Virtual Box.

  4992   Tue Jul 19 21:05:55 2011 haixingUpdateDAQchoose the right relay

Rana and I are working on the AA/AI circuit for Cymac. We need relays to bypass certain paths in the circuit, and we just found a nice website
explaining how to choose the right relay:


This piece of information could be useful for others.

  4993   Tue Jul 19 23:39:11 2011 Jamie, JenneUpdateLSCMajor overhaul of LSC rack; binary switching of whitening filters now working

Yesterday we started going through the LSC binary whitening switching to make sure the new switching control in the LSC model was working.  Jenne and I hooked up a fancy home-brew white noise generator [0] into all of the LSC whitening filter inputs and started switching the whitening filters to see what would happen.  We found that some of the channels were switching, but the majority were not, or worse yet switching the wrong channels.  Upon closer inspection, and after finally finding the LSC wiring schematic, we found that the LSC rack cross-connect/back-plane cabling was pretty much a complete mess, and didn't at all correspond to the channel layout in Suresh's diagram.

Given that the back-plane wiring had to be almost completely redone, we decided to completely redo the LSC electronics layout, to be a little more self-consistent and to use the given space more efficiently.  We'll post an updated electronics drawing soon.  The LSC model was also updated to reflect the new layout.

We then went through and verified that all of the whitening switching was working with the new layout.  As described previously, the first filter in the PD input filter bank is used to control the switching.  We did indeed verify that all the switching is working, but we noticed that switching logic was inverted, such that the whitening filter engaged when the filter was turned off.  This was fixed in the model and all the switching logic was verified to be working as expected.

Everything has now been hooked back up, but we need to verify that we're getting all of the PD demodulated RF and DC outputs as expected.  We need to check the RF phases, as some of the RF cable lengths have changed.

[0] a 50k resistor



  4994   Wed Jul 20 06:17:04 2011 SureshUpdateGreen LockingY-end green laser power issues

The Y-end green beam power is 0.47 mW.

While aligning the Y-end aux laser light into the fiber we noticed that the green power out of the doubling crystal was in microwatts.  I checked to see what was the trouble and found that the oven was cold as the temperature controller had been disabled.  I enabled it and scanned the temperature to maximise the green output.  Yet the power is less than 10% of that at the X end (7mW).

To verify I checked the power of various beams on the Y-end table.  They are listed below in the picture


The green beam power is proportional to the square of the IR incident power and this explains the drop in green power by a factor of (210/730)^2  thus making 7 mW -->  0.5 mW.  However we may be able to double the power at the Y-arm oven if the uncoated lenses in the IR path are exchaned for coated ones. 


The green beam injection into the Y-arm cavity also needs to be cleaned up as noted here.  As seen in the picture below two of the mirrors which launch the beam into the arm cavity need to be fixed as well.


  4995   Wed Jul 20 06:36:39 2011 SureshUpdateIOOWFS1 and 2 gains

Gains of individual quadrants in both the WFS

As a simple check of the gains on all the quadrants I hooked up the AM (Jenne) laser to put FM modulated light on to the WFS heads and observed the FM modulation frequency , 105 Hz, show up on a power spectrum of the RF outputs.   The plots below show the peak at 105Hz in all the quadrants.




However I should have put in AM modulation rather FM modulation.  I will do that using the digital system today.  The first version above was done wth a Marconi driving the AM laser modulation.



  4996   Wed Jul 20 06:52:01 2011 SureshUpdateLSCABSL - PSL beat lock

The ABSL locking setup to the PSL is down. 

According the plan, I started to use the IR beam dumped after the doubling crystal for the IR beat lock (Sonali's project).  The beat lock was disturbed when I shifted some clamps to make way for a few mirrors.  So I set about fixing the beat lock.  I reobtained the lock but noticed that the net beam power reaching the Newfocus 1611 detector was around 15mW.  10mW from the ABSL and 5mW from PSL.

This is much too high as the maximum allowed on 1611 is 2mW. 

I therefore started to adjust the power levels by using  Y1-1064-45S mirrors at non-45 deg angles.  However Rana pointed out that this would lead to amplitude noise due to the mirror vibrations.  I then switched to using beam splitters as pick offs.   This is better than using neutral density filters since the back scatter is lower this way.

David wanted some of the ABSL beam for his SURF student.  So I changed the mirror after beam expanding telescope on the ABSL route to provide this power.  We also installed a pair of half wave plates and a PBS to allow us smooth power level control on this beam.

The beat lock setup is now down and needs to be completed for PRCL and SRCL measurements.



  4997   Wed Jul 20 10:10:19 2011 SonaliUpdateGreen LockingWeekly summary

 I finished wih the set-up at the ETMY table. Instead of the neutral Density Filter , I put in a mirror(Y1-1037-45S)  which is reflective for IR , so that only 1% of the light is incident on the fibre  as per Rana's suggestion.

Now, the power incident on the fibre is measured to be 6 mW and the power measured out of the fibre is 2.76 mW after the necessary alignments.

On the PSL able, I have routed the beam that is coming out of the back of the PMC(instead of the dumped light from the oven to prevent any light from reflecting back into the laser), to the area where I am putting the set-up for the superposition of the PSL and the ETMX and ETMY beams.

Today I will proceed with the layout.

  4998   Wed Jul 20 11:13:59 2011 Larisa ThorneUpdateelogI restarted the ELOG as it seemed to have crashed


  4999   Wed Jul 20 11:42:47 2011 Ishwita, ManuelUpdate Weekly summary
  • We gave a white-board presentation on derivation of formula for optimum Wiener filter coefficients and wrote a latex document for the same. relevant elog entry
  • We enjoyed drilling the cover of the AA board and fixing it.
  • The AA board was fixed on rack 1X7 with Jenne's help. relevant elog entry
  • We tried writing a simulation for the transfer function of the stacks in Matlab. Once we get some satisfying results, we will post it on the elog.
  • We started reading the book 'Digital Signal Processing - Alan V. Oppenheim / Ronald W. Schafer' and are still reading it. We also tried watching lecture videos on z-transform...
  5001   Wed Jul 20 14:42:34 2011 steveUpdateSUSoplev gains today

C1:SUS-ETMX_OLPIT_GAIN set to 1.0     OLYAW 1.0

                ETMY                                     -0.2                   -0.2

                ITMY                                        2.0                    -2.0

                ITMX                                        0.5                     0.5

                  BS                                          0.4                    -0.4

                PRM                                         0.5                    -0.7

                SRM                                         1.0                     1.0

Earlier today Rana and I made power spectra of ETMY_OPLEV_ERROR signals with servo on and off.

It was indicating that the servo is not doing anything. These gain values were not set since IFO rebuilt.

Valera's entries were searched also. He did not do such thing. Rana may know where it is in the elog if it happened.

  5002   Wed Jul 20 17:43:33 2011 sureshUpdateComputersrestarted the frame builder

I restarted the frame builder in the last 15mins. 

I was making a change to a DAC channel in the C1IOO model.

  5004   Wed Jul 20 19:24:12 2011 ranaUpdateSUSoplev gains today

I guess Valera forgot to elog it. Steve, please email him and get the info.

I started to check out the OL servos today so that our whole interferometer is not too floppy.

  • The ETMX OPLEV DAQ channels were not in the list. Jamie ran the activateDQ.py script and it came back. Right now, we have no diagnostics to know if people have run this or not so the frames will have missing data now and again depending on how forgetful the rebooters are. Perhaps we can get activateDQ put into the make file???
  • I turned ON all of the offset buttons on the OL1, etc. filter banks. This allows for the dark offsets to be set for the OL quadrants. With these buttons off it doesn't make any sense.
  • I noticed that there are white (INVALID) fields all over the OPTLEV_SERVO screens. This is just because the new SUS models have not captured all of the functionality of the old system. Needs fixing.


Some of these OL spectra are not like the others...


  5005   Wed Jul 20 19:48:03 2011 JamieUpdateSUSRe: oplev gains today


 We have been modifying models that need to have their channels renamed to run activateDQ when Joe's post_build_script to is run. 

The trick is to integrate things to get the post_build_script running after every model build (getting it hooked in to the make file somehow).  We're working on it.

 I've added the following epics channels to sus_single_control model using the epicsOutput part:

  • OL_SUM
  • OL_YAW

These channels are now all available.  I'm not exactly sure how to ensure that they're being trended.  I'll check that tomorrow.

  5006   Wed Jul 20 20:04:54 2011 JamieUpdateCDSC1:DAQ-FB0_C1XXX_STATUS sometimes unexplainably goes red

I have been noticing this happening occasionally, but I don't understand what is causing:


The channel in question above is C1:DAQ-FB0_C1SCX_STATUS.  This channel is (I believe) reporting some status of the front end model communication with the frame builder, but I'm not sure exactly what.

Usually this problem goes away when I restart the model or the frame builder, but it didn't work this time.  Tomorrow I will figure out what this channel means, why it's sporadically going red, and how to correct it.

ELOG V3.1.3-