I tried to run the scripts/senseMCdecentering to check the centering of the MC beam spots on the mirrors. The script (csh) produces a lot of error messages on the control room machines. They are machine dependent combination of "epicsThreadOnce0sd epicsMutexLock failed", "Segmentation fault", "FATAL: exception not rethrown". Most of ezcawrite commands fail but not all(?). After running the mcassUp script couple of times all the dither lines came on. The MCL responses to dither lines look qualitatively similar to what it was in February (plot attached). The overall MCL spectrum looks ~100 times lower, presumably due to the analog gain reallocation.

Before that I realigned the beam into the PMC, recentered the PSL QPDs, and the beam into the MC to bring the MC RFPD_DC from ~3 to ~1.5 VDC then tweaked MC2 to bring the MC RFPD_DC from ~1.5 to ~1 VDC.

The mcass dither lines are off now and the loops are disabled.

The RF amplifier of the prototype BBPD has been replaced from ERA-5SM to MAR-6SM.
The bandwidth is kept (~200MHz for S3399 with 30V_bias), and the noise level got better while the maximum handling power was reduced.

MAR-6SM is a monolithic amplifier from Minicircuits. It is similar to ERA-5SM but has lower noise
and the lower output power.

The noise floor corresponds to the shotnoise of the 0.4mA DC current.
Now the mess below 50MHz and between 90-110MHz should be cleaned up.
They are consistently present no matter how I change the PD/RF amp (ERA<->MAR)/bias voltage.
I should test the circuit with a different board and enhanced power/bias supply bypassing.

Discussion on the RF power (with M. Evans)

- Assume 5mA is the maximum RF (~50mW for 1064nm, ~15mW for 532nm). This is already plenty in terms of the amount of the light.

- 100% intenisty modulation for 5mA across 50Ohm induces -2dBm RF power input for the amplifier.

- Assume if we use MAR-6 for the preamplifier. The max input power is about -18dBm.
  This corresponds to 16% intensity modulation. It may be OK, if we have too strong intensity modulation, we can limit the power
  down to 0.8mA in the worst case. The shot noise will still be above the noise level.

- In the most of the applications, the RF power is rather small. (i.e. 40m green beat note would expected to be -31dBm on the RF amp input at the higherst, -50dBm in practice)
So probably we need more gain. If we can add 10-12dB more gain, that would be useful.

- What is the requirement for the power amplifier?

• Gain: 10~12dB
• Output (1dBcomp): +3dBm +Gain (13dBm~15dBm)
• Noise level / Noise Figure: 3nV/rtHz or NF=14dB
  The output of MAR-6 has the votage level of ~7nV/rtHz. If we bring the power amplifier with input noise of ~3nV/rtHz,
  we can surppress the degradation of the input equivalent noise to the level of 10%. This corresponds to N.F. of 14dB.

Search result for Freq Range 10-200MHz / Max Gain 14dB / Max NF 15dB / Min Power Out 13dBm
GVA-81 is available at the 40m. ERA-4SM, ERA-6SM, HELA-10D are available at Downs.

Conversion between nV/rtHz and NF (in the 50Ohm system)

SN1: Connect signal source (50Ohm output) to a 50Ohm load.
Power ratio between the noise and the signal

SN1 = (4 k T (R/2)) / (S/2)^2

SN2: Connect signal source (50Ohm output) to an RF amp.
Only the voltage noise was considered.

SN2 = (4 k T (R/2) + Vn^2) / (S/2)^2

10 Log10(SN2/SN1) = 10. Log10(1 + 2.42 (Vn / 1nVrtHz)^2)

e.g.
Vn: 0 nVrtHz ==> 0dB
Vn: 0.5 nVrtHz ==> 2dB
Vn: 1 nVrtHz ==> 5dB
Vn: 2 nVrtHz ==> 10dB
Vn: 3 nVrtHz ==> 13.5dB

The SLP-50 filters which were on the 55 MHz lines have been replaced with the SBP-60.  Their respective characteristics are given below:

SBP-60 has lower insertion loss and higher return loss.  

This may however change the phase of I and Q in the demod boards and they will therefore need to be readjusted.  Currently the output power level of 55 MHz demod is at 2dBm, whereas it ought to be at 6dBm.   I have not yet corrected that.  Once that is completed Kiwamu will adjust the phases.

 I shifted the temperature sensor to a new location.  See the photograph below.  I noticed that the higher temperature is reached on the side where there are two RF Amps.  So it would be better to check the temperature of that  area and make sure that it remains well below 65 deg.  The operating maxium is 65deg C

Here is a picture of the new RF source layout.

And here is a photograph of it

[Suresh / Kiwamu]

 We installed the TRY photo diode (Thorlabs one) and the ETMYT CCD camera in place on the ETMY table.

Now we can see a signal on the TRY digital channel.

It will be quite useful for the Y arm locking, for instance we can do a triggered locking and the maximization of the intracavity power.

Someone has to install the EMTY trans QPD at some point.

The SRM qpd cable was removed from the BS-table. It's path was changed from 1x4 to ITMY-table following the inner cable tray.

Dry fore pump of TP3 replaced by brand new Varian SH-110  at  1.1 Torr_75,208 hrs

The annuloses were closed off for 25 minutes. We are back to VACUUM NORMAL mode.

The TP3 fore line pressure dropped to 44 mTorr at 25 minutes in operation.......9.4mTorr at day 2 with full annulos load

 After Kiwamu set the REFL11 phases in the PRMI configuration (maximized PRM->REFL11I reesponse) I tried to measure the MC length and the 11 MHz frequency missmatch by modulating the 11 MHz frequency and measuring the PM to AM conversion after the MC using the REFL11Q signal. The modulation appears in the REFL11Q with a good snr but the amplitude does not seem to go through a clear minimum as the 11 MHz goes through the MC resonance.

We could not relock the PRMI during the day so I resorted to a weaker method - measuring the amplitude of the 11 MHz sideband in the MC reflection (RF PD mon output on the demod board) with a RF spectrum analyzer. The minimum frequency on the IFR is 11.065650 MHz while the nominal setting was 11.065000 MHz. The sensitivity of this method is about 50 Hz.

I tuned the ITMY bandstops -- 'before' and 'after' spectra attached.  Note that the after the tuning, the bounce mode at ~16 Hz is about twice as quiet!

However, notice that in the 'before' plot the roll mode at about 23.5 Hz did not show up at all, whereas it is quite prominent in the 'after' plot.  I was concerned that this line could have been a result of placing the bandstop there, so I made another plot with the BounceRoll filter turned off.  Sure enough, the 23.5 Hz line is still there.  So I'm not crazy: the roll mode did start acting up at some time between my 'before' and 'after' plot, but not as a result of the tuning.

The emphasis of this annual safety audit  was on  safe  electrical housekeeping on March 3, 2011

We now have the DC signal from three PDs available in the ADC channels 14,15 and 16.  The signals are from  REFL55, AS55 and POY photodiodes respectively.  As the DC signals on all the other PDs of the same port (REFL, AS and PO)  have the same information we do not need to monitor more than one DC PD at each port.

The LSC PD Interface Card, D990543 - Rev B, can take 4 PDs and provides the DC signals of the PDs on the connector P2 (the lower of the two) on the back plane of the chassis. An adaptor card, D010005-00, plugs into the back plane from the rear of the Eurorack and provides the four DC signals on two-pin lemo sockets.

I have connected the three DC signals from the relevant RF PDs (above) to a DC whitening filter, D990694-B-1 which is associated with the channels 9 to 16 of the ADC card.

The cables are in a bit of a mess right now as some of the PD power supply lines are too short to reach up the the Interface card in the top Eurocart. Steve and I plan to redo some of the cabling later today

Minicircuits ERA-5SM was used for the RF amp of the BBPD. This amp is promising as a replacement of Teledyne Cougar AP389
as ERA-5SM gave us the best performance so far among the BBPDs I have ever tested for the aLIGO BBPD/Green.

The -3dB bandwidth of ~200MHz and the noise floor at the shotnoise level of 0.7mA DC current were obtained.

1. Introduction

The aLIGO BBPD candidate (LIGO Document D1002969-v7) employs Teledyne Cougar AP389 as an RF amplifier.
This PD design utilizes the 50Ohm termination of the RF amp as a transimpedance resistance at RF freq.

However, it turned out that the bandwidth of the transimpedance gets rather low when we use AP389, as seen in the attachment2.
The amplifier itself is broadband upto 250MHz (the transfer function was confirmed with 50Ohm source).
The reason is not understood but AP389 seems dislike current source. Rich suggested use of S-parameter measurement
to construct better model of the curcuit.

On the other hand, the RF amplifiers from Minicircuits (coaxial type like ZFL-1000LN+), in general, exhibit better compatibility with PDs.
If you open the amplifier case, you find ERA or MAR type monolithic amplifiers are used.

So the question is if we can replace AP389 by any of ERA or MAR.

2. Requirement for the RF amp

- The large gain of the RF amp is preffered as far as the output does not get saturated.

- The amplifier should be low noise so that we can detect shot noise (~1mA).

- The freq range of the useful signal is from 9MHz to 160MHz.

The advanced LIGO BBPD is supposed to be able to receive 50mW of IR or 15mW of 532nm. This approximately corresponds to
5mA of DC photocurrent if we assume FFD-100 for the photodiode. At the best (or worst) case, this 5mA has 100% intensity modulation.
If this current is converted to the votage through the 50Ohm input termination of the RF amp, we receive -2dBm of RF signal at maximum.

This gives us a dilemma. if the amp is low noise but the maximum output power is small, we can not put large amount of light
on the PD. If the amp has a high max output power (and a high gain), but the amp is not low noise, the PD has narrow power range
where we can observe the shotnoise above the electronics noise.

What we need is powerful, high gain, and low noise RF amplifier!

Teledyne Cougar AP389 was almost an ideal candidate before it shows unideal behavior with the PD.
Among Minicircuits ERA and MAR series, ERA-5 (or ERA-5SM) is the most compatible amplifier.

Considering the difference of the gain, they are quite similar for our purpose. Both can handle upto -2dBm,
which is just the right amount for the possible maximum power we get from the 5mA of photocurrent.

3. Test circuit with ERA-5SM

A test circuit has been built (p.1 attachment #1) on a single sided prototype board. 

First, the transfer function was measured with FFD-100. With the bias 100V (max) the -3dB bandwidth of ~200MHz was observed.
This decreases down to 75MHz if the bias is 25V, which is the voltage supplied by the aLIGO BBPD circuit. The transimpedance
at the plateau was ~400Ohm.

Next, S3399 was tested with the circuit. With the bias 25V and 30V (max) the -3dB bandwidth of ~200MHz was obtained although
the responsivity of S3399 (i.e. A/W) at 1064nm is about factor of 2 smaller than that of FFD-100.

The noise levels were measured. There are many sprious peaks (possibly by unideal hand made board and insufficient power supply bypassing?).
Othewise, the floor level shows 0.7mA shotnoise level.

The PMC exhibited the reduction of the transmission, so it was aligned.

The misalignment was not the angle of the beam but the translation of the beam in the vertical direction
as I had no improvement by moving the pitch of one mirror and had to move those two differentially.

This will give us the information what is moving by the temperature fluctuation or whatever.

I think that the gain ramping time (_TRAMP) should be set to 1 second for all filter modules by default. We don't want them to switch instantaneously except in a few special cases.

So Jamie and I wrote a script (in scripts/general/) which sets all of these fields to 1 for a given system. The name of the system is an argument to the script. e.g.

>  setTRAMP LSC 1

The idea is that we set it once and then from then on, its captured by the autoBURT. Of course, we have to run this script each time we add new filter modules to a model.

I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs.  I'll do the MCs, the PRMs, and the SRMs next.

I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain).  It looked like this:

ellip("BandStop",4,1,40,11.4,12.2)ellip("BandStop",4,1,40,16.7,17.5)gain(1.25872)

Valera said that one of these was for the roll mode and the other for the bounce mode.  However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz.  So, we're taking a guess that this was for a mode that has moved due to new pendulum designs.  For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line.  Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental.  When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.

ITMX is done.  I'll continue tomorrow.  I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).

(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops.  It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)

 This was because of a bug in the RCG for foton filter module naming when top names is being used.  Rebuilding the LSC front-end model with top_names (which was needed to get around another bug in the RCG) broke the filter file.  I manually fixed the file, so it should work now.

New right angle PVC front panel with SMA bulkhead connectors are in place. The connections are still lose. It is ready for Suresh to finalise his vision on it.

They are the DC responses.

I put the resonant frequencies that Leo reported in the wiki to obtain the DC response.

The resonant frequencies I used are :

  f_BS = 0.957 Hz

  f_ITMX = 0.966 Hz

  f_ITMY = 0.988 Hz

Also I assumed that all the Q-values are 5 due to the damping.

I installed 'glue' on Rossa, Allegra, and Rosalba.  This is a Python module that includes a facility for LIGO_LW XML files.  Oddly, I couldn't find the glue package on Pianosa.

 I was wrong. Rana did not fix the interface box. I removed the interface box and turned down the HEPA flow  from 100 to 20% on the Variac.

 See my updated elog 4636 for what Joe and I did this morning, and what a possible problem is (making the LSC model into a sub-model).

I've got confused

1) Are these the DC responses of the coils? If that is true, we need to specify the resonant frequency of each suspension to get the AC response.

2) Are these the AC responses well above the resonant freqs? In that case, The responses should be x.xxx / f^2 [m/counts]

EDIT by KI on 15/5/2011:

The calibration of MICH error signal was wrong by a factor of 2.

The open loop transfer functions of the Michelson locking have been measured.

The purpose of this excise is to calibrate the coil-magnet actuators on BS and ITMs.

The estimated actuation coefficients are :

 BS = 3.69e-08 [m/counts]
 ITMX = 8.89e-09 [m/counts]
 ITMY = 9.22e-09 [m/counts] 

I guess the accuracy is something like 5 % because the calibration of the MI optical gain relies on a peak-to-peak measurement.

A next step is to calibrate the PRM actuator and the PRC optical gain.

(measurement)

The Michelson was locked with different actuators in every measurement. I locked the Michelson to the dark fringe with BS, ITMX and ITMY in each time.

The measured peak-to-peak value in the error signal was 20.2 counts, corresponding to a sensor gain of 5.96e+07 [counts/m]. Note that I used AS55_Q for the locking.

After locking the MI I took the open loop transfer function by injecting broadband noise from DTT.

Then the data were fitted coarsely.  In the fitting I used the resonant frequencies that Leo reported recently (http://blue.ligo-wa.caltech.edu:8000/40m/Mechanical_Resonances).

The Q-values are assumed to be 5 because of the local dampings. As a result the fitting gives us the actuator coefficients.

Here is a plot showing the measured open loop transfer functions. The solid lines represent the fittings.

(by the way)

- The delay time including ADC/DAC and RFM looks quite big. According to the fitting the delay is something like 600 usec.

This is about two times larger than the one reported before (see this entry). I will re-measure it with empty filters.

Foton doesn't correctly display the LSC filter bank file : C1LSC.txt.

Foton tells a lie that they all are empty.

The file itself looks fine to me i.e. I can find correct filters in text format.

Looks like someone (maybe Joe and Jenne ?) updated the file. I am not sure if this is the reason or not.

allegra:chans>ls -al | grep LSC
-rw-r--r--  1 controls controls   20659 May  5 11:46 C1LSC.txt

NEEDS TO BE FIXED SOON

Joe helped me compile the lsc simulink model, and now we have R&D phase rotation.

Right now, we have to do our own math, and figure out what relative phase to put in.  Soonly, I'll figure out how to do subtraction, and we can put in the measured value.

More details when I'm not running around like crazy...

--------------------------------------------------------------------------------------------

Okie dokie.  Last night I had modified the c1lsc.mdl to accommodate the R & D phase rotation.  I also made pretty new screens.  This morning however, the adventures began.....

Under Joe's supervision, I ran "make c1lsc".  The error that came up was something about things not being connected.  Joe assures me that this is a temporary problem, that Rolf is already working on.  The reason is that right now the LSC model is "flat", i.e. it doesn't have a bunch of sub-boxes and sub-screens in the simulink model.  Somehow this causes badness.  Joe stuck all the guts of the LSC model into a sub-model.  He then enabled "top_names", which makes the channels use the name of the sub-model, not the sub-model AND the main model (so since the sub-model is called LSC, our channels are just C1:LSC-OTHER_STUFF, rather than C1:LSC-LSC_OTHER_STUFF).  This fixed things so that the compiling worked (when we did "make c1lsc").  The one other thing that we changed was to delete all of the little "Outs" that were attached to EPICS readouts.  These are unneccessary and don't go anywhere, and when we made the sub-model, they made a bunch of empty outputs (unconnected outs on the main simulink model).  So, after doing that, we were able to compile, and do "make install-c1lsc", and all was good in the world.  Mostly.

Joe then noticed that I was using the CDS part "cdsPhase", which only takes one phase input.  I wanted "cdswfsPhase", which actually does the R&D phase rotation that we want.  Perhaps Alex/Rolf/whoever should change the name of that CDS part.  We switched all of the cdsPhase blocks to be cdswfsPhase, and recompiled.  All was still good in the world.  Mostly.

The last thing that was funny was that when I wanted to execute the medm screens, they would still look at the old _IQ_MTRX_1_1 and _IQ_MTRX_2_1 values, rather than the newly defined _PHASE_R and _PHASE_D channels, even though while editing the medm screen, it looked like it was pointing to the right place.  Anyhow, I opened the text file version of the C1LSC_PDX.adl, and changed the channel names to the _R and _D versions by hand.  I don't know if we edit the screens and run generate_screens.py again, if we'll have to re-edit the .adl text files.

After fixing this, all really was good in the world. 

Perhaps though, this making a subsystem business broke the filters somehow?  Foton is looking at the wrong text file now?  Something?  The filters are all still there, they just got moved down a level.  Joe said that he and Rolf are on it, and he should be able to put the LSC model back to being "flat" in the next few days.

eeek.  I've been running around all day, so this is an incomplete elog.  I'll fill in more stuff in the next hour or so, but just to let people know what's going on:

[Valera, Jenne]

Valera noticed that lots of things in and around the PSL table are drifting with temperature.  This is why he and Steve installed a temp sensor on the table earlier today.

Since the alignment into the PMC, and also the alignment downstream of the PMC have been drifting in angle, we supposed that it might be the PMC itself which is changing somehow with temperature.  We don't have a good idea of how exactly it is sensitive to temperature, but we're working on figuring it out.

Round 1 of testing:  We put a foil hat over the PMC to shield it from the HEPA air blowing directly down on top of it.  I made sure that the foil is also covering the PZT and the metal ring at the end of the PMC, because this could potentially be the problem (metal is usually more temperature sensitive than glass, or the PZT itself could be changing, either of which could make the end mirror twist, and change the alignment of the PMC).  We'll see later if this did anything useful or not. 

I have photos of the aluminum foil setup, which I will post later when I get back to the lab after teaching. 

 Having finished the bulk of the work for the LPF itself ( see here ), I have begun trying to design the seismometer box to Jenne's specifications.

Currently looking into what the voltage buffer amplifier might look like for this.

Suggestions/corrections would be much appreciated!

Valera and I installed the the temp sensor and the interface box that Rana fixed. This may help with diagnosing the PSL drift.

Comparison between Hamamatsu S3399 and Perkin Elmer FFD-100

These are the candidates for the BB PD for the green beat detection as well as aLIGO BB PD for 532nm/1064nm.

FFD-100 seems the good candidate.

Basic difference between S3399 and FFD-100

- S3399 Si PIN diode: 3mm dia., max bias = 30V, Cd=20pF

- FFD-100 Si PIN diode: 2.5mm dia., max bias = 100V, Cd=7pF

The circuit at the page 1 was used for the amplifier.

- FFD-100 showed 5dB (= x1.8) larger responsivity for 1064nm compared with S3399. (Plot not shown. Confirmed on the analyzer.)

- -3dB BW: S3399 180MHz, FFD-100 250MHz for 100V_bias. For 30V bias, they are similar.

I modified C1LSC.mdl to use the CDSphase blocks, which automatically calculate the R and D phase rotation for us.  Now each of the RFPDs has 2 channels in place of the old IQ_MTRX channels:  C1:LSC-RFPD_PHASE_R and C1:LSC-RFPD_PHASE_D.

I have not yet compiled / rebooted / done CDS magic to actually make these installed.  So far the change is only in the simulink model.

I was going to wait until morning to compile/reboot/magic, so I can do it under Joe's supervision.

In the meantime, I also modified the RFPD screens.  They have white boxes for the _R and _D channels just now, but that's because the new model hasn't been put in.  They now look like phase rotators, instead of Koji's temporary matrix.

Still to do:  Find the EPICS database where the phase rotation calculation is done (you give it an angle, it gives you sin(angle) and cos(angle) ).  I want to put a "90-angle" in the database so that we can type in the measured relative phase between I and Q, and it will calculate how many more degrees it needs to get to 90deg. 

Building on what was posted previously

The configuration has now evolved into an Inverting Op Amp Feedback Low Pass Filter circuit.

Had to change out some components to satisfy conditions: R1=1k Ohm, R2=10k Ohm, C=0.1uF. These were changed in order to decrease the magnitude of the current passing through the op amp by a factor of 10 (10V supplied through the R1 resistor yields about 10mA). The configuration itself was changed from non-inverting to inverting in order to get the frequency vs. gain part of the Bode plot to continue to decrease across higher frequencies instead of leveling off around 4kHz.

The attached plot shows 2 day trends of the PMC and MC reflected and transmitted power, the PSL POS/ANG QPD signals, and the temperature measured by the dust counter.

The power step in the middle of the plot corresponds to Koji/Jenne PMC realignment yesterday.

It looks like everything is following the day/night temperature changes.

I went push all the possible connectors for the MC3 shadow sensors including the SCSIs, flat cables and satellite box.

Also I put screws on them so that they won't become loose any more.

As a result UL_PDMON dropped from 0.6 V to 0.490 V and it becomes stable so far.

I didn't strain relief the cables but we must do it at some point before going into the full locking test.

[Leo  w/ a little help from Kiwamu]

Leo summarized the mechanical resonances of all the suspensions, based on the free-swinging spectra taken on Sat Apr 30.

Since Leo doesn't have the wiki account I helped him putting the information on the wiki.

Good work, Leo !

http://blue.ligo-wa.caltech.edu:8000/40m/Mechanical_Resonances

The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.

The rest of the MC1,2,3 PD signals looked ok.

Last night I was trying to calibrate the MICH error signal and the actuators on BS and ITMs.

However I gave up taking the data because the MC locking was unstable. MC3 drifted a lot.

REFL55 has been installed on the AP table.  REFL11 has been moved to make space for a 50% beam splitter. The reflected beam from this splitter is about 30% of the transmitted beam power.  The reflected beam goes to REFL11 in the current configuration.  The DC levels are 1.2V on REFL 11 and 3.5V on the REFL55.

I redid some of the cabling on the table because the we need to choose the heliax cables such that they end up close to the demod board location.  As per the 1Y2 (LSC) rack layout given here, some of the PD signals have to arrive at the top and others at the bottom of the LSC rack.

Currently the PDs are connected as follows:

REFL11 PD --> Heliax (ASDD133) (arriving at the top of LSC rack) --> REFL11 Demod Board 

REFL55 PD --> Heliax (REFL166) (arriving at the top of LSC rack) --> AS55 Demod Board

AS55 PD --> Heliax (AS166) (arriving at the top of the LSC rack) --> not connected.

We are waiting for the Minicircuits parts to modify the rest of the demod boards.

The heliax cables arriving at the LSC rack are not yet fixed properly.  I hope to get this done with Steve's help today.

[Valera, Suresh]

The first time I noticed that the MC was not locking was after I had finished switching the RF source installation.  Before this change the RF modulation frequency (for MC) was 29.485 MHz as read from the Marconi RF Source.  We replaced this with a Wenzel crystal source at 29.491 MHz.  This may have changed the loop gain. 

Today, I changed the MC alignment to optimise the MC lock.  Valera pointed out that this is not a desirable solution since it would shift the beam pointing for all components downstream.  However, since we are not sure what was the last stable configuration, we decided to stay with the current settings for now and see the trends of several parameters which would tell us if something is drifting and causing the autolocker to fail.

The MC Auto locker is now working okay.  However to obtain lock initially we reduced the loop gain by decreasing the VCO gain.  We then increased the gain after the autolocker had locked the MC.

I found that the MC autolocker was OFF. Kiwamu says he turned it off because its slow. Suresh says that he has some feelings that maybe something is wrong. I'll let them describe what they know about the MC in an elog.

I checked the trend of the MC and PMC transmissions for the past 30 days:

Looks like the alignment has been drifitng. PMC was corrected recently by Koji, but the alignment of the input beam to the MC or the MC itself has to be fixed. Has someone been twiddling the MC SUS alignment biases??

[Rana/Jamie/Kiwamu]

 Since we've got the PRMI locked we now should be able to do more qualitative measurements.

Here is a task list that we will measure/develop in the PRMI condition.

 - Optical gain measurements

 - Characterization of control loops

 - MICH and PRC calibrations

 - Noise budget

 - Development of automatic noise budget scripts

 - Arm loss measurement 

 - Shnupp asymmetry measurement

My observation wasn't accurate enough.

The looseness came from the fact that the N-SMA bulk heads were slipping on the black plate.

This is actually what Suresh pointed out (see here). So the thickness of the black plate doesn't matter in this case.

Somehow I was able to tighten the bulk heads using two wrenches and I think they are now tight enough so that the heliax's heads don't move any more.

Here are some details about the PRMI locking done last night.

(REFL11 installation)

 REFL11 has been installed on the AP table. The RF signal from the RFPD is sent by a heliax cable which has been called ASDD133.

Before the beam goes into the RFPD a HWP and PBS are installed such that we can adjust the amount of light entering to the photo diode.

One thing I didn't like was that I had to introduce a big amount of the light into the PD to get a reasonably big RF signal.

I was trying to look for an RF signal by looking at a spectrum analyzer, then I realized that the RF signal at 11 MHz was quite tiny when the DC_MON was less than 1.5 V.

After I increased the amount of the light up to 1.9 V in DC_MON, which sounds already too much, I then got able to see the 11 MHz signal on the analyzer.

Note that I decreased the amount of the light down to 0.5 V after I finished locking the PRMI.

We should make sure what is going on with the 11 MHz modulation.

(Locking)

First I started locking the MIchelson with AS55. The demodulation phase was already somewhat optimized to the I-signal port.

So I decided not to touch the demodulation phase matrix because it may take some times.

After I eliminated electrical offsets in the digital side, I was easily able to lock the Michelson. The control sign was plus.

Then I started playing with the PRC control too. The demodulation phase in REFL11 looked nearly 45 deg although I didn't carefully measure it.

I made a 45 deg rotational matrix to maximize the I-port signal and tried to lock the PRC. Then immediately I was able to lock PRC as well as MICH.

 GAIN_MICH = 100

 GAIN_PRC = 100

Also GAIN_PRC = -100 gave a carrier resonant lock.

The control filters are the same in MICH and PRC. I used my favorite filters as usual.

 FM1 = 1000 : 10

 FM6 = 0.1 : 1

 FM7 = 1 : 50

Somehow I frequently failed to engage the boost filters (i.e. FM6 and FM7) it looks offsets in the control path kicks either BS or PRM.

 Atm 1,  PRM oplev inward path with 2 lens solution: 14 cm gap between F 1145 and F 1545 mm lenses. 

Atm 2,   The PRM beam size 3 mm and the beam  quality is still bad. The BS path only needed alignment.

The little red all terrain cargo wagon 40" x 18"  has just arrived on pneumatic wheels.

Model #29, 200 lbs max load at 26 PSI,  minimum age requirement 1.5 years

This is a continuation of this

 The low pass filter is finally acceptable, and its Bode graph is below (on a ~3Hz frequency span that shows the cutoff frequency is at 0.1Hz)

Jenne went through all the suspension racks and pushed all the connectors.

After pushing them, we had a quick look at those spectra and found no funny noise spectrum except for C1:PRM-SENSOR_UL.

We then checked connection around the SCSI cables and eventually found the connection between ADC_card_0 and a SCSI was loose.

We put short standoffs on the ADC card so that the screws from the SCSI can nicely reach to the ADC card. Now everything looks fine.

SUS diagnostic is quite useful !

 I was charge with making a Non-Inverting Op Amp Low Pass Feedback circuit for Jenne, which may somehow be integrated into a seismometer project she's working on.

Circuit diagram is attached. Calculations show that R1, R2 and C have the following relationship: if R1=10^n, R2=10^(n+1), C=10^(-n-4). For the particular circuit being modeled by the transfer function, R1=100 Ohm, R2=1k Ohm, and C=1uF.

Attached also is the circuit's Bode plot, showing frequency versus gain and phase, respectively. The frequency versus gain graph is true to what the circuit was calculated to generate: a gain of +20 and a cutoff frequency at 200Hz. Not sure what's going on with the frequency verus phase plot.

Here are the free-swinging spectra for the BS, ETMX, ETMY, ITMX, ITMY, MC1, MC2, MC3, and PRM chambers.  Kiwamu left the suspensions free for 5 hours this weekend, starting at Sat Apr 30 00:15:26 2011.

This is GPS time 988 182 941.  Quick tip: you can do local to GPS time conversions using lalapps_tconvert, which is a lot like tconvert but with special powers.  It is installed on pianosa.

$ lalapps_tconvert Sat Apr 30 00:15:26 2011

988182941

I generated these figures with the attached Python script, measure.py.

Notice that the C1:SUS-ITMX_SENSOR_UL and C1:SUS-MC3_SENSOR_UL spectra fall as 1/f.  Jenne suggested that this might indicate that there is a loose electrical connection.

Also, notice that C1:SUS-ETMY_SENSOR_LR, C1:SUS-ITMY_SENSOR_LL, and C1:SUS-PRM_SENSOR_SIDE are a lot noisier above 10 Hz.

Done. C1:PSL-PMC_PMCTRANSPD was improved from ~0.75 to 0.87.

I temporarily turned off the power to the 1Y2 rack this morning while wiring in the binary output adapter board power (+/- 15V) into the cross connects.

The board is now powered and we can proceed to testing if can actually control the LSC whitening filters.