I measured the Transfer Functions between from IN2 to IN1 on the WFS1PIT, WFS2PIT, WFS1YAW and WFS2YAW servo loops. 

Then I used the foton filter profiles of the servo filters in the loop and added another one to simulate the pendulum to generate a reasonable fit to the data.  Only the pendulum filter was hand tweaked since the PIT and YAW pendula have different resonant frequencies.

The filter modules included are:

1) Integrator: zpk([0.8],[0],0.8,"n")

2) Phase lead: zpk([0.8],[100,100],1,"n")

3) 45 deg filter: zpk([1:10],[3,30],1,"n")

4) ELP28: ellip("LowPass",5,1,50,28)

5)Pendulum: zpk([ ],0.03+i*0.82;0.03+i*0.82;],1,"n"  (for YAW)

5)Pendulum: zpk([ ],0.05+i*0.68;0.05+i*0.68;],1,"n"  (for PIT)

The data and fits are below.   The UGF is around 2 to 3 Hz and there is no servo bump at this gain setting.  The fits are poor at and below the resonance because the coherence was poor at these frequencies.  I will have to do a swept sine measurement for these low frequencies.

[Steve, Suresh]

    Steve went over to the MC2 walkway and stepped over the barrier to pick up some stuff there.  MC2 stack shifted and MC2 pitch as off.  MC unlocked and could not relock till the MC2 pitch bias was readjusted

previous MC2PIT reading: 3.6235           current MC2PIT reading:  3.9565

Without the WFS the MC to PSL alignment is poor, but it is largely due to a shift in the MC and not a shift in the PSL beam.  We know this 'coz the shift in the DC spot positions on WFS (when the MC is unlocked) is not significant nor is the shift on the C1:IOO-QPD.  When WFS loops are engaged the MC optics are turned to optimise the PSL to MC alignment, but the shift is large at the moment.

(Sorry Mirko your measurement could not be completed.  The MC unlocked in the middle)

Please Note:  If you need to access the blocked off area near MC2 stack, do not step over the barrier.  The disturbance is too great and the MC2 stack will shift.  Instead please move the barrier aside and walk as gently as possible near it, taking care not to touch the MC2 Chamber.

I turned on the two remaining loops in the ASC system to see if we can lock.   I put in some ones into the WFS_OUTPUT matrix

and locked the MC2_TRANS_PIT and MC2_TRANS_YAW loops.

The effect of doing so is visible in the error signals.  The black loops are with all ASC loops off, Blue traces are with the WFS1 and 2 loops locked and Red traces are with all loops locked.  I took the red traces to a lower frequency to see if the suppression of the error signals at low frequencies is disturbed by the switching on of the MC2_TRANS loops.  They seem to be working fine without adding any perturbation above the UGF.

I measured the  Transfer Function coefs (at 10Hz using the WFS Lockins)  with MC2_TRANS loops locked in this rudimentary fashion

The green and blue bits are the only relevant parts since we ignore the off diagonal parts.  And most of these off diagonal coefs are indeed quite small (<5% of the max).  I have marked the not-so-small ones in yellow.

I then calculated the output matrix elements in two different ways.

a) Using a null vector in the place of MC_DoF --> MC2_TRANS transfer coefs.  The output matrix we get is

b) Without using the null vector.  i.e. using the MC_DoF --> MC2_TRANS transfer coefs and inverting the full matrix.  The output matrix we get is

I plan to try out these two output matrices and measure the OL TFs of the MC2_TRANS and see if we can include these into ASC in a useful fashion.

Apparently the MC2 stack had not finished shifting.   The MC unlocked while Steve was working on the PSL table installing the mirror for IOO_QPD and then it could not relock.  So I moved the MC2 once again in Pitch.  The current status of the sliders is here

Yesterday I fixed the yellow buttons on the MC_ALIGN and MCLOCK screens.  They use the new updatesnap script  .  Could we also add a couple of lines to this script so that eveytime we save a snap shot the various values are written(appended) to a text file?  That way we do not need to depend solely on the conlog, which is quite slow.

I have modified the 'mcwfson' and 'mcwfsoff' scripts to include the Clear History step for the MC2_TRANS_PIT and _YAW filters.  

These scripts can be run, by hand, from LOCKMC screen or from the WFS_MASTER screen.  Use the 'Turn WFS ON/OFF' button. 

The mcautolockmain script will now clear history on all ASC filter banks when the MC unlocks.

I have turned on ASC loops on the MC2_TRANS (= alignment transmission DOFs of the above elog) paths.

[Den, Mirko, Suresh]

    We were investigating why there is no correlation between MC1 osem signals and seismic motion.   During this we noticed a recurrence of this old problem of MC1_LR sensor being dead.  I went and pressed down the chip holders where the AA filters used to sit and which now hold the jumper wire.  The board is large and flexible it is quite likely some solder joint is broken on the MC1_LR path on this board.

   The signal came back to life and is okay now. But it can break off again any time.

[Koji, Suresh]

    We investigated the effect of airflow from the HEPA filters on the PSL beam fluctuation and the resultant noise injected into the WFS loops.   The hint that the WFS are injecting PSL beam jitter into MC mirror motion lies in the MC2_TRANS_PIT and YAW signal's power spectrum shown here.  First, in the blue trace, which shows the spectrum when the WFS loops are off, we see that the WFS1 and WFS2 error signals have a different shape from that of MC2_TRANS.  Since WFS are affected by the PSL beam jitter while the MC2_TRANS_QPD is not, the WFS spectrum contain excess noise, while the MC2_TRANS signals show only the mirror motion.  Next, upon switching on the WFS1 and WFS2 loops, we notice that the MC2_TRANS  spectra acquire the same shape as the WFS spectra.  This shows that the excess noise from the beam jitter has been injected into the MC2 motion, and shows up in the MC2_TRANS spectra.

   To confirm these conclusions we repeated the above measurement with the HEPA fans at 0% (Blue trace), 20% (Red), 30% (Brown) and  100% (Green).   The plots are shown below.  We can see that there is no difference between 0 and 20% levels but beam jitter is visible at 30% HEPA level.  The WFS loops were ON during this time and we can can see the PSL noise injected in to MC2 motion (Green).

The HEPA filter fans are now at 20%.  How can we be sure that they are really working at 20%, since we cannot see any difference between 0 and 20%?

Now that we have this quiet situation, we also investigated the effect (or lack thereof) of switching on the MC2_TRANS loops.  The figure below shows the spectra with all the loops turned off (Blue), with the WFS1 and WFS2  loops turned on (Green)  and with everything turned on (Red).   With the current output matrix, which is the same simple one as the one in this elog, we see some low frequency suppression.  But it also seems to add some noise into the other WFS loops.  I am not sure of this result, due the long duration of this measurement, the seimic noise level may have changed over the course of this measurement.

As they are not doing any good just now.  I have turned them off by setting the gain in MC2_TRANS PIT and YAW to zero.

Without adding significant amounts of noise to other WFS loops I have engaged the MC2_TRANS_PIT and YAW loops. 

After several attempts to measure the system response and computing the output matrix, none of which gave any useful results, I gave up on that and decided to find three orthogonal actuation vectors which enable us to close the loops.  So using the last good output matrix (below left side)  as a template, I rounded it off to the nearest set of orthogonal vectors and arrived at the following matrix (right side):

I also decided that WFS1 and 2 need not drive MC2.  This is just to decouple the loops and minimise cross-talk.   This (albeit heuristic)  matrix seems to work pretty well and the real matrix is probably quite close to it.

I show below the suppressed error signals after tweaking the gains a bit.   The blue line is with no WFS, the green one with only WFS1 and 2 loops on, while the red is with all loops turned on.  The WFS1Yaw and MC2_Trans_pit loops might benefit from a more careful study to determine a better output matrix.

[Koji Suresh]

As part of the general lab clean up we removed many unused BNC cables (long and short) from around the SP table.  We removed one very long BNC cable which was connected on one side to an PEM input and not connected on the other side near the 1X2 rack..   There were several cables from an old SURF phase camera project which were still attached to a couple of RF amps on the SP tables and running towards the 1X6 rack. 

We also removed some unused power cables  plugged into a power distribution strip near Megatron.

The PSL alignment into the MC was too poor for the autolocker to engage.  So retaining the last coil slider settings on the MC_Align screen that Kiwamu wanted, I have realigned the PSL beam and recentered the beam on the WFS.

When the WFS_MASTER was burtrestored after the recent power shutdown, the values loaded into the output matrix were not optimal.  When we switch on the WFS loops now, the MC_TRANS loops seem to push the WFS into away from the best possible coupling to PSL.  So I have switched them off for now.   Will load a new optimised output matrix and measure the transfer functions to see what is going on.

What I did:

    I have changed the c1ioo model such that the signals which are demodulated in the WFS lockin (the SIG inputs) are now picked up just after the input matrix.  This permits us to put a notch filter at the excitation frequency into the WFS servo filterbanks and thus prevent the excitation of all the actuators when we wish to excite just one of them. 

The Problem:

    I had followed the procedure of determining the TF coefs between actuators (MC1,2,3 P and Y ) and sensors (WFS1, 2 and MC2Trans P and Y)  and found the output matrix by inverting this TF coef matrix. However these matrices, once substituted for the heuristically determined matrices were always unsuccessful in keeping the WFS servo lock.  The reason appeared to be that when the loops are closed the exitation of one actuator led to the excitation of all actuators through the cross couplings in the output matrix.    In order to prevent this we need a notch filter in the servo filter banks.   But then we will not be able to see the sensor response after the servo filters since the response at 10Hz would be blocked from reaching the lockins.  So I shifted the point at which we sample the sensor response to a point before the WFS servo filters. 

The solution:

a) shift the point where the lockin input signals are picked up in the c1ioo model.

b) retune the lockin servo phases to minimise Q phase

c) edit the WFS lockin scripts to ensure that the 10Hz notch is turned on

d) measure the TF coefs and compute the -1*inverse

e) plug it into the output matrix and tweak the gains to ensure a stable lock

f) examine cross talk by comparing the expected TF in each loop with the expected loop TF.

Current state:

  I have completed steps a to e above.  The loops are stable and the error signal is suppressed (see attached pdf files)

To be done:

  The open loop transfer function has to be compared with expected OLTF to be sure we have minimised cross talk.

[Koji, Suresh]

Kiwamu mentioned that REFL165 is not responding and its DC out seems saturated at 9V.  Koji and I checked to see if changing the power supply to the PD changed its behaviour. It did not.  

I then look a close look at the PD and found that the front window of the PD was not clear and transparent.  There was a liquid condensation inside the window, indicating an over heating of the PD at some point.  It could have arisen due to excessive incident power.  The pic below shows this condensation:

I also checked the current flowing through the reverse bias voltage line.  There was a voltage drop of 3V across R22 (DCC D980454-01-C)   indicating a 150mA of current through the PD.  This is way too much above the operating current of about 20mA.   The diode must have over heated.

I pulled out the old PD out and installed a new one from stock.  The pic below shows the clear window of a new PD.

After changing the PD I checked the DC output voltage while shining a torch light on to the PD.  It showed an output of about 30 to 40 mV.  This seemed okay because the larger 2mm photodiodes showed ~100mA DC output with the same torch.Below is the current state of the ckt board.

I will tune the PD to 165 MHz tomorrow and measure its transimpedance.

The transfer function and current noise were measured.  The location of the peak shifts with the amount of incident light power (RF or DC).  The TF was measured at an incident 1064nm light power of 0.4 mW which produced a DC output voltage of 14 mV => DC photocurrent of 0.28 mA. 

Many of the effects that Koji noted in the previous characterization are still present.

In addition I observed a shift of the peak towards lower frequencies as the RF power supplied to the AM Laser (Jenne Laser) is increased.  This could create a dependance of the demodulation phase on incident RF power.

The plots are attached below.

1) The REFL165 has been replaced onto the AS table.

2) When the PD interface cable is attached the PD shows a DC out put of 6mV and does not respond to a flash light.  I changed the PD interface port in the LSC rack by swapping the other end of the cable with an unused (Unidentified PD) interface cable,  The PD is working fine after that.   There could be a problem with some binary switch state on the PD interface where the REFL165 cable was plugged in earlier.

 [Koji, Suresh]

To determine the amount of RF power in the AM laser beam at various RF drive levels I measured the RF power out of the Newfocus 1611 PD while driving the AM laser with a Marconi.  During this measurement the DC output was 2.2V.  With the DC transimpedance of 10^4 and a sensitivity of 0.8 A/W we have carrier power as 0.275 mW (-5.6 dBm).  [Incidentally the measured carrier power with a power meter is about 0.55 mW. Why this discrepancy?]

Estimation of the signal strength at the REFL165 PD:

   From the 40m Sensing Matrix for DRFPMI we see that the signal strength at REFL165 in CARM is about 5x10^4 W/m.  Since we expect about 0.1nm of linear range in CARM length we expect about 0.05 mW of RF power.  If the (DC) carrier power is about 10 mW at the photodiode (18mW is about the max we can have since the max power dissipation is 100 mW in the diode)  then the RF : DC power ratio is 5x10^-3 => -23 dB

As this is lower than the power levels at which the PD transfer function was determined and where we noted the distorsion and shift of the resonance peak, it is likely that these effects may not be seen during the normal operation of the interferometer.

The shift due to the carrier power level (DC) change may still however pose a problem through a changing demodulation phase. 

I have completed the calibration of the demod board efficiencies.  Here is the schematic of the set-up.

The data is given below and the data-file is attached in several different formats.

 The REFL165 RF output was not reaching the Demod board.  The RF cable was disconnected.  I fixed that and then I put in a RF signal at 165MHz , 1.66 mVrms at the test input  (100Hz off set from the 165MHz LO) and saw that the 100 Hz demodulated signal was visible in the dataviewer. 

Will complete the Optical RF power -> CDS counts calibration tomorrow morning. 

These are the measurements for estimating the amplitude of the signal recorded in the CDS when a known amount of modulated light is incident on the photodiode. 

I mounted the PD characterisation setup onto a small breadboard which could then be placed close AP table.  I then placed position markers for REFL165 on the AP table before moving it onto my small breadboard.  The AM laser was driven by an RF function generator (Fluke 6061A) at a frequency of 165.98866 MHz, which is 102 Hz offset from the 165MHz LO.  The power level was set at -45dBm.  This power level was chosen since anything higher would have saturated the AntiAliasing  Whitening Filters.  The counts in the CDS were converted to voltage using the ADC resolution = 20V per 2^16 counts.

 When the 166MHz power is decreased by a factor of 2 the amplitude of 102Hz wave recorded in CDS goes down by sqrt(2) as expected.   The RF AM power incident on the REFL165 was estimated to be 0.011mW(rms)  (case #1 in the above table)  using the DC power ratio and using the transimpedance of the 1611 BBPD to be 700 Ohms.  This produces a 171 mV amplitude wave at 102 Hz.  I then stepped down the power by factor of 2 and repeated the measurement. 

(These numbers however are not agreeing with the power incident on REFL165 if we assume its transimpedance to be 12500.  It will take a bit more effort to make all the numbers agree.  Will try again tomorrow)

Here is a picture of the small black breadboard on which I have put together the PD characterisation setup.  It would be great if we can retain this portable set up as it is, since we keep reusing it every couple of weeks.  It would be convenient if we can fiber couple the path to the PD under test with a 2m long fiber.  Then we will not have to remove the PD from the optical table while testing it.

 The filter was ON and the whiterning filter gain was 45dB

There was something wrong with the Beam Scan PC.  The  mouse and screen were not responding and the PC was asking for drivers for any new hardware that we plugged in.  We called in the services of Junaid and co. since we do not have a Win98 Second Edition installation disk in the lab.   Junaid came with the disk, we changed the screen and the mouse and installed everything. 

We tried to get the network going on the PC so that we could update stuff easily over the net.  This didnt succeed. For now, we still have to depend on a Win98se CD to get drivers if any new hardware is connected to this machine. 

For future reference, some notes:

1)  We will get a copy of Win98SE for the lab from Junaid

2) We have to use a USB mouse from Dell. We have several spares of this. The drivers for these are present in the machine. 

The Beam Scan is working okay now.  We will proceed with the beam profile measurements.  

[Kiwamu, Suresh]

   Today we attempted to measure the beam profile of the REFL beam under two conditions:

              (a) with PRM aligned and ITMs misaligned 

              (b) with PRM misaligned and ITMs aligned

The raw data is shown below.  In each of the above conditions we measured in both the vertical (v) and horizontal (h) directions.   The measurements in the vertical direction were better than the ones in the horizontal direction because the optics had a horizontal oscillation which gave larger errors in measurement.

Looking at the general trend of these lines it is clear that modes are not matched since the beam reflected by the PRM has a different divergence than that reflected from ITMs.  The beam is also astigmatic as the vertical and horizontal directions have different divergences.

I could find beam parameters only for the Blue line above (Profile in the vertical direction while PRM was aligned).   The fit is quite sensitive to the data points close to the waist, so we need to make better (lower St.Dev.) measurements near the AP table closer to the beam waist.  The intensity with only one ITM aligned is too low and also contributes to the errors.   The beam size is close to 6mm in the horizontal direction, this coupled with yaw oscillations give large errors in this measurement.

Here is the only reliable fit that could be obtained, which is for the prompt reflection from the PRM in the vertical direction

The fit function I used is  Beam Dia = Waist { Sqrt [ 1+  ((z + z0)/zr)^2). The fit parameters we get for this data are

z0 = 7.7 m 

Waist = 2.4 mm

zr = 6.9 m

Will make another attempt later today...

[Keiko, Suresh]

   Keiko and I measured the IPPOS beam profile.  The fit parameters  are :

The data files are attached. 

If we assume the nominal wavelength of the IR light to be 1064nm and constrain the Rayleigh length to be zr = (pi w0^2)/lambda we obtain the following fit parameters: (these are compared with the beam profile measurements of June/18/2010 available in the wiki )

* I updated the waist waist location coz because I missed-out the distance in air from the vacuum port to the optic on the IPPOS table.

 In an attempt to estimate the errors on the fit parameters I upgraded my Mathematica code to use the function 'NonlinearModelFit', which allows us to define weights and also reports the errors on the fit parameters.   The plots have been upgraded to show the error bars and residuals.

The parameters determined are given below and compared to the earlier measurements of 06/18/2010

Vertical Profile:

Horizontal Profile:

There is a significant change in the beam waist location (as compared to previous report) because I corrected a mistake in the sign convention that I was using in measuring the distances to the waist from the zero-reference.
 

I am trying to track down possible errors in our measurements. 

So as a first step I am recomputing the IPPOS waist location with respect to the MC waist, using the same optical layout diagram as the one used by Jenne in her calculations.  Pic of Jenne's lab notebook showing location of optics is attached.  

 Let us compare it with the old measurement of the IPPOS beam from June/18/2010.

Note that there is a discrepancy of about 3.2 m in the waist location for the vertical profile and about 3.5 m for the horizontal profile between these two measurements. 

Let us compare these measurements with what is expected from calculations.  Jenne uses the known parameters of MC waist and the locations of the MMT optics to compute the parameters for the IPPOS beam:

 As the 2010 measurements are reported wrt to MMT2 and calculations are wrt MCwaist, I have used the distance between the MCwaist to MMT2 = 3.910 m to shift the reference from MMT2 to MC waist. Refer to the attached diagram from Jenne's notes for this MMT2 <--> MC waist distance.

There is a discrepancy of 1.5 meters between the calculations and recently measured waist location.  The discrepancy with the 18Jun2010 measurement is much larger, about 3 meters in both v and h.

Are such variations to be expected between two successive measurements?  I looked at another case where we have two measurements of a beam to see what to expect.

I looked at the REFL (Reflection from PRM) case, where we repeated a measurement, to see how much variation could happen in w0 and zr, between repeated measurements. This was a particularly bad case as our first attempt had problems due to OL servo loop oscillations in the PRM suspension damping.  We fixed that later and measurement 2 has smaller residuals. And I think we are doing okay in IPPOS case as seen by the reduced scatter of the residuals.

 These are the fits from the REFL beam measurement 1

 I have also recomputed the fits to the data from REFL beam measurement 2.  They match the earlier fits reported by kiwamu in his elog 6446

Note that between these two measurements the beam waist location has shifted by 0.5 m for the vertical and about 1.3 m for the horizontal cases.  So variations of 1.5 m in the waist locations are possible if we are not careful.  But this is a particularly extreme example, I think we are doing better now and the measurement is unlikely to change significantly if we repeat it.

Some notes:

Fits for IPPOS and both REFL measurements 1 and 2 are attached. 

The zero reference for the z axis of the IPPOS beam plot is at a distance of 6.719 m from MC waist for a beam propagating towards the IPPOS QPD.

The zero reference for the z axis of the REFL beam plots is at a distance of 5.741 m from the MMT2 in the direction of a beam reflected by PRM and propagating towards the REFL port.

[Suresh, Jenne]

  The input beam is most probably being clipped at the Faraday Isolator.  

Evidence: 

a)  The beam scan of the IPPOS beam showed a nongaussian beam in the horizontal direction.  This was visible in the beam scan since it overlays a gaussian-fit over the data.

b)  I was able to remove this departure from gaussian profile by introducing an offset of 5 into the C1:IOO-WFS2_YAW_OFFSET.  

c)   We made a few measurements of the beam diameter as a function of distance at an offset of 7.  At a distance of beyond 3 m the deviation from gaussian profile was once again apparent. 

d)  We increased the offset to 14 to remove this deviation. 

e)  When we measured the beam diameter again with this new offset the horizontal diameter and vertical diameters dropped by 2.sigma.  Indicating there the beam was clipped till then.

f)   We increased the offset to 16 and the beam diameter did not change further (within 1.sigma). Implying no more clipping, hopefully. 

And then the earthquake stopped us from proceeding further. 

We plan to investigate this further to be sure..  Data attached.

Subsidiary effects to keep track of:

1) Introducing an offset into the WFS loops decreases the coupling from PSL into MC. 

2) If the beam is being clipped at the Faraday Isolator then the REFL beam would also show lesser clipping with WFS offsets.

    WFS servo is moving the MC mirror angles to minimise TEM01 and TEM10 modes within the MC cavity.    This means it will compensate not only for angular noise in the mirrors but also for the PSL beam pointing fluctuations.  So the extra "noise" we see when WFS loops are on is because they are active below the WFS UGF of about 2 Hz.  Also if the HEPA airflow is above 20% (of its max), the PSL beam jitter (caused by the airflow) will add broadband noise into the WFS servo loops and this will show up in the OSEM signals.  See elog 5943 for details.

I tried to determine an optimal WFS2YAW offset to be used so that we may avoid clipping.

Initially, I just measured the beam diameter as a function of offset.  If the beam diameter would become independent of offset if it is not clipped.  However a systematic effect became apparent when I shifted the beam on the detector to a slightly different location.  So I repeated the measurements while recentering the beam to the same location everytime  (centered at -1650+/- 50 for both H and V directions).

I have attached plots of the scans for both cases, with recentering and without.    I have not been able to figure out what is going on since the beam diameter does not become independent of the offset.  While the beam profile becomes more gaussian beyond offsets of about 7 or so, the beam diameter does not seem to follow a clear pattern.  The measurements are repeatable (within one sigma) so the experimental errors are smaller than 1 sigma.

The photographs below show the improvement of Horizontal beam profile with WFS2Yaw offset.  These seem to indicate a good gaussian beam for offsets beyond 7 or so.  At offsets more than 12 the MC unlocks.

Offset = -2	Offset = 0	Offset = 2	Offset = 8

This seems to indicate that the beam diameter does not vary for WFS2Yaw offset > 8	But if we recenter the beam for each measurement this effect seems to vanish

 Will continue tomorrow.   Jenne wants to do some IFO locking now.

I have installed ACAD 2002 on one of the Windows machines in the Control Room.    It is on the machine which has Solid Works (called C21530). 

The installation files are in MyDocuments under Acad2002.  This a shared LIGO license which Christian Cepada had with him.

I hope we will be able to open our optical layout diagrams with this and update them even though it is an old version.

   I have worked out the fibers we need to get for the following distribution scheme:

1) We have a laser placed at the 1Y1 rack.  A part of the power is split off for monitoring the laser output and sent to a broadband PD also placed in the same rack.  The RF excitation applied to the laser is split and sent to LSC rack (1Y2) and used to calibrate the full PD+Demod board system for each RFPD.

2) A single fiber goes from the laser to a 11+ way switch located in the OMC electronics cabinet next to the AP table.  From here the fibers branch out to three different tables.

Cable for the laser source to the OMC table:

We also require a cable going from PSL table to the ETMY table:   This is not a part of the RFPD characterisation.  It is a part of the PSL to Y-end Aux laser lock  which is a part of the green locking scheme.  But it is  fiber we need and might as well order it now along with the rest.

If you would like to add anything to this layout / scheme, please comment.  On Monday Eric is going to take a look at this and place orders for the fibers.

(I have included the lengths required for routing the fibers and added another 20% to that ) 

The MC2 Oplev signal path has been modified in the c1mcs model.  The ADC channels have been sent over the rfm into c1ioo model and are currently used in the WFS servo loops.  Please see this elog 5397.

[Jamie, Suresh]

Yesterday Den and Koji reported that the WFS loops were causing the MC to become unlocked.  They had aligned the PMC.   The input beam into the MC seems to be well aligned.  MCREFL DC close to minimum it gets while MC is locked (~0.45 V).

I checked and saw that the WFS heads and the MC2_TRANS_QPD had picked up DC offsets.  To reset them I turned off the MC_autolocker and closed the PSL shutter.

The ADC offsets were set using this script /cvs/cds/rtcds/caltech/c1/scripts/MC/WFS/WFS_QPD_offsets.  (Jamie fixed the paths to ezcaservo to get this script to work)

The WFS sensor head offsets were manually set to adjust the Q and I signals from the sensor head to zero.  (This operation is supposed to be done by a script which is available, but I will check it out before I direct people to it).

Then we noticed that the ASC outputs were turned off.  (Presumably Koji turned them off yesterday, when the MC was repeatedly unlocking due to the WFS loops).

We turned on the ASC outputs and the MC stayed locked with reasonable outputs on the WFS output channels.  (+/-100)

However, engaging the WFS servo increases the MCREFL DC signal to 0.7 V from the 0.45 V value when the servo is not engaged.  This could be because of DC offsets in the WFS servo filters.   I will adjust these offsets to maintain good MC transmission when the WFS servo is engaged.

Frame builder is down.  PRM has tripped its watch dogs.  I have reset the watch dog on PRM and turned on the OPLEV. It has damped down.  Unable to check what happened since FB is not responding.

There was an minor earthquake yesterday morning which people could feel a few blocks away.  It could have caused the the PRM to unlock.

Jamie,Rolf,  is it okay or us to restart the FB?  

I tried restarting the fb in two different ways.  Neither of them re-established the connection to dtt or epics.

1) I restarted the fb from the control room console with the 'shutdown' command.  No change.

2) I halted the machine with 'shutdown -h now' and restarted it with the hardware reset button on its front-panel. No change.

The console connected to the fb showed that the network file systems did not load.  Could this have resulted in failure to start several services since it could not find the files which are stored on the network file system?

The fb is otherwise healthy since I am able to ssh into it and browse the directory structure.

[Mike, Rana]

The fb is okay.  Rana found that it works on Pianosa, but not on Allegra or Rossa.  It also works on Rosalba, on which Jamie recently installed Ubuntu.

The white fields on the medm  'Status' screen for fb are an unrelated problem.

 [Koji, Suresh]

  We tried to locate the sixteen analog output channels we need to control the four tip-tilts (four coils on each).  We have only 8 available channels on the C1SUS machine. 

  So we will have to plug-in a new DAC output card on one of the machines and it would be logical to do that on the C1IOO machine as the active tip-tilts are conceptually part of the IOO sub-system.   We have to procure this card if we do not already have it.  We have to make an interface between this card output and a front panel on the 1X2 rack.  We may have to move some of the sub-racks on the 1X2 rack to accommodate this front panel.

  We checked out the availability of cards (De-whitening, Anti-imaging, SOS coil drivers)  yesterday.  In summary: we have all the cards we need (and some spares too).  As the De-whitening and Anti-imaging cards each have 8 channels, we need only two of each to address the sixteen channels.  And we need four of the SOS coil drivers, one for each tip-tilt.  There are 9 slots available on the C1IOO satellite expansion chassis (1X1 rack), where these eight cards could be accommodated.

  There are two 25 pin feed-thoughs, where the PZT drive signals currently enter the BS chamber.  We will have to route the SOS coil driver outputs to these two feed-throughs. 

   Inside the BS chamber, there are cables which carry the PZT signals from the chamber wall to the the table top, where they are anchored to a post (L- bracket).  We need a 25-pin-to-25-pin cable (~2m length) to go from the post to the tip-tilt (one for each tip-tilt).  And then, of course, we need quadrapus cables (requested from Rich) which fit inside each tip-tilt to go to the BOSEMs.

   I am summarising it all here to give an overview of the work involved.

    The only script that can currently take this action is the MC autolocker.  If that is disabled first and the PMC unlocks later, the WFS will not be turned off.  During the last round of discussions we had about the autolocker script, sometime last Nov, we decided that too much automation is not desirable and that the autolocker should be kept as simple as possible.

   Here is the suggested layout of the MC health check web page layout. I will update the Omnigraffle file as people comment and suggest changes.  If you want the file let me know.

[Yuta, Suresh]

We found that the MC was not locking and that the alignment between PSL and MC was too poor to obtain a TEM00 mode in the MC.   To correct the situation we went through the following steps:

1) We burt restored the MC alignment slider values to their values at 3:07 AM of today

2) We turned off the MC-autolocker and the ASC signal to the coils.   Then aligned the PSL beam into the MC (with the MC servo loop off) to obtain the TEM00 mode.  We had to adjust the zig-zag at the PSL output by quite a bit to maximise MC transmission.

3) We then centered the spot on the MC2 face and centered the transmitted beam on the MC2_TRANS_QPD

4) Next, we centered the beams on the MC_WFS sensors.

5) Turning on the WFS loops after this showed that everything works fine and WFS loops do not accumulate large offsets.

[Koji, Yuta, Suresh]

We measured the MC spot positions after re-aligning the MC.  The spot positions are listed below:

spot positions in mm (MC1,2,3 pit MC1,2,3 yaw):
    3.9073    6.6754    2.8591   -7.6985   -0.9492    7.0423

Procedure:

1) In the directory /opt/rtcds/caltech/c1/scripts/ASS/MC  we have the following scripts

      a) mcassUp:    This sets up the MCASS lockins to excite each of the MC mirrors at a different frequency

      b) mcassOn:    This sets the MCASS output matrix to actually send the excitation signals to the mirrors

      c) senseMCdecenter:  This sequentially introduces a 10% offset into the coil gains of each mirror degree of freedom.   It also sends the lockin output data to the screen. 

      d) sensemcass.m :  This is a matlab file which digests the data gathered by the senseMCdecenter script to print a couple of plots and compute the spot positions.

      e) MCASS_StripTool.stp:  This is a set-up file for the StripTool which allows us to see the MCASS-lockin_outputs.  It is nice to see the action of senseMCdecenter  script  at work.

2) So the series of commands to use are

      a) ./StripTool  <-- MCASS_StripTool.stp

      b) ./mcassUp

      c) ./mcassOn

      d) ./senseMCdecenter | tee Output_file

       e) ./mcassOff

      f) ./mcassDown

       g) matlab <-- sensemcass.m  <---- Output_file

Mike Pedraza came by today to install a new wireless network router configured for the 40m lab network.  It has a 'secret' SSID i.e. not meant for public use outside the lab.  You can look up the password and network name on the rack.  Pictures below show the location of the labels.

I have made a preliminary sketch of the cabling involved in connecting the Tip-tilt coil drivers.   This is a preliminary document. 

 The scheme currently is to run a 25pin Kapton strip cable from BS to IMC table inside the chamber.  However we cannot do the same for the OMC table since it will cross the bellows which we often remove.  So we need to supply the one tip-tilt on the OMC table from outside.  I could not spot a spare unused feedthough on the OMC chamber.  We will have to swap one of the blank flanges for one with a few feed throughs.

We do not have any of the cables.   So everything listed has to be arranged for.   The pics are from the existing coil driver system on the SUS machine.

Recent History

The lower blades which I had given to the Physics Workshop for making a vacuum relief hole (using a sinker-EDM process) came back about ten days ago.   Merih Eken <meken@caltech.edu>,  the supervisor at the Physics Dept workshop, handled this matter for us.  The blades were sent to a local EDM machineshop and returned in about three working days ( a weekend intervened). 

Bob cleaned and handed them over to me yesterday evening.  

Current status

Today I have reassembled the four tip-tilts.  I have repacked them in clean bags (double bagged) shifted them to Clean Optics Cabinet (near the ETMX chamber).  The four tip-tilts are in the bottom-most shelf in the cabinet.  There are also some tip-tilt spares in a separate envelope.

Note:  The mirror holder is now held tightly by the eddy current dampers.  This was done for safety of the wires during transportation from LHO.  The eddy current damper in the front of the mirror has to be retracted to allow the mirror holder to swing free.  It has be to about 1mm away from the suspended mirror holder

Work Remaining

1) We need to install the quadrapus cables.  The connector placement on the BOSEM side will have some issues.  It is best to loosen the BOSEM seating as well as the connector seating screws and then push the cable connector into place.  Caution:  when the connector seating screws on the BOSEM are loosened the flexible ckt could be damaged by the loose connector.

2) Insert the mirrors into the mirror holders and balance the suspension such that the mirror's hang vertical and do not have a large yaw offset.

3) Adjust the wire suspension point height so that the flags are in the center of the BOSEM aperture.  Else they will strike against the

4) We need to adjust the position of the BOSEMs such that the shadow sensor signals are at 50%.  This ensures that all the magnets hang at an appropriate distance from their respective coils.

5) To do (3) we need to set up a shadow sensor read-out set-up for one tip-tilt (four sensors)

The reason for using Alberto's laser is that some amount of work has already gone into characterising its phase noise.  Ref elog entry 2788

We have positioned the guide rod and the wire-stand-off on the optic in the axial direction. 

We have selected six magnets whose magnetic strength is +/-5% of their mean strength (180 Gauss).  The measurement was made as follows:

1) each magnet was placed on its  end, on the top of a beaker held upside down. 

2) The Hall probe was placed directly under the magnet touching the glass from the other side (the inside of the beaker). 

This ensures that the relative position of the magnet and the probe remains fixed during a measurement.  And ensures that their separation is the same for each of the magnets tested. 

With this procedure the variation in the measured B field is less than +/- 10% in the sample of magnets tested.

[Jenne, Suresh]

The ETM assembly has moved forward a couple of steps.  We have completed the following:

1) Positioning the guide rod and wire stand-off on both the ETMs (5 and 7)

2) The magnets had to be cleaned with an acetone wash as they had touched the plastic Petri-dish (not cleaned for vacuum).

3) The magnets and the Al dumb-bells have been glued together and left to cure in the gluing fixture.

4) The guide-rod and wire stand-offs have also been glued to the optic and left to cure for 24 hrs.

JD:  As you can see in my nifty status table, we are nearing the end of the suspension story.  

We are going to try (but can't guarantee) to get ETMX to Bob for baking by Friday at lunchtime, that way we can re-suspend it on ~Monday, and place it in the chamber.  Then we could potentially begin Green arm locking next week.  Steve has (hopefully!!) ordered the spring plungers for ETMY.  The receiving and baking of the spring plungers is the only current delay that I can foresee, and that only is relevant for one of the optics. 

We (who is going to be in charge of this?) still need to move the SRM OSEMs & cables & connectors to the ITMY chamber from the BS chamber. 

[Jenne, Suresh]

 Jenne found the X-end table enclosure had been left open.  She replaced the lid on it.

We did several things today+night.  The final goal was to lock the PRC so that we could obtain the POX, POY and POP beams.  However there were large number of steps to get there.

1) We moved the ITMY into its place and balanced the table

2) We then aligned the Y-arm cavity to the green beam which was set up as a reference before we moved the ETMY and ITMY to adjust the OSEMS.  We had the green flashing in Y-arm

3) We checked the beam position on PR2. It was okay. This confirmed that we were ready to send the beam onto the Y arm.

4) We then roughly aligned the IR beam on ETMY where Jamie had placed an Al foil with a hole.  We got the arm flashing in both IR and green. 

5) We used the PZTs to make the green and IR beams co-incident and flashing in the Y arm.  This completed the alignment of the IR beam into the Y-arm.

6) The IPPO (pick-off) window had to be repositioned to avoid clipping.  The IPANG beam was aligned such that it exits the ETMY chamber onto the ETMY table.  It can now be easily sent to the IPANG QPD.

7) Then BS was aligned to direct the IR beam into the X-arm and had the X-arm flashing.  It had already been aligned to its green.

8) It was now the turn of the SRC.  The beam spots on all the SRC related optics were off centered.  We aligned all the optics in the AS path to get the AS beam on to the AP table.

9) The AS beam was very faint so we repositioned the AS camera to the place intended for AS11 PD, since there was a brighter beam available there. 

10) We could then obtain reflections from ITMY, ITMX and PRM at the AS camera. 

11) Problems:

      a) ITMY osems need to be readjusted to make sure that they are in mid-range.  Several are out of range and so the damping is not effective.

      b) When we tried to align SRC the yaw OSEM had to be pushed to its full range.  We therefore have to turn the SRM tower to get it back into range.

 12)  We stopped here since moving the SRM is not something to be attempted at the end of a rather long day. Kiwamu is posting a plan for the rest of the day.

PR2's side magnet height was adjusted and its roll was balanced (attachment 1,2). I verified that the OpLev beam is still aligned. The pitch was balanced: First, using an iris for rough adjustment. Then, with the QPD. I locked the counterweight setscrew.

I turned off the HEPAs, damped PR2, and measured the QPD spectra (attachment 3). Major peaks are at 690mHz, 953mHz, and 1.05Hz. I screwed back the lower OSEM plate. The wires were clamped to the suspension block and were cut. Winch adapter plate removed. I wanted to push OSEMs into the OSEM plates but the wiki is down so I can't tell what was the plan. This will have to wait for tomorrow. Also here like with AS1 we need to apply glue to the counterweights.