In this past weekend I replaced a summing amplifier for the end green PDH locking by a home-made summing circuit box in order to increase the control range.
It's been working well so far.
However due to this circuit box, the demodulation phase of the PDH locking is now somewhat different from the past, so we have to readjust it at some point.
However due to this circuit box, the demodulation phase of the PDH locking is now somewhat different from the past, so we have to readjust it at some point.
At the X end station, the voltage going to the NPRO PZT had been limited up +/- 4 V because of the summing amplifier : SR560.
Therefore the laser was following the cavity motion only up to ~ +/- 4 MHz, which is not wide enough. (it's okay for night time)
So we decided to put a passive circuit instead of SR560 to have a wider range.
We made a passive summing circuit and put it into a Pomona box.
The circuit diagram is shown below. Note that we assume the capacitance of the 1W Innolight has the same capacitance as that of the PSL Innolight (see #3640).
The feedback signal from a PDH box goes into the feedback input of the circuit.
Then the signal will be low passed with the corner frequency of 200 kHz because of the combination of RC (where R is 681 Ohm and C is capacitance of the PZT).
Because of this low pass filter, we don't drive the PZT unnecessarily at high frequency.
On the other hand the modulation signal from a function generator goes into the other input and will be high passed by 50 pF mica capacitor with the corner frequency of 200 kHz.
This high pass filter will cut off noise coming from the function generator at low frequency.
In addition to it, the 50 pF capacitor gives a sufficient amount of attenuation for the modulation because we don't want have too big modulation depth.
Here is a plot for the expected transfer functions.
You can see that the modulation transfer function (blue curve) has non-zero phase at 216 kHz, which is our modulation frequency.
I forgot to mention about the whitening filter for the ALS digital control system.
As usual I used a whitening filter to have a good SNR against ADC noise, but this time our whitening scheme is little bit different from the usual our systems.
I used two ADC channels for one signal and put a digital summing point and digital filters to keep good SNR over the frequency range of interest.
It's been working fine but it's still primitive, so I will study more about how to optimize this scheme.
The diagram above shows our scheme for the signal whitening.
Basically the SNR at DC is bad when we use only a whitening filter as shown on the bottom part of the diagram because the signal is quite tiny at DC.
On the other hand if we take raw signal into ADC as 'DC path' shown above, the SNR is better at DC but not good at intermediate frequencies (30 mHz - 1kHz).
So the idea to keep the good SNR over the frequency range of interest is to combine these 'DC path' and 'AC path' in a clever way.
In our case, the 'DC path' signal is not as good as the 'AC path' signal above 30 mHz, so we cut off those high frequency signals by using a digital low pass filter.
In addition to it, I put a gain of 1000 in order to match the relative gain difference between 'DC path' and 'AC path'.
Then the resultant signal after the summing point keeps the good SNR with a flat transfer function up to 1 kHz.
Two different measurement have been performed for a test of the green locking last night.
Everything is getting better. yes. yes.
[ measurement 1 : IR locking]
The X arm was locked by using the IR PDH signal as usual (#4239, #4268) .
The in-loop signal at from the IR path and the out-of-loop signal at from the green beat note path were measured.
Let us look at the purple curve. This is an out-of-loop measurement by looking at the green beat note fluctuation.
The rms down to 0.1 Hz used to be something like 60 kHz (see here), but now it went down to approximately 2 kHz. Good.
This rms corresponds to displacement of about 260 pm of the X arm. This is barely within the line width. The line width is about 1 nm.
[ measurement 2 : green locking]
The motion of the X arm was suppressed by using the green beat signal and feeding it back to ETMX.
After engaging the ALS servo, I brought the cavity length to the resonance by changing the feedback offset from epics.
Then took the spectra of the in-loop signal at the beat path and the out-of-loop signal at the IR PDH path.
Here is a time series of TRX after I brought it to the resonance.
TRX was hovering around at the maximum power, which is 144 counts.
Since I put one more 10:1 filter to suppress the noise around 3 Hz, the rms of the in-loop beat spectrum went to about 1 kHz, which used to be 2 kHz (see #4341).
But the out-of-loop (IR PDH signal) showed bigger noise by a factor of 2 approximately over frequency range of from 2 Hz to 2 Hz. The resultant rms is 2.7 kHz.
The rms is primarily dominated by a peak at 22 Hz (roll mode ?).
I calibrated the IR PDH signal by taking the peak to peak signal assuming the finesse of the cavity is 450 for IR. May need a cooler calibration.
I did a quick calculation to determine the amount of sideband transmission through the FP cavity.
The modulation frequency of the end PDH is 216kHz. The FSR of the cavity is about 3.9MHz. So the sidebands pick up about 0.17 radians extra phase on one round trip in the cavity compared to the carrier.
The ITM reflectance is r_ITM^2 = 98.5% of power, the ETM reflection is r_ETM^2 = 95%.
So the percentage of sideband power reflected from the cavity is R_SB = r_ITM*r_ETM*(exp(i*0.17) - 1)^2 / (1 - r_ETM*r_ITM exp(i*0.17) )^2 = 0.85 = 85%
So about 15% of the sideband power is transmitted through the cavity. The ratio of the sideband and carrier amplitudes at the ETM is 0.05
So, on the vertex PD, the power of the 80MHz +/-200kHz sidebands should be around sqrt(0.15)*0.05 = 0.02 = 2% of the 80MHz beatnote.
Once we get the green and IR locked to the arm again, we're going to look for the sidebands around the beatnote.
Uniblitz mechanical shutter was placed into the beam path of the PSL output with razor beam trap. The output power was 1.39W at 2.08A
It is working from the MEDM screen "old map" C1IOO_Mech_Shutter.adl
Cheater cables for SRM sus tied up. They were dangling aimlessly on the floor.
Just in case anyone else wants to access it, we now have 30 days of H1 S5 DARM data sitting on Rossa's harddrive. It's in 10min segments. This is handy because if you want to try anything, particularly Wiener Filtering, now we don't have to wait around for the data to be fetched from elsewhere.
[Kevin, Rana, Koji]
I calculated the dark noise of POX and POY due to Johnson noise and voltage and current noise from the MAX4107 op-amp using nominal values for the circuit components found in their data sheets. I found that the dark noise should be approximately 15.5 nV/rtHz. The measured dark noise values are 18.35 nV/rtHz and 98.5 nV/rtHz for POX and POY respectively. The shot noise plots on the wiki have been updated to show these calculated dark noise sources.
The measured dark noise for POY is too high. I will look into the cause of this large noise. It is possible that the shot noise measurement for POY was bad so I will start by redoing the measurement.
Having finished labeling the existing cables to match their new names, we (Steve, Kiwamu and Larisa) moved on to start laying new cables and labeling them according to the list.
Newly laid cables include: ETMXT (235'), ETMX (235'), POP (110') and MC2 (105'). All were checked by connecting a camera to a monitor and checking the clarity of the resulting image. Note that these cables were only laid, so they are not plugged in.
The MC2 cable needs to be ~10' longer; it won't reach to where it's supposed to. It is currently still in its place.
The three other cables were all a lot longer than necessary.
I put the PMC last mode matching lens (one between the steering mirrors) on a translation stage to facilitate the PMC mode matching.
Currently 4% of incident power is reflected by the PMC. But the reflected beam does not look "very professional" on the camera to Rana - meaning there is too much TEM20 (bulls eye) mode in the reflected beam.
I locked the PMC on bulls eye mode and measured the ratio of the TEM20/TEM00 in transmission to be 1.3%. Thus the PMC mode matching is ~99% and the incident beam HOM content is ~3%.
While working on the PMC I found that the source of PMC "blinking" is not the frequency control signal from MC to the laser (the MC servo was turned off) but possibly some oscillation which could be affected even by a small change of the pump current 2.10 A to 2.08 A. I showed this behaviour to Kiwamu and we decided to leave the the current at 2.08 A for now where things look stable and investigate later.
Alex and I updated the open mx drivers from 1.3.3 to 1.3.901 (1.4 release candidate). We downloaded the drivers from: http://open-mx.gforge.inria.fr/
We put them in /root/open-mx-1.3.901 on the fb machine (and thus get mounted by all the front ends.). We did configure and make and make install.
We did a quick check with /opt/mx/bin/mx_info on the fb machine at this point and realized the MAC addresses and host names were all messed up, including two listings for c1iscex with different mac addresses (neither of which was c1iscex).
We then brought all the front ends mx_streams down, brought the fb down, then cleared all the peer names with mx_hostname. We then brought the fb up, and the front end mx_stream processes.
/opt/mx/mx_info now shows a clean and correct set of hostnames and mac addresses. Testpoints and trends are working.
In addition to the other fixes, Alex rebuilt the daqd process. I failed to elog this. When he rebuilt it, he needed change the symmerticom gps offset in the daqdrc file (located in /opt/rtcds/caltech/c1/target/fb).
On Friday night, Kiwamu contacted me and let me know the frame builder had core dumped after a seg fault. I had him temporarily disable the c1ass process (the only thing we changed that day), and then replaced Alex's rebuilt daqd code with the original daqd code and restarted it. However, I did not change the symmetricom offset at this point. Finally, I restarted the NDS process. At that point testpoints and trends seemed to be working.
The daqd process was restarted sometime on Sunday night (by Valera i believe). Apparently this restart finally had the symmetricom gps offset kick in (perhaps because it was the first restart after the NDS was restarted?). So data was being written to a future gps time.
Kiwamu had problems with testpoints and trends and contacted me. I tracked down the gps offset and fixed it, but the original daqd process only started once successfully, after that is was segfault, core dump non-stop. I tried Alex's rebuilt daqd (along with putting the gps offset to the correct value for it), and it worked. Test points, trends, excitations were checked at the point and found working.
I still do not understand the underlying causes of all these segmentation faults with both the old and new daqd codes. Alex has suggested some new open mx drivers be installed today.
Looks like there was a mysterious loss of data overnight; since there's nothing in the elog I assume that its some kind of terrorism. I'm going to call Rolf to see if he can come in and work all night to help diagnose the issue.
We wish to have roughly 2 dBm of output power on each line coming out of the RF distribution box. So I adjusted the attenuators inside the box to get this.
I also looked at why the 2x output looked so distorted and found that the input power was around 17 dBm whereas the maximum allowed (as per the datasheet of Minicircuits MK-2) is 15dBm. So I increased the attentuation on its input line to 5dBm (up by 2dBm) The input power levels are around 14.6dBm now and the distortion has come down considerably. However the net output on the 2x lines is now down to 0.7dBm. We will have to amplify this if we need more power.
The schematic and the power output are now like this:
New noise spectra of the green locking have been updated.
The plot below shows the in-loop noise spectra when the beat signal was fedback to ETMX.
The rms noise integrated from 0.1 Hz to 100 Hz went down to approximately 2 kHz.
The red curve was taken when the beat was controlled only by a combination of some poles sand zeros on the digital filter banks. The UGF was at 40Hz.
This curve is basically the same as that Koji took few weeks ago (see here). Apparently the rms was dominated by the peaks at 16 Hz and 3 Hz.
The blue curve was taken when the same filter plus two resonant gain filters (at 16.5 Hz and 3.15 Hz) were applied. The UGF was also at 40Hz.
Due to the resonant gain filter at 16.5 Hz, the phase margin became less, and it started oscillating at the UGF as shown in the plot.
As per Kiwamu's request I made a light touch to the input steering and the mode matching lens.
Here V_ref and V_trans are C1:IOO-MC_RFPD_DCMON and C1:IOO-MC_TRANS_SUM, respectively.
Result: Visibility = 1 - V_ref(resonant) / V_ref(anti_reso) = 1 - 0.74 / 5.05 = 85%
What has been done:
Larisa Thorne received 40m lab specific, basic safety training. She will attend P. King's Basic Laser Safety Training Session tomorrow.
The mechanical assembly of RF distribution box is 99% complete. Some of the components may be bolted to the teflon base plate if needed.
All RF cables and DC voltage supply lines have been installed and tested. I removed the terminal block which was acting as a distribution box for the common zero voltage line. Instead I have used the threaded holes in the body of each voltage regulator. This allows us to keep the supply lines twisted right up to the regulator and keeps the wiring neater. The three regulator bodies have been wired together to provide a common zero potential point.
I did a preliminary test to see if everything is functioning. All units are functioning well. The output power levels may need to be adjusted by changing the attenuators.
The 2x frequency multiplier outputs are not neat sine waves. They seem to produce some harmonics, unlike the rest of the components.
I will post the measured power output at each point tomorrow. The RF power meter could not be found in the 40m lab. We suspect that it has found its way back to the PSL lab.
Frank is recommending these PhaseTrack-210 as phase stable low loss rf coax cables.
I have been editing and reloading the c1ioo model last two days. I have restarted the frame builder several times. After one of the restarts on Sunday evening the fb started having problems which initially showed up as dtt reporting synchronization error. This morning Kiwamu and I tried to restart the fb again and it stopped working all together. We called Joe and he fixed the fb problem by fixing the time stamps (Joe will add details to describe the fix when he sees this elog).
The following changes were made to c1ioo model:
- The angular dither lockins were added for each optics to do the beam spot centering on MC mirrors. The MCL signal is demodulated digitally at 3 pitch and 3 yaw frequencies. (The MCL signal was reconnected to the first input of the ADC interface board).
- The outputs of the lockins go through the sensing matrix, DOF filters, and control matrix to the MC1,2,3 SUS-MC1(2,3)_ASCPIT(YAW) filter inputs where they sum with dither signals (CLOCK output of the oscillators).
- The MCL_TEST_FILT was removed
The arm cavity dither alignment (c1ass) status:
- The demodulated signals were minimized by moving the ETMX/ITMX optic biases and simultaneously keeping the arm buildup (TRX) high by using the BS and PZT2. The minimization of the TRX demodulated signals has not been successful for some reason.
- The next step is to close the servo loops REFL11I demodulated signals -> TMs and TRX demodulated signals -> combination of BS and PZTs.
The MC dither alignment (c1ioo) status:
- The demodulated signals were obtained and sensing matrix (MCs -> lockin outputs) was measured for pitch dof.
- The inversion of the matrix is in progress.
- The additional c1ass and c1ioo medm screens and up and down scripts are being made.
I restarted the elog using the script.
For some reason, Kiwamu forced us to change the MC servo electronics today. We are now combining it with the FSS box.
The MC Servo by itself was locking by just driving the NPRO PZT. Becuase of the ~30 kHz mechanical resonances of that system, our badnwidth is limited. To get higher bandwidth, we can either use a wideband frequency shifter like the AOM or just use the ole FSS combo of PZT/EOM. The old MC servo was able to get 100 kHz because it used the AOM.
So we decided to try going through the FSS box. The MC servo board's FAST output now goes into the IN1 port (500 Ohm input impedance) of the TTFSS box. This allows us to use the FSS as a kind of crossover network driving the PZT/EOM combo.
At first it didn't work because of the 5V offset that Jenne, Larisa, Koji, and Suresh put into there, so I cut the wire on the board that connected the power to the summing resistor and re-installed the MC Servo board.
We also removed the old Jenne-SURF 3.7 MHz LP between the MC mixer and servo. Also removed the Kevin-box (1.6:40) stuck onto the NPRO PZT.
We have yet to measure the UGF, but it seems OK. The PCDRIVE is too high (~5-6V) so there is still some high frequency oscillation. Needs some investigation.
* To get the FSS SLOW servo to work (change NPRO temperature to minimize PZT drive onto NPRO) I set the setpoint to 5V in the script so that we operate the FSS box output at 5V mean. I set the threshold channel to point to MC_TRANS_SUM instead of RC_TRANSPD. I also had to fix the crontab on op340m so that it would point to the right scripto_cron script which runs the FSSSlowServo, RCThermalPID.pl, etc. I also had to fix scripto_cron itself since it had the old path definitions and was not loading up the EpicsTools.pm library.
** Also, I was flabbergasted by the dog clamping on the last turning mirror into the MC. Barely touching the mount changes the alignment.
Most of the RF cables required for the box are done. There are two remaining and we will attend to these tonight.
We expect to have finished the mechanical assembly by Sunday and start a quality test on Monday.
Frank put his low noise preamp info here.
I suggest that we build these (using Altium) but replace the cheapo transistors with the high class MAT03 matched BJT pair from Analog Devices.
This will allow us to have a pre-amp better matched to the noise of the mixers down to low frequency.
Today I was working on RF distribution box.
So far I almost finished to electronically isolate voltage regulators from the box wall by inserting mica sheet, sleeve, and washers.
The problem I found is the resistance between wall and the voltage regulator is order of M ohms
I checked my isolation (mica sheet and sleeve and washer) but there is no problem there.
But I found that the power switch is not completely isolated from the wall.( around 800 kohm)
and that the resistance between the regulator and the wall is smaller for the regulator closer to the power switch
and greater for the regulator less closer to it.
So I think we need to put washer or sleeve to isolate the powersitch electronically from the box wall.
Suresh or I will fix this problem
[ To Suresh, I can finish the isolation when I come tomorrow. Or you can proceed to finish isolation.]
The plot below shows how the f2p filters work.
At -2 min I turned on the f2p filters.
The f2p measurements are done on ETMX and ITMX with the real time lockin systems.
The f2p measurements are done on ETMX and ITMX with the real time lockin systems.
I don't explain what is the f2p measurement in this entry, but people who are interested in it can find some details on an old elog entry here or somewhere on DCC.
So far the resultant filters looked reasonable compared with the previous SRM f2p filters.
- backgrounds -
Some times ago I found that the coils on ETMX had not been nicely balanced, and it made a POS to angle coupling when I tried green locking (see here).
In addition to that, accuracy of A2L kind of measurement including the dithering techniques depend on how well the coils are balanced. Therefore we need to balance the coils basically at all the suspended optics.
There used to be a script for this particular purpose, called f2praio.sh. This script does measure the imbalances and then balance the coils.
However this time I used the realtime lockin system to measure the imbalances instead of using the old f2p script.
One of the reasons using the real time system is that, some of the ezca and tds commands for the old script don't work for some reasons.
Therefore we decided to move on to the real time system like Yuta did for the A2L measurement a couple of months ago.
The f2p measurement finally gives us parameters to generate a proper set of filters for POS and also the coil gains. We apply those filters and the gains in order to eliminate the POS to angle coupling and to balance the coils.
- results -
The followers are the resultant filters and coil gains.
The plots below show new f2p filters according to the measurement.
ITMX (assuming pendulum POS has f0 = 1 Hz and Q = 1)
ULPOS fz = 1.009612 Qz = 1.009612
URPOS fz = 1.125965 Qz = 1.125965
LLPOS fz = 0.873725 Qz = 0.873725
LRPOS fz = 0.974418 Qz = 0.974418
ETMX (assuming pendulum POS has f0 = 1 Hz and Q = 1)
ULPOS fz = 1.055445 Qz = 1.055445
URPOS fz = 1.052735 Qz = 1.052735
LLPOS fz = 0.944023 Qz = 0.944023
LRPOS fz = 0.941600 Qz = 0.941600
C1:SUS-ETMX_LLCOIL_GAIN = 1.07233
The precision of the coil gains looked something like 1% because every time I ran the measurement script, the measured imbalances fluctuated at this level.
The precision of the filter gain at DC (0.01 Hz) could be worse, because the integration cycles for the measurement are fewer than that of the coil gains done at high frequency (8.5 Hz).
Of course we can make the precisions by increasing the integration cycles and the excitation amplitudes, if we want to.
We updated the c1ass model to include the BS. We removed the dither excitation of the PZTs. PZT control goes to epics. To do this, modified the /cvs/cds/caltech/target/c1iscaux/PZT_AI.db file. We basically have it sum both the existing epics slider and our new output from c1ass.
More importantly we updated the color scheme.
We compiled and tested the Dolphin and RFM which work.
I should note we can't figure out why testpoints are not working properly with just this model. Alex and Joe spent well over an hour trying to debug it to no success. Current workaround is to add what channels you want from c1ass to the DAQ recording. Other testpoints on other models appear to be working.
[Koji and Kiwamu]
We took transfer functions (TF) from the angle excitations at ETMX and ITMX to the green beat note signal (i.e. angle to length TF).
It turned out that the coupling from ETMX_PIT is quite large.
I wonder how f2p of the ETMX changes this coupling. We'll see.
The plot above shows a set of the transfer functions from the angle excitation to the green beat note.
Note that the y-axis has not been calibrated, it is just a unit of counts/counts.
You can see that the TF from ETMX_PIT to the beat (red cruve) is larger than the others by about a factor of 10 over most of the frequency range.
This means that any PIT motions on ETMX can be coupled into the green beat signal somewhat over the wide frequency range.
It looks having a resonance at 1.5 Hz, but we don't exactly know why.
At that time the coil gains on only ITMX were tuned by applying f2p filters, but ETMX wasn't because of a technical reason coming from epics.
- - - - measurement conditions
* PSL laser was locked to X arm by feeding back the IR PDH signal to MC2.
* the green laser was locked to Xarm as usual.
* took the green beat note signal (approximately 0 dBm) into Rana's MFD with the cable length of about 6 m.
* the output from the MFD was connected to XARM_COARSE channel without a whitening filter.
* excitation signal was injected into either ASC_PIT or ASC_YAW. The excitation was Gaussian noise with frequency band of 10 Hz and amplitude of 300 counts.
* only ITMY had the f2p filters, which balance the coil gains all over the frequency.
I talked to Alex today and had two things fixed:
First the maximum length of filter names (in the foton C1SYS.txt files in /chans) has been increased to 40, from 20. This does not increase EPICS channel name length (which is longer than 20 anyways).
This should prevent running into the case where the model doesn't complain when compiled, but we can't load filters.
Additionally, we modified the feCodeGen.pl script in /opt/rtcds/caltech/c1/core/advLigoRTS/src/epics/util/ to correctly generate names for filters in all cases. There was a problem where the C1 was being left off the file name when in the simulink .mdl file the filter was located in a box which had "top_names" set.
- more precise F2P measurement and modify lockin simlink model (Kiwamu)
- run C1ASS to check it (Valera)
- take care of CDS (Joe)
- MC mode matching (Jenne/Koji)
- RF stuff (Suresh)
- mode matching for doubling crystal at PSL table (low priority)
- OPLEV (low priority)
- update the noise spectra of green locking
- make noise budgets
As one of the trouble shooting steps for the daqd (i.e. framebuilder) I rebuilt the daqd executable.
As one of the trouble shooting steps for the daqd (i.e. framebuilder) I rebuilt the daqd executable. My guess is somewhere in the build code is some kind of GPS offset to make the time correct due to our lack of IRIG-B signal.
The actual daqdrc file was left untouched when I did the new install, so the symmetricom gps offset is still the same, which confuses me.
I'll take a look at the SVN diffs tomorrow to see what changed in that code that could cause a 300000000 or so offset to the GPS time.
DTT stopped working for recent data. An 'ls' in the frames/full/ directory reveals:
drwxr-xr-x 2 controls controls 258048 Feb 3 12:26 9807
drwxr-xr-x 2 controls controls 258048 Feb 4 16:13 9808
drwxr-xr-x 2 controls controls 262144 Feb 5 19:59 9809
drwxr-xr-x 2 controls controls 258048 Feb 6 23:46 9810
drwxr-xr-x 2 controls controls 258048 Feb 8 03:33 9811
drwxr-xr-x 2 controls controls 262144 Feb 9 07:19 9812
drwxr-xr-x 2 controls controls 253952 Feb 10 11:06 9813
drwxr-xr-x 2 controls controls 266240 Feb 11 14:53 9814
drwxr-xr-x 2 controls controls 266240 Feb 12 18:39 9815
drwxr-xr-x 2 controls controls 266240 Feb 13 22:26 9816
drwxr-xr-x 2 controls controls 262144 Feb 15 02:13 9817
drwxr-xr-x 2 controls controls 253952 Feb 16 05:59 9818
drwxr-xr-x 2 controls controls 241664 Feb 17 09:46 9819
drwxr-xr-x 2 controls controls 28672 Feb 17 12:22 9820
drwxr-xr-x 2 controls controls 32768 Feb 17 15:06 6663
drwxr-xr-x 2 controls controls 73728 Feb 17 23:39 6664
controls@fb /frames/full $ date
Thu Feb 17 23:39:27 PST 2011
This is the 140 ft. MFD measurement of the VCO phase noise. It is open loop and so should be a good measurement. The RMS is 30 Hz integrated down to 2 mHz.
I don't know why this doesn't agree with Suresh's measurements of the same thing which uses the PLL feedback method.
In BLUE, I also plot the frequency noise measured by using a Stanford DS345 30 MHz func. generator. I think that this is actually the noise of the FD (i.e. the SR560 preamp) and not the DS345. Mainly, it just tells you that the PINK VCO noise measurement is a real measurement.
I calibrated it by putting in a 5 kHz_pp triangle wave on the sweep of the DS345 and counting the counts in DV.
We made a model for the dither angular stabilization system c1ass.mdl. The attached file shows the diagram.
The idea is to dither a combination of 6 optics (ETMs, ITMs, PZTs) at different frequencies and demodulate three PDs (TRX, TRY, REFL11I). Then form the DOFs from demodulted signals, filter, and send each DOF to a combination of optics.
This is enough to get started with arm cavities alignment (we may need to add the BS for the Y arm). More optics and PD can be added as they become available and/or needed.
The DAC for the fast PZT are not connected and have to be commissioned.
I worked a little bit more on optimizing the mode matching to the MC, but it's still not great. I've only gotten a visibility of ~45%, but Koji said that it used to be ~87%. So there is a long way to go. Kiwamu said he can work with the lower-power configuration for a few days, and so my next step will be to measure the beam profile (stick a window in the path, and look at the refl from the window....that way we don't get thermal lensing from transmission through an optic), and redo the mode matching calculation, to figure out where the last lens should actually sit.
So.... Kiwamu and I were concerned (still a little concerned) that ETMY is not damping as nicely as it should be. (It's fine, but the UL rms is ~5, rather than ~1 or less. BURT restores by Kiwamu didn't change anything.) Anyhow, I was heading out to push the annoying ribbon cables more firmly into the satellite adapter board things that are tied to the racks in various places (The back of 1X5 for the corner optics and the end station racks for the ETMs). The point was to push in the ETMY one, but while I was out in the lab and thinking about it, I also gave all of the corner connectors (MC1, MC2, MC3, ITMx, ITMY, BS, PRM, SRM) a firm push.
Kiwamu noticed that when I did this, the Mode Cleaner alignment got a little bit worse, as if the connection to the satellite adapter boards hadn't been great, I pushed the connectors in and the connection got better, but we also got a bit of a DC offset in the MC alignment. Anyhow, the MC_TRANS power went down by ~2, to about the place it had been before Kiwamu adjusted the position of the lens in between the zigzag mirrors. (I don't know if Kiwamu elogged it earlier, but he scooted the lens a teensy bit closer in the optical path to the Mode Cleaner).
To counteract this loss in MC transmitted power as a result of my connector actions, I went back to the PSL table and fiddled with the zigzag steering mirrors that steer the beam from the PSL table over to the mode cleaner. I got it a little better, but it's still not perfect.
Kiwamu has noted that to improve the mode matching into the Mode Cleaner with the new PMC in place, we might have to move the lens which is currently between the zigzag steering mirrors, and put it after the second mirror (so in between the last steering mirror and the pickoff window that sends a piece of the beam over to PSL_POS and PSL_ANG). This will make the waist between MC1 and MC3 tighter.
Moral of the story: To improve IMC mode matching we need to move the last lens closer in the optical path to the mode cleaner waist. Twiddle with zigzag steering mirrors to optimize.
The Distribution box is several steps nearer to completion.
1) Soldered capacitors and DC power lines for four units of the distribution box.
2) mounted all the components in their respective places.
3) Tomorrow we prepare the RF cables and that is the last step of the mechanical assembly.
4) we plan to test both the generator and distributon parts together.
Kevin took a transfer function of the newly assembled PD and noticed that the frequency has shifted to 14.99 freom 11. MHz.
We needed to find the current RLC combination. So we removed the ferrite core from L5 rendiring it to its aircore value of 0.96/muH. We then used this to find the Capacitance of the PD (117pF)
We used this value to compute the inductance required to achieve 11.065MHz which turned out to be 1.75microH.
This was not reachable with the current L5 which is of the type 143-20J12L (nominal H=1.4 micro Henry).
We therefore changed the inductor to SLOT 10 -3-03. It is a ferrite core, shielded inductor with a plasitc sleeve. Its nomial valie is 1.75 microH
We then tested the DC output to see if here is a response to light. There was nonel. l
The problem was traced to the new inductor. Surprisingly the inductor coil had lost contact with the pins.
I then replacd the inductor and checked again. The elecronics seems to work okay.. but there is a very small signal 0.8mV for 500microW.
There seems to be still something wrong with the PD or its electronics.
[Larisa, Kiwamu, Steve and Suresh]
We continued the labeling of video cables. All exiting cables which are going to be used used in the new scheme have been labeled.
We also labeled the cables running from the video mux to the TV monitors in the computer room. Some of these will be removed or reallocated.
We will continue next Wednesday (after the meeting) and will lay cables that are most urgently required.
Could not load filters into the C1:SUS-ETMX_LOCKIN1_SIG filter bank.
Apparently the filter bank name was too long. I'm not sure why this isn't caught by the real time code generator, I'm planning on asking Alex and Rolf about it today.
Reduce the name of the components. Basically LOCKIN1 needs to become something like LOCK1 or LIN1.
In related news, it looks like the initial filters are hard coded to be 2048 Hz. Given that they start out empty they won't cause things to break immediately, and if you're editing the file you can update the rate as you add the filter. I'll also bring this up with Alex and Rolf and see if the RCG can't be more intelligent about its filter generation.
I modified the core/advLigoRTS/Makefile to once again place the startc1SYS and killc1SYS scripts in the scripts/FE/ directory.
It had been reverted in the SVN update.
I've modified the rc.local file to run the IOC codes as controls, which means they no longer write root permission log files on startup.
The awgtpman, which was the other permission issue with the start scripts, is started by a run script now. This new version seems to be content to keep the permissions of the current log file, which is set to controls.
This should prevent the issue of sudo wiping your path environment variable for just that command. (Try "sudo which burtwb" versus "which burtwb" for example). This apparently a security feature of sudo.
If you should happen to use sudo to run a start script, the easiest solution to fix the permissions is just got to the target directory (type "target") and run "sudo chown controls:controls -R *" on one of the workstations (the front ends don't handle the groups properly at the moment).
This should allow the scripts to properly use burtrb and burtwb to write and backup burt files.
. mode matching for MC (Jenne/Koji)
. mode matching for doubling crystal on PSL table (Suresh/Koji)
. f2p adjustment (Kiwamu)
. fix daq and CDS issues (Joe)
. increase oplev gain (low priority)
. make ITMY camera nicer (Steve)
. c1ass simlink model (Valera/Joe)
. Bounce Roll notches (Suresh)
. align everything (at first green beam, then X arm cavity and finally IR beam)
. update the noise spectrum of the green locking
. estimate the noise from angle to length coupling
Valera pointed out the OPLEV SUM channels were incorrect. We changing the optical level sum channel to _OPLEV_SUM when it should have been OL_SUM. This has been fixed in the activateDAQ.py script.
Here is the followup on Jenne's February 14th, 2011 update on the quantum efficiency measurements of WFS2.
Attached is a PDF of my calculations, based on measurements ranging between 0-25 degrees in 5 degree increments.
The graph at the bottom plots these angles versus the calculated quantum efficiency at each point and the responsivity. Since quantum efficiency and responsivity only differ by a factor of some natural constants (lamda, e, h, c), I used a graph with two vertical axes, because the points would be plotted at essentially the same location if quantum efficiency (%) and responsivity (Amps/Watts) were graphed on two separate plots.
The calculated values for quantum efficiency based on my measurements (labelled "ExpAverage") were pretty close to what Jenne had calculated in earlier attempts, which was around 60%. Just to test, I compared my quantum efficiency result against the calculation of quantum efficiency using the responsivity value for silicon, 0.5 Amps/Watt, which is labelled as "Spec". Comparison of "ExpAverage" and "Spec" shows that they differ by only about 2%, so I conclude that the theoretical quantum efficiency calculated using a given responsivity agrees with my measurement-based experimental result.
[Jenne and Kiwamu]
This time we aligned the vertical angle (not the translation) of the IR beam so that the transmitted light from BS shoots the center of ETMY.
The idea is to use ETMY as a beam pointing reference instead using IP_ANG, assuming the translation is not so bad.
As a result it looks like we are wining. A quick A2L test on ITMX_PITCH showed a small off-centering at sub-milimeter level.
We are concluding that the initial beam after PZT2 had been pointing downward somehow.
Before doing this whole job, we checked the spot shape on IP_POS to see if the beam is clipped or not. It was a round shape, which means no clipping around MMT.
But on the other hand, the spot on IP_ANG had been clipped more than half of its bottom as Suresh reported on his elog (see here).
I found that this clipping is able to be fixed by moving the beam angle upward. I guess the clipping happened at one of the steering mirror in the ETMY chamber.
According to these information, we imagined that the beam was somehow pointing downward after PZT2.
So we started aligning the beam by touching only PZT2 for vertical direction. Then we found a beam spot on ETMY's suspension frame, and brought it to the center.
Then we aligned BS and X arm for this new beam axis. The it resulted a small off-centering on pitch.
Once the MC fully gets back, we will examine the TRX degradation with this configuration.