Summary for the week ending June 26th. (Number of elog entries = 53)
The slow readback of the ETMX side seems to also have something flaky and bi-stable. This is not an issue for damping, but it disables the SIDE watchdog for ETMX and makes it unsafe if we accidentally use the wrong damping sign.
Since the MC1 LRSEN channel is not wasn't working, my input matrix diagonalization hasn't worked today wasn't working. So I decided to fix it somehow.
I went to the rack and traced the signal: first at the LEMO monitor on the whitening card, secondly at the 4-pin LEMO cable which goes into the AA chassis.
The signal existed at the input to the AA chassis but not in the screen. So I pressed the jumper wire (used to be AA filter) down for the channel corresponding to the MC1 LRSEN channel.
It now has come back and looks like the other sensors. As you can see from this plot and Joe's entry from a couple weeks ago, this channel has been dead since May 17th.
993190663 = free swinging ringdown restarted again
I used scripts/SUS/freeswing-all.csh to give the optics a kick and then turn off their watchdogs and collect the free swinging data. Final script end time = 993173551. Start taking data ~ 993173751
I had to fix up the script a little: it had amateur stuff in there, such as undefined variables.
It still doesn't work that well. On the new Ubuntu workstations, pianosa, it fails by just not setting some of the EPICS variables using the EZCA stuff.
On Allegra, it failed on ~1 out of 10 commands by returning "epicsThreadOnce0sd epicsMutexLock failed" ???
On Pianosa, it sometimes says, instead, "epicsThreadOnceOsd: pthread_mutex_lock returned Invalid argument.". Ah...now I understand?
epicsThreadOnceOsd: pthread_mutex_lock returned Invalid argument.
So finally, I had to run the script on op340m to get it to actually run all of its commands. That's right; I used a 15 year old Solaris 9 Blade 150 because none of our fancy new Linux machines could do the job reliably.
Fixing our EZCA situation is a pretty high priority; if the locking scripts fail to run ~1 command every hour its going to completely derail the lock acquisition attempts.
If you want to use the IFO tonight, just run the script again on op340m again when you're done.
I have updated the scripts/SUS/peakFit/ directory so that it now finds the SUS input matrix coefficients in addition to just finding the free-swinging peaks.
The attached PDF shows how much rejection of the unwanted DOFs we get between the existing diagonal input matrix and this new empirical matrix. Previously, the decoupling was only a factor of a few for some of the modes. Now the decoupling is more like orders of magnitude (at least according to this calculation). It will be worse when we load it and then try another free swinging run. However, the fact that the suppression can be this good means that the variation in the coefficients at the ~hours time scale is at least this small (~< 0.1%)
That's the basic procedure, but there are a lot of important but mainly technical details:
I'll set the optics to be aligned and then swing tonight.
[Rana / Kiwamu]
Last Friday we did several things for MC :
- aligned the incident beam to MC
- increased the locking gain by 6 dB and modified the auto-locker script accordingly
- improved the alignment of the beam on the MC_REFLPD photo diode
In the beginning of the work, we wanted to know what RF frequency components are prominent in the reflection from MC.
Since the WFS circuits are capable for two RF notches, we wanted to determine which frequencies are appropriate for those notches.
So for the purpose we tried searching for unwanted RF components in the reflection.
However during the work, we found several things that needed to be fixed, so we spent most of the time for improving the MC locking.
- Alignments of the incident beam
At the beginning, the reflection from MC was about 2.2 in C1:IOO-REFLDC and the lock of MC had been frequently unlocked.
This situation of high reflection seemed to be related to a work done by Suresh (#4880).
Rana went to the PSL table and tweaked two input steering mirrors in the zig-zag path, and finally the reflection went down to ~ 0.8 in C1:IOO-REFLDC.
This work made the lock more robust.
- Change of the locking gain
After the alignment of the incident beam, we started looking at the time series of the MC_REFLPD signal with an oscilloscope as a start point.
What we found was a significant amount of 30 kHz components. This 30 kHz oscillation was thought be a loop oscillation, and indeed it was so.
We increased the loop gain by 6 dB and then the 30 kHz components disappeared successfully.
So the nominal locking gain of MC is now 11 dB in C1:IOO-MC_REFL_GAIN. The auto locker script was also modified accordingly.
- RF components in the MCREFL signal
After those improvements mentioned above, we started looking at the spectrum of the MCREFL PD using the spectrum analyzer HP8590.
The 29.5 MHz component was the biggest components in the spectrum. Ideally this 29.5 MHz signal should be zero when MC is locked.
One possible reason for this big 29.5 MHz signal was because the lock point was off from the resonant point.
We tweaked the offset in the MC lock path using a digital offset, C1:IOO-MC-REFL_OFFSET.
We found an offset point where the 29.5MHz signal went to the minimum, but didn't go to zero.
(works to be done)
So it needs some more works to investigate the cause of nonzero 29.5 MHz signal as well as investigation of what RF components should be notched out.
A good start point would be writing a GPIB interface script such that we can get the spectra from HP8590 without any pains.
I was able to measure the sensing matrix in the PRMI configuration.
The results will be posted later.
The attached plots show the location of the ~29.5 MHz pole and the 59 MHz notch for each quadrant of the WFS1 Sensor head.
As may be seen from the above table, these frequencies will need to be adjusted in some cases.
From the plots we can see that, when there is no attenuation set on the attenuator AT65-0263 (ref D990249-A), the MAX4107 oscillations are seen in Q2,Q3,Q4 quadrants at around 200 MHz.
Rana suggested, from his previous encounter with this circuit, that the solution is to remove the second MAX4106 and the attenuator on the RF line to avoid this oscillation.
A look at the circuit board shows that some of the inductors have not been mounted. That explains the presence of only one notch though the schematic shows two.
What I did today.
1. I tried to align the IR input beam by aligning the two mirrors, to couple input light into the fibre.
2.I was unsuccessful for a long time even though I tried a lot of tricks.
3. I also tried to use the optical fault locator to superpose the IR beam spot onto the beam spot of the other laser to facilitate effective coupling.
4.But the crucial point was to superpose the input beam path in the perfect direction of the output beam path and not just the beam spot.(the input cone and the output cone are perfectly aligned).
5.After one whole day of trial and thought, I managed to couple light into the fibre, and saw the output beam spot on the screen-camera-monitor set-up which we had arranged. Eurekka !!;)
6.I then used a power meter to measure the input beam power and the output beam power.
7.It was a disappointing 2% . I had read in project reports of many students of a 20% success.
8.After a lot of subtle tweaking of the mirrors using the knobs, I managed to increase the percentage of output beam to 12%.
9. This is a workable level.
10.A day of lot of new learning! Pictures of the setup are attached.:)
When I try to get minute trend, it says "word too long".
I put labels on the pair of beam steering mirrors which are at the output end of the PSL table. I had changed one of these mirrors (elog) and Jenne had changed the other (elog). This was at about 3PM today
I just learned from Kiwamu that this has messed up the MC alignment.
Today Ishwita, Sonali, and I completed basic laser safety training with Peter King. I completed the Laser Safety Quiz and have turned in my certificate sheet.
I just need to turn in a signed copy of the Lab Safety Checklist to SFP (which I can now have signed by Koji after completing the course).
Steve and I have removed the TT mirror from the clean box. It is now on the small optical table in the lab that I have been working on. Thanks to Steve, all of the mechanical components for the horizontal displacement measurement experiment are compiled and on the small optical table. Here is a photo of the small optical table with the gathered components.
The plan is to attach the slider and the shaker directly to the black mounting plate. On the slider, we we then place the smaller black mounting plate (with the lip). The lip will attach to the shaker. We know exactly where to drill and everything is lined up. The shaker will be placed on the smaller black mounting plate (with the lip). The assembly will begin on Monday.
Here is a photo of the planned set-up for the shaker and the horizontal slider + mounting base.
ITMY gets new Tamron M118FM50 that has improved close focusing. It is a small fixed focal length camera so the video tube cover can be put on.
The Watec LCL-902K 1/2" ccd camera was losing it power supply voltage because of bad connection. It was replaced.
The I-P curve was measured again, but this time in a lower current range of 1.0-1.9 [A].
The old days the NPRO ( inside the MOPA ) was running ~1.7A 500 mW
Lightwave Laser Head M126-1064-700 sn238, mounted on full size Al base and side heat sink on
Controller 125/126 Smart Supply sn 201M
The PRM sus damping restored. C1:SUS-PRM_SDPD_VAR is still 20-30mV and going up. Side gain turned on. This pulled it down to 5-8 mV
Why is the side osem sensing voltage 4.4V ? It can not be higher than ~2.4V.......something is rotten in the state of Denmark?
Edit by KI:
It's because Valera increased the transimpedance gain of the PRM SIDE OSEM to match the signal level to the new ADC range (#3913 ).
I have updated the TT suspension wiki to include a new page on my transfer function model. In this new page, an introduction and analysis of my transfer function (including a comparison of the transfer functions for a flexibly- and rigidly-supported damper) are included. This page contains linear and logarithmic bode plots. Here is a link to the transfer function page.
I have also updated my photosensor page on the TT suspension wiki so that the experimental data points in my current versus voltage plot are plotted against the curve provided by the Hamamtsu data sheet. I have also included an introduction and analysis for my mini-experiment with the forward voltage and forward current of the LED. Here is link to the photsosensor page.
The beam profile of the LWE (LightWave Electronics) NPRO was measured.
Mode matching telescopes will be designed and setup soon based on the result of the measurements.
Here is a plot of the measured beam profile.
The measurement was done by using Kevin's power attenuation technique (#3030).
An window was put just after the NPRO and the reflected beam was sampled for the measurement to avoid the beam scan saturated.
Sonali, Ishwita, and another anonymous SURF saved the long-lasted water shortage of the 40m
The plot below is the latest I-P curve.
Based on the measurement and some thoughts, I decided to run this laser at about 1.8 [A] which gives us a middle power of ~ 360 [mW].
In the 40m history, the laser had been driven at 2.4 [A] in years of approximately 2006-2009, so it's possible to run it at such a high power,
but on the other hand Steve suggested to run it with a smaller power such that the laser power doesn't degrade so fast.
The laser controller handed from PK (#4855) was used in this measurement.
The nominal current was tuned to be 1.8 [A] by tuning a potentiometer on the laser head (see page.18 on the manual of LWE).
There was a huge bump around 1.4 [A] and sudden power drop at 1.48 [A] although I don't know the reason.
I found some DQ channels (e.g. SENSOE_UL and etc.) for C1SUS haven't been activated, so I ran activateDQ.py.
Then I restarted daqd on fb as usual. So far the DQ channels look working fine.
I found the PMC unlocked. Koji noticed that the FSS Slow Actuator Adjust was railed at the positive end of the slider. I set it close to zero, and relocked the PMC. The FSS slow loop servo is doing its thing, and the PMC and MC are now locked.
I recorded a burt snapshot of these settings: /opt/rtcds/caltech/c1/burt/autoburt/snapshots/2011/Jun/23/21:40
We have fixed the counts-to-micron (cts2um) calibration for the suspension sensor filters. Each suspension sensor filter bank (e.g. ULSEN) has a "cts2um" calibration filter. These have now been set with the following flat gains:
40 V 10^3 um um
-------- * -------- = .36 --
2^16 cts 1.7 V ct
The INMTRX was also fixed with proper element values:
This was done for all core optic suspensions (BS, PRM, SRM, ITMX, ITMY, ETMX, ETMY).
For some reasons foton's deafault sample rate is NOT correct when it runs on the CentOS machines.
It tries to setup the sample rate to be 2048 Hz instead of 16384 Hz until you specify the frequency.
To avoid an accidental change of the sample rate,
running foton on CentOS is forbidden until any further notifications.
Run foton only on Pianosa.
Additionally I added an alias sentence in cshrc.40m such that people can not run foron on CentOS (csh and tcsh, technically speaking).
Below is an example of raw output when I typed foron on a CentOs machine.
DO NOT use foton on CentOS
Rod Luna picked up these computers for Larry Wallace yesterday: Dell Inspiron 530, Dell Dimension 4600 and SunBlade 1000
Access to the north side of the PSL table is blocked by the 8" beam guard. This opens the beam pathways between them.
All the suspensions are bad until you fix them. But, ... there is a script which can be used to diagnose them today:
I was trying to measure the sensing matrix in the PRMI configuration, but basically gave up.
It is mainly because the lock of PRMI wasn't so stable and it didn't stay locked for more than a minute.
It looked like an angular motion fluctuated a lot around 1- 3 Hz. The beam spot on the AS camera moved a lot during the lock.
I have to figure out who is the bad suspension and why.
June 22-June 24:
1.Coupling light into fibre at the ETMY.
2.Routing of the fibre to the PSL table.
June 27-June 30:
1.PSL optical table layout sketching.
2.Combining the PSL beam with fibre output onto a BS and then superpose them on a New Focus 1611 PD.
July 5-July 8:
1.Conversion of the PD output to voltage using MFD(Mixer Frequency Discriminator).
2. Report writing.
July 7: 5:00 pm: 1st Report Due.
July 11-July 22:
1.Locking Y-arm to PSL.
2.Setting up the feedback loop using the MFD output as the error signal and acting on the AUX laser frequency.
July 25-Aug 5:
1.Y-Arm cavity characterisation.
Measurement of the transmission of IR and green light through the cavity.
To obtain FSR, Finesse,Loss of the Cavity, Visibility, Transverse Modes(g-factor, astigmatism), Reflectivity, Q-factor.
3.Report and abstract writing.
Aug 1: 5:00 pm: 2nd Report and absract due.
Preparation for talk and seminar.
I put a paper Peet's bag with half of the Mini-Moos into George.
I have shifted the Jenne laser back to the small table where we do RF PD characterisation (RFPD table). I found several 25pin D-type connector cables, connected them in tandem and am using that to power the WFS2 sensor head at the RFPD table.
The set up is ready for looking at the RF response of the WFS sensors. Will continue tonight.
Kiwamu and I have started to put together a vent plan on the 40m wiki:
We will keep working on this (there's still a *lot* to fill in), but please help fill in the plan by adding questions, answers, procedures, preparations, etc.
NOTE: The potentiometers on the bread board circuit box (the one I have been using with the signal generator, DC power, LED displays, and pulse switches) is BROKEN!
The potential across terminals 1 and 2 (also 2&3) fluctuates wildly and there dial does not affect the potential for the second potentiometer (the one with terminals 4, 5, and 6).
This has been confirmed by Koji and Jaimie. PS I didn't break it! >____<
NEVERTHELESS, using individual resistors and the 500 ohm trim resistor, I have managed to get the current versus forward voltage plot for the Hamamatsu L9337 Infared LED
The sensing matrix was measured in the DRMI configuration for the first time.
The measurement was done by an automatic script and the realtime LOCKIN module built in the c1lsc model.
The resultant matrix is still too primitive, so I will do some further analysis.
(Measurement of sensing matrix)
The quantities we want to measure are the transfer functions (TFs) from displacement (or change in optical phase) of each DOF to sensors in unit of [counts/m].
So essentially the measurement I did is the same as the usual TF measurement. The difference is that this measurement only takes TFs at a certain frequency, in this case 283 Hz.
The measurement goes in the following order :
(1) Lock DRMI
(2) Shake an optic of interest longitudinally with an amplitude of 1000 counts at 283.103 Hz, where no prominent noise structures are present in any spectra of the sensor signals.
(3) Put a notch filter at the same frequency of 283.103 Hz in each DOF (MICH, PRC and SRC) to avoid unwanted suppression due to the control loops.
(This technique is essentially the same as this one, but this time the control loops are shut off only at a specific frequency )
The notch filter I put has a depth of 60 dB and Q of 20. The filter eats the phase of ~10 deg at 200 Hz, which still allow servos to run with a high UGF up to 200Hz.
(4) Take the output signal from a signal port of interest (i.e. REFL11_I, etc.,) and then put it into the realtime LOCKIN module.
(5) Measure the resultant I and Q signals coming out from the LOCKIN module.
(6) Repeat the procedure from (2) through (5) for each optic and sensor.
Again, the resultant sensing matrix is still primitive, for example the optic-basis should be converted into the DOF basis.
The values listed in the matrix below is the absolute values obtained by operation of sqrt( I^2 + Q^2) plus the polarity according to the output from I and Q of LOCKIN.
Therefore they still contain the actuator response, which is not desired. i will calibrate them into [counts/m] later by using the calibration factor of the actuator responses.
All the raw data showed the relative phase between I and Q either ~ 127 deg or ~ -53 deg.
In my definition, the one has 127 deg is plus polarity and the one has -53 deg is minus polarity.
Technically speaking the polarity depends on the polarity of the actuator and also the direction of the actuator against the DOFs.
Without any excitation the absolute values fluctuated at about 10-4 - 10-5, so the excitation amplitude was big enough to observe the sensing matrix.
Though, I still need to estimate the statistical errors to make sure the SNR is reasonably big.
Fig.1 Measured sensing matrix from optic to sensors.
(Things to be done)
- convert the optic-basis (i.e. BS, ITMs, PRM and SRM) to the DOF-basis (i.e. MICH, PRC and SRC) so that the matrix is understandable from point of view of the interferometer control.
- estimate the optimum demodulation phase for each DOF at each sensor port.
- add some statistical flavors (e.g. error estimations and so on.)
- edit the script such that it will keep watching the ADC overflows and the coherence to make sure the measurement goes well.
- add some more signal ports (e.g. REFL55, POY55 and etc.)
- compare with an Optickle model
The result will be updated later.
This is the new hot air station for the 40m lab.........
Peter King came over to the 40m with a laser controller and gave it to us.
We will test it out with the LightWave NPRO, which was used for MOPA.
I started on the 16th with a very intense lab tour & was fed with a large amount of data (I can't guarantee that I remember everything....)
Then... did some (not much) reading on filters since I'm dealing with seismic noise cancellation this summer with Jenne at the 40m lab.
I'll be using the Streckeisen STS-2 seismometers & I need to use the anti aliasing filter board that has the 4 pin lemo connectors with the seismometers & its boxes that require BNC connectors. I spent most of the time trying to solder the wires properly into the connectors. I was very slow in this as this is the first time I'm soldering anything.... & till now I've soldered 59 wires in the BNC connectors....
I have made my transfer function model and posted it to the suspension wiki. Here is the link to my model!
Bode Plot Model
Please let me know if there need to be any adjustments, but I have posted the bode plots, a model image, and an explanation of why I think it's right! ^ ___^ V
I am currently working on the photo sensor circuit for the displacement detector. So far, I have gotten the infared LED to light up! ^ ___^ V
I am now trying to get a plot of forward voltage versus current for the LED. HOPEFULLY it will match the curve provided in the LED datasheet.
I'm using the bread board circuit box and when I'm not working at the bench, I have signs posted. PLEASE DO NOT REMOVE THE CONNECTIONS! It is
fine to move the bread board circuit box, but please do not disturb the connections > ____<
Here is a photo of the workspace
1. Collimation of a beam.
2. Coupling of the IR light at the ETMY table to a fibre.
I am now measuring the sensing matrix in the DRMI configuration.
A goal of tonight is to measure the sensing matrix as a test of the script.
Last night I was making a script which will measure the sensing matrix using the realtime LOCKIN module.
The script is a kind of expansion of Jamie's one, which measure the asymmetry, to more generic purpose.
It will shake a suspended optic of interest and measure the response of each sensor by observing the demodulated I and Q signals from the LOCKIN module.
I will continue working on this.
- made a function that drives the LOCKIN oscillator and get the data from the I and Q outputs.
- checked the function with the MICH configuration.
ITMX, ITMY and BS were shaken at 100 Hz and at different time.
Then the response of AS55_Q showed agreement with what I got before for the actuator calibration (see this entry).
It means the function is working fine.
The Lightwave NPRO power supply which is being shared between the AS table and the ETMY table has been shifted back to the ETMY table.
The current to the laser is set at 1.5A. The laser output is 200mW at this current level.
There were small pieces of glass, remnants of a fluorescent tube, which were lying around on the ETMY end table for a while now. We picked up the larger pieces by hand and used the HEPA filtered vacuum cleaner to pick up the remaining glass and dust on the table.
40m surfs: Nicole Ing, Iswita Saikia and Sonali Mohapatra received 40m specific safety training today.
1.The aim is the laser frequency stabilisation of PSL and AUX.
2.As a first step we want to couple some of the AUX laser beam into a single mode optical fibre and route the fibre to the PSL table.
3.The position of the optical fibre on the ETMY table is shown by the coupler in the attached picture. The yellow lines show the new scheme we want to implement.
4.WHAT WE DID TODAY.
I used a matlab code written by Koji to analyse the transimpedance and current noise data of REFL55. The details are in the attached pdf file.
Resonance is at 55.28 MHz:
Q of 4.5, Transimpedance of 615 Ohms
shot noise intercept current = 1.59 mA
current noise =21 pA/rtHz
Notch at 110.78 MHz:
Q of 54.8 Transimpedance of 14.68 Ohms.
REFL55 was modified. The noise level confirmed. The PD is now ready to be installed.
Kevin's measurement report told us that something was wrong with REFL55 PD. The transimpedance looked OK, but the noise level was terrible (equivalent to the shotnoise of 14mA DC current).
Rana and I looked at the circuit, and cleaned up the circuit, by removing unnecessary 11MHz notch, 1k shunt resister, and so on.
I made a quick characterization of the PD.
The transimpedance ws measured as a function of the frequency. The resonance was tuned at 55MHz. The notch was tuned at 110MHz in order to reject the second harmonics. The transimpedance was ~540V/A at 55MHz. (For the calibration, I believed the DC transimpedance of 50V/A and 10000V/A for the DC paths of this PD and #1611, respectively, as well as the RF impedance (700V/A0 of #1611.
Output noise levels were measured with various amount of photocurrent using white light from a light bulb. The measurement was perforemed well above the noise level of the measurement instruments.
The measured output noise levels were converted into the equivalent current noise on the PD. The dark noise level agrees with the shot noise level of 1.5mA (i.e. 22pA/rtHz). In deed, the noise level went up x~1.5 when the photocurrent is ~1.4mA.
The small optical bench (next to the MC-2 Chamber and the tool box tower) has been cleared of the misc. object previously on it, cleaned, and leveled (after much calibration X___X).
PLEASE, PLEASE, PLEASE do NOT MOVE OR HIT THE TABLE! It was incredibly painful to level.
This is how leveling the table made me feel...
VERY SAD...so do not move please!
The shaker has already been moved to the table and the amplifier for my shaking experiment is located behind the table (not on the table, as to prevent scratching).
There was a rogue, undocumented, gateway process running on NODUS since ~4 PM. This guy was broadcasting channels back into the Martian and causing lockups in the IOO controls. I did a kill -9 on its process.
Someone will pay for this.
Put the serial numbers into the elog. So we can identify the laser and controller in the future.
Hmm. Was the current within the operating range? (i.e. Is it a 700mW laser or a 1W one?)
You can obtain the nominal operating current from the old EPICS values (or some elog entries).
Note that NPROs are designed to be healthy only at around the nominal pumping power
(i.e. thermal gradient, and thermal lensing of the crystal, etc.)
Be aware that this laser should be used under the old SOP. So the appropriate interlocking is mandatory.
And probably we need to modify the SOP such that it reflects the latest situation.
The I-P curve of the LightWave NPRO, which was taken out from the MOPA box, was measured. It looks healthy.
The output power can go up to about 1 W, but I guess we don't want it to run at a high power to avoid any further degradation since the laser is old.