We now have the DC signal from three PDs available in the ADC channels 14,15 and 16. The signals are from REFL55, AS55 and POY photodiodes respectively. As the DC signals on all the other PDs of the same port (REFL, AS and PO) have the same information we do not need to monitor more than one DC PD at each port.
The LSC PD Interface Card, D990543 - Rev B, can take 4 PDs and provides the DC signals of the PDs on the connector P2 (the lower of the two) on the back plane of the chassis. An adaptor card, D010005-00, plugs into the back plane from the rear of the Eurorack and provides the four DC signals on two-pin lemo sockets.
I have connected the three DC signals from the relevant RF PDs (above) to a DC whitening filter, D990694-B-1 which is associated with the channels 9 to 16 of the ADC card.
The cables are in a bit of a mess right now as some of the PD power supply lines are too short to reach up the the Interface card in the top Eurocart. Steve and I plan to redo some of the cabling later today
Minicircuits ERA-5SM was used for the RF amp of the BBPD. This amp is promising as a replacement of Teledyne Cougar AP389
as ERA-5SM gave us the best performance so far among the BBPDs I have ever tested for the aLIGO BBPD/Green.
The -3dB bandwidth of ~200MHz and the noise floor at the shotnoise level of 0.7mA DC current were obtained.
The aLIGO BBPD candidate (LIGO Document D1002969-v7) employs Teledyne Cougar AP389 as an RF amplifier.
This PD design utilizes the 50Ohm termination of the RF amp as a transimpedance resistance at RF freq.
However, it turned out that the bandwidth of the transimpedance gets rather low when we use AP389, as seen in the attachment2.
The amplifier itself is broadband upto 250MHz (the transfer function was confirmed with 50Ohm source).
The reason is not understood but AP389 seems dislike current source. Rich suggested use of S-parameter measurement
to construct better model of the curcuit.
On the other hand, the RF amplifiers from Minicircuits (coaxial type like ZFL-1000LN+), in general, exhibit better compatibility with PDs.
If you open the amplifier case, you find ERA or MAR type monolithic amplifiers are used.
So the question is if we can replace AP389 by any of ERA or MAR.
- The large gain of the RF amp is preffered as far as the output does not get saturated.
- The amplifier should be low noise so that we can detect shot noise (~1mA).
- The freq range of the useful signal is from 9MHz to 160MHz.
The advanced LIGO BBPD is supposed to be able to receive 50mW of IR or 15mW of 532nm. This approximately corresponds to
5mA of DC photocurrent if we assume FFD-100 for the photodiode. At the best (or worst) case, this 5mA has 100% intensity modulation.
If this current is converted to the votage through the 50Ohm input termination of the RF amp, we receive -2dBm of RF signal at maximum.
This gives us a dilemma. if the amp is low noise but the maximum output power is small, we can not put large amount of light
on the PD. If the amp has a high max output power (and a high gain), but the amp is not low noise, the PD has narrow power range
where we can observe the shotnoise above the electronics noise.
What we need is powerful, high gain, and low noise RF amplifier!
Teledyne Cougar AP389 was almost an ideal candidate before it shows unideal behavior with the PD.
Among Minicircuits ERA and MAR series, ERA-5 (or ERA-5SM) is the most compatible amplifier.
Considering the difference of the gain, they are quite similar for our purpose. Both can handle upto -2dBm,
which is just the right amount for the possible maximum power we get from the 5mA of photocurrent.
A test circuit has been built (p.1 attachment #1) on a single sided prototype board.
First, the transfer function was measured with FFD-100. With the bias 100V (max) the -3dB bandwidth of ~200MHz was observed.
This decreases down to 75MHz if the bias is 25V, which is the voltage supplied by the aLIGO BBPD circuit. The transimpedance
at the plateau was ~400Ohm.
Next, S3399 was tested with the circuit. With the bias 25V and 30V (max) the -3dB bandwidth of ~200MHz was obtained although
the responsivity of S3399 (i.e. A/W) at 1064nm is about factor of 2 smaller than that of FFD-100.
The noise levels were measured. There are many sprious peaks (possibly by unideal hand made board and insufficient power supply bypassing?).
Othewise, the floor level shows 0.7mA shotnoise level.
The PMC exhibited the reduction of the transmission, so it was aligned.
The misalignment was not the angle of the beam but the translation of the beam in the vertical direction
as I had no improvement by moving the pitch of one mirror and had to move those two differentially.
This will give us the information what is moving by the temperature fluctuation or whatever.
I think that the gain ramping time (_TRAMP) should be set to 1 second for all filter modules by default. We don't want them to switch instantaneously except in a few special cases.
So Jamie and I wrote a script (in scripts/general/) which sets all of these fields to 1 for a given system. The name of the system is an argument to the script. e.g.
> setTRAMP LSC 1
The idea is that we set it once and then from then on, its captured by the autoBURT. Of course, we have to run this script each time we add new filter modules to a model.
I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs. I'll do the MCs, the PRMs, and the SRMs next.
I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain). It looked like this:
Valera said that one of these was for the roll mode and the other for the bounce mode. However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz. So, we're taking a guess that this was for a mode that has moved due to new pendulum designs. For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line. Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental. When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.
ITMX is done. I'll continue tomorrow. I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).
(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops. It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)
Foton doesn't correctly display the LSC filter bank file : C1LSC.txt.
This was because of a bug in the RCG for foton filter module naming when top names is being used. Rebuilding the LSC front-end model with top_names (which was needed to get around another bug in the RCG) broke the filter file. I manually fixed the file, so it should work now.
New right angle PVC front panel with SMA bulkhead connectors are in place. The connections are still lose. It is ready for Suresh to finalise his vision on it.
They are the DC responses.
I put the resonant frequencies that Leo reported in the wiki to obtain the DC response.
The resonant frequencies I used are :
f_BS = 0.957 Hz
f_ITMX = 0.966 Hz
f_ITMY = 0.988 Hz
Also I assumed that all the Q-values are 5 due to the damping.
I've got confused
1) Are these the DC responses of the coils? If that is true, we need to specify the resonant frequency of each suspension to get the AC response.
2) Are these the AC responses well above the resonant freqs? In that case, The responses should be x.xxx / f^2 [m/counts]
BS = 3.69e-08 [m/counts]
ITMX = 8.89e-09 [m/counts]
ITMY = 9.22e-09 [m/counts]
I installed 'glue' on Rossa, Allegra, and Rosalba. This is a Python module that includes a facility for LIGO_LW XML files. Oddly, I couldn't find the glue package on Pianosa.
Valera and I installed the the temp sensor and the interface box that Rana fixed. This may help with diagnosing the PSL drift.
I was wrong. Rana did not fix the interface box. I removed the interface box and turned down the HEPA flow from 100 to 20% on the Variac.
Foton tells a lie that they all are empty.
The file itself looks fine to me i.e. I can find correct filters in text format.
Looks like someone (maybe Joe and Jenne ?) updated the file. I am not sure if this is the reason or not.
allegra:chans>ls -al | grep LSC
-rw-r--r-- 1 controls controls 20659 May 5 11:46 C1LSC.txt
NEEDS TO BE FIXED SOON
See my updated elog 4636 for what Joe and I did this morning, and what a possible problem is (making the LSC model into a sub-model).
The open loop transfer functions of the Michelson locking have been measured.
The purpose of this excise is to calibrate the coil-magnet actuators on BS and ITMs.
The estimated actuation coefficients are :
BS = 3.69e-08 [m/counts]
ITMX = 8.89e-09 [m/counts]
ITMY = 9.22e-09 [m/counts]
EDIT by KI on 15/5/2011:
The calibration of MICH error signal was wrong by a factor of 2.
BS = 3.69e-08 [m/counts]
ITMX = 8.89e-09 [m/counts]
ITMY = 9.22e-09 [m/counts]
I guess the accuracy is something like 5 % because the calibration of the MI optical gain relies on a peak-to-peak measurement.
A next step is to calibrate the PRM actuator and the PRC optical gain.
The Michelson was locked with different actuators in every measurement. I locked the Michelson to the dark fringe with BS, ITMX and ITMY in each time.
The measured peak-to-peak value in the error signal was 20.2 counts, corresponding to a sensor gain of 5.96e+07 [counts/m]. Note that I used AS55_Q for the locking.
After locking the MI I took the open loop transfer function by injecting broadband noise from DTT.
Then the data were fitted coarsely. In the fitting I used the resonant frequencies that Leo reported recently (http://blue.ligo-wa.caltech.edu:8000/40m/Mechanical_Resonances).
The Q-values are assumed to be 5 because of the local dampings. As a result the fitting gives us the actuator coefficients.
Here is a plot showing the measured open loop transfer functions. The solid lines represent the fittings.
(by the way)
- The delay time including ADC/DAC and RFM looks quite big. According to the fitting the delay is something like 600 usec.
This is about two times larger than the one reported before (see this entry). I will re-measure it with empty filters.
allegra:chans>ls -al | grep LSC
-rw-r--r-- 1 controls controls 20659 May 5 11:46 C1LSC.txt
Joe helped me compile the lsc simulink model, and now we have R&D phase rotation.
Right now, we have to do our own math, and figure out what relative phase to put in. Soonly, I'll figure out how to do subtraction, and we can put in the measured value.
More details when I'm not running around like crazy...
Okie dokie. Last night I had modified the c1lsc.mdl to accommodate the R & D phase rotation. I also made pretty new screens. This morning however, the adventures began.....
Under Joe's supervision, I ran "make c1lsc". The error that came up was something about things not being connected. Joe assures me that this is a temporary problem, that Rolf is already working on. The reason is that right now the LSC model is "flat", i.e. it doesn't have a bunch of sub-boxes and sub-screens in the simulink model. Somehow this causes badness. Joe stuck all the guts of the LSC model into a sub-model. He then enabled "top_names", which makes the channels use the name of the sub-model, not the sub-model AND the main model (so since the sub-model is called LSC, our channels are just C1:LSC-OTHER_STUFF, rather than C1:LSC-LSC_OTHER_STUFF). This fixed things so that the compiling worked (when we did "make c1lsc"). The one other thing that we changed was to delete all of the little "Outs" that were attached to EPICS readouts. These are unneccessary and don't go anywhere, and when we made the sub-model, they made a bunch of empty outputs (unconnected outs on the main simulink model). So, after doing that, we were able to compile, and do "make install-c1lsc", and all was good in the world. Mostly.
Joe then noticed that I was using the CDS part "cdsPhase", which only takes one phase input. I wanted "cdswfsPhase", which actually does the R&D phase rotation that we want. Perhaps Alex/Rolf/whoever should change the name of that CDS part. We switched all of the cdsPhase blocks to be cdswfsPhase, and recompiled. All was still good in the world. Mostly.
The last thing that was funny was that when I wanted to execute the medm screens, they would still look at the old _IQ_MTRX_1_1 and _IQ_MTRX_2_1 values, rather than the newly defined _PHASE_R and _PHASE_D channels, even though while editing the medm screen, it looked like it was pointing to the right place. Anyhow, I opened the text file version of the C1LSC_PDX.adl, and changed the channel names to the _R and _D versions by hand. I don't know if we edit the screens and run generate_screens.py again, if we'll have to re-edit the .adl text files.
After fixing this, all really was good in the world.
Perhaps though, this making a subsystem business broke the filters somehow? Foton is looking at the wrong text file now? Something? The filters are all still there, they just got moved down a level. Joe said that he and Rolf are on it, and he should be able to put the LSC model back to being "flat" in the next few days.
eeek. I've been running around all day, so this is an incomplete elog. I'll fill in more stuff in the next hour or so, but just to let people know what's going on:
Valera noticed that lots of things in and around the PSL table are drifting with temperature. This is why he and Steve installed a temp sensor on the table earlier today.
Since the alignment into the PMC, and also the alignment downstream of the PMC have been drifting in angle, we supposed that it might be the PMC itself which is changing somehow with temperature. We don't have a good idea of how exactly it is sensitive to temperature, but we're working on figuring it out.
Round 1 of testing: We put a foil hat over the PMC to shield it from the HEPA air blowing directly down on top of it. I made sure that the foil is also covering the PZT and the metal ring at the end of the PMC, because this could potentially be the problem (metal is usually more temperature sensitive than glass, or the PZT itself could be changing, either of which could make the end mirror twist, and change the alignment of the PMC). We'll see later if this did anything useful or not.
I have photos of the aluminum foil setup, which I will post later when I get back to the lab after teaching.
Having finished the bulk of the work for the LPF itself ( see here ), I have begun trying to design the seismometer box to Jenne's specifications.
Currently looking into what the voltage buffer amplifier might look like for this.
Suggestions/corrections would be much appreciated!
Comparison between Hamamatsu S3399 and Perkin Elmer FFD-100
These are the candidates for the BB PD for the green beat detection as well as aLIGO BB PD for 532nm/1064nm.
FFD-100 seems the good candidate.
Basic difference between S3399 and FFD-100
- S3399 Si PIN diode: 3mm dia., max bias = 30V, Cd=20pF
- FFD-100 Si PIN diode: 2.5mm dia., max bias = 100V, Cd=7pF
The circuit at the page 1 was used for the amplifier.
- FFD-100 showed 5dB (= x1.8) larger responsivity for 1064nm compared with S3399. (Plot not shown. Confirmed on the analyzer.)
- -3dB BW: S3399 180MHz, FFD-100 250MHz for 100V_bias. For 30V bias, they are similar.
I modified C1LSC.mdl to use the CDSphase blocks, which automatically calculate the R and D phase rotation for us. Now each of the RFPDs has 2 channels in place of the old IQ_MTRX channels: C1:LSC-RFPD_PHASE_R and C1:LSC-RFPD_PHASE_D.
I have not yet compiled / rebooted / done CDS magic to actually make these installed. So far the change is only in the simulink model.
I was going to wait until morning to compile/reboot/magic, so I can do it under Joe's supervision.
In the meantime, I also modified the RFPD screens. They have white boxes for the _R and _D channels just now, but that's because the new model hasn't been put in. They now look like phase rotators, instead of Koji's temporary matrix.
Still to do: Find the EPICS database where the phase rotation calculation is done (you give it an angle, it gives you sin(angle) and cos(angle) ). I want to put a "90-angle" in the database so that we can type in the measured relative phase between I and Q, and it will calculate how many more degrees it needs to get to 90deg.
Building on what was posted previously
The configuration has now evolved into an Inverting Op Amp Feedback Low Pass Filter circuit.
Had to change out some components to satisfy conditions: R1=1k Ohm, R2=10k Ohm, C=0.1uF. These were changed in order to decrease the magnitude of the current passing through the op amp by a factor of 10 (10V supplied through the R1 resistor yields about 10mA). The configuration itself was changed from non-inverting to inverting in order to get the frequency vs. gain part of the Bode plot to continue to decrease across higher frequencies instead of leveling off around 4kHz.
The attached plot shows 2 day trends of the PMC and MC reflected and transmitted power, the PSL POS/ANG QPD signals, and the temperature measured by the dust counter.
The power step in the middle of the plot corresponds to Koji/Jenne PMC realignment yesterday.
It looks like everything is following the day/night temperature changes.
I went push all the possible connectors for the MC3 shadow sensors including the SCSIs, flat cables and satellite box.
Also I put screws on them so that they won't become loose any more.
As a result UL_PDMON dropped from 0.6 V to 0.490 V and it becomes stable so far.
I didn't strain relief the cables but we must do it at some point before going into the full locking test.
The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.
The rest of the MC1,2,3 PD signals looked ok.
[Leo w/ a little help from Kiwamu]
Leo summarized the mechanical resonances of all the suspensions, based on the free-swinging spectra taken on Sat Apr 30.
Since Leo doesn't have the wiki account I helped him putting the information on the wiki.
Good work, Leo !
Here are the free-swinging spectra for the BS, ETMX, ETMY, ITMX, ITMY, MC1, MC2, MC3, and PRM chambers. Kiwamu left the suspensions free for 5 hours this weekend, starting at Sat Apr 30 00:15:26 2011.
Last night I was trying to calibrate the MICH error signal and the actuators on BS and ITMs.
However I gave up taking the data because the MC locking was unstable. MC3 drifted a lot.
REFL55 has been installed on the AP table. REFL11 has been moved to make space for a 50% beam splitter. The reflected beam from this splitter is about 30% of the transmitted beam power. The reflected beam goes to REFL11 in the current configuration. The DC levels are 1.2V on REFL 11 and 3.5V on the REFL55.
I redid some of the cabling on the table because the we need to choose the heliax cables such that they end up close to the demod board location. As per the 1Y2 (LSC) rack layout given here, some of the PD signals have to arrive at the top and others at the bottom of the LSC rack.
Currently the PDs are connected as follows:
REFL11 PD --> Heliax (ASDD133) (arriving at the top of LSC rack) --> REFL11 Demod Board
REFL55 PD --> Heliax (REFL166) (arriving at the top of LSC rack) --> AS55 Demod Board
AS55 PD --> Heliax (AS166) (arriving at the top of the LSC rack) --> not connected.
We are waiting for the Minicircuits parts to modify the rest of the demod boards.
The heliax cables arriving at the LSC rack are not yet fixed properly. I hope to get this done with Steve's help today.
The first time I noticed that the MC was not locking was after I had finished switching the RF source installation. Before this change the RF modulation frequency (for MC) was 29.485 MHz as read from the Marconi RF Source. We replaced this with a Wenzel crystal source at 29.491 MHz. This may have changed the loop gain.
Today, I changed the MC alignment to optimise the MC lock. Valera pointed out that this is not a desirable solution since it would shift the beam pointing for all components downstream. However, since we are not sure what was the last stable configuration, we decided to stay with the current settings for now and see the trends of several parameters which would tell us if something is drifting and causing the autolocker to fail.
The MC Auto locker is now working okay. However to obtain lock initially we reduced the loop gain by decreasing the VCO gain. We then increased the gain after the autolocker had locked the MC.
I found that the MC autolocker was OFF. Kiwamu says he turned it off because its slow. Suresh says that he has some feelings that maybe something is wrong. I'll let them describe what they know about the MC in an elog.
I checked the trend of the MC and PMC transmissions for the past 30 days:
Looks like the alignment has been drifitng. PMC was corrected recently by Koji, but the alignment of the input beam to the MC or the MC itself has to be fixed. Has someone been twiddling the MC SUS alignment biases??
Since we've got the PRMI locked we now should be able to do more qualitative measurements.
Here is a task list that we will measure/develop in the PRMI condition.
- Optical gain measurements
- Characterization of control loops
- MICH and PRC calibrations
- Noise budget
- Development of automatic noise budget scripts
- Arm loss measurement
- Shnupp asymmetry measurement
My observation wasn't accurate enough.
The looseness came from the fact that the N-SMA bulk heads were slipping on the black plate.
This is actually what Suresh pointed out (see here). So the thickness of the black plate doesn't matter in this case.
Somehow I was able to tighten the bulk heads using two wrenches and I think they are now tight enough so that the heliax's heads don't move any more.
I found that all the Heliax cables landing on the bottom of 1Y2 were too loose.
The looseness basically comes from the fact the black plate is too thick for the Heliax cable to go all the way. It permits the Heliax's heads to rotate freely.
Here are some details about the PRMI locking done last night.
REFL11 has been installed on the AP table. The RF signal from the RFPD is sent by a heliax cable which has been called ASDD133.
Before the beam goes into the RFPD a HWP and PBS are installed such that we can adjust the amount of light entering to the photo diode.
One thing I didn't like was that I had to introduce a big amount of the light into the PD to get a reasonably big RF signal.
I was trying to look for an RF signal by looking at a spectrum analyzer, then I realized that the RF signal at 11 MHz was quite tiny when the DC_MON was less than 1.5 V.
After I increased the amount of the light up to 1.9 V in DC_MON, which sounds already too much, I then got able to see the 11 MHz signal on the analyzer.
Note that I decreased the amount of the light down to 0.5 V after I finished locking the PRMI.
We should make sure what is going on with the 11 MHz modulation.
First I started locking the MIchelson with AS55. The demodulation phase was already somewhat optimized to the I-signal port.
So I decided not to touch the demodulation phase matrix because it may take some times.
After I eliminated electrical offsets in the digital side, I was easily able to lock the Michelson. The control sign was plus.
Then I started playing with the PRC control too. The demodulation phase in REFL11 looked nearly 45 deg although I didn't carefully measure it.
I made a 45 deg rotational matrix to maximize the I-port signal and tried to lock the PRC. Then immediately I was able to lock PRC as well as MICH.
GAIN_MICH = 100
GAIN_PRC = 100
Also GAIN_PRC = -100 gave a carrier resonant lock.
The control filters are the same in MICH and PRC. I used my favorite filters as usual.
FM1 = 1000 : 10
FM6 = 0.1 : 1
FM7 = 1 : 50
Somehow I frequently failed to engage the boost filters (i.e. FM6 and FM7) it looks offsets in the control path kicks either BS or PRM.
The PRMI has been successfully locked
Details will be posted in the morning.
The returning spot diameter on the qpd ~10 mm. In order to reduce the spot size I moved the f 1145 mm lens toward the PRM ~ 25 cm. The spot size was reduced to ~8 mm, 3200 counts.
I'll try to find an other lens tomorrow.
Atm 1, PRM oplev inward path with 2 lens solution: 14 cm gap between F 1145 and F 1545 mm lenses.
Atm 2, The PRM beam size 3 mm and the beam quality is still bad. The BS path only needed alignment.
The little red all terrain cargo wagon 40" x 18" has just arrived on pneumatic wheels.
Model #29, 200 lbs max load at 26 PSI, minimum age requirement 1.5 years
This is a continuation of this
The low pass filter is finally acceptable, and its Bode graph is below (on a ~3Hz frequency span that shows the cutoff frequency is at 0.1Hz)
Jenne went through all the suspension racks and pushed all the connectors.
After pushing them, we had a quick look at those spectra and found no funny noise spectrum except for C1:PRM-SENSOR_UL.
We then checked connection around the SCSI cables and eventually found the connection between ADC_card_0 and a SCSI was loose.
We put short standoffs on the ADC card so that the screws from the SCSI can nicely reach to the ADC card. Now everything looks fine.
SUS diagnostic is quite useful !
Notice that the C1:SUS-ITMX_SENSOR_UL and C1:SUS-MC3_SENSOR_UL spectra fall as 1/f. Jenne suggested that this might indicate that there is a loose electrical connection.
I was charge with making a Non-Inverting Op Amp Low Pass Feedback circuit for Jenne, which may somehow be integrated into a seismometer project she's working on.
Circuit diagram is attached. Calculations show that R1, R2 and C have the following relationship: if R1=10^n, R2=10^(n+1), C=10^(-n-4). For the particular circuit being modeled by the transfer function, R1=100 Ohm, R2=1k Ohm, and C=1uF.
Attached also is the circuit's Bode plot, showing frequency versus gain and phase, respectively. The frequency versus gain graph is true to what the circuit was calculated to generate: a gain of +20 and a cutoff frequency at 200Hz. Not sure what's going on with the frequency verus phase plot.
This is GPS time 988 182 941. Quick tip: you can do local to GPS time conversions using lalapps_tconvert, which is a lot like tconvert but with special powers. It is installed on pianosa.
$ lalapps_tconvert Sat Apr 30 00:15:26 2011
I generated these figures with the attached Python script, measure.py.
Also, notice that C1:SUS-ETMY_SENSOR_LR, C1:SUS-ITMY_SENSOR_LL, and C1:SUS-PRM_SENSOR_SIDE are a lot noisier above 10 Hz.
Done. C1:PSL-PMC_PMCTRANSPD was improved from ~0.75 to 0.87.
- PMC alignment (Jenne/Koji)
I temporarily turned off the power to the 1Y2 rack this morning while wiring in the binary output adapter board power (+/- 15V) into the cross connects.
The board is now powered and we can proceed to testing if can actually control the LSC whitening filters.
1) Filled in the C1SUS_BS_OLMATRIX properly so as to make the BS oplev work for Steve.
2) Turned on the ITMX damping. Apparently it had tripped this morning, possibly due to work in the lab area.
3) The ETMX FE controller (c1scx) had ADC timed out and died sometime around 8:30 am. The c1x01 (the IOP on the ETMX computer) was also indicating a FB status error (mismatch in DAQ channels).
The reported error in dmesg on c1iscex was:
[1628690.250002] c1spx: ADC TIMEOUT 0 3541 21 3605
[1628690.250002] c1scx: ADC TIMEOUT 0 3541 21 3605
Just to be safe, I rebuilt the c1x01 and c1scx models, ran ./activateDAQ.py, and used the scripts killc1spx, killc1scx, and killc1x01.
I finally restarted the process with startc1x01, startc1scx, and startc1spx. Everything is currently alive and indicating all green.
I think the installation of the PD DC signals are quite important. What to do
1) Connect the DC signals to the right top whitening board (be aware that there may be the modification of the whitening circuit).
2) Reconfigure the LSC model such that the DC signal is passed to the right channels (modify the left top part of the model)
Daytime tasks :
- PRM & BS oplev (Steve)
- LSC binary outputs (Joe/Jamie)
- installation of the REFL55 RFPD (Suresh/Jamie)
- Adjustment of demodulation phases (Kiwamu)
- Bounce-Roll filters on BS and PRM (Suresh/Joe)
- Suspension diagnostic using the free-swinging spectra (Leo)
- PMC alignment (Jenne/Koji)
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.
Also changing the sign of the PRC control gave me the lock of the carrier resonant condition.
The screenshot above is the time series of the error signals when I was locking the PRMI in the sideband resonant condition (i.e. carrier is non-resonant).
Note that I used REFL11 for the PRC control and AS55 for the MICH control as planed.
Details will be posted in the morning.
Today we will try to lock the PRMI.
The Martian wireless bridge has the ethernet cable inserted in the wrong connector.
It should be inserted to one of the four port. Not in the "INTERNET" connector.
Once the connector has been changed, the martian net as well as the internet became accessible from the laptops.
The countersink gives rise to another problem when we mount the N-type-to-SMA bulkhead adaptor. As we are making a circular hole in the plastic strip (instead of a hole with two flat sections) the adaptor is free to turn when we tighten it with a wrench. We currently hold the smooth circular part on the other side with a gripping pliers and while tightening. If that part disappears into the countersink (as seen in the pics) we will not be able to tighten the adaptor sufficiently and consequently we will also not be able to get the heliax connector to be tight.
A better solution would be to use the 1/4-inch plastic L-angle beam which Steve has used on the AS table. In addition to solving this loose connector problem, the beam is also more rigid than the plastic strip.
Due to this loose connection the RF power at 55 MHz varies from -34 dBm to 3 dBm, depending on the angle of the Heliax's head.
What we should do is to make countersinks on the black plate like this:
- AS55 RFPD
With a help from Jamie the AS55 RFPD was installed.
- 55 MHz demodulation board
The AS55 demod board was installed on 1Y2.
- 3-way combiner
ZFSC-3-13 has been installed. All the RF cables from the source side were connected to the combiner.
- installation of the REFL11 RFPD
- DAQ check for AS55 and REFL11
(to be done in the daytime)
- setup AS55 RFPD
- install a demod board for 55 MHz
- install a 3-way RF combiner on EOM.
- prepare 55 MHz RF source (Marconi or RF source box ?)