As per Gautam's request, I list the changes that were made since he left:
1. The AOM driver was connected to a signal generator.
2. The first order beam from the AOM was coupled into the PMC while the zero-order beam is blocked. We might want to keep this configuration if the pointing stability is adequate.
3. c1psl got Burt restored to Dec 1st.
4. Megatron got updated.
Currently, c1susaux seems unresponsive and needs to be rebooted.
In order to use the 0th-order deflection beam from the AOM for cavity mode scans, I've coaligned this beam to the existing mode-matching/launch optics set up for the 1st-order beam.
Instead of being dumped, the 0th-order beam is now steered by two 45-degree mirrors into the existing beam path. The second mirror is on a flip mount so that we can quickly switch between 0th-order/1st-order injections. None of the existing optics were touched, so the 1st-order beam alignment should still be undisturbed.
Currently the 0th-order beam is being injected into the IFO. After attenuating so as to not exceed 100 mW incident on the fiber, approximately 50 mW of power reaches the AS table. That coupling efficiency is similar to what we have with the 1st-order beam. With the Y-arm cavity locked and the AUX PLL locked at RF offset = 47.60 MHz (an Y-arm FSR), I observed a -50 dBm beat note at Y-end transmission.
I've made several changes to the C1MCS model and C1PEM model, and have installed BLRMS filters for the MC mirror coils, which are now running. The main idea behind this test was to see how much CPU time was added as a result of setting up IPC channels to take the signals from C1MCS to C1PEM (where the BLRMS filtering happens) - I checked the average CPU time before and after installing the BLRMS filters, and saw that the increase was about 1 usec for 15 IPC channels installed (it increased from ~27usec to 28usec). A direct scaling would suggest that setting up the BLRMS for the vertex optics might push the c1sus model close to timing out - it is at ~50usec right now, and I would need, per optic, 12 IPC channels, and so for the 5 vertex optics, this would suggest that the CPU timing would be ~55usec. I have not committed either of the changed models to the SVN just yet.
Now that I have a procedure in place to install the BLRMS filters, we can do so for other channels as well, such as for the coils and Oplevs of the vertex optics, and the remaining PEM channels (SEIS, accelerometers, microphones?). For the vertex optics though, I am not sure if we need to do some rearrangement to the c1sus model to make sure it does not time out...
As we had planned yesterday (ELOG 10034) I and Eric Gustafson wanted to manually measure the transimpedence for REFL33. But on closer inspection I found the RF signal cable coming from the Photodiode REF DET (mounted on the POY table), that we were supposed to plug into the network analyzer, did not have an SMA connector at the end. There was just the Teflon and metal part sticking out of the insulation. So we disconnected the cable labeled REF DET from the PD and pulled it out to fix it. (POY table and from near the 1Y1 rack)
Being unable to locate any SMA male connectors in the 40m lab [pasternack PE4025], we headed over to Downs where Rich Abbott did a quick and awesome job of soldering the SMA connector and also teaching me in the process. I will write an ELOG on how to do a clean solder of the SMA connectors to the RF cable shortly for future reference.
Coming back to the 40m we rerouted the REF DET cable from near the 1Y1 rack and into the POY table. This job was done mostly by Eric. We were also unable to locate a torque wrench to tighten the cable at the PD’s end and had to leave it finger tight. Eric is planning to buy a new torque wrench as we will need it often.
Also, I cross checked the SwithList located at /users/alex.cole/switchList with the RF switch connections at 1Y1 rack and turns out it is consistent, except that at CH2 of the first switch where MC REFL was to be connected, there is a unlabeled cable. It might belong to the correct PD, but must be made sure of. The rest of the channels that are not mentioned in the list were unconnected on the RF switch.
Now instead of disconnecting REFL 33 to make measurements with the NA, we had to take out AS55 from the RF switch, as the former was very hard to remove without the torque wrench. Then Eric removed the optical fiber which was illuminating the AS55 (AS table) from its mount to hook it up to the power meter. But then we were not sure of how to operate the Laser diode controller (LDC 3744C) and decided to leave stuff as it is and continue either tomorrow or on Monday. Right now we closed the optical fiber of AS55 with a cap and it remains unmounted. The RF cables of REF DET and AS55 were left hanging near the 1Y1 rack.
[Nichin, Eric G, Koji]
Continuing out work from elog:10037, we wanted to check if the frequency response of AS55. Having figured out exactly how to use the Laser diode controller (LDC 3744C), we hooked up a fiber power meter to the optical fiber illuminating AS55 (that we disconnected from its mount last Friday ) and raised up the current to 150mA to get almost 0.8mW power reading.
When aligning the fiber to illuminate the PD, we found that the beam was pretty wide. So we pulled out the collimator and tweaked it to get a focused beam. The fiber was mounted back and was aligned to get a maximum DC reading. The multimeter readout 30mV finally. Taking the transimpedence as 200ohm approx., the hot current is about 1.5mA.
Network analyzer was now connected to the modulation input of the laser and the RF output from REF DET and AS55 (inputs to RF switch at rack 1Y1) were connected as input to measure the transfer function. We got just noise on the scope of NA. So, then we tried REFL33 as the Input and still got nothing (We were also not sure if this PD was properly illuminated, we did not check). However the REF DET was giving a nice response on the scope. Turns out all the PDs were disconnected form the Demodulator (D990511) on rack 1Y2.
On closer inspection the RF cable between domodulator and RF switch that was labelled AS55 had a loose SMA connector at the switch end. I will have to fix that tomorrow . For the time being Koji connected the cable labelled REFL33 to the AS55 demodulator and we finally got a response form the AS55 PD on the NA. However no readings were recorded. The power supply to REF DET was turned off in the end as Eric G claimed that it has been ON for almost a year now, which is not a good thing. Also, we removed the modulation input from NA to the diode laser and terminated the input with a 50ohm terminator.
We planned to pull out and check each and every RF cable (especially the SMA ends for faulty soldering and loose connections) and fix/ replace them as needed.
Not "hot" current but "photo" current. Is this my bad!?
It was me who told Nichin that the DC transimpedance was 200Ohm. But according to this entry I checked the RF transimpedance of AS55 before.
In my code, the DC transimpedance was defined to be 50Ohm. If we believe it, 30mV corresponds to 0.6mA.
The multimeter readout 30mV finally. Taking the transimpedence as 200ohm approx., the hot current is about 1.5mA.
All the temporary changes to the video cables and the video MUX ( 3843 ) have been reversed and the system returned to its original state.
We put offsets in the PRCL and MICH loops, and measured sensing matrices for each condition.
What we found was that PRCL offsets of order 1/20th a linewidth (calibration to be checked tomorrow) would give significant changes in the angles of the REFL signal sensing matrix elements. We broke MICH lock before we were able to put in a significant enough offset to see the demod phases change.
Because there are so many plots, I've put them together in a pdf. Each page has a set of radar plots for sensing matrix elements. On the bottom of each page I note what our MICH and PRCL offset values were, and where the data is saved (in the 40m scripts directory). To see the differences, make sure your pdf viewer is set to single-page, not scrolling.
One major thing that we noted was that putting in a PRCL offset also changed the MICH offset. When we increased the PRCL offset, we saw the AS port get brighter (but not as bright as when we were putting in large MICH offsets).
Tomorrow, I need to check the calibrations we were using, to see how many meters we were moving the optics. Also, Q, Gabriele and I need to meditate and do some modelling to figure out why the length offset could be affecting the degeneracy so strongly.
After speaking with Jenne and Gabriele, I did a little bit of simulating based on my earlier code that looked at the angle of MICH vs. PRCL, just with cavity detuning instead of macroscopic length change.
The zero point in the following plots is with the PRC locked on the sideband. The PRC detuning was done by changing the PRM-BS microscopic length (in terms of phase), and the MICH detuning was done by adding half of the detuning to the BS-ITMY distance, and subtracting half of it from the BS-ITMX distance.
This plot is in terms of radians, so to roughly relate it to line width, here's a plot of the POP powers as a function of the PRC detuning.
And glossing over the MICH offset, here's the PRC offset plots in displacement, rather than radians.
The simulation is actually slightly different now. I now use nominal ITM T values (T=.014) instead of the random R=.99 I had in place.
(correction: Field Power should be Field Amplitude in the first plot)
I have measured the sensing matrix at a variety of PRCL offset values.
During this each measurement, I also took a 20 second average of the POP 2f signals and the ASDC signal:
All of this data was taken during a single lock stretch.
If / when I do this again, I want to go out to larger offsets. I won't take as many points, but I do want to see how far I can go before I lose lock, and what the phase separation looks like at larger offset values (this time, I stopped at +700 counts which is about 0.7nm, to start checking the negative values. MC has been unhappy, so I wasn't able to take very many negative offset values.)
I conclude that these sensing matrix measurements do see changes in the phase separation with PRCL length offset (what we saw / said yesterday), but that they do not line up with Q's simulation from this afternoon in elog 9671.
The simulation says that we shouldn't be seeing large phase changes until we get out to several nanometers, however the measurement is showing that we get large phase chnages with picometer scale offsets. Yesterday, Rana and I said that the offsets due to RAM were small (of order picometer), and that they were therefore likely not important (elog 9668). However, now it seems that the RAM is causing significant length offsets which then cause poor MICH/PRCL phase separation.
To Do List:
* Confirm MIST simulation with Optickle.
* Look at sensing matrix data pre-lockins (in the raw sensors).
* Check that there is no clipping anywhere in the REFL path (at least out of vacuum), and that the beam is sufficiently small on all 4 REFL diodes.
* Calculate the new PRC g-factor with the new length.
Alex is installing the newly compiled gds code (compiled on Centos 5.5 on Rosalba) which does in fact include the ezca type tools.
At the moment we don't have a solaris compile, although that should be done at somepoint in the future. It means the gds tools (diaggui, foton, etc) won't work on op440m. On the bright side, this newer gds code has a foton that doesn't seem to crash all the time on Linux.
We were stymied tonight by a problem which began late this afternoon. The MC would periodically go angularly unstable, breaking lock and tripping the MC2 watchdogs. Suspicion fell naturally upon McWFS.
Eventually I traced the problem to the MC3 SIDE damping, which appeared to not work--it wouldn't actually damp, and the Vmon values did not correspond to the SDSEN outputs. Suspicion fell on the coil driver.
Looking at the LEMO monitors on the MC3 coil driver, with the damping engaged, showed clear bit resolution at the 100mV level, indicating a digital/DAC problem. Rebooting c1sosvme, which acquires all the OSEM sensor signals and actually does the side damping, resolved the issue.
Lies! The problem was not resolved. The plot shows a 2-day trend, with the onset of the problem yesterday clearly visible as well as the ineffectiveness of the soft-reboot done yesterday. So we'll try a hard-reboot.
Since we decided to use the Acromag for readback of the temperature sensor for Kira's seismometer temperature control, I enabled logging of the channel Johannes had reserved for this purpose last week. Kira has made the physical connection of a temperature sensor to the BNC input for this channel - it reads back -2.92 V right now, which is around what I remember it being when Kira was doing her benchtop tests. I edited C0EDCU.ini to enable logging of this channel at 16 Hz. Presumably, a study of the ADC noise of the Acromag at low frequencies has to be made to ensure appropriate whitening (if any) can be added. Channel name is C1:PEM-SEIS_EX_TEMP_MON. Similarly, there is C1:PEM_SEIS_EX_TEMP_CTRL which is meant to be the control channel for the servoing. Calibration of the temperature sensor readback into temperature units remains. It also remains to be verified if we can have these slow EPICS channels integrated with a fast control model, or if the PID temperature control will be purely custom-script based as we have for the FSS slow loop.
I removed the fast channels I had setup temporarily in c1als. Recompilation and restart of the model went smoothly.
Since we've been hijacking channels like there is no tomorrow for the AUX-PLL setup, I'm documenting the channel names here. The next time c1psl requires a reboot, I'll rename these channels to something more sensible. To find the channel mapping, Koji suggested I use this. Has worked well for us so far... We've labelled all pairs of wires pulled out of the cross connects and insulation taped the stripped ends, in case we ever need to go back to the original config.
To mitigate integrator railing
I renamed most of the filter banks in the c1lsc model. The input filters are now labeled based on the RF photodiode's name, plus I or Q. The last set of filters in the OM subsystem (output matrix) have had the TO removed, and are now sensibly named ETMX, ETMY, etc.
We also removed the redundant filter banks between the LSCMTRX and the LSC_OM_MTRX. There is now only one set, the DARM, CARM, etc ones.
The webview of the LSC model can be found here.
The list of the iscaux channels and pin assignments were posted to google drive.
The spreadsheet can be viewable by the link sent to the 40m ML. It was shared with foteee@gmail for full access.
Necessary electronics modification
1. D990694 whitening filter modification (4 modules)
This module shares the fast and slow channels on the top DIN96pin (P1) connector. Also, the whitening selector (done by an analog signal per channel) is assigned over 17pin of the P1 connector, resulting in the necessity of the second DSUB cable. By migrating the fast channels, we can swap the cable from the P1 to P2. Also, the whitening selectors are concentrated on the first Dsub. (See Attachment1 P1)
2. D040180 / D1500308 Common Mode Board
CM servo board itself doesn't need any modification. The CM board uses P1 and P2. So we need to manufacture a special connector for CM Board P2. (cf The adapter board for P1 T1800260). See also D1700058.
3. D990543A1 LSC Photodiode Interface
PD I/F board has the DC mon channels spread over the 16pin limit. P1 21A can be connected to 6A so that we can accommdate it in the first Dsub.
Also the board uses AD797s. This is not necessary. We can replace them to OP27s. I actually don't know what is happening to those bias control, temp mon, enable, and status. These features should be disables at the I/F and the PDs. (See Attachment2 P1)
We setup the channels for PID control of the seismometer can. First, we ssh into c1auxex and went to /cvs/cds/caltech/target/c1auxex2 and found ETMXaux.db. We then added in new soft channels that we named C1:PEM-SEIS_EX_TEMP_SLOWKP, C1:PEM-SEIS_EX_TEMP_SLOWKI, C1:PEM-SEIS_EX_TEMP_SLOWKD that will control the proportional, integral and differential gain respectively. These channels are used in the script FSSSlow.py for PID control. We then had to restart the system, but first we turned off the LSC mode and then shut down the watchdog on the X end. After doing the restart, we disabled the OPLEV as well before restarting the watchdog. Then, we enabled the LSC mode again. This is done to not damage any of the optics during the restart. The restart is done by using sudo systemctl restart modbusIOC.service and restarted with sudo systemctl status modbusIOC.service. Then, we made sure that the channels existed and could be read and writtten to, so we tried z read [channel name] and it read 0.0. We then did z write [channel name] 5, and it wrote 5 to that channel. Now that the channels work, we can implement the PID script and check to make sure that it works as well.
I just finished carrying out the same checks for the DAC at 1X9 (with channels 9 through 16 that are unused as of now) as those I had done for the DAC at 1Y4, as the hardware prep up till now was done with the characterisation of the DAC at 1Y4. Conclusions:
I will now proceed to install various pieces of hardware (AI Board, PZT driver board, HV Power Supply and cabling) at 1X9, while not making the connection to the PZTs till I receive the go ahead.
We diagnosed the suspension damping of the IMC/BHD/recycling optics by kicking the various degree of freedom (dof) and then tuning the gain so that we get a residual Q of approx. 5 in the cases where this can be achieved.
MC2: SIDE-YAW coupling, but OK
MC3: Too much coupling between dofs, NEEDS ATTENTION
AS1: POS-PIT coupling, close to oscillation, cnt2um off, NEEDS ATTENTION
AS4: PIT-YAW coupling, cannot increase YAW gain because of coupling, No cnt2um, No Cheby, NEEDS ATTENTION
PR2: No cnt2um, No Cheby
PR3: POS-PIT coupling, cannot increase POS/PIT/YAW gain because of coupling, No cnt2um, No Cheby, NEEDS ATTENTION
SR2: No cnt2um
I and koji setup the measurement of the QPD response to the pitch and yaw displacements of the beam spot.
We did this using a 100mW 1064nm laser. Its power was attenuated to ~ 1.9mW, and the spot size at the QPD position was 6000-7000 um .
The QPD was put on a translation stage, using which, the center of teh QPD wrt the beam spot could be moved in pitch and yaw.
Following are the measurements :
The slope of teh linear region is -8356 /inch
The slope of the linear region in this is 9085/inch
The old plots looked horrible, and so here is a new plot
The slopes and other stats are
Linear model Poly1:
f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
p1 = 8550 (7684, 9417)
p2 = -2148 (-2390, -1906)
Goodness of fit:
Adjusted R-square: 0.9907
Linear model Poly1:
f(x) = p1*x + p2
Coefficients (with 95% confidence bounds):
p1 = -8310 (-8958, -7662)
p2 = 2084 (1916, 2252)
Goodness of fit:
Adjusted R-square: 0.9945
Setup loop to measure transfer function of control loop - the aim is to find the open loop gain of the system using the SR785 to inject noise (a swept sine) into the system and taking observations using the scope. We tried to calculate the gain algaebraically, in order to understand what our readings meant and what we can determine from them. Need to figure out how to run python script for the SR785, but took readings from cmd today.
Included - changes/additions made to circuit; frequency reponse obtained (need to check the frequency response as it does not look like the expected result, need to correct the loop itself, or increase the magnitude of the inserted noise as its possible that the noise is currently being suppressed by the system).
To do - circuit needs to be checked + laser lock improved - laser keeps leaving resonance while trying to take readings.
Kevin and I meaured the transfer function of the photodiode circuit using the Jenne laser and agilent in the 40m lab. The attached figures depict our measured transfer function over the modulation frequency ranges of 30kHz-30MHz and 1kHz-30MHz when the power of the laser was set to 69 and 95 μW. These plots indicate a clear roll off frequency around 300 kHz. In addition, the plots beginning at 1kHz display unstable behavior at frequencies below 30kHz. I am not sure why there is such a sharp change in the transfer function around 30kHz, but I suspect this to be due to an issue with the agilent or photodiode.
You have this measurement problem when the IF bandwidth is larger than the measurement frequency. I suspect the IF bandwidth is 30kHz.
To characterize the Mini-Circuits RF FC (Model UFC-6000) and plot Bode Plots at varying Modulation frequencies.
Here are the list of measurements(files attached) taken from FC using SRS(Model DS345) Synthesized Function Generator for a Sinusoidal signal at different Modulation Frequencies ranging from 0.01 Hz to 1 KHz:
Carrier Frequency Modulation Depth Attached measurement Folder
5 MHz Δ f = 5 MHz Bode_5
10 MHz Δ f = 10 MHz Bode_10
20 MHz Δ f = 20 MHz Bode_20
The measured data will be used to estimate:
1) Transfer Function of FC
2) Quantization noise from Power Spectral Density(PSD) vs Hz
To Do Next:
1)Complete interfacing the Pi with EPICS.
2)Make bode plots (Matlab script attached) and PSD plots and estimate the control parameters for optimal design of FOLL PID loop.
Rack 1Y2, I took transfer function measurements for each of the following demodulator boards: REFL11, REFL33, REFL55, REFL165, AS55, POP22, POX11 and POY11.
What I did:
1) Removed the wire at PD Input to demodulator board.
2) Put the MOD output from network analyzer into PD input of board.
3) Ran a sweep from 100kHz to 100MHz.
4) Measured the transfer function between PD RF MON and PD Input. (The PD RF MON signal came out of the RF multiplexer, so the mux is included as well )
5) Put the original wire back at PD Input.
The plots clearly show an attenuation of 20dB (factor of 10) for all the demodulator boards. This explains why my transimpedance measurements are off by 10 times.
Note: for REFL 165, there was an extra 100MHz high pass filter installed at PD Input. I did not remove this and made my measurements along with this.
a) Modify the PDFR system to calibrate out this attenuation.
b) Measure the transfer function between the input and output of RF mux, so that we can have just the transfer function between PD input an PD RF MON (for documentation's sake)
I repeated the exact steps above and made sure everything was back where it should be after I was done.
Reason I had to retake the measurements:
My script for acquiring data from the AG4395A network analyzer was such that it first acquired the magnitude data from channel 1 and then recorded phase data from channel 2 without holding its trace. Hence the phase and magnitude data were not exactly in sync with each other. So, when I tried to fit the data to a model using vector fitting, I ended up with very bad results.
I have now changed every single script relating to the network analyzer to just get the real and imaginary data in one go and then calculate the phase using this data.
The fitting process is now in progress and results will be up shortly.
The plots in the previous Elog includes delay and a little attenuation by RF cables and the RF mux.
Today I separately calculated the delay and attenuation for an RG405 cable (550 cm) and the RF mux(using really small RF cables). These delays should be accounted for when fitting the transfer function of Demodulator boards and transimpedance of PDs.
The plots are in both semilogx and linear.
EDIT by KI:
The definition of the recycling gain is wrong here.
See the latest entry (#5875)
Here is a summary about the Power Recycled Michelson (PRMI).
It seems the mode matching is also one of the greatest contributor on the low recycling gain.
+ Loss = 5.3% (or effective reflectivity of 93.28% in Michleson) => Under coupling !!
+ Mode matching efficiency = 47.4 % => Really bad !!
With these values we end up with a recycling gain of 7 and a normalized REFLDC of 0.5 as observed (#5773).
Also according the incident beam scan measurement (#5773) the loss is NOT a local effect like a clipping, it is more like uniformly distributed thing.
As for the mode matching, the number indicates that approximately the half of the incident light is coming back to the REFL port without interacting with PRMI.
This is bad because the non-mode-matched light, which is just a junk light, is entering into the photo detectors unnecessarily.
In the worst scenario, those junk light may create a funny signal, for example a signal sensitive to the alignment of PRM.
The method to estimate the loss and the MM (Mode-Matching efficiency) is essentially the same as before (#5541).
One difference from the previous estimation is that the I used more realistic parameters on the transmissivity of ITMs and PRM :
PRM : T = 5.637 % (see the 40m wiki)
ITM : T = 1.384 % (see the 40m wiki)
In addition to the basic calculations I also made plots which are handy for figuring out where we are.
Quantities we can measure are the reflected light from PRMI and the recycling gain using the REFL PD and the POY PD respectively.
So I wanted to see how the loss and MM can be estimated from the measured REFL DC and recycling gain.
The plots below are the ones.
The first figure shows a contour map of the loss as a function of the measured REFL DC and recycling gain.
The white area is a place where no proper solutions can be found (for example MM can get to more than 100 or loss becomes negative).
The star mark in the plot corresponds to the place where we are now. Obviously the loss is about 5%.
If we somehow decrease the amount of the loss the star mark will mostly go up in the plot.
The second figure shows a contour map of the MM as a function of the measured REFL DC and recycling gain.
The X and Y axis are exactly the same as that of the first plot. Again the star mark represents the place where we are.
We are currently at MM=47%
Here are some solutions to bring the recycling gain higher.
We don't work on these things immediately since it requires opening of the chambers again and it will take some times.
But we should think about those options and prepare some stuff for a coming vent.
+ Refinement of the position of the mode matching telescopes. => The Recycling gain can go up to 15.
=> Assuming the loss in the cavity doesn't change, the star mark in the first plot will go to the left hand side along the "0.05" black solid line.
=> However PRMI will be still under coupled.
=> Needs an estimation about which way we move the telescopes.
+ Locate the place of the dominant loss source and reduce it somehow.
=> The recycling gain will be more than 18 if the loss reduces by a factor of more than 5.
=> Needs a clever way to find it otherwise we have to do it in the classical way (i.e. white light and trying to find dirty surfaces)
Difficult to understand.
The mode matching does not change the recycling gain. It changes the coupling of the incident light into the cavity.
It changes the reflected and accumulated power, but the recycling gain is not affected.
The recycling gain is determined by the optical configuration and the optical loss in the cavity.
In the actual measurement, of course, we should take both of the loss and the mode matching into account.
But this is the issue of the measurement method.
The essential questions are:
How much is the actual recycling gain? And how does it affect the signal extraction?
How much is the actual recycling gain? And how does it affect the signal extraction?
As Koji pointed out I made a wrong definition on the recycling gain of PRMI (Power-Recycled Michelson Interferomter).
Reflectivity of PRMI (measured by REFLDC):
Power build up (measured by POY DC) :
Mode Matching (MM) efficiency :
Loss in the PRMI cavity :
(Results of Measurement and Estimation)
Estimated recycling gain = 15
Estimated MM efficiency = 47.4%
Estimated Loss = 5.3%
Measured power build Up = 7
Measured reflectivity of PRMI = 0.5
We first took data of a simple low pass filter, and attempted to perform a fit to both the magnitude and phase in order to find the Z of the components. Once we felt confident in our ability to measure tranfer functions, we took data and plotted the transfer function of the existing control loop of the AUX laser. What we found generally followed the trend of, but was lower than, 10^4/f, which is what we hoped to match, and also had a strange unexplained notch ~1.3 kHz. The magnitude and phase data both got worse after around 40-50 kHz, which we believe is because the laser came out of lock near the end of the run.
[Attachment 2 and 3] are the frequency response of the low pass filter, curves fitted using least squares in python.
[Attachment 1 and 4] is the same measurement of OLTF of the actual AUX circuit, and the control diagram pointing out the location of excitation and test point.
I have taken the charger for the dark gray dell laptop from its station, and have labelled the information there too.
Will keep it back tonight.
We did a quick check to make sure there is no saturation in the C1:SUS-ITMX_LSC_EXC analog path. For this, we looked at the SOS driver output monitors from the 1X4 chassis near MC2 on a scope. We found that even with 600 x 10 = 6000 counts of our 619 Hz excitation these outputs in particular are not saturating (highest mon signal was UL coil with 5.2 Vpp). In comparison, the calibration trials we have done before had 600 counts of amplitude, so we can safely increase our oscillator strength by that much
Things that remain to be investigated -->
In preparation for tomorrow's vent, I'm checking some of the OMC-related electronics we plan to use.
(well, technically the first up was the Kepco HV power supply... but I quickly tested that its output works up to 300V on a multimeter. The power supply for OMC-L-PZT is all good!)
According to the DCC, the nominal HV supply for this board is 200V; the board itself is printed with "+400V MAX", and the label on the HV supply says it was run at 250V. For now I'm applying 200V. I'm also supplying +-15V from a Tektronix supply.
I used two DB25 breakout boards to look at the pins for the DC and AC voltage monitors (OMC_Vmon_+/-, pins 1/6, and OMC_Vmon_AC+/-, pins 2 and 7) on a scope. I hooked up a DS345 function generator to the piezo drive inputn (pins 1,6). According to the 2013 diagram from the DCC, there is just one drive input, and an alternative "dither in" BNC that can override the DAC drive signal. I leave the alternative dither floating and am just talking to the DAC pins.
Aspects of the system seem to work. For example, I can apply a sine wave at the input, and watch on the AC monitor FFT as I shift the frequency. However, anything I do at DC seems to be filtered out. The DC output is always 150V (as long as 200V comes from the supply). I also notice that the sign of the DC mon is negative (when the Vmon_+ pin is kept high on the scope), even though when I measure the voltage directly with a multimeter the voltage has the expected (+) polarity.
A few things to try:
On further investigation this was the key clue. I had the wrong DCC document, this is an old version of this board, the actual board we are using is version A1 of D060283-x0 (one of the "other files")
Gautam and Koji returned at this point and we started going through the testpoints of the board, before quickly realizing that the DC voltage wasn't making it to the board. Turns out the cable was a "NULL" cable, so indeed the AC wasn't passing. We swapped out the cable, and tested the circuit with 30V from the HV supply to trim the voltage reference at U14. The minimum voltage we could get is 5V, due to the voltage divider to ground made by R39. We confirmed that the board, powered with 200V, can drive a sine wave and the DC and AC mons behave as expected.
I traced a cable from the OMC electrical feedthrough flanges to find the DCPD/OMMT Satellite Box (D060105). I couldn't find the DCC number or mention of the box anywhere except this old elog.
Gautam and I supplied the box with power and tested what we think is the bias for the PD, but don't read any bias... we tracked down the problem to a suspicious cable, labelled.
We confirmed that the board supplies the +5V bias that Rich told us we should supply to the PDs.
We tested the TFs for the board from the PD input pins to output pins with a 100kHz low pass (attached, sorry no phase plots). The TFs look flat as expected. The unfiltered outputs of the board appear bandpassed; we couldn't identify why this was from the circuit diagram but didn't worry too much about it, as we can plan to use the low passed outputs.
I went around 40m picking up any Sorensens that were laying around to test if they worked, or in need of repair. I gathered up a total of 7 Sorensens and each one with a Voltmeter. I made sure the voltage would rise on the Sorenson as well as the voltmeter, maxing out at ~33.4 Volts. For the current, the voltmeter can only rise to 10 Amps before it is fused. Many of the Sorensons that I found did not have their own wall connection, so I had to use the same one for multiple.
From these 7, I have found 5 that are well. One Sorenson I have tested has a output shortage above 20V and the other has yet to be tested.
Of the 7 Sorenson Power Supplies I tested, 5 are working fine, 1 cannot output voltage more than 20 Volts before shorting, and other does not output current. Six Sorensons are behind the X-Arm.
I have been checking the binary output switching for the SUS whitening filters. It appears that the whitening switching is working for (almost) all the vertex suspensions (BS, ITMX, ITMY, PRM, SRM), but not for the ETMs.
The table below lists the output from my switch-checking script (attached). The script uses the SUS digital lockin to drive one coil and measure the same coil's OSEM response, repeating for each coil/OSEM pair. I used a lockin drive frequency of about 10 Hz, at which the whitening filter should have 10 db of gain.
All but one of the vertex OSEMS show the proper response (~10db gain at 10Hz) when the whitening is switched on from the digital controls. ITMY UL appears to not be switching, which I fear is due to my electronics fail noted in my previous log post. The ETMs are clearly not switching at all.
I will try to get the ETM switching working tomorrow, as well as try to asses what can be done about the ITMY UL switch. After that I will work on confirming the coil drive dewhite switching.
freq: 10.123 Hz
I/Q filters: 0.1 Hz LP, 4-pole butterworth
ul : 3.31084503062 = 10.3987770676 db
ll : 3.34162124753 = 10.4791444741 db
sd : 3.43226254574 = 10.7116100229 db
lr : 3.28602651913 = 10.3334212798 db
ur : 3.29361593249 = 10.3534590969 db
ul : 3.37499773336 = 10.5654697099 db
ll : 3.2760924572 = 10.3071229966 db
sd : 3.13374799272 = 9.9212813757 db
lr : 3.28133776018 = 10.3210187243 db
ur : 3.37250879937 = 10.5590618297 db
ul : 0.99486434364 = -0.0447226830807 db
ll : 3.39420873724 = 10.6147709414 db
sd : 3.88698713176 = 11.7922620572 db
lr : 3.357123865 = 10.5193473069 db
ur : 3.37876008179 = 10.5751470918 db
ul : 3.26758918055 = 10.2845489876 db
ll : 3.32023820566 = 10.4233848529 db
sd : 3.25205538857 = 10.2431586766 db
lr : 3.24610681962 = 10.227256141 db
ur : 3.31311970305 = 10.4047425446 db
ul : 3.30506423619 = 10.3835980943 db
ll : 3.28152094133 = 10.3215036019 db
sd : 3.08566647696 = 9.7869796462 db
lr : 3.30298270419 = 10.378125991 db
ur : 3.3012249406 = 10.3735023505 db
ul : 0.99903400106 = -0.00839461539757 db
ll : 0.99849991349 = -0.0130393683795 db
sd : 1.00314092883 = 0.0272390056874 db
lr : 1.00046493718 = 0.00403745453682 db
ur : 1.00265600785 = 0.0230392084558 db
ul : 1.00223179107 = 0.0193634913327 db
ll : 0.96755532811 = -0.286483823189 db
sd : 1.00861855271 = 0.0745390477589 db
lr : 1.05718545676 = 0.483023602007 db
ur : 0.99777406174 = -0.0193558045143 db
from numpy import *