Since the RFM-Dolphin bridges for the ASX model was added to the c1rfm model, c1rfm kept timing-out from the single sample time of 60us.
The model had 19 dolphin accesses, 21 RFM accesses, and 9 shared memory (SHM) accesses.
At the beginning 2 RFM and 2 SHM accesses were moved to c1sus (i.e. they were mistakenly placed on c1rfm).
But this actually made the c1sus model timed out. So the model was reverted.
The current configuration is that the WFS related bridges were accommdated in the c1mcs model.
This made the timing of c1rfm ~40us. So it is safe now.
On the other hand, the c1mcs model has the time consumption of ~59us. This is marginal now.
We need to understand why any RFM access takes such huge delay.
As a part of the network analyzer test in the previous entry, the transfer functions of Mini-Circuits filters we have at the 40m were measured.
<<List of the filters>>
- LPF (SMA): SLP1.9, SLP5, SLP21.4, SLP30, SLP50, SLP100, SLP150, SLP750
- LPF (BNC): BLP1.9, BLP2_5, BLP5, BLP30
- BPF (SMA): SBP10.7, SBP21.4, SBP70
- HPF (SMA): SHP25, SHP100, SHP150, SHP200, SHP500
New AG4395, sn MY41101114 for West Bridge Labs was delivered. For the test purpose it is at the 40m now.
I made a series of tests in order to find anything broken.
Network analyzer test
- RF out / Rch test
RF out directly connected to R input channel.
The received power at the R-ch was measured while the output was swept from 10Hz to 500MHz.
The RF power was changed from -50dBm to +15dBm with +10dBm increment (but the last one).
The attenuator setting was changed from 50dB to 0dB.
=> The configured output power was properly detected by the R channel.
=> RF output is producing the signal properly. R-ch is detecting the produced signal properly.
- Ach/Bch test
Same test as above for Ach and Bch
=> Same result as above
=> A-ch and B-ch are detecting the produced signal properly.
- Transfer function test
Connect a power splitter to the RF out. Detect the split signals by R-ch and A-ch
=> Measurement is at around 0dB +/- 1dB up to 500MHz.
Same measurement for B-ch
=> Same result
=> A/R and B/R indicates proper transfer function measurements.
RF out was split in to two. One was connected to R-ch. The other was connected to A-ch.
The thru response calibration was run.
=> The thru calibration was performed properly.
- Practical tranfer function measurements.
In the above calibration setup, various RF filters were inserted in the Ach path.
The measured data was extracted via GPIB connection.
=> Practical transfer function measurements were performed.
=> GPIB connectivity was confirmed
External reference test
- External 10MHz reference from an SRS frequency counter was connected to Ext Ref In
=> Ext Ref indicator on the screen appeard
=> The internal oscillator seemed to be locked to the external reference in
Spectrum analyzer test
- Measured the signals from DS345 by R/A/B ch
Sinusoidal signal (1V) swept from 10MHz to 30Mhz
=> Corresponding moving peak was detected in each case
- Noise level measurement
R/A/B channels were terminated. The attenuation at each port was set to 0dB.
Frequency span was changed between 500MHz, 10MHz, 100kHz, 1kHz.
=> Noise level of ~10nV/rtHz between 0.1-500MHz was confirmed. All R/A/B channels have the same performance.
I aligned both the X and Y end green to the arms.
c1x01 timing issue was solved. Now all of the models on c1iscex are nicely running.
- c1x01 was synchronized to 1PPS in stead of TDS
- C1:DAQ-DC0_C1X01_STATUS (Upper right indicator) was red. The bits were 0x4000 or 0x2bad.
C1:DAQ-DC0_C1X01_CRC_SUM kept increasing
- c1scx, c1spx, c1asx could not get started.
- login to c1iscex "ssh c1iscex"
- Run "sudo shutdown -h now"
sudo shutdown -h now
- Walk down to the x end rack
- Make sure the supply voltages for the electronics are correct (See Steve's entry)
- Make sure the machine is already shutdown.
- Unplug two AC power supply of the machine.
- Turn off the front panel switch of the IO chassis
- Wait for 10sec
- Turn on the IO chassis
- Plug the AC power supply cables to the machine
- Push the power switch of the realtime machine
I routed cables (RG405 SMA-SMA) from several demodulator boards in rack 1Y2 to the RF Switch in rack 1Y1 using the overhead track. Our switch chassis contains two 8x1 switches. The COM of the "right" switch goes to channel 7 of the "left" switch to effectively form a 16x1 switch. The following is a table of correspondences between PD and RF Switch input.
ThePOP110 demod board has not yet had a cable routed from it to the switch because I ran out of RG405.
We should also consider how important it is to include MCREFL in our setup. Doing so would require fabrication of a ~70 ft RG405 cable.
This post pertains to the fiber-coupled diode laser mounted in rack 1Y1.
To turn the laser on, first turn the power supply's key (red) to the clockwise. Then make sure that the laser is in "current" mode by checking that the LED next to "I" in the "Laser Mode" box in lit up. If the light is not on, press the button to the right of the "I" light until it is. Now press the output button (green). This is like removing the safety for the laser. Then turn the dial (blue) until you have your desired current. Presently, the current limit is set to around 92 mA.
To turn the laser off, dial the current back down to 0mA and turn the key (red) counterclockwise.
For the RF PD Frequency Response Measurement project, we get each PD signal from the "PD RF Mon" output of each demodulator board corresponding to our PD under test. Therefore we can't neglect the frequency response of various filters inside the demodulator board. I used our Agilent 4395 Network Analyzer to gather frequency response data for each demodulator board being considered for the RFPD frequency response project (AS55, REFL11, REFL33, REFL55, REFL165, POX11, POP22, POP110).
The NA swept over a frequency range of 1-500 MHz. Data was collected using NWAG4395A (from the netgpibdata directory). It should be noted that the command line options -a 16 -x 15 (averaging=16 and excitation amplitude=15 dBm[the max]), in addition to the usual command line options described in the help file, were used to minimize noise.
The data is located in /users/alex.cole. The file names are in the format [PDNAME]DemodFilt_1000000.dat (e.g. REFL11DemodFilt_1000000.dat). Results for POP110 are shown below.
Our fluorecent lights became obsolete. We'll have change fixtures over to some more energy efficient one. Do you have any recommendation regarding to less noise performer unit?
We may go this direction of LED fluorecent lamps ?
Sorrensen ps ouput of +15V at rack 1X9 was current limited to 10.3V @ 2A
Increased threshold to 2.1A and the voltage is up to 14.7V
I guess I was thinking that POPDC was a proxy for any type of PRCL lock. Even if we're sideband locked, there is still some signal in POPDC (although it is very small relative to a carrier lock - ~40cts vs. 1,000cts). However, as soon as this question was asked of me, I realized that one of the 2f demodulated signals made more sense.
Since I want the ability to choose between POP110 and POP22, I have put a little 1x3 input matrix before the PRCL lockins in the ASS model. Since POPDC was already there, I included it as an option in the matrix (in case we ever want to do some PRCL ASS after we have some carrier resonating as well).
I started to modify the c1asx model to reduce the RFM model from hitting its max time.
Instead of bringing in ASS, I have modified ASX to do everything and only the clock signals to ITMX pitch and yaw are now going through RFM. RFM is still hitting 62usec and I suppose that is because of the problems with c1iscex.
c1iscex not happy
Cause and symptoms
While restarting the models, c1iscex crashed a couple of times because of some errors and had to be powercycled. The models were modified and they seem to start ok.
But it looks like there is something wrong with c1iscex since the models were started. The GPS time is off and C1:DAQ-DC0_C1X01_CRC_SUM keeps building up even for c1x01 which was left untouched.
1. Since c1x01 ans c1spx were not touched,c1scx and c1asx were killed and we tried to start the other models. This did not help.
2. Koji did a manual daqd restart which did not help either.
We are leaving c1iscex as is for the time being and calling Jamie for help.
P.S. While making the models, I had created IPCx_PCIE blocks in c1iscex which do not exist. I changed them to RFM and SHMEM blocks. This did not allow me to compile the model and was only spitting errors of IPCx mismatch. After some struggle and elog search I figured out from an old elog that eventhough the IPCx blocks are changed in the model, the old junk exists in the ipc file in chans directory. I deleted all junk channels related to the ASX model. The model compiled right away.
I have added the PRCL ASS to the main ASS screen, and created the servo and lockin screens. The filters loaded are the same as those used for the arms (bandpasses and lowpasses for the lockins, and an integrator for the servo).
I'm going to try to lock, and get the ASS to work.
- We are ready to implement ASS for PRM
I have added an IPC sender from the LSC model, to send POPDC to ASS. I have copied over the structure of the arms' ASS, to do the same for PRCL. I have set it up to dither the PRM, and feed back to the PRM. I did not include an LSC set, since I'm assuming that we'll set the input pointing with the arms, and just want to move the PRM to maximize POPDC.
Models have been compiled, installed, and restarted, and the daqd was restarted.
I'm not really sure why the ASS was involved in this. I feel like it might have been simpler to just do everything in the ASX model, to keep things cleaner. Also, the IPC blocks for this stuff (in both ASS and ASX) are not on the top level of the model. I had thought that this was expressly forbidden (although I'm not sure why). I'm emailing Jamie, to see if he remembers what, if anything, is breakable if the IPC blocks are down a level.
I'm not sure if it's forbidden by the RCG, but you should definitely NOT do it. All IO, whether it be between ADC/DACs or IPCs, should always be at the model top level. That's what keeps things portable, and makes it easier to keep track of where are signals are going/coming from.
Getting rid of the LO transmission will certainly help / be good. After adding these channels, the RFM model is regularly hitting 62usec (out of a max acceptable of 60).
In the past, we used to use Stefan's 'ezcademod' or Matt's 'ezlockin' to do auto phase adjustment.
JoeB / Jamie are working on python replacements for these tools, but in the near term possibly I can make a bash script to use ezcaservo and the existing LOCKINs to do this.
Over the last three days, I've had the interferometer to test and optimize the ASX Servo. Based on what I have seen, I think the conclusion is that with the current parameters, the servo does its job provided the input pointing set up at the endtable with the coarse adjustment knobs is reasonably good. Once the cavity is aligned and IR transmission maximized using ASS, I have been able to get the green transmission up to 0.8 which is close to the best we had pre-vent. I have not been elogging regularly over the last few days, so this one is going to be a longish one.
Major changes made:
Details of tests runs:
For the most part, I have been trying to optimize the PZT mirror dither servo. To this end, I did the following:
Attempt to measure transfer function:
One of the things that came up during my presentation was how fast the loop was capable of responding. I was able to get a quantitative idea of this by playing around with the overall servo gain. Initially, it took ~30 seconds for the servo to get the transmission up to its peak value, with a servo gain of 1. When I ramped this up to 5, the response was much faster, with the peak transmission being reached in ~5seconds.
I wanted to get a more quantitative picture, and hence tried to measure the transfer function by first injecting an excitation into the 'SIG' filter-bank in the demodulation stage. However, coherence between the IN1 and IN2 signals was very poor for all the amplitude configurations I tried. At Jenne's suggestion, I tried injecting the excitation at the control-filters stage, but found no improvement. Perhaps the amplitude envelope was wrong or the measurement technique has to be rethought.
New MEDM screen:
PRMI(sb) lock was recovered
- Stared at the time series data of the REFL demod signals, and decided to use REFL165I&Q for the locking.
- Jiggled the demodulation phase of REFL165 and POP110. Changed the servo gains.
- Finally found a short lock. Further optimized the parameters.
- PRM ASC was turned on by giving the identity matrices for the input and output matrices.
Now just hitting the up button is sufficient to engage the ASC servo.
- Under the presence of the ASC, the PRMI is indefinitely locked as before.
- Reacquisition is also instantaneous. (It acquires even if the ASC is left "on".)
- Actually the lock is somewhat robust even when the PRM ASC is not used.
This is VERY GOOD as we can skip one of the steps necessary for the full lock.
Although, the seismic on Friday night is very quiet.
The spot motion at POP seems to be somewhat pitch/yaw mixed, in stead of previous "totally-dominated-by-yaw" situation.
Demod phase adjustment
- Shook PRM at 580Hz / 100cnt
- Swept the demod phase of REFL165 such that the PRM peak is minimized in the Q signal
- Open DTT. Measured transfer functions between REFL165I and the Q signals of each PD.
- Minimized the PRCL signal coupling in the signals.
- The resolution of the adjustment was ~1deg.
Locking test with PRM/BS
Tried the lock acquisition only with PRM and BS. (cf. http://nodus.ligo.caltech.edu:8080/40m/8816)
This just worked nicely.
Today's locking parameters:
MC Trans: 17500
POP110I (in lock): 150
PRCL Source: REFL165(I) 106deg / 45dB / Normalization SQRT(10 POP110I) / Input MTRX 1.0
PRCL Trigger: POP110I x 1.0 50up 25down
PRCL Servo: G=+3.5 Acq: FM4/FM5 Opr: FM2/FM3/FM6/FM7
PRCL Actuator: PRM +1.0
MICH Source: REFL165(Q) 106deg / 45dB / Normalization SQRT(0.1 POP110I) / Input MTRX 1.0
MICH Trigger: POP110I x 1.0 50up 25down
MICH Servo: G=-10 Acq: FM4/FM5 Opr: FM2/FM3/FM6
MICH Actuator: (ITMX -1.0 / ITMY +1.0) or (BS 0.5 / PRM -0.267)
Now the SRM Yaw bias in yaw is functional without any strage behavior.
The problem was found at the connector of the flat ribbon cable from the DAC to the cross connect.
I used the extender board to diagnose the SRM coil driver circuit at 1X4.
The UL coil input did not show any sign of voltage no matter how the bias slider was jiggled.
I opened the side panel of the rack and found the signal was absent at the cross connect which relays two flat ribbon cables
for the SRM coil driver. I checked the DAC output with a multimeter. All the bias outputs were OK at the DAC.
Then I opened the IDC connector at the DAC side of the crossconnect as the signal was already missing there.
I found that the flat ribbon cable was a half line shifted from the supposed location.
This resulted a short circuit of the DAQ +/- pins for the SRM UL coil.
I recrimped the connector and now the SRM Yaw slider is back.
This changed the nominal position of the SRM. The new slider values were saved.
Notes to the fiber team:
I am aligning beam onto the RFPDs (I have finished all 4 REFL diodes, and AS55), in preparation for locking.
In doing so, I have noticed that the fiber lasers for the RFPD testing are always illuminating the photodiodes! This seems bad! Ack!
For now, I blocked the laser light coming from the fiber, did my alignment, then removed my blocks. The exception is REFL55, which I have left an aluminum beam dump, so that we can use REFL55 for PRM-ITMY locking, so I can align the POP diodes.
EDIT: I have also aligned POP QPD, and POP110/22. The fiber launcher for POP110 was not tight in its mount, so when I went to put a beam block in front of it and touched the mount, the whole thing spun a little bit. Now the fiber to POP110 is totally misaligned, and should be realigned.
What was done for the alignment:
1. Aligned the arms (ran ASS).
2. Aligned the beam to all the REFL and AS PDs.
3. Misaligned the ETMs and ITMX.
4. Locked PRM+ITMY using REFL11.
The following were modified to enable locking
(1) PRCL gain changed from +2.0 to -12.
(2) Power normalization matrix for PRCL changed from +10.0 to 0.
(3) FM3 in PRCL servo filter module was turned OFF.
5. POP PDs were aligned.
- IPANG aligned on the QPD. The beam seems to be partially clipped in the chamber.
- Oplev of the IFO mirrors are aligned.
- After the oplev alignment, ITMX Yaw oplev servo started to oscillate. Reduced the gain from -50 to -20.
I used MC_L signal from the Mode Cleaner as the desired signal with GUR2_X as witness signals. I observed good subtraction where coherence is high. But there was noise added in other frequency bands. I am not sure how to avoid that.
Please find attached documents that contains relevant plots.
An exercise of optimally subtracting one seismometer signal by another using weiner filters was done. Results have been summarized document attached.
I was receiving missing path error when I was trying to measure the MC spot positions. Jenne pointed out that Koji had moved all the unused scripts in scripts/ASS to /scripts/ASS/OBSOLETE yesterday and in the process one of the scripts that the MC spot position measurement script calls for (MeasureSpotPositions.py) must have also been moved to the OBSOLETE directory. I moved the script to /scripts/ASS/MC so that we know the script is being used and also changed its path in the main script.
1, Vacuum envelope grounds must be connected all times! After door removal reconnect both cables immediately.
2, The crane folding had a new issue of getting cut as picture shows.
3, Too much oplev light is scattered. This picture was taken just before we put on the heavy door.
4, We were unprepared to hold the smaller side chamber door 29" od of the IOC
5, Silicon bronze 1/2-13 nuts for chamber doors will be replaced. They are not smooth turning.
TP2's fore line - dry pump replaced at performance level 600 mTorr after 10,377 hrs of continuous operation.
I have done some preliminary testing of the X-End Green ASS Servo. I will write a more detailed elog about this soon, but I thought I'd note down the important stuff here.
Yesterday, while we were venting, I aligned the X-arm to the green using the sliders on IFOalign, maximizing the transmission. Then I retook a power spectrum so as to determine the LO frequencies. Jenne pointed out that LO frequencies should not be integers (it usually suffices to append a .098725 or something to the frequency) so I made the necessary changes.
I did a first run of the servo yesterday, and more runs today. Notable points:
More details to follow.
While Gautam is working on the Xarm green ASS...
The EPICS monitor points for the ASS actuators were added to the ASS model.
This will be used for the offloading the ASS actuations to the alignment biases.
As this modification allowed us to monitor the actuation apart from the dithering,
now we can migrate the ASS actuation to the fast alignment offset on the suspension.
This modification to the offset moving scripts were also done.
We have looked a little more at the SRM situation. We aligned the SRM, and then aligned the oplev, so that we had a convenient monitor of the optic's motion.
When we use the _COMM channels, which are the usual ones on the IFO_ALIGN screen, the pitch slider makes pitch motion, but the yaw slider makes the oplev spot move ~45degrees from horizontal.
However, when we use the bias channels that are in the front end model, parallel to the ASC path, pitch moves pitch, and yaw moves pure yaw.
So, we conclude that the SRM coils are fine, and there is something funny going on with the slow part of the actuation.
Koji restarted the slow computer susaux, and burt restored it, but that did not fix the situation. We went inside and looked at all of the ribbon cable connections, and pushed them all in, but that also has not fixed things.
We have been looking at D010001-b, the coil driver board, and we think that's where the summing resistor network between the slow bias slider, and the coil outputs from the fast model exists. (It's not 100% clear, but we're confident that that's what is going on).
Tomorrow, we will pull the SRM's coil driver board, and see if any of the components in the slow slider path, before the summing point, look burned / broken / bad.
I have furthered Koji's work, and moved the filter on/off state for all the filter banks also to the burt snapshot.
Turning on the ASS is now much faster than it was originally, with the ezcawrites in series.
For the photodetector frequency response project, our new RF Switch Chassis (NI pxie-1071) arrived today. I took the switches out of the old chassis (Note for future generations: you have to yank pretty darn hard) and put them in the new chassis, which I mounted in rack 1Y1 as pictured.
The point of this new chassis is that its controller is compatible with our control room computer setup. We will be able to switch the chassis using TCP/IP or telnet, aiding in our automation of the measurement of photodetector frequency response.
Where are the foreline pressure gauges? These values are not on the vac.medm screen.
The new tip seal dry pump lowered the small turbo foreline pressure 10x
TP2fl after 2 day of pumping 65mTorr
I moved bunch of ezcawrite from the ASS Dither On script to a snapshot file.
This accelerated a half of the "up" time but still switching part is not in the snapshot.
If you find anything wrong with ASS, please notify me.
Cold cathode gauge CC1 -h (horizontal) just coming on 9.2e-5 Torr
P2 is the fore line pressure of the maglev. One can see the 4 Torr load during switching over to turbo pumping.
CC4 5e-9 Torr is the performance of the maglev pumping on the RGA only.
The annuloses are not pumped now. They are closed off to see how much outgassing plus leak they have.
Configuration: vacuum normal, annuloses not pumped
Precondition: 14 days at atm, IOO chamber north door was taken off as a new entrance, the ETMX chamber was not opened.
What is new in the vacuum system: new P1 pirani gauge, gold plated clean allen wrench and ..........what else was dropped?
Note: the wireless laptop did not fail once all day yesterday. I want to give credit to the person who is responsible for this.
I have a concern about the SRM suspension. The yaw alignment bias produces huge pitch coupling.
This could be a connector issue or the rubbing of the mirror on the EQ stops.
We have the photos of the magnets and they were not touching the OSEMs.
[Koji, Manasa, Jenne]
The Y arm was locked in IR, and we saw flashing in the Xarm (Gautam had the Xarm for green work when we began). I checked IPANG, and the beam was beautifully unclipped, almost perfectly centered on the first out of vacuum mirror. I aligned the beam onto the QPD.
We then swapped out the MC Y1 that we use at low power, and replace the usual 10% BS, so that we wouldn't crispy-fry MC REFL. Manasa adjusted the half wave plate after the laser, to maximize the power going toward the PMC. We relocked the PMC, and see transmission of ~0.84, which is at the high side of what we usually get. The beam was aligned onto MC REFL and centered on the WFS, and the MC was locked at nominal power. Koji tweaked up the alignment of the MC, and ran the WFS offset script. I aligned beam onto POP QPD and POP110 coarsely (using a flashing PRC, not a locked PRM-ITMY cavity, so the alignment should be rechecked). The arms have both been locked and aligned in IR....the green beams need to be steered to match the current cavity axis.
The AS beam, as well as REFL and POP, are all coming out of the vacuum nicely unclipped.
Notes: When Koji was aligning the SRM to get the SRC cavity roughly aligned (the AS flashes all overlapping), we noticed that there is some major pitch-yaw coupling. Serious enough that we should be concerned that perhaps some connector is loose, or an actuator isn't working properly. This should be checked.
Moral of the story: Coarse alignment of all mirrors is complete after pump-down and we have IR locked and aligned to both arms at nominal power.
Still to do:
* Restore PRM, align beam onto the REFL PDs.
* Lock PRM-ITMY cavity, align beam onto POP PDs.
* Align AS beam onto AS55.
* Recenter all oplevs.
* Recenter IPPOS and IPPANG at nominal power.
* Start locking!!
IFO P1=1mT PSL shutter is opened
I redid the power spectrum measurement for the X-arm green transmission after aligning the arm to green using the ITMX/ETMX Pitch and Yaw sliders on IFOalign.
The Y-axis now reflects the relative intensity noise (RIN), which I obtained by taking the average value of the X-arm green transmission using tdsavg. Based on this measurement, I have now picked four new frequencies at which to try and modulate the PZT mirrors: 10, 19, 34 and 39 Hz. Bandpass filters in the LIA stage have been appropriately modified.
For the photodetector frequency response project, I finished the construction of our baluns chassis and mounted it in rack 1Y1 (1st picture).
After consulting with Jenne, I mounted the fiber launcher for REFL165 on the AS table such that it would not cause an obstruction. I aligned the launcher using a multimeter to monitor the DC output of REFL165, but looking at the data I got, it seems I need to do a better alignment/focusing job to get rid of a bunch of noise.
The pumpdown has started at 8:38am
Manasa was here to confirm good alignment of the IFO
Inner jam nuts of AC bellow were torqued to 45 ft/lbs and door nuts were check on opened chambers.
Annulos were roughed down to 500 mTorr
Oplev servos turned off, PSL and green shutters closed before pumpdown started
I did an alignment check of the IFO before we start pumping down.
Arms were locked. PRM and SRM were aligned. Green was aligned to the arms for reference during the pump down.
Steve! It's a GO!
MC spot positions:
Oplevs were all centered yesterday and haven't drifted much. So I left them as is.
QPDs (IPPOS aligned from yesterday.
- I suppose the green transmission paths were thoroughly inspected and aligned in prior to the measurement
- Of course it is a BAD idea to use 60Hz as the LO frequency.
- Power spectra should be plotted as "RIN (relative intensity noise)" as the DC of 1 and 100 gives you 100 times different power spectra for the same beam.
Don't forget to subtract the offset from your DC values.
I had prepared two more PZT mounted mirrors for the Y-end some time back. These are:
I used the same QPD set-up and the methodology described here to do a full-range calibration of these PZTs. Plots attached. The calibration constants have been determined to be:
CVI-pitch: 0.316 mrad/V
CVI-yaw: 0.4018 mrad/V
Laseroptik pitch: 0.2447 mrad/V
Laseroptik yaw: 0.2822 mrad/V
CVI YAW CVI PITCH
Laseroptik YAW Laseroptik PITCH
In order to decide what frequencies to dither the 4 degrees of freedom (M1-pitch&yaw, M2-pitch&yaw) at, I took the power spectrum of the X and Y-arm green transmission (C1:ALS-TRX_OUT, C1:ALS-TRY_OUT). Plots showing the power spectra are attached. Looking at the power spectra, I would think that for the X-arm, it would be okay to dither at 40, 50, 60 and 70 Hz. In order to check if the piezos could respond to these frequencies, I used my QPD setup and shook the PZTs with a 100Hz, 1Vpp sinusoid, and saw that the spot moved smoothly on the QPD.
As for choosing the modulation amplitude, I did a simplistic approximation assuming that the misalignment only rotates the beam axis relative to the cavity axis, and determined what angle coupled 10% of the power into the next eigenmode. Assuming that this is small enough such that if we are already locked to TEM00, the dither won't kick it up to some higher-order mode, the LO amplitude should be in the range of 30-60 digital counts (determined using the PZT calibration constants determined here. This corresponds to a sine-wave of ~50mV amplitude reaching the PZTs (after HV amplification). I am not sure if this is too small, but according to the PZT datasheet, these platforms are supposed to have a resolution of 0.02 urad, which would correspond to the input signal changing by ~0.1 mV, so this signal should be capable of dithering the tip-tilt.
I have already added band-pass filters centered at these frequencies to the model (with a passband of 5Hz, 2Hz on either side), and low-pass filters to pull out the DC component of the output of the lock-in amplifiers. It remains to tune the gains of the filter stages. These parameters (frequency, amplitude of the LOs) may also have to be changed after tests). Hopefully the PZTs can be plugged in tomorrow, and I can try and make a measurement of the output matrix.
Koji also suggested that it may be good to have a path in the model that feeds back to the PZTs by dithering the cavity mirrors as opposed to the PZT mounted mirrors. I will work on incorporating this into the SIMULINK model (c1asx.mdl) and also into the master medm screen.
Power Spectra of Arm Green Transmission:
GET CAMERA IMAGES OF EVERYTHING
Check all OpLevs centered, in and out of vacuum
IPANG needed to be re-aligned today. Heavy doors are in place and bolts tight (torque 25 & 45).
Steve! We are ready for pump down!
I will check the IFO alignment once again early tomorrow morning before Steve starts pumping down.
I goofed on the transfer function requirement by not giving you the plant transfer function, which looks to be about 0.014 V/V, independent of frequency (PSL:1278). This needs to be compensated for in the electronic transfer function.
RGA background at day 12 of this vent . The maglev is pumping on the rga through VM2