This morning (about 10am to 11am), I have collected additional transfer function measurements for the T.T. suspension. I have finished taking my measurements. The SR785 has been returned to its place next the the seismometer racks.
The data has been backed up onto the cit40m computer
Excited all optics - -
Fri Aug 12 03:34:12 PDT 2011
[Suresh / Kiwamu]
We tried adjusting the OSEMs on PRM, but we didn't complete it due to a malfunction on the coils.
The UL and LL coils are not working correctly, the forces are weak.
Tomorrow we will look into the satellite box, which is one of the suspects.
During the adjustment we found that the POS excitation force was unequal in each sensor.
At the beginning we thought it's because of the difference of the sensitivity in each OSEM due to the bad OSEM orientations.
However it turned out that it comes from the actual force imbalance on each coil.
We checked the force of each coil by putting an offset (-2000 cnts) in each output digital filter and looked at the OSEM signals in time series.
The UL and LL coils are too weak and the responses are almost buried in the noise of the OSEMs in time series.
We briefly checked some analog electronics and found the DAC, AI board and deWhitening board were healthy.
We were able to see the right amount of voltage from the monitor pin on the front panel of the coil driver.
So something downstream are suspicious, including the satellite box, feedthrough and coils.
- - -
Although the coil issue, it could be worth trying to check the input matrix.
DMass and I locked the NPRO laser (Model M126-1064-700, S/N 238) on the AP table to the reference cavity on the PSL table using the PDH locking setup shown in the block diagram below (the part with the blue background):
A Marconi IFR 2023A signal generator outputs a sine wave at 230 kHz and 13 dBm, which is split. One output of the splitter drives the laser PZT while the other is sent to a 7dBm mixer. Also sent to the mixer is the output of a photodiode that is detecting the reflected power from off the cavity. (A DC block is used so that only RF signal from the PD is sent to the mixer). The output of the mixer goes through an SR560 low-noise preamp, which is set to act as a low pass filter with a gain of 5 and a pole at 30 kHz. That error signal is then sent to the –B port of the LB1005 PDH servo, which has the following settings: PI corner at 10kHz, LF gain limit of 50 dB, and gain of 2.7 (1.74 corresponds to a decade, so the signal is multiplied by 35). The output signal from the LB1005 is added to the 230 kHz dither using another SR560 preamp, and the sum of the signals drive the PZT.
I am monitoring the transmission through the cavity on a digital oscilloscope (not shown in the diagram) and with a camera connected to a TV monitor. I sweep the NPRO laser temperature set point manually until the 0,0 mode of the carrier frequency resonates in the cavity and is visible on the monitor. Then I close the loop and turn on the integrator on the LB1005.
The laser locks to the cavity both when the error signal is sent into the A port and when it is sent into the –B port of the PDH servo. I determined that –B is the right sign by comparing the transmission through the cavity on the oscilloscope for both ways.
When using the A port, the transmission when it was locked swept from ~50 to ~200 mV (over ~10 second intervals) but had large high frequency fluctuations of around +/- 50 mV. Looking at the error signal on the oscilloscope as well, the RMS fluctuations of the error signal were at best ~40 mV peak to peak, which was at a gain of 2.9 on the LB1005.
Using the –B port yielded a transmission that swept from 50 to 250 mV but had smaller high frequency fluctuations of around +/- 20 mV. The error signal RMS was at best 10mV peak to peak, which was at a gain of 2.7. (Although over the course of 10 minutes the gain for which the error signal RMS was smallest would drift up or down by ~0.1).
The open loop error signal peak-to-peak voltage was 180 mV, which is more than an order of magnitude larger than the RMS error signal fluctuations when the loop is closed, indicating that it is staying in the range in which the response is linear.
In the above plot the transmission signal is offset by 0.1 V for clarity.
Below is the closed loop error signal. The inset plot shows the signal viewed over a 1.6 ms time period. You can see ~60 microsecond fluctuations in the signal (~17 kHz)
The system remained locked for ~45 minutes, and may have stayed locked for much longer, but I stopped it by opening the loop and turning off the function generator. Below is a picture of the transmitted light showing up on a monitor, the electronics I'm using, and a semi-ridiculous mess of wires.
I determined that it’s not dangerous to leave the system locked and leave for a while. The maximum voltage that the SR560 will output to the PZT is 10Vpp. This means that it will not drive the PZT at more than +/-5 V DC. At low modulation rates, the PZT can take a voltage on the order of 30 Vpp, according to the Lightwave Series 125-126 user’s manual, so the control signal will not push the PZT too hard such that it’s harmful to the laser.
We moved the seismometer STS2(Bacardi, Serial NR 100151) as we told in this Elog Entry, so the distance between Guralp1 and STS2 is 31.1m. Following is the coherence plot for this case:
then we also moved the Guralp1 under the BS and plugged it with the Guralp2 cable (at 7:35pm PDT), so now the distance between the two seismometers is 38.5m. Following is the coherence plot for this case:
We moved the STS2(Bacardi, Serial NR 100151) to his new location and laid his cable from rack 1X7 to ETMX. The seismometer was below the mode cleaner vacuum tube before.
Now, (since 6:05pm PDT) its placed near the ETMX.
We started an ITMX freeswing run at this time
Thu Aug 11 18:58:59 PDT 2011
But the optic did not repond to the kick. It is possible that the earthquake stops are close to the face and/or rear of the optic and prevent it from oscillating. We will check again and see what is up in a few hours.
ITMX OSEMs were adjusted so as to have the right DC numbers and the more uniform response to POS excitation.
It is waiting for the free-swinging test.
- ITMX was moved from its position to the north side of the table.
- The table was rebalanced.
- We found that the output of the LR OSEM has an excess noise compared with the other OSEMs.
We tried to swap the LR and SD OSEMs, but the SD OSEM (placed at the LR magnet) showed
the same excess noise at around 10-50Hz.
- We found that one of the EQ stops was touching the mirror. By removing this friction, all of the OSEMs
come to show similar power spectra. Good!
- Then we started to use LOCKIN technique to measure the sensitivity of the OSEMs to the POS excitation.
Originally the response of the OSEMs was as follows
UL 3.4 UR 4.3
LL 0 LR 2.5
After the adjustment of the DC values, final values became as follows
UL 3.9 UR 4.4
LL 3.9 LR 3.2
- We decided to close the light door.
Following is the power spectrum plot (with corrected calibration [see here]) of seismometers Guralp1 and STS2(Bacardi, Serial NR 100151):
The seismometers are placed approximately below the center of the mode cleaner vacuum tube.
Finally, we have found the correct calibration of Guralp and STS2 seismometers.
ADC: 216counts = 20V Hence, calibration of ADC is 3.2768e+03 counts/V.
Sensitivity of seismometer = 800 V/ms-1
Gain of the guralp breakout box (reference elog entry) = 20
Calibration = 3.2768e+03 counts/V x 800 V/ms-1 x 20 = 52428800 counts/ms-1 -----> 1.9073e-08 ms-1/count
Sensitivity = 1500 V/ms-1
Gain of the STS electronic breakout box = 10
Calibration = 3.2768e+03 counts/V x 1500 V/ms-1 x 10 = 49152000 counts/ms-1 -----> 2.0345e-08 ms-1/count
All of my plots have already taken into account the calibration of the photosensor (V/mm ratio)
Here is a bode plot generated for the transfer function measurements we obtained last night/this morning. This is a bode plot for the fully-assembled T.T. (with flexibly-supported dampers and bottom bar). I will continue to upload bode plots (editing this post) as I finish them but for now I will go to sleep and come back later on today.
Here is a bode plot comparing the no eddy-current damper case with and without the bar that we suspected to induce some non-uniform damping. We have limited data on the NO EDC, no bar measurements (sine swept data from 7 Hz to 50 Hz) and FFT data from 0 Hz to 12.5 Hz because we did not want to induce too much movement in the mirror (didn't want to break the mirror). This plot shows that there is not much difference in the transfer functions of the TT (no EDC) with and without the bar.
From FFT measurements of the no eddy-current damper case without the bar (800 data points, integrated 10 times) we can define the resonance peak of the TT mirror (although there are still damping effects from the cantilever blades).
The largest resonance peak occurs at about 1.94 Hz. The response (magnitude) is 230.
The second-largest resonance peak occurs at about 1.67 Hz. The response (magnitude) is 153. This second resonance peak may be due to pitch motion coupling (this is caused by the fact that the clamping attaching the mirror to the wires occurs above the mirror's center of mass, leading to inevitable linear and pitch coupling).
Here is a bode plot of the EDC without the bar. It seems very similar to the bode plot with the bar
Here is a bode plot of the rigidly-supported EDC, without bar. I need to do a comparison plot of the rigid and flexibly-supported EDCs (without bar)
The horizontal trolley drive stopped working at the east end this morning. It is working intermittently. In the worst case we can take the door off with the manual -Genie- lift.
I'm working with Konecrane to solve the wormgear drive problem.
Gear box found, it's lead time one week at $825 The crane may be functional round August 25
The entry was quite confusing owing to many misleading wordings.
- The PS2 should be calibrated "as is". (i.e. should be calibrated with the frame)
- The previous calibrations with the highly reflective surface were 0.32V/mm and 0.26V/mm, respectively.
This time you have 0.10V/mm (with an undescribed surface). The ratio is not 32 but 3.2.
- The DC output of PS2 on the shaking setup was 2.5V. The DC output seen in the plot is 3.5V-ish.
This suggests the possibiliteies:
1) The surface has slightly higher reflectivity than the frame
2) The estimation of the distance between the frame and the PS2 during the TF measurement was not accurate.
- The word "DC coupling level" is misleading. I guess you mean the DC value of the vbration isolation transfer function
of the suspension.
I have re-calibrated the photosensor I used to measure the displacements of the TT frame (what I call "Photosensor 2").
As before, the linear region is about 15.2mm to 25.4mm. It is characterized by the slope -0.0996 V/mm (-0.1 V/mm). Recall that photosensor 1 (used to measure mirror displacements) has a calibration slope of -3.2V/mm. The ratio of the two slopes (3.2/0.1 = 32). We should thus expect the DC coupling level to be 32? This is not what we have for the DC coupling levels in our data (2.5 for flexibly-supported, fully-assembled TT (with EDC, with bar), 4.2 for EDC without bar, 3.2 for rigid EDC without bar, 3.2 for no EDC, with bar, 3.2 for no EDC without bar) . I think I may need to do my calibration plot for the photosensor at the frame?
I have redone the voltage versus displacement measurements for calibrating "Photosensor 2" (the photosensor measuring the motions of the TT frame). This time, I calibrated the photosensor in the exact position it was in during the experimental excitation ( with respect to the frame ). I have determined the linear region to be 15.2mm to 22.9mm (in my earlier post today, when I calibrated the photosensor for another location on the frame, I determined the linear region to be 15.2mm to 25.4mm). This time, the slope was -0.92 V/mm (instead of -0.1 V/mm).
This means that the calibration ratio for photosensor 1 (measuring mirror displacements) and photoensor 2 (measuring frame displacements) is 34.86.
Since this "unity" value should be 34.86 for my transfer function magnitude plots (instead of the ~3 value I have), do I need to scale my data? It is strange that it differs by an order of magnitude...
Following is the coherence plot obtained when Guralp1 and STS2(Bacardi, Serial NR 100151) are placed very close to each other (but they aren't touching each other):
The seismometers were placed as shown in the picture below:
They are placed below the center of the mode cleaner vacuum tube.
The spot positions on the MC mirrors were adjusted by steering the MC mirrors, resulting in 1 mm off-centering on each optic.
One of the requirements in aligning the MC mirrors is the differential spot positions in MC1 and MC3.
It determines the beam angle after the beam exists from MC, and if it's bigger than 3 mm then the beam will be possibly clipped by the Faraday (#4674).
The measured differential spot positions on MC1 and MC3 are : PIT = 0.17 mm and YAW = 1.9 mm, so they are fine.
(Measurement and Results)
Suresh and I aligned the MC cavity's eigen axis by using MCASS and steering the MC mirrors.
Most of the alignment was done manually by changing the DC biases
because we failed to invert the output matrix and hence unable to activate the MCASS servo (#5167).
Then I ran Valera's script to measure the amount of the off-centering (#4355), but it gave me many error messages associated with EPICS.
So a new script newsensedecenter.csh, which is based on tdsavg instead of ezcaread, was made to avoid these error messages.
The resultant plot is attached. The y-axis is calibrated into the amount of the off-centering in mm.
In the plot each curve experiences one bump, which is due to the intentional coil imbalance to calibrate the data from cnts to mm (#4355).
The dashed lines are the estimated amount of off-centering.
For the definition of the signs, I followed Koji's coordinate (#2864) where the UL OSEM is always in minus side.
After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away)
We just checked with a function generator the calibration of the ADC. We set a square wave with amplitude 1V. We measured the voltage with the oscilloscope and we found on the data viewer that one volt is 3208 counts. That's what we expected (+/- 10V for 16bits) but now we are more sure.
We turned off the power of the seismometers and moved the Guralp1 close to the STS. Both are now situated below the center of the mode cleaner vacuum tube.
We oriented the X axis of the STS & Guralp1 along the X axis of the interferometer. Then we turned on the power again, but the STS channels don't give any signal. We think this is, because we didn't push the auto zero button.
After pressing the auto-zero button (a lot of times) of the STS breakout box & aligning the bubble in the STS, we could finally get data from STS (Bacardi). So, now STS2 (Bacardi - Serial NR. 100151) is working!
I'm pretty sure that don't have any ADC's with this gain. It should be +/- 10V for 16 bits.
Jenne told us that the ADC was +/- 2V for 16 bits so our calibration is wrong. Since, the ADC is +/- 10V for 16 bits we need to change our calibration and now we can also use the purple STS breakout box.
New calibration for Guralp:
ADC: 216counts = 20V Hence, calibration of ADC is (215x0.1) counts/V.
Sensitivity = 800 V/ms-1
(215 x 0.1) counts/V x 800 V/ms-1 = 2621440 counts/ms-1 -----> 3.8147e-07 ms-1/count
Calibration = 3.8147e-07 ms-1/count
Using the above calibration we obtain the following plot:
When we compare this plot with the old plot (see here) we see that in our calibration, we have got a factor of 10 less than the old plot. We do not know the gain of the Guralp. If we assume this missing 10 factor to be the gain of Guralp then we can get the same calibration as the old plot. But is it correct to do so?
I'm having this problem with DTV every morning at Rosalba only. It wants to start with a negative GPS time and it can not connect to the frame builder.
Normally after a few time of starting it, it will work.
Koji and I have finished shaking the table for the first round of measurements (horizontal shaking). We have cleaned up the lab space used.
The FFT Analyzer has been put back to its position at the back side of the rack (near the seismometers).
I will calibrate the photosensor for the suspension frame and piece together/analyze/produce graphs of the data today. If everything is fine (the measurements are fine) and if there is a chance, we hope to shake the TT suspension vertically.
We worked on the beam path from MC to BS this evening.
After the beam spots on MC1 and MC3 were close to the actuation nodes (<1mm away) we checked the beam position on the Faraday Isolator (FI) to make sure that it is passing through both the input and output apertures without clipping. The beam is slightly displaced (by about half a beam diameter) downwards at the input of the FI. The picture below is a screen shot from the MC1 monitor while Kiwamu held an IR card in front of the FI.
We then proceeded to check the beam position on various optical elements downstream. But first we levelled the BS table and checked to see if the reflection from PJ1 (1st Piezo) is landing on the MMT1 properly. It was and we did not make any adjustment to PJ1. However the reflection from MMT1 was not centered on MMT2. We adjusted the MMT1 to center the beam on it. We then adjusted MMT2 to center the beam on PJ2. At this point we noticed that the spot on IPPO (pick off window) was off towards the right edge. When we centered the beam on this it missed the center of the PRM. In order to decide what needs to be moved, we adjusted PJ2 such that the beam hits the PR2, bounces back to PR3, and becomes co-incident with the green beam from X-arm on the BS. Under this condition the beam is not in the center of PRM and nor is it centered on IPPO. In fact it is being clipped at the edge of the IPPO.
It is clear that both IPPO and the PRM need to be moved. To be sure that the beam is centered on PR2 we plan to open the ITMX chamber tomorrow.
[Jenne, with ample supervision by Kiwamu and Suresh]
Y-green was aligned, and is now flashing. The ETMY trans camera was very helpful for this alignment. I didn't end up needing to use a foil aperture.
Kiwamu and Suresh had just closed up the IOO doors, so we don't know yet where it's hitting on the PSL table (if the beam is making it that far). Tomorrow we'll look at ITMY to see if the green beam is centered there, and if it's coming out to the PSL table.
For some reason the workstation at the vac rack was off and unplugged. Nicole and I plugged its power back in to the EX rack.
I turned it on and it booted up fine; its not dead. To get it on to the network I just made the conversion from 131.215 to 192.168 that Joe had done on all the other computers several months ago.
Now it is showing the Vacuum overview screen correctly again and so Steve no longer has to monopolize one of the Martian laptops over there.
I ended up choosing a different dither frequency for driving the NPRO PZT: 230 kHz, because the phase modulation response in that region is higher according to other data taken on an NPRO laser (see this entry). At 230 there is a dip in the AM response of the PZT.
I am driving the PZT at 230 kHz and 13 dBm using a function generator. I am then monitoring the RF output of a PD that is detecting light reflected off the cavity. (The dither frequency was below the RF cutoff frequency of the PD, but it was appearing in the "DC output", so I am actually taking the "DC output" of the PD, which has my RF signal in it, blocking the real DC part of it with a DC block, and then mixing the signal with the 230kHz sine wave being sent to the PZT.
I am monitoring the mixer output on an oscilloscope, as well as the transmission through the cavity. I am sweeping the laser temperature using a lock in as a function generator sending out a sine wave at 0.2 V and 5 mHz. When there is a peak in the transmission, the error signal coming from the mixer passes through zero.
My next step is to find or build a low pass filter with a pole somewhere less than 100 kHz to cut out the unwanted higher frequency signal so that I have a demodulated error signal that I can use to lock the laser to the cavity.
Thanks to Koji's help, the second photosensor, which was not working, has been fixed. I have re-calibrated the photosensor after fixing a problem with the circuit. I have determined the new linear region to lie between 7.6 mm and 19.8mm. The slope defining the linear region is -0.26 V/mm (no longer the same as the first photosensor, which is -0.32 V/mm).
Here is the calibration plot.
ETMY is now in its new nominal position, according to the rails that Kiwamu put in the other day. OSEM voltages are all centered, and the magnets looked pretty well centered in the OSEM bores. We're taking data for some free swinging spectra, to check the decoupling.
Next up: Align Y-green to the arm, then move on to fixing the other optics that Jamie pointed out.
Below is the overview of all the core IFO suspension input diagonalizatidons.
I had originally put the condition number of the calculated input matrix (M) in the last column. However, after some discussion we decided that this is not in fact what we want to look at. The condition number of a matrix is unity if the matrix is completely diagonal. However, even our ideal input matrix is not diagonal, so the "best" condition number for the input matrix is unclear.
What instead we do know is that the matrix, B, that describes the difference between the calculated input matrix, M, and the ideal input matrix, M0: should be diagonal (identity, in fact):
M = M0 B
B should be diagonal (identity, in fact), and it's condition number should ideally be 1. So now we calculate B-1, since it can be calculated from the pre-inverted input matrix:
B-1 = M-1 * M0
From that we calculate cond(B) == cond(B-1).
cond(B) is our new measure of the "badness" of the OSEMS.
pit yaw pos side butt
UL -2.000 -2.000 -2.000 -0.345 2.097
UR -0.375 -0.227 -0.312 -0.060 0.247
LR 1.060 1.075 0.971 0.143 -0.984
LL -0.565 -0.698 -0.717 -0.141 0.672
SD 1.513 1.485 1.498 1.000 -1.590
pit yaw pos side butt
UL 0.791 1.060 1.114 -0.133 1.026
UR 1.022 -0.940 1.052 -0.061 -1.027
LR -0.978 -0.987 0.886 -0.031 0.903
LL -1.209 1.013 0.948 -0.103 -1.043
SD 0.286 0.105 1.249 1.000 0.030
pit yaw pos side butt
UL 1.420 0.818 -0.069 0.352 1.038
UR 0.276 -1.182 1.931 -0.217 -0.905
LR -1.724 -0.274 1.940 -0.254 0.862
LL -0.580 1.726 -0.060 0.315 -1.194
SD 0.560 0.171 -3.535 1.000 0.075
pit yaw pos side butt
UL 0.437 1.015 1.050 -0.065 0.714
UR 0.827 -0.985 1.129 -0.221 -0.957
LR -1.173 -1.205 0.950 -0.281 1.245
LL -1.563 0.795 0.871 -0.125 -1.084
SD -0.581 -0.851 2.573 1.000 -0.171
pit yaw pos side butt
UL 0.905 -0.884 -0.873 0.197 0.891
UR -1.095 1.088 1.127 -0.252 -1.115
LR -0.012 -0.028 0.002 0.001 0.030
LL 1.988 -2.000 -1.998 0.451 1.964
SD 4.542 -4.608 -4.621 1.000 4.517
pit yaw pos side butt
UL 0.344 0.475 1.601 0.314 1.043
UR 0.283 -1.525 1.786 -0.071 -1.181
LR -1.717 -1.569 0.399 -0.102 0.938
LL -1.656 0.431 0.214 0.283 -0.837
SD 0.995 -2.632 -0.999 1.000 -0.110
pit yaw pos side butt
UL -0.212 1.272 1.401 -0.127 0.941
UR 0.835 -0.728 1.534 -0.101 -1.054
LR -0.953 -1.183 0.599 -0.066 0.827
LL -2.000 0.817 0.466 -0.092 -1.177
SD -0.172 0.438 2.238 1.000 -0.008
I modified a set of the automated MC locking scripts which are dedicated for the low power MC.
Currently there are three scripts like the usual MC locking scripts:
(1)mcup_low_power, (2) mcdown_low_power and (3) autolockMCmain40_low_power.
I ran those scripts on op340m as usual and so far they are running very well. The lock acquisition is quite repeatable.
I hope theses scripts always bring the lock condition to the same one and hence the LOCKIN signals don't change by every lock.
- To run the script
log into op340m and run autolockMCmain40m_low_power
And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab. Requiring us to start over again.
ADC: 216counts = 4V Hence, calibration of ADC is 214counts/V.
Gain of the AA board, g1 = 0.1
214 counts/V x 800 V/ms-1 = 13107200 counts/ms-1 -----> 7.6294e-08 ms-1/count
Gain, g2 = 10
Calibration = 7.6294e-08 ms-1/count x g1 x g2 = 7.6294e-08 ms-1/count
214 counts/V x 1500 V/ms-1 = 24576000 counts/ms-1 -----> 4.069e-08 ms-1/count
Gain of the STS electronic breakout box, g3 = 10
Calibration = 4.069e-08 ms-1/count x g1 x g3 = 4.069e-08 ms-1/count
We got the results of the wiener filtering simulations (Elog Entry)
We got the power spectra and coherence of the seismic noise measurements from GURALPs and STS seismometers (Elog Entry)
We tried to whiten the target and the input signal for the computation of the wiener filter for the real data, but the results are unsatisfactory. We should not care about high frequencies in wiener filter computation so we will just filter them off in the filter output with a low pass filter.
We just found the right gain for the system seismometer-AAboard-ADC (Elog Entry)
Last night, I attached a metal plate to the Vout faceplate of my photosensor circuit box because the BNC connection terminals were loose. This was Jamie's suggestion to establish a more secure connection (I had originally drilled holes for the BNCs that were much too large).
I have also fixed the mechancial set-up of my shaking experiment so that the horizontal sliding platform does not interfere with the photodiode mounting stage. Koji pointed out last night that in the full range of motion, the photodiode mounting stage interferes with the movement of the sliding platform when the platform is at its full range.
I have began shaking. I am getting a problem, as my voltage outputs are just appearing a high-frequency noise.
We used a function generator, an oscilloscope and the Data Viewer to check the gain of the new AA board (used for the seismometers). Putting a sine wave of 0.3V (using a function generator) to the AA board, we could see about 500 counts in the Data Viewer. The calibration of the ADC is 214 counts/volt, so the AA board gives to the ADC an output of 0.03V. This proves that the AA board has a gain of 0.1. Guralp1 and STS1 (Bacardi), both have a gain of 10 now, that balance the AAboard gain of 0.1. If we consider the gain of AA board in our calibrated power spectrum plot of seismic signals from Guralp1 and STS1 (Bacardi), we get the following plot:
We attempted to minimise the A2L coupling in the MC mirrors (centering the beam spot on the actuation node on each optic). While it was easy to minimise the coupling in the pitch for all the three optics and yaw of MC2, the yaw alignment of MC1 and MC3 proved to be difficult. For one the adjustment required was quite large, so much so that PSL alignment into the MC is often lost during this adujstment. We had to align the PSL coupling several times in order to proceed. And the MC settles into a new position when the MC-PSL servo loop was disturbed by random denizens in the lab. Requiring us to start over again.
Kiwamu wrote a script to measure the MC(optic)(Pitch/yaw) -> Lockin(#1 to #6) matrix. Inverting this matrix gave us the linear combination of the offsets to put on the MC# PIT/YAW inorder to minimise a specific Lockin output. However the cross couplings were not completely eliminated. This made it very hard to predict what a given set of offsets were going to do to the Lockin outputs.
Net result: the spots are centered in vertical direction (pitch) but not in the horizontal (yaw)
Day time tasks have started so I am quitting now.
Suresh and I tweaked the OSEM angles in ETMX yesterday. Last night the ETMs were left free swinging, and today I ran Rana's peakFit scripts on ETMX to check the input diagnolization:
It's well inverted, but the matrix elements are not great:
pit yaw pos side butt
UL 0.3466 0.4685 1.6092 0.3107 1.0428
UR 0.2630 -1.5315 1.7894 -0.0706 -1.1859
LR -1.7370 -1.5681 0.3908 -0.0964 0.9392
LL -1.6534 0.4319 0.2106 0.2849 -0.8320
SD 1.0834 -2.6676 -0.9920 1.0000 -0.1101
The magnets are all pretty well centered in the OSEMS, and we worked at rotating the OSEMS such that the bounce mode was minimized.
Rana and Koji are working on ETMY now. Maybe they'll come up with a better procedure.
I've finished using the network analyzer to characterize find a dither frequency for driving the PZT to use in my PDH locking. I found a region in which the amplitude response of the PZT is low: The dip is centered at 2.418 MHz. Changing the NPRO laser temperature by 100mK has no significant effect on the transfer function in that region. I will post plots tomorrow.
I'm finished with the network analyzer. It is unplugged, and the cart is still near the PSL table. (I'll roll it back tomorrow when it won't disturb interferometer locking).
I closed the shutter on the NPRO at the end of the night.
Tomorrow I plan to put together the fast locking setup. I'll drive the PZT at 2.418 MHz. More details to come tomorrow.
- Jenne will make a better kick/free-swing test later.
02:27am, ran the new freeswinging-ifo.csh script. It's just a copy of freeswinging-all.csh, but it doesn't include the MC mirrors, since Suresh and Kiwamu are still working.
Now we have copies of the script for -all, -mc, -ifo to cover the various sections of the suspended interferometer.
[Rana Koji Jenne Jamie]
- The situation of the ETMY suspension is improved.
- The damping servos except for Pitch are now functional.
- We intentionally turned off the damping servos for the matrix measurements.
- Opened the light door of the ETMY chamber.
- We set up the CDS SUS lockin:
Excite UL/UR/LL/LR equally [by setting the output matrix (1, 1, 1, 1, 0)] at 3.12Hz with 2000 cnts
Put the OSEM PD outputs into lockin one by one. For the image rejection, 0.1Hz 4th order LPF has been used though we like to use a faster settling LPF.
- Found only UL was responding to the excitation. After fitzing with the cables and connectors, it was found that the DAC card was loose from the bus.
By pushing the card the responses have been back. [Note we had the reboot of c1iscey almost at the same time.]
- Checked the response in the I channel of the lockin.
UL -8ish / UR +7ish / LR +5ish / LL +2ish
- Tweaked LL sensor to get better response ==> in vain. Decided to move the lower OSEM plate for the better positioning of the LR/LL.
- Got reasonable (+5ish) response for LL.
- Confirmed that the POS/YAW/SIDE damping works with positive gains. PITCH did not work with the negative gain (but that could be a good sign.)
- Let the suspension freely swinging for a while (~30min). Checked the side/pos separation. They are not perfect but seemed diagonalizable.
- Closed the light door.
I updated the peakFit routines to make them a bit more user friendly:
These changes were committed to the 40m svn.
This week, I have finished assembling everything I need to begin shaking. I built an intermediary mounting stage to mount the TT suspension base to the horizontal sliding platform, finished assembling the second photodiode, finished assembling the photosensor circuit box, and calibrated the two photosensors. Today I built a platform/stage to mount the photodiodes so that they are located close enough to the mirror/suspension that they can operate in the linear range. Below is an image of the set-up.
The amplifer that Koji fixed is acting a bit strange again...It is sometimes shutting off (Apparently, it can only manage to do short runs ~ 1minute? That should be enough time?).
The set-up is ready to begin taking measurements.
Jenne found a big scratch on the north vac door of ITMY. Fortunately it does not reach the inner annulos 0 -ring seal.
This is precisely what we have to avoid to preserve our vacuum system!
I measured the particles coming off of new- unused clean room coat. Tyvek, Convertors, Allegiance #9393 measured 10 counts of 0.3 micron at 1 minute and 0 count at 7 minute.
The 0.5 micron size measured 0 at both times. Jenne's used coat measured 20 counts of 0.3 micron and 0 counts for 0.5 micron at 1 minute. ( counts / cf- min)
The HEPA tent background is consistently 0 when it's CP STAT 100 curtains are closed.
We did the simulation of the stacks by defining a transfer function for one stack (green plot) and another similar transfer function for the other stack.
We simulated the ground motion by filtering a white noise with a low pass filter with a cutoff frequency at 10Hz. (blue plot) (the ground motion for the 2 stacks are completely uncorrelated)
We simulated the electronic white noise for the seismic measurements. (black plot)
We filtered the ground motion (without the measurements electronic noise) with the stack's transfer function and subtracted them to find the mirror response (red plot), which is the target signal for the wiener filter.
We computed the static wiener filter with the target signal (distance between the mirrors) and the input data (seismic measurements = ground motion + electronic noise).
We filtered the input and plotted the output (light blue plot).
We subtracted the target and the output to find the residual (magenta plot).
We didn't figure out why the residual is above the electronic noise only under ~6hz. We tried to increase and decrease the electronic noise and the residual follows the noise still only under ~6Hz.
It also shows that the residues are above the target at frequencies over 20Hz. This means that we are injecting noise here.
We tried to whiten the target and the input (using an high pass filter) to make the wiener filter to care even of higher frequencies.
The residues are more omogeneously following the target.
We also plotted the Wiener filter transfer function without making whitening and with making whitening. It shows that if we do whitening we inject no noise at high frequency. But we loose efficency at low frequencies.
We shouldn't care about high frequency, because the seismometers response is not good over 50Hz. So, instead of whitening, we should simply apply a low pass filter to the filter output to do not inject noise and keep a good reduction at low frequencies.
The top plot shows a sweep from 10 kHz to 5 MHz of the ratio of the voltage output of the PD detecting power from the NPRO laser beam and the RF source voltage (the magnitude of the complex transfer function). The black trace was taken with the laser beam blocked. For runs 2 and 3 I changed the laser temperature set point by 10 mK and 100 mK respectively to see if there was a significant change in the AM response. The bottom plots shows runs 2 and 3 compared to run 1 plotted in dB (to be explicit, i'm plotting 10 times the base 10 log of the magnitude of the ratio of two complex transfer functions). Changing the temperature seems to have only a minor effect on the output except at around 450kHz, where the response has a large peak in run 1 and much smaller peaks in runs 2 and 3.
The traces in the top plot consist of 16 averages taken with a 300Hz IF bandwidth, 15 dBm source power (attenuated with a 6 dB attenuator) and with 20dB attenuation of the input power from the PD.
Next I'm going to probe a narrow band region where the response is low (2.0MHz or 2.4MHz perhaps) and choose a bandwidth for the dither frequency for the PDH locking.