Optimizing lock parameters for stable X-ray production, posted by Ronic Chiche at ThomX igloo about lasers and optics | software
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Today, after setting the locking parameters, I got 80kW in the FPC for 33% amplifier ratio after CEP tuning (Smaract CH2 ~ -423.5µm) and alignment.
maybe the alignment has to be improved by some walking procedure.
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Optimizing lock parameters for stable X-ray production, posted by Ronic Chiche at ThomX igloo about lasers and optics | software
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this morning, I did some walking procedure and I got 82kW in the FPC with 33% amplifier ratio (after CEP optimization too).
but when I move the FP cavity motors to adjust the frequency, I cannot keep this power and it is reduced.
could it be we get a stronger correlation between axis than before in the mechanics has more rust than before ? |
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Optimizing lock parameters for stable X-ray production, posted by Ronic Chiche at ThomX igloo about lasers and optics | software
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this morning, I did some walking procedure and CEP alignment to get ~80kW in the FPC with 33% amplifier ratio.
we have to check if this power drop comes from:
- a laser amplifier power drop |
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Optimizing lock parameters for stable X-ray production, posted by Ronic Chiche at ThomX igloo about lasers and optics | software
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the RF frequency is now 500.1003MHz which is equivalent (if divided by 15) to 33.34002MHz.
the frequency has to be changed by ~2kHz @33MHz <=> ~550µm /2 for one motor.
I changed the laser and the FP cavities frequency. |
Checking the amplifier power, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this morning, with Daniele, we checked the amplifier power, right after the CVBG (the power meter has to be placed on a metal plate above the large table
hole), and just at the input of the FP cavity, after the 1/4 and 1/2 waveplates (the power meter has to be placed on flat beam dump+ Thorlabs beam dump
+ V metallic mount to be at the right height). |
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Checking the amplifier power, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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we did a long term run (25 mn) with the powermeter located at the FPC position at 33% amplifier ratio.
the initial power was 18W .
then, it goes to 18.5W in 10 minutes, then 5 minutes later, it goes to 18.3W and stay stable until the end the run. |
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Checking the amplifier power, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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I put back and aligned the 1/2 waveplate only and I get 71kW max after its optimization and optimizing the CEP and alignment (without walking procedure).
this waveplate change a lot the reflected power seen on the CH2 of the scope.
to be continued this afternoon... |
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Checking the amplifier power, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this afternoon, we put back the 1/4 and 1/2 waveplates and after a long alignment/angle tuning/CEP optimization process, we hardly got 80-81kW in the
cavity for 33% amplifier ratio. the transmission photodiode is then ~ 7.5 divisions (500mV/division) on the scope.
BUT during the 1/2 and 1/4 waveplate angle tuning process, we clearly saw: |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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the RF frequency changed from 500.1003MHz to 500.0913MHz => it reduced by 9kHz @ 500MHz which is equivalent to 600Hz @ 33MHz (we measured 500Hz @
33MHz). the electron orbit length increased, so we have to increase the cavities length => increase motor values by ~ 68µm.
for the laser cavity : 1.496 560 mm => 1.564 560 mm |
day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 
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at the begining of the day, we started to get ~81kW in the FPC for 33% amplifier ratio and after ~1h, we got 84kW after CEP and alignment tuning.
at the end of the day, we got 89kW without walking alignment.
we tried to improve a bit the robustness of the FPC and RF locks: |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today with Alice, we planned to do a long run with ~80kW in the FPC to check if the lock problems are coming from the interaction with the machine or
not.
the goal is to check this assumption on a full day comparable with a day of X-ray production. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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we observed that :
- the MOT.03 motor always exhibits some perturbations on the transmitted, reflected and PZT signals (see "peaks" in the picture) in
contrary to the MOT.06 motor. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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last thing we tried :
we removed the threshold on the FPC/RF error signal.
=> we cannot choose automatically the RF bucket anymore (we need to manually let the phase drift slowly and start the lock at the right moment). |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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This morning, I added an amplifier on the 33MHz beating signal in between the mixer+LPF and the scope/Laselock.
it seems to improve the robustness of the RF/FPC lock.
because of this gain, I increased the upper and lower thresholds on the search criterion of the RF/FPC lock from +/-50mV to +250mV/-200mV |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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major result of the day: X-ray vertical scan by moving the hexapod
abscise : hexapod position
ordinate : xray flux in asynchronous condition |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, Kevin reduced the steering current in the IcePap controllers of the FP cavity motors.
the motor MOT.06 was producing a pattern in the Transmission signal when it was moved and doing a lock loss very often.
so, we changed its current from 0.8A to 0.4A and it fixes the problem => no more systematic lock loss. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, I restarted the cavity after the Christmas shutdown.
everything went fine.
I got ~ 86kW for 33% laser amplifier ratio after optimization of the CEP and alignment with walking procedure. |
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CEM noise measurements, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | cabling
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The goal of these measurements is to check if one can find some correlation between the CFP lock losses observed during a run and some CEM noise in the
bunker.
the main issue is coming from a 20Hz noise apearing/disapearing in the laser cavity PZT signal. |
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CEM noise measurements, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | cabling
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This afternoon, we started almost all the parts of the machine with Vincent and Nicolas, and we didn't see any change in the Loop noise signal.
we saw only a peak comb at 10Hz on the Loop noise signal when the septum is ON. the amplitude of the peaks is then related to the voltage on the
septum. |
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correlations between vacuum gauges and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum
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the machine people saw a correlation between BPM jumps and vacuum gauges peaks related to breakdowns in the beam pipe.
these breakdowns could produce some accoustic noise which could be related to our lock losses.
=> we tried to do a corrrelation between our lock losses and the vacuum gauge peaks => WE DON'T SEE any correlation !!! |