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). |
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. |
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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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 we did x-rays => we got 41 000 pA at maximum and 90kW in the FPC for 33% amplifier ratio.
finally, I changed the strategy for the feeback on RF.
i removed the integration and derivative parameters and reduced the gain parameter : |
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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 lock of the CFP after almost 2 weeks without operation.
after quick alignment and CEP tuning, I got 88kW for 33% ratio for the laser amplifier.
the FPC seems pretty far from the RF frequency (2.8kHz @ 33MHz) but it's possible the present RF frequency has been tuned for 61.5 or 70MeV |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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I installed an accelerometer setup in the bunker.
presently, the accelerometer is placed on top of the housing and its signal is connected to the 2nd scope (33MHz and 500MHz RF beating) on channel
4. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today I connected a copy of the laser PZT signal to the 2nd scope CH2 (with AC coupling to remove the DC offset) to be able to monitor synchronously
the Accelerometer and laser PZT signals.
the accelerometer is still connected to the 2nd scope CH4 and placed on top of the housing. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, I did some measurement with nobody interfering with the tests.
- the "no noise" image shows a standard situation during 10s when there is no noise either on PZT or Accelerometer.
most of the time, we are in this situation. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 8x
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then, I moved the accelerometer on top of the "X-hutch side" vessel, placed directly on the metal top case, inside the housing.
- the "no noise same range" image shows a standard situation during 10s when there no noise either on PZT or Accelerometer.
on can compare the noise level on the accelerometer with the previous post when it was outside on top of the housing. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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at the end of the day, I moved the accelerometer from the top of the cavity vessel to the top case of the Onefive laser.
I quickly saw again quite strong correlations between the vibrations compensated by the PZT and the accelerometer signal.
when one does a laser motor step which makes a systematic lock loss, one doesn't see any signal on the accelerometer. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 6x
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this morning, I did some new plots with the accelerometer placed on the top of the case of the OneFive laser.
I previously observed with the accelerometer placed on the top of one cavity vessel, the correlation between the accelerometer signal and the PZT
noise is pretty good but not 100%. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 7x
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new plots, with the accelerometer placed directly on the optical cavity table (on the marble part), close to the oscillator.
the correlation seems a bit better....
we would need to put the accelerometer on one foot of the table to check if the table has not some micro-movement or at the IP to check if the |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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one possible source for this acoustic noise was the vibrations coming from the water cooling of the dipoles which is normally never turned off even when
the machine is off.
this afternoon, Kevin turned off the main valve of the water cooling of half of the dipoles (the half on the FPC side), and we recorded the peak-peak |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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here is the pk-pk measurement of the accelerometer during the whole night.
the recording started at 5pm yesterday and has been stopped this morning at 10am.
one got 28k points in 17 hours => 1.65k points / h |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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here is the acquisition from 10:30am to 5:30pm
11k point in 7h => 1.57k points / h
the noise is almost the same during the daylight, a little bit increasing from 1:30pm. |
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correlations between accelerometer and lock losses @ 20Hz, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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here is the same kind of measurement (pk-pk of 1 sec of acquisition) done on the laser PZT when the FP is at 90kW.
it's from 6:20pm to 7:10pm => ~2.4s by point
the minimum values are for the PZT being off. |