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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long term pk-pk measurement of the accelerometer (placed on the optical cavity table, on the marble part close to the laser oscillator) from 5:30pm to
9am => ~ 2.255s / pt
start of the quiet period : ~ 5k pts <=> 8:45pm |
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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 the accelerometer on the ground close to one feet of the FP cavity hexapod (see picture) and restarted the acquisition at 6:40pm on 20th
of february.
the acquisition corresponds to the night between the 20th and the 21th of february. |
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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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for this 20Hz oscillation, could it be a natural resonance of the optical table placed on its feet ?
typical mass of the table m ~ 8T
feets : |
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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, the cavity was pretty misaligned => basic alignment in y direction helps a lot => 93kW for 33% amp ratio.
the Rigol 33MHz generator phase was adjusted : phase ch2 = phase ch1 (40 deg) + 36 deg = 76 deg.
Ronic |
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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, the alignment of FP cavity was so bad that I tuned the 01 mode by error (CEP and alignment)... insead of the 00 mode !!!
I was able to reach ~30kW and was limited at this value, so I used the camera to check what was happening and saw the 01 mode.
so, I moved the lock on a 00 mode and redid a full tuning (CEP and alignment). |
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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, after 1 week of vacation, I was able to easily lock the cavity with 92kW with 33% amp ratio without too much optimizations (no walking alignment).
could it be related to the nice weather we got during this week ?
as in the past we observed more noise when the weather was changing and we had very difficult locking procedure after a simple weekend... |
air conditionning in ThomX Bunker, posted by Ronic Chiche at ThomX igloo about lasers and optics
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The temperature slitly increase in thomx Bunker from 23° to 24° during the last day.
The thermalisation of the CFP is very long...
In any case the operation of the CFP is so easy, it seems to be correlated to the weather... tody it's very nice as of hte rest of the week. |
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air conditionning in ThomX Bunker, posted by Ronic Chiche at ThomX igloo about lasers and optics
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after the new temperature setting for the bunker air cooling (winter to summer transition), the temperature drop from 24° to 20°C which induced
a slight misalignment between the onefive oscillator and the fiber injection.
the amplifier photodiode PD_IN which checks the amplifier power injection drop also from 3mW to 2.885mW... hopefully, it is enough to start the |
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air conditionning in ThomX Bunker, posted by Ronic Chiche at ThomX igloo about lasers and optics
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I finally got 93-94kW for 33% amp ratio.
I had to move the FP-cavity length to compensate the temperature change in the bunker.
doing that, I had the message "Low Limit SW pressed" when I tried to move P4z under -98 000 steps !!! |
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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, I removed the NKT oscillator from the bunker to put it in the PLIC room.
I locked the FP cavity and obtained 97kW with 33% amplifier ratio, without any alignment, just by changing a little bit the CEP.
Ronic |
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Possible causes for the noise in the FP-cavity system, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics
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list of possible causes of the high frequency noise which makes the system loosing the lock => to be checked.
(if you have some new idea, I will edit the post)
1- Laser |
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Possible causes for the noise in the FP-cavity system, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics
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4.3 - Vibrations of the mirror mounts due to temperature related to cavity power (the electrons machine is OFF)
1) to test this possible issue, we plan to make a run at low power in the FP-cavity, around 10kW, instead of ~90kW as usual.
for that, I will need to change the diffuser position on axis 18 to get the same error signal for the locking. |
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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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New locking parameters (I got 98kW for 33% amp ratio) :
Axis 18 position : +0009420
P = 0.05 |
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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 had a long run without any lock loss during ~1h with the 23kW recipie in the morning.
during the afternoon, we had some few lock losses but the FPC system was globally quiet and stable,
but at the end of the day, I observed more and more frequent high frequency noise which implies lock losses. |
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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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long run yesterday at relatively low power (~23kW) with double loop (FPC + RF) between 10am and 6pm
Ronic
Chiche wrote:
We had a long run without any lock loss during ~1h with the 23kW recipie |
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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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long run today at relatively nominal power (~90kW) with double loop (FPC + RF) between 13:30am and 6:30pm
Ronic
Chiche wrote:
long run yesterday at relatively low power (~23kW) with double loop |
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Stability test Without and with , posted by Ronic Chiche at ThomX igloo about lasers and optics
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The laser starts at 93 KW.
This morning I operated the laser locked with the RF for 1h30 without any delock. All the machine was switch off.
All the system was very stable. Sometimes the 20 Hz perturbation was visible but no delocking. |
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Suite tests stabilité, posted by Ronic Chiche at ThomX igloo about lasers and optics
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We continue to find what gives high freq. perturbation.
The laser starts at 92 KW it is stable and locked to the RF. NO high freq parturbation.... With the machine off. (30 min of lock)
We put now the machine ON (All in warming exept pulsed elements)... => the system is very stable NO delock, NO high freq perturbations. The |
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Xrays experiment with prostate, posted by Ronic Chiche at ThomX igloo about lasers and optics
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Today we do XRays for experiment.
The laser start to 33% at 93 KW but Pgain = 0.033
The laser is locked so stable for the moment. We have Xrays and the system is stable. |
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laser operation again with machine OFF, posted by Ronic Chiche at ThomX igloo about lasers and optics
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The laser start at 33% with 92 KW optimized and
P=0.03
I=0.0005 |