controller M1 & M4 (plan mirrors) with IcePap controllers, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | cabling
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at the begining of each session, it will be mandatory to avoid any backlash for the motors :
- for the P4 motor : one can go 2k steps DOWN, then 2k steps UP to go back to -360 000 and use the
steps UP without any backlash |
Basic alignment & alignment motors check, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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14/02/19: The 4 motors but Mby control works. Mby motor home does not bring it to its "middle" position but to the end of its range.
Issue circumvented using the higher rights software.
The beam is now going through the cavity windows (from P1 to S2). |
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Alignment procedure, posted by Ronic Chiche at Optical room about mechanics | lasers and optics
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we did again the complete alignment procedure starting with iris and optimizing injection motors Ma and Mb, then installing mirror S2, S3, P4 and P1,
optimizing thetaX and thetaY axis for each motor.
everything was fine until we installed P1. we tried to optimize thetaX and thetaY of P1 and we clearly observed a strange motion when doing that |
Amplifier mission Bordeaux, posted by Loïc Amoudry at Other about mechanics | lasers and optics 
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Voyage Bordeaux au CELIA avec Jérôme LHERMITE (Loïc et Titoutan)
1er jour (34°) :
Mesure du spectre et de la puissance des 4 diodes de pompe 3ème étage jusqu’à ~60W (12A). |
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Amplifier mission Bordeaux, posted by Loïc Amoudry at Other about mechanics | lasers and optics
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M² mesuré à 10W.
M²x = 1.17
M²y = 1.14 |
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Spin coater air supply removed and front panel changed, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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Spin coater firstly needed vacuum and air supply. The air supply being useless for our experiments, it has been disabled.
The process is the following and is reversible:
1) Remove the hub from the top of the spin coater, (see picture 1), 4 screws |
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Cavity dust source check, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics
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Several experiments have been done in order to check the potential source of dust in the ThomX cavity. For each step, we look at a clean surface, put
the cavity under vacuum, go back at ambient pressure and check back the "clean surface".
1st: Primary pump on |
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Alignment procedure, posted by Ronic Chiche at Optical room about mechanics | lasers and optics
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Picture of the installed mirrors inside the FP cavity.
To install an Iris instead of a mirror :
One has to remove manually the orange nuts and replace the mirror mount with the Iris mount. |
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!!! strange amplifier beam pointing fluctuations !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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this morning, I locked the cavity to ~25kW without any problem.
but this afternoon, the reflected power exhibited low frequency (~1Hz) fluctuations of about 10% without any lock.
the reflected PhD is a DET10 which has a small surface. |
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!!! strange amplifier beam pointing fluctuations !!!, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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we confirmed the effect of the bunker temperature on the laser amplifier "beam pointing" fluctuations.
once the temperature is getting back to stable values, it doesn't happend again.
we bought a temperature data logguer to monitor them in the future: https://www.picotech.com/data-logger/tc-08/thermocouple-data-logger |
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M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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Kevin moved the M4 mirror controller from the ISP controller to some ICEPAP controller.
the IHM to access this ICEPAP controller is accessible by launching 'jive' from any account ('operateur.thomx' for example).
once in the jive window, one has to select the 'device' tab, then select the OC=>OP=>OCH.02-MOT.03 device. |
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M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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one problem is the FP-cavity/laser lock loss when one moves a FP-cavity motor.
with acceleration = 0.01 units/s² and velocity = 50mm/s (here, the 'mm' unit seems strange as it is very fast), it's enough
to make a move fast enough for small displacements (10 steps for example to center PZT position) and it seems that the cavity stays locked (only the FP-cavity/laser |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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laser cavity :
when one decreases the laser motor position, the laser repetition rate increases (laser cavity length decreases).
=> +/- laser motor step => +/- laser cavity roundtrip length => -/+ |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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Now, I placed a temperature probe stuck on the laser housing itself.
fig. 1
one can compare the temperature measured at the surface of the laser housing and the beating frequency with the 500MHz reference oscillator |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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the last thing we did with Daniele, is to start/stop the airflow on top of the housing (closed) to see a possible pressure effect on the laser frequency
drift.
fig 1 : in green, the temperature measured with the probe stuck on the laser housing. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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today, I swapped the 500MHz RF reference oscillator for a Siglent 500MHz DDS oscillator.
see the attached plot : the beating frequency with the 500MHz laser harmonics produces the same behavior as before.
so, the oscillations should come from the laser temperature regulation. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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long-term correlation, over 5-6 days, between the temperature measured in the bunker, outside of the housing (blue curve) and the temperature measured
with a probe stuck on the laser housing, inside of the FP-cavity housing (green).
it's a perfect correlation with almost the same temperature scale : 1°C outisde the housing => 1°C of laser housing |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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this morning, I did a 500MHz beating frequency (Laser vs RF) drift test with the Smaract motors configured with "Sensor Mode" OFF over 50 minutes
(~ 1500 acquisitions)
compared with previous measurements, one observes a much more smooth "exponential-like" drift compared to "Sensor Mode" ON |
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Laser and FP cavities frequency adjustment, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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at the beginning of the procedure, the frequency gap between the new Ring 33MHz frequency (33.3378MHz) and the laser/FP cavities frequency was 12.33kHz
=> the Smaract motor position was at +100µm
=> the FP cavity motor Mot.03 position was at -358 720 steps |
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Laser and FP cavities frequency adjustment, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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This afternoon, I did the 2nd half of the travel: dF @ 33MHz = 0Hz
=> the Smaract motor position is now at +1750µm
=> the FP cavity motor Mot.03 position stayed at -200 000 steps |