LMA cleaning technique, posted by Loïc Amoudry at Optical room about lasers and optics
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Christophe MICHEL told us more precise informations about spin coater cleaning.
They always clean with pur water and cotton tipped sticks.
First a spray of water, then they put the wet cotton tipped sitck onto the mirror from the center to the edge ~x3 while continuing to spread |
Injection of 33MHz Onefive through fiber, posted by Loïc Amoudry at Optical room about lasers and optics 
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Output power of the Onefive, and power after injection and different components have been measured.
Coupling ~= 90%
Each of our two EOM roughly have the same loses ~3dB |
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Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics 8x
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Last Friday, we tried to increase the FP-cavity power by just increasing the amplifier ratio from 35% to 70%.
It took a bit longer than expected because it started with the surprise of finding our entire setup powered off…
The power had tripped, and the switch that allowed us to remotely reset the power supplies had been damaged. |
Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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today with Alice and Daniele,
we checked the distance of the optical setup :
from the amplifier output (the fiber output) to the 2nd lens (+200 mm) : |
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Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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new power increase after alignment of the waveplates and iris.
amplifier ratio (%) => FPC cavity power (kW) => FPC cavity coupling (%) => Vr unlock (mV)
33 => 98 => |
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Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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I installed a stronger optical filter on the reflection photodiode and loaded it on 1kOhms.
70% amplifier ratio => 575 mV => 575 µA => no more photodiode linearity issue
amplifier ratio (%) => Vr unlocked (mV) |
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Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning with Daniele, we set the amplifier ratio to 33% => 97kW
then, we set the amplifier ratio to 50% => 124 kW (position of the diffuser on Axis 18 : +11775)
we changed the waveplates axis => no effect |
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Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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Last friday, with Daniele, we did some realignement on the 2nd CVBG of the compressor : the beam shape seems better, now.
this morning, we checked that the injection path (periscope and injecton mirrors) is not sensitive to the polarization state of the beam.
we checked also the power at the input of the FPC for 70% amplifier ratio : 40W ! |
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Incoming laser beam power issue, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, we observed on the photodiode used in reflexion of the cavity, that its voltage level stops increasing after 50% of power for the laser amplifier
when the cavity is not locked (the FP-cavity is just a reflective mirror).
the photodiode itself is not saturated (low power sent after a wedge and an absorbing filter) and the reading is done on 50 ohms. |
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Improvement holder amplifier fiber, posted by Loïc Amoudry at Optical room about lasers and optics
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| We've added a clamp in the 3rd stage to prevent the pump fiber from moving and tilting (it was tilting to the left). |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Today, the lock of the FPC was particularly bad (maybe the worst ever seen), with a lot of high frequency noise.
the lock was impossible during several minutes !
we tried to switch off all the equipments of the machine, one by one without any effect on the lock. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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At the end of the day, we found out what was the origin of this noise : some road renovation work with jackhammer and road roller just at the entrance
of the "Igloo".
this origin was 100% correlated with a large increase of the accelerometer signal. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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After this observation, we did a test with Daniele to try to correlate the road traffic in front of the Igloo with the lock losses observed on the FPC.
We didn't see any clear correlation. Cars or buses are not the direct origin of the FPC lock losses... only when some heavy load is hitting
the building, we observed a clear correlation. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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we did some tests with Marie to make some vibrations on the door.
below, I exhibit some pictures of the scope with the accelerometer plugged on it without or with noise...
this level of noise is not able to make the FPC loosing the lock. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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This morning, I installed a high-voltage probe (1:1000) on the AC-line to see if one could detect a correlation between lock losses and AC-line voltage
variations.
I observed many lock losses but without any variation or correlation of the AC-line signal (scope set in "peak detect" with "envelope" |
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Good Xrays production trend, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics | software
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| this afternoon, we succeeded to get a quite long Xray production trend around 15-20 minutes with a flux above 25k on i1. |
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Free Spectral Range (FSR), posted by Loïc Amoudry at Optical room about lasers and optics
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FSR is 33.347 MHz @1e-8 mbar
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First stable X-rays production, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, we locked the laser on the FP-cavity with about 48-49kW stable in the FP-cavity (for 32% of amplifier ratio).
and then we locked the FP-cavity on the RF reference (500MHz beating lock + 33MHz beating for starting lock search).
the starting lock search voltage has been chosen between -20mV and +20mV. |
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First mode degeneracy on ThomX, posted by Loïc Amoudry at Optical room about lasers and optics
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Yesterday, we've observed the first degeneracy on ThomX cavity at ~115 kW stored. The shape of the stored power on the oscilloscope is really close
to what has been published in the D-shape mirror's paper ("tek0000" transmission in yellow, piezoelectric activator in green, error
signal in blue). |
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First hands on the Alphanov amplifier & software, posted by Ronic Chiche at ThomX igloo about lasers and optics
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Aurélien, Manar, and I spent more than 2h trying to start the software communicating with the Alphanov amplifier controller.
each time, we had a problem with the software, asking to switch OFF and ON the controller before being able to switch the amplifier diodes ON.
we switched OFF and ON many times without any success. |