Etuvage cavité THOMX, posted by Ronic Chiche at Optical room about vacuum
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Mail de Bruno Mercier du 19/11/2018 :
Une première cavité a été étuvée, la pression est actuellement de
3.10-10 mbar, l' étuvage
de la deuxième cavité vient de commencer et se
finira en début de la semaine prochaine.
Bonne journée,
Bruno
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End of vacuum test and cavity ready for cleaning, posted by Loïc Amoudry at Optical room about vacuum 
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Vacuum tests finished on 19 december 2018.
Spent last two days to discuss the importance of removing aluminium and baking wires before to insert mirrors for cleanliness issues. Finally
we took pictures to support our demand. |
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Cleaning outside IP cavity, posted by Loïc Amoudry at Optical room about lasers and optics | utilities
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From 7th january to 11th january.
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End of cleaning, plastic fixed on cavity, posted by Loïc Amoudry at Optical room about utilities
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| 08/02/19 - End of the cleaning process. |
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Mirrors checked with binocular microscope, posted by Loïc Amoudry at Optical room about lasers and optics
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29/01/19 - ThomX mirrors have also been checked with binocular microscope. They shown the same spots as S-BOX mirrors.
1st image shows reflective face of a spherical mirror.
2nd image shows reflective face of M1 (sapphire). |
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Mirrors sent to LMA, posted by Loïc Amoudry at Other about lasers and optics
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30/01/19 - As LMA people came, we discussed about the spots on ThomX mirrors which should be clean. As mentionned in "SBOX commissioning",
these spots are normal.
An other question appeared during the conversation about the storage time and location of these mirrors. They have been stored for more than |
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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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Motors connexions, posted by Loïc Amoudry at Optical room about mechanics
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Motors are connected. The true mirror's name are P1 for injection mirrors, S2, S3 and P4. (S=spherical, P=planar).
They are still some old schemes (and notations on the cavity) which mention M1, M2, M3 and M4. I make the link here:
M3 = P1 |
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Beam size and finesse, posted by Loïc Amoudry at Optical room about lasers and optics
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FSR initiale : 33.34 MHz (S3 = -825000 et S4 = -825000)
Beam size initiale : wx=2.05mm et wy=2.15mm
Finesse initiale : 3400 |
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Motors Z axis reversed, posted by Loïc Amoudry at Optical room about mechanics
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S2 and S3 z-axis are initially at 1/4 (5mm/20mm) of there range over ~20mm range. This is meant to be able to spread them up to ~15mm in case of
thermal effect.
Actually, they are in an opposite position. Means that they can only be spread of 5mm from the initial position. |
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Cavity at atm pressure, posted by Loïc Amoudry at Optical room about lasers and optics | vacuum
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Dry air injected into the cavity.
Lock has been proceeded without any trouble. ~~4000 finesse. Considered to be the same than before.
x and y motors axis put back to the last "cavity at air" position. z position kept at maximum distance between spherical mirrors. |
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Check of mirrors and coating directions, posted by Loïc Amoudry at Optical room about lasers and optics
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Direction of HR face of P1 and P4 have been checked, there was no problem. The mirrors are in the good direction and the coating is on the good face.
Once P1 and P4 outside of the cavity, we checked the coating position by sending the HeNe laser with an angle. There was two reflections and
the most intense was the one closer to the normal to the mirror. |
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Wires in laser path, posted by Loïc Amoudry at Optical room about mechanics | lasers and optics | cabling
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| There was some ceramic wires close to the beem path right before P4. We moved them away (we can imagine they could move again with vibration). |
Motors Z axis reversed, posted by Loïc Amoudry at Optical room about mechanics
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All Z motors (for P1, S2, S3 and P4) have been initialized again with a proper HOME command with their own controller with the "superviser"
software (which means they all moved to the +1650000 position).
Thus, they have been moved to their default position : +825000 for spherical mirrors (S2 and S3) and -825000 for plan mirrors (P1 and P4). |
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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 |
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Finesse after removing wires, posted by Loïc Amoudry at Optical room about lasers and optics
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19/04/01: We removed the wires from the beam path in the cavity. Finesse stayed at 3400. FSR: 33.342 MHz.
When locked:
Input Power: ~4mW |
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Transmission of the mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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We openned the cavity, removed S2 and measured trans of P1 and same for S2.
Pin ~= 3.91 mW
PS2 ~= 20 nW --> ~~ 5 ppm !!! |
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Beam size at closest spherical mirrors position, posted by Loïc Amoudry at Optical room about lasers and optics
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S3 and S2 @ +1 640 000 and P1 and P4 @ -825 000
Diameter in x: 4.7mm
Diameter in y: 4.7mm |
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Transmission of the mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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After verification, transmission of P1 correspond to ~150ppm.
The 1337ppm come from a beam leakage. Reflection from P1 goes to the input window which reflects again a part of the beam directly into the cavity
between P1 and S3 then between P4 and S2. |
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Transmission of the mirrors, posted by Loïc Amoudry at Optical room about lasers and optics
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P1 transmission out of the mount (means angle of the mirror is not the real angle):
Pin = 3.2 mW
Pout = 545 nW |