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

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.

Cavity should be ready to clean for the new term 2019

Le 19/12/2018 à 14:56, Bruno Mercier a écrit :

Bonjour Daniele, Loïc,

Nous sommes à votre disposition pour effectuer une entrée d'azote sur
la cavité.

Bruno

From 7th january to 11th january.

08/02/19 - End of the cleaning process.

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).

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 two years in plastic boxes. LMA people explained that some company do not let anything more than 6 months in these boxes for pollution issues.

We merged into the same conclusion, clean the mirrors in case of pollution. Finally, they took the mirrors and we will go to LMA to recover them between 11/02 and 14/02. 

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).

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
M1 = S2
M2 = S3
M4 = P4

The wires are plugged as follows (I use notations wrote on the cavity and wires):

M3x = 1-1
M3y = 1-2
M3z = 2-1

M1x = 1-3
M1y = 1-4
M1z = 2-2

M2x = 1-5
M2y = 1-6
M2z = 2-3

M4x = 1-7
M4y = 1-8
M4z = 2-4

FSR initiale : 33.34 MHz (S3 = -825000 et S4 = -825000)

Beam size initiale : wx=2.05mm et wy=2.15mm

Finesse initiale : 3400

FSR après éloignement des miroirs sphériques : 33.29 MHz (S3 ~= -1496000 et S4 ~= -1496000)

Beam size : wx=1.7mm et wy=1.85mm

Finesse : 3600

FSR après rapprochement des miroirs sphériques : 33.39 MHz (S3 ~= -250000 et S4 ~= -500000)

Beam size : wx = 2.1mm et wy=2.4mm

Fit de la caméra jamais au dessus de 90%. ~~80%.

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.

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.

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.

On P4 we noticed a spot which seems to be in the coating (does not move while sending nitrogen).

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).

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).

reminder : lower values on the motors makes the motor tip going inside which makes the cavity length larger.
thus spherical mirrors are in default position with a possible big range to put inside the motor tip (for thermal effects compensation).
by complementarity, plan mirrors are in default position with a possible big range to put outside the motor tip.

the Labwindows CVI was buggy about the proper representation of the motors motion in Z direction (wrong direction and wrong default position).
the software is now fixed.
 

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 :
   - for thetaX axis, steps in one direction seem to have a different length from steps in reverse direction.
   - for thetaY axis, trying to move in one direction, makes sometime a motion in the reverse direction.
at this moment, it is difficult to say if the problem comes from the controller, the mirror mount or the motor itself.
if both axis are concerned on the same mirror (P1), maybe the problem comes from the mount... to be continued on Monday.

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
Through S2: ~0.950uW
Through S3: ~0.930uW
Through P4: ~0.850uW

We openned the cavity, removed S2 and measured trans of P1 and same for S2.

Pin ~= 3.91 mW
PS2 ~= 20 nW --> ~~ 5 ppm !!!
PP1 ~= 5.23 uW --> ~~ 1337 ppm !?!?!

P1 is the Sapphire mirror. 3mm thick. Tomorrow we'll measure its trans again, being out of the mount for constraint issues.

S3 and S2 @ +1 640 000 and P1 and P4 @ -825 000

Diameter in x: 4.7mm
Diameter in y: 4.7mm

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.

P1 transmission out of the mount (means angle of the mirror is not the real angle):

Pin = 3.2 mW
Pout = 545 nW
Offset = 68 nW

Transmission = (545-68)/3.2e6 = 149 ppm