The Sbox currently has the injection from ThomX installed T ~ 120 ppm , M2 planar from Sbox spare and M3 / M4 spherical mirrors from Sbox installed.

The last finesse measurement that was done gave a Finesse of ~ 19300 (After cleaning M2 using ethanol + aceton + pure water)

on Friday the whole optical table was cleaned again and the inside of the box was cleaned (even with a lot of dust inside the box the Finesse was 19300 )

all the mirrors were cleaned after using the three steps, M3 and M4 had clear visible dust on them.

D-shaped mirrors were installed again between M1 and M2

The alignment was redone and the beating observed ,  There is still a need for alignment improvement.

the cavity is under vacuum ~ 4.8*10^-2 mbar on Friday evening (~ 19h00) , The cavity is yet to be locked and to measure its Finesse

A PowerPoint showing the last finesse measurement and the error signal of the menhir laser lock

Max Finesse obtained @ 4 mirror setup was ~ 19 300 

With M1 from ThomX , M2/M3/M4 from SBox

Used the spincoater and pure water to clean dielectric mirrors which will be installed inside the SBox for directing the reflection line.

The method : place pure alchole on mirror - wipe it using white sterile tissue (in one direction) - clean with pure water in spincoater suing cotton swap .

After multible rounds, the result in the images was obtained. there is still a significant amount of dust particles (not all could be dust!!).

Not sure if the reason is the cleaning method ?? will invistegate it more !!!

Images of the SBox mirrors cleaned at the same time when the cavity was aligned.

Directly from the spincoater to the SBox directly.

PowerPoint attached shows details

PowerPoint shows the detailed images of all the mirrors before and after cleaning.

Images of SBox mirrors and M1 from Gamma factory attached only for the front after cleaning

the lines showing are on the back of the mirrors, they come from the spinning mount the mirrors are fixed on in the spin-coater.

Naming code :

               M#BB - M# mirror Back Before cleaning

               M#BA - M# mirror Back After cleaning

               M#FB - M# mirror Front Before cleaning

               M#FA - M# mirror Front After cleaning

               G : Gamma factory

Following the observation that when rotating M2 plan mirror of SBox the deformation position of the mode changes.

M2 was replaced with M2 spare of SBox

images of the mirror front side attached before and after cleaning, no spots at the center, but there seems to be 2 spots far from the center of the mirror.

After comparing with old images of M2 SBox spare, they do not appear to be damages, but dust !! (old image attached, taken on 10/12/2020, was never opened after)

While repeating the alignment, the mirrors were cleaned using the spin-coater and placed again.

The current mirrors placed in the SBox are

M1 plane injection from Gamma factory

M2 plane from SBox spare

M3/M4 spherical from SBox main set

no visible damage seen on the mirrors with the microscope

no images of the surfaces were taken due to time constraint.

1st version of the document.
if some information is not correct or missing, give any comment by replying to this post.

Start with the cavity lock images attached, taken from last week, at start we have a coupling ~ 5%  and started improving on the alignment .

The image of 00 modes attached corresponds to the coupling seen on the oscilloscope.

We have a higher coupling with the 11 mode due to the size of the injected beam in comparison to mode

lenses were added to improve it.

Current setup at SBox for locking the cavity

After spacial matching, the coupling increased to ~ 15 - 20 % 

The locking was done for the fundamental mode, tried to improve the coupling with the motors, but the lock is very unstable to be investigated. (Note: the cavity in under normal pressure)

Cavity locked today under vacuum and no airflow, it is stable over a long time

the alignment was improved and an increase of the transmission by 20 % from its original value

unfortunately,  data from the oscilloscope was saved, but it was not in the correct format (image) to show.

Attached ; the mode shape, the new motor positions. 

Closing the series for the setup

The cavity was only locked @ 133.33 MHz but the Finesse was not measured

The FSR was changed to match the new laser MENHIR 216.6625 MHz 

The amplifier was installed on the optical table next to SBox table.

The CVBG that will be used for stretching before amplification needs cleaning (they are very fragile, 'ask victor for best method')

The software to drive the diodes of the amplifier we have is not the compatible one.

Amplifier placed next to the pulsed laser on the table under the airflow

The output is in free space with height from the table of about 10 cm, note the injection height into the cavity is between 14 - 15 cm.

a power cable is placed but not plugged.

Connection to the computer is made using USB B on amplifier to USB A  (note need a longer cable, the available on is too short)

The cooling, to be connected to an outside chiller, will use the bottom one shown in the image attached.

The two water tubes, from chiller to amplifier,  has been marked. The size of the tubes from the amplifier fit inside the tubes from the chiller.

The current setup of the optical table attached.

The cavity is aligned and the lock of the fundamental mode has been attempted, but the mode is drifting too quickly to be able to follow.

I have placed the cavity under vacuum for a better stability.

a simple telescope for the CW was adjusted to having 2 lenses of 300 mm placed ~ 250 mm away from the colimator and 200 mm lens placed after it with 510 mm.

Before injecting into the amplifier, the pulse needs to be stretched using a CVBG, type attached.

the CVBG is to be used at a small angle, the beam shape and spectrum after the PBS is attached.

After measuring the beam profile, a mirror was placed to direct all the power for fiber injection

power before the fiber is 13 mW and the power injected is 6.19 mW

The software to control the CELIA amplifier is on the laptop that was placed in ThomX bunker.

I have placed it in the PLIC room next to the SBox table.

it is called 'Alphanov Control Software'

Closing series

closing series