ELOG THOMX commissioning

mechanics | lasers and optics | detectors and electronics

Current Installed Setup

Attached is the current setup in ThomX

Attachment 1: 18-02-2022_ThomX_FPCavity_Finesse_Setup.jpg

102

Tue Oct 27 13:13:50 2020

Coatings reflectivity curves and datas for HR Saphir, HR Suprasil and HR ULE.

Attachment 1: HR_Saphir_Théorique.PNG

Attachment 2: HR_Suprasil_Théorique.PNG

Attachment 3: HR_ULE_Théorique.PNG

Attachment 4: Table_HR_Saphir.TXT

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... 702 more lines ...

Attachment 5: Table_HR_Suprasil.TXT

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... 702 more lines ...

Attachment 6: Table_HR_ULE.TXT

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... 702 more lines ...

Wed Jan 16 14:54:14 2019

Loïc Amoudry

lasers and optics | utilities

report

Optical room

Cleaning outside IP cavity

From 7th january to 11th january.

Attachment 1: Avant_nettoyage.jpg

Attachment 2: Apres_une_semaine_nettoyage_lingettes_et_brosseadents.jpg

Attachment 3: Sans_UV_traces_scotch_nettoyees_apres_baking.jpg

307

Fri Dec 22 09:46:18 2023

lasers and optics | detectors and electronics | software

Christmas shutdown

this morning, I shut off all the equipements (especially the computer) except the ones powered by the UPS : laser controller, laser peltier controller, laser motors controller.
and I disconnected the cables from the power plugs of the wall (to prevent any possible overvoltage).

Jean-Noël Cayla will need to shut off the electrical shelf (the one powering the UPS) during the afternoon, I will check at this moment if the laser controller is still properly powered thanks to the UPS.

308

Fri Dec 22 16:13:27 2023

lasers and optics | detectors and electronics | software

Christmas shutdown

this afternoon, I checked visually what happens when the AC power of the UPS is broken down => the laser controller has still its "emission" button ON... no AC interruption.
so, I guess the UPS switched properly the output AC line from the input AC line to the internal batteries.

Ronic Chiche wrote:

378

Wed Nov 20 11:28:01 2024

this morning, with Daniele, we checked the amplifier power, right after the CVBG (the power meter has to be placed on a metal plate above the large table hole), and just at the input of the FP cavity, after the 1/4 and 1/2 waveplates (the power meter has to be placed on flat beam dump+ Thorlabs beam dump + V metallic mount to be at the right height).

we compared with the power measured the 9th of september : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/356

the 3 collumns are the measurement close to the CVBG on 9th of september / same position today / just befor the FPC today

amplifier ratio (%)                 power after compressor (W)                 (new) power @ CVBG (new) power @ FPC      ratio FPC/CVBG power (%)
10                                               0.91                                                  0.93                                    0.83                                       89.2
20                                               8.6                                                    8.6                                      8.0                                         93.0
30                                              16.7                                                  16.9                                    15.8                                        93.5
40                                              25.5                                                  25.6                                    24.0                                        93.7
50                                              34.5                                                  34.6                                    32.5                                        93.9
60                                              42.5                                                  42.5                                    39.5                                        92.9
70                                              50.0                                                  50.0                                    45.0                                        90.0

we observed with the viewer the beam on the powermeter.
at 70% of amplifier ratio, the beam size is as big as the powermeter detector.
then, the 93% to 90% transport efficiency drop could come from this "too small" powermeter detector.

we observed also at this power ratio (70%) that the 1/4 and 1/2 waveplates were not perfectly centered and we burn a part of the platic mount at this power.

379

Wed Nov 20 12:00:47 2024

we did a long term run (25 mn) with the powermeter located at the FPC position at 33% amplifier ratio.

the initial power was 18W .
then, it goes to 18.5W in 10 minutes, then 5 minutes later, it goes to 18.3W and stay stable until the end the run.

Ronic Chiche wrote:

we compared with the power measured the 9th of september : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/356

the 3 collumns are the measurement close to the CVBG on 9th of september / same position today / just befor the FPC today

we observed also at this power ratio (70%) that the 1/4 and 1/2 waveplates were not perfectly centered and we burn a part of the platic mount at this power.

380

Wed Nov 20 12:42:11 2024

I put back and aligned the 1/2 waveplate only and I get 71kW max after its optimization and optimizing the CEP and alignment (without walking procedure).
this waveplate change a lot the reflected power seen on the CH2 of the scope.

to be continued this afternoon...

Ronic Chiche wrote:

we did a long term run (25 mn) with the powermeter located at the FPC position at 33% amplifier ratio.

the initial power was 18W .
then, it goes to 18.5W in 10 minutes, then 5 minutes later, it goes to 18.3W and stay stable until the end the run.

Ronic Chiche wrote:

we compared with the power measured the 9th of september : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/356

the 3 collumns are the measurement close to the CVBG on 9th of september / same position today / just befor the FPC today

we observed also at this power ratio (70%) that the 1/4 and 1/2 waveplates were not perfectly centered and we burn a part of the platic mount at this power.

381

Wed Nov 20 18:55:37 2024

Check of mirrors and coating directions

this afternoon, we put back the 1/4 and 1/2 waveplates and after a long alignment/angle tuning/CEP optimization process, we hardly got 80-81kW in the cavity for 33% amplifier ratio. the transmission photodiode is then ~ 7.5 divisions (500mV/division) on the scope.

BUT during the 1/2 and 1/4 waveplate angle tuning process, we clearly saw:
- a reflection signal level which is very sensitive to the input polarization
- a coupling which can be almost zero with ~70kW inside the cavity
- the more important: ~9.5 divisions (500mV/division) on the scope with only 70-75kW in the powermeter
=> which device should we believe ?

the problem is all these photodiodes (reflection, error signal, transmission) and powermeter are aligned with mirrors which seem to be sensitive to the polarization state of the beam... and for the "output" beam side of the cavity, we cannot remove the mirrors because of the mechanics of the cavity which prevent a direct view of the ports. for the "input" beam side of the cavity, the output port is used for the cavity beam size measurement with a Basler camera.

we have to think to how to solve this issue !

Ronic Chiche wrote:

to be continued this afternoon...

Ronic Chiche wrote:

we did a long term run (25 mn) with the powermeter located at the FPC position at 33% amplifier ratio.

the initial power was 18W .
then, it goes to 18.5W in 10 minutes, then 5 minutes later, it goes to 18.3W and stay stable until the end the run.

Ronic Chiche wrote:

we compared with the power measured the 9th of september : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/356

the 3 collumns are the measurement close to the CVBG on 9th of september / same position today / just befor the FPC today

we observed also at this power ratio (70%) that the 1/4 and 1/2 waveplates were not perfectly centered and we burn a part of the platic mount at this power.

Tue Mar 26 18:26:32 2019

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).

Attachment 1: ThomX_P4.jpg

367

Tue Oct 8 11:59:27 2024

Characterizing Focus Tunable Lens

Yesterday Ronic and I worked on the high laser power measurements with the Vertical set-up of the Focus Tunable Lens. We went upto 38W@4 dpt at the begining and then also changed the focal power at 38W.

Observation:

1. We observed nice rings @38W 4dpt, maybe it hits some optics we have to check.

2. We also observed flactuations of power for two adjacent index of the beam profiler when we increase the laser power, which we need to understand.

3. We could see that the vertical deformation is not present for this set-up, we could remove the effect of gravity by this set-up.

Attachment 1: Updates_of_Focus_Tunable_lenses.pdf

Thu Oct 3 13:53:44 2019

The cavity is right now at 6.5e-8 mbar (turbo pumps on for 1 night and ionic pumps for 3h), primary pumps and turbo pumps are cut, ionic pump are on and the pressure level is still going down.
Therefore there aren't any big leak in the cavity and we can expect a final vacuum level close to e-9 mbar.

Thu Sep 12 16:19:26 2019

Loïc Amoudry