on last friday (12/01/2024), the IcePap DS issue was solved and I was able to control the FP-cavity motors properly.
I was able to quickly lock either the laser on the FP-cavity and the FP-cavity on the RF reference as before.

then, we can close these posts on restarting the equipments after the Christmas shutdown

this morning we locked the laser and the FP-cavity with ~ 40kW => some HOM appeared "randomly" depending on the power.

we tried to play manually on the L-shape arm :
- first, we moved horizontally to put the L-shape in the beam axis
at some point, we saw the power level divided by ~2, we stopped and came back to restore the full power.
- then, we tried to move vertically.
whatever the direction, we were not able to see a clear cut of the beam.
BUT "strangely", at some point, the PZT drift followed the direction of the motion and was not really depending on the "cooling" or "heating" process when the lock stops or restart.
"strangely" again, at the endpoint, the power dropped by ~20-30% after a delock but it was impossible to restore the power when we put the arm at the initial position.
=> we had to adjust the FP-cavity alignment to restore the power !!!
=> we had the feeling that moving the arm could have misalign the cavity axis !!! :-(
=> we have to discuss with Yann and get the CAD files of the cavity to have a better understanding...

here is the picture of the L-shape arm and the inside of the vessel.

this image corresponds to the "zero" position on each positionner.

yesterday with Daniele, we tried again to move the arm horizontally and vertically from the "zero position" to have a better understanding of the beahvior,
but it is roughly the same :
- a clear beam power reduction (=> cut of the beam) when one moves the horizontal axis
- a very small beam power reduction when one moves the vertical axis

as there are no end-position limits on the axis and as it is possible to "touch" the motors or different mecanichal pieces, we prefered to be conservative:
after several tries, one placed the arm at a position where the HOMs seem to be pretty well suppressed.

for the moment, we will consider this arm in a proper position.

Mail de Yann du 12/10/2018 :

Je vous fais le bilan des actions effectuées :

1/ La mécanique a été remontée avec changement des billes céramiques, soufflet défectueux, ect...

2/ Test et mise en place des vérins en position

3/ nettoyage des chambres et insertions de la méca

4/ connectorisation des câbles perlés et test des vérins par le soft

5/ fermeture des brides

6/ nettoyage du marbre et de la zone

On est donc prêt pour les test de vide et d'étuvage.

RAPPEL pour tous :

Des nouvelles combinaisons propres sont à disposition (on ne sort pas du flux avec la combi !)

Mettre MASQUE / CHARLOTTE / COMBI / GANTS !

Ne pas rentrer de CARTONS ou autres sources de pollution.

NETTOYER les outils ou objets à rentrer dans la zone

RANGER après les manips.

Mail de Yann du 8/10/2018 :

Bonjour,
Tous les vérins sont maintenant OK ! Merci Ronic.
La cavité a été réglé en mode nominal (tilt à +2/-2 et Z à +5/-15 ou -5/+15).
Demain avec Christopher on remet tous dans les enceintes à vide.
Du coup, Patrick tu pourras ré-connecter les câbles céramique (à partir de demain apres midi).
On est dans les temps pour des tests de vide et d'étuvage a partir de lundi prochain.
A+
Yann.

For ~ 46kW power in the FP-cavity:

• Alplhanov amplifier ratio : 20%
   
• Axis 18 position : -0004710 steps
   
• PID A (for laser/FPC lock) :

input : input a
P = 0.06
I = 0.0007
D = 0.85
Sign : positive
Sampling : fast
filter : off

• Search A :

criterion : input d
upper th. : 10V
lower th. : 0.04V
speed : 100V/s
relock mode : none
off mode : hold

• Output A :

range : 50%
offset : 5V

• PID B (for RF/FPC lock) :

input : input b
P = 3
I = 0.00002
D = 2
Sign : negative
Sampling : mid
filter : off

• Search B :

criterion : input c
upper th. : 0.45V
lower th. : -0.45V
speed : 1V/s
relock mode : none
off mode : hold

• Output B :

range : 20%
offset : 5V

For ~ 23kW power in the FP-cavity:

• Alplhanov amplifier ratio : 15%
   
• Axis 18 position : -0016014 steps
   
• PID A (for laser/FPC lock) :

input : input a
P = 0.1
I = 0.0016
D = 1.4
Sign : positive
Sampling : fast
filter : off

• Search A :

criterion : input d
upper th. : 10V
lower th. : 0.03V
speed : 100V/s
relock mode : none
off mode : hold

• Output A :

range : 50%
offset : 5V

• PID B (for RF/FPC lock) :

input : input b
P = 5
I = 0.0001
D = 1
Sign : negative
Sampling : mid
filter : off

• Search B :

criterion : input c
upper th. : 0.45V
lower th. : -0.45V
speed : 1V/s
relock mode : none
off mode : hold

• Output B :

range : 20%
offset : 5V

For ~ 66kW power in the FP-cavity:

• Alplhanov amplifier ratio : 25%
   
• Axis 18 position : +0018369 steps
   
• PID A (for laser/FPC lock) :

input : input a
P = 0.1
I = 0.0016
D = 1.4
Sign : positive
Sampling : fast
filter : off

• Search A :

criterion : input d
upper th. : 10V
lower th. : 0.03V
speed : 100V/s
relock mode : none
off mode : hold

• Output A :

range : 50%
offset : 5V

• PID B (for RF/FPC lock) :

input : input b
P = 5
I = 0.0001
D = 1
Sign : negative
Sampling : mid
filter : off

• Search B :

criterion : input c
upper th. : 0.45V
lower th. : -0.45V
speed : 1V/s
relock mode : none
off mode : hold

• Output B :

range : 20%
offset : 5V

The cavity has been cleaned then put under primary vacuum (primary pump without vacuum flow control). Dusts presence was checked at air and no significant changes have been observed.

1ST image before cleaning
2ND image after cleaning
No changes after coming back from primary vacuum

A power up has been performed on ThomX until 65kW intracavity power. We didn't see any modes but stored power was really unstable since ~60kW (see image tek00004.png).

Measurement report is shown in the table below. Gain seems to decrease against intracavity power.

As a conclusion, pulse length compression does not seems to bring any trouble in the PDH loop. But at relatively high intracavity power, power start to be really unstable even if we did not see any mode.
We can notice that we tried to align, change CEP but it had no important impact on the quality of the lock. See further experiments with Ronic and D-shape.

to anticipate the power shut down on next tuesday 23/09,
this afternoon, I switched off all the equipments except the oscillator connected on the UPS.

this morning, I restarted all the equipments of the FPC.

everything was fine after being able to get back the correct PDH phase between modulation and demodulation...I got 88kW with 33% amplifier ratio after basic alignment and CEP tuning.

the Pico1 server used for the X-ray photodiode TMD.01 doesn't want to start...
I tried with Astor. the server start to run (red => blue => green colors)
but when I start the Jive panel, it gets down again (red color)... to be solved

the 33MHz/500MHz RF frequencies from the Ring seems different from the previous state (maybe working at an energy of 50MeV instead of 70MeV which was the previous energy ?).

so, I let the FPC at the present position and wait to discuss if it is necessary or not to move the FPC motors for the correct energy...

This morning I did a phase alignment on the PDH signal generator (Rigol DG4102)
this procedure ensure that both phases of the sine wave signals are aligned before finding the correct phase for maximizing the error signal.

so, from now on, in case of power shut down, one just need to :

1) do a phase alignment

2) put the correct phase number on the 2 channels according to the picture (if not automatically done by the generator itself).

340° on channel 1
270° on channel 2

1) and 2) can be done in any order.

All the equipments have been switched off on Friday 17th due to a power shut down on Saturday 18th :
CW and Onefive oscillators, computers, laser amplifier, cavity mirror motors, chiller, etc...

Today, I restarted all the equipements :

Chiller                                                 : ok, temperature converged quickly to the set temperature : 25°C
Cavity mirrors motors controller         : I had to configure the general network as 192.168.xxx.xxx in order to operate the software designed by Didier Jehanno
Computer                                           : ok, now, it IP address is 192.168.1.1
Laser amplifier controller                    : I had a LOT of issues in restarting the LAL software. I had to restart several times the amplifier controller in order to access it by software. I quickly check the power increase to 50% after it has been correctly seeded
CW oscillator                                     : ok, Koheras restarted without any issue.
OneFive oscillator                             : the power ON was ok but it did not modelock. I tried several gently knocks on the case but without success (one clearly see the effect on the scope, the oscillator "tries" to modelock).
                                                            fortunately, after about 1h, the oscillator modelocked alone (check with Buddy fiber photodiode + scope).... the power is the same as before. the Alphanov software measures 5.4mW (it was 5.5 mW the 2/1/2023)

Smaract controller for OneFive        : ok, I changed its IP address to 192.168.1.10. I tested the PC control in moving forth and back the "CEP" motor by 1mm... the OneFive was still modelocked.
 

This morning, all the equipments have been switched off due to a power shut down tomorrow morning.
Only the Onefive oscillator is still ON, connected to the Uninterruptable Power Supply (UPS).

after alignment, CEP adjustment and optimizing the PDH phase, I got back ~92kW in the FPC for 33% amplifier ratio.

list of possible causes of the high frequency noise which makes the system loosing the lock => to be checked.
(if you have some new idea, I will edit the post)

1- Laser
   1.1- vibrations on the laser box coming from the optical table / housing
   1.2- vibrations coming from the Smaract translation stages (Frep or CEP) inside the laser box
   1.3- pressure noise coming from the weather (the laser cavity is sealed) on the laser box

2- Amplifier
   2.1- vibrations coming from the fans in the controler crate
   2.2- vibrations coming from the chiller (water cooling cavitation)

3- Beam propagation
   3.1- vibration noise coming from the housing / the table
   3.2- vibration noise coming from the motors of the injection mirrors

4- Fabry-Perot cavity
   4.1- pressure noise on the cavity vessels coming from the weather/air cooling
   4.2- vibrations coming from the rust on the mechanics
   4.3- vibrations of the mirror mounts due to temperature related to cavity power
   4.4- vibrations coming from the electron ring mechanics
   4.5- "vacuum" index variation coming from local ionization due to the electron beam
   4.6- vibrations coming from the far position (related to the middle range) of some mounts and due to the spring of the translations stage.

5- Feedback system / Electronics / CEM
   5.1- CEM votage noise on the laser or FPC PZT's