Yesterday, we received the controller back from Alphanov
and I tested it immediately in the optical room.
if the software is properly talking to the controller, everything works normally.
then, one just have to remember that is mandatory to have the software properly connected to let the controller start electrically (power supply activated on the main boards)

Today, I installed it in the casemate with all the connections to the laser input, output, laser head, safety connections, etc...
and it works properly.

- The power in the fiber from the strecher is at 6.3mW.
the software reads 5.3mW but after a long fiber... then it is OK.
=> one strange thing : it detects 100MHz instead of 33MHz => to be reported to Alphanov !

- Amplifier output power measured after 2 mirrors :
0%                 =>               230 mW
10%               =>               880 mW
20%               =>               8.8W
30%               =>               17W

which are the numbers we had before.... then we are back to normal conditions to continue the commissioning.

today, I tried to restart the amplifier at 0% (without 3rd stage) but it didn't start... still the same error message.

but the PD_IN power and the PD_PULSE frequency seems correct.... I will try to power the amplifier OFF and ON later to see if one can reset this error.

edit : finally, a the end of the day, I switched OFF and ON several times the amplifier but I always get the same error message "bad sequence error".
I tried to use the Alphanov software to see if we can get more information about the error :
the watchdog LED is RED => I have to check if it is normal or not before starting the amplifier
and the PD_CRI LED is RED => normal because the preamp stage is not started (and it does not want to start...)

PD_IN is at 3.1mV but a previous post says that the amplifier worked with 2.7mV.
we can try to increase to 3.2-3.3 mW and see if it works....

edit : it seems we already had this kind of error before.
Guillaume suggested to check the average power of the seeder at the output of the fiber, the repetition rate and the stability of the signal.
previous post (https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/179) have shown an input power (PD_IN) around 5.7mW (see the attached image) !
this power was maybe obtained without any EOM which divide the power by ~2.
=> we can try to remove it temporarilly to check if the amplifier is able to restart in this condition... to be done

the air temperature is between 21°C and 22°C.

I tried to lock the cavity but it was very instable with only short time locks.
I had to increase the parameters of the PID:
P = 0.07
I = 0.0007
D = 0.706
after that, the lock was stable but we can see something in transmission (dark blue curve) which seems to be a degeneracy.

maybe because of the water cooling temperature, after stopping the laser amplifier, I was not able to restart it.
I always got an error (an alarm was triggered by bad sequence) when I want to switch ON the preamplifier at 0%.
the Temp Amp 1 is about 25-26°C... it is stange.
to be tested after the water cooling is repaired.

Yesterday, the ThomX water circuit should have been repared,
and yesterday aftenoon, Daniele restarted the chiller and I checked it this morning without any error.
BUT the pump of the ThomX water circuit is again in default...
Dalkia has been called to fix the problem.

despite this point, I restarted the laser amplifier this morning.
everything seems as usual and I can see some small resonance at the output of the Fabry-Perot cavity
BUT the reflection photodiode level doen't change when the amplifier is ON.
I need to check if the photodiode switch is set ON or if it is misaligned or dead.... to be checked.
in between, I prefer to stop the laser amplifier.

edit : the photodiode problem was coming from the PhD power supply which was OFF.
I just turned it ON.

this morning, the chiller was in error and I had to restart it.

the air temperature is around 21°C.

the water cooling has been repaired but the initial Temp Amp 1 is at 28°C.

I got 86kW in the FP-cavity with 33% of laser amplifier ratio after tuning the CEP and the alignment.
but the amplifier stopped after an error after 30 minutes => the Temp Amp1 reached 30°C => it's not normal.
the chiller was again in error. I tried to restart it but I got an ERROR14 : Thermostat error, the flow rate is zero !!!
the tubes for the inner circuit going to the amplifier are a little hot by touching them with my hand.
the tubes for the outer circuit going to the ThomX water circuit is hot for the "blue" tube et cold for the "yellow" tube.
it means there is no flow in the outer circuit.
Jean-Noel just told me it's normal because he stopped the ThomX water pump because of a too high temperature => Dalkia should fix the problem today.

OC/OP/OCH.01-MOT06 roughly at position -792 600 steps.
CEP motor = -211µm

the OC/OP/OCH.01-MOT03 is still faulty => to be fixed by Kevin.

this morning, the computer was restarted and I had to launch all the applications.
no problem except the powermeter for which I had to do a power switch OFF and ON remotely.

the chiller was in error and I had to restart it also.

the air temperature seems to be not properly controlled (see the picture)
one can see a constant temperature drop from Tuesday 9 April 10:30am.

it seems the water cooling is also not working properly as I saw the laser amplifier temperature (Temp Amp 1) increased constantly during the run from 24°C to 30°C (in 30 mintues).
=> it's not normal, it should be regulated at 25°C !

I got 89kW in the FP-cavity with 33% of laser amplifier ratio after tuning the CEP and the alignment.

OC/OP/OCH.01-MOT06 roughly at position -782 000 steps.
CEP motor = -425µm

the OC/OP/OCH.01-MOT03 is still faulty => to be fixed by Kevin.

this morning, I had to restart the chiller. Temp Amp 1 is at 27.5°C after having started the amplifier at 33% ratio.

I removed the 100kohms resistor on the Transmission channel, on the scope (now, it is 1Mohms), to get more sensitivity.

the air temperature is around 21°C and is stable during the last days.

I don't see any power coming from the amplifier despite it is at 33%... I think the MPS prevent us to work and the amplifier shutter is blocking the beam.
I will send an email to Sophie to check that point.

EDIT : Kevin showed me how to acknowledge the error on the MPS
=> go to "Detail" and then acknowledge the "vacuum error".

I saw the FP-cavity resonances but I didn't have time to optimize them as the water temperature is still too high and the chiller is not working good enough.
=> the amplifier did a safety stop.
one needs to wait this issue is fixed.

OC/OP/OCH.01-MOT06 at position -790 000 steps.
CEP motor = -300µm but far from the optimum CEP position.

from now on, the transmission factor for calculating the FP intra cavity power is 1/1.75ppm ~ 570 000 (changed in the Powermeter software)

this morning the temperature of the water cooling circuit is still very high said Sophie, and the laser amplifier temperature "Temp Amp1" is at 29°C instead of ~23-25°C
then, when I start the laser amplifier, it stops rapidly with a warning error.
I will check the chiller status as the Dalkia should fix the water temperature problem at some time (Sophie + Alice working on this point)

the air temperature in the bunker is back at 19.5°C from last Friday afternoon and is stable at less than 0.5°C.

after restarting the chiller, the "Temp Amp1" is now at 25°C before starting the power in the amplifier, it rises at 28.5°C after some minutes
I found the resonances with the motor OC/OP/OCH.01-MOT06 at position -783 460 steps.
and I had to tune the CEP to get the maximum resonances at -198µm.

with the new transmission factor, I got almost 90kW for 33% laser amplifier ratio after a simple alignment procedure.

the motor OC/OP/OCH.01-MOT03 is sill in error.

This morning, I locked again the FP-cavity at more than 50kW with 33% of laser amplifier ratio.

the temperature is measured today at 20.5°C despite the fact the air conditionning is still OFF.
the temperature, rising from 18°C, started monday at 11AM roughly.
maybe, the difference comes from the external doors of the Igloo which have been closed recently ? to be confirmed.
as the temperature is measured inside the airflow housing, all the powered equipements are disspating some heat, rising the inside temperature compared to the bunker temperature.
EDIT : Sophie Chance told me the water temperature cooling of ThomX was defective... the water temperature went to 29°C ! it is being fixed by Dalkia.
careful, we don't have a temperature measurement of the water going to the chiller...

to find resonances, I moved the OC/OP/OCH.01-MOT06 motor from position -770 000 steps to position -788 600 steps which corresponds to ~100µm !
it can be explained by the temperature change and also because during the lock last week, I let the MOT06 motor in position after the cavity was at 50kW.
I had also to change the CEP motor position from -170µm to -420µm and to do some alignment (with walking procedure).

accessing the motor OC/OP/OCH.01-MOT03 from the ATK panel, produces an error : "connection to device failed"... to be solved by Kevin ?

This morning with Daniele, we operated the FP-cavity to be sure there is no issue due to the Linac section changing operation :
- opening/closing the valves due to air pressure break down
- opening/closing the bunker roof
- large temperature change
- etc...

the temperature in the bunker dropped to 18°C instead of 21.5°C, so we had to do some FP-cavity alignment.
but after obtaining resonances and changing the CEP, we got more than 50kW for 33% of amplifier ratio => OK !

this morning I solved the problem of the 33MHz frequency beating which should be ~12kHz between the generator (at the new frequency 33.3378MHz) and the laser cavity frequency (still at the old frequency which is 33.35MHz)...
the generator providing the 33MHz frequency has 2 channels, and only one was set at the proper frequency !

so, I set both channels at  33.3378MHz and now I measure properly ~12kHz of frequency beating.

now, we can move the laser cavity and the FP cavity in confidence.

at the beginning of the procedure, the frequency gap between the new Ring 33MHz frequency (33.3378MHz) and the laser/FP cavities frequency was 12.33kHz
=> the Smaract motor position was at +100µm
=> the FP cavity motor Mot.03 position was at -358 720 steps
the PDin photodiode was at 3.151mW @ 33% amplifier ratio
the PDpulse photodiode was at 33.384MHz

after several moves (each time, one corrects the CEP / alignment to keep ~ 47kW inside the FP-cavity)
we can move the laser cavity at 300nm/s without any laser modelock loss
we move the FP cavity at the same speed (300nm/s = 50 steps/s with 1step  = 6nm)

now, we did roughly half of the travel : dF @ 33MHz = 5.3kHz
=> the Smaract motor position was at +1075µm
=> the FP cavity motor Mot.03 position was at -200 000 steps
the PDin photodiode was at 3.178mW @ 33% amplifier ratio
the PDpulse photodiode was at 33.377MHz

Today, we restarted the FP-cavity locking, after 3 weeks without using it.
those 3 weeks have been used to set the machine ring at the new (better) frequency : 500.067MHz (corresponding to a change of -183kHz)
or 33.3378MHz in fondamental frequency (corresponding to a change of -12.2kHz)

the power supply of FP-cavity photodiodes was OFF maybe due to some electrons losses.
we had to switch it OFF and ON to restart it.

the computer was restarted and we had to restart the applications and set their parameters.
in attachement, the parameters of the Kangoo software.
we had several "warnings" from the laser amplifier software => the amplifier stopped
but maybe it's because of the electrons not sent in the dump which pertubate the monitoring signal levels of the amplifier => to be confirmed

we had to do some alignment.
with 33% of  amplifier ratio, we had 49kW inside the FP-cavity.
we tried to move a bit the L-shape mirror but without any significant effect to improve the intra-cavity power.

we didn't start the laser and FP cavities length increase procedure.

surprinsingly, the beating frequency between laser cavity and 33.3378MHz is only 140Hz and not 12kHz as expected.... to be investigated
 

what does this 10ps phase jitter mean in term of cavity length variations ?

L = L0 + dL sin(2pi fm t) = L0 (1 + dL/L0 sin(2pi fm t))

F = c / L ~ F0 - F0² dL / c sin(2pi fm t) with F0 = c / L0

d/dt(phi) = 2pi F => phi = 2pi F0 t + F0² dL / (c fm) cos(2pi fm t) => dphi = F0² dL / (c fm)

dphi = 2pi F0 dt => dL = L0 * 2pi fm dt

dt rms = 10ps @ fm = 20Hz of modulation frequency <=> dL rms = 10 nm (L0 = 9m)

yesterday I did 2 tests to try to understand the origin of the 20Hz oscillation which is dominant in the remaining 10-20ps rms jitter between the transmitted pulses and the RF reference generator.

10ps rms jitter is equivalent to phase jitter dphi = 2*pi*f0*dt = 2mrad rms @ 33MHz or 30mrad rms @ 500MHz.

with V0 = 1Vpeak of beating signal amplitude, the equivalent rms beating voltage is dV = V0 * sin(dphi) ~ V0 * dphi = 2mV rms @ 33MHz or 30mV rms @ 500MHz

1) I did a beating between the internal photodiode of the laser with an external 33MHz oscillator (the photodiode is too slow to use higher harmonic).
the difficult part is to see the 2mV rms noise on a 2Vpp oscillating signal, so I locked the external 33MHz reference oscillator with the beating signal => see first plot.
there is no trace of 20Hz oscillation in the beating signal => the lock is too good and removed the oscillation ?

2) I did a beating between the photodiode in reflection of the FP-cavity (so the signal is not coming only from the oscillator but is going also through the Alphanov amplifier) with the 500MHz RF Ring generator.
I cannot the lock the generator anymore, so the measurement is done in open loop. I adjust the laser Frep with the motor to try to cancel the beating frequency => see 2nd plot
there is no trace of 20Hz oscillation in the beating signal => it is in contradiction with the previous post : "conclusion: the 20Hz oscillation is coming from the laser cavity" ?!?

maybe we need a more complex measurement scheme with the possibility to measure in the same time the 10-20ps rms jitter coming from the locked FP-cavity transmitted signal/500MHz Ring generator
AND the beating signal between the laser or amplifier with 500MHz local reference generator... to be done...