Kevin moved the M4 mirror controller from the ISP controller to some ICEPAP controller.

the IHM to access this ICEPAP controller is accessible by launching 'jive' from any account ('operateur.thomx' for example).

once in the jive window, one has to select the 'device' tab, then select the OC=>OP=>OCH.02-MOT.03 device.

an AtkPanel is launched in which one can change the step values which are direclty the motor steps.

one problem is the FP-cavity/laser lock loss when one moves a FP-cavity motor.

with acceleration = 0.01 units/s² and velocity = 50mm/s (here, the 'mm' unit seems strange as it is very fast), it's enough to make a move fast enough for small displacements (10 steps for example to center PZT position) and it seems that the cavity stays locked (only the FP-cavity/laser is locked).

=> to be checked when both FP-cavity/laser and FP-cavity/RF-reference feedback loops are running.

today for the first time, we were able to make a long term lock of all the elements (Laser on FP cavity and FP-cavity on RF reference) during 20 minutes @50kW without any single loss of lock.

the success of this long term lock was coming from the possibility to drive the Smaract motor in piezo-scan mode and to apply a heating on one vessel of the FP-cavity to let its frequency slowly drift always in the same direction.
then, the FP-cavity motor can follow this drift without any loss of the lock.

even when we lost the lock, it was quite easy to get it back because of the frequency drift, always in the same direction due to the FP-cavity heating with the heating cable.

a good strategy to make this double lock :
1) adjust the laser frequency to the RF reference frequency in using the Smaract motor in "closed loop" mode until reaching a beating < 10Hz.
2) search for FP-cavity resonance in using the ISP motor of the FP-cavity
3) once the laser is locked on the FP-cavity, the FP-cavity length changes => work on the FP-cavity motor to follow the drift until one reachs a thermal equilibrium.
4) once the thermal equilibrium is reached, one can switch on the heating of the heating cable to continue the slow "thermal" drift in the same direction 5V of total voltage should be enough for 1h of work.
5) in the same time, one need to cancel the frequency offset between the RF reference and the FP-cavity using the FP-cavity motor and one need to follow the laser cavity fluctuations using the Smaract motor in "closed loop" mode.
6) once the FP-cavity is at the same length than the RF-reference, one can close the second loop (when both PZT are in the middle of their range).
7) at that point, one need to swap the Smaract motor control to "piezo scan" mode => one follows only the laser fluctuations ~ 1µm peak-peak
8) one always follows the FP-cavity drift using the IcePap controller on the FP-cavity motor, 10 steps by 10 steps => it should work during 1h.
9) when one reachs the thermal equilibrium again, one can add 5V to the heating cable voltage.
 

today, I did a 20 minutes "double lock" run w/o any single lock loss.

the attached file shows the recorded RMS beating voltage between 500MHz signals (laser harmonic and RF reference).
the end of the plot after iteration ~1.8k shows the lock loss to the RF reference.

when the lock is not working, one gets a sine signal V=V0*sin(phi(t)) with V0=288mV => Vrms = 288/sqrt(2)) = 204mV rms
(this signal is not on the figure)

for low phase values : V=V0*dphi
when the locking is good, this voltage is about V = 3.5mV rms => dphi = 12mrad rms
a full beating signal period (500MHz => 2ns) corresponds to 2pi, so dphi = 12mrad rms => jitter dt = 4ps rms

this afternoon, we did a new long-term "double lock" run w/o any single lock loss during 1/2h.

we did 2 acquisitions :

fig 1 : phase measurement between the 33MHz signal coming from the laser and the 500MHz RF.
this plot doesn't last 1/2h.
the measured jitter is ~45ps, at the limit of the scope resolution.

fig 2 : same phase measurement between the two 500MHz signals (laser and RF)
the lock is lost at the end of the plot.
the measured voltage noise is Vrms ~ 2.5mV rms => jitter ~  2.8ps rms

the conversion factor between jitter and voltage is 1,1 ps / mV

!!! CAREFUL !!! heating the FP-cavity with the heating cable works in the opposite direction of the heating due to power in the cavity !

laser cavity :

when one decreases the laser motor position, the laser repetition rate increases (laser cavity length decreases).
=> +/- laser motor step  =>  +/- laser cavity roundtrip length => -/+ laser repetition rate => -/+ laser harmonic @500MHz 
=> +/- 100nm => +/- 200nm => -/+ 0.7Hz @33.33MHz => -/+ 10Hz @500MHz

here is the natural variation of the laser cavity frequency beating with RF @500MHz over 1h (~1.6s / iteration)
one can see some oscillations equivalent to ~1µm of roundtrip length with ~10 minutes period and maybe a slower drift or oscillation with ~2µm of roundtrip range over the hour.
I mention that I moved the laser "PZT" motor before taking the data : could it be the reason of the 10-20min oscillations ?

during the same time, here is a probe temperature curve (the probe in stuck on the end flange, close to X-hutch, of the FP-cavity, inside the housing... not close to the laser position).
the temperature variation range is ~2.5/100 °C which induces on inox (relative length thermal effect : 17e-6 /K) a length variation of 4µm of roundtrip (10m) which could be compatible to the laser cavity length variation measured.

Now, I placed a temperature probe stuck on the laser housing itself.

fig. 1

one can compare the temperature measured at the surface of the laser housing and the beating frequency with the 500MHz reference oscillator
one sees a possible very long term correlation but there is no correlation at the minute level when we see the frequency oscillation after t=2000s.

the laser housing temperature seems not to induce directly a frequency variation.

fig 2 / 3

we applied 15W on the heating wire rolled around the FP-cavity flange.
in red, we see the temperature increasing on the probe rolled around the wire, reaching almost 30°C.
we heat the inside of the housing (airflow stopped) during more than 30 minutes
in green, we don't see any variation (even if one makes a zoom) of the temperature of the probe stuck on the laser housing.

in same time, on fig 3, one can see the frequency drift.
there is no correlation between the oscillations and the temperature.

CONCLUSION :
the laser frequency fluctuations does not seem to come from the outside temperature.
 

the last thing we did with Daniele, is to start/stop the airflow on top of the housing (closed) to see a possible pressure effect on the laser frequency drift.

fig 1 : in green, the temperature measured with the probe stuck on the laser housing.
one can clearly see the 2 "start - wait ~10mins - stop" we did at 16h50 then at 17h30.
the air temperature blowed by the airflow is cooler than the housing temperature and we see the effect on the probe.

fig 2 : this is the laser frequency drift during the 1st airflow start/stop
the airflow has been turned on at 100 iterations and stopped at 500 iterations (~5 mins)
we don't see any correlation

fig 3 : this is again the laser frequency drift during the 2nd airflow start/stop
the airflow has been turned on at 1850 iterations and stopped at 2550 iterations (~10 mins)
we don't see any correlation

CONCLUSION : neither external temperature change or pressure variations can explain the 10-20min period oscillations observed on the laser frequency variations.
it can be either the laser temperature regulation or the RF reference oscillator temperature regulation (due to the oven of the quartz)

today, I swapped the 500MHz RF reference oscillator for a Siglent 500MHz DDS oscillator.

see the attached plot : the beating frequency with the 500MHz laser harmonics produces the same behavior as before.
so, the oscillations should come from the laser temperature regulation.

long-term correlation, over 5-6 days, between the temperature measured in the bunker, outside of the housing (blue curve) and the temperature measured with a probe stuck on the laser housing, inside of the FP-cavity housing (green).

it's a perfect correlation with almost the same temperature scale : 1°C outisde the housing => 1°C of laser housing

thus, a stabilization of the temperature, inside of the housing, could help to reduce the frequency drifts of the laser.

this morning, I did a 500MHz beating frequency (Laser vs RF) drift test with the Smaract motors configured with "Sensor Mode" OFF over 50 minutes (~ 1500 acquisitions)

compared with previous measurements, one observes a much more smooth "exponential-like" drift compared to "Sensor Mode" ON (see previous posts).

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

This afternoon, I did the 2nd half of the travel: dF @ 33MHz = 0Hz
=> the Smaract motor position is now at +1750µm
=> the FP cavity motor Mot.03 position stayed at -200 000 steps
=> the FP cavity motor Mot.06 position is now at -790 000 steps
the PDin photodiode was at 3.191mW @ 33% amplifier ratio
the PDpulse photodiode was at 33.372 / 33.371MHz

the FP-cavity power is ~47kW @ 33% amplifier ratio => to be improved

there is no signal beating at 500MHz, only at 33MHz => to be investiguated => fixed

This morning FP Laser was operating well locked at 30 KWatts in stable vay.

There are some fluctuations due tu pointing instabilities probably dues to temperature fluctuations in de bunker.

In the attacced picture are reported the lock parameters and signals.

By adjusting the position of laser caviti length the lock old all de morning.

today, I installed a laser dump just before the telescope to avoid any high power (50W instead of 17W usually) issue in the injection line.
last time, we saw some plastic mounts of the polarizers slightly burnt because of some small misalignment.
I used a thorlabs LB2 (see picture) which is able to manage 80W CW or 25J/cm2 pulses => this is OK in both cases : 50W CW / 1.5µJ/pulse for ThomX.

I started the laser amplifier at 70% which produces 50W at the amplifier output and 45W at the input of the FPC.

start : 15h10
immediately, the Temp Amp1 increases from 26°C to 30°C
the Temp Amp2 stays around 26°C
PD_OUT = 79,2W

start + 5-10 min
Temp Amp1 : 31°C
Temp Amp2 : 27°C
PD_OUT = 79,2W

start + 30 min
Temp Amp1 : 31,6°C
Temp Amp2 : 27,5°C
PD_OUT = 79,2W

start + 1h00
Temp Amp1 : 31,6°C
Temp Amp2 : 27,6°C
PD_OUT = 79,2W

start + 1h30
Temp Amp1 : 31,7°C
Temp Amp2 : 27,7°C
PD_OUT = 79,2W

start + 2h00
Temp Amp1 : 31,7°C
Temp Amp2 : 27,7°C
PD_OUT = 79,2W

start + 2h30
Temp Amp1 : 31,7°C
Temp Amp2 : 27,7°C
PD_OUT = 79,2W

today, we locked the FP cavity at ~50kW with 30% laser amplifier ratio (16W) during almost all the day (from 10am to 4pm)
CEP optimized for MCS-1/Ch2 = -244µm at the end of the day.

once one finds the proper CEP value to reach to correct loops gain, the cavity lock and power are very stable:
one looses the lock only when one needs to use the Smaract motors to follow the long temperature drifts.
several elements of the ThomX machine have been powered ON progressively during the lock without any lock perturbation excepting for a very short time when switching ON the RF cavity (to be confirmed) and when one tried to inject electrons into the ring (loss of the electrons after few turns only)... but it's not very clear. the lock is still stable but some time one sees a lock loss without "reason"... could it be the electron loss or some bad compensation of the noise due to feedback, it's hard to say.

at the end of the day, I had to realign the FP-cavity injection and change the CEP more often than in the morning,
and surprisingly, the intra-cavity power drops a little bit at the begining of the lock (~50kW) and after some tenth of seconds (=> ~47-48kW).
it is not so much but it is very repeatable at each try.
I tried to optimize the CEP, the injection alignment, the PID parameters => it helps but at the end, I still have this slow power drop of few kW over tenth of seconds that I didn't see at the begining of the day... to be investigated.

as the temperature is back to a normal value ~ 20.8°C, the injected power to the amplifier (PD_IN in the Alphanov software) is back to 3.15mW without doing any alignment.

this morning the lock was around 48.5kW with 30% laser amplifier ratio (16W) after CEP/alignment tuning.

temperature since we moved to temperature probe (jump at the beginning of the plot) below the ring on a metallic base.

temperature @ 22.3°C

today, all the PC applications were closed except the web browser.
I had to restart all of them, then try to relock.
(maybe I let the terminal window open with all the apps and someone tried to unlog by removing them ?)

the cavity height was pretty misaligned.
after a rough alignment, the power inside the cavity was back at 49kW for 30% amplifier ratio.

the CEP motor needs to be adjusted a lot during the cavity heating process

temperature @ 21.9°C

48.5kW inside CFP for 30% amplifier ratio

Frep Laser motor = 123.4µm
CEP motor = -67.8µm

below the image of the relative voltage range between CFP PZT (pink) and laser PZT (green).
the CFP PZT is driven by 10x the voltage range showed by the scope (0-100V HV output and 0-10V monitor on the Laselock)
one can see on the scope that the relative range of both PZT voltage range is roughly the same which means that the real CFP PZT sensitivity is 10x smaller than the Laser PZT sensitivity.
as the CFP PZT is driven by 0-100V and the Laser PZT is driven by 0-10V voltages, they have approximately the same range which is ~200nm (calibrated with the Laser motor in closed loop mode).

in a previous email, the CFP PZT should be given with a sensitivty of about 4nm/V => 400nm/100V of length range => 800nm/100V of CFP roundtrip range => 80e-9/100V of relative sensitivity => 40Hz of frequency peak-peak range for 500MHz carrier frequency.
there is a discrepancy between measurements (~10Hz peak-peak range for 500MHz carrier) and expected value !