ELOG THOMX commissioning

Optimizing lock parameters for stable X-ray production

This afternoon, we scanned the optical table vertically with the hexapod in asynchronous mode to find its optimum position, looking at the X-ray production.
then, we searched for the correct bucket and phase in the bucket thanks to the Kevin script on the 500MHz and the 33MHz phases.

we got relatively easily some stable X-rays.
on the gain "0" on the current amplifier of the X-rays photodiode, we got 15 000 pA (380k Xrays / pA => 5.7.10^9 Xrays).
but we saw, when the cathode charge was fluctuating, that we could be saturated above 20 000 pA !

the power in the cavity was ~84kW after CEP and alignment tuning.

the command to launch the X-rays measurement window is:
taurustrend -r 100 /XLI/OP/TMD.01/I1

Ronic Chiche wrote:

This morning, I wanted to test quickly if the Smaract motors can be used in open loop instead of closed loop or in piezo scan.

the goal is to do very fine steps without to much vibrations (like with piezo scan mode) but with the full motor range (the piezo scan mode has a very limited range).

I can check what happens to the 33MHz beating frequency between the laser and the RF frequency without the laser amplifier or the lock of the FP-cavity.
1Hz of beating freqency variation is equivalent to 270nm of round-trip length, which is 135nm of motor displacement !

=> the full range of the piezo scan mode is difficult to estimate because the measurement sensitivity is not good enough but around 5Hz.

=> 1350nm in closed loop is equivalent to ~ 10Hz => 135nm is equivalent to 1Hz => ok

=> 1 step in open loop is equivalent to ~ 10Hz !!! => this is a way too coarse tuning !!!! => cannot be used unless one finds a way to set the motion differently in the settings parameters.
but usually, the settings parameters are used only to tune the speed, not the step size.

Ronic Chiche wrote:

Today with Daniele and Alice, we operated to cavity.
we obtained 84kW for 33% of amplifier ratio.
we had to tune the CEP @ -565µm and the FP-cavity alignment.

then we locked properly the FP-cavity on the ring RF frequency.
we quite easily relock with the correct phase when we are loosing the lock.

the ThomX machine was running during these 2 locks, so we are ready for doing X-rays again.

Ronic Chiche wrote:

here are the (good) lock parameters used this morning.

for the RF/FPC lock, the 33MHz beating signal used to select the right bucket is 1Vpp
=> beating signal : V0 . sin(phi) with V0=0.5V.

to discrimate a 500MHz bucket, we need to get dV < V0 dphi.

dphi = 2pi / 15 = 420 mrad => dV < 0.2 V => dV < +/- 0.1V

we used dV = +/- 0.02V but perharps we can relax the constraint.

we also reduced the RF scanning speed at 0.1V/s to let the system find the right phase when the system is slowly drifting.

368

Wed Oct 9 09:56:21 2024

Optimizing lock parameters for stable X-ray production

This morning, I wanted to test quickly if the Smaract motors can be used in open loop instead of closed loop or in piezo scan.

the goal is to do very fine steps without to much vibrations (like with piezo scan mode) but with the full motor range (the piezo scan mode has a very limited range).

=> the full range of the piezo scan mode is difficult to estimate because the measurement sensitivity is not good enough but around 5Hz.

=> 1350nm in closed loop is equivalent to ~ 10Hz => 135nm is equivalent to 1Hz => ok

Ronic Chiche wrote:

Today with Daniele and Alice, we operated to cavity.
we obtained 84kW for 33% of amplifier ratio.
we had to tune the CEP @ -565µm and the FP-cavity alignment.

then we locked properly the FP-cavity on the ring RF frequency.
we quite easily relock with the correct phase when we are loosing the lock.

the ThomX machine was running during these 2 locks, so we are ready for doing X-rays again.

Ronic Chiche wrote:

here are the (good) lock parameters used this morning.

for the RF/FPC lock, the 33MHz beating signal used to select the right bucket is 1Vpp
=> beating signal : V0 . sin(phi) with V0=0.5V.

to discrimate a 500MHz bucket, we need to get dV < V0 dphi.

dphi = 2pi / 15 = 420 mrad => dV < 0.2 V => dV < +/- 0.1V

we used dV = +/- 0.02V but perharps we can relax the constraint.

we also reduced the RF scanning speed at 0.1V/s to let the system find the right phase when the system is slowly drifting.

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

366

Thu Oct 3 16:38:03 2024

Optimizing lock parameters for stable X-ray production

Today with Daniele and Alice, we operated to cavity.
we obtained 84kW for 33% of amplifier ratio.
we had to tune the CEP @ -565µm and the FP-cavity alignment.

then we locked properly the FP-cavity on the ring RF frequency.
we quite easily relock with the correct phase when we are loosing the lock.

the ThomX machine was running during these 2 locks, so we are ready for doing X-rays again.

Ronic Chiche wrote:

here are the (good) lock parameters used this morning.

for the RF/FPC lock, the 33MHz beating signal used to select the right bucket is 1Vpp
=> beating signal : V0 . sin(phi) with V0=0.5V.

to discrimate a 500MHz bucket, we need to get dV < V0 dphi.

dphi = 2pi / 15 = 420 mrad => dV < 0.2 V => dV < +/- 0.1V

we used dV = +/- 0.02V but perharps we can relax the constraint.

we also reduced the RF scanning speed at 0.1V/s to let the system find the right phase when the system is slowly drifting.

365

Tue Sep 17 13:04:32 2024

Optimizing lock parameters for stable X-ray production

here are the (good) lock parameters used this morning.

for the RF/FPC lock, the 33MHz beating signal used to select the right bucket is 1Vpp
=> beating signal : V0 . sin(phi) with V0=0.5V.

to discrimate a 500MHz bucket, we need to get dV < V0 dphi.

dphi = 2pi / 15 = 420 mrad => dV < 0.2 V => dV < +/- 0.1V

we used dV = +/- 0.02V but perharps we can relax the constraint.

we also reduced the RF scanning speed at 0.1V/s to let the system find the right phase when the system is slowly drifting.

Attachment 1: Capture.JPG

364

Tue Sep 17 12:48:13 2024

Finding correct motors position and parameters to keep the lock during a move

this morning with Daniele, we did a quite long run with this motor position and it seems we don't lose the lock too much.

the motor positions are:

MOT.03 (M4): -186 500 steps

MOT.06 (M1): -797 500 steps

we got 85kW after CEP optimization and rough alignment optimization.

Ronic Chiche wrote:

this morning, I try to find a new region for MOT.03 and MOT.06 where we can move them without unlocking the cavity.

I started from the position:
MOT06 : ~ -785 000
MOT03 : ~ -200 000

and I do -10 000 steps (dz = 10k x 6nm = 60µm) at a time on both motors.
previously a good region for MOT.06 was -900 000 !

I moved also the laser cavity by 40µm to cancel the beating with the RF frequency.

MOT06 : ~ -795 000
MOT03 : ~ -191 000

Max power after optimazing the CEP ~ 65kW => I need to realign => 78kW
I need to increase the D parameter on the PID to compensate the (85kW / 78kW ratio).

I changed the MOT.03 and MOT.06 speed to 30steps/s => it seems a bit better.
but I still see some lock losses during a move.

.... to be continued...

363

Mon Sep 16 12:03:30 2024

Finding correct motors position and parameters to keep the lock during a move

this morning, I try to find a new region for MOT.03 and MOT.06 where we can move them without unlocking the cavity.

I started from the position:
MOT06 : ~ -785 000
MOT03 : ~ -200 000

and I do -10 000 steps (dz = 10k x 6nm = 60µm) at a time on both motors.
previously a good region for MOT.06 was -900 000 !

I moved also the laser cavity by 40µm to cancel the beating with the RF frequency.

MOT06 : ~ -795 000
MOT03 : ~ -191 000

Max power after optimazing the CEP ~ 65kW => I need to realign => 78kW
I need to increase the D parameter on the PID to compensate the (85kW / 78kW ratio).

I changed the MOT.03 and MOT.06 speed to 30steps/s => it seems a bit better.
but I still see some lock losses during a move.

.... to be continued...

362

Mon Sep 9 11:00:43 2024

lasers and optics | detectors and electronics | software

restarting CFP system after the long summer shutdown (RF section conditionning) and Alphanov amplifier issue

this morning, with Vincent :

- we added the 10Hz trigger to the CH2 on the remote scope (192.168.229.21) to check the synchronization at the right timing.
CH1 : 33MHz RING
CH2 : LINAC/RING synchro signal
CH3 : 500MHz RING
CH4 : 33MHz FPC

we successfully lock both laser on FPC (87kW for 33% amp ratio) and FPC on 500MHz RF.
we saw the result on the scope.
suprisingly, the FPC/RF lock seems much robust than before.

the only problem is the MOT.06 which make the lock being lost at almost every move.
one reason could be the rust on the mechanics... we can try to change the position of both plan mirror motors to work in a proper region.
before, it was working well at -900 000 steps on MOT.06, now it is -780 00.
it's a quite long travel...

end of this posts thread

Ronic Chiche wrote:

I changed a little bit the locking parameters (see picture) for the RF/FPC loop and it locked rapidely.

I asked Vincent to connect on the same scope the synchro signals to check if the FPC lock was OK => he connected 33MHz signals coming from the laser and from the 33MHz RF generator.
=> the signals are not locked even when the FPC seems to be locked to the RF.

=> it can be normal because he forgot to connect also the synchro trigger signal which gives the moment of synchronization of the machine... to be finished on Monday.

Ronic Chiche wrote:

now, the Ring RF frequency is set to 500.067MHz.

so the CFP/laser frequency should be 500.067MHz/15 = 33.3378MHz.

the frequency was set to 33.378MHz !!! => it explains the frequency shift only on the 33MHz beating => I corrected the frequency on the generator and informed Nicolas Delerue.

=> now, I can try to lock the CFP to the RF frequency.

Ronic Chiche wrote:

after redoing the alignment of the CVBG, we got back the initial power in the FPC (87kW)

now, I checked the RF locking signals on the 2nd oscilloscope.
I get a strange ratio between the 33MHz beating and the 500MHz beating signals.
beat @ 33MHz ~ 40kHz !
beat @ 500MHz ~ 700Hz !

maybe the 33MHz generator frequency is not matching the 500MHz RF frequency ?

Ronic Chiche wrote:

amplifier power measurement before the compressor CVBG.
we used a mirror in between the amplifier output and the compressor + a 2-mirror periscope to match the powermeter height.

amp ratio (%) power (W)

0                               0.7
10                             1.65
20                             13
30                             25
40                             37.7
50                             50.5
60                             62
70                             74
80                             86
90                             99
100                          110

we had an alarm @100% of amplifier ratio => the reason is not clear... maybe it's coming from a discrepency between some internal measurement and the expected value.
we checked the power after the alarm => still OK

conclusion, the amplifier seems to be OK... we need to redo the alignment of the compressor CVBG.

Ronic Chiche wrote:

After the summer power shutdown, I restarted all the equipements and got quickly ~80kW for 33% amplifier ratio with CEP optimization and without Alignment optimization.

CEP motor position : -506µm

Ronic Chiche wrote:

this morning with Daniele, we are measuring the amplifier power just before the FP-cavity.
Casemate temperature @19.5°C

@0% : 205mW
@10%: 755mW
@20%: 7.44W
@30%: 14.3W
@33%:16.3W
@40% : 20.3W
@50% : 24W
@60% : 26W

=> there is a power issue !!!

the normal casemate temperature should be in between 21 and 22°C.
cf this post (https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/133) to get previous amplifier power.

=> it seems we need to redo the compressor CVBG alignment !
first, we will check the amplifier power before the compressor.

Ronic Chiche wrote:

after doing some alignment (walking procedure on the Y axis), and CEP optimization, I got 83kW for 33% on the laser amplifier with a coupling of ~60%

=> we have to check the input power after the amplifier.

I adjusted the FP and laser cavity motors to have a small 33MHz detuning with the RF reference (~10 Hz of beating @ 33MHz)

pb : I don't see the 500MHz beating signal => to be checked

during the motion of the FP-cavity motors, I observed a systematic delock when moving MOT.06 on P1z and no delock with MOT.03 on P4z when I move by 10 steps.
Kevin checked that both IcePap controller have the same configuration and then, the problem is maybe coming from the rust observed on the mechanic.

Ronic Chiche wrote:

we had to move the laser cavity motor to find the resonances and change a lot the CEP.

the CEP motor is at -524.1µm

we got ~75kW in the FP cavity without alignment but with CEP optimization.

the coupling (the cyan color) is ~ 62% !

=> we need to do some alignment

Ronic Chiche wrote:

I refilled the chiller and the stabilized temperature is @ 25°C

we started the 3rd stage of the Alphanov amplifier at 30% => PD_OUT is fluctuating around 1-1.4W => it's not related to the real output power !

the photodiode connected to the scope CH2 is around 210mV @ 50ohms

we clearly see some small peak on the transmission signal (scope CH1) => we need to optimize the laser cavity length and the CEP

Ronic Chiche wrote:

temperature in the casemate ~ 19.5°C stable

this morning, I measured the power directly at the output of the fiber coupler (through the output fiber), after the strecher : ~5mW
then, I connected the EOM used for the PDH technic : ~2.5mW
then, I connected the fiber of the EOM to the Alphanov amplifier input fiber.

LAL Alphnov software :
PD_IN = 3.289mW
PD_PULSE = 33.372MHz

=> nothing to do ! :-)))

I switched ON the preamplifier (3rd stage @ 0%) => PD_Preamp2 = 152.44mW

361

Fri Sep 6 17:27:20 2024

mechanics | lasers and optics | detectors and electronics

20Hz oscillation in the locking between Laser and FP-cavity

could it be possible this 20Hz oscillations comes from anouncements in the bunker, puting the housing+table in vibration ?
(there are such anouncements during restricted access) => to be asked to Harold

Ronic Chiche wrote:

measure to be done next week to check the 20Hz noise on the laser amplifier signal:

- install a DET10 in reflection of the FP-cavity to get a high BW and measure the 500MHz harmonic.
- do the beating with the 500MHz Ring RF generator
- with the laser motor try to be close to the 500MHz Ring RF frequency => beating frequency below 1kHz
- send the beating signal to some RF spectrum analyzer to use its large dynamic range.

for example, with the Siglent RF spectrum analyzer, it is possible to detect easily a peak @ -96dBm <=> 3.5µV rms
so, one should be able to make the measurement @ 500MHz or even @ 33MHz even if the phase sensitivity is lower :

for example V0=100mV peak beating signal @ f0=33MHz should produce a 20Hz noise signal of:
dV ~ V0 * dphi = V0 * 2*pi*f0*dt = 200µV rms with jitter dt=10ps rms

Ronic Chiche wrote:

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)

Ronic Chiche wrote:

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...

Ronic Chiche wrote:

this afternoon, we did 2 tests to better understand this 20Hz oscillation:

- we locked the amplified laser directly to the 500MHz ring reference oscillator, without any intermediate locking to the FP-cavity => no change
the 20Hz oscillation is still present in the correction signal of the laser PZT.

- we switched OFF the controller of the hexapod => no change.

conclusion:
the 20Hz oscillation is coming from the laser cavity
or is coming from "outside" and could be measured, maybe at a higher level, with an external "noises & vibrations measurement system".

Ronic Chiche wrote:

this morning, we tried to find the origin of the 20Hz oscillation.

- we switched OFF the laser Smaract motors controller => no change

- then, we addionally disconnected the FP-cavity PZT cable from the Laselock (we put a charge of 1kohm) => no change

- then, we switched ON the laser Smaract motors controller and switched OFF the FP-cavity motors controllers => no change

in conclusion, we don't really know where this instabillity comes from.
the amplitude is roughly 1Vpp (when the oscillation is at its maximum) on the laser PZT <=> length oscillation of ~20nm pp

could it come :
- from the air cooling regulation with pressure variation ?
- from vibrations of the hexapod below the table ?
or is it from inside of the laser or FP cavities ?

see these posts for the first measurements on this issue: https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/257

360

Fri Sep 6 17:21:51 2024

lasers and optics | detectors and electronics | software

restarting CFP system after the long summer shutdown (RF section conditionning) and Alphanov amplifier issue

I changed a little bit the locking parameters (see picture) for the RF/FPC loop and it locked rapidely.

=> it can be normal because he forgot to connect also the synchro trigger signal which gives the moment of synchronization of the machine... to be finished on Monday.

Ronic Chiche wrote:

now, the Ring RF frequency is set to 500.067MHz.

so the CFP/laser frequency should be 500.067MHz/15 = 33.3378MHz.

the frequency was set to 33.378MHz !!! => it explains the frequency shift only on the 33MHz beating => I corrected the frequency on the generator and informed Nicolas Delerue.

=> now, I can try to lock the CFP to the RF frequency.

Ronic Chiche wrote:

after redoing the alignment of the CVBG, we got back the initial power in the FPC (87kW)

now, I checked the RF locking signals on the 2nd oscilloscope.
I get a strange ratio between the 33MHz beating and the 500MHz beating signals.
beat @ 33MHz ~ 40kHz !
beat @ 500MHz ~ 700Hz !

maybe the 33MHz generator frequency is not matching the 500MHz RF frequency ?

Ronic Chiche wrote:

amplifier power measurement before the compressor CVBG.
we used a mirror in between the amplifier output and the compressor + a 2-mirror periscope to match the powermeter height.

amp ratio (%) power (W)

conclusion, the amplifier seems to be OK... we need to redo the alignment of the compressor CVBG.

Ronic Chiche wrote:

After the summer power shutdown, I restarted all the equipements and got quickly ~80kW for 33% amplifier ratio with CEP optimization and without Alignment optimization.

CEP motor position : -506µm

Ronic Chiche wrote:

this morning with Daniele, we are measuring the amplifier power just before the FP-cavity.
Casemate temperature @19.5°C

@0% : 205mW
@10%: 755mW
@20%: 7.44W
@30%: 14.3W
@33%:16.3W
@40% : 20.3W
@50% : 24W
@60% : 26W

=> there is a power issue !!!

the normal casemate temperature should be in between 21 and 22°C.
cf this post (https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/133) to get previous amplifier power.

=> it seems we need to redo the compressor CVBG alignment !
first, we will check the amplifier power before the compressor.

Ronic Chiche wrote:

after doing some alignment (walking procedure on the Y axis), and CEP optimization, I got 83kW for 33% on the laser amplifier with a coupling of ~60%

=> we have to check the input power after the amplifier.

I adjusted the FP and laser cavity motors to have a small 33MHz detuning with the RF reference (~10 Hz of beating @ 33MHz)

pb : I don't see the 500MHz beating signal => to be checked

Ronic Chiche wrote:

we had to move the laser cavity motor to find the resonances and change a lot the CEP.

the CEP motor is at -524.1µm

we got ~75kW in the FP cavity without alignment but with CEP optimization.

the coupling (the cyan color) is ~ 62% !

=> we need to do some alignment

Ronic Chiche wrote:

I refilled the chiller and the stabilized temperature is @ 25°C

we started the 3rd stage of the Alphanov amplifier at 30% => PD_OUT is fluctuating around 1-1.4W => it's not related to the real output power !

the photodiode connected to the scope CH2 is around 210mV @ 50ohms

we clearly see some small peak on the transmission signal (scope CH1) => we need to optimize the laser cavity length and the CEP

Ronic Chiche wrote:

temperature in the casemate ~ 19.5°C stable

LAL Alphnov software :
PD_IN = 3.289mW
PD_PULSE = 33.372MHz

=> nothing to do ! :-)))

I switched ON the preamplifier (3rd stage @ 0%) => PD_Preamp2 = 152.44mW

Attachment 1: 20240906_161926.jpg

359

Fri Sep 6 15:20:20 2024

lasers and optics | detectors and electronics | software

restarting CFP system after the long summer shutdown (RF section conditionning) and Alphanov amplifier issue

now, the Ring RF frequency is set to 500.067MHz.

so the CFP/laser frequency should be 500.067MHz/15 = 33.3378MHz.

the frequency was set to 33.378MHz !!! => it explains the frequency shift only on the 33MHz beating => I corrected the frequency on the generator and informed Nicolas Delerue.

=> now, I can try to lock the CFP to the RF frequency.

Ronic Chiche wrote:

after redoing the alignment of the CVBG, we got back the initial power in the FPC (87kW)

now, I checked the RF locking signals on the 2nd oscilloscope.
I get a strange ratio between the 33MHz beating and the 500MHz beating signals.
beat @ 33MHz ~ 40kHz !
beat @ 500MHz ~ 700Hz !

maybe the 33MHz generator frequency is not matching the 500MHz RF frequency ?

Ronic Chiche wrote:

amplifier power measurement before the compressor CVBG.
we used a mirror in between the amplifier output and the compressor + a 2-mirror periscope to match the powermeter height.

amp ratio (%) power (W)

conclusion, the amplifier seems to be OK... we need to redo the alignment of the compressor CVBG.

Ronic Chiche wrote:

After the summer power shutdown, I restarted all the equipements and got quickly ~80kW for 33% amplifier ratio with CEP optimization and without Alignment optimization.

CEP motor position : -506µm

Ronic Chiche wrote:

this morning with Daniele, we are measuring the amplifier power just before the FP-cavity.
Casemate temperature @19.5°C

@0% : 205mW
@10%: 755mW
@20%: 7.44W
@30%: 14.3W
@33%:16.3W
@40% : 20.3W
@50% : 24W
@60% : 26W

=> there is a power issue !!!

the normal casemate temperature should be in between 21 and 22°C.
cf this post (https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/133) to get previous amplifier power.

=> it seems we need to redo the compressor CVBG alignment !
first, we will check the amplifier power before the compressor.

Ronic Chiche wrote:

after doing some alignment (walking procedure on the Y axis), and CEP optimization, I got 83kW for 33% on the laser amplifier with a coupling of ~60%

=> we have to check the input power after the amplifier.

I adjusted the FP and laser cavity motors to have a small 33MHz detuning with the RF reference (~10 Hz of beating @ 33MHz)

pb : I don't see the 500MHz beating signal => to be checked

Ronic Chiche wrote:

we had to move the laser cavity motor to find the resonances and change a lot the CEP.

the CEP motor is at -524.1µm

we got ~75kW in the FP cavity without alignment but with CEP optimization.

the coupling (the cyan color) is ~ 62% !

=> we need to do some alignment

Ronic Chiche wrote:

I refilled the chiller and the stabilized temperature is @ 25°C

we started the 3rd stage of the Alphanov amplifier at 30% => PD_OUT is fluctuating around 1-1.4W => it's not related to the real output power !

the photodiode connected to the scope CH2 is around 210mV @ 50ohms

we clearly see some small peak on the transmission signal (scope CH1) => we need to optimize the laser cavity length and the CEP

Ronic Chiche wrote:

temperature in the casemate ~ 19.5°C stable

LAL Alphnov software :
PD_IN = 3.289mW
PD_PULSE = 33.372MHz

=> nothing to do ! :-)))

I switched ON the preamplifier (3rd stage @ 0%) => PD_Preamp2 = 152.44mW

358

Fri Sep 6 12:10:51 2024

lasers and optics | detectors and electronics | software

restarting CFP system after the long summer shutdown (RF section conditionning) and Alphanov amplifier issue

after redoing the alignment of the CVBG, we got back the initial power in the FPC (87kW)

now, I checked the RF locking signals on the 2nd oscilloscope.
I get a strange ratio between the 33MHz beating and the 500MHz beating signals.
beat @ 33MHz ~ 40kHz !
beat @ 500MHz ~ 700Hz !

maybe the 33MHz generator frequency is not matching the 500MHz RF frequency ?

Ronic Chiche wrote:

amplifier power measurement before the compressor CVBG.
we used a mirror in between the amplifier output and the compressor + a 2-mirror periscope to match the powermeter height.

amp ratio (%) power (W)

conclusion, the amplifier seems to be OK... we need to redo the alignment of the compressor CVBG.

Ronic Chiche wrote:

After the summer power shutdown, I restarted all the equipements and got quickly ~80kW for 33% amplifier ratio with CEP optimization and without Alignment optimization.

CEP motor position : -506µm

Ronic Chiche wrote:

this morning with Daniele, we are measuring the amplifier power just before the FP-cavity.
Casemate temperature @19.5°C

@0% : 205mW
@10%: 755mW
@20%: 7.44W
@30%: 14.3W
@33%:16.3W
@40% : 20.3W
@50% : 24W
@60% : 26W

=> there is a power issue !!!

the normal casemate temperature should be in between 21 and 22°C.
cf this post (https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/133) to get previous amplifier power.

=> it seems we need to redo the compressor CVBG alignment !
first, we will check the amplifier power before the compressor.

Ronic Chiche wrote:

after doing some alignment (walking procedure on the Y axis), and CEP optimization, I got 83kW for 33% on the laser amplifier with a coupling of ~60%

=> we have to check the input power after the amplifier.

I adjusted the FP and laser cavity motors to have a small 33MHz detuning with the RF reference (~10 Hz of beating @ 33MHz)

pb : I don't see the 500MHz beating signal => to be checked

Ronic Chiche wrote:

we had to move the laser cavity motor to find the resonances and change a lot the CEP.

the CEP motor is at -524.1µm

we got ~75kW in the FP cavity without alignment but with CEP optimization.

the coupling (the cyan color) is ~ 62% !

=> we need to do some alignment

Ronic Chiche wrote:

I refilled the chiller and the stabilized temperature is @ 25°C

we started the 3rd stage of the Alphanov amplifier at 30% => PD_OUT is fluctuating around 1-1.4W => it's not related to the real output power !

the photodiode connected to the scope CH2 is around 210mV @ 50ohms

we clearly see some small peak on the transmission signal (scope CH1) => we need to optimize the laser cavity length and the CEP

Ronic Chiche wrote:

temperature in the casemate ~ 19.5°C stable

LAL Alphnov software :
PD_IN = 3.289mW
PD_PULSE = 33.372MHz

=> nothing to do ! :-)))

I switched ON the preamplifier (3rd stage @ 0%) => PD_Preamp2 = 152.44mW

357

Fri Sep 6 11:56:53 2024

lasers and optics | detectors and electronics

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/147

fixing CVBG issue

this morning with Daniele, we realigned the amplifier beam axis on the iris position.
it was pretty fast an easy => we got rapidely some resonance and we locked back to 87kW @33% amp ratio after tuning CEP and alignment.

we tried to play on the L-shape but we didn't a clear effect.

we also played on the 1/2 and 1/4 waveplates to tune the polarization.
we see very clearly the locked reflected signal changing without almost changing the transmission !

Aurélien suggested to slightly focusing the beam in the DET36 photodiode to have a better estimation of the coupling.
presently, the beam is clearly larger than the DET36 photodiode area which artificially increases the measured coupling.
(I cannot use a DET100 because I need 500MHz BW to get some RF signal for beating with the 500MHz reference signal).

I added a +75mm lens in front of the DET36 reflection signal photodiode => now, the beam is rougly 1-2mm diameter, centered on the DET36.
when I optimize the alignment and the CEP, I get 86-87kW in the CFP and 45% coupling => cf plot

end of the CVBG issue posts.

Ronic Chiche wrote:

1) this morning, I aligned to CFP to get back 82kW in the cavity for 33% of amplifier ratio.
thus, we can ajust the iris positions on the optical table to fix the CFP optical path before touching the CVBG.

2) we aligned the 5 iris. all of them were misaligned by 1-2mm, principaly vertically (maybe because we had to change the CFP frequency some time ago to match the new RF frequency?).

3) we opened the compressor box and found out the beam on the last mirror was really on the border => we have to move it.

=> we recorded several beam profiles at 20-70% of amplifier ratio (see images before realignement)
above 50% of amplifier ratio, the beam is deformed.

=> we realigned the 2 last mirrors of the compressor and compensate the axis displacement with the 2 inches injection mirrors at the output of the compressor to get back the telescope axis.
amplifier ratio (%)                 power after compressor (W)
0                                                 0.286
10                                               0.91
20                                               8.6
30                                              16.7
40                                              25.5
50                                              34.5
60                                              42.5
70                                              50.0
80                                              57.0
90                                              64.0
100                                            70.0

the power is back => OK ! :-)))

we took some images with the beam profiler at high power after the realignement (see images after realignement)

tomorrow, we have to realign the amplifier beam axis to the CFP axis.

Ronic Chiche wrote:

the CVBG of the compressor module seems to have an issue.

here is the plan of the work :

1) faire des résonances avec la CFP
2) ajuster les iris d'alignement du faisceau de l'ampli pour être sur de ne pas perdre la référence de l'axe de la CFP

3) installer des wedges haute puissance à proximité du compresseur + beam profiler
4) verifier la forme du faisceau au beam profiler en fonction de la puissance de l'ampli

5) ouvrir le boîtier du compresseur
6) prendre des images du boîtier à la caméra thermique en fonction de la puissance

7) éventuellement shunter le 2e CVBG avec un D shape et regarder le mode et caractéristique en sortie d'ampli.
8) ajuster l'injection dans le premier CVBG ou le second ou les deux en fonctions des résultats précédent

here are some useful logbook posts:

D-shape + images thermiques du compresseur qui peuvent servir de référence :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/150

post des images du faisceau en fonction de la puissance de l'ampli :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/135 (et autres posts du fil)

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/195 (et autres posts du fil)

Attachment 1: 20240906_151100.jpg

356

Thu Sep 5 09:53:10 2024

lasers and optics | detectors and electronics

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/147

fixing CVBG issue

2) we aligned the 5 iris. all of them were misaligned by 1-2mm, principaly vertically (maybe because we had to change the CFP frequency some time ago to match the new RF frequency?).

3) we opened the compressor box and found out the beam on the last mirror was really on the border => we have to move it.

=> we recorded several beam profiles at 20-70% of amplifier ratio (see images before realignement)
above 50% of amplifier ratio, the beam is deformed.

small power drop for ratio < 40% compared to previous measurements : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/133

the power is back => OK ! :-)))

we took some images with the beam profiler at high power after the realignement (see images after realignement)

tomorrow, we have to realign the amplifier beam axis to the CFP axis.

Ronic Chiche wrote:

the CVBG of the compressor module seems to have an issue.

here is the plan of the work :

1) faire des résonances avec la CFP
2) ajuster les iris d'alignement du faisceau de l'ampli pour être sur de ne pas perdre la référence de l'axe de la CFP

3) installer des wedges haute puissance à proximité du compresseur + beam profiler
4) verifier la forme du faisceau au beam profiler en fonction de la puissance de l'ampli

5) ouvrir le boîtier du compresseur
6) prendre des images du boîtier à la caméra thermique en fonction de la puissance

here are some useful logbook posts:

D-shape + images thermiques du compresseur qui peuvent servir de référence :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/150

post des images du faisceau en fonction de la puissance de l'ampli :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/135 (et autres posts du fil)

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/195 (et autres posts du fil)

Attachment 1: 70%_before_realign.png

Attachment 2: 60%_before_realign.png

Attachment 3: 50%_before_realign.png

Attachment 4: 40%_before_realign.png

Attachment 5: 30%_before_realign.png

Attachment 6: 20%_before_realign.png

Attachment 7: 80%_after_alignment.png

Attachment 8: 70%_after_alignment.png

Attachment 9: 60%_after_alignment.png

Attachment 10: 40%_after_alignment.png

Attachment 11: 30%_after_alignment.png

Attachment 12: 20%_after_alignment.png

355

Thu Sep 5 09:51:22 2024

lasers and optics | detectors and electronics

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/147

fixing CVBG issue

the CVBG of the compressor module seems to have an issue.

here is the plan of the work :

1) faire des résonances avec la CFP
2) ajuster les iris d'alignement du faisceau de l'ampli pour être sur de ne pas perdre la référence de l'axe de la CFP

3) installer des wedges haute puissance à proximité du compresseur + beam profiler
4) verifier la forme du faisceau au beam profiler en fonction de la puissance de l'ampli

5) ouvrir le boîtier du compresseur
6) prendre des images du boîtier à la caméra thermique en fonction de la puissance

here are some useful logbook posts:

D-shape + images thermiques du compresseur qui peuvent servir de référence :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/150

post des images du faisceau en fonction de la puissance de l'ampli :

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/135 (et autres posts du fil)

https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/195 (et autres posts du fil)

354

Fri Aug 30 17:59:01 2024

lasers and optics | detectors and electronics | software