Finding correct motors position and parameters to keep the lock during a move, posted by Ronic Chiche at ThomX igloo about mechanics
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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 |
Fiber injection and onefive output power, posted by Loïc Amoudry at Optical room about lasers and optics
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Fiber injection is finished with the new ThomX stretching CVBG in double pass (+50% injection power compared to K-BOX CVBG in simple pass).
- Output Onefive: 27 mW
- After Onefive + lambda/2 + isolator: 25.8 mW |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, we tried to lock the FP cavity with the Smaract motors ON (with option -LV).
we know the Smaract controllers produce some noise and the lock is very bad or impossible when the controller in ON (whatever the displacement mode
is : closed or open loop, or piezo scan). |
Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics 
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today, after the several unsuccessful attempt yesterday to get an improvement in the lock,
we decided to "rebuild" the error signal electronics block by block and step by step :
the scheme is basically : |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this afternoon, we tried to better understand how to drive properly the EOM to kill high frequency noise.
we locked to laser on the FP-cavity as usual.
then we injected a 0-10V square signal on the laser EOM @ 1KHz (with fast rise and fall times ~ 10ns) |
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Fast feedback loop between laser and FP cavity, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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I copy the post about Fast Feedback loop : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/265
This morning,
- I installed the fast feedback loop. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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 |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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 |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this morning, the chiller was in error and I had to restart it.
the air temperature is around 21°C. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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... |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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: |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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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. |
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FP-cavity lock survey during the Linac section changing operation, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today with Daniele, we disconnected the EOM to increase the injected power of the amplifier, we were at 4.8mW but we still have the "bad sequence"
error => email to Guillaume
we tried also several time again, to stop and restart the amplifier, but it didn't help. |
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FP-cavity inside power sensitivity, posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning I monitored the frequency shift between the FP-cavity frequency (the laser is locked on it) and the RF reference frequency @ 500MHz,
during the warm-up time, for 50kW stored in the cavity (the recording started ~ 9h20).
one observes on fig.1 a simple exponential behavior with 500Hz frequency shift @500MHz (equivalent to ~ 10µm) for 50kW stored. |
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FP-cavity FSR shift, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, to match the ring frequency at 500.25MHz (15th laser harmonic), we did a frequency shift on the laser using the Smaract motors (not too fast,
~2µm/s, to prevent laser modelock loss)
and we "followed" this shift on the FP-cavity using the FP-cavity motors. |
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FP cavity mode axis change and Finesse measurement, posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning with Manar, we did a cavity mode axis change.
we checked the cavity mode centroid position on the beam profiler (placed behind P4) and changed it by roughly 1mm on the X-axis and by 500µm
on the Y-axis. |
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FP cavity alignment , posted by Manar Amer at ThomX igloo about lasers and optics
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Note the direction of injection is M1 - M2 - M3 - M4
P1 - S2 - S3 - P4 |