Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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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: |
Ring frequency / Laser "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 
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temperature stable around 20.8°C
today, the equivalent Smaract position corresponding to the 500.25MHz ring frequency is +158.4µm on MCS-1/ch0 (closed loop mode)
it is very difficult to maintain both loops in the same time as soon as it is needed to move one motor (CFP or Laser) because of the one element |
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M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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. |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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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. |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature since we moved to temperature probe (jump at the beginning of the plot) below the ring on a metallic base.
Ronic
Chiche wrote:
as the temperature is back to a normal value ~ 20.8°C, the injected |
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Ring frequency / Laser "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature stable around 21.7°C
today, the equivalent Smaract position corresponding to the 500.25MHz ring frequency is +147µm on MCS-1/ch0 (closed loop mode)
Ronic |
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M4 motor using icepap controller and jive/Atkpanel IHM, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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 |
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bunker temperature curve, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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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. |
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Laser / FP-cavity "day by day" locking, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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temperature @ 21.9°C
48.5kW inside CFP for 30% amplifier ratio
Frep Laser motor = 123.4µm |
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Temperature control of the FP-cavity length, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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as the CFP motors displacements induce a cavity unlock, we try to change the cavity length by changing the temperature of elment of the cavity.
yesterday, we tried to put a "heating cable" borrowed to the vacuum group to change the temperature of one bellows between the FP-cavity
and the electron ring. |
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Temperature control of the Laser length with the inside Peltier, posted by Ronic Chiche at ThomX igloo about lasers and optics
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bunker temperature @ 22.5°C
today, Sebastien Pitrel improved its python software to manually control the laser peltier. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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 => -/+ |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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 |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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. |
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Smaract motors parameters and controller, posted by Ronic Chiche at ThomX igloo about mechanics | detectors and electronics
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current Smaract motors parameters :
- Closed loop Max frequency : 5000
- Signal Amplitude threshold : 2047 |
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Temperature control of the FP-cavity length, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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several days ago, we installed a heating cable around the output flange (close to the X-hutch) of the FP-cavity vessel.
we are able to heat this cable by applying a DC voltage coming from 2 DC voltage supplies in serie (2 devices with 2x 0-30V / 3A => 0-120V /
3A). |
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Long term lock of Laser-FP cavity-RF reference, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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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 |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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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 |