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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today, I removed one of the DC voltage supply (as with 30V, we are already able to 30°C on the heating cable).
the remaining DC voltage supply is configured in series (2x30V = 60V max) and is at the IP address : 192.168.1.101
Ronic |
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, 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. |
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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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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. |
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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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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this afternoon, I started the heating cable after the warm-up of the FP-cavity :
14h20 : start to fill 50kW in the cavity
15h : start of the heating cable @10V (2x 5V) (iteration 2300) |
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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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last friday, I locked the cavity and then, switched ON the heating cable after waiting the cavity reaches a steady state in frequency drift : see the
figure.
blue : temperature of the probe on the heating cable |
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New mirrors batch informations, posted by Ronic Chiche at ThomX igloo about lasers and optics
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| the 2 files describe the specfications for the16 mirrors ordered (4 for ThomX + spare, 4 for SBOX + spare) and the measurements made by the LMA. |
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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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on last tuesday, I did a long-term measurement of the frequency drift when the heating cable is powered ON at 20V (2x 10V) @ t=0mn.
the freqeuncy drift (between the laser, locked in open loop on the FP-cavity, and the RF reference oscillator) acquisition was made by the National
Instrument software. |
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Strecher and fiber injection alignment, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, the Alphanov amplifier stopped because of the too low injected power : ~2.5mW (measured by the Alphanov software)
it was still working at ~2.7mW.
normally, the injected power is ~3.1mW (equivalent to 6.2mW measured directly at the fiber output). |
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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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today with Fatematuj, we did a long-term frequency drift measurement between the FP-cavity loaded with 50kW and the RF reference frequency... and without
any other thermal source (no heating cable !)
we had a small lock loss at t ~ 120mn. |
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Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I shut off all the equipements (especially the computer) except the ones powered by the UPS : laser controller, laser peltier controller,
laser motors controller.
and I disconnected the cables from the power plugs of the wall (to prevent any possible overvoltage). |
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Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this afternoon, I checked visually what happens when the AC power of the UPS is broken down => the laser controller has still its "emission"
button ON... no AC interruption.
so, I guess the UPS switched properly the output AC line from the input AC line to the internal batteries. |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I plugged back the 4 power cables which supply all the equipments.
all the equipments have restarted without problem, but the shutter of the laser amplifier needs a ThomX safety system grant to let the beam propagate
to the cavity... |
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Variable focal lens validation, posted by Ronic Chiche at ThomX igloo about lasers and optics
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we plan to use Electrically Tunable Lenses EL-10-30-C NIR to build the ThomX telescope but they need to be compatible with the powerful laser beam.
for CW regime, on the datasheet (see attached file), the optical damage threshold is 10 kW/cm².
with 70W laser power and 1mm² beam surface (which is much smaller than the real beam size), we are at 7kW/cm². |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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the laser coupled into the amplifier is still measured at ~3mW at the input, on the Alphanov software, once the Amp stage are started at 0% of power
ratio.
this afternoon, Kevin restarted the 3rd safety system of ThomX to grant the opening of the beam shutter => now the shutter can be opened. |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I set the Ring frequency at 500.25MHz and after switching ON the power supply of the amplifiers for the RF signal coming from the laser,
I saw the beating frequency (between ring RF and laser harmonic frerquencies at 500.25MHz) that I canceled, playing with the Smaract motor.
Now, I need to adjust the FP-cavity length to follow the laser cavity length but the IcePap DS (controlling the FP-cavity motor) freezes too |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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on last friday (12/01/2024), the IcePap DS issue was solved and I was able to control the FP-cavity motors properly.
I was able to quickly lock either the laser on the FP-cavity and the FP-cavity on the RF reference as before.
then, we can close these posts on restarting the equipments after the Christmas shutdown |
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33MHz (FP-cavity vs RF) phase stability, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this morning, with Vincent Chaumat, we made a beating (phase detection) between the laser 33MHz and the 33MHz coming from the Rigol generator locked
by the 10MHz link onto the 500MHz ring generator.
once the laser and the FP-cavity are locked on the RF reference, the 33MHz phase detection is stabilized and confirm the laser/FP-cavity lock |
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Adding one photodiode in reflection, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, I added a DET36 photodiode in reflection (I used a thin beam splitter) to better measure the coupling over the full beam size.
this DET36 photodiode is sent to the "laser locking" oscilloscope with the other signals :
CH1 :transmission |
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controller M1 & M4 (plan mirrors) with IcePap controllers, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | cabling
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previously, we have connected motor M4 with an IcePap controller.
see this post : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/278
due to the backlash behavior of the FP-cavity motors, it is impossible to work in both directions on one motor when the FP-cavity is locked. |