Alphanov amplifier beam profile measurement, posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning with Manar,
- we fixed the chiller problem (+/-2°C fluctuation around the set temperature value = 25°C).
we opened and closed several times the water valve of the primary circuit to remove air bubles => no effect on the temperature variations. |
CW laser installation and cleaning, posted by Ronic Chiche at ThomX igloo about lasers and optics 
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This morning with Manar, in order to prepare the installation of the news FP cavity mirrors,
- we installed the Koheras below the optical table
- we put a fiber prolongator at the end of the Koheras fiber and we put a mounted collimator at the end of the fiber. |
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CW laser installation and cleaning, posted by Ronic Chiche at ThomX igloo about lasers and optics
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This morning with Ronic , in preparation for the mirror installation, we removed additional mechanics and cables from the table.
We organized and cleaned the permanently installed cables on the table away from the area of the cavity opening.
We opened the two top vents and left the shutters open to circulate clean air , (note the shutters surrounding the laser and amplifier are half |
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New Mirrors from LMA _ Images, posted by Manar Amer at Optical room about lasers and optics
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Today we tested a mirror from one patch
image is for the front face of the mirror
PowerPoint has more details about the images |
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33MHz laser SN2439 back to Orsay, posted by Ronic Chiche at Optical room about lasers and optics
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As the general local network for the FP-cavity devices is 192.168.xxx.xxx, I changed the IP adress of the smaract laser motors (Frep and CEP) controller.
For that, I used the embedded web server as described in the manual in attached file.
the new adresses are : |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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the last tries to lock the 33MHz + amplifier to the 30k Finesse FP-cavity were unsuccessful.
during a laser Frep scan using the Laselock, one observes that the main cavity resonance is not able to stay inside the PZT scan range from one
scan to another (500ms-1s period) |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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finding the right modulation/demodulation PDH phase is very difficult on the main resonance because the we get non stationnary signals with a lot of
oscillations.
changing the phase, in this condition, does not really change the error signal. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today with Daniele, we locked easily (but with a noisy lock) on the secundary resonance and we tried to lock on the main resonance (with very low coupling
~10% which mean a CEP ~Pi)
the lock was possible but was very noisy. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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After removing the 2 generators from the optical table, the lock is much more stable and now, it is possible to lock on the main resonance with a poor
CEP but with quite good stability.
the coupling is still very low ~ 5% for that CEP but if one improves it (CEP ->0), using the laser double-wedge motor, one clearly sees an improvement |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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this morning, I tested the laser+amplifier @ 30% lock on the FP cavity with and without Smaract motors.
I recorded the PDH error signal during a lock:
- blue : with Smaract motors controller powered ON but motors are stopped |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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I checked with the Matlab code below the CEP detuning effect (2nm sech² spectrum... not exactly the same as in ThomX)
@ CEP = 0 => coupling = 100% and Gcav = 10.5k
if all the coupling loss comes from the CEP detuning effect : |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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we checked yesterday morning the real input power @ 30% for the amp => it is 16W in agreement with the previously measured values
Ronic
Chiche wrote:
I checked with the Matlab code below the CEP detuning effect (2nm |
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First X rays and FP-cavity mode and electron beam waists size @ IP, posted by Ronic Chiche at ThomX igloo about lasers and optics
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on friday 23/06 afternoon, after scanning the hexapod z-axis, we observed a cut of the power stored in the FP-cavity (with constant input power/coupling)
at both ends of the scan, due to the losses of the beam-pipe aperture.
we placed the hexapod exactly in the middle of this range ~ z=-1.68 mm (which is not the middle of the maximum range of the hexapod), we opened |
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Incoming laser beam power issue, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, we observed on the photodiode used in reflexion of the cavity, that its voltage level stops increasing after 50% of power for the laser amplifier
when the cavity is not locked (the FP-cavity is just a reflective mirror).
the photodiode itself is not saturated (low power sent after a wedge and an absorbing filter) and the reading is done on 50 ohms. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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Today, we locked the cavity with input power @ 30% for the amp => we got 40kW with only 30% of coupling (and a bad lock => we could have more power
inside cavity).
P@30% = 16W |
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Equipments shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics
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on the August 30rd and 31th, a global power shutdown was forseen for ThomX.
to prevent damage on equipments, I switched off all of them (and disconnected power cables from the wall plugs).
yesterday, after the week-end, all the equipments have been restarted and the cavity as been locked properly. |
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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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Smaract controller remplacement, posted by Ronic Chiche at ThomX igloo about lasers and optics
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previously, we were using a spare Smaract MCS controller to drive the Onefive linear stages (without -LV -low vibration- option and
using Ethernet),
during the repair of the initial MCS controller with -LV option. |
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Onefive laser modelock and Smaract CEP controller, posted by Ronic Chiche at ThomX igloo about lasers and optics
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today, during an attempt in improving the CEP with the Smaract controller CH2, we lost the laser modelock.
at this point, we decided to reference the Smaract CH2 for CEP :
now, 0 mm is roughly the middle of the motor range. |
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33MHz oscillator + Alphanov amplifier lock, posted by Ronic Chiche at ThomX igloo about lasers and optics
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redoing the PDH error signal scheme with discrete components is more flexible and it is easier to check the signal/noise ratio.
now, we are able to get a quite clean lock only with the PZT correction (w/o fast feedback correction using the EOM) even with both motors controllers
ON (cavity and laser). |