temperature @ 21.9°C
48.5kW inside CFP for 30% amplifier ratio
Frep Laser motor = 123.4µm
CEP motor = -67.8µm
below the image of the relative voltage range between CFP PZT (pink) and laser PZT (green).
the CFP PZT is driven by 10x the voltage range showed by the scope (0-100V HV output and 0-10V monitor on the Laselock)
one can see on the scope that the relative range of both PZT voltage range is roughly the same which means that the real CFP PZT sensitivity is 10x smaller than the Laser PZT sensitivity.
as the CFP PZT is driven by 0-100V and the Laser PZT is driven by 0-10V voltages, they have approximately the same range which is ~200nm (calibrated with the Laser motor in closed loop mode).
in a previous email, the CFP PZT should be given with a sensitivty of about 4nm/V => 400nm/100V of length range => 800nm/100V of CFP roundtrip range => 80e-9/100V of relative sensitivity => 40Hz of frequency peak-peak range for 500MHz carrier frequency.
there is a discrepancy between measurements (~10Hz peak-peak range for 500MHz carrier) and expected value !
| Ronic Chiche wrote: |
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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.
(maybe I let the terminal window open with all the apps and someone tried to unlog by removing them ?)
the cavity height was pretty misaligned.
after a rough alignment, the power inside the cavity was back at 49kW for 30% amplifier ratio.
the CEP motor needs to be adjusted a lot during the cavity heating process
| Ronic Chiche wrote: |
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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: |
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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.
| Ronic Chiche wrote: |
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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:
one looses the lock only when one needs to use the Smaract motors to follow the long temperature drifts.
several elements of the ThomX machine have been powered ON progressively during the lock without any lock perturbation excepting for a very short time when switching ON the RF cavity (to be confirmed) and when one tried to inject electrons into the ring (loss of the electrons after few turns only)... but it's not very clear. the lock is still stable but some time one sees a lock loss without "reason"... could it be the electron loss or some bad compensation of the noise due to feedback, it's hard to say.
at the end of the day, I had to realign the FP-cavity injection and change the CEP more often than in the morning,
and surprisingly, the intra-cavity power drops a little bit at the begining of the lock (~50kW) and after some tenth of seconds (=> ~47-48kW).
it is not so much but it is very repeatable at each try.
I tried to optimize the CEP, the injection alignment, the PID parameters => it helps but at the end, I still have this slow power drop of few kW over tenth of seconds that I didn't see at the begining of the day... to be investigated.
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