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Dear all,
We now figured out that the problem is coming from the temperature
controller (Oko-Lab). This periodicity of 66 sec seems to be the exact time
that the temperature/CO2 controller box takes to have the fan ON, then OFF,
then ON again. So every minute, the temperature is checked and if a
variation is detected, the chamber receives warm air (at about 48°C). And
somehow, this seems to influence the intensity/laser during the imaging. If
the controller box is turned off, the oscillations immediately stop. We
figured out that the user actually forgot a few times to fill in the water
dish containing the probe, and then the temperature controller was trying to
compensate. Once the probe was reimmerged and the system fully
re-equilibrated, I could not observe the oscillations anymore.
I contacted Oko-Lab while we were trying to figure out the problem, and they
have been very responsive. They pointed out a couple more things but the
probe not being in water still seems to be the main culprit.
Best Regards,
Alexia