Result from a step function test.
At ~1.5 h, I changed the temperature setpoint from 33.5 to 34.5 C, so the voltage supply to the heater rose up. It reached at 1.7 V and constant because the perl script limited the voltage at that value for preventing any mishap. The can reached the equilibrium first, in ~ 5.5 hrs after the setpoint was changed. Then the cavity's temperature reached the equilibrium, ~ 3 hrs later. The stack temperature had not reached equilibrium yet.
Heat transfer mechanism that heats up the cavity seems unlikely to be conduction from can-> stack -> suspension-> cavity. If that were the case, the stack would reach equilibrium before the cavity.
I'm repeating the experiment, but this time I turn off the thermal PID feedback of the can temperature, and make a step down in the heater voltage supply, and keep the laser locked to the cavity so that we can read the continuous value from SLOWDC.
*I'm sure I made this entry last night. Where did it go?