Reference cavity temperature stabilization

I finally calibrated all the temperature sensors that are mounted on the reference cavity and switched the heater back on. It is still running with a digital control loop (Dinco) that has a pole at 100mHz. As for iLIGO we use the average of four AD590s as in loop sensors (Refcav_Temp) and control the heater with a HP power supply (also from iLIGO). The operating temperature is 38.8degC and roughly 18W are necessary to keep it at this temperature and the reference cavity is insulated with yellow painted styrofoam (iLIGO). Another AD590 is used as out of loop sensor.
The measurement is showing a 1 day trend of the ambient temperature (L1:PSL-OSC_PD_BP_AC), the in loop sensor (L1:PSL_ISS_REFCAV_TEMP), the out of loop sensor (L1:PSL-OSC_PD_INT_AC) all calibrated in Kelvin and the control signal to the heater (L1:PSL-ISS_REFCAV_HEATEROUT) in counts. During the measurement the HEPAs and AC were off and the makeup air running at 100%. The peak to peak fluctuations are between 10mK (in loop) and 100mK (out of loop).