Modeling of Planck-high frequency instrument bolometers using non-linear effects in the thermometers

The Planck satellite, which is planned to be launched in 2007, is dedicated to surveying the Cosmic Microwave Background (CMB) to a high precision. Aboard this mission, the High-Frequency Instrument (HFI) will use 52 NTD Ge spiderweb bolometers made by Caltech-JPL and cooled to 100 mK by a dilution cooler. In this paper, we present a model of these detectors that includes non-linear effects seen in NTD Ge thermometers: electron–phonon decoupling and electrical field effect. We show that this model leads to consider only electrical field effect. Furthermore, the optical characterization of the HFI bolometers clearly shows a non-ideal behavior that is explained by non-linear effects in the thermometer. We finally show that these effects have to be taken into account for optimized CMB observations and to fully understand the physics of semi-conducting bolometers.