Composite bolometer based on high temperature superconducting Bi2Sr2CaCu2O8+x crystals for application in the far infrared

We discuss the feasibility of a new type of high temperature superconducting bolometer operating in the sub-millimeter region (A > 300pm ) of the spectrum in the temperature range 80K + 100K. We use the sharp resistive transition of BizS~aCaCuzO~+, superconducting single crystals as sensitive thermometer. The sensor is thermally coupled to a thin diamond substrate covered on the back side with a bismuth flm that performs the absorbtion of the radiation. Such a detector should have large sensitive area and short time response due to the low heat capacity of both crystal and substrate. We describe the results of the electrical bolometric characterization, noise measurements and optical calibration carried out on the first prototype and use them to predict the Noise Equivalent Power (NEP) of a well designed detector.