Development of submillimeter-wave camera for atacama submillimeter telescope experiment

Submillimeter-wave focal plane arrays based on superconducting direct detec tors are designed to be used on a new 10-m submillimeter-wave telescope in Chile. Niobium tunnel junctions with low leakage current coupled to antenna structures can be sensitive submillimeter- wave direct detectors when high quantum efficiency and low leakage current are realized. Inhomogeneous dis tributed junctions coupled to log-periodic antennas can be used to realize this. Input coupling of better than 50% is calculated with a bandwidth of m ore than 60 GHz using low current density inhomogeneous distributed junctio ns. Their measured leakage current of 5 pA and their shot-noise limited ope ration suggests that noise equivalent power of less than 10(-17)W/Hz(0.5) a t operating temperature of 0.9 K could be achieved.