<title>Development of a submillimeter-wave camera for the Atacama Submillimeter Telescope Experiment</title>

Abstract

ABSTRACT The Atacama Submillimeter Telescope Experiment (ASTE) is a Japanese development program for the large millimeter andsubmillimeter array (LMSA/ALMA). The new 10-rn submillimeter-wave telescope is a prototype telescope for the LMSAproject and to be installed in Chile in 2001 . The telescope will be equipped with submillimeter-wave SIS mixer receiversand a submillimeter-wave direct detector camera. The subrnillimeter-wave camera based on superconducting directdetectors (SIS photon detectors) are under development to realize very wide field observations in submillimeter-wave.Niobium tunneijunctions with low leakage current coupled to antenna structures can be sensitive submillimeter -wavedetectors when high quantum efficiency and low leakage current is realized. Inhomogeneous distributed junctions coupledto log-periodic antennas can be used to realize this. Input coupling of more than 50% is calculated using 5-element and 10-element inhomogeneous distributed junctions. With leakage current of less than 100 pA, noise equivalert power can be lessthan 10'6W/Hz°5 under shot noise limited operation. Submillimeter-wave camera of 100 pixels is now under design and willbe installed on ASTE 10-rn telescope in 2002 or later.Keywords : submillimeter-wave receivers, LMSA/ALMA, superconducting tunnel junctions, direct detectors, distributedjunctions, log-periodic antenna,