Development of TES Bolometer Camera for ASTE Telescope: I. Bolometer Design

We are developing transition edge sensor (TES) bolometer arrays for a new multicolor millimeter-submillimeter camera for the Atacama Submillimeter Telescope Experiment located at an altitude of 4860 m in the Atacama Desert. Our goal is to realize high sensitivity and wideband multicolor observations for estimating the photometric redshift of dusty star-forming distant galaxies, and also for precise measurement of properties of clusters of galaxies through the Sunyaev-Zel'dovich effect. We will have three bands with center wavelengths of 1.1, 0.85, and 0.45 mm, which correspond to 270, 350, and 670 GHz in frequency. We discuss the optimization of a feedhorn coupled spiderweb transition edge sensor bolometer design for the 270 and 350 GHz bands. Because the optical loading increases with shorter wavelength, large saturation power and thermal conductivity are required, which in turn require large heat capacity to avoid electrothermal oscillation. The heat capacity is increased by adding a large gold structure at the center of the spiderweb, which at the same time acts as a reflector and degrades the bandwidth performance. By detailed electromagnetic simulation, we have overcome this drawback by optimizing the frontshort distance.