*Speaker : Prof. Shinhong Kim (University of Tsukuba)
*Abstract : We present the status of the COsmic BAckground Neutrino Decay search(COBAND) experiment and the development of Superconducting Tunnel Junction (STJ) detector with the cryogenic preamplifier as a far-infrared single photon detector for the COBAND experiment. The photon energy spectrum from the radiative decay of cosmic background neutrino is expected to have a sharp cutoff at high energy end in a far-infrared region ranging from 15meV to 30meV. The detector is required to measure an individual photon energy with a sufficient energy resolution less than 2% for identifying the cutoff structure, and to be designed for a rocket or satellite experiment.
We develop a combination of the diffraction grating and the array of Nb/Al-STJ pixels, where each Nb/Al-STJ pixel can detect a single far-infrared photon delivered by the grating. An amplifier is required to have a level of 10 electron equivalent-noise for Nb/Al-STJ. To achieve high signal-to-noise ratio of the STJ, we use a preamplifier made with the Silicon on Insulator (SOI) technique that can be operated at low temperature around 0.3K.
We also develop Hf-STJ as a micro-calorimeter which is planned to be used in the future satellite experiment. The present status of the development of the STJ detector development is reported in more detail.