Kota Kasahara

Development of Superconducting Tunnel Junction detectors as a far-infrared photon-by-photon spectrometer for neutrino decay search

We present the development of Superconducting Tunnel Junction (STJ) detectors as a far-infrared single photon spectrometer, which is motivated for an application to a search for the radiative decay of the cosmic neutrino background (CνB). The photon energy spectrum from the radiative decays of CνB is expected to have a sharp edge at high energy end in a far-infrared region ranging from 14 meV to 25 meV (from 50 μm to 90 μm in wavelength) in the cosmic infrared background and the overwhelming infrared foreground from the zodiacal emission. Thus, the detector is required photon-by-photon detection with sufficiently high energy resolution, in order to gain the best signal-to-noise ratio as well as to identify the edge structure. The following two types of photon detectors are under consideration: an array of niobium/aluminum STJ (Nb/Al-STJ) pixels with a diffraction grating, and STJ using hafnium (Hf-STJ). Each Nb/Al-STJ pixel is required to be capable of detecting single photons in the far-infrared region, and the pixel array measures the photon wavelength spectrum which the diffraction grating creates. Hf-STJ is expected to achieve 2% energy resolution for single photon of 25 meV due to very small gap energy of hafnium.

Development of Superconducting Tunnel Junction Detectors as a far-infrared single photon detector for neutrino decay search

Yuji Takeuchi∗a †, Shin-Hong Kima, Kenichi Takemasaa, Kenji Kiuchia, Kazuki Nagataa, Kota Kasaharaa, Takuya Okudairaa, Tatsuya Ichimuraa, Masahiro Kanamarua, Kouya Moriuchia, Ren Senzakia, Hirokazu Ikedab, Shuji Matsuurab, Takehiko Wadab, Hirokazu Ishinoc, Atsuko Kibayashic, Satoru Mimad, Takuo Yoshidae, Shota Komurae, Keisuke Orikasae, Ryuta Hirosee, Yukihiro Katof, Masashi Hazumig, Yasuo Araig, Erik Rambergh, Jonghee Yooh, Mark Kozlovskyh, Paul Rubinovh, Dmitri Sergatskovh, Soo-Bong Kimi aUniversity of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8571, Japan bInstitute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara,

Development of superconducting tunnel junction photon detector on SOI preamplifier board to search for radiative decays of cosmic background neutrino

Kota Kasahara∗, Shin-Hong Kim, Yuji Takeuchi, Ren Senzaki, Kazuki Nagata, Takuya Okudaira, Masahiro Kanamaru, Tatsuya Ichimura, Koya Moriuchi, Kenji Kiuchi, Yasuo Arai1, Masashi Hazumi1, Hirokazu Ikeda2, Shuji Matsuura2, Takehiko Wada2, Satoru Mima3, Hirokazu Ishino4, Takuo Yoshida5, Yukihiro Kato6, Erik Ramberg7, Mark Kozlovsky7, Paul Ruvinov7, Dmitri Segratskov7 University of Tsukuba, Ibaraki 305-8571, Japan 1KEK, Ibaraki 305-0801, Japan 2JAXA ISAS, Kanagawa 252-5210, Japan 3RIKEN, Saitama 351-0198, Japan 4Okayama University, Okayama 700-8530, Japan 5University of Fukui, Fukui 910-8507, Japan 6Kinki University, Osaka 577-8502, Japan 7Fermi National Accelerator Laboratory, Illinois, 60510, US E-mail: kasahara@hep.px.tsukuba.ac.jp

Search for Cosmic Background Neutrino Decay

We present a proposal of an experiment for search for cosmic background neutrino decay. Due to the mass difference between neutrino generations, a heavier neutrino can decay into a lighter neutrino with a photon. Standard model predicts the neutrino lifetime is 10 44 year, while the current experimental lower limit of neutrino lifetime is 3 x10 12 year. However Left-Right symmetric model suggests much shorter neutrino lifetime down to 10 17 year in the shortest. If we assume a mass of the heaviest neutrino is 50 meV/c 2 , the expected photon energy at the neutrino rest frame is 25 meV. The energy spectrum of the photon from the cosmic background neutrino decay has a cutoff at this energy and a low energy tail due to a red shift effect as shown in Fig.1. Thus we propose an experiment to search for the photon emission from the decay of cosmic background neutrino by measuring the photon energy spectrum in the far infrared region with a superconducting tunneling junction (STJ) detector. We plan to perform a rocket experiment with the STJ detector in 2016 in the earliest, aiming at improving the neutrino lifetime limit by two order. We also aim at a 10-hour satellite experiment with 5 sensitivity for the neutrino lifetime of 10 17 year in further future [1]. [1] S. H. Kim, K. Takemasa, Y. Takeuchi and S. Matsuura, J. Phys. Soc. Jpn., 81 (2012) 024101S.

Development of Superconducting Tunnel Junction Photon Detectors with Cryogenic Preamplifier for COBAND Experiment

We present the status of the development of Superconducting Tunnel Junction (STJ) detector with the cryogenic preamplifier as far-infrared single photon detector for the COsmic BAckground Neutrino Decay search (COBAND) experiment. The photon energy spectrum from the radiative decay of the cosmic background neutrino is expected to have a sharp cutoff at high energy end in a far-infrared region ranging from 15 meV to 30 meV. 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 an array of Nb/Al-STJ pixels which can detect a single far-infrared photon delivered by a diffractive grating according to its wavelength. 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 around 0.3K. We have developed the Nb/Al-STJ with the SOI cryogenic preamplifier and have tested the detector performance around 0.3K.

Development of Superconducting Tunnel Junction Detector Using Hafnium for COBAND Experiment

We present the development of a Superconducting Tunnel Junction detector using hafnium (Hf-STJ) as a far infrared single photon detector for COsmic BAckground Neutrino Decay search (COBAND) experiment. The photon energy spectrum from the decay of cosmic background neutrino is expected to have a sharp edge at the high energy end in a far-infrared region ranging from 14–25 meV in the cosmic infrared background and the overwhelming infrared foreground from the zodiacal emission. We are developing a Hf-STJ which is expected to have 2% energy resolution for a single photon of 25 meV. We have successfully produced a superconductor-insulator-superconductor structure using Hf. However, it is found to suffer from a large leakage current and needs modification of the Hf-STJ to reduce it. We have developed two new types of Hf-STJ: Hf-STJ with an Al layer and Hf-STJ with a new sputtering condition. The leakage current density of two new types of Hf-STJ becomes 16 times smaller than the old Hf-STJ and obtained a response to the visible light. Because of its large leakage current, further optimization is underway.