K. Kiuchi

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

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.

GroundBIRD: observations of CMB polarization with fast scan modulation and MKIDs

Polarized patterns in the cosmic microwave background (CMB) radiation contains rich knowledge for early stage of the universe. In particular their odd-parity patterns at large angular scale (> 1°), primordial B-modes, are smoking-gun evidence for the cosmic inflation. The GroundBIRD experiment aims to detect these B-modes with a ground-based apparatus that includes several novel devices: a high-speed rotational scan system, cold optics, and microwave kinetic inductance detectors (MKIDs). We plan to start observations in the Canary Islands in 2017. In this paper, we present the status of the development of our instruments. We established an environment that allows operation of our MKIDs in an optical configuration, in which the MKIDs observe radiations from the outside of the telescope aperture. We have also constructed MKID prototypes, and we are testing them in the optical configuration.