Hidden photon CDM search at Tokyo

We report on a search for hidden photon cold dark matter (HP CDM) using a novel technique with a dish antenna. We constructed two independent apparatus: one is aiming at the detection of the HP with a mass of $\sim\,\rm{eV}$ which employs optical instruments, and the other is for a mass of $\sim5\times10^{-5}\, \rm{eV}$ utilizing a commercially available parabolic antenna facing on a plane reflector. From the result of the measurements, we found no evidence for the existence of HP CDM and set upper limits on the photon-HP mixing parameter $\chi$.Comment: Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs, Zaragoza, June 22 to 26, 201

Direct search for solar axions by using strong magnetic field and X-ray detectors

We have searched for axions which could be produced in the solar core by exploiting their conversion to X rays in a strong laboratory magnetic field. The signature of the solar axion is an increase in the rate of the X rays detected in a magnetic helioscope when the sun is within its acceptance. From the absence of such a signal we set a 95% confidence level limit on the axion coupling to two photons $g_{a\gamma\gamma}\equiv 1/M < 6.0\times 10^{-10}$ GeV$^{-1}$, provided the axion mass $m_a<0.03$ eV. The limit on the coupling is factor 4.5 more stringent than the recent experimental result. This is the first experiment whose sensitivity to $g_{a\gamma\gamma}$ is higher than the limit constrained by the solar age consideration.Comment: 11 pages, REVTeX, 4 eps figures included, submitted to PL

東京アクシオンヘリオスコープ装置による太陽アクシオンの探索

学位の種別: 論文博士審査委員会委員 : （主査）東京大学教授 駒宮 幸男, 東京大学教授 宮下 精二, 東京大学教授 森 俊則, 東京大学准教授 川本 辰男, 東京大学教授 塩澤 真人University of Tokyo(東京大学

A liquid-helium cooled large-area silicon PIN photodiode x-ray detector

An x-ray detector using a liquid-helium cooled large-area silicon PIN photodiode has been developed along with a tailor-made charge sensitive preamplifier whose first-stage JFET has been cooled. The operating temperature of the JFET has been varied separately and optimized. The x- and $\gamma$-ray energy spectra for an \nuc{241}{Am} source have been measured with the photodiode operated at 13 K. An energy resolution of 1.60 keV (FWHM) has been obtained for 60-keV $\gamma$ rays and 1.30 keV (FWHM) for the pulser. The energy threshold could be set as low as 3 keV. It has been shown that a silicon PIN photodiode serves as a low-cost excellent x-ray detector which covers large area at 13 K.Comment: 6 pages, and 3 figures, Elsevier macros elsart.sty and elsart12.sty are neede

Trace Element Analysis of Potassium by Resonance Ionization Mass Spectrometry

A simple resonance ionization mass spectrometer is built with a Quadrupole Mass Spectrometer (QMS) and two laser diodes aiming at trace analysis of potassium. The overall detection efficiency is estimated comparing the yields of resonance ionization and electron-impact ionization in the same QMS. A clear discrimination of $^{39}\rm K$, $^{40}\rm K$ and $^{41}\rm K$ is demonstrated with a help of isotope shifts of the atomic levels.Comment: 14 pages, 9 figures, submitted to JJA

Submucosal Endoscopy, a New Era of Pure Natural Orifice Translumenal Endoscopic Surgery (NOTES)

Natural orifice translumenal endoscopic surgery (NOTES) involves the intentional perforation of the viscera with an endoscope to access the abdominal cavity and perform an intraabdominal operation. In a brief time period, NOTES has been shown to be feasible in laboratory animal and human studies. Easy access to the peritoneal cavity and complete gastric closure should be secured before NOTES can be recommended as an acceptable alternative in clinical practice. The concept of submucosal endoscopy has been introduced as a solution to overcome these two primary barriers to human NOTES application. Its offset entry/exit access method effectively prevents contamination and allows the rapid closure of the entry site with a simple mucosal apposition. In addition, it could be used as an endoscopic working space for various submucosal conditions. Herein, the detailed procedures, laboratory results and human application of the submucosal endoscopy will be reviewed

Measurements of anisotropic scintillation efficiency for carbon recoils in a stilbene crystal for dark matter detection

It is known that scintillation efficiency of organic single crystals depends on the direction of nuclear recoils relative to crystallographic axes. This property could be applied to the directional WIMP dark matter detector. The scintillation efficiency of carbon recoils in a stilbene crystal was measured for recoil energies of 30 keV to 1 MeV using neutrons from $^7$Li(p,n)$^7$Be and $^{252}$Cf. Anisotropic response was confirmed in low energy regions. The variation of the scintillation efficiency was about 7 %, that could detect the possible dark matter signal.Comment: 12 pages, 6 figures, to be published in Physics Letters

ISAI: Investigating Solar Axion by Iron-57

The existence of the axion is a unique solution for the strong CP problem, and the axion is one of the most promising candidates of the dark matter. Investigating Solar Axion by Iron-57 (ISAI) is being prepared as a complemented table-top experiment to confirm the solar axion scenario. Probing an X-ray emission from the nuclear transitions associated with the axion-nucleon coupling is a leading approach. ISAI searches for the monochromatic 14.4 keV X-ray from the first excited state of 57Fe using a state-of-the-art pixelized silicon detector, dubbed XRPIX, under an extremely low-background environment. We highlight scientific objectives, experimental design and the latest status of ISAI