arXiv subjects

M. Sakai

Publications and source records attributed to M. Sakai.

23 records · Page 2Linked to original sources

arXiv2015

A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector

We describe a compact, ultra-clean device used to deploy radioactive sources along the vertical axis of the KamLAND liquid-scintillator neutrino detector for purposes of calibration. The device worked by paying out and reeling in precise lengths of a hanging, small-gauge wire rope (cable); an assortment of interchangeable radioactive sources could be attached to a weight at the end of the cable. All components exposed to the radiopure liquid scintillator were made of chemically compatible UHV-cleaned materials, primarily stainless steel, in order to avoid contaminating or degrading the scintillator. To prevent radon intrusion, the apparatus was enclosed in a hermetically sealed housing inside a glove box, and both volumes were regularly flushed with purified nitrogen gas. An infrared camera attached to the side of the housing permitted real-time visual monitoring of the cable's motion, and the system was controlled via a graphical user interface.

physics.ins-det↗

arXiv2015

A new type of Neutrino Detector for Sterile Neutrino Search at Nuclear Reactors and Nuclear Nonproliferation Applications

We describe a new detector, called NuLat, to study electron anti-neutrinos a few meters from a nuclear reactor, and search for anomalous neutrino oscillations. Such oscillations could be caused by sterile neutrinos, and might explain the "Reactor Antineutrino Anomaly". NuLat, is made possible by a natural synergy between the miniTimeCube and mini-LENS programs described in this paper. It features a "Raghavan Optical Lattice" (ROL) consisting of 3375 boron or $^6$Li loaded plastic scintillator cubical cells 6.3\,cm (2.500") on a side. Cell boundaries have a 0.127\,mm (0.005") air gap, resulting in total internal reflection guiding most of the light down the 3 cardinal directions. The ROL detector technology for NuLat gives excellent spatial and energy resolution and allows for in-depth event topology studies. These features allow us to discern inverse beta decay (IBD) signals and the putative oscillation pattern, even in the presence of other backgrounds. We discuss here test venues, efficiency, sensitivity and project status.

physics.ins-det↗

arXiv2014

Suzaku Observation of HESS J1507-622

HESS J1507-622 is one of the bright unidentified TeV objects. HESS J1507-622 is unique, since the location of the object is off the Galactic disk. We observed the HESS J1507-622 region with the Suzaku XIS, and found no obvious counterpart although there is no severe interstellar extinction. However, there are two interesting X-ray objects; SRC1 is a bright extended source, and SRC2 is a faint diffuse object. If either of them is a counterpart, the flux ratio between TeV and X-ray is large, and HESS J1507-622 is a real dark particle accelerator.

astro-ph.HE↗

arXiv2011

Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector

We report a measurement of the neutrino-electron elastic scattering rate from 8B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5 MeV analysis threshold is 1.49+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1. The analysis threshold is driven by 208Tl present in the liquid scintillator, and the main source of systematic uncertainty is due to background from cosmogenic 11Be. The measured rate is consistent with existing measurements and with Standard Solar Model predictions which include matter enhanced neutrino oscillation.

hep-ex↗

arXiv2000

Interpretation of a microwave induced current step in a single intrinsic Josephson junction on a Bi-2223 thin film

Thin stacks consisting of a single intrinsic Josephson junction on (Bi,Pb)-Sr-Ca-Cu-O thin films are investigated under the influence of external microwave fields. The $I$-$V$-characteristic shows a single resistive branch, a clear superconducting gap edge structure and a pronounced current step in external microwave fields. With increasing irradiation power it shifts to higher voltages, while the height of the step remains practically unchanged. In a numerical simulation including an ac-magnetic field parallel to the superconducting layers the experimental features of the structure can be explained by a collective motion of Josephson fluxons.

cond-mat.supr-con↗