Minoru Takasaki

Bio: Minoru Takasaki is an academic researcher from KEK. The author has contributed to research in topics: Beam (structure) & Proton Synchrotron. The author has an hindex of 13, co-authored 76 publications receiving 616 citations.

Radiation damage in silicon microstrip detectors

Abstract: A radiation damage effect on silicon strip detectors of pn-junction type is investigated using a high energy proton beam. In order to clarify the cause of leakage current increase, several variations of strip detectors with different surface structures were made and tested. No appreciable differences in leakage current increase are observed among these samples. A strong temperature dependence on leakage current is observed. This can be explained by a formation of radiation induced trap energy levels in the bulk silicon. A moderate room temperature annealing is seen. A pulse height degradation of about 10–20% is observed at a few Mrad of radiation. Some implications of the present results are discussed for possible application of silicon semiconductor detectors in future high energy hadron colliders.

Antiproton-proton annihilation at rest into pi 0M and gamma M with M= phi, eta ', omega, rho 0, eta, and pi 0.

Abstract: We have carried out high-statistics measurements of inclusive ..pi../sup 0/ and ..gamma..-ray spectra from p-barp annihilation at rest. From the monochromatic peaks in the ..pi../sup 0/ spectra, we derive the yield (or its upper limit) of the reaction p-barp..--> pi../sup 0/M for M = phi, eta', ..omega.., rho/sup 0/, eta, and ..pi../sup 0/. The same quantity was independently obtained from the ..gamma..-ray spectra, which included some ..pi../sup 0/'s that were mistaken as single ..gamma.. rays due to the limited granularity of the ..gamma.. detector. Taking the monochromatic peaks in the ..gamma..-ray spectra as being due to prompt ..gamma.. rays, we also derive the upper limit for p-barp..--> gamma..M.

Radiation hardness of cerium-doped gadolinium silicate Gd2SiO5:Ce against high energy protons, fast and thermal neutrons

Abstract: Degradation of Gd 2 SiO 5 :Ce in optical transmittance due to proton irradiation was negligibly small below 10 6 rad, smaller than 2%/cm at 10 7 rad and large at 10 8 rad. The radiation hardness of 10 7 rad against protons is by two orders of magnitude smaller than against low energy γ-rays. Long term spontaneous recovery of the proton-induced damage is not large (10–20% of the initial degradation in 84 days). Recovery upon exposure to UV light occurs to some extent. Degradation due to thermal neutrons was negligibly small for a fluence of 10 14 n/cm 2 . No degradation was observed for exposure to fast neutrons of about 10 13 n/cm 2 during one year in the extracted beam tunnel of proton synchrotron.

Development of Superconducting Combined Function Magnets for the Proton Transport Line for the J-PARC Neutrino Experiment

Abstract: Superconducting combined function magnets will be utilized for the 50 GeV, 750 kW proton beam line for the J-PARC neutrino experiment. The magnet is designed to provide a dipole field of 2.6 T combined with a quadrupole field of 19 T/m in a coil aperture of 173.4 mm at a nominal current of 7345 A. Two full-scale prototype magnets to verify the magnet performance were successfully developed. The first prototype experienced no training quench during the excitation test and good field quality was confirmed.

The T2K Experiment

Abstract: The T2K experiment is a long-baseline neutrino oscillation experiment Its main goal is to measure the last unknown lepton sector mixing angle {\theta}_{13} by observing { u}_e appearance in a { u}_{\mu} beam It also aims to make a precision measurement of the known oscillation parameters, {\Delta}m^{2}_{23} and sin^{2} 2{\theta}_{23}, via { u}_{\mu} disappearance studies Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem

The Super-Kamiokande detector

Abstract: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons. During the period April, 1996 to July, 2001, Super-Kamiokande I collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency. These data provided crucial information for our current understanding of neutrino oscillations, as well as setting stringent limits on nucleon decay. In this paper, we describe the detector in detail, including its site, configuration, data acquisition equipment, online and offline software, and calibration systems which were used during Super-Kamiokande I.

Indications of Neutrino Oscillation in a 250 km Long-Baseline Experiment

Abstract: The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.