K. Ishida

Method of probing inner-structure of geophysical substance with the horizontal cosmic-ray muons and possible application to volcanic eruption prediction

Abstract One potential use of cosmic-ray muons arriving nearly horizontally along the earth is a probe of the inner-structure of a gigantic geophysical substance, such as a volcanic mountain. A simple detection system comprising a plastic scintillator hodoscope which is expandable to a larger scale was developed. The first successful measurement of the inner-structure of Mt. Tsukuba is described. The future perspective of the application of the present method towards the prediction of volcanic eruption is discussed.

Development of a two-fold segmented detection system for near horizontally cosmic-ray muons to probe the internal structure of a volcano

Abstract Very high-energy cosmic-ray muons penetrating through a mountain enable us to probe internal structure of volcanoes. An improved cosmic-ray muon detection system comprising two segmented detectors with multiplicity cut of the soft-component background of cosmic ray was developed. By applying to the measurement on internal structure of the volcano Mt. Asama, we proved that the volume occupancy in the region of a crater is less than 30%.

The RIKEN-RAL pulsed Muon Facility

Abstract RIKEN has constructed a pulsed muon facility at Rutherford Appleton Laboratory (RAL) in the UK under an international collaboration between RIKEN and RAL to promote muon science. We have confirmed that the facility produces a pulsed decay muon beam as well as a pulsed surface positive muon beam with the highest instantaneous intensity in the world and initiated the muon science research program, which includes muon catalyzed fusion, since June 1995.

Development of the Cosmic-Ray Muon Detection System for Probing Internal-Structure of a Volcano

Very high-energy cosmic-ray muons penetrating through a mountain enable us to probe the internal structure of volcanoes. An improved cosmic-ray muon detection system comprising two segmented detectors with multiplicity cut of the soft components of cosmic rays was developed. The test measurement for the volcano Mt. Asama is described.

Electrical Properties of Liquid Te–Se Mixtures at High Temperatures and High Pressures

The electrical conductivity σ and the thermoelectric power S have been measured for liquid Te–Se mixtures in a wide temperature and pressure range. Substantial changes in σ and S are induced by a slight application of pressure. The region where such changes occur is determined can the concentration-temperature plane. It is suggested that the observed semiconductor to metal transition is originated from the structural change.

New RIKEN-RAL pulsed µCF facility and X-ray studies on DT-µCF

In November 1994, the construction of a new superconducting muon channel of the RIKEN-RAL muon facility at ISIS of Rutherford Appleton Laboratory was completed. Subsequently, important features, such as the highest instantaneous intensity with a single-pulse structure and a high purity have been confirmed. Along with the installation of advanced µCF experimental equipment, including a high-purity D-T mixture target system with an in situ3He removal capability and a 4 T confinement magnet, an advanced µCF experiment, e.g. a precise X-ray measurement on µ-α sticking in dtµ-µCF will be realized. An account of the commissioning experiments, a plan for the earliest phase of the µCF experiment and possible future directions are reported.

X-ray studies on muon transfer reactions from hydrogen to helium

We have experimentally studied the muon transfer reactions from hydrogen to helium in liquid hydrogen with helium impurity concentration around 100–1000 ppm. The X-ray from the decay of (d4Heμ) molecule was clearly observed in the D2-4He system, whereas the corresponding X-ray was very weak in other systems such as D2-3He and H2-4He. This is well explained by the particle decay mode of the muonic molecule.

Construction of Riken-ral muon facility at ISIS and advanced μSR

By utilizing the intense pulsed proton beam available at the ISIS facility of RAL, the new muon facility project of an advanced superconducting muon channel funded by the RIKEN is now under construction. The new facility, by adopting the superconducting solenoid system, will produce the strongest backward decay pulsedμ+ orμ−in the momentum range from 20 MeV/c to 120 MeV/c. Also, by adopting the pulsed magnetic kicker, each one of two muon pulses will be supplied to two extraction channels simultaneously. Various important muon science experiments including advanced pulsedμ−SR andmu+SR experiments will be realized.

Density enhancement of muon beams with tapered glass tubes

We have demonstrated that the beam density of 54 MeV/c muons can be increased almost by a factor of two when a tapered glass tube is inserted coaxially along the muon beam. The observations are compared with a multiple Coulomb scattering calculation, which reproduces the observation reasonably. This technique opens a new and simple way to increase the muon intensity effectively.

Muon catalyzed fusion and muon to 3He transfer in solid T2 studied by X-ray and neutron detection

X-ray and neutron measurements were carried out for muon catalyzed fusion and related phenomena in solid T2. The X-ray originated from the μ- to α sticking in muon catalyzed fusion; t + t + μ-→ (μ-α) + 2n was measured for the first time, yielding Kα X-ray intensity of (μα) atom and the intensity ratio of Kβ to Kα. Utilizing the phenomena of 3He accumulation in solid T2, the X-ray in the μ- transfer process from (tμ) to 3He was detected, providing a formation rate and radiative decay branching-ratio of (t3Heμ) molecule. From fusion neutron measurements, estimated values were obtained for (ttμ) molecular formation rate as well as sticking probability ωt in ttμ fusion. A possible new insight in t + t fusion reaction process at a low energy limit is also obtained.