K. Nakai

Half-life of 44Ti

Abstract The half-life of 44 Ti has been determined with a method measuring the activity of 44 Ti produced and implanted in a plastic plate through the projectile fragmentation. The half-life was determined from the specific activity of implanted 44 Ti nuclei determined through absolute measurements of the amount by counting fragments, and of their activity by taking ratios of sum- and single-peaks in high-resolution γ -ray spectra with a Ge detector. The half-life of 44 Ti determined was 59±2 years.

A low-momentum π-μ channel at the KEK 12 GeV proton synchrotron

Abstract A low-momentum secondary beam channel for pion-and muon-experiments has been constructed at the KEK proton synchrotron. Pions produced at 90° to the 12 GeV primary proton beam are extracted with a simple beam optics of two quadrupole doublets and a single 45° bending magnet. The large angle extraction resulted in a good π/e ratio of more than 80% for p π > 150 MeV/ c . The maximum available pion intensity for p π = 200 MeV/ c is 10 7 /pulse. The channel can be used parasitically to other high-energy experiments. The design of the channel, results of the performance tests and some experiments using the channel are described.

Structure of the transitional nucleus 149Eu

The level structure of the transitional nucleus 149Eu was studied by means of in-beam γ-ray spectroscopy using the 150Sm(p, 2nγ)149Eu reaction. The 152−(994.3 keV) and 192−(1609.3 keV) favoured states of the decoupled band based on the 112− isomeric state were found, and the unfavoured 132−(1175.8 keV) state was also found. The positive-parity Δ I = l bands based on the 52+ ground state and the 72+ first excited state were assigned. These states are discussed in terms of a simple particle-plus-rotor model.

The g-factor measurement for the 8+ isomeric state of 86Sr produced in Kr gas

Abstract The g-factor of the 8+ isomeric state ( T 1 2 = 460 nsec ) in 86Sr, produced via the Kr(α, 2n)Sr reaction, was determined to be g(8 + ; 86 Sr ) = −0.243±0.004 by the stroboscopic resonance method. It was found that about a half of the nuclear alignment was preserved in the gaseous environment.

Beam-pulsing system for the IMS cyclotron

Abstract An external beam-pulsing system to produce pulsed beams of various time characters (several tens of nanoseconds to seconds) out of a cyclotron beam has been installed for the purpose of studying delayed-γ-ray phenomena. It is composed of two parts. For short time ranges a sinusoidal electric field sweeps the beam horizontally to obtain one out of every 2, 3, 4, 6 or 12 natural beam pulses. For longer time ranges ( > 1 μs) a rectangular pulse-shaped electric field is used to deflect unwanted beams vertically. A combination of the two deflectors makes a versatile time range available for experiments. The design and construction of the system and some experiments performed are described.

Study of energy deposition of GeV particles in nuclei

Abstract The highly-inelastic process in hadron-nucleus reactions at several GeV has been studied to investigate mechanisms of energy deposition of GeV particles in nuclei and possibilities to search for any signature of unusual phenomena.