Hajime Ohnuma

Coulomb breakup of light composite nuclei

Abstract We present a new analysis of the Coulomb dissociation of nuclei comprising a charged core and one or more neutral valence particles at energies of tens of MeV/nucleon and above. The approach assumes only that excitation of the projectile is to the low energy continuum. A successful comparison is made with new high precision measurements of small angle deuteron dissociation at 140 MeV incident energy.

(3He, d) Stripping to Bound and Unbound States in 29P

The 28 Si ( 3 He, d) 29 P reaction has been studied at an incident energy of 29.3 MeV. Comparisons of DWBA and CCBA analyses of angular distributions for low-lying bound states show that channel-coupling effect is not important except for stripping to the 1.95-MeV 5/2 + state. Angular distributions for resonance states are analyzed by using Gamow functions as form factors for DWBA calulations. Such a description gives a reasonable account of the experimental angular distributions except that it fails to reproduce experimentally observed j -dependence.

Vector analyzing power and polarization measurements for the 116Sn(d, p)117Sn reaction and deuteron D-state effects

Abstract The vector analyzing power A y and polarization P y have been measured for the l n = 0 reaction 116 Sn(d, p) 117 Sn(g.s.) at E d = 22 MeV to obtain the quantities S p = 2( P y - A y ) and S d = 3 A y - 2 P y . Large and negative values of S d can be explained by deuteron D-state effects.

Three-Ge(Li) Compton polarimeter with kinematic selection

Abstract The performance of a three-Ge(Li) Compton polarimeter with kinematic selection has been investigated. It has been shown that elimination of unwanted events by kinematic selection makes it possible to construct a polarimeter which has high polarization sensitivity, large solid angle and good signal-to-noise ratio. The usefulness of the polarimeter has been demonstrated in an example of the spin-parity assignment of the 2432 keV state in 49Cr.

Detector system of the first focal plane of the spectrometer SMART at RIKEN

Abstract A detector system of the first focal plane of SMART, the 135xa0MeV/u high-resolution spectrometer at RIKEN Accelerator Research Facility, is described. It consists of a pair of multi-wire drift chambers and a trigger scintillator hodoscope contained in a He-filled detector box. A major subject using this system is the measurement of the (d, 2 He) reaction making the most of its large angular and momentum acceptances. Without seriously sacrificing the detection efficiency, reasonably good energy and angular resolutions for 2 He, 460xa0keV and 9xa0mrad (FWHM), respectively, have been achieved after optimizing the optics property of the spectrometer.

Analog (p, t) and (p, τ) reactions on 14N induced by 52 MeV protons

Abstract The 14 N(p, t) 12 N and 14 N(p, τ) 12 C reactions leading to T = 1 states have been studied. The angular distributions for the 15.11 MeV 1 + T =1 state in 12 C and for the ground state in 12 N and the ratio of these cross sections can not be explained by DWBA theory.

A liquid-helium scintillator as a fast-neutron polarimeter

Abstract A liquid-helium neutron polarimeter was constructed and successfully used for polarization measurements in (p, n) and (d, n) reactions. Its effective analyzing power was about 0.7, in good agreement with a Monte Carlo calculation which includes the effects of multiple scattering and the finite size of the scatterer and the detectors. The response of the liquid-helium scintillator to neutrons was measured between 3 and 18 MeV. A linear relation was observed between the incident neutron energy and the maximum light output. No significant position dependence of the light output was found.

Excitation of giant Gamow-Teller resonances in the reaction 140Ce(p, n)140Pr

Abstract Two broad peaks were observed at E x = 6.5 and 12.1 MeV in the (p, n) reaction on 140 Ce at E p = 38 MeV. They are interpreted as the T = T 0 − 1 Gamow-Teller resonances (GTR). A self-consistent TDA model with a Skyrme type interaction predicts such a splitting of the T = T 0 − 1 GTR, and reproduces the relative energies and strengths of the components. Experimental results are also compared with a recent RPA calculation which includes Δ -hole excitations.

Angular Distribution for the Reaction 16O(p, t)14O* (6.27 MeV) and Channel Coupling Effects

Angular distribution for the 16 O( p , t ) 14 O * (6.27 MeV) reaction obtained at E p =52 MeV has confirmed a previous observation that it cannot be fitted by L =3 DWBA. An explanation in terms of couple-channel Born approximation is presented.

Contributions of spin‐dependent effects to the vector analyzing power and proton polarization for ln=0 (d,p) reaction

Both the vector analyzing powers and the proton polarizations have been measured for the 116Sn(d,p)117Sn(grd., 1/2+) and 29Si(d,p) 30Si(grd.,0+) reactions at 22.2 MeV. The separation of the contributions from the proton and deuteron spin‐orbit distortions has been performed for these ln=0 transfers using the method of Johnson. The obtained results have been compared with DWBA and the adiabatic calculations.