Yuehu Pu

Performance of a phoswich detector composed of thin plastic and thick BaF2 scintillators

Abstract A phoswich detector which consists of thin plastic and thick BaF 2 scintillators has been tested using heavy ion reactions. It was found that gamma-rays, neutrons and charged particles with an atomic number up to 8 can be clearly distinguished. Based on the obtained resolution of particle identification, practical use of the detector has been discussed.

Complex fragment distributions in 84Kr+27Al at Elab=10.6 MeV/u

Abstract The distributions of atomic number Z and isotopic mass and the missing atomic number ΔZ in binary decay, which were obtained from the experiment for 84 Kr+ 27 Al at the incident energy of 10.6 MeV/u at the RIKEN Ring Cyclotron Facility, are analyzed in terms of the extended Hauser-Feshbach method (EHFM) and several features of the sequential decay mechanisms have been revealed.

The competition between fusion-fission and deeply inelastic reactions in the medium mass systems

The competition between fusion-fission and deeply inelastic reactions in the Cl + Ni system has been studied by investigating the exit channelQ-value dependence of theZ-distributions of fission-like fragments. TheZ-, kinetic energy- and angular distributions of the fission-like fragments produced in the37Cl +64Ni system atElab=170, 186 MeV and in the28Si +74Ge system atElab=176 MeV have been measured by counter telescopes. TheZ-distribution of the37Cl +64Ni system was found to be essentially the same as that of the35Cl +62Ni system at the same bombarding energy. It is shown that this result can not be explained by the statistical fusion fission model but is consistent with a deeply inelastic model. A systematic study of the fission-like phenomenon in this mass region indicates that the maximum angular momenta for fusion reactions as well as the minimum angular momenta for DIC can be reproduced by the Bass model in the sliding limit (f=1.0) while the maximum angular momenta for fully energy-damped deeply inelastic reactions are governed by the strong interaction radius as predicted by the successive critical distance fusion model. The significance of these results are discussed.

Complex fragment mass distributions IN84Kr+27AlATElab=10.6 MeV/u

To study the decay mechanisms of intermediate mass fragments and fission products from a hot compound nucleus, we made an experiment for 84Kr+27Al at the energy of 10.6 MeV/u using Riken Ring Cyclotron Facility. The distributions of nuclear element Z and its isotope mass are extensively analyzed in terms of Extended Hauser‐Feshbach Method (EHFM) and it is concluded that the sequential decay plays an important role in the decay process from the highly excited compound nucleus. The dependence of element distributions on angular momentum is intensively discussed by comparing the two systems 84Kr+27Al and 3He+Ag, which form the same compound nucleus with different angular momentum window at the same excitation energy.

Statistical emission of complex fragments from highly excited compound nucleus

In order to study the mechanism of complex fragments production from highly excited light and medium compound nucleus induced by relatively low energy heavy ion reactions, the full statistical analysis have been performed in terms of Extended Hauser Feshbach (EHF) method. At first the charge‐ and kinetic energy‐distributions of 35Cl+12C reaction at (ELab=180,200 MeV) and 23Na+24Mg reaction at (ELab=89 MeV) which form the 47V compound nucleus of almost same excitation energy are extensively investigated as a prototype of the light mass system. The variations in observed cross section from fragment to fragment are understood by the variations of binding energy of the lighter fragments of binary decay from the compound nucleus. The difference of the yield in the measured cross sections between the reactions is interpreted as the entrance channel effect that 23Na+24Mg channel has the larger critical angular momentum for fusion cross section than 35Cl+12C channel. The measured kinetic energy distributions in t...

Search for elementary process of cluster impact fusion using atomic heavy ions

In order to investigate the role of heavy nuclei in the heavy water cluster impact d+d fusion, we have undertaken a series of d+d fusion experiments using atomic and molecular heavy ions (C, O, Ne, Ar, Kr, and Xe) on the deuterated solid targets in the energy range of 0.4–4 MeV. The observed excitation functions of 3 MeV proton yields are well accounted for in terms of the two step knock‐on cascade model. No distinct differences were observed in d+d fusion rate even when the number of atoms in the oxygen molecule (O+, O2+ and O3+) were changed. Extending the calculation of the excitation function of the atomic oxygen impact fusion rate up to the extremely low incident energies (∼keV), it has been found that the estimated proton yields are much smaller than the heavy water cluster impact fusion by 10 orders of magnitude. This indicates that the recent observation of strong enhancement of cluster impact d+d fusion from Brookhaven cannot be explained by the sum of usual elementary processes but must be due t...