Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers

Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers are investigated. The authors reported that the carrier lifetime in n-type epilayers increased by reduction of deep levels through thermal oxidation and thermal annealing. However, the carrier lifetimes in p-type epilayers were not significantly enhanced. In this study, in order to investigate the influence of surface passivation on the carrier lifetimes, the epilayer surface was passivated by different oxidation techniques. While the improvement of the carrier lifetime in n-type epilayers was small, the carrier lifetime in p-type epilayers were remarkably improved by appropriate surface passivation. For instance, the carrier lifetime was improved from 1.4 μs to 2.6 μs by passivation with deposited SiO2 annealed in NO. From these results, it was revealed that surface recombination is a limiting factor of carrier lifetimes in p-type 4H-SiC epilayers

Nucleosynthesis in Supernovae, Hypernovae/Gamma-ray Bursts and Compact Binary Mergers

We present the status and open problems of the astrophysical sites responsible for the nucleosynthesis of Fe-group and heavier elements (with the exception of the s-process). This involves type Ia supernovae with the requirement to have a low Ye-component (for the explanation of 55Mn), the role of the core collapse supenova explosion mechanism in the composition of the Fe-group (and heavier?) ejecta, the transition between neutron star and black hole remnants as the result of the collapse of massive stars, and the relation of the latter with supernova and/or gamma-ray bursts/hypernovae. In addition, the role of compact binary mergers is discussed, especially with respect to forming the heaviest r-process elements in galactic eveolution

Complete set of polarization transfer coefficients for the 3He(p,n){}^{3}{\rm He}(p,n) reaction at 346 MeV and 0 degrees

We report measurements of the cross-section and a complete set of polarization transfer coefficients for the ${}^{3}{\rm He}(p,n)$ reaction at a bombarding energy $T_p$ = 346 MeV and a reaction angle $\theta_{\rm lab}$ = $0^{\circ}$. The data are compared with the corresponding free nucleon-nucleon values on the basis of the predominance of quasi-elastic scattering processes. Significant discrepancies have been observed in the polarization transfer $D_{LL}(0^{\circ})$, which are presumably the result of the three-proton $T$ = 3/2 resonance. The spin--parity of the resonance is estimated to be $1/2^-$, and the distribution is consistent with previous results obtained for the same reaction at $T_p$ = 48.8 MeV.Comment: 4 figures, Accepted for publication in Physical Review

Electron-induced proton knockout from neutron rich nuclei

We study the evolution of the \eep cross section on nuclei with increasing asymmetry between the number of neutrons and protons. The calculations are done within the framework of the nonrelativistic and relativistic distorted-wave impulse approximation. In the nonrelativistic model phenomenological Woods-Saxon and Hartree-Fock wave functions are used for the proton bound-state wave functions, in the relativistic model the wave functions are solutions of Dirac-Hartree equations. The models are first tested against experimental data on $^{40}$Ca and $^{48}$Ca nuclei, and then they are applied to a set of spherical calcium isotopes.Comment: 5 pages, 2 figures. contribution to the XIX International School on Nuclear Physics, Neutron Physics and Applications, Varna (Bulgaria) September 19-25, 201

Probing nuclear skins and halos with elastic electron scattering

I investigate the elastic electron scattering off nuclei far from the stability line. The effects of the neutron and proton skins and halos on the differential cross sections are explored. Examples are given for the charge distribution in Sn isotopes and its relation to the neutron skin. The neutron halo in $^{11}$Li and the proton halo in $^{8}$B are also investigated. Particular interest is paid to the inverse scattering problem and its dependence on the experimental precision. These studies are of particular interest for the upcoming electron ion colliders at the GSI and RIKEN facilities.Comment: 27 pages, 9 figures, accepted for publication in J. Phys.

The monitoring system for the aerogel Cherenkov counter of the BELLE detector

We report on a design and performances of a monitoring system developed for the aerogel Cherenkov counters (ACC) of the BELLE detector. The system consists of blue LEDs, a diffuser box, and optical distributors which distribute the LED light to the ACC modules. The employed LED (NSPB series) has been observed to have high reliability on the long term stability and the temprature dependence. The diffuser box is employed to reduce the intrinsic non-uniformity of the LED light intensity. The overall performances of the present monitoring system on uniformity and intensity of the light output have been found to satisfy all the requirements for the monitoring.Comment: 24 pages, LaTeX, 13 eps figures, to be published in Nucl. Instrum. and Meth. A. Postscript file (4.5 MB) is available at http://www-hep.phys.saga-u.ac.jp/~murakami/paper/xxx_accmon.p