Volume 28, Issue 4, July 1997
28(1997); http://dx.doi.org/10.1134/1.953043View Description Hide Description
The methodological principles of constructing various practical methods for the multilevel parametrization of resonance neutron cross sections are formulated on the basis of the classical results of Wigner -matrix theory. The general structure of the well known code SAMMY, which has been used effectively in recent years to analyze and represent the detailed energy structure of the cross sections in wide ranges of the region of resolved levels, is discussed. It is shown that similar results can also be obtained by the combined method and the method of rigorous pole expansion of the matrix. The algorithms for transforming the parameters of the various methods are presented, and their advantages in the practical use of the ENDF/B-6 parameters are discussed.
28(1997); http://dx.doi.org/10.1134/1.953044View Description Hide Description
A series of methods and nuclear models for describing the properties of the ground and excited positive-parity states of even–even deformed nuclei are described and tested on practical problems. Some models are illustrated by examples of their application. Calculations are carried out for the isotopes and The experimentally observed properties of low-lying states are studied systematically, and the structure of the wave functions of rotational levels is analyzed. The role of angular resonance states in the mixing of states with different internal configurations is discussed. The predictive powers of the methods and models are demonstrated.
28(1997); http://dx.doi.org/10.1134/1.953045View Description Hide Description
The recent developments in the theory of the generation of potentials for which the Schrödinger equation has an exact solution are discussed. The generalization of the Darboux transformation to the nonstationary Schrödinger equation is studied in detail. The supersymmetric generalization of the nonstationary Schrödinger equation is formulated. Versions corresponding to exact and spontaneously broken supersymmetry are discussed. New, exactly solvable nonstationary potentials are obtained as examples. The stationary Darboux transformation is viewed as a special case of the new transformation. Families of isospectral potentials with the spectra of the harmonic oscillator and the hydrogen-like atom are obtained. The effectiveness of these methods for describing the coherent states of the transformed Hamiltonians is demonstrated.
28(1997); http://dx.doi.org/10.1134/1.953046View Description Hide Description
Algorithms for closed-orbit correction in synchrotrons and related topics such as error sources, statistical characteristics of the orbit, etc., are discussed. The review covers both traditional methods for orbit correction (beam-bump, harmonic correction, etc.) and new developments (eigenvector correction, SVD, algorithms for optimum positioning of dipoles, etc.). The use of expert systems and artificial neural networks is described as well. The last section is devoted to first-turn steering.
28(1997); http://dx.doi.org/10.1134/1.953047View Description Hide Description
The recent experimental data on the quasielastic scattering of light unstable nuclei on stable target nuclei are reviewed. The microscopic approaches to the construction of the nucleon density distributions in nuclei and the projectile–target interaction potentials are described. The cross sections for quasielastic scattering are analyzed for a large group of light exotic nuclei. The problem of the existence of a neutron or protonhalo in nuclei and other features of the nuclear matter distribution are discussed. Possible future experiments on quasielastic scattering and other reactions using radioactive beams are suggested.