Michael F. Werby

Optical model analysis of 9Be(p, p0)9Be cross sections and polarizations from 6 MeV to 30 MeV

Abstract Cross-section and polarization data for proton elastic scattering from 9Be in the lab energy range 6 to 30 MeV and in the angular range 20° to 160° have been analyzed using an optical model potential. Good quality fits are obtained with potential parameters which vary smoothly with energy. The effects of energy-averaged compound-nucleus resonances and of quadrupole coupling on the elastic scattering are investigated. The reaction is suggested for use as a polarization monitor since it compares favourably with α(p, p)α for this purpose. Contour maps of polarization, P, and cross section times P2 are given as a function of angle and energy.

Cluster-transfer analysis of the 7Li(3He, p)9 Be reaction

Abstract An exact finite-range two-mode multi-interaction DWBA cluster-transfer analysis of the 7 Li( 3 He, p) 9 Be reaction for 3 He bombarding energies of 3.2, 4.5, and 10 MeV is performed using the computer code FANLU2. It is found that it is essential to include the exchange mode in order to describe the angular distributions at backward angles and that the analysis provides a good overall description of the reaction when the full exact finite-range multi-interaction formalism is employed. Extracted spectroscopic factors indicate that d⊕ 7 Li is a more probable cluster configuration for 9 Be than is 3 He⊕ 6 He, but the latter configuration plays an important role in the analysis. The various cancellation approximations that can be employed in the DWBA are shown to be inadequate for this reaction.

Exchange effects in the 7Li(3He, α)6Li reaction

Abstract Angular distributions of α-particles from the 7Li(3He, α)6Li reaction at 3He bombarding energies of 16 and 18 MeV are analyzed with an exact finite-range two-mode DWBA formalism using the computer code FANLU2. It is demonstrated that within the formalism used it is essential to include the exchange mode of the reaction. The overall features of the angular distributions are described remarkably well, but a strong dependence on optical model parameter sets makes it essential to adhere to a characteristic class of such sets. Spectroscopic factors for direct and exchange modes are extracted and discussed.

Study of angular asymmetries in the 2H(α, 3He)3H reaction

Abstract The Barshay-Temmer theorem predicts that the angular distribution of the products of the reaction 2H(α, 3He)3H will be symmetric about 90° in the c.m. system. Recently, asymmetries have been reported in the angular distribution in excess of 10 % at some angles. These asymmetries clearly violate the theorem. In an effort to explain the asymmetry as well as describe the angular distribution an exact finite-range multi-interaction DWBA calculation, which includes all appropriate one-particle transfer reaction mechanisms, was employed. Semi-realistic three-nucleon wave functions were utilized in one case in deriving the form factors appropriate for two-particle clustering of the tri-nucleon systems and various Coulomb effects associated with the interactions were included. It was found that both the asymmetry and angular distribution are well described within the present formalism.

Time domain solutions for scattering from objects in a waveguide

Calculations that describe scattering from an object in a waveguide in the frequency domain are very time consuming. For the time domain it can be orders of magnitude more expensive both in time and storage than for the frequency domain, rendering such calculations impractical unless a supercomputer can be used. The solution of scattering from an object for a realistic target and waveguide using the Cray 2 computer (a 528‐Megaword, 4.1‐ns machine) at the Minnesota Supercomputer Institute is discussed. The methods employed as well as results will be presented.

A perturbation method for normal mode theory with variable velocity profile

Normal mode theory is a very well‐developed technique for predicting the propagation loss in the ocean for most stratified environments and velocity profiles, as well as some range‐dependent environments. So why another method? The reason is that sometimes it is desirable to retain the simple trigonometric functions obtained from constant velocity profiles. This is usually done by employing the approximate scheme of using multiple layers in each of which the velocity profile is assumed constant. In this work, it is shown that this can be carried out nicely by representing the velocity profile in terms of a mini‐max fit using Tschebyscheff polynomials and a first‐order perturbation technique derived from Sturm‐Liouville theory. The derivation leads to a compact closed expression that is easily programmable. The results from the formulation are compared with other methods.