Vol. 18, No. 9 (1962)
1962-05-05
CONTENT
1962, 18 (9): 435-442.
doi: 10.7498/aps.18.435
Abstract +
The effect of magnetic annealing on the ferromagnetic resonance linewidth of a single crystal of normal ferrites or of ferrous ferrite containing a small concentration of substitutional Co2+ ions is calculated. The calculations are based on a mechanism of magnon scattering induced by the ion-to-ion variation of the spin-orbit interaction as suggested by Haas and Callen. The result obtained shows that besides the isotropic part of linewidth, there is an anisotropic part, which depends on the direction of the field applied during annealing as well as on the direction of magneti2ation. For each percent of cobalt the maximum directional variation of linewidth may be of the order of 4 oersted.
1962, 18 (9): 449-466.
doi: 10.7498/aps.18.449
Abstract +
The present author suggests a new distribution function for the roots of the complex polynomial corresponding to the nulls of the radiation pattern of a linear antenna array on the unit circle in a complex plane which is more general than the one suggested by the same author in a previous paper. The new distribution function is of the form ψK=ψ0{1+ξK((ln(ψm/ψ0-1)-lnξ)/(ln m))}. When ψ0 and ξ are chosen properly, the suggested distribution includes the following distributions or arrays as special cases: (1) the uniform end-fire arrays; (2) the uniform broadside arrays; (3) the Schelkunoff's distribution in the range of ψ; (4) the Dolph-Tchebyscheff's distribution for number of elements not greater then seven. But the suggested distribution has the advantage of improving all of them, especially for the suppression of side-lobes near-by the main beam which is very important in certain practical applications.Moreover, since the primary patterns of many types of radiating elements fall off with increasing angle from the main maximum so that the wide-angle lobes would be at a lower level than those close to the main beam, it is necessary to design an array pattern in such a way so that the side-lobes should increase in magnetude with increase in angle from the position of the main beam in order to achieve an over-all pattern with side-lobes all equal or approximately equal in magnitude which is useful in many practical applications. Neither Schelkunoff's distribution in the range of ψ nor Dolph-Tchebyscheff's distribution meets this requirement but the suggested distribution does.In this paper, explicit expressions for the relative antenna currents have been put in closed forms convenient for calculation and semigraphical method has been used for all the pattern calculations.
1962, 18 (9): 471-482.
doi: 10.7498/aps.18.471
Abstract +
An attempt is made to explain the observed structure phenomenon in the 2-3 Mev region of the spectra of the neutrons from the fission of U235 or Pu239 by the thermal neutron. Three possible causes for the effect are proposed and investigated. Firstly, . the effect of distribution of the nuclear temperature is studied. It is found that a continuous distribution of the nuclear temperature is unable to cause formation of any structure in the spectra, while two distinct nuclear temperatures would bring about such an effect; however, the value of the ratio of the two temperatures, i.e. T1/T2≥ 3 seems rather unreasonable. Next, in the "evaporation" formula of the energy spectra, the absorption cross section of the optical model is employed. In the case of fission, giant resonances of the absorption cross-section occur at various energies both for the light and for the heavy fragment. The calculation suggests that the structure phenomenon in the 2-3 Mev region of the spectra of the fission neutrons could very possibly be caused by the d-ware giant resonance in the absorption cross-section of the heavy fragments. By using the optical model absorption cross-section and taking a certain temperature distribution, the calculated spectra of the fission neutrons agree well with the experiment in magnitude as well as in position of the structure of the neutron spectra. Thirdly, the fact that the neutrons emitted by the fragments may be anisotopic, would also cause a structure phenomenon in fission neutron spectra; the effect is, however, rather small. Finally, some experiments for further clarification of the problem are proposed.
