Vol. 17, No. 8 (1961)
1961-04-20
CONTENT
1961, 17 (8): 9-33.
doi: 10.7498/aps.17.9
Abstract +
This paper incends to give a comprehensive survey of the high encrgy nuckar interactions produced in emulsions and cloud chambers by particles of an energy in the range 1011 to 1014 cV. The more difficult problems of measurement, such as determination of the primary energy, identification of the secondary particles and estimation of the target mass, are first brought up for discussion. Effort has been made to explain whenever possible the physical meaning of the quantities, which may give information concerning the collision mechanism and hence the internal structure of the colliding particles. The main quantities or these arc the angular distribution, the transverse momentum and the inelasticity, in addition to the multiplicities of the different kinds of the secondary particles. For these quantities, the principle of measurement, the accuracy of experiment and the meaning of the results, particularly the latter, have been emphazised and discussed in some detail. Finally, the various models of the "one emitting centre" and of the "two emitting centres" arc discussed entirely from the physical point of view and are compared with the experimental results. It is hoped that this paper may present a general picture of the recent development of the high energy nuclear interactions and indicate the problems siill remained to be sclved.
1961, 17 (8): 34-40.
doi: 10.7498/aps.17.34
Abstract +
Experiments were made on the growth of copper and iron whiskers by means of vapour reduction. The mechanism of growth was studied in order to find out the effective procedures of growing thick and long whiskers with very high strength. The growth of whiskers was found to be facilitated when the crystal structure of the grow-boat material is similar to that of the whisker. This led to the conclusion that the growth of whiskers is through a mechanism involving an axial screw dislocation. On the basis of observations on the mode of distribution and the direction of growth of the copper and iron whiskers grown on the wall of the boat, it was concluded that the growth of these whiskers proceeded from the tip. Furthermore, experiments showed that the cuprous (or ferrous) chloride vapour was preferentially reduced by hydrogen at the tip of the whisker, presumably because of the catalyzing action of the surface step produced at the tip by a screw dislocation.Observations on the growth of thick copper whiskers with a diameter of 50-120 microns revealed laminar growth, growth in piling up forms and in layers. Such peculiar growth behavior may possibly be associated with an alternation of one-dimensional and two-dimensional nucleation and growth. The possibility of growing a piece of bulk crystal essentially free from dislocations by suitably selecting and controlling the condition and mode of growth was discussed.
