The neutron thermopile is a excellent neutron flux detector and has many better points than the chamber type has. However, the fact that its action is accompanied by time lag is fatal to it. Furthermore, because of its various defects, that is, disturbance signal induced by ambient temperature change and damage of junctions resulting from neutron irradiation, it has not been used in the past for the purpose of direct control and major safety of the reactor. It was used only for safety back up and monitoring in the reactor. In this point of view, the author and his co-operators have studied on how to apply the neutron thermopile for control and safety of the nuclear reactor, that is, as follows: (a) the method for compensating time lag resulting from its responsive action by using the time constant compensating circuit. (b) the method for preventing the induction of the disturbance signal caused by a change in ambient temperature. (c) the method for calibrating changes in the characteristics of the junctions by making use of Peltier's effect. As the results, these methods have been enabled to serve the practical purpose. Thus, it can be thought that the neutron thermopile should be used as the major instrumentation designed for the direct control and major safety of the reactor.
Lattice vibrations of ideal wurtzite were formulated by a point dipole model taking account of valence type short range interactions up to third neighbors. Explicit expressions were given for Γ-point frequencies and electroelastic constants by the method of long wave. Sum rule for phonon frequencies were derived. Piezoelectric constants were interpreted in terms of mechanical, electronic and cross-coupling contributions, and the extreme ambiguity of its theoretical calcu-lation was pointed out. Preliminary numerical analysis of II-VI compounds shows that the present model is promising for CdS and CdSe in predicting the infrared data and electroelastic properties except piezoelectricity, but the model fails for BeO and ZnO. Coulomb dynamical tensors of ranks two, three and four were calculated and tabulated in Appendix.
By suitably determining the position of the fixed pivotal axis of a previously reported movable tube flowmeter of the angular momentum type, its structure has been simplified. Namely, the pivotal axis is taken through a point on the axis of the straight tube of either the inlet or outlet portion of the movable tube and perpendicular to the tube. Since the measurement of flow rate by such a flowmeter is not affected by any physical quantity at the inlet or outlet end of the tube, the flow rate may be obtained from the quan-tities measured at the other end of the movable tube. The experimental results confirm fairly well this theoretical consideration.
Relations between pluse height and concentration of intermediate solvents in a decalin liquid scintillators have been studied. The intermediate solvents used in this experiment are Naph-thalene and its derivatives. The pulse height at room temperature are shown to increase with concentration of intermediate solvents over the range 0.005M._??_0.1M. But the pulse height at -6°C has shown to increase remarkably with higher concentration of intermediate solvents. Such variations of pulse height may be understood from an analysis of the fluorescence spectrum of excimer of intermediate solvents. The excimer, in general, acts as a quencher. By proper selection of solvents, intermediate solvents, and solutes, intermediate solvents act as a sensitizer in the liquid scintillators. The contribution of the excimer of intermediate solvents are discussed.
We report an experiment on magnetic or magneto-electric annealing effects using a single crystal of (Cr2O3)0.99-(Al2O3)0.01. The transition of antiferromagnetic domain was observed through the measurement of sign and magnitude of the magneto-electric coeffi-cient α. From these experimental results we found that the 180° reversal of all spins could be induced by the electric field when the sample was cooled through N'eel temperature under the applications of magnetic and electric fields. Moreover the threshold value EH which gives the reversal of α' s sign was found to be a constant.