The possibility of using superconducting pulsed magnet for high energy physics has been studied in many laboratories around the world. Problems and requirements of the pulsed magnets tested in those laboratories are reviewed in conjunction with conductors developed for them. Most serious problems involved in the pulsed magnets are degradation and training effects. Brief reviews on AC losses and stability are also given. Design requirements of the conductors for the pulsed magnets are considered in terms of several parameters, such as number of filaments, diameter, Cu/SC ratio, alloy compositions and twist pitch. Since requirements of the conductors for high stability and low AC losses are conflicting, some of the parameters are optimized.
The dynamic behavior of liquid helium in a glass dewar (7cm i.d. and 74cm length) rigidly set on the vertically vibrating shake table was observed. The shake table was excited at amplitudes of 4, 10, and 20mm, and at frequencies up to 500cpm. The increased loss rate due to the vibration, which depended on the amplitude and frequency of the excitation and the depth of liquid in the dewar, was about 0.1W at most in this experiment. The amplitude of the liquid motion was increased at the resonant frequency, but had no corrlation with the magnitude of the loss rate. The vibration losses were considered to be caused by the enhancement of convective heat transfer in a vapour column above the liquid.
A simple NMR marginal oscillator with a single MOSFET has been improved by incorporating an amplifier with additional MOSFET; the main part (cryogenic box) is immersed in liquid N2 or He and is put between the pole pieces of an electromagnet. The influence of static magnetic field upon the characteristics of the commercial MOSFET element was studied and the element was found to work well at low temperatures under magnetic fields up to 20.1kG. The stationary NMR measurements of Al27 nucleus in ruby crystal were carried out over the temperature range 1.5-300K by using the built-in NMR apparatus; in particular, the temperature dependence of the NMR linewidth was measured in this work.
This paper presents the construction and operational characteristics of the experimental apparatus of MHD rotating machine with superconducting rotor, which has the electromechanical energy conversion function based on the inductive interactions between travelling magnetic field produced by the rotor and MHD working fluid. The machine consists of a rotating-dewar type superconducting rotor and a coaxially rotating metal cylinder which simulates the liquid metal MHD working fluid, and both of them are driven separately by speed-controlled driving motors. The superconducting magnets installed in the rotor has the 8 shaped winding whose outer diameter is 11cm and hight is 11cm, and with the excitation current of 200A (rating), it produces screw type magnetic field in the inductive interaction region of the cylinder with the peak value of 0.2Wb/m2, whereas the avarage field strength reaches almost 4Wb/m2 inside the winding. In this condition, mutual interaction force is 30N in the peripheral direction and 8N in the axial direction and the total driving power of motors is 1, 300W when the relative rotation speed of the rotor and the cylinder is 800rpm. Observed characteristics of this machine are for the most part in agreement with those estimated by the theoretical analysis.
Maximum current of a superconducting magnet is restricted by maximum magnetic field. Therefore current density in low magnetic field regions becomes much smaller than critical current density in those magnetic field. This means that the superconductors are used inefficiently. A most simple way to use the superconductors more efficiently is to divid the magnet into several components according to their magnetic field strength. A principle of deviding method to minimize the winding volume of the superconducting magnet is described on the basis some approximation.