The article gives a fairly extensive review of the available literature about low-H magnetic shielding. Beginning with ferromagnetic cylindrical shieldings, the theoretical design equations for transversal and longitudinal DC and low frequency (_??_1MHZ) AC fields, inclusive leakage fields from the ends, are presented, disussed and compared with actually designed shields. Experimental procedures (demagnetization and shaking), which help to raise the shielding ratio together with limits and problems of such shieldings are listed. Superconducting shielding is covered in three sections: stationary, rotating, and expanding (balloon-type) shieldings, and again, a survey of results achieved and limits of superconducting shieldings are presented. Finally, a short section covers the main features of active shielding with degaussing coils. An appendix outlines methods of shielding against strong fields and shortly discusses conventional low-H magnetometers. A list of the major literature is added.
The situation of researches and developments of high speed transport systems in Germany is presented. In Germany, many efforts are devoted to the development of magnetically levitated-linear motor driven-high speed transport systems. Two methods are now considered for the magnetic levitation. One is the electro-magnetic method utilizing magnetic attractive force between electro-magnet and iron track. Another is the electro-dynamic method utilizing magnetic repulsive force between superconduting coil and conductive sheet track. The system of practical train will be decided according to the test results of both methods at 75km test track. This new high speed transport system will connect München and Humburg in near future.
In order to mvestigate the mechanisms determing critical current densities in practically used superconducting alloys, Jc-T-H characteristics of Nb-60 at % Ti alloy were measured. Specimens were prepared as the copper clad wires of 0.25mm in diameter, and were aged for various times at 350°C-400°C. The results of measurments on heat-treated specimens show that the precipitates on dislocation network are important as the pinning centers, and the temperature and the field dependence of critical current densities are established in early stage of annealing. The scaling rules for the pinning force densities assume the form Fp∝Hc2(T)n(B/Hc2)p(1-B/Hc2)q, where n≅5/2, p_??_1, and q≅2 for annealed specimens.
A survey of researches on persistent current switches for superconducting magnets is presented. Basic principles and methods of persistent current switches are given. General characteristics and some problems of thermal type and mechanical type persistent current switches are described including off-state resistance, on-state resistance, stability of switch-superconductor, responce time and consumption of liquid He. Some examples of these switches are given.