| 摘要 |
931,808. Travelling-wave tubes. PHILIPS ELECTRICAL INDUSTRIES Ltd. Nov. 11, 1959 [Nov. 14, 1958], No. 38233/59. Class 39 (1). A magnetic focusing system for a travelling- wave tube comprises an elongated permanentmagnet body 1, 2, 3, Fig. 1, of material having a high saturation induction and a low coercive field strength H, magnetized longitudinally and hollow to accommodate the tube; the magnetic field in the hollow interior is not more than H; each end of the body is provided with a soft-iron polepiece 4, 5; within each polepiece is located a ring 6, 7 of a magnetic material having a remanent induction B not more than 4 times H; and the rings are magnetized radially so as to intensify the magnetic field at the ends. Preferably 6 has twice the axial length of 7. A stack of rings of alternate high-permeability soft magnetic material 9 and hard paper 8 is provided inside the hollow magnet for homogenizing the field. |
