GB646197A - Improvements in and relating to magnetic induction accelerators - Google Patents

Abstract

646,197. Magnetic induction accelerators. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 13, 1946, No. 27587. Convention date, Sept. 15, 1945. [Class 39 (i)] A magnetic induction accelerator used for example to produce X-rays has a unidirectional biasing magnetic field associated with the alternating field, and the electrons are injected at or near the instant 30 when the resultant field 26 rises through zero. The electrons are then accelerated over a longer period each cycle than in the absence of bias, when the electrons are injected at the point 25. A unidirectional current may be superimposed on the alternating current in the field coils, 32, 33, Fig. 7, or may be supplied to a separate set of windings, both sets having a greater diameter than the annular chamber in which the electrons circulate. The unidirectional flux is required only at the electron orbit and undesired unidirectional flux through the central part of the magnetic core may be reduced or eliminated by coils 36, 37 of lesser diameter than the annular chamber and located in grooves in the magnetic core. A laminated core member 38 is provided between the pole-pieces 10, 11 to avoid stray magnetic fields in the region of the chamber. The coils 36, 37 may receive direct current from the same source as the coils 32, 33, a filter circuit blocking the alternating current from the coils 36, 37, or the ratio of turns of the coils 36, 37 to the coils 32, 33 may be chosen to eliminate the alternating current. In this case, however, the compensation for alternating current flowing through the coils 36, 37 may cause an excess of compensating unidirectional flux. This is made to byepass the coils 36, 37 by providing a bleeder circuit. The ratio of the alternating fluxes of the sets of coils 32, 33 and 36, 37 may be chosen to satisfy the 1: 2 conditions, thus making possible the elimination of the air gaps in the central core. The unidirectional current to the coils 36, 37 may be varied to saturate the core and so contract the orbit for the electrons to strike a target. Specifications 574,812 and 585,992 are referred to.