GB561816A - Improvements in and relating to magnetic induction accelerators - Google Patents

Abstract

561,816. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 7, 1943, No. 287. Convention date, Jan. 13, 1942. [Class 39 (i)] A magnetic induction accelerator or " betatron " of the kind in which a cyclically varying magnetic field confines electrons or other charged particles in a circular orbit while continuously accelerating them along the orbit, has means for cyclically interposing a target, for example, an X-ray target, in the orbit at times calculated to interrupt the particles after they have been accelerated to high velocity. In one form, electrons from a cathode 28, Fig. 2, describe an orbit in the annular vessel 10 under the influence of conical magnetic poles having laminated tips 13 extending within the central aperture of the vessel. The poles are energized by coils tuned by a series condenser to the frequency of an alternating supply which maintains them in oscillation by coupling coils also wound on the polepieces. A propellershaped target 40 is rotated by a synchronous motor 45, 50 contained in a side arm 48 and energized by the same supply through a phaseshifter. To ensure that the electrons are injected only at the desired point near the zero of the cycle, a control electrode system 29, 30 normally suppressing emission from the cathode is made positive by potential from a peaking transformer coupled to the magnetic coils ; an amplifying circuit embodying a gas-filled relay is described. In a modification, a tungsten target is on a reed vibrated by an electromagnet fed by the supply. If the reed 107, Fig. 6, is furnished with a portion 111 of magnetic material, the electromagnet may be dispensed with as the main magnetic field will cause the reed to vibrate. The phase and amplitude of the vibrations are controlled by a rod 113 bearing on the reed and mounted on a flexible bellows 115 which enables it to be moved in or out. The whole is mounted on a metal cup 109. The wall of the vessel is coated with silver.