GB466836A - Improvements in and relating to apparatus for producing electron streams of great energy - Google Patents

Abstract

466,836. Electromagnets. SIEMENS-SCHUCKERTWERKE AKT.-GES. March 5, 1936, No. 6725. Convention date, March 6, 1935. [Class 35] [Also in Group XL] Apparatus for producing electron streams of great energy comprises a varying accelerating magnetic flux #, Fig. 1, about which the electrons are accelerated in a circular path R; and a guiding magnetic field Hf coaxial with the accelerating field, which maintains the electron movement in the path R. To do this, the guiding field must vary with and be equal to half the mean value of the accelerating field. Further, to stabilize the electron path for small axial and radial disturbances, the guiding field must decrease outwardly from the centre, proportionally to an inverse power of the radius which is not more than 1 and preferably is equal to ¢. The two fields are produced by the same winding W excited by alternating current at 50 or 500 cycles per second, suitable air gaps being provided to maintain proportionality. Fig. 3 shows a single pair of polepieces shaped to produce both fields, the main part of the pole faces being produced by rotating hyperbolas 1, 2 about the axis a. The accelerating flux is strengthened to the required value by projecting portions A, B at the centre. The diameter of the electron path is made equal to the focal separation of the hyperbolas. To reduce leakage fields, the air gap between A and B may be divided into a number of gaps separated by magnetic material and possibly filled with non-magnetic material or the gaps may be filled with permeable material such as is used for " dust cores." The outer parts of the core may be dispensed with, any deviation from the hyperbolic law being compensated by reducing the separation of the boundaries of the core. The maintenance of the rotational symmetry of the fields is secured by design of the core laminations, which may be involute strips, bundles of wire or spirally wound sheets. The central space of the involute laminations may be filled with wire or spirals, high insulation being used in the spiral type to withstand the induced voltages. Permalloy or other high permeability alloy is preferably used. The return circuits for the magnetic flux should also be symmetrical, at least two side yokes being provided, with air-gaps adjustable to obtain exact symmetry. Fig: 10 shows an arrangement in which the accelerating flux # passes through a central core, while the guiding field comes from ring-shaped polepieces P provided with constrictions A. As the magnetizing current increases, the portions A become saturated and the lines of force are deflected into the central polepiece. The resultant weakening of the guiding field relatively to the accelerating field causes the electron ring to expand and burst. An additional field coil W is wound onto the central polepiece to enable faults of design to be corrected. A central powder core L is provided.