Abstract
For electron injection into a betatron acceleration tube, there are an optimum angle of inci-dence and optimum position of electron gun to render the amplitude of electron osillation to a. minimum. In general, the oscillation amplitude of tangentially incident electrons becomes smaller as the field bumps are smaller, their phase angle in nearer π/2 and the voltage of incident elect-rons is higher. Hence, with a Kerst type magnet, the maximum X-ray output is easily obtained by placing the electron gun right under the magnet yoke, whereby the optimum angle of electron incidence becomes independent of the voltage of incident electrons and excitation current of the magnet. On the assumption that the X-ray output is proportional to he reciprocal of electron oscillation amplitude, the relation between the angle of electron incidence and the X-ray output can be explained.
