Emittance Measurement of Axisymmetric High-Current Electron Beam Confined by a Longitudinal Magnetic Field

Abstract

We propose a method for emittance measurement of an axisymmetric high-current electron beam confined by a longitudinal magnetic field. In this method, the beam current is measured by a multi-layer Faraday cup to obtain the radial beam current profile using Abel inversion. Based on the theory of a beam in a uniform focusing channel, the transverse electron temperature is uniquely defined by the shape of the current density profile. Therefore, measuring the current density profile enables the determination of the beam emittance. Because the method does not require to use slits, the measurement has been markedly simplified. The method has been adopted to a test beam. The emittance is found to be 20.2π mm·mrad, which basically agrees with that obtained by a slit-slit method.