Application of magnetic field for improvement of energy spread of an electron beam

Electron diffraction is not solely a powerful method to study fundamental physics but has also been applied to quantum sensors. A low-coherence electron source results in a drop of fringe contrast. One approach to enhance a visibility of the diffraction pattern is to improve a longitudinal coherence of an electron beam. When electrons pass through a magnetic field, they experience a force which bends them to circular paths. Electrons with different energies will travel along the different paths. By placing a slit behind the magnetic field, the width of the electron energy distribution will become narrower and hence an improvement of the beam coherence. However, this method reduces the intensity of the electron beam. The simulation was performed to optimize the slit width for electron diffraction experiments with respect to the energy spread of the beam and electron flux.