A calibration device for low-energy electrons

An iron-free, low-energy charged particle magnetic spectrometer is designed using a Helmholtz coil geometry. Through the fringe fields of the coils, the spectrometer provides a focus in both the dispersive and non-dispersive planes. By choosing the optimal bend angle and the positions of the source and the focal distance, we expect to obtain an energy resolution of order 1% and an absolute calibration of 0.1%.