Abstract

When an electron beam traverses the interface between two media with different dielectric constants, the so called transition radiation are generation [1]. In a periodic structure with multiple interfaces, the radiation is greatly enhanced around a spatial region in a conical pattern for certain wavelength. In previous research [1,2] structures with the thickness of each layer is much longer than the wavelength are used. As a result, ultra-relativistic electrons with energies 100 Mev to 50 Gev [2] are required. However, with advent of new technologies, periodic multilayer structures can be constructed with a spatial period less then 100 Å. The generation of soft x rays with a low-energy electron beam that passes through such a multilayer structure was recently proposed [3]. In solid-state structures, the losses due to photoabsorption, and electron scattering may be the main obstacles in x-ray generation with these structures. We showed [4] that the energy of the electron beam from ~ 200 Kev to a few Mev is sufficient to compensate for the loss due to electron scattering. We further demonstrated that above the electron energy of ~ 200 Kev for most of the materials radiating soft x-ray frequency range, the photoabsorption is the limiting factor and electron scattering can be neglected. The phtotoabsorption imposes an energy “ceiling” above which further increase in beam energy is rewarded with diminishing radiation. Based on these results, we prescribe the optimal geometric configuration for maximum radiation from multilayer structures composed of certain materials at certain frequency and electron beam energy.

© 1992 Optical Society of America