Radiation signatures from an external relativist electron beam

Abstract

X-band radiation has been observed which occurs when an electron beam travelling in air traverses an aluminum plate. The radiation pattern is more complicated than can be explained with a simplified model of Cerenkov radiation from air and transition radiation from the aluminum-air interface. The empirical observation is that the peak angle decreases with energy until about 70 MeV, then increases with energy. The angular width of the peak distribution shows a similar behavior with energy. The observed peak angle decreases as the distance from the horn antenna to the aluminum foil is increased. The explanation of the radiation distribution observed is not yet satisfactory. A major improvement in the data accumulation process has been introduced by measuring radiation at a fixed angle as data is taken with a movable horn. This procedure allows us to compensate for the fluctuating electron beam intensity. The data can now be digitized and stored in a computer for analysis. Previous experiments allowed only for analog measurements. Further work, both theoretical and experimental, will be required to understand fully the radiation signature of the electron beam. Keywords: Cerenkov radiation; Transition radiation; Normalization. Theses. (JHD)