A compact high-energy electron radiography system based on active plasma lenses

We propose a compact high-energy electron radiography scheme based on a compact imaging lens composed of an active plasma lens [1] with a weak chromatic dependency to realize a point-to-point focus. The system consists of a 50MeV electron linear accelerator coupled to a 3cm-long capillary to provide a magnification of 20. The transfer matrix of active plasma lenses has been derived, which is a simple way to design an imaging system. In addition, the entire imaging columns magnify the sample by the magnification of less than 45cm. Validity of the imaging lens system is confirmed by the particle tracking code GPT [2] and three-dimensional particle-in-cell code IBMP [3]. Line spread function (i.e., the differential of the intensity projection) and its Gaussian fit of the simulation result indicate a resolution of $1 \mu \mathrm{m}$ on the image plane. Furthermore, the factors affecting spatial resolution have been discussed and an experimental plan for a cascaded imaging system has been given.