FIGURE 4.1 Refraction and periodic focusing of a particle beam at a plasma boundary. Courtesy of T. Katsouleas, University of Southern California.

full array of phenomena associated with HED beam-plasma interactions is not the intent of this report, but the committee believes that the information provided will give the reader some idea of the wealth of phenomena associated with beams in plasmas. Then, in the secion on applications of HED beam-plasma physics, three applications are described rather extensively, followed by coverage of seven other applications. The final section discusses the opportunities for furthering this field, both experimentally and theoretically/computationally.

The intellectual theme of this chapter can be gleaned from the following list of illustrative questions of high intellectual value:

• At what intensities does dense matter become transparent? At what intensities does vacuum become opaque?