exception to this situation, since they would be unaffected by the Earth’s magnetic field, are not subject to "self-dispersion” effects, and can be directed with small divergence angles. Such beams can be produced by accelerating negatively charged beams (e.g., H ) to energies of over 250 MeV and then "stripping" the extra electron after acceleration. Unlike the endoatmospheric PBW concepts, which typically require pulsed, high-intensity beams, the exoatmospheric neutral beam concept in its present state of conceptual development is based on a rather lower intensity beam that must dwell on the target for some longer period of time. Components of a typical conceptual system (Figure C.2-1) include target acquisition and tracking, beam position, and damage assessment inputs to some overall fire-control function; the charged-beam generator, which includes power, beam injection, and particle acceleration subunits; and beam steering and neutralization functions. The angular dispersion of the neutralized beam, principally determined by the neutralizer, is a critical parameter because of its effects on the lethality characteristics of the system. Basic parameters (based solely on basic physics considerations) for a nominal particle beam weapon are shown in Table C.2-1. Table C.2-1 Nominal PBW Parameter Summary Beam Particle Energy 250 MeV protons Beam Current 100 milliamperes Beam Power 25 MW Prime Power about 50 MW Accelerator Length 50-75 meters C.2.2 Basic Exoatmospheric PBW Lethality Considerations Because of the difference in exo- and endoatmospheric propagation mechanisms, it appears unlikely that ground-to-space or space-to-ground attacks can be mounted. A neutral beam—the most feasible space propagation mode—will rapidly disperse upon encountering a significant amount of atmosphere; and an intense,
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