Collective-interaction control and reduction of optical frequency shot noise in charged-particle beams.

We present a theoretical model for longitudinal collective Coulomb interactions in a charged-particle beam. It suggests a possibility to control and reduce optical frequency shot-noise current in accelerated electron beams. For short interaction lengths, the model describes well coherent optical transition radiation effects observed in SLAC LCLS and in other laboratories. For longer interaction lengths (quarter plasma oscillation period) the model predicts the possibility to reduce the beam current noise below the classical shot-noise level, an effect not yet observed experimentally at optical frequencies.