Statistical fluctuations of cooperative radiation produced by nonisochronous electrons-oscillators

Abstract

Shot noise, intrinsic to the ensemble of nonisochronous electrons-oscillators, is the cause of statistical fluctuations in cooperative radiation generated by single-pass cyclotron-resonance masers (CRMs). Autophasing time — the time required for the cooperative radiation power to peak — is the critical parameter characterizing the dynamics of electrons-oscillators interacting via the radiation field. Shot-noise related fluctuations of the autophasing time imposes appreciable limitations on the possibility of coherent summation of electromagnetic oscillations from several single-pass CRMs. Premodulation of charged particles leads to a considerable narrowing of the autophasing time distribution function. When the number of particles Ne exceeds a certain value that depends on the degree to which the particles have been premodulated, the relative root-mean-square deviation (RMSD) of the autophasing time δT changes from a logarithmic dependence on Ne (δT ∼ 1/ ln Ne) to square-root (δT ∼ 1/ √ Ne). As a result, there is an increased probability of coherent summation of electromagnetic oscillations from several single-pass generators. A slight energy spread (∼4%) results in a twofold drop of the maximum attainable power of cooperative radiation.