Intense superradiant and stimulated-superradiant sources of THz radiation

Abstract

Summary form only given. Superradiant emission (in the sense of Dicke), is the cooperative coherent radiation emission of individual charges that emit in phase with each other. The emitted radiative energy is then proportional to N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (N-the number of emitting charges). When the radiating charges are an accelerated free electron bunch, the condition for superradiant emission is t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> Lt2pi/omega where t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> is the bunch duration and omega is the radiation frequency. Intense superradiant THz radiation emission (over 300 W average power) was demonstrated recently at Thomas Jefferson Lab based on coherent synchrotron radiation (CSR) from a bending magnet. We have studied schemes for enhancing the performance of superradiant radiation sources at high frequency and high power levels with compact moderate energy RF-electron guns. High frequency (1 THz) superradiant emission is possible even with bunches near 1 ps, in violation of the condition, if the electrons energy in the bunch is correlated with injection time (energy chirped). Substantial enhancement of the power emission and spectral narrowing is also possible if the emission of radiation takes place in a resonator (stimulated-superradiance). Examples of realizable designs of superradiant and stimulated superradiant sources of THz radiation based on undulator radiation schemes will be presented and qualified