The Frequency Spectrum and Energy Content in a Pulse Flux of Terahertz Radiation Generated by a Relativistic Electron Beam in a Plasma Column with Different Density Distributions

Abstract

This paper reports on the generation of a directed flux of electromagnetic radiation with an energy content of 10 J in the frequency range of 0.2–0.3 THz at a microsecond pulse duration in a beam–plasma system. The flux is generated when a relativistic electron beam (REB) pumps electron plasma waves in a magnetized plasma column. In the described experiments, this fundamentally new approach to generate terahertz radiation was carried out at the GOL-PET facility in the conditions of varying the beam current density and the plasma density in the appropriate ranges of 1–2 kA/cm² and 10¹⁴–10¹⁵ cm^–3. From the comparison of the flux energy spectrum measured experimentally in the frequency range 0.15–0.45 THz with the calculated one obtained using the previously proposed model of radiation generation in a beam–plasma system it was shown that this process occurs through resonant pumping by REB of precisely the branch of upper-hybrid plasma waves. Mastering this new method to generate terahertz radiation opens the prospect of its use to obtain multi-megawatt radiation fluxes in the frequency range up to 1 terahertz and higher. For such a development approach the most promising beam for pumping plasma oscillations seems to be a kiloampere REB generated in a linear induction accelerator.