Energy Content and Spectral Composition of a 5-µs-Long Flux of Submillimeter Radiation Generated in Plasma during REB Relaxation

In Budker Institute of Nuclear Physics (BINP), experimental and theoretical studies of generation of submillimeter electromagnetic radiation with characteristic frequencies 0.1–0.5 THz under conditions of intense plasma–beam interaction are carried out. Generation of radiation occurs in the specialized G-OL‑PET facility during collective relaxation of pulsed relativistic electron beam (REB) with the following parameters: electron energy 0.6 MeV, beam current 15 kA, and pulse duration 5 µs in a plasma column with plasma density (0.5–1) × 10 15 cm –3 , under conditions of its confinement in a vacuum chamber with a corrugated magnetic field (the ratio of the maximum and minimum values of magnetic induction in the corrugations is B max / B min = 4.5/3.2 T). An important feature of the carried out studies is the presence of specifically created inhomogeneities both in its cross section and along its length. In experiments carried out earlier under the same conditions, a high level of power (about 10 MW) was reached in the flux of submillimeter radiation going out into the atmosphere. Radiation energy of 7 J was reached at pulse duration of 0.5 µs, which is limited by the high-frequency breakdown at the vacuum side of the output window. This article is devoted to the problem of increasing the duration of the pulse of generated submillimeter radiation of such a high power. This is attained by suppressing high-frequency (HF) breakdown near the surface of the window through which the radiation flux is going out into the atmosphere and by increasing the duration of megavolt radiation pulse applied to the accelerator diode in which REB is generated.