Gyrotron multistage depressed collector based on E × B drift concept using azimuthal electric field. II: Upgraded designs

Abstract

Multistage Depressed Collectors (MDCs) are nontrivial for high-frequency gyrotrons. A basic conceptual design of an E Â B MDC using azimuthal electric fields was proposed in Part I of this series. In the present work, several upgraded design proposals based on the basic one will be elaborated. These proposals will significantly reduce the back-stream of electrons, which was the main drawback of the basic design proposal. Another upgraded design proposal will shrink the length and maximal radius of the MDC to be only a fraction of its full-length version. A conceptual design of the final MDC proposal will be given at the end.Published under license by AIP Publishing. https://doi.

Coaxial multistage depressed collector design for high power gyrotrons based on E×B concept

“…The size of the collector can be significantly decreased by a folded helical gap as was also proposed in Ref. 11 . The regions of an inward and outward drift are split into more regions with a smaller azimuthal section for each fragment.…”

“…That cannot be achieved with a conventional SDC system. For that purpose, a systematic investigation of the design of multistage depressed collector (MDC) systems for fusion gyrotrons is ongoing at KIT [5][6][7][8][9][10][11] .…”

“…Since then, three different types of MDC designs have been suggested for annular gyrotron electron beams based on the E×B drift. The first type is based on the transformation of the annular beam to a sheet beam 6,9 , the second type consists of the application of an azimuthal magnetic field on the annular beam 15,16 and the third one is based on utilizing an azimuthal electric field 5,10,11 .…”

Development of multistage energy recovery system for gyrotrons

“…The further increase of total efficiency is possible with implementation of multistage systems of energy recovery. Such systems have to separate the electron beam on fractions with different energy of electrons and provide deposition of these fractions on sections under different potentials [4][5][6][7][8][9]. The magnetic induction in the collector region of gyrotrons is noticeably less than in the resonator.…”

“…In order to achieve recovery of electron energy in a multistage depressed collector, a method of separation of electrons with different energy should be realized. A new approach to separation of electrons, based on their radial drift in the crossed electric and magnetic fields, was studied by several research groups (for example, [5][6][7][8][9]). The authors of this paper proposed to use the axial electric field and the azimuthal magnetic field with the aim of providing effective separation of electrons.…”