Linear Theory Of Transvertron Microwave Sources

Brendan B Godfrey; Donald J. Sullivan; M. Joseph Arman; Thomas C. Genoni; John E. Walsh

doi:10.1117/12.951784

25 July 1989 Linear Theory Of Transvertron Microwave Sources

Brendan B Godfrey, Donald J. Sullivan, M. Joseph Arman, Thomas C. Genoni, John E. Walsh

Proceedings Volume 1061, Microwave and Particle Beam Sources and Directed Energy Concepts; (1989) https://doi.org/10.1117/12.951784
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

Abstract

Theory and simulations predict that an intense relativistic electron beam can generate high power microwaves simply by propagating axially through a pillbox cavity of appropriate dimensions. Basically, the beam is deflected sideways by the magnetic field of a TMmn1 cavity mode and then exchanges energy with the mode in proportion to J⊥•E⊥ and to JzΔ⊥Ez•X⊥ The microwave energy grows or damps depending on the beam transit time, T, across the cavity. Maximum growth generally occurs for Wmn1T ≈ (ℓ + 1/2)π for an unmagnetized beam, ℓ an odd integer. Results are qualitatively similar but more complicated when an axial magnetic field is present. Beam bunching plays a minor role, at least linearly, and particle reflections do not occur. Thus, this new device is not related closely to the vircator or the monotron. Several distinct realizations of this basic mechanism can be imagined, depending on the beam cross section, the cavity mode excited, and the magnetic guide field strength. The case of an unmagnetized annular electron beam propagating near the cavity wall and interacting with a TM011 mode is discussed extensively in a companion paper. A solid beam near the cavity axis interacting with a TM111 mode in a moderate applied magnetic field is an interesting alternative; it resembles a compact Gyrocon, a device known for high efficiency. Configurations analogous to single cavity Scantrons also are feasible, although they appear to have lower gain than the previous examples. These results also may be relevant to optimization of other microwave sources and to the beam breakup instability in high current accelerators.

Citation Download Citation

Brendan B Godfrey, Donald J. Sullivan, M. Joseph Arman, Thomas C. Genoni, and John E. Walsh "Linear Theory Of Transvertron Microwave Sources", Proc. SPIE 1061, Microwave and Particle Beam Sources and Directed Energy Concepts, (25 July 1989); https://doi.org/10.1117/12.951784

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