Slow-wave electron cyclotron maser

Kho, T. H.; Lin, A. T.

doi:10.1103/physreva.38.2883

Cited by 37 publications

(7 citation statements)

References 9 publications

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“…In addition, application is restricted to a cold mono-energetic particle distribution only. Extensions have been given to loss-cone distributions by Lau and Chu (1983) and to spiraling magnetic-field aligned electron beams by Kho and Lin (1988).…”

Section: Phase Space Bunching Mechanismmentioning

confidence: 99%

“…Whether the amplified slow wave can escape from the plasma is a different one and -is difficult to answer. Analytical and numerical calculations have been presented by Kho and Lin (1988) for the slow wave in a field-aligned beam plasma system and γ 0 = 2, ω ce = 2ω pe finding a strong instability. It seems that the slow wave can be more easily be made unstable when a beam along the magnetic field is present in the plasma.…”

Section: Radiation and Absorption In Bunchingmentioning

confidence: 99%

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The electron–cyclotron maser for astrophysical application

Treumann

2006

Astron Astrophys Rev

379

383

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The electron-cyclotron maser is a process that generates coherent radiation from plasma. In the last two decades, it has gained increasing attention as a dominant mechanism of producing high-power radiation in natural hightemperature magnetized plasmas. Originally proposed as a somewhat exotic idea and subsequently applied to include non-relativistic plasmas, the electroncyclotron maser was considered as an alternative to turbulent though coherent wave-wave interaction which results in radio emission. However, when it was recognized that weak relativistic corrections had to be taken into account in the radiation process, the importance of the electron-cyclotron maser rose to the recognition it deserves. Here we review the theory and application of the electron-cyclotron maser to the directly accessible plasmas in our immediate terrestrial and planetary environments. In situ access to the radiating plasmas has turned out to be crucial in identifying the conditions under which the electron-cyclotron maser mechanism is working. Under extreme astrophysical conditions, radiation from plasmas may provide a major energy loss; however, for generating the powerful radiation in which the electron-cyclotron maser mechanism is capable, the plasma must be in a state where release of susceptible amounts of energy in the form of radiation is favorable. Such conditions are realized when the plasma is unable to digest the available free energy that is imposed from outside and stored in its particle distribution. The lack of dissipative processes is a common property of collisionless plasmas. When, in addition, the plasma density becomes so low that the amount of free energy per particle is large, direct emission becomes favorable. This can be expressed as negative absorption of the plasma which, like in conventional masers, leads to coherent emission even though no quantum correlations are involved. The physical basis of this formal analogy between a quantum maser and the electron-cyclotron maser is that in the electron-cyclotron maser the free-space radiation modes can be amplified directly. Several models have been proposed for such a process. The most famous one is the so-called loss-cone maser. However, as argued in this review, the loss-cone maser is rather inefficient. Available in situ measurements indicate that the loss-cone maser plays only a minor role. Instead, the main source for any strong electron-cyclotron maser is found in the presence of a magnetic-field-aligned electric potential drop which has several effects: (1) it dilutes the local plasma to such an extent that the plasma enters the regime in which the electron-cyclotron maser becomes effective; (2) it generates energetic relativistic electron beams and field-aligned currents; (3) it deforms, together with the magnetic mirror force, the electron distribution function, thereby mimicking a high energy level sufficiently far above the Maxwellian ground state of an equilibrium plasma; (4) it favors emission in the freespace RX mode in a direction roughl...

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Section: Phase Space Bunching Mechanismmentioning

confidence: 99%

Section: Radiation and Absorption In Bunchingmentioning

confidence: 99%

The electron–cyclotron maser for astrophysical application

Treumann

2006

Astron Astrophys Rev

379

383

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“…Kho and Lin [33] analyzed an invariant of motion of a single electron in fast and slow EM waves without using linear approximation. Their results showed that, in fast wave devices, the EM field obtains energy only from of the electrons.…”

Section: Discussionmentioning

confidence: 99%

Linear dispersion relation of backward-wave oscillators with finite-strength axial magnetic field

Minami

Saito

Choyal

et al. 2002

IEEE Trans. Plasma Sci.

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The linear dispersion relation of backward wave oscillators (BWOs) with finite strength axial magnetic field is derived and calculated numerically. Axisymmetric mode radiation in a slow wave structure (SWS) with corrugated metal wall including a column of relativistic electron beam streaming along the lines of a finite strength axial magnetic field is analyzed. Three theoretical achievements [viz. 1) the dielectric tensor derived by Bogdankevich et al., 2) the formulation of EM waves in the beam column that are expressed as a linear combination of extraordinary and ordinary modes elucidated by Antonsen et al., and 3) a consideration of boundary conditions in the beam-SWS system initiated by Swegle et al. ] are combined in our numerical code to be exact and universal under the scope of linear treatment. Our dispersion relation can include effects of interaction between a structure mode and electron cyclotron modes in addition to conventional beam space charge modes. Numerical analysis is carried out using the parameters of a BWO experiment at the University of Maryland. The results show the well-known cyclotron absorption of radiation from the BWO at a particular value of magnetic field that was previously analyzed in various ways different from ours.Index Terms-Absolute instability, backward-wave oscillators (BWOs), dielectric tensor, electron cyclotron mode, high-power microwave, slow-wave structure (SWS).

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“…Note that the operation of CRMs when both the Cherenkov and anomalous Doppler cyclotron resonance conditions take place simultaneously have been studied in [23]- [25]. (The case of the cyclotron resonance under the anomalous Doppler effect is often called the cyclotron Cherenkov resonance.)…”

Section: Introductionmentioning

confidence: 99%

Combined Resonances in Cyclotron Masers With Periodic Slow-Wave Structures

Nusinovich

Zhao

2015

IEEE Trans. Plasma Sci.

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It is shown that electrons moving along helical trajectories in an external uniform magnetic field and propagating in periodic slow-wave circuits can simultaneously interact with several space harmonics of such waves. The linear theory describing combined resonances in such systems is developed. Our treatment is limited by consideration of four resonances: 1) two cyclotron resonances at the fundamental and second cyclotron harmonics; 2) the Cherenkov resonance at the zero space and zero cyclotron harmonics; and 3) the cyclotron resonance under the anomalous Doppler effect condition at the minus first cyclotron harmonic. It is shown that the growth rate and the bandwidth in the cases of such a combined resonance, in which the dominant role is, as a rule, played by the cyclotron resonance at the fundamental and the Cherenkov resonance, can be much larger than in the case of single resonances.

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Slow-wave electron cyclotron maser

Cited by 37 publications

References 9 publications

The electron–cyclotron maser for astrophysical application

The electron–cyclotron maser for astrophysical application

Linear dispersion relation of backward-wave oscillators with finite-strength axial magnetic field

Combined Resonances in Cyclotron Masers With Periodic Slow-Wave Structures

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