Thermal effects on the efficiency of Doppler-shift dominated cyclotron masers

Lin, A. T.; Wen-Wei, Chang; Lin, Chin-Yuan

doi:10.1063/1.864733

Cited by 14 publications

(4 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The calculation of the pondermotive changes of the edge density in IBW schemes at various frequencies has been carried out by Cardinali et al [13]. The possible excitations of the PDI in the SOL of a tokamak plasma have been studied both in theory [14][15][16][17][18][19][20] and experiment [21][22][23]. These show that the PDI could be an important mechanism for dissipating the nonlinearly trapped wave power in the edge of a plasma, responsible for the lack of penetration of the wave into the plasma interior and for the ineffectiveness of heating the plasma core.…”

Section: Introductionmentioning

confidence: 99%

Observation of parametric decay instability during ion Bernstein wave heating experiments on HT-7

Yang

Zhao

et al. 2001

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

The parametric decay processes with a power threshold of 70 kW have been observed on the HT-7 tokamak. Two types of parametric decay instabilities have been identified. The pump wave decays into an ion cyclotron quasi-mode and an ion Bernstein wave, or decays into a low-frequency electron Landau damped quasi-mode and an ion Bernstein wave. The experimental observation shows good agreement with theoretical prediction. Other peaks at a frequency of n D are also observed. The main features of the observed radiofrequency spectra is due to the parametric decay instability of the launched slow electron plasma pump wave into an ion cyclotron quasi-mode and an electron plasma wave, dominated by plasma inhomogeneity convective loss. As the plasma displacement shifts towards the antenna, a higher ω/ value at the antenna position and a higher wave frequency are used to reduce the possibility of parametric decay instability (PDI) production. The experimental evidence clearly shows that a higher wave frequency, edge density and value of ω/ in the scrap-off layer are favourable to prevent the production of PDIs. The PDI was effectively reduced and successfully avoided with a power level up to 300 kW.

show abstract

Section: Introductionmentioning

confidence: 99%

Observation of parametric decay instability during ion Bernstein wave heating experiments on HT-7

Yang

Zhao

et al. 2001

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…In the relativistic-beam/submillimeter wavelength regime the obvious choice for this output coupling is the gyrotron (Flyagin 1984), quite likely with the doppler-shift dominated version (Lin et al 1984;Lin & Lin 1985). In the relativistic-beam/submillimeter wavelength regime the obvious choice for this output coupling is the gyrotron (Flyagin 1984), quite likely with the doppler-shift dominated version (Lin et al 1984;Lin & Lin 1985).…”

Section: Realizationmentioning

confidence: 99%

“…These devices achieve their output radiation through a coupling of the cyclotron modes of the electron beam with radiation in a resonant electromagnetic cavity, with outputs in the millimeter wavelength region. The possible benefits in frequency scaling, on the other hand, of the "doppler-shift dominated" version (Lin, et al 1984) of the gyrotron can be combined with the benefits of the FEL synchronous harmonic generator to be described below. While the output frequencies and power outputs of gyrotrons might be raised by using quasi-optic resonators (Vomvoridis, et al 1983) (instead of microwave resonators), the requirements for higher (d.c.) magnetic fields are costly.…”

Section: Introductionmentioning

confidence: 99%

The free-electron-laser synchronous harmonic generator—A high power source of submillimeter waves

Cassedy¹

1987

Laser Part. Beams

View full text Add to dashboard Cite

A harmonic generator of submillimeter wavelength radiation, operating on a relativistic electron beam, is proposed. The device is shown to operate on principles of parametric interactions, under the particular conditions of an electric-quadrupole pump field which is propagating synchronously with the electron beam. Using a fluid model, it is shown that a cascade of parametric sum and difference frequencies in the transverse beam modes should occur, with each harmonic component growing convectively along the beam. The physical effect, termed the "sonic condition", has been observed previously on a non-relativistic device emitting output radiation in the UHF range. A realization for relativistic beams is proposed, using an FEL structure as the parametric pump, a closed waveguide synchronous pump region and an output coupling of the gyrotron type. Possible advantages over the present state-of-the-art for high-power submillimeter electron-beam devices are discussed.

show abstract

“…Over the past years there has been great intrest in solar physics in the excitation of direct electromagnetic emission from unstable electron distributions (Twiss and Roberts, 1958;Fung and Yip, 1966;Ramaty, 1969;Mangeney and Veltri, 1976;Stepanov, 1978). Unlike plasma emission (Melrose, 1987), which is a multi-stage process, direct electromagnetic emission is a very efficient process.…”

Section: Introductionmentioning

confidence: 99%

Electron cyclotron maser emission from solar flares

Vlahos

1987

Sol Phys

View full text Add to dashboard Cite

Energetic electrons, with energies 10-100 keV, accelerated during the impulsive phase of solar flares, sometimes encounter increasing magnetic fields as they stream towards the chromosphere. A consequence of the conservation of their magnetic moment is that the electrons with large initial pitch angle will be reflected at different heights from the atmosphere. Energetic electrons reflected below the transition zone will lose most of their energy to collisions and will never return to the corona. Thus, electrons reflected above the transition zone form a loss-cone velocity distribution which can be unstable to Electron Cyclotron Maser (ECM). The interaction of quasi-perpendicular shocks with the ambient coronal plasma will form a 'ring' or 'hollow beam' velocity distribution upstream of the shock. 'Ring' velocity distributions are also unstable to the ECM instability. A review of the recent results on the theory of ECM will be presented. We will focus our discussion on the questions: (a) What are the characteristics of the linear growth rate of the ECM during solar flares? (b) How does the ECM saturate and what is its efficiency? (c) How does the ECM generated radiation modify the flare environment? Finally we will review the outstanding questions in the theory of ECM and we will relate the theoretical predictions to current observations.

show abstract

Thermal effects on the efficiency of Doppler-shift dominated cyclotron masers

Cited by 14 publications

References 10 publications

Observation of parametric decay instability during ion Bernstein wave heating experiments on HT-7

Observation of parametric decay instability during ion Bernstein wave heating experiments on HT-7

The free-electron-laser synchronous harmonic generator—A high power source of submillimeter waves

Electron cyclotron maser emission from solar flares

Contact Info

Product

Resources

About