Emission of Radio-Frequency Waves from Plasmas

Bekefi, G.; Brown, Sanborn C.

doi:10.1119/1.1986484

Cited by 35 publications

(12 citation statements)

References 3 publications

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“…To determine whether this plasma is strongly ionized, the electron density can be estimated using the requirements for opacity [1,2,23,24]. The absolute spectral intensity I λ at wavelength λ can be calculated using [25],…”

Section: Cooling Phase (T > 25 Ns) -Lasting 100s Of Nanoseconds Thismentioning

confidence: 99%

Observation of Shell Structure, Electronic Screening, and Energetic Limiting in Sparks

et al. 2016

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We study the formation of micron-sized spark discharges in high-pressure xenon on the nanosecond time scale. The spark's energy per length is measured through the expansion dynamics of the generated shock wave, and is observed to scale linearly with the spark radius. At the same time, the surface temperature of the spark channel remains constant. Together, these observations allow us to conclude that the spark channel, up to 40 μm in overall radius, is actually an energetically hollow shell about 20 μm thick. Further, the energy per nucleus in the shell is about 15 eV, independent of size and density. To reconcile these findings with the opacity to visible light, we appeal to collective screening processes that dramatically lower the effective ionization potential, allowing a much higher electron density than is otherwise expected. Thus, nanosecond measurements of sparks provide access to the thermodynamics and kinetics of strongly correlated plasmas.

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Section: Cooling Phase (T > 25 Ns) -Lasting 100s Of Nanoseconds Thismentioning

confidence: 99%

Observation of Shell Structure, Electronic Screening, and Energetic Limiting in Sparks

et al. 2016

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“…Unfortunately, as was shown later, Twiss had not included the statistical weights of the electrons correctly. A correct calculation (8) showed that under the circumstances described by Twiss, negative absorption is not possible. The conditions necessary for negative ab-sorption have been reviewed in a very lucid fashion by Wild et al (9).…”

mentioning

confidence: 99%

“…so that the phase velocity of light is greater than c. vv is the plasma frequency: V ( ne) (8) where ne is the number density of thermal electrons. Roughly speaking, the result of this change of phase velocity is that the Lorentz factor y in Eq.…”

mentioning

confidence: 99%

Possibility of Maser Action in Cosmic Radio Sources

McCray¹

1966

Science

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“…Later, Rai et al [1972] based on the previous reference of Bekefi and Brown [1961], found that the bremsstrahlung process is a possible source of RF emissions in UHF and microwaves measured during some lightning processes. The authors demonstrated how the full ionized plasma in the return stroke does not radiate microwave power since its absorption coefficient lets to an optical thickness much greater than the unity.…”

Section: Bekefi and Brownmentioning

confidence: 99%

X-rays and microwave RF power from high voltage laboratory sparks

Montanyà

Fabró

March

et al. 2015

Journal of Atmospheric and Solar-Terrestrial Physics

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Lightning flashes involve high energy processes that still are not well understood. In the laboratory, high voltage pulses are used to produce long sparks in open air allowing the production of energetic radiation. In this paper X-rays emitted by long sparks in air are simultaneously measured with the RF power radiation at 2.4 GHz. The experiment showed that the measured RF power systematically peaks at the time of the X-rays generation (in the microsecond time scale). All of the triggered sparks present peaks of RF radiation before the breakdown of the gap. The RF peaks are related to the applied voltage to the gap.RF peaks are also detected in discharges without breakdown. Cases where X-rays are detected presented higher RF power. The results indicate that at some stage of the discharge, before the breakdown, electrons are very fast accelerated letting in some cases to produce X-rays. Microwave radiation and X-rays may come from the same process.2

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Emission of Radio-Frequency Waves from Plasmas

Cited by 35 publications

References 3 publications

Observation of Shell Structure, Electronic Screening, and Energetic Limiting in Sparks

Observation of Shell Structure, Electronic Screening, and Energetic Limiting in Sparks

Possibility of Maser Action in Cosmic Radio Sources

X-rays and microwave RF power from high voltage laboratory sparks

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