Measurements of dipole antenna impedance in an isotropic laboratory plasma

Graf, K. A.; Jassby, D. L.

doi:10.1109/tap.1967.1139001

Cited by 10 publications

(5 citation statements)

References 12 publications

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“…The strength of the magnetic field is controlled by a variac and a potentiometer in the dc power We use a balanced dipole similar to that used by others [Graf and Jassby, 1967;Snyder and Mittra, 1968]. The dipole is constructed by removing a short length of the outer conductor and the dielectric of two parallel semirigid 50-ohm coaxial cables having an outside diameter of 0.085 in.…”

Section: Experimental Apparatusmentioning

confidence: 99%

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Input impedance of a short dipole antenna in a warm anisotropic plasma, 2, Experiment

Nakatani¹,

Kuehl²

1976

Radio Science

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The measured input impedance of a short, cylindrical dipole immersed in a pulsed, RF discharge, anisotropic, argon plasma is presented. The experimental results show that the input impedance undergoes a pronounced change when the antenna frequency passes through the harmonics of the electron cyclotron frequency, which is in agreement with the predictions of kinetic theory. In general, the correlations between experimental and theoretical results are judged as fair to very good over a wide range of plasma parameters. Effects of the plasma sheath are found to be important and a sheath correction term based on a simple sheath model is included for correlating experimental and theoretical results. Using a curve‐fitting technique, a sheath thickness of 3λD was determined. Impedance measurements at dipole frequencies above the harmonics showed anomalous results which are explained by kinetic theory.

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Section: Experimental Apparatusmentioning

confidence: 99%

“…Input impedance measurements for an electrically long dipole [ Graf and Jassby, 1967] and for a thick monopole [Ancona, 1971 ] were made in an isotropic Copyright ¸ 1976 by the American Geophysical Union. plasma.…”

Section: Introductionmentioning

confidence: 99%

Input impedance of a short dipole antenna in a warm anisotropic plasma, 2, Experiment

Nakatani¹,

Kuehl²

1976

Radio Science

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“…Besides the diagnostic studies, QTN spectroscopy can be used for precise calibration measurements of plasma parameters in a laboratory device, where the external magnetic field can be completely annulled in the system [Harp, 1964;Graf and Jassby, 1967]. In these unmagnetized plasmas, the entire QTN spectrum can be used for precise plasma diagnostics-examining the electron temperature and the collision frequency from the low-frequency part of the spectrum, plasma density (with collisional corrections given in section 2.3) from the resonance region and of the electron temperature alone from the high-frequency part.…”

Section: Laboratory Plasmas and Unmagnetized Ionospheresmentioning

confidence: 99%

Electrostatic thermal noise in a weakly ionized collisional plasma

et al. 2017

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Quasi‐thermal noise (QTN) spectroscopy is a plasma diagnostic technique which enables precise measurements of local electron velocity distribution function moments. This technique is based on measurements and analysis of voltage fluctuations at the antenna terminals, induced by thermal motion of charged particles. In this work, we accommodate, for the first time, this technique to weakly ionized collisional plasmas. It turns out that the QTN spectrum is modified both at low frequencies, increasing the level of power spectrum, and around the plasma frequency, where collisions damp the plasma oscillations and therefore broaden and reduce the amplitude of so called “plasma peak,” while the spectrum at high frequencies is nearly unmodified compared to the collisionless case. Based on these results, we show that QTN spectroscopy enables independent measurements of the collision frequency, electron density, and temperature, provided the ratio of collision frequency to plasma frequency is ν/ωp∼0.1. The method presented here can be used for precise estimation of plasma parameters in laboratory devices and unmagnetized ionospheres, while application in the ionosphere of Earth is possible but limited to small, low‐frequency range due to magnetic field influence.

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“…If this aerial is longer than a wavelength, it has a wider frequency band, a wider beamwidth and fewer minor lobes than the equivalent unloaded aerial. The behaviour of this equivalent aerial in a warm plasma has been investigated both theoretically (Wait 1965, Talekar andGupta 1967) and experimentally (Ting et al 1968, Judson et al 1968, Graf and Jassby 1967. In this letter, the radiation resistance of the loaded dipole aerial (LDA) is evaluated in an L11 isotropic warm plasma, and the computed values compared with those for the equivalent unloaded dipole aerial (UDA).…”

Section: Radiation Resistance Of a Centre-fed Dipole With Non-reflectmentioning

confidence: 99%

Reincrease in Electron Density in the Current-Decaying Phase of Pulsed-Discharge of Argon-Hydrogen Mixture

Watanabe

Shiratani

Ogi

et al. 1988

Jpn. J. Appl. Phys.

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best fit methods, and the results are shown in figure 3 in the form of ( M -1) = f ( E / N ) and l/y=g(E/N) as in figure 2. It is apparent that these results show that the theory outlined above is indeed the correct explanation of breakdown. The three intersections of ( M -1) and l/y curves are obtained showing clearly the reasons for the inflexion in the Paschen curve for Hg vapour.It is intended that a full account of the theoretical and experimental techniques will be published elsewhere.

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Measurements of dipole antenna impedance in an isotropic laboratory plasma

Cited by 10 publications

References 12 publications

Input impedance of a short dipole antenna in a warm anisotropic plasma, 2, Experiment

Input impedance of a short dipole antenna in a warm anisotropic plasma, 2, Experiment

Electrostatic thermal noise in a weakly ionized collisional plasma

Reincrease in Electron Density in the Current-Decaying Phase of Pulsed-Discharge of Argon-Hydrogen Mixture

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