Antenna impedance measurements and sheath effects in an RF generated plasma

Ancona, C.

doi:10.1109/tap.1971.1139912

Cited by 7 publications

(2 citation statements)

References 11 publications

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“…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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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: 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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“…More often, because of rocket outgassing, quite different results are obtained on the upleg and downleg of the trajectory [Bramley, 1965;Pfister and Ulwick, 1965]. In laboratory experiments, the plasma inhomogeneity may be important [ Chen et al, 1967], and there are effects of the limited volume available [Ancona, 1971] In some instances, parasitic effects have been encountered which made the data difficult to interpret. Some rocket experiments were hampered by telemetry radiation [Bramley, 1965], interferences between several on-board experiments [Hoang, 1971], base capacitance effects [Molozzi and Richardson, 1966], possibility of nonlinear effects due to too high an RF excitation voltage • [Miller and Schulte, 1970], unknown wake effects [Bramley, 1965].…”

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confidence: 99%

The impedance of a dipole antenna in the ionosphere: 1. Experimental study

Vernet¹,

Manning²,

Steinberg³

1975

Radio Science

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The impedance of a short electric dipole antenna has been measured from rockets in the ionosphere. The EIDI I experiment was launched in conditions where the plasma was expected to be nearly isotropic (operating frequencies 4.48 and 6.09 MHz, f0F2 ⋍ 9 MHz, fH ⋍ 1 MHz). It was designed to detect and measure or to eliminate most of the unwanted effects which complicated the data reduction of previous experiments: outgassing, telemetry radiation, etc. The number of parameters measured simultaneously on board (impedances with variable bias and RF excitation level, resonance frequencies, Te, dc current drawn by the antennas, vehicle potential) and from the ground or an overhead satellite was large enough to provide numerous cross checks and to determine the sheath dimensions. The impedance is very weakly spin‐modulated over most of the flight; the collision frequency is very low (v/ω ⋍ 10−5) unlike some of the previous experiments where collision losses were dominant. The measured values of the impedance are given as a function of X=f2p/f2 where the other parameters are known.

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Optimization of a two-stages electrostatic reflex ion source

Farchi

Wartski

Boukari

et al. 1994

Review of Scientific Instruments

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In our argon, oxygen, or nitrogen broad beam ion source, 80 mm in diameter, which is either an electrostatic reflex ion source, or a magnetic and electrostatic reflex ion source, the hot filament has been replaced by a carefully optimized microwave plasma (MP) cathode under the electron cyclotron resonance condition. Different geometries of antennae in which the microwave transverse electric field is more or less favored have been tested. A major improvement was obtained when a dc polarization of these antennae was superimposed onto the microwave field, allowing a fine tuning via the sheath thickness adjustment. Registered cathode currents under various conditions of pressure of neutrals, microwave power, and polarization voltage have shown a gain of a factor of 3 relative to the previous case where the single disk antenna was at a floating potential. Best results with argon gas at a pressure of 3×10−2 mbar were obtained with a spear-head shaped antenna fed at a microwave power of 50 W and polarized at 26 V. Extracted ion beam current densities as high as 5 mA/cm2 resulted from these different MP cathode improvements. Moreover, we have shown that the internal electronic tuning of the source can advantageously replace the traditional external tuning.

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Antenna impedance measurements and sheath effects in an RF generated plasma

Cited by 7 publications

References 11 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

The impedance of a dipole antenna in the ionosphere: 1. Experimental study

Optimization of a two-stages electrostatic reflex ion source

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