Experimental investigation of an argon hollow cathode

Stillwell, R. P.; Robinson, R. S.; Kaufman, H. R.; Cupp, R. K.

doi:10.2514/3.25714

Cited by 7 publications

(2 citation statements)

References 6 publications

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“…The use of the lowest t ON required to maintain the sintering temperature confirmed the effect of impurities on the ionization and the resulting decrease in temperature. In a hollow cathode discharge study for a spacecraft application, the results of Stillwell et al (1985) indicated that increasing the flow allows for decreased discharge potentials while keeping the electrical current unaltered. This finding lends additional support to the above discussion.…”

Section: Evolution Of the Electrical Discharge Parameters In The Sint...mentioning

confidence: 99%

Influence of the gas mixture flow on the processing parameters of hollow cathode discharge iron sintering

Brunatto¹,

Muzart²

2007

J. Phys. D: Appl. Phys.

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A study was made to verify the influence of the gas mixture flow on the iron sintering process with simultaneous surface enrichment of alloying elements by hollow cathode discharge. In this process, two independent cathodes formed an annular discharge: (1) a pressed cylindrical sample of iron powder, acting as the central cathode, was placed concentrically inside an external (hollow) cathode; (2) the external cathode, machined from a AISI 310 steel bar, acted both to confine the geometry of the plasma and as a source of alloying elements (Cr and Ni). The sintering was carried out at 1423 K, for a period of 7.2 × 103 s, under a gas mixture of 80% Ar + 20% H2 and a pressure of 399 Pa, at flow rates of 2 × 10−6, 5 × 10−6, and 8 × 10−6 m3 s−1, with an inter-cathode radial space of 5.8 mm. The discharge was generated using a pulsed voltage power source with a 200 µs period. The gas mixture flow plays an important role both in the cleanliness of the sintering atmosphere (reflected in the electric power utilized to maintain the sample's temperature) and in the amount of metallic atoms deposited on the sample's surface (as a result of the sputtering and the oxidation/reduction process on the cathode surfaces).

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Section: Evolution Of the Electrical Discharge Parameters In The Sint...mentioning

confidence: 99%

Influence of the gas mixture flow on the processing parameters of hollow cathode discharge iron sintering

Brunatto¹,

Muzart²

2007

J. Phys. D: Appl. Phys.

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“…The plasma source chosen is a hollow cathode which is based on the design reported by Kaufman and Robinson 16 and Still well et al 17 A Langmuir probe is used to determine the characteristics of the plasma generated by the plasma source. The probe is placed in the proximity of the test article so that the plasma conditions at the test article are known.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Plasma electron collection through biased slits in a dielectric

Carruth

1987

Journal of Spacecraft and Rockets

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A large number of experimental and analytical efforts have been directed toward understanding the plasma sheath growth and discharge phenomena which lead to high-voltage solar array/space plasma interactions. An important question which has not been addressed is how the voltage gradient in the plasma sheath near the surface of such an array may affect these interactions. The purpose of the experimental study described in this paper is to examine the merging of the sheaths around biased slits in a dielectric and how this affects the collection of electrons through these slits. The data, which are obtained by emissive probes and direct measurement of the current collected through the slits, indicate that when the sheaths merge the current collection by the slits is significantly altered with the most positive slit collecting more electrons than it otherwise would. Therefore, the effect of a voltage gradient in the sheath around a solar array should be considered when evaluating solar array performance.

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The physics of positively biased conductors surrounded by dielectrics in contact with a plasma

Hastings

Chang

1989

Physics of Fluids B: Plasma Physics

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The physics of a positively biased conductor surrounded by dielectrics in contact with plasma is investigated. It is shown that because of the presence of secondary emission from the surrounding dielectrics the voltage of the surfaces near the conductor has three solutions. Of the three possible solutions, the high- and low-voltage solutions are stable while the intermediate voltage solution is unstable. For the stable solutions, the low-voltage solution always has very low secondary emission while the high-voltage solution has high secondary emission. The secondary current emitted from the neighboring dielectrics is collected by the conductor. When the voltage on the dielectric undergoes a transition from one bistable solution to another this will be seen as a concomitant increase in the current collected to the conductor. This theory is applied to explain the ‘‘snapover’’ effect. The snapover effect is observed on high-voltage solar arrays that involve the use of highly biased surfaces in contact with the space environment. It has been observed that when such surfaces are postively biased the current undergoes an anomalous increase at a critical voltage.

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Experimental investigation of an argon hollow cathode

Cited by 7 publications

References 6 publications

Influence of the gas mixture flow on the processing parameters of hollow cathode discharge iron sintering

Influence of the gas mixture flow on the processing parameters of hollow cathode discharge iron sintering

Plasma electron collection through biased slits in a dielectric

The physics of positively biased conductors surrounded by dielectrics in contact with a plasma

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