Effect of a Low Work Function Insert on Hollow Cathode Temperature and Operation

Rand, Lauren P.; Williams, John D.

doi:10.2514/6.2013-4037

Cited by 4 publications

(3 citation statements)

References 11 publications

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“…To achieve reproducible operation, an electride insert needed to be operated for approximately 10 h and be shut-down and restarted several times [16]. Reproducible operation was quantified by comparing the barrel temperature and anode voltage at a given set point of discharge current of 3.5 A and flow rate of 4 sccm of xenon.…”

Section: A Cathode Operationmentioning

confidence: 99%

A Calcium Aluminate Electride Hollow Cathode

Rand

Williams

2015

IEEE Trans. Plasma Sci.

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This paper discusses the development and testing of a C12A7 electride hollow cathode. C12A7:e − is a crystalline ceramic in which electrons clathrated in subnanometer sized cages act as a conductive medium. C12A7:e − has a predicted work function of 0.6 eV and hence is of interest in electron emission devices. A 6-mm diameter hollow cathode was fabricated with a C12A7:e − insert and operated for over 50 h on xenon with no signs of degradation. It was successfully started at room temperature without a heater and steady state operating temperatures below 650°C were observed during some tests. In addition, the C12A7:e − cathode was operated on iodine for over 20 h at discharge currents up to 15 A.

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Section: A Cathode Operationmentioning

confidence: 99%

A Calcium Aluminate Electride Hollow Cathode

Rand

Williams

2015

IEEE Trans. Plasma Sci.

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“…This led to the rise of lanthanum hexaboride, a refractory compound characterized by its low work function, high melting point, and robust chemical stability, making it an ideal choice for cathode applications, particularly in satellite missions [21][22][23]. Calcium aluminate electride (C12A7) is a promising contender for future electric propulsion endeavors [24,25]. While the exact work function of C12A7 remains a topic of debate, there is a consensus in the academic community that C12A7 boasts a notably lower work function compared to traditional emitter materials [16].…”

Section: Introductionmentioning

confidence: 99%

Analysis of anode surface roughness influence on heaterless hollow cathode discharge

Hsieh,

Huang,

Huang

et al. 2024

Phys. Scr.

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This research delves into the influence of cylindrical and planar anode surface roughness on heaterless hollow cathode discharge characteristics. Three surface roughness levels, Ra 1.6 µm, Ra 3.2 µm, and Ra 6.4 µm, along the cylindrical anode's azimuthal direction and the planar anode's radial direction, have been selected and modified by the machining process. A central finding is the correlation between the discharge voltage and anode surface roughness. As the roughness increases, cylindrical and planar anodes require less discharge voltage to sustain the primary discharge. This reduction is likely due to the enhanced surface area from the roughness, which aids in electron current collection. The discharge voltage oscillations appear inversely related to the surface roughness of planar anodes, which may be associated with changes in the neutral gas density gradient between the planar anode and the cathode. In contrast, cylindrical anodes show fewer effects from their surface roughness, likely due to the distinct neutral gas flow dynamics. These findings offer insights into standardizing hollow cathode testing and allow future research to explore these interactions more deeply.

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“…The main characteristic was an increase in anode voltage from 140 to 180 V after 4-5 h, suggesting an increase in emitter temperature [8,11]. Rand et al also reported instabilities and higher anode voltages of the heaterless C12A7 hollow cathode due to surface contamination [11,14].…”

Section: Introductionmentioning

confidence: 99%

An experimental study on the degradation of the C12A7 hollow cathode

Hua¹,

Wang²,

Luo³

et al. 2022

Plasma Sci. Technol.

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Emitter overheating is by far the largest problem limiting the performance of novel C12A7 hollow cathodes. To explore the failure operating point and degradation mechanism of the C12A7 hollow cathode, microscopic analyses of a degraded electride emitter after ten hours of thermal electron emission are presented in this paper. The morphology and composition variation of overheated electride emitters by SEM, EDS, and XRD indicate the melting and decomposition of electride of the surface layer. The monitored temperature of the electride emitter during the C12A7 hollow cathode operation shows that to avoid overheating the electride emitter, the average current density should be about 64 mA/mm2 allowed for the C12A7 hollow cathode in its current configuration. Experiment results of the heaterless C12A7 hollow cathode demonstrate that the Xe ions bombardment can remove the insulating layer and restore the thermionic emission capability for less degraded emitters. Based on experimental results and microscopic characterization, the depletion and degradation mechanism of electride emitters during the hollow cathode operation are discussed.

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Effect of a Low Work Function Insert on Hollow Cathode Temperature and Operation

Cited by 4 publications

References 11 publications

A Calcium Aluminate Electride Hollow Cathode

A Calcium Aluminate Electride Hollow Cathode

Analysis of anode surface roughness influence on heaterless hollow cathode discharge

An experimental study on the degradation of the C12A7 hollow cathode

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