Spectroscopic measurements on xenon plasma in a hollow cathode

Malik, Anil Kumar; Montarde, P; Haines, M. G.

doi:10.1088/0022-3727/33/16/316

Cited by 26 publications

(23 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The code includes thermal conduction, radiative heat losses, and, within the insert region, radiative heat transfer. It does not include plasma radiation, which is assumed small, because the resonant xenon lines are optically thick in the line centers [13]. A schematic of the thermal fluxes modeled is shown in Fig.…”

Section: Thermal Modelmentioning

confidence: 99%

Thermal Model of the Hollow Cathode Using Numerically Simulated Plasma Fluxes

Katz

Mikellides

Polk

et al. 2007

Journal of Propulsion and Power

View full text Add to dashboard Cite

The first results from a hollow cathode thermal model are presented. The thermal model uses the spatially distributed plasma fluxes, calculated by a two-dimensional axisymmetric model of the plasma inside the emitter region, as the heat source to predict the hollow cathode and insert temperatures. The computed insert temperature profiles are compared with measured values for a cathode similar to the 0.635-cm diameter discharge cathode used in the NASA solar electric propulsion technology applications readiness ion engine. The insert temperatures can be used to predict cathode life from barium depletion. The present results and related experimental studies yield three important conclusions. First, the emitter in the NASA solar electric propulsion technology applications readiness hollow cathode does not operate in the emission-limited regime. The thermionic electron current is about 20 A higher than the discharge current and requires significant reverse electron flux from the plasma to satisfy current continuity. Second, the high-plasma density near the centerline of the cathode results in power deposition on the orifice plate that is more than twice the emitter power deposition. Third, despite a higher heat load to the orifice plate, the operating temperature where it would be measured by a thermocouple is approximately 100 C lower than the emitter. The lower orifice plate temperature is due to poor thermal contact between the emitter and the cathode tube and higher than anticipated radiative losses from the external surface of the heater. Nomenclature F = geometrical configuration factor IP = ionization potential, V j emission = emission current density, A=m 2 j the e = plasma thermal current density, A=m 2 j i = plasma ion current density, A=m 2 _ q rad = heat loss by radiation, W=m 2 _ q emission = heat loss by electron emission, W=m 2 _ q e = heating by plasma electrons, W=m 2 _ q i = heating by plasma ion flux, W=m 2 T = material temperature, K T e = plasma electron temperature, eV WF = emitter work function, eV ij = Kronecker delta " = material emissivity = material thermal conductivity, W=m K = Stephan-Boltzman constant, W=m 2 K 4 sheath = sheath potential, V Introduction H IGH-POWER, long-life electric thrusters were considered necessary as NASA planned many of the challenging missions under the Prometheus program. These missions might have required an increase in both life and emission current compared with hollow cathodes used on NASA's Deep Space 1 spacecraft. Although both the discharge and neutralizer hollow cathodes were operating at the end of the NASA solar electric propulsion technology applications readiness (NSTAR) thruster 30,000-h extended life test [1], the future missions may be even more challenging. A previous life test of the International Space Station plasma contactor hollow cathode [2] ended after 28,000 h, when the cathode would no longer ignite. One scenario for end of life is when the insert can no longer provide free barium to lower the work function and the remaining barium in th...

show abstract

Section: Thermal Modelmentioning

confidence: 99%

Thermal Model of the Hollow Cathode Using Numerically Simulated Plasma Fluxes

Katz

Mikellides

Polk

et al. 2007

Journal of Propulsion and Power

View full text Add to dashboard Cite

show abstract

“…These measurements show good agreement with the spectroscopic measurements of Malik. 34 The ionization fraction has been shown to approach unity with the orifice of hollow cathodes however, even if the T5 HC approaches full ionization at very high levels of orifice current density the propellant mass utilization through the keeper orifice does not, in general, exceed 10%. 35 36 This latter parameter is defined as the ratio of extracted ion current over the equivalent current of 100% singly-ionized xenon.…”

Section: Current Collection Analytical Modelmentioning

confidence: 99%

Thrust production mechanisms in Hollow cathode microthrusters

Grubisic

Gabriel

2010

2010 IEEE Aerospace Conference

View full text Add to dashboard Cite

-Hollow cathode have recently been investigated at the University of Southampton as potential standalone microthrusters.12 Thrust measurements suggest that in some cases, hollow cathodes are able to generate specific impulse of over 1000s with xenon. The means by which hollow cathodes are able to generate such high levels of specific impulse is not clearly understood. This paper explores thrust production mechanisms in the T5, T6 and XIPS hollow cathodes based on thrust performance and ion energy measurements. Analysis suggests the total thrust produced includes components of gas dynamic thrust particularly as a result of an intense electron pressure at the cathode exit, but also shows evidence for magneto-hydro-dynamic (MHD) forces at high currents and low flow rates arising from the self-induced azimuthal magnetic field within the orifice and resulting cross-field interaction plasma. Data may also suggest ion acceleration due to plasma potential hills. While this initial characterization can only loosely attribute the relative magnitude each mechanism plays it does show evidence for each. This research shows that with further development based on an understanding of the thrust mechanism, hollow cathodes thrusters could present significant refinements to the technology of electric propulsion.

show abstract

“…Hollow cathodes are used in a wide variety of applications: as efficient light sources [23], as sources of electrons [207][208][209][210][211][212][213] to generate excited species for elemental analysis [1,152,183,214], as ion sources [3,199,[215][216][217][218][219], for nitriding [220][221][222][223], space propulsion [224][225][226], vacuum welding [227], basic plasma research [228,229], cluster formation [230] and plasma-activated pre-treatment and coating processes [231][232][233] among others.…”

Section: Use Of Hollow Cathodes In the Synthesis Of Thin Filmsmentioning

confidence: 99%