Characterization of a Barium Oxide Cathode Operating on Xenon and Iodine Propellants

Taillefer, Zachary; Blandino, John J.; Szabo, James

doi:10.2514/1.b37315

Cited by 17 publications

(8 citation statements)

References 32 publications

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“…In addition, LaB 6 cathodes are resistant to neutralization, but the operating temperature is as high as 1500-1600 • C, bringing considerable challenges to the performance of the heater and cathode life. [1][2][3] Therefore, it has become a current research hotspot and challenge to develop a new cathode material with low work function, low operating temperature, and stable chemical properties in the international electric propulsion field. 4 In 2004, the Tokyo Institute of Technology (Japan) reported for the first time the work function of C12A7: e − (2.4 eV), which is much lower than conventional cathode materials W (4.52 eV), LaB 6 (2.6 eV), CeB 6 (2.62 eV), and BaO-W (2.1 eV).…”

Section: Introductionmentioning

confidence: 99%

“…BaO‐W and LaB 6 traditional hollow cathodes are more maturely applied, whereas BaO‐W cathodes require high work gas purity, and the activation process is complicated. In addition, LaB 6 cathodes are resistant to neutralization, but the operating temperature is as high as 1500–1600°C, bringing considerable challenges to the performance of the heater and cathode life 1–3 . Therefore, it has become a current research hotspot and challenge to develop a new cathode material with low work function, low operating temperature, and stable chemical properties in the international electric propulsion field 4 .…”

Section: Introductionmentioning

confidence: 99%

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Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping

et al. 2022

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Ca 24 Al 28 O 64 ] 4+ (4e − ) (C12A7:e − ) has excellent potential in electric propulsion owing to various advantages, including low work function, low working temperature, and stable chemical properties. However, increasing electron concentration enhances the thermionic emission property of C12A7:e − . This study used a chemical method-spark plasma sintering to synthesize Zr-doped C12A7:e − (C12(A 1 − x Z x )7:e − , where x = 0 to 0.14). The study results show that C12(Al 0.86 Zr 0.14 )7:e − maximum injected electron concentration (n), conductivity (σ), electron mobility (μ n ), and zero-field emission current density (J o ) improved to 2.4 × 10 21 /cm 3 , 1507 S/cm, 5.2 cm 2 /V⋅s, and 2.4 A/cm 2 , respectively. The emission current density of the C12(Al 0.86 Zr 0.14 )7:e − could be maintained at about 2.9 A/cm 2 under 1100 • C, 4000 V, and 600 min. Theoretical calculation results prove that Zr doping broadens the cage conduction band (CCB) of C12A7:e − and reduces the bandgap between the CCB and the frame conduction band. In addition, Zr doping increases the electronic density of states near the Fermi level, and the density of states presents a continuous state. This helps to increase the injected electron concentration and enhance the electrical transport and thermionic emission characteristics of the sample. The calculation results provide theoretical support for the experiment.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping

et al. 2022

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“…In recent years the use of storable atomic propellants like bismuth and mercury for high thrust applications, and zinc and magnesium for high specific impulse applications has been investigated [1][2][3][4]. Some molecular propellants have been investigated, such as water (where the thruster operates on hydrogen and oxygen gas created by electrolysis) [5,6], iodine [7][8][9][10][11][12][13], and adamantane [14][15][16], but were all found to have prohibitive disadvantages such as significantly lower performance compared to xenon. A paper on the first in-space demonstration of (low-power) thruster operation on iodine vapor was recently published in Nature [13].…”

Section: Introductionmentioning

confidence: 99%

Aromatic Hydrocarbons as Molecular Propellants for Electric Propulsion Thrusters

Borrfors

Harding

Weissenreider

et al. 2023

Preprint

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The aromatic hydrocarbons (AHs) fluorobenzene, naphthalene, and 1fluoronaphthalene are introduced as promising alternatives to xenon as propellant for in-space electric propulsion (EP). These storable molecules have similar mass, lower cost, and lower ionization energies compared to xenon, as well as the critical advantage of low post-ionization fragmentation compared to other molecular propellant candidates. The ionization characteristics of AHs are compared with those of xenon and the diamondoid adamantane, previously evaluated as a molecular propellant for EP. Quantum chemical calculations and BEB theory together with 25 eV electron ionization mass spectrometry (EI-MS) measurements have been used to predict the fragmentation of the AHs and adamantane when ionized in a plasma with an electron temperature of 7 eV (a typical electron temperature in EP plasmas). A high fraction (81 − 8 %) of the detected AH ions originate from intact molecules, compared to 3 % for adamantane. indicating extraordinarily low fragmentation for the selected AHs. The ionization potential of the AHs is similar to that of adamantane but lower compared to xenon (8.14–9.2 eV for the AHs, 9.25 for adamantane and 12.13 eV for xenon). BEB calculations have also been used to predict total ionization cross sections. The calculated ionization cross section of the AHs is comparable to that of adamantane but 3–5 times higher than that of xenon, which together with the low ionization potential can contribute to more efficient ionization. The AHs may have the potential to perform better than xenon, despite the absence of fragmentation in xenon.

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“…However, in the case of beams and plasmas based on molecular gases, the most common situation encountered in different applications is indeed the presence of multiple ion species which may collectively change the surface chemistry and modify the effective SEE yield compared with that observed separately with each species. This is a situation, for example, that would be encountered in many material processing 21,22 or space propulsion 23,24 applications. Thus, the aim of the present work is not only to provide information on the SEE yield due to iodine ion bombardment, but to also study the emission behavior in the presence of multi-species ion beams.…”

Section: Introductionmentioning

confidence: 99%

Secondary electron emission due to multi-species iodine ion bombardment of different target materials

Habl

Rafalskyi

Lafleur

2021

Journal of Applied Physics

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Ion-induced Secondary Electron Emission (SEE) is a fundamental surface interaction that strongly influences many plasma discharges. Recently, interest in iodine plasmas is growing due to new material processing and space propulsion applications, but data for SEE yields due to iodine ion bombardment remains scarce. Additionally, due to the formation of multiple ion species in typical iodine plasmas, and surface chemical reactions leading to iodide layer formation, the effective SEE yield is expected to differ from that for individual ion species on clean surfaces. In this work, we measure the SEE yield of multi-species iodine ion beams bombarding different target materials (Mo, W, Al, Ti, Cu, carbon-carbon, and steel), in the energy range 0.6-1.4 keV. An ion beam is produced by extracting and accelerating ions from a gridded ion source based on an Inductively Coupled Plasma (ICP). SEE yields of downstream targets are measured using a conventional electrostatic probe technique, and the ion beam composition is determined using time-of-flight spectrometry. The beam is composed predominately of atomic (I + ) and molecular (I +2 ) ions whose ratio changes depending on the ICP power. Yields depend strongly on the target material and beam composition, and vary between 0.05-0.4 depending on whether potential or kinetic emission processes dominate.

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Characterization of a Barium Oxide Cathode Operating on Xenon and Iodine Propellants

Cited by 17 publications

References 32 publications

Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping

Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping

Aromatic Hydrocarbons as Molecular Propellants for Electric Propulsion Thrusters

Secondary electron emission due to multi-species iodine ion bombardment of different target materials

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Characterization of a Barium Oxide Cathode Operating on Xenon and Iodine Propellants

Cited by 17 publications

References 32 publications

Enhancing the injected electron concentration and thermionic emission property in C12A7:e− ceramic via Al site Zr doping

Enhancing the injected electron concentration and thermionic emission property in C12A7:e− ceramic via Al site Zr doping

Aromatic Hydrocarbons as Molecular Propellants for Electric Propulsion Thrusters

Secondary electron emission due to multi-species iodine ion bombardment of different target materials

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Product

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Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping

Enhancing the injected electron concentration and thermionic emission property in C12A7:e⁻ ceramic via Al site Zr doping