Low Frequency Wave Detection in the Plume of a Low Temperature Magnetic Nozzle

Hepner, Shadrach; Collard, Timothy A.; Jorns, Benjamin

doi:10.2514/6.2018-4730

Cited by 2 publications

(2 citation statements)

References 5 publications

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“…With that said, we recognize that three processes discussed here may not be the only or dominant driving factors, and their interactions with the plume expansion may vary between devices. Other near-field detachment processes have been recently identified [13] which may also have an effect here. The relationships we see, particularly with the charge exchange process, are compelling but correlational at this point.…”

Section: Ionization Within the Plumementioning

confidence: 60%

“…The increasing demand for new forms of in-space propulsion for small spacecraft has given rise in the past two decades to a growing interest in low power (<200 W) magnetic nozzle thrusters [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. This interest stems largely from the number of advantages magnetic nozzles, a form of electric propulsion that employs a diverging magnetic field to accelerate a heated plasma, can offer compared to state-of-the-art technology.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic nozzle efficiency in a low power inductive plasma source

Collard

Jorns

2019

Plasma Sources Sci. Technol.

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The nozzle efficiency and performance of a magnetic nozzle operating at low power (<200 W) are experimentally and analytically characterized. A suite of diagnostics including Langmuir probes, emissive probes, Faraday probes, and laser induced fluorescence are employed to map the spatial distribution of the plasma properties in the near-field of a nozzle operated with xenon and peak magnetic field strengths ranging from 100 to 600 G. The nozzle efficiency is found to be <10% with plasma thrust contributions <120 μN and specific impulse <35 s. These performance measurements are compared with predictions from quasi-1D idealized nozzle theory and found to be 50%-70% of the model predictions. It is shown that the reason for this discrepancy stems from the fact that the underlying assumption of the idealized model-that ions are sonic at the throat of the nozzle-is violated at low power operation. By correcting for the shifting location of the sonic transition point, the model and experiment are made to agree. The physical mechanism by which the sonic line moves with respect to the nozzle geometry is attributed to non-ideal behavior at low power. In particular, it is posited that the low ionization fraction at these low operational powers gives rise to neutral-collisional effects in the near-field of the device that can impede ion acceleration. The roles of ionization, enhanced electron resistivity, and charge exchange collisions are all examined. It is found that the ion sonic transition location is most correlated with the ratio of the charge exchange mean free path to the characteristic electrostatic acceleration length giving rise to an effective drag term on the ions.

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Section: Ionization Within the Plumementioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Magnetic nozzle efficiency in a low power inductive plasma source

Collard

Jorns

2019

Plasma Sources Sci. Technol.

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Anisotropic electron heating in an electron cyclotron resonance thruster with magnetic nozzle

2023

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In a grid-less electron cyclotron resonance plasma thruster with a diverging magnetic nozzle, the magnitude of the ambipolar field accelerating the positive ions depends on the perpendicular energy gained by the electrons. This work investigates the heating of the electrons by electromagnetic waves, taking their bouncing motion into account in a confining well formed by the magnetic mirror force and the electrostatic potential of the thruster. An electromagnetic particle-in-cell code is used to simulate the plasma in a magnetic field tube. The code's Maxwell solver is based on a semi-Lagrangian scheme known as the constrained interpolation profile which enables larger time steps. The results show that anisotropic plasma heating takes place exclusively inside the coaxial chamber, along a Doppler-broadened zone. It is also shown that a trapped population of electrons with a larger perpendicular energy exists in the plume.

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Low Frequency Wave Detection in the Plume of a Low Temperature Magnetic Nozzle

Cited by 2 publications

References 5 publications

Magnetic nozzle efficiency in a low power inductive plasma source

Magnetic nozzle efficiency in a low power inductive plasma source

Anisotropic electron heating in an electron cyclotron resonance thruster with magnetic nozzle

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