Plume Characterization of an Ion-Focusing Hall Thruster

The role of the electrically conductive vacuum chamber wall in the completion of the discharge circuit of a Hall effect thruster (HET) is experimentally investigated. The AerojetRocketdyne T-140 laboratory-model HET operating at a discharge voltage of 300 V, discharge current of 5.16 A, and anode flow rate of 5.80 mg/s serves as a representative HET test bed. The nominal facility operating pressure during thruster firings is 4.9 × 10 -6 Torr corrected for xenon. Two 0.91 m x 0.91 m square aluminum plates are placed adjacent to, but electrically isolated from, the walls of the stainless steel vacuum chamber at two locations with respect to the center of the thruster exit plane: 4.3 m axially downstream along thruster centerline and 2.3 m radially outward centered on the exit plane. The plates are configured in three distinct electrical configurations with corresponding measurements: a) electrically grounded plates with measurements of currents to ground, b) electrically isolated plates with measurements of floating voltages, and c) isolated but electrically connected plates with measurements of the current conducted between them. The measurements are all taken simultaneously with the discharge current oscillations of the thruster at a sampling frequency of 100 MHz. Measurements of the current conducted to ground in the electrically grounded configuration reveal that the axial and radial plates collect ion currents that are 13.6% and 10.7% of the discharge current, respectively; the collected current is coupled to the discharge current oscillations but is smaller in magnitude and phase-delayed. In the electrically connected plate configuration, 5.5% of the average discharge current is observed to flow from the axial plate to the radial plate driven by a floating voltage difference of 7.6 V; this current is uncorrelated in time with the discharge current oscillations. These results indicate that the vacuum chamber conducts current and is a recombination site for a significant number of plume ions during HET operation. NomenclatureI = current, A 2 Pb = vacuum chamber base pressure, Torr Pc = corrected vacuum chamber background pressure, Torr Pi = indicated vacuum chamber background pressure, Torr V = voltage, V Vc-g = cathode-to-ground voltage, V Vd = discharge voltage, V Vp = plasma potential with respect to ground, V Vpa = axial plate voltage with respect to ground, V Vpr = radial plate voltage with respect to ground, V ΔV = acceleration voltage, V ΔVcath = cathode coupling voltage, V

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“…The mass flow controllers have an uncertainty of ± 0.03 mg/s (5.1%) for the cathode flow and ± 0.12 mg/s (2%) for the anode flow. 19,20 …”

Section: B T-140 Hetmentioning

confidence: 98%

Preliminary Assessment of the Role of a Conducting Vacuum Chamber in the Hall Effect Thruster Electrical Circuit

Frieman¹,

King²,

Khayms³

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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“…The controllers were calibrated before each test by measuring gas pressure and temperature as a function of time in a known control volume. The mass flow controllers have an uncertainty of 0.03 mg∕s (5.1%) for the cathode flow and 0.12 mg∕s (2%) for the anode flow [19,20].…”

Section: A Vacuum Facilitymentioning

confidence: 99%

Role of a Conducting Vacuum Chamber in the Hall Effect Thruster Electrical Circuit

Frieman

King

Walker

et al. 2014

Journal of Propulsion and Power

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“…The Savitzky-Golay filter is frequently used for smoothing and differentiating current-voltage characteristics of Langmuir probes and RFEAs 23,25,41,42 . The filtering is achieved by doing a running fitting of a polynomial of degree N using the least-squares method on a subset of the (x, y) experimental data of width M > N centered around a given point x i (forcing M to strictly be an odd number).…”

Section: Savitzky-golay Filtermentioning

confidence: 99%

Data Processing Techniques for Ion and Electron Energy Distribution Functions

Caldarelli¹,

Filleul²,

Boswell³

et al. 2022

Preprint

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Retarding field energy analyzers and Langmuir probes are routinely used to obtain ion and electron energy distribution functions (IEDF, EEDF). These typically require knowledge of the first and second derivatives of the I-V characteristics, both of which can be obtained in various ways. This poses challenges inherent to differentiating noisy signals, a frequent problem with electric-probe plasma diagnostics. A brief review of commonly used analog and numerical filtering and differentiation techniques is presented, together with their application on experimental data collected in a radio-frequency plasma. The application of each method is detailed with regards to the obtained IEDF and EEDF, the deduced plasma parameters, dynamic range, energy resolution and signal distortion.

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Plume Characterization of an Ion-Focusing Hall Thruster

Cited by 14 publications

References 18 publications

Preliminary Assessment of the Role of a Conducting Vacuum Chamber in the Hall Effect Thruster Electrical Circuit

Preliminary Assessment of the Role of a Conducting Vacuum Chamber in the Hall Effect Thruster Electrical Circuit

Role of a Conducting Vacuum Chamber in the Hall Effect Thruster Electrical Circuit

Data Processing Techniques for Ion and Electron Energy Distribution Functions

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