Plasma characterization in Hall thrusters by Langmuir probes

Andreussi, Tommaso; Saravia, M. M.; Andrenucci, Mariano

doi:10.1088/1748-0221/14/05/c05011

Cited by 10 publications

(5 citation statements)

References 19 publications

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“…Finally, concerning the axial profiles of the electron temperature (figure 9(g)), the time-averaged peaks are consistent with the results reported in [42,43]. In this regard, it is important to highlight that the simulated cases correspond to relatively low power levels, around 8-12 kW.…”

Section: Resultssupporting

confidence: 86%

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reza

Farbod

Knoll

et al. 2023

Plasma Sources Sci. Technol.

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High-power magnetically shielded Hall thrusters have emerged in recent years to meet the needs of the next-generation on-orbit servicing and exploration missions. Even though a few such thrusters are currently undergoing their late-stage development and qualification campaigns, many unanswered questions yet exist concerning the behavior and evolution of the plasma in these large-size thrusters that feature an unconventional magnetic field topology. Noting the complex, multi-dimensional nature of plasma processes in Hall thrusters, high-fidelity particle-in-cell (PIC) simulations are optimal tools to study the intricate plasma behavior. Nonetheless, the significant computational cost of traditional multi-dimensional PIC schemes renders simulating the high-power thrusters without any physics-altering speed-up factors unfeasible. The novel reduced-order “quasi-2D” PIC scheme enables a significant reduction in the computational cost requirement of the PIC simulations. Thus, in this article, we demonstrate the applicability of the reduced-order PIC for a cost-efficient, self-consistent study of the physics in high-power Hall thrusters by performing simulations of a 20 kW-class magnetically shielded Hall thruster along the axial-azimuthal and radial-azimuthal coordinates. The axial-azimuthal quasi-2D simulations are performed for three operating conditions in a rather simplified representation of the thruster’s inherently 3D configuration. Nevertheless, we have resolved self-consistently an unprecedented 650 µs of the discharge evolution without any ad-hoc electron mobility model, capturing several breathing cycles and approximating the experimental performance parameters with an accuracy of 70 to 80 % across the operating conditions. The radial-azimuthal simulations, carried out at three cross-sections corresponding to different axial locations within the discharge channel, have casted further light on the evolution of the azimuthal instabilities and the resulting variations in the electrons’ cross-field mobility and the plasma-wall interactions. Particularly, we observed the development of a long-wavelength, relatively low-frequency wave mode near the exit plane of the thruster’s channel that induces a notable electron transport and a significant ion heating.

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Section: Resultssupporting

confidence: 86%

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reza

Farbod

Knoll

et al. 2023

Plasma Sources Sci. Technol.

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“…This is broadly consistent with multiple previous studies [9,[11][12][13][14][15][16][17]. In these previous works, the cause for the difference in efficiency was largely attributed to the role of ionization rate [9,13,17,18,69,70]. Assuming that xenon and krypton have the same electron temperature at a given condition, xenon would have a higher ionization rate coefficient (figure 2).…”

Section: Overall Efficiency Comparisonsupporting

confidence: 91%

Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton

Su,

Marks,

Jorns

2024

Plasma Sources Sci. Technol.

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The trends in mass utilization with increasing discharge voltage and current are investigated for a magnetically shielded Hall thruster operating on xenon and krypton. A 9-kW class shielded thruster is operated with discharge voltages from 300 to 600 V and discharge currents from 15 to 30 A on xenon and krypton. Experimental measurements of discharge current, thrust, anode efficiency, and ion velocity as a function of axial position are used to calibrate a multi-fluid 2D Hall thruster code at all operating conditions. The results of these calibrated simulations are employed to interrogate the plasma properties inside the thruster channel. A simplified 0D model for mass utilization evaluated on spatial averages of the simulated plasma parameters is employed to interpret the response of this efficiency mode with power for each propellant. It is found that with both higher voltage and current, mass utilization increases for both gases and their relative gap in this efficiency decreases. This can be attributed to the higher plasma densities and ionization rate coefficients at high voltage, and solely to higher plasma densities at high current. The driving factors for the increase in mass utilization are examined in the context of its nonlinear response to internal plasma properties. The behavior of mass utilization is also discussed in context of the gap in overall efficiency between the propellants. Finally, the implications of these results for improving the performance of high power Hall thrusters operating on krypton are examined.

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“…The first is the operating parameters of the device, that is, the plasma generation conditions, such as the current of the toroidal field and vertical field coils, the microwave power injected by the ECRH system, the flow rate of the gas puffing, the gas composition in vacuum vessel, and so on. The second type is the parameters of the plasma itself, including the density, temperature, floating potential, macro status, etc., which need to be measured by diagnostic tools such as Langmuir probes [14] and high-speed cameras [15]. The data acquisition system uses a PXIe-based controller as LCM.…”

Section: Data Acquisition and Management Systemmentioning

confidence: 99%

Helimak control system

Yang

Wen

et al. 2023

J. Inst.

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The excellent wall condition is essential for fusion devices to generate reproducible high-parameter plasma. Wall conditioning techniques should be validated before applying on large fusion devices to reduce potential risk. Helimak, a toroidal steady state magnetic confinement device, was reassembled and upgraded to a technical validation platform for wall conditioning. A new control system has been developed to achieve the upgrade of Helimak. The control system is based on a distributed control architecture, which provides not only efficient development but also flexible control mechanisms. For each auxiliary subsystem, a corresponding local control module is developed to drive and control a variety of equipment. The control network ensures real-time transmitting of the parameters and data. A dedicated trigger network and timing control module can improve synchronization and real-time performance. Data acquisition system based on mature commercial busses provides sufficient data acquisition capabilities for diagnostic tools. The data management system uses MDSplus to provide convenient data access. An independent interlock and safety system is designed for comprehensive and reliable personal protection. After engineering commissioning, the Helimak has realized wall conditioning by electron cyclotron resonance heating (ECRH) plasma at different resonance positions. The flexibility of control systems allows the installation of more wall conditioning tools in the future that will provide the ability to validate combined wall conditioning techniques. Helimak will become a low-cost, reliable technology verification platform, which will help to achieve advanced scenarios in tokamak and stellarator.

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Plasma characterization in Hall thrusters by Langmuir probes

Cited by 10 publications

References 19 publications

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Reduced-order particle-in-cell simulations of a high-power magnetically shielded Hall thruster

Trends in mass utilization of a magnetically shielded Hall thruster operating on xenon and krypton

Helimak control system

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