Non-invasive Hall current distribution measurement in a Hall effect thruster

Area of Science:

• Plasma Physics
• Electric Propulsion
• Applied Electromagnetics

Background:

• Hall thrusters are crucial for space propulsion.
• Understanding Hall current density distribution is key to optimizing performance.
• Previous methods for measuring current density are often invasive or lack spatial resolution.

Purpose of the Study:

• To develop a non-invasive method for determining Hall current density distribution in closed drift thrusters.
• To utilize remote magnetic field measurements and inverse problem solving for current density mapping.
• To validate the method by comparing results with known thruster behavior.

Main Methods:

• Employing an array of eight tunneling magnetoresistive (TMR) sensors for high-sensitivity magnetic field measurements.
• Positioning the sensor array outside the thruster channel to measure induced magnetic fields.
• Applying Tikhonov regularization to solve the inverse problem for current density distribution.
• Analyzing temporal variations and calculating ratios of Hall current to discharge current.

Main Results:

• Successfully determined Hall current density distributions as a function of time using contour plots.
• Measured Hall current to discharge current ratios between 6.1 and 7.3 across various operating powers (1.3 kW to 2.2 kW).
• Identified a breathing mode frequency of 24 kHz at 1.5 kW, consistent with discharge current measurements.

Conclusions:

• The developed remote magnetic field measurement and inverse problem solving technique effectively determines Hall current density distribution.
• The method provides valuable insights into thruster dynamics, including breathing mode frequencies.
• This non-invasive approach offers a significant advancement for Hall thruster research and development.