Time-resolved ion energy measurements using a retarding potential analyzer for electric propulsion applications

Area of Science:

• Plasma physics
• Electric propulsion diagnostics

Background:

• Characterizing plasma requires time-resolved diagnostic tools.
• Retarding potential analyzers (RPAs) are crucial for measuring ion energy distributions in electric propulsion (EP).
• Existing diagnostics have limitations in measuring high-frequency plasma oscillations.

Purpose of the Study:

• To verify the functionality of a high-speed retarding potential analyzer (HSRPA).
• To assess HSRPA's capability in measuring time-resolved ion energies at frequencies relevant to Hall effect thrusters (HETs).
• To demonstrate an effective alternative diagnostic for time-resolved plasma measurements.

Main Methods:

• Utilized a gridded ion source with superimposed oscillations (sine, triangle, noisy sine waves) at 20-80 kHz.
• Employed a high-speed retarding potential analyzer (HSRPA) with high-speed circuitry.
• Applied data fusion techniques (empirical transfer function method, shadow manifold interpolation) for data reconstruction.

Main Results:

• Successfully reconstructed time-series data from HSRPA measurements.
• Produced time-resolved ion energy distribution functions (IEDFs) at tested frequencies and waveforms.
• Demonstrated HSRPA effectiveness under conditions mimicking HETs.

Conclusions:

• The HSRPA is effective for time-resolved ion energy measurements in plasma.
• This diagnostic provides a viable alternative for studying HETs and similar plasma devices.
• The study validates HSRPA's performance at higher frequencies and beam potentials than previously investigated.