Magnetic Field Plate for Electric Propulsion Backsputter Mitigation

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Solution Overview

Problem

The challenge of high backsputter rates during electric propulsion (EP) device testing in ground-based facilities, which affects the fidelity of performance and erosion rate measurements, making it difficult to predict in-space performance and lifetime, is exacerbated by increased power and the use of krypton and argon propellants, and current mitigation methods like graphite and angled beam dumps are inadequate for large vacuum facilities.

Innovation Solution

A system using a plate with a magnetic field generator disposed transverse to the thruster output plume, either with permanent magnets or solenoids, to trap electrons and slow down incoming ions, reducing backsputter by generating a magnetic field that impedes electron motion and adjusts the plate voltage to balance ion and electron flux.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If limited-duration testing is performed at higher facility pressure to reduce test time, then productivity increases, but backsputter rates increase causing measurement fidelity to deteriorate

Engineering Contradiction:

Improvetest speedVSAvoidmeasurement fidelity

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

A magnetic field generator is introduced as an intermediary component between the thruster and the chamber walls. This magnetic field acts as a mediator to trap electrons and reduce the energy of incoming ions, thereby decreasing backsputter rates to the thruster while allowing testing to proceed at higher pressures for improved productivity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The magnetic field strength is adjusted as a controllable parameter to optimize the balance between test duration and measurement fidelity. By varying the magnetic field strength, the system can adapt to different testing requirements while maintaining acceptable backsputter rates

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If beam targets are placed closer to the thruster to accelerate testing, then test duration decreases, but backsputter rates increase significantly

Engineering Contradiction:

Improvetest durationVSAvoidbacksputter contamination

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The magnetic field generator serves as a protective intermediary that enables close placement of beam targets without suffering from excessive backsputter contamination. The magnetic field traps electrons and reduces ion energy, allowing the target to be positioned closer to the thruster for accelerated testing

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If higher power thrusters are tested to evaluate advanced devices, then device capability increases, but facility pumping capacity requirements increase and backsputter contamination worsens

Engineering Contradiction:

Improvethruster powerVSAvoidthruster contamination

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The magnetic field generator acts as a protective intermediary for high-power thruster testing. By trapping electrons and reducing ion energy before they reach the chamber walls, it significantly reduces backsputter contamination to the thruster, enabling testing of advanced high-power devices without excessive contamination

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The magnetic field strength is adjusted as a controllable parameter to optimize protection against backsputter contamination for different power levels. This allows flexible adaptation to various thruster power requirements while maintaining acceptable contamination levels

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system effectively reduces backsputter rates by slowing ions to below the sputtering threshold, maintaining plume integrity and improving the accuracy of EP device testing, thereby enhancing the prediction of in-space performance and lifetime.

Implementation Method 1

A magnetic field generator disposed about or at the plate and configured to generate a magnetic field between the thruster and the plate

Methodology Applied

Scientific EffectMagnetic field generation: Electromagnetic Induction

Implementation Method 2

The magnetic field generator is oriented such that a magnetic field is generated transverse to the output plume

Methodology Applied

Scientific EffectLorentz force: Lorentz Force

Implementation Method 3

slow down incoming ions, reducing backsputter by generating a magnetic field that impedes electron motion and adjusts the plate voltage to balance ion and electron flux

Methodology Applied

Scientific EffectIon deceleration: Lorentz Force

Implementation Method 4

backsputter rates by slowing ions to below the sputtering threshold

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS20250224308A1Backsputter mitigation in electric propulsion testing

Publication Date: 2025.07.10 COLORADO STATE UNIV RES FOUND

AI summary

A system for mitigating backsputter to a thruster in a propulsion test facility includes a plate disposed in an output plume of the thruster and a magnetic field generator disposed about or at the plate and configured to generate a magnetic field between the thruster and the plate. The magnetic field generator is oriented such that a magnetic field is generated transverse to the output plume.