Plasma Magnetic Field Control via Axial Current Pulses

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Solution Overview

Problem

Magnetized plasma stability is challenging due to the differential decay rates of poloidal and toroidal magnetic fields, leading to plasma instability and reduced confinement, which affects the magnetic lifetime and fusion performance.

Innovation Solution

A system and method that utilize a controller with measuring probes and a power source to adjust the inductance-to-resistance (L/R) time constant and provide additional axial current pulses to maintain a stable toroidal to poloidal magnetic field ratio, preventing the q-factor from reaching rational values that cause instability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If additional axial current pulses are provided to increase toroidal field, then plasma stability is improved, but device complexity increases

Engineering Contradiction:
Improveplasma stabilityVSAvoiddevice complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The controller continuously monitors plasma parameters through measuring probes and automatically adjusts the axial current pulse timing and magnitude based on real-time feedback. This closed-loop control maintains plasma stability by detecting deviations from optimal conditions and applying corrective current pulses, eliminating the need for complex manual intervention while ensuring stable plasma configuration.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the axial current pulse characteristics (timing, duration, magnitude) based on real-time plasma conditions. The controller modifies pulse parameters adaptively to maintain optimal toroidal to poloidal magnetic field ratio, allowing the plasma to remain stable despite changing conditions without requiring a statically complex device architecture.

Inventive Principle:
Principle #15Dynamics

2Duration of action of stationary object

If L/R time constant is adjusted to be shorter than shortest decay time of poloidal field, then plasma magnetic lifetime is extended, but control precision requirements increase

Engineering Contradiction:
Improvemagnetic lifetimeVSAvoidcontrol precision
Core Design Contradiction:
Duration of action of stationary objectVSManufacturing precision

Solution Approach 1:

The system optimizes the L/R time constant of the axial current pulse circuit to be shorter than the shortest decay time of the poloidal field. This parameter adjustment ensures that the toroidal field decays at a controlled rate, extending plasma magnetic lifetime. The controller compensates for the stricter timing requirements by using precise pulse generation and synchronization with plasma diagnostics.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The system replaces mechanical or manual timing mechanisms with electronic control systems that can achieve precise timing control. The controller uses electronic pulse generation and digital timing circuits to achieve the required precision in L/R time constant adjustment, eliminating the need for mechanically complex timing mechanisms.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If measuring probes are positioned at various radial, axial and angular positions, then plasma parameter measurement accuracy is improved, but device complexity increases

Engineering Contradiction:
Improvemeasurement accuracyVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The measurement system is divided into multiple independent probe positions distributed at various radial, axial, and angular locations. Each probe measures local plasma parameters independently, and the controller integrates these segmented measurements to reconstruct the overall plasma state. This segmentation provides comprehensive spatial coverage and high measurement accuracy without requiring a single complex measurement device.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The measuring probes are designed with multi-functionality, capable of measuring multiple plasma parameters (temperature, density, magnetic field) at each position. This universal probe design reduces the total number of specialized devices needed while maintaining high measurement accuracy across all plasma parameters and spatial locations.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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

This approach extends the plasma magnetic lifetime by maintaining stability and improving confinement, avoiding 'over-sustained' or 'under-sustained' plasma conditions, thereby enhancing the plasma's heat confinement and fusion performance.

Implementation Method 1

The power source is configured to provide one or more additional, axial, current pulses to increase a toroidal field of the plasma

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

A plurality of measuring probes positioned at various radial, axial and angular positions in a wall of a flux conserving chamber are configured to provide signals of at least one parameter of the plasma

Methodology Applied
Scientific EffectElectromagnetic field detection: Magnetic Field

Data Source

PatentEP3183944B1System and method for controlling plasma magnetic field
Publication Date: 2018.10.03 GENERAL FUSION INC
  • EP3183944B1 patent drawingFigure 1
  • EP3183944B1 patent drawingFigure 2A~2B
  • EP3183944B1 patent drawingFigure 3A~3B

AI summary

Examples of a system for generating and confining a compact toroid are disclosed. The system comprises a plasma generator for generating magnetized plasma, a flux conserver for receiving the compact toroid, a power source for providing current pulse and a controller for actively controlling a current profile of the pulse to keep plasma's q-profile within pre- determined range. Examples of methods of controlling a magnetic lifetime of a magnetized plasma by controlling a current profile of the current pulse are disclosed.