Atmospheric Glow Plasma Stabilization via Displacement Current Control
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Solution Overview
Problem
Atmospheric Pressure Glow discharge plasmas are unstable when impurities are present, leading to a transition from glow to arc, which results in uneven surface treatment and high current densities, making it difficult to maintain a stable and uniform plasma for material surface modification.
Innovation Solution
The method involves controlling the AC plasma energizing voltage to provide a sharp relative decrease in displacement current before the pulse maximum, preventing filament formation by managing the displacement current's sign and rate of change, especially using a dielectric material on the electrodes to control voltage variation and secondary electron emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC plasma energizing voltage is applied to generate glow discharge plasma, then plasma is produced for surface treatment, but plasma becomes unstable and transitions to arc discharge when impurities are present
Solution Approach 1:
The patent applies a preliminary voltage spike before the main AC plasma energizing voltage pulse. This preliminary action prepares the plasma by controlling electron emission and ionization processes in advance, preventing the exponential growth of ionization that leads to glow-to-arc transition. The preliminary voltage spike occurs at a controlled rate of change, establishing stable plasma conditions before the main treatment phase begins.
Solution Approach 2:
The patent changes the temporal parameters of the applied voltage by introducing a specific waveform structure with a preliminary spike followed by the main pulse. The rate of change of voltage (dV/dt) is carefully controlled during different phases: the preliminary spike has a controlled rising edge, followed by a main pulse with specific duration and amplitude. This parameter modulation prevents the conditions that lead to arc discharge while maintaining effective plasma generation for surface treatment.
2Productivity
If high current density plasma is generated, then plasma effectiveness increases, but filamentary discharge and uneven surface treatment occur
Solution Approach 1:
The patent employs periodic pulsed voltage application with a specific waveform structure. Each pulse cycle includes a preliminary voltage spike followed by a main treatment pulse, creating periodic plasma generation. This periodic action allows the plasma to be regenerated in a controlled manner, maintaining uniform current distribution across the electrode surface and preventing the formation of unstable filamentary discharges that would cause uneven treatment.
Solution Approach 2:
The preliminary voltage spike in each pulse cycle prepares the plasma by initiating controlled ionization and electron emission before the main treatment phase. This preliminary action ensures that when the main pulse arrives, the plasma is already in a stable, uniform state ready for effective surface treatment, preventing the development of high current density filaments that would compromise treatment uniformity.
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 stabilizes the glow plasma, preventing the transition to filamentary states, ensuring a uniform and stable plasma distribution for effective surface treatment, even in the presence of impurities, and reduces the risk of arcing and uneven treatment.
Implementation Method 1
Atmospheric Pressure Glow (APG) discharge is used in practice, among others, for non-destructive material surface modification. Glow discharge plasmas are relatively low power density plasmas, typically generated under atmospheric pressure conditions or partial vacuum environments.
Implementation Method 2
controlling the AC plasma energizing voltage to provide a sharp relative decrease in displacement current before the pulse maximum, preventing filament formation by managing the displacement current's sign and rate of change
Implementation Method 3
using a dielectric material on the electrodes to control voltage variation and secondary electron emission
Implementation Method 4
Atmospheric Pressure Glow (APG) discharge is used in practice, among others, for non-destructive material surface modification
Data Source
AI summary
Method and apparatus for generating and sustaining a glow discharge plasma in a plasma discharge space comprising at least two spaced electrodes. The method and apparatus are arranged for performing the steps of introducing in the discharge space a gas or gas mixture under atmospheric pressure conditions, energizing the electrodes by applying an AC energizing voltage (Va) to the electrodes, and controlling the energizing voltage (Va) such that at plasma generation a sharp relative decrease of displacement current is provided.