Inductively Coupled Plasma Source Liquid Cooling and Arcing Prevention
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Solution Overview
Problem
Inductively coupled plasma sources face design challenges such as preventing gas-phase discharges during high voltage operation, efficiently dissipating heat, and maintaining electrical isolation while allowing gas replenishment and RF coil placement close to the plasma for efficient power transfer.
Innovation Solution
The plasma source is surrounded by a liquid for cooling and electrical insulation, and gas is introduced through a high-voltage flow restrictor to minimize arcing, with a split Faraday shield positioned to reduce capacitive coupling and facilitate efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gas is introduced into the high voltage plasma chamber to replenish gas, then gas replenishment is achieved, but gas-phase discharge (arcing) may occur which would damage the system
Solution Approach 1:
The patent introduces a liquid medium (typically water or dielectric fluid) as an intermediary substance between the gas supply and the plasma chamber. This liquid serves multiple functions: it provides electrical insulation to prevent arcing, acts as a cooling medium, and allows controlled gas transfer through it. The liquid barrier eliminates the direct electrical contact that would cause discharge while still permitting gas to diffuse or flow through to replenish the plasma chamber.
Solution Approach 2:
The patent employs hydraulic principles by using a liquid-filled environment to control gas flow into the plasma chamber. The liquid medium allows gas to be introduced in a controlled manner through pressure differential while the liquid's incompressibility and insulating properties prevent electrical discharge. This hydraulic approach replaces direct gas-phase introduction with a liquid-mediated delivery system.
2Power
If RF coils are placed close to the plasma for efficient power transfer, then power transfer efficiency is improved, but capacitive coupling increases which complicates the power supply design
Solution Approach 1:
The patent uses a liquid dielectric medium as an intermediary between the RF coils and the plasma chamber. This liquid layer allows the coils to be positioned close to the plasma for efficient inductive coupling while the liquid's dielectric properties reduce unwanted capacitive coupling. The intermediary substance enables close proximity positioning without the direct electrical contact that would create complex capacitive coupling issues.
3Productivity
If the plasma source is made compact and powerful for efficient beam formation, then beam formation efficiency is improved, but heat generation increases making cooling difficult
Solution Approach 1:
The patent merges multiple functions into the liquid medium surrounding the plasma chamber: electrical insulation, cooling, and gas delivery. By combining these functions in a single integrated system, the design achieves compact dimensions without sacrificing cooling capability. The liquid medium is in direct thermal contact with the plasma chamber, enabling efficient heat removal despite the compact and powerful design.
Solution Approach 2:
The patent employs hydraulic cooling by circulating liquid through channels in or around the plasma chamber. This liquid cooling system efficiently removes heat from the compact plasma source through forced convection, allowing high power operation without excessive temperature rise. The hydraulic approach provides superior heat transfer compared to air cooling or radiative cooling.
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 design achieves dense, quiescent, and high-potential plasma with efficient cooling and capacitive screening, reducing the risk of arcing and heat-related issues, while maintaining high voltage isolation and efficient power transfer.
Implementation Method 1
The plasma source is surrounded by a liquid for cooling
Implementation Method 2
The plasma source is surrounded by a liquid for cooling and electrical insulation
Implementation Method 3
The RF antenna provides energy to maintain the gas in an ionized state within the chamber
Implementation Method 4
Inductively coupled (IC) plasma sources have advantages over other types of plasma sources
Implementation Method 5
Inductively coupled plasma ion sources may use a split Faraday shield to reduce capacitive coupling between the coil and the plasma
Implementation Method 6
The ion or electron source is typically maintained at a high positive or negative voltage, and the sample is typically maintained at or near ground potential
Data Source
AI summary
An inductively coupled plasma source for a focused charged particle beam system includes a dielectric liquid that insulates and cools the plasma chamber. A flow restrictor at an electrical potential that is a large fraction of the plasma potential reducing arcing because the voltage drop in the gas occurs primarily at relative high pressure.