Ferromagnetic Bar Shielding for RF Coil Eddy Current Reduction
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Solution Overview
Problem
The use of metallic enclosures in RF systems for plasma sources leads to unwanted capacitive and inductive parasitic effects, causing eddy current losses and reducing the efficiency of plasma processing.
Innovation Solution
A magnetic shield comprising a back-shell with a cage defined by an arrangement of ferro-magnetic bars is used to enclose the RF source coil, redirecting magnetic flux and reducing eddy current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If metallic enclosures are used in RF systems for plasma sources, then electro-magnetic compatibility and RF interference requirements are met, but eddy current losses increase and system efficiency decreases
Solution Approach 1:
A magnetic shield comprising a back-shell with a cage defined by an arrangement of ferro-magnetic bars is introduced as an intermediary component between the RF source coil and the metallic enclosure. This magnetic shield redirects magnetic flux and reduces eddy current losses while allowing the metallic enclosure to remain in place for EMC compliance.
Solution Approach 2:
The magnetic shield uses ferro-magnetic materials (such as nickel zinc ferrite, magnesium zinc ferrite, or manganese zinc ferrite) combined with a cage structure to create a composite shielding system that provides both magnetic flux redirection and eddy current reduction, addressing both RF interference and energy loss issues.
2Object-affected harmful factors
If metallic enclosures are used to enclose RF source coils, then electromagnetic shielding is provided, but capacitive and inductive parasitic effects increase
Solution Approach 1:
The magnetic shield acts as an intermediary that modifies the electromagnetic field distribution between the RF source coil and the metallic enclosure, reducing parasitic effects while maintaining the enclosure's electromagnetic shielding function.
Solution Approach 2:
The magnetic shield changes the magnetic flux distribution parameters by providing a dedicated path for magnetic field lines through the ferro-magnetic bars, thereby reducing inductive parasitic effects on the metallic enclosure while maintaining electromagnetic compatibility.
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 magnetic shield effectively reduces eddy current losses by 4% to 90% across different designs, enhancing the overall efficiency of the RF system and plasma processing.
Implementation Method 1
A magnetic shield comprising a back-shell with a cage defined by an arrangement of ferro-magnetic bars is used to enclose the RF source coil, redirecting magnetic flux and reducing eddy current losses
Implementation Method 2
the arrangement of ferro-magnetic bars defines an open cage having an open side; and wherein a bottom side of the RF source coil, when in use, faces the open side
Implementation Method 3
The magnetic shield effectively reduces eddy current losses by 4% to 90% across different designs, enhancing the overall efficiency of the RF system and plasma processing
Data Source
AI summary
In some examples, a magnetic shield for a plasma source is provided. An example magnetic shield comprises a back-shell. The back-shell includes a cage defined, at least in part, by an arrangement of bars of ferro-magnetic material. The cage is sized and configured to at least extend over a top side of an RF source coil for the plasma source.