VHF broadband coaxial adapter

A plasma processing system, comprising:

• a matching network;
• a resonating structure;
• and
• an apparatus coupling the matching network to the resonating structure, the apparatus configured to provide a broadband RF transition from the matching network to the resonating structure of the plasma processing system for frequencies ranging between 13 megahertz (MHz) and 220 MHz, the apparatus comprising:
• a conductive conical frustum having an open top base, an open bottom base, and a surface area coupling the open top base to the open bottom base, and
• a conductive cylinder positioned within the conductive conical frustum and having a closed bottom base and an open top base, the open top base of the conductive cylinder being connected to sidewalls of the open top base of the conductive conical frustum, the conductive cylinder having a height shorter than a height of the conductive conical frustum, the conductive cylinder having an interior volume coaxially nested within an interior volume of the conductive conical frustum.

An apparatus for a plasma processing system, the apparatus comprising:

• a conductive conical frustum having an open top base, an open bottom base, and a surface area coupling the open top base to the open bottom base, wherein a diameter of the top base is smaller than a diameter of the bottom base;
• and
• a conductive cylinder positioned within the conductive conical frustum and having a closed bottom base and an open top base, the open top base of the conductive cylinder being connected to sidewalls of the open top base of the conductive conical frustum, the conductive cylinder having a height shorter than a height of the conductive conical frustum, an interior volume of the conductive cylinder radially surrounded by an interior volume of the conductive conical frustum,
• wherein the conductive conical frustum and the conductive cylinder are configured to provide an impedance transition that minimizes RF reflections across multiple load conditions of the plasma processing system.