Hermetically-Sealed RF Feed-Through for CO2 Laser
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Solution Overview
Problem
Existing RF power feed-through designs for high-power CO2 lasers face challenges such as difficulty in matching impedance components within a shielded enclosure, excessive heating, and corona discharge issues, particularly at higher power levels like 20 kW, which affect the reliability and efficiency of the laser system.
Innovation Solution
The RF feed-through design incorporates springably compressible connecting members for secure electrode contact, a fluid-cooled central electrode, and an integrated series capacitor arrangement to reduce voltage and prevent arcing, along with a re-entry transmission line to minimize series inductance and series capacitance adjustments, addressing the impedance matching and overheating problems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional RF feed-through designs are used for high-power CO2 lasers, then the laser can operate at higher power levels, but excessive heating occurs in the feed-through and vacuum seals deteriorate
Solution Approach 1:
The patent extracts the problematic vacuum seal material (indium) from the high-temperature zone by placing it in a cooled region of the feed-through structure. The indium seal is positioned where cooling channels are located, separating the sealing function from the high-temperature RF current carrying path, thereby allowing high power operation without seal deterioration
Solution Approach 2:
The patent introduces a ceramic insulator as an intermediary component between the RF feed-through center conductor and the vacuum chamber wall. This ceramic barrier provides both electrical insulation and thermal isolation, preventing heat transfer from the high-power RF path to the vacuum seal, enabling high power operation while maintaining seal integrity
2Reliability
If larger inductors and capacitors are used for impedance matching at high power, then impedance matching improves, but the device size increases and cannot fit within the shielded enclosure
Solution Approach 1:
The patent changes the electrical parameters of the feed-through structure itself to provide impedance matching functionality. By adjusting the geometry, materials, and configuration of the feed-through components (center conductor dimensions, insulator properties, cooling channel arrangement), the structure achieves the required impedance transformation without requiring separate large inductor and capacitor components, thereby maintaining compact enclosure size
Solution Approach 2:
The patent makes the feed-through structure multi-functional by integrating impedance matching capability into the basic feed-through components. The center conductor, insulator, and cooling channels are designed to simultaneously perform their primary functions (RF power transmission, electrical insulation, thermal management) while also providing the necessary impedance transformation, eliminating the need for separate matching network components
3Productivity
If RF power transmission is increased to achieve higher laser output, then laser efficiency improves, but corona discharge and arcing occur between feed-through connections and electrodes
Solution Approach 1:
The patent applies preliminary action by providing pre-cooled connecting members that are already at low temperature before making electrical contact with the electrodes. The cooling channels are positioned to cool the connection points in advance, preventing corona discharge and arcing from occurring when high RF power is transmitted, thereby enabling efficient high-power operation without harmful discharges
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 results in a more reliable, efficient, and compact RF feed-through that reduces voltage requirements, prevents corona discharges, and accommodates higher power levels without compromising the sealed-off laser chamber integrity, enabling reliable operation of CO2 lasers with average power of 1 kW or greater.
Implementation Method 1
first and second springably compressible connecting members on a side thereof within the enclosure and attached respectively to a live electrode and a ground connection of the feed-through
Implementation Method 2
a fluid-cooled central electrode
Data Source
AI summary
A carbon-dioxide (CO2) gas-discharge slab laser includes elongated discharge-electrodes in a sealed enclosure. Radio Frequency (RF) power is supplied to the electrodes via an impedance matching network and a co-axial electrical low inductance transmission line feed-through sealed to the enclosure. The feed-trough includes two spring contacts which are configured to be spring compression push-fit in grooves in edges of the discharge-electrodes. A central conductor of the feed-through is fluid cooled. A capacitor of the impedance matching network is assembled on the central conductor as an integral part of the feed-trough.