MgF2 Window Sealing for VUV Plasma Light Sources
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Solution Overview
Problem
High-brightness continuous optical discharge (COD) light sources face challenges in expanding the vacuum ultraviolet (VUV) radiation spectrum due to limitations in transparency and mechanical properties of existing window materials, particularly magnesium fluoride (MgF2), and issues with sealing at high temperatures and pressures.
Innovation Solution
The use of MgF2 as the window material for outputting plasma radiation, with surfaces perpendicular to the optical axis to mitigate double refraction, and sealing with glass cement to ensure reliability at high temperatures, combined with an iron-nickel alloy housing to match thermal expansion coefficients, allows for stable operation and broader VUV spectrum expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If MgF2 is used as window material to expand VUV spectrum, then transparency in VUV range is improved, but sealing reliability at high temperature and pressure deteriorates
Solution Approach 1:
The patent changes the sealing method from mechanical sealing to chemical bonding using glass cement, and modifies the operating temperature parameter to match the glass cement's service temperature range (up to 500°C), thereby achieving reliable sealing of MgF2 windows under high temperature and pressure conditions while maintaining VUV transparency
Solution Approach 2:
The patent uses composite sealing structures combining glass cement with metal flanges and MgF2 windows, creating a multi-material assembly that leverages the transparency of MgF2 in VUV range while using glass cement's chemical bonding properties to achieve reliable sealing at high temperatures and pressures
2Illumination intensity
If chamber temperature is increased to 600-900K for high-brightness COD operation, then radiation brightness is improved, but sealing of optical windows becomes more difficult
Solution Approach 1:
The patent adjusts the operating temperature parameter to be compatible with glass cement sealing (up to 500°C), and modifies the sealing method to chemical bonding which maintains integrity at high temperatures, thereby enabling both high-brightness operation and reliable window sealing
Solution Approach 2:
The patent introduces glass cement as an intermediary sealing material between metal flanges and MgF2 windows, which provides chemical bonding capability that maintains sealing reliability at high operating temperatures (600-900K) required for high-brightness COD operation
3Stability of the object's composition
If gas pressure is increased above 50 atm for high-brightness COD, then radiation stability is improved, but mechanical stress on windows increases
Solution Approach 1:
The patent uses composite sealing structures with glass cement providing chemical bonding that distributes mechanical stress from high gas pressure (above 50 atm) across the window assembly, thereby maintaining both high brightness stability and window structural integrity under elevated pressure conditions
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 results in higher-brightness, stable light sources with an expanded VUV radiation spectrum, maintaining reliability and minimizing convective turbulence for optimal performance.
Implementation Method 1
A stationary gas discharge sustained by laser radiation in pre-created relatively dense plasma is known as continuous optical discharge (COD)
Implementation Method 2
A COD, sustained in the gas-filled chamber by a focused beam of a continuous wave (CW) laser
Implementation Method 3
LiF MgF2 have the shortest-wave boundary of transparency, around 110 nm
Implementation Method 4
The coefficients of linear thermal expansion (CLTE) of the glass cement, material of the sleeves and the housing are matched with the CLTE of the crystal magnesium fluoride
Implementation Method 5
By means of a pulsed laser system (9) at least one pulsed laser beam (10) is generated, which is focused in the chamber region designed for sustenance of the radiating plasma (2) and provides for optical breakdown and generation of initial plasma
Data Source
AI summary
A light source with radiating plasma sustained in the gas-filled chamber by a focused beam of CW laser. The gas is inert gas with a purity of at least 99.99%. The chamber contains a metal housing with at least one window made of MgF2 for outputting a plasma radiation. Each window is located in a hole of the housing on the end of a sleeve and is soldered to the sleeve by means of glass cement, and each sleeve is welded to the hole of the metal housing on the outside seam. The sleeves and the housing are made of an alloy with a coefficient of linear thermal expansion (CLTE), matched with the CLTE of the MgF2 crystal in the direction perpendicular to the optical axis of the MgF2 crystal. The technical result consists in expanding the radiation spectrum of the light source into the VUV region.