Short Arc Mercury Lamp Anode Design for Radiation Stability
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Solution Overview
Problem
Short arc type mercury lamps with argon (Ar) gas enclosed experience a sudden decrease in radiation intensity beyond a certain usage time due to thermal stress and overheating, which is not observed with krypton (Kr) gas, but using Kr gas results in lower initial radiation intensity and elongated arcs, compromising luminance.
Innovation Solution
A short arc type mercury lamp design where Kr is used as the rare gas, with a specially configured anode having a taper portion and flat leading end surface, where the ratio of the anode's radius to the distance between electrodes satisfies 1−r/(d0×tan θ)≥0.66, allowing for increased light extraction without arc contraction, thus maintaining initial radiation intensity and preventing sudden decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Ar gas is enclosed in the short arc type mercury lamp, then the initial intensity of radiation is high, but the persistency ratio of intensity of radiation suddenly decreases after a certain usage time
Solution Approach 1:
The patent changes the type of rare gas from Ar to Kr, which has different thermal conductivity properties. This parameter change prevents the arc contraction effect that occurs with Ar, thereby avoiding the sudden decrease in radiation intensity while maintaining high initial radiation levels.
2Duration of action of stationary object
If Kr gas is enclosed in the short arc type mercury lamp, then the persistency ratio of intensity of radiation is maintained, but the initial intensity of radiation and luminance are reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform temperature distribution within the arc through the specific anode configuration. The anode structure with its particular geometry (tapered shape with specific angle and length ratios) generates localized thermal conditions that prevent arc elongation while maintaining high radiation intensity throughout the lamp's operational life.
3Illumination intensity
If the arc is contracted by Ar gas, then the current density is increased and luminance is improved, but thermal stress deforms the anode leading end surface
Solution Approach 1:
The patent changes the thermal conductivity parameter by substituting Ar with Kr gas. This parameter change eliminates the excessive arc contraction and current density concentration that cause thermal stress and anode deformation, thereby improving reliability while maintaining acceptable luminance levels.
Solution Approach 2:
The specific anode configuration creates localized thermal management that distributes heat more evenly across the anode structure, preventing the concentration of thermal stress at the leading end surface that occurs with Ar gas.
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 design achieves initial radiation intensity comparable to Ar-filled lamps while preventing sudden decreases in radiation persistency, enhancing lamp longevity and maintaining high radiation levels over extended usage.
Implementation Method 1
the different thermal conductivities of the gases. Since the mercury arc can contract at a higher thermal conductivity, the arc is elongated
Implementation Method 2
the anode has a taper portion at a leading end side and a flat leading end surface on a leading end thereof, and the anode satisfies the following formula: 1−r/(d0×tan θ)≧0.66, where r (mm) is a radius of the leading end surface of the anode, θ (°) is an angle between an electrode axis and the taper surface in an axial cross-section of the anode, and d0 (mm) is the distance between the cathode and the anode
Implementation Method 3
short arc type mercury lamps in which Hg and a rare gas are enclosed are used as a light source for exposing semiconductor, a liquid crystal display (LCD) or the like to light
Data Source
AI summary
A short arc type mercury lamp structure has Hg and a rare gas which are enclosed inside a light-emitting tube. Kr is enclosed as the rare gas. It is possible to realize the initial intensity of radiation at the same level as in the case in which Ar is enclosed and prevent a sudden decrease in the intensity of radiation when the lamp is lighted for a long time. The longevity of the lamp is greatly increased than that of a lamp in which Ar is enclosed. The anode satisfies the formula:1−r/(d0×tan θ)≧0.66,where r (mm) is the radius of the leading end surface of the anode, θ(°) is the angle between the electrode axis and the taper surface in the axial cross-section of the anode, and d0 (mm) is the inter-electrode distance.