Thoriated Tungsten Cathode Tip for Discharge Lamp Flicker
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Solution Overview
Problem
In short arc type discharge lamps, the emitter substance at the cathode tip end is not utilized efficiently due to insufficient supply from the inner portion to the surface, leading to decreased electron emission characteristics and flicker issues as the substance depletes.
Innovation Solution
The cathode is designed with a thoriated tungsten tip end part containing thorium oxide particles that are coated with thorium, allowing them to migrate to the higher temperature surface, ensuring sufficient supply and extending the lamp's flicker durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If emitter substance is contained in the cathode inner portion, then the quantity of emitter substance is increased, but the supply from inner portion to surface becomes insufficient due to low temperature diffusion
Solution Approach 1:
The cathode is pre-configured with emitter substance (thorium oxide particles coated with thorium) in the inner portion before operation. This preliminary placement allows the emitter substance to be ready for supply when needed, and the high temperature operation automatically activates the diffusion process to transport the pre-positioned emitter substance to the surface where it is needed for electron emission.
Solution Approach 2:
The invention utilizes the temperature parameter difference between the cathode inner portion and surface. By operating the cathode at high temperature, the diffusion coefficient increases, enabling effective transport of emitter substance from the inner portion to the surface. The temperature parameter change activates the diffusion process that was insufficient at lower temperatures.
2Reliability
If emitter substance is evaporated and consumed at the cathode surface, then electron emission characteristics are maintained, but the emitter substance depletes leading to flicker occurrence
Solution Approach 1:
The cathode system performs self-service by automatically replenishing the emitter substance at the surface through heat diffusion from the inner portion. The high temperature operation naturally drives the diffusion process, eliminating the need for external replenishment systems. The emitter substance is continuously supplied from the inner portion to the surface where it is consumed, creating a self-sustaining cycle that extends flicker durability.
3Reliability
If thorium oxide particles are coated with thorium, then the migration to high temperature surface is enhanced, but the manufacturing complexity increases
Solution Approach 1:
Thorium coating acts as an intermediary substance between the thorium oxide particles and the tungsten matrix. This intermediate thorium layer facilitates the migration of emitter substance to the high temperature surface by providing a diffusion pathway. The thorium coating simplifies the overall manufacturing process compared to creating complex graded structures, as it can be applied through conventional coating techniques.
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 thorium oxide particles effectively migrate to the surface, preventing depletion and significantly improving the electron emission characteristics and extending the lamp's durability by ensuring continuous supply to the high-temperature surface.
Implementation Method 1
the quantity of the emitter substance being supplied to the cathode tip end surface from the inner portion of the cathode having a lower temperature by means of heat diffusion is low
Implementation Method 2
the quantity of the emitter substance being evaporated and consumed by means of the heat of the surface of the cathode tip end where the temperature becomes highest
Data Source
AI summary
A short arc type discharge lamp wherein a cathode and an anode are arranged opposite to each other in an interior of a light emitting tube and said cathode comprises a main part made from tungsten and a tip end part made from thoriated tungsten, wherein thorium oxide particles having been peripherally coated with thorium are contained in the tip end part of said cathode.