Variable-Pitch X-Ray Tube Filament for Uniform Heating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing X-ray tube filaments suffer from nonuniform temperature distribution, leading to reduced lifespan due to higher temperatures at the center and ion bombardment, which affects electron beam density and X-ray focus brightness.
Innovation Solution
A coiled filament with a central region of constant coil pitch and end regions with progressively reduced coil pitch, combined with an eccentric Wehnelt electrode configuration to deflect the electron-beam-irradiation region, ensuring uniform temperature distribution and reduced ion bombardment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant coil pitch is used in the filament, then the manufacturing is simple, but the temperature distribution becomes nonuniform with highest temperature at the center
Solution Approach 1:
The filament is designed with different coil pitch characteristics in different regions: the central region has a constant, larger coil pitch while the end regions have progressively smaller coil pitches. This local differentiation creates higher density at the ends to compensate for heat loss, achieving uniform temperature distribution along the filament length.
2Quantity of substance
If the coil pitch is made dense at the center and sparse at the ends, then the electron density distribution becomes Gaussian, but the temperature distribution remains nonuniform with center temperature higher than ends
Solution Approach 1:
Instead of making the coil pitch dense at the center (as in prior art), the invention inverts the approach by making the coil pitch sparse at the center and dense at the ends. This inverted configuration compensates for the natural heat loss at the ends, achieving uniform temperature distribution while still providing adequate electron density.
3Power
If the filament operates at high temperature to maintain X-ray tube current, then the current output is sufficient, but the wire diameter wear increases and lifetime is reduced
Solution Approach 1:
The invention changes the geometric parameters of the filament, specifically the coil pitch distribution, to achieve more uniform temperature distribution. This allows the filament to operate at lower maximum temperatures while maintaining the required X-ray tube current, thereby reducing wire diameter wear and extending filament lifetime.
4Shape
If the electron-beam-irradiation region is centered on the filament, then the X-ray focus is symmetric, but the filament is subject to ion bombardment that reduces lifetime
Solution Approach 1:
The invention introduces asymmetry in the filament configuration by using different coil pitch characteristics in the central and end regions. This asymmetric design serves two purposes: it maintains adequate electron density for X-ray generation while reducing ion bombardment effects on the filament, thereby extending filament lifetime without completely sacrificing focus symmetry.
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 solution achieves a uniform longitudinal temperature distribution, extending the filament's lifespan by minimizing both temperature-related wear and ion-induced erosion, while maintaining consistent X-ray focus brightness.
Implementation Method 1
The present invention relates to a filament for an X-ray tube... a coiled filament with an improvement in temperature distribution uniformity... uniform temperature distribution as far as possible over the whole length of the filament
Implementation Method 2
A coiled filament for an X-ray tube preferably gives itself a uniform temperature distribution as far as possible over the whole length of the filament... intensity distribution of an electron beam emitted from the filament
Data Source
AI summary
A coiled filament for an X-ray tube has a varied coil pitch to obtain a good uniformity of the longitudinal temperature distribution. The filament has a central region including plural turns having a same coil pitch, and end regions which include plural turns each of which has a coil pitch smaller than the coil pitch of the central region. The coil pitches of the plural turns of the end regions are reduced one by one by a same variation from a turn close to the central region toward an outermost turn. A value of Δp/p is within a range of 0.015 to 0.1 and k/n is within a range of 0.3 to 0.8, where p is the coil pitch of the central region, Δp is the coil pitch variation of the end regions, n is a total number of turns of the filament, and k is a sum of numbers of turns of the end regions. The k/n preferably satisfies the following equation:k/n=0.72−4.66(Δp/p)±0.12.