X-Ray Generator Filament Control for Pulsed Imaging Tube Life
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Solution Overview
Problem
Existing X-ray sources, particularly those used in pulsed X-ray imaging, face issues with cathode filament wear-out due to evaporation of tungsten, necessitating improved methods to extend filament lifetime and maintain accurate temperature control during pulsed operation.
Innovation Solution
A controller for a high voltage generator that manages X-ray pulses with emission pauses, using a blanking current to lower the filament temperature to an intercooler level where a non-zero emission current is measurable, followed by a boosting current to return to operational temperature, thereby reducing filament degradation and improving temperature control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the filament temperature is repeatedly changed via boosting and blanking to reduce wear, then filament lifetime is extended, but temperature drift and deviations occur over multiple pulses
Solution Approach 1:
The patent implements a feedback mechanism by measuring the emission current at the intercooler filament temperature and using this measurement to determine the actual filament temperature. The controller then adjusts the blanking and boosting currents based on this feedback to maintain accurate temperature control over multiple pulses, resolving the temperature drift issue while preserving the extended lifetime benefit
Solution Approach 2:
The patent replaces direct temperature measurement with an indirect electrical measurement system. Instead of measuring temperature directly, the system measures the emission current which correlates to temperature, and uses this electrical signal to control the filament temperature profile. This substitution enables accurate temperature monitoring without direct thermal contact
2Loss of substance
If the filament temperature is reduced to extend lifetime, then tungsten evaporation is minimized, but emission current measurement becomes difficult at very low temperatures
Solution Approach 1:
The patent optimizes the intercooler filament temperature parameter to a specific range that balances two competing requirements: low enough to minimize tungsten evaporation and extend filament lifetime, but high enough to maintain measurable emission current. This parameter optimization resolves the contradiction by finding the optimal operating point that satisfies both constraints
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 method enhances filament lifetime by minimizing degradation during pulsed operation while ensuring accurate temperature monitoring and calibration, allowing for precise control of X-ray emission.
Implementation Method 1
provide an operational filament current to heat a filament of a cathode of the X-ray source to an operational filament temperature
Implementation Method 2
the filament current heats the filament, causing the filament to expel electrons (thermionic emission), creating a space charge
Data Source
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AI summary
A high voltage generator for an X-ray source is controlled to provide: power to the X-ray source to generate a plurality of X-ray pulses during a pulsed X-ray imaging run, wherein subsequent X-ray pulses of the plurality of X-ray pulses are temporally separated by a respective emission pause comprising a first part and a second part; an operational filament current to heat a filament of a cathode of the X-ray source to an operational filament temperature during the plurality of X-ray pulses to generate a desired X-ray imaging emission current during the X-ray pulses; a blanking filament current that is lower than the operational filament current to allow the filament temperature to decrease during the first part of the emission pauses, such that the filament temperature reaches an intercooler filament temperature, wherein the intercooler temperature is (i) lower than the operational filament temperature and (ii) at a level resulting in a non-zero emission current at an operational X-ray source voltage when the filament is at the intercooler filament temperature; and a boosting filament current that is higher than the blanking filament current to increase the filament temperature from the intercooler filament temperature to the operational filament temperature during the second part of the emission pauses.