Cathode Gridding Voltage Control With Two-Stage Switching
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Solution Overview
Problem
Existing methods for controlling electron beam intensity in X-ray tubes, particularly in interventional imaging systems with unipolar cathodes and long cables, suffer from slow transitions, higher losses, and potential inaccuracies due to parasitic capacitance, making them unsuitable for modern imaging systems.
Innovation Solution
A multi-stage switching unit with separate control circuits for gridding and bias voltages is employed, allowing rapid transitions and precise voltage control by dividing the voltage change into two steps: a fast, low-precision initial step and a precise final step, using a first control circuit for gridding voltage and a second control circuit for bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single-stage voltage control method is used, then the device complexity is reduced, but the transition speed from gridding to bias voltage becomes slow and the control precision deteriorates
Solution Approach 1:
The voltage control is divided into two separate control circuits: a first control circuit for gridding voltage and a second control circuit for bias voltage. This segmentation allows each circuit to be optimized for its specific function, enabling fast transitions while maintaining precise control, thereby resolving the contradiction between transition speed and control precision without excessive complexity.
2Adaptability or versatility
If long cables are used to connect the control system, then the adaptability to modern interventional imaging systems is improved, but parasitic capacitance increases causing voltage control inaccuracies
Solution Approach 1:
The patent introduces an intermediary compensation mechanism that actively counteracts the effects of parasitic capacitance in long cables. The control circuits include compensation components that generate opposing voltage adjustments, thereby maintaining precise voltage control despite the presence of long cables connecting the system to modern interventional imaging equipment.
3Productivity
If rapid voltage transitions are implemented, then the productivity of X-ray exposure control is improved, but temporary voltage drops and energy losses increase
Solution Approach 1:
The control system performs preliminary actions by pre-charging capacitors and preparing voltage levels before the actual transition is needed. This allows rapid switching between gridding and bias voltages without causing large temporary voltage drops or excessive energy losses, as the energy is already stored and ready for immediate deployment.
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 enables fast and accurate control of electron beam intensity in X-ray tubes, minimizing temporary voltage drops and energy losses, suitable for modern interventional imaging systems with long cables.
Implementation Method 1
The cathode emits a stream of electrons in response to heat resulting from an applied electrical current via the thermionic effect
Implementation Method 2
to an electric field due to a high voltage applied between the cathode and the anode
Data Source
AI summary
Methods and systems are provided for controlling an electron beam generated by an X-ray tube assembly including a unipolar cathode with a long cable between driving electronics of the cathode and the X-ray tube. A voltage supplied to a gridding electrode of the cathode is controlled by a multi-stage switching unit including a first control circuit and a second control circuit. A bias voltage for switching the cathode on is generated by a high precision voltage source of the second control circuit, and a gridding voltage for switching the cathode off is generated by voltage sources of the first control circuit. A time taken to transition between the gridding voltage and the bias voltage is advantageously reduced by decreasing the supplied voltage to a common voltage (e.g., 0 V) in a first step, and then increasing the supplied voltage to the bias voltage or the gridding voltage in a second step.