Suppressive Electrode for X-Ray Target Assembly
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Solution Overview
Problem
Bipolar x-ray emission apparatuses face instability due to high voltage breakdowns caused by electron acceleration towards the insulating element, leading to potential vacuum breakdown and loss of high voltage stability.
Innovation Solution
A suppressive electrode is introduced, extending from the insulating element towards the conductive wall, designed to divert and capture electrons emitted from the triple junction, reducing the electric field component towards the insulating element and stabilizing the high voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the potential of the source relative to the walls of the vacuum chamber is increased to achieve higher accelerating potentials, then the electron beam energy and x-ray emission energy are improved, but the risk of vacuum breakdown and dissipation of the high potential difference increases
Solution Approach 1:
The vacuum chamber is divided into two separate chambers: a first vacuum chamber containing the electron source held at a high negative potential, and a second vacuum chamber containing the x-ray target held at a high positive potential. Each chamber is independently maintained at vacuum conditions and can be independently sealed, allowing the system to achieve high total accelerating potential while keeping the potential difference across each chamber's walls manageable and reducing vacuum breakdown risk.
2Power
If a bipolar system is used with high negative potential between the electron source and chamber walls and high positive potential between the chamber walls and the x-ray target, then the total accelerating potential is increased while the apparatus size is reduced, but the stability of the positive part of the apparatus (high-voltage target portion) deteriorates due to electron acceleration towards the insulating element
Solution Approach 1:
An insulating element is introduced as an intermediary component to electrically isolate the high voltage target from the vacuum chamber walls while allowing the target to be held at a high positive potential. This insulating element prevents direct electrical contact between the high voltage portion and the chamber, stabilizing the high voltage configuration by eliminating leakage paths and reducing the risk of discharge.
3Reliability
If the size of the vacuum chamber is increased to mitigate vacuum breakdown risk, then the safety margin against vacuum breakdown is improved, but the apparatus becomes bulky, expensive and difficult to manufacture
Solution Approach 1:
The vacuum system is segmented into two separate vacuum chambers, each maintaining vacuum conditions independently. This allows each chamber to be compact in size while the system as a whole achieves the high accelerating potentials needed for high-energy x-ray emission. The segmentation enables high reliability without requiring a single large vacuum chamber, thus avoiding increased bulk and manufacturing complexity.
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 suppressive electrode effectively suppresses electron acceleration towards the insulating element, reducing the risk of vacuum breakdown and maintaining a stable high voltage, allowing for higher electron voltages and x-ray energies, enhancing x-ray penetration and resolution in imaging systems.
Implementation Method 1
designed to divert and capture electrons emitted from the triple junction, reducing the electric field component towards the insulating element
Implementation Method 2
x-ray emission is achieved by bringing a beam of accelerated electrons into interaction with a target of an x-ray generating material
Implementation Method 3
Thermionic emission, for example, may be used to generate appropriate electrons for acceleration
Data Source
AI summary
A target assembly for an x-ray emission apparatus, the apparatus assembly including: a vacuum chamber having at least one conductive wall; an insulating element projecting through the conductive wall; a conductive high voltage element extending along the insulating element from outside the chamber to an end portion of the insulating element furthest from the conductive wall; an x-ray-generating target arranged at the end portion of the insulating element and electrically connected to the high voltage element; and a suppressive electrode arranged at the end portion of the insulating element and configured to suppress acceleration toward the outer surface of the insulating element of electrons which are emitted from a junction between the outer surface of the insulating element and an inner surface of the conductive wall.