Electron Beam Control Assembly for Space-Charge Neutralization
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Solution Overview
Problem
Conventional scanning electron beam scanners face challenges in maintaining electron beam space-charge neutralization, leading to beam expansion and focusing difficulties, particularly in medical and rapid imaging applications, due to the high cost and complexity of cryopumps and pressure control systems required to achieve the necessary vacuum pressure.
Innovation Solution
The implementation of an electron beam production and control assembly that includes a vacuum chamber with a focusing unit and a target with active and inactive sections, where the electron beam is directed to impinge on the active section for imaging and the inactive section for ion accumulation, allowing continuous operation and reducing the need for frequent regeneration of ions, thereby minimizing time delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cryopumps and pressure control servo-valves are used to maintain vacuum pressure at 10^-6 Torr, then electron beam space-charge neutralization is achieved, but system cost and complexity increase significantly
Solution Approach 1:
The patent extracts and eliminates the complex vacuum system components (cryopumps and servo-valves) by introducing a gas injection system that maintains neutralization through controlled gas pressure rather than high vacuum, thereby removing the need for sophisticated vacuum maintenance equipment
Solution Approach 2:
The invention changes the operating pressure parameter from high vacuum (10^-6 Torr) to controlled low vacuum conditions, fundamentally altering how space-charge neutralization is achieved and eliminating the need for complex vacuum control systems
2Use of energy by moving object
If the electron gun is deactivated between scans to save energy, then power consumption decreases, but ion accumulation is lost and re-neutralization time delays occur
Solution Approach 1:
The patent applies preliminary action by continuously maintaining ion accumulation in the chamber between scans through controlled gas injection, so that when the electron gun is reactivated, neutralization is already prepared and no time delay occurs
Solution Approach 2:
The invention ensures continuity of useful action by maintaining the ionizing gas environment continuously between scans, allowing the electron beam to be rapidly re-established without waiting for ion regeneration, thus eliminating idle time while managing power consumption
3Productivity
If higher beam current is used to improve imaging speed, then scan speed increases, but space-charge repulsion increases causing beam expansion and focusing difficulties
Solution Approach 1:
The patent introduces positive ions as an intermediary substance that mediates the space-charge repulsion between electrons, allowing high beam currents to be used without beam expansion by providing electrostatic counterbalancing through the ion cloud
Solution Approach 2:
The invention changes the electrical environment parameter by introducing positive charge carriers (ions) that alter the net charge density in the beam path, enabling high current operation while maintaining beam focus through modified electrostatic conditions
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 solution enables continuous operation of the scanning electron beam system, reduces the time required for space charge neutralization, and decreases the overall system complexity and cost by maintaining ion accumulation between scans, improving performance and efficiency in applications like cardiac scanners and baggage handling systems.
Implementation Method 1
the negatively charged electrons in the beam interact with the gas creating positive ions
Implementation Method 2
The focusing unit directs the beam towards the target in a converging manner to impinge on the target
Data Source
AI summary
An electron beam production and control assembly includes a vacuum chamber, a beam source, and a target. The target has an active section and an inactive section. The active section is adapted to generate x-rays when the beam impinges on the x-ray producing section. The electron beam production and control assembly also includes a focusing unit positioned along the chamber at a location intermediate the rearward end and the forward end. The focusing unit directs the beam towards the target in a converging manner to impinge on the target. The focusing unit sweeps the beam along a scanning path over the active section of the target. The focusing unit moves the beam to a retrace path on the inactive section of the target between sweeps of the scanning path to maintain ion accumulation in the beam between sweeps over the active section.