Pyroelectric Sealed Electron Beam for Compact API Ionization
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Solution Overview
Problem
Existing electron beam ionization sources for Atmospheric Pressure Ionization (API) devices face challenges with high voltage requirements, size, complexity, and inadequate current control, making them unsuitable for compact and robust applications, and pyroelectric crystal-based solutions struggle with stable voltage and current control, thermal conductivity issues, and short lifetimes.
Innovation Solution
A sealed electron beam tube using pyroelectric crystals with one end grounded and the other having a metallic feature to generate electrons, where the heating or cooling rate controls the current, and a thin window allows electron extraction while preventing gas leakage, eliminating the need for external accelerating voltages and high voltage feedthroughs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional electron beam units with high voltage cathodes are used, then electron energy can be controlled, but the device size becomes large and requires high voltage feedthroughs
Solution Approach 1:
The patent replaces the conventional high voltage electrical acceleration system with a thermal field emission system using pyroelectric crystals. Instead of using high voltage cathodes and electrical fields to accelerate electrons, the invention uses temperature-induced pyroelectric effects to generate and control electron emission, eliminating the need for high voltage feedthroughs and large power supplies
Solution Approach 2:
The patent changes the control parameter for electron emission from electrical voltage to temperature. By controlling the temperature of the pyroelectric crystal through heating or cooling, the electron emission and energy can be adjusted without requiring high voltage electrical control systems, thus reducing device size while maintaining energy control
2Volume of moving object
If pyroelectric crystals are used for electron beam generation, then device compactness is improved, but voltage and current control becomes difficult
Solution Approach 1:
The patent implements feedback control mechanisms where temperature sensors monitor the pyroelectric crystal temperature and adjust heating/cooling rates accordingly. This feedback system allows precise control of electron emission current by maintaining the crystal at optimal temperatures, making the compact device as controllable as conventional systems
Solution Approach 2:
The patent employs dynamic temperature adjustment where the heating and cooling rates of the pyroelectric crystal are continuously varied to control electron emission. By dynamically adjusting the thermal state of the crystal, precise control over electron current is achieved despite the compact design, transforming the static pyroelectric effect into a dynamically controllable source
3Power
If pyroelectric crystals operate at high temperatures, then electron emission is enhanced, but thermal stress causes crystal cracking
Solution Approach 1:
The patent uses periodic heating and cooling cycles rather than continuous high temperature operation. The pyroelectric crystal is heated to generate electron emission, then cooled to reduce thermal stress, creating a cyclic operation pattern. This periodic action maintains high electron emission intensity while preventing cumulative thermal stress that would cause crystal cracking
Solution Approach 2:
The patent incorporates thermal management structures that cushion against thermal stress before it can cause damage. By pre-cooling the crystal or using thermal expansion compensation structures, the system prepares the crystal to withstand temperature variations, preventing cracking while maintaining the high temperatures needed for electron emission
4Power
If conventional ionization sources are used, then ionization capability is achieved, but radioactive contamination and safety issues arise
Solution Approach 1:
The patent replaces long-lived radioactive sources with a non-radioactive pyroelectric electron beam source that can be turned on and off as needed. The electron beam source has no radioactive contamination risks and can be deactivated by simply stopping the heating/cooling cycles, eliminating safety issues while maintaining ionization capability through controlled electron emission
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 provides a compact, robust, and stable non-radioactive ionization source with controlled electron energy and current, suitable for API devices, offering improved reliability and longevity by minimizing thermal stress and gas permeation, and enabling continuous operation with multiple crystals.
Implementation Method 1
heating or cooling a pyroelectric crystal, which extracts high energy electrons through a thin window
Implementation Method 2
A heating and/or cooling element such as a Peltier element is useful for controlling the rate of cooling of the crystal
Implementation Method 3
The high voltage, which can be as much as several megavolts, accelerates electrons to high energy
Implementation Method 4
The tube is evacuated and the window prevents the gas external to the sealed tube from leaking into the tube
Data Source
AI summary
A non-radioactive source for Atmospheric Pressure Ionization is described. The electron-beam sealed tube uses a pyroelectric crystal(s). One end of the crystal is grounded while the other end has a metallic cap with sharp feature to generate an electron beam of a given energy. The rate of heating and/or cooling of the crystal is used to control the current generated from a tube. A heating and/or cooling element such as a Peltier element is useful for controlling the rate of cooling of the crystal. A thin window that is transparent to electrons but impervious to gases is needed in order to prolong the life of the tube and allow the extraction of the electrons. If needed, multiple crystals with independent heaters can be used to provide continuous operation of the device. Dielectric shielding of the pyroelectric crystal is used to minimize discharge of the crystal.