Cold-Cathode Ion Source Element With Sub-Mean Free Path Spacing
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Solution Overview
Problem
Conventional ion source elements with carbon nanotube films are unstable due to electron bombardment, leading to local destruction and transformation of the CNT film, resulting in a short operational lifespan.
Innovation Solution
The ion source element features a cold cathode, grid electrode, and ion accelerator arranged in a specific configuration with a reduced space between the cold cathode and grid electrode, less than the mean free path of electrons, minimizing electron and gas ion interactions, and using a field emission film composed of carbon nanotubes, low-melting-point glass, and conductive particles to enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the space between the cold cathode and grid electrode is reduced to less than the mean free path of electrons, then the ionization probability of gas molecules is reduced and stability is improved, but the device complexity increases due to precise spacing requirements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the spacing parameter between the cold cathode and grid electrode to be less than the mean free path of electrons at the operating pressure. This specific parameter adjustment reduces the ionization probability of gas molecules, thereby improving the stability and operational lifespan of the ion source element without requiring fundamental design changes.
2Use of energy by moving object
If a conventional cold cathode with CNT film is used, then the power consumption is low and evaporation rate is low, but the CNT film is locally destroyed and transformed due to electron and gas ion bombardment, reducing operational lifespan
Solution Approach 1:
The patent converts the harmful effect of electron and gas ion bombardment into a beneficial outcome by reducing the spacing between the cold cathode and grid electrode. This configuration limits the travel distance of electrons, reducing their interaction with gas molecules and subsequent bombardment of the CNT film. The harmful bombardment process is thus converted into a controlled interaction that preserves the CNT film integrity while maintaining low power consumption.
Solution Approach 2:
The patent changes the critical parameter of electrode spacing to be less than the mean free path of electrons. This parameter change fundamentally alters the interaction dynamics between electrons, gas molecules, and the CNT film, reducing ionization events and protecting the cathode material from destruction, thereby extending operational lifespan while maintaining low power consumption characteristics.
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 configuration significantly reduces the ionization probability of gas molecules, increasing the stability of the ion source element and extending its operational period, making it suitable for various applications such as mass spectrographs and vacuum gauges.
Implementation Method 1
The CNT film acts as an electron emitter for the ion source element
Implementation Method 2
In their travel, electrons bombard with the gas molecules and/or atoms and, thereby, create gas ions
Implementation Method 3
an ion accelerator arranged above the grid electrode
Data Source
AI summary
An ion source element includes a cold cathode, a grid electrode, and an ion accelerator. The cold cathode, the grid electrode, and the ion accelerator are arranged in that order and are electrically separated from one another. A space between the cold cathode and the grid electrode is essentially smaller than a mean free path of electrons at an operating pressure. The ion source element is thus stable and suitable for various applications.