Negative Ion Source With Segmented Plasma And Converter Chambers
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Solution Overview
Problem
Existing negative ion sources suffer from short lifetimes, high power requirements, and high gas loads, limiting their reliability and efficiency in applications such as semiconductor production and fusion energy, where high current and long-term operation are essential.
Innovation Solution
A negative ion source system comprising a plasma chamber, a microwave source, a magnetic filter, and a beam formation mechanism, which ionizes gas into hyperthermal neutral atoms and converts them to negative ions using a cesiated converter, with the magnetic filter reducing electron temperature to enhance ion production and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional negative ion sources are operated at full power to achieve high current output, then beam current increases, but lifetime decreases significantly
Solution Approach 1:
The ion source is divided into two separate chambers: a plasma chamber for generating ions and a converter chamber for negative ion production. This segmentation allows the plasma chamber to operate at high power continuously while the converter chamber components can be replaced without replacing the entire source, thereby extending operational lifetime while maintaining high beam current capability.
Solution Approach 2:
The converter components (converter surface and extractor) are extracted as separate replaceable modules from the main plasma source. This allows these consumable parts to be replaced independently after a certain lifetime, enabling the main plasma generation system to continue operating without interruption, thus resolving the contradiction between high current operation and source lifetime.
2Productivity
If conventional negative ion sources are designed for high current output, then beam current increases, but power requirements increase to 15 kW
Solution Approach 1:
A cesiated converter surface is introduced as an intermediary between the plasma source and the extraction region. This converter efficiently converts positive ions to negative ions with high conversion efficiency, reducing the power required in the plasma chamber to achieve the same negative ion beam current, thereby lowering overall power requirements while maintaining high productivity.
3Productivity
If conventional negative ion sources operate at high current, then beam current increases, but gas load on downstream vacuum components increases to 18-20 sccm
Solution Approach 1:
By segmenting the source into plasma and converter chambers with separate pumping systems, the gas load is localized to the plasma chamber where it is needed for ion generation. The converter chamber operates at lower gas flow rates, reducing the total gas load on downstream vacuum components while maintaining high beam current output.
4Duration of action of stationary object
If conventional negative ion sources are designed for long lifetime, then component durability increases, but current output is limited to low currents
Solution Approach 1:
The high-stress components (converter surface and extractor) are extracted as separate replaceable modules, allowing them to be replaced after limited use. This enables the main plasma generation system to be designed for long-term continuous operation, achieving both long lifetime for the main system and high current output capability through the replaceable high-performance converter modules.
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 system achieves a high current output of up to 10 mA with a long lifetime exceeding one month, significantly improving reliability and reducing power and gas loads, thus addressing the limitations of conventional negative ion sources.
Implementation Method 1
The microwave source transmits microwaves to the plasma chamber to ionize the gas into atomic species including hyperthermal neutral atoms
Implementation Method 2
The microwave source transmits microwaves to the plasma chamber to ionize the gas into atomic species
Implementation Method 3
The magnetic filter reduces the temperature of electrons between the plasma chamber and the negative ion source converter
Implementation Method 4
converting the hyperthermal neutral atoms to negative ions via interaction with a cesiated conversion cone
Data Source
AI summary
A negative ion source includes a plasma chamber, a microwave source, a negative ion converter, a magnetic filter and a beam formation mechanism. The plasma chamber contains gas to be ionized. The microwave source transmits microwaves to the plasma chamber to ionize the gas into atomic species including hyperthermal neutral atoms. The negative ion converter converts the hyperthermal neutral atoms to negative ions. The magnetic filter reduces a temperature of an electron density provided between the plasma chamber and the negative ion converter. The beam formation mechanism extract the negative ions.