Ion Source Electron Path Length Extension
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Solution Overview
Problem
Current ion sources for neutron generators in well logging instruments are limited in generating a sufficient number of ions, which restricts the number of neutrons produced, and thus the information that can be collected about formations, especially under power-constrained conditions.
Innovation Solution
An ion source design featuring a cathode, cathode grid, reflector electrode, and extractor electrode with specific voltage differences to create an ionization region where electrons interact with an ionizable gas, increasing the path length and number of ions produced, and optionally utilizing secondary electrons generated from a reflector electrode to enhance ionization rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional ion source design is used, then the structure is simple and power consumption is low, but the number of ions generated is insufficient
Solution Approach 1:
The ion source is divided into multiple functional regions with distinct electrodes (cathode, cathode grid, reflector electrode, extractor electrode) that can be independently controlled. This segmentation allows each region to perform a specific function in the electron ionization process, increasing overall ion generation while maintaining manageable structural complexity
Solution Approach 2:
The patent introduces a longitudinal dimension to electron motion by implementing a reflector electrode that causes electrons to travel back through the ionization region. This transforms a single-pass linear trajectory into a multi-pass path, effectively increasing the interaction length between electrons and gas molecules without proportionally increasing the physical device size
2Productivity
If more power is supplied to generate more ions, then ion production increases, but power consumption becomes excessive for well logging applications
Solution Approach 1:
The reflector electrode creates a continuous circulation of electrons through the ionization region. Instead of electrons being consumed in a single pass, they are reflected back and continue ionizing gas molecules, maintaining continuous useful action. This increases ion production efficiency without requiring proportional increases in power input
Solution Approach 2:
The patent optimizes the voltage parameters of different electrodes (cathode-grid voltage difference, reflector electrode voltage, extractor electrode voltage) to create an efficient electron circulation pattern. By carefully controlling these voltage parameters, the system achieves high ion generation rates while maintaining power consumption within acceptable limits for well logging applications
3Speed
If electrons are accelerated quickly through the ionization region, then the extraction efficiency is high, but the ionization ratio decreases
Solution Approach 1:
The electron motion is transformed from a single continuous acceleration into a periodic pattern of acceleration and reflection. Electrons are accelerated toward the extractor, then reflected back by the reflector electrode, creating periodic passes through the ionization region. This periodic action allows sufficient interaction time for ionization while maintaining high extraction efficiency
Solution Approach 2:
The cathode grid is positioned to allow preliminary acceleration of electrons before they enter the main ionization region. This preliminary action gives electrons initial velocity and proper direction, ensuring they enter the ionization region with optimal conditions for both ionization and subsequent extraction, resolving the conflict between speed and ionization ratio
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 design increases the ionization ratio by up to five times, allowing for a higher number of ions to be generated, which translates to a greater number of neutrons produced, enhancing the information gathering capability of well logging instruments while maintaining efficient power usage.
Implementation Method 1
a cathode to emit electrons
Implementation Method 2
The cathode and the cathode grid may have a first voltage difference such that a resultant electric field in the ion source accelerates the electrons through the cathode grid and into the ionization region
Implementation Method 3
At least some of the electrons, when in the ionization region, may interact with an ionizable gas to create ions
Implementation Method 4
The reflector electrode may have a negative potential such that the electric field repels the electrons away from the reflector electrode and into the ionization region
Data Source
AI summary
An ion source includes a cathode to emit electrons, a cathode grid downstream of the cathode, a reflector electrode downstream of the cathode grid, reflector grid radially inward of the reflector electrode, and an extractor electrode downstream of the reflector electrode, the extractor electrode and cathode grid defining an ionization region therebetween. The cathode and the cathode grid have a first voltage difference such the electrons are accelerated through the cathode grid and into the ionization region on a trajectory toward the extractor electrode. The reflector grid and the extractor electrode have a second voltage difference less than the first voltage difference such that the electrons slow as they near the extractor electrode and are repelled on a trajectory toward the reflector electrode. The reflector electrode has a negative potential such that the electrons are repelled away from the reflector electrode and into the ionization region.