Field Emitter Array Neutron Generator for Well Logging
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Solution Overview
Problem
Conventional neutron generators for well logging face challenges in efficiently producing high-energy neutrons for subsurface formation evaluation due to high voltage requirements and complexity, which can lead to reliability and robustness issues.
Innovation Solution
A neutron generator incorporating a field emitter array with nano-emitters, such as silicon nanotips, that produces energetic electrons for ionization of deuterium and tritium gas, reducing the need for high anode voltages and eliminating the requirement for permanent magnets, enabling a compact and reliable ion source for fusion reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ion sources use high voltage arc discharge to produce ion beams, then neutron production efficiency is improved, but device complexity and reliability deteriorate due to high voltage requirements and permanent magnet components
Solution Approach 1:
The patent replaces the conventional arc discharge ionization mechanism with a field emitter array that uses quantum tunneling electron emission. This substitution eliminates the need for high voltage arc discharge circuits and permanent magnets, significantly reducing device complexity while maintaining ion production capability for neutron generation
Solution Approach 2:
The patent changes the operating voltage parameter from high voltage (kilovolt range for arc discharge) to low voltage (hundreds of volts for field emission). This parameter change enables the use of solid-state field emitter arrays instead of complex high voltage arc discharge systems, reducing both device complexity and improving reliability
2Use of energy by moving object
If conventional ion sources use high anode voltages to accelerate ions, then ion beam energy is improved, but electrical stress and reliability worsen
Solution Approach 1:
The patent employs pulsed operation of the field emitter array, where voltage is applied in periodic pulses rather than continuously. This allows ion beam energy to be maintained during the pulse while reducing average electrical stress on components, thereby improving reliability without sacrificing ion beam energy when needed for neutron production
Solution Approach 2:
The patent introduces a field emitter array as an intermediary device between the power supply and the ionizable gas. This intermediary converts electrical energy to electron kinetic energy through quantum tunneling, which then ionizes the gas through electron impact. This intermediary mechanism achieves ion beam energy with lower electrical stress compared to direct high voltage arc discharge
3Manufacturing precision
If permanent magnets are used in conventional ion sources, then ion beam focusing is improved, but robustness and ease of operation worsen due to fragility and complexity
Solution Approach 1:
The patent replaces permanent magnet-based magnetic focusing systems with electric field-based focusing using electrostatic lenses and field emitter geometry. This substitution eliminates fragile permanent magnets and complex magnetic shielding, making the system more robust and easier to operate while maintaining ion beam focusing capability through electric field control
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 solution allows for sub-microsecond ignition with lower anode voltages, reducing electrical stress and improving the robustness and reliability of the neutron generator, while maintaining efficient neutron production for effective subsurface formation evaluation.
Implementation Method 1
a field emitter array configured to deliver charged particles to the ion source chamber for causing production of ions by electron impact ionization of the gas
Implementation Method 2
produces energetic electrons for ionization of deuterium and tritium gas
Implementation Method 3
neutron generator incorporating a field emitter array with nano-emitters, such as silicon nanotips, that produces energetic electrons for ionization of deuterium and tritium gas, reducing the need for high anode voltages and eliminating the requirement for permanent magnets, enabling a compact and reliable ion source for fusion reactions
Data Source
AI summary
A well logging tool includes a neutron generator having an ion source cathode comprising a nano-structure field emission (FE) array for producing a charged particle current routed through an ionizable gas, thus generating ions by electron impact ionization of the gas. The nanostructures can be provided by bundles of silicon nanotips grown on a substrate. The FE array can be provided on an axially facing substrate located co-axially in an elongate housing, with the charged particle current directed from the centrally located FE array to a co-axial annular anode and having axial and radial directional components.