Cylindrical Neutron Generator Nanotip Array
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Solution Overview
Problem
Conventional neutron generators for well logging face limitations due to a small target surface area, leading to increased titanium layer thickness, thermal stress, and reduced neutron yield, as well as desorption of deuterium and tritium atoms, which limits the duty cycle and overall efficiency.
Innovation Solution
A cylindrical field ionization nanotip array is used, providing a larger target surface area and allowing for a thinner titanium layer, reducing thermal stress and increasing neutron emission, while maintaining high voltage pulses to generate predominantly monatomic deuterium and tritium ions for efficient neutron production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional target design with limited surface area is used, then the device structure remains simple, but the neutron yield is reduced and thermal stress increases
Solution Approach 1:
The patent transitions from a conventional planar target surface to a three-dimensional cylindrical target structure. The cylindrical geometry provides a substantially larger surface area for ion bombardment, allowing increased neutron production capacity without proportionally increasing device volume. This dimensional change enables the target to handle higher ion currents while distributing thermal load across a larger surface area.
Solution Approach 2:
The cylindrical target is divided into multiple discrete target elements or segments arranged along the cylinder surface. This segmentation allows the total ion current to be distributed across multiple independent bombardment zones, reducing the thermal stress on any single point while maintaining high overall neutron yield. Each segment can be independently optimized for specific operational parameters.
2Strength
If the titanium layer thickness is increased to handle thermal stress, then thermal stress resistance improves, but neutron yield decreases
Solution Approach 1:
The cylindrical target structure serves multiple functions simultaneously: it provides thermal management through its geometry, supports the titanium layer, and enables high neutron yield through increased surface area. The cylindrical shape inherently distributes thermal stress while maintaining structural integrity, eliminating the need to choose between thick protective layers and thin high-yield layers.
Solution Approach 2:
The patent changes the geometric parameters of the target from a flat or simple cylindrical rod to an optimized cylindrical structure with specific dimensions and surface characteristics. By adjusting the cylinder diameter, length, and surface area-to-volume ratio, the target achieves optimal thermal stress distribution while maintaining thin titanium layer thickness for high neutron yield. The geometric parameters are tuned to balance thermal management and neutron production efficiency.
3Productivity
If high voltage pulses are applied to generate monatomic ions, then neutron production efficiency increases, but thermal desorption of deuterium and tritium increases
Solution Approach 1:
The target is pre-loaded with deuterium and tritium atoms into the titanium layer before operation. This preliminary loading ensures that the fuel atoms are already in position and can be immediately utilized when ion bombardment begins, reducing the need for continuous high-voltage pulsing that would cause thermal desorption. The pre-loaded fuel reservoir provides a sustained supply for efficient neutron production.
Solution Approach 2:
The system uses periodic pulsed voltage application rather than continuous high voltage. The pulses are timed and duration-controlled to generate monatomic ions for neutron production while allowing thermal relaxation between pulses. This periodic action prevents excessive heat buildup that would cause deuterium and tritium desorption, while still maintaining high neutron production efficiency during the active pulse periods.
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 significantly increases the neutron yield by enhancing the target surface area and reducing thermal desorption, enabling a longer duty cycle and more efficient neutron generation with reduced thermal stress, thus improving the performance of neutron generators for well logging applications.
Implementation Method 1
A cylindrical field ionization nanotip array is used, providing a larger target surface area and allowing for a thinner titanium layer, reducing thermal stress and increasing neutron emission, while maintaining high voltage pulses to generate predominantly monatomic deuterium and tritium ions for efficient neutron production
Data Source
AI summary
A neutron generator comprises a cylindrical housing having a target rod concentrically located along a central axis of the cylindrical housing. An array of field ionization nanotips is positioned around an inner surface of the housing, where the array of nanotips extends toward the central axis. A method for logging a formation comprises deploying a logging tool having a neutron generator into a borehole. An array of nanotips is located around an inner cylindrical surface of a cylindrical housing in the neutron generator are energized. An ionizable gas proximate the array of nanotips is ionized. The ions are accelerated radially inward to bombard a titanium layer on an outer diameter of a target rod concentrically located along a central axis of the cylindrical housing to generate neutrons.