Photomultiplier Dynode Ring Structure for Electron Collection
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Solution Overview
Problem
The venetian blind dynode structure in photomultipliers used for well-logging tools inefficiently collects secondary electrons produced by the first dynode, leading to reduced amplification efficiency due to poor collection by subsequent dynodes, despite its resistance to vibration and heat.
Innovation Solution
A photomultiplier design featuring a plurality of dynodes with a conductive outer and inner ring structure, where insulators are positioned between adjacent pairs, enhancing the collection of secondary electrons by creating a low electric field region upstream and a high electric field region downstream of each dynode, improving electron trajectory and amplification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a venetian blind dynode structure is used, then the photomultiplier resists vibration and heat better, but the collection of secondary electrons by subsequent dynodes becomes poor
Solution Approach 1:
The patent applies local quality by creating different electric field conditions in different spatial regions. Specifically, a first electric field configuration is established upstream of the dynode to facilitate secondary electron emission, while a second electric field configuration is established downstream to improve secondary electron collection. This localized field differentiation allows the venetian blind structure to maintain its mechanical robustness while overcoming its electron collection inefficiency
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of controlled electric fields between the venetian blind dynode structure and the secondary electrons. These electric fields act as intermediaries that guide and accelerate secondary electrons from the dynode surface toward subsequent collecting dynodes, bridging the gap between the robust but inefficient venetian blind structure and the need for effective electron multiplication
2Productivity
If the first dynode intercepts about 80% of incident electrons, then electron collection is high, but many intercepted electrons produce secondary electrons that are poorly collected by subsequent dynodes
Solution Approach 1:
The patent applies preliminary action by pre-configuring the electric field downstream of the first dynode before secondary electrons are emitted. This pre-established electric field is oriented and strength-adjusted to immediately capture and guide secondary electrons toward subsequent dynodes as they are produced, preventing their loss before they can be collected and multiplied
Solution Approach 2:
The patent changes the electric field parameters (strength, direction, distribution) in different regions around the dynode structure. By adjusting these field parameters, the system optimizes both the initial interception of incident electrons by the first dynode and the subsequent collection of emitted secondary electrons, transforming the electric field from a uniform configuration to a spatially differentiated configuration that addresses both collection stages
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 enhances the amplification efficiency of the photomultiplier, providing excellent single photoelectron resolution and high detection efficiency, particularly in well-logging environments, by efficiently utilizing secondary electrons of various energies and maintaining structural ruggedness.
Implementation Method 1
The at least one first dynode includes a conductive outer ring and a medial conductive member coupled to the conductive outer ring in spaced relation. The at least one second dynode includes a conductive outer ring and a conductive inner ring supported within the conductive outer ring.
Implementation Method 2
A photomultiplier is often optically coupled to a scintillator and incorporated into a well-logging tool to measure radiation within the wellbore. A scintillator crystal emits visible or near-visible light in response to the detected radiation. The photomultiplier receives the light from the scintillator crystal and transforms that light into electrical pulses.
Data Source
AI summary
A photomultiplier includes a tube and plurality of dynodes within the tube and including at least one first dynode and at least one second dynode. A respective insulator is between adjacent pairs of dynodes. The at least one first dynode includes a conductive outer ring and a medial conductive member coupled to the conductive outer ring in spaced relation therefrom. The at least one second dynode includes a conductive outer ring and a conductive inner ring supported within the conductive outer ring.