Photomultiplier Accelerating Electrode and Dynode Unit Configuration
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Solution Overview
Problem
Conventional photomultipliers experience variations in transit time due to a metal disk placed between the accelerating electrode and the first-stage dynode, leading to increased Cathode Transit Time Difference (CTTD) and Transit Time Spread (TTS), which affects the uniformity and performance of the device.
Innovation Solution
A photomultiplier design where the accelerating electrode and dynode unit are directly opposite without a conductive member, eliminating the need for a metal disk at the same potential as the first-stage dynode, and using insulating support members with protruding portions and slit grooves for precise assembly and alignment, ensuring uniform electron transit times across the cathode surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a metal disk is placed between the accelerating electrode and the first-stage dynode to support the dynode, then the assembly structure is stabilized, but the transit time of electrons varies significantly depending on the emission area of photoelectrons, increasing CTTD and TTS
Solution Approach 1:
The patent removes the metal disk component from the structure between the accelerating electrode and the first-stage dynode. By extracting this conductive element that caused potential interference and transit time variations, the design achieves more uniform electron transit times across different emission areas while maintaining structural stability through alternative support mechanisms.
Solution Approach 2:
The patent introduces an insulating support structure as an intermediary element to hold the first-stage dynode in position without using a conductive metal disk. This insulating mediator eliminates the harmful electrical influence on electron transit while providing the necessary mechanical support, thereby reducing CTTD and TTS variations.
2Speed
If a focusing electrode and accelerating electrode are arranged between the cathode and the first-stage dynode to correct photoelectron orbits and reduce transit time variations, then high-speed response is achieved, but the device complexity increases
Solution Approach 1:
The patent combines the focusing and accelerating functions into an integrated electrode arrangement where the focusing electrode and accelerating electrode work together as a unified system. By merging these functions and optimizing their spatial configuration, the design achieves high-speed response while reducing the overall complexity compared to separate, independent electrode systems.
Solution Approach 2:
The electrode structure in the patent is designed to perform multiple functions simultaneously - the focusing electrode not only corrects photoelectron orbits but also works in conjunction with the accelerating electrode to control electron transit. This multi-functional design reduces the need for additional specialized components, thereby achieving high-speed response with reduced device complexity.
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 reduces electron transit time variations, achieving CTTD of 500 psec or less and TTS of 300 psec or less, enhancing the photomultiplier's uniformity and performance while simplifying the assembly process and reducing variations in produced units.
Implementation Method 1
The cathode emits photoelectrons as a primary electron within the sealed container in response to incidence of light having a predetermined wavelength
Implementation Method 2
The dynode unit includes a plurality of stages of dynodes emitting secondary electrons in response to the photoelectrons reached from the photocathode to cascade-multiply sequentially the photoelectrons
Implementation Method 3
The focusing electrode functions to correct the orbit of each photoelectron emitted from the photocathode
Implementation Method 4
The accelerating electrode functions to accelerate the photoelectrons reached from the photocathode via the focusing electrode
Data Source
AI summary
The present invention relates to a photomultiplier having a structure that enables to perform high gain and satisfy higher required characteristics. In the photomultiplier, an electron-multiplying unit accommodated in a sealed container comprises a focusing electrode, an accelerating electrode, a dynode unit, and an anode. Particularly, at least the accelerating electrode and dynode unit are held unitedly in a state that at least a first-stage dynode and a second-stage included in the dynode unit are opposite directly to the accelerating electrode not through a conductive material. A conventional metal disk for supporting directly dynodes which are set to the same potential as that of the first-stage dynode is not placed between the accelerating electrode and dynode unit; thus, variations of the transit time of electrons may be drastically reduced while the electrons reach from the cathode to the second-stage dynode via the first-stage dynode.