Photomultiplier Tube Dynode Support Structure
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Solution Overview
Problem
Conventional photomultiplier tubes experience a decrease in withstand voltage when downsized due to close proximity of structures with different potentials on an insulating substrate, leading to electrical charging and reduced physical strength of dynodes, causing deformation or breakage.
Innovation Solution
A photomultiplier tube design featuring a housing with opposing insulating substrates, an electron multiplying part with staged dynodes, a photocathode, and an anode, where supporting bases with varying cross-sectional areas are used to maintain electrical separation and enhance physical strength, preventing voltage drops and structural damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the photomultiplier tube is downsized by arranging structures in close proximity on an insulating substrate, then the device size is reduced and compactness is improved, but the withstand voltage between structures decreases due to electrical charging of the insulating substrate and reduced physical strength of dynodes
Solution Approach 1:
The supporting base extends in the thickness direction (third dimension) of the insulating substrate, with its projection area in the planar direction being smaller than the insulating substrate's area. This vertical extension creates electrical separation between adjacent dynodes by utilizing the thickness dimension, thereby maintaining withstand voltage while allowing close horizontal spacing for compactness.
Solution Approach 2:
The supporting base acts as an intermediary structure between the insulating substrate and adjacent dynodes. By extending vertically from the substrate and positioning between dynodes, it serves as an electrical barrier that prevents charge accumulation on the substrate surface, thus maintaining insulation performance in the downsized configuration.
2Volume of moving object
If the photomultiplier tube is downsized, then compactness is improved, but the physical strength of dynodes decreases making them susceptible to deformation or breakage during power supply connection
Solution Approach 1:
The supporting base utilizes the thickness direction of the insulating substrate to provide structural reinforcement. By extending vertically and making contact with the substrate over an extended area in the thickness direction, it creates a robust support structure that strengthens the dynode assembly without increasing the planar footprint of the device.
3Area of stationary object
If structures with different potentials are arranged in close proximity on an insulating substrate, then device compactness is improved, but electrical charging of the insulating substrate occurs decreasing withstand voltage between adjacent dynodes
Solution Approach 1:
The supporting base serves as an intermediary electrical barrier between adjacent dynodes and the insulating substrate. Its vertical extension and positioning between dynodes prevent electron accumulation on the substrate surface, eliminating the harmful electrical charging effect while maintaining close horizontal spacing for compact design.
Solution Approach 2:
By utilizing the thickness direction to extend the supporting base vertically, the design creates electrical separation in the third dimension. This prevents charge accumulation on the insulating substrate surface that would otherwise occur due to close horizontal spacing of high-voltage structures.
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 design effectively suppresses voltage drops and maintains physical strength, preventing deformation and breakage of dynodes, even when the photomultiplier tube is downsized, while also increasing the internal volume and reducing the likelihood of defective joining and electrical charging.
Implementation Method 1
a photocathode which is installed on the first end side inside the housing so as to be spaced away from the electron multiplying part, thereby converting incident light from outside to photoelectrons
Data Source
Figure 1
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AI summary
The photomultiplier tube 1 is provided with a casing 5 made of an upper frame 2 and a lower frame 4, an electron multiplying part 33 having dynodes 33a to 331 arrayed on the lower frame 4, a photocathode 41, and an anode part 34. Conductive layers 202 are installed on an opposing surface 20a of the upper frame 2. The electron multiplying part 33 is provided with base parts 52a to 52d of the respective dynodes 33a to 33d installed on the side of the lower frame 4, and power supplying parts 53a to 53d connected to the conductive layers 202 at one end parts of the respective base parts 52a to 52d in a direction along the opposing surface 40a. The base parts 52a to 52d are constituted in such a manner that the both end parts are joined to the opposing surface 40a, the central part is spaced away from the opposing surface 40a, and a cross sectional area at the one end part on the side of each of the power supplying parts 53a to 53d is made greater than a cross sectional area at another end part.