Scintillator Panel Needle Crystal Alignment via Dynamic Vapor Deposition
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Solution Overview
Problem
Existing scintillator panels with needle crystals formed by oblique vapor deposition lack alignment in a plane, leading to decreased modulation transfer function (MTF) and packing density due to crystal contact and increased voids, which reduces the efficiency of radiation conversion to light.
Innovation Solution
A method of depositing scintillator material on a substrate such that the material incidents obliquely with varying angles, aligning needle crystals in a plane by adjusting the amount of material deposited based on the angle between the projected incident direction and a reference direction, using a shutter or screens to control deposition, resulting in increased packing density and improved MTF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If oblique vapor deposition is performed with constant incident angle, then needle crystals are formed with voids between them, but the crystals are not aligned in a plane leading to decreased packing density and MTF
Solution Approach 1:
The incident angle of the vapor deposition is dynamically varied during the deposition process. The substrate is rotated to change the incident angle from a first angle to a second angle, allowing the deposition conditions to evolve and achieve both needle crystal formation and planar alignment simultaneously.
Solution Approach 2:
The substrate undergoes periodic rotation during vapor deposition, creating cyclic changes in the incident angle. This periodic action allows different regions of the substrate to receive deposition at varying angles, promoting uniform needle crystal alignment across the entire substrate surface.
2Reliability
If oblique vapor deposition is performed to form needle crystals, then light guidance is improved through total reflection, but crystal contact and voids reduce modulation transfer function
Solution Approach 1:
By dynamically adjusting the incident angle during deposition, the method optimizes the balance between forming sufficient voids for light guidance and maintaining crystal separation for high MTF. The varying angle prevents excessive crystal contact while ensuring adequate void formation.
Solution Approach 2:
The incident angle parameter is changed during the deposition process to optimize both light guidance and MTF. By transitioning from one angle to another, the method achieves optimal void size and distribution that enhances both total reflection and modulation transfer function.
3Reliability
If the distance between needle crystals is increased to reduce contact, then packing density decreases and conversion efficiency is reduced
Solution Approach 1:
Instead of increasing horizontal distance between crystals, the method utilizes angular variation in deposition to control crystal orientation and spacing. By changing the incident angle dimension, the method achieves proper crystal separation without sacrificing packing density in the vertical dimension.
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 alignment of needle crystals in a plane increases packing density and MTF, enhancing the conversion efficiency of radiation to light and sensitivity of the radiation detector without increasing the distance between crystals.
Implementation Method 1
a method for producing a scintillator panel by oblique vapor deposition
Implementation Method 2
the difference between the refractive index of cesium iodide (about 1.8) and the refractive index of air (1.0) causes the light generated in the cesium iodide needle crystals to repeat total reflection, thus guiding the light to the light-receiving element
Data Source
AI summary
A method is provided for manufacturing a scintillator panel including a substrate and a scintillator layer containing a plurality of crystals formed by depositing a scintillator material on a deposition surface of the substrate. The method includes depositing the scintillator material on the deposition surface of the substrate such that the scintillator material incidents on the deposition surface obliquely with respect to the normal to the deposition surface, and varying the angle between a reference direction on the deposition surface and a projected incident direction that is obtained by projecting the direction of the scintillator material incident onto the deposition surface. In the vapor deposition, the amount of the scintillator material deposited on the deposition surface changes according to the angle between the projected incident direction and the reference direction.