3D p-n Junction Microdosimeter Array for Energy Deposition Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current microdosimetry methods, such as tissue-equivalent proportional counters and solid-state detectors, face limitations in accurately measuring energy deposition in small volumes due to size constraints, noise issues, and inability to distinguish energy deposited by single events, leading to inaccuracies in predicting radiobiological effects and dose equivalents in radiation fields.
Innovation Solution
A microdosimeter comprising an array of three-dimensional p-n junction semiconductor detectors embedded in a tissue-equivalent medium, such as polymethylmethacrylate, with core and outer electrodes, allowing for accurate charge collection and reduced noise, enabling precise measurement of energy deposition and dose equivalents by detecting secondary charged particles generated in the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tissue-equivalent proportional counters are used for microdosimetry measurements, then energy deposition in small volumes can be measured, but the device size becomes large (1 to 2 cm in diameter) which limits spatial resolution
Solution Approach 1:
The detector is divided into multiple pixels (e.g., 32x32 array) on a silicon wafer, with each pixel acting as an independent sensitive volume. This segmentation allows the large measurement capability to be distributed across many small elements, achieving both accurate energy deposition measurement and high spatial resolution simultaneously.
Solution Approach 2:
The invention transitions from three-dimensional gas-filled proportional counters to two-dimensional planar silicon detector arrays. This dimensional change enables compact packaging while maintaining multiple independent measurement volumes, resolving the contradiction between measurement precision and device size.
2Volume of moving object
If solid state detectors with small sensitive volumes are used, then spatial resolution is improved, but noise increases and the ability to distinguish single event energy deposition is lost
Solution Approach 1:
By segmenting the silicon wafer into multiple pixels, each pixel maintains a small sensitive volume for good spatial resolution while the array as a whole provides sufficient signal accumulation. The segmentation allows independent readout of each pixel, preserving single event detection capability without excessive noise.
Solution Approach 2:
Multiple small pixel signals are combined through readout electronics to achieve the signal levels needed for reliable single event detection. The merging of signals from multiple pixels maintains sensitivity while the individual pixel small size preserves spatial resolution.
3Ease of manufacture
If planar p-n junction detectors are used, then manufacturing is simplified, but charge collection is incomplete due to lateral diffusion
Solution Approach 1:
The detector structure is optimized locally at each pixel with specific doping profiles and electrode configurations that confine charge collection to the intended sensitive volume. This local optimization maintains manufacturing simplicity while eliminating lateral diffusion losses through careful design of the p-n junction geometry and electric field distribution.
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 solution enables 100% charge collection and accurate determination of deposited energy event-by-event, reducing errors in dose equivalent measurements and improving spatial resolution, allowing for the measurement of low LET radiation and providing more accurate radiobiological characterization of radiation fields.
Implementation Method 1
a tissue equivalent medium for generating secondary charged particles
Implementation Method 2
the detectors are located to detect secondary charged particles generated in the tissue equivalent medium
Implementation Method 3
allowing for accurate charge collection and reduced noise, enabling precise measurement of energy deposition
Data Source
Figure 1~2
Figure 3A~3C
Figure 4~6
AI summary
A microdosimeter, comprising an array of three-dimensional p-n junction semiconductor detectors, each providing a sensitive volume-target and a tissue equivalent medium for generating secondary charged particles. The array is manufactured from a semiconductor on insulator wafer and the detectors are located to detect secondary charged particles generated in the tissue equivalent medium.