Ionization Chamber Radon-Thoron Separation Using Air Delay
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Solution Overview
Problem
Current radon and thoron measurement devices using ionization chambers struggle to accurately separate radon (Rn-222) and thoron (Rn-220) due to low energy resolution of ion signals, leading to confusion in indoor radon concentration measurements, as thoron is not effectively discriminated from radon.
Innovation Solution
The apparatus employs a metallic cylindrical ionization chamber with a main probe and an auxiliary probe, pre-amplifiers, and a differential amplifier to detect alpha particles, utilizing a DC bias voltage and an air inflow delay module to differentiate between radon and thoron based on their half-life differences, allowing for separate concentration measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an ionization chamber is used to detect alpha particles from radon and thoron, then the device cost is reduced and manufacturing is simplified, but the energy resolution is insufficient to separate radon and thoron signals
Solution Approach 1:
The measurement process is divided into two separate measurements: one for total alpha activity (radon + thoron) and another for thoron-only activity after delay. This segmentation allows the use of a simple ionization chamber while achieving separate radon and thoron concentration measurements through temporal separation rather than energy resolution.
Solution Approach 2:
The system performs a preliminary measurement of total alpha activity immediately, then introduces a time delay to allow thoron decay before performing a second measurement. This preliminary action captures the combined signal, and the subsequent delayed measurement captures primarily radon, enabling separation without requiring high energy resolution.
2Measurement precision
If semiconductor sensors or high-specification digital signal processing are used to separate radon and thoron, then measurement precision improves, but device cost and complexity increase
Solution Approach 1:
The patent replaces complex electronic signal processing methods (such as pulse shape discrimination or energy spectrum analysis requiring sophisticated electronics) with a simple temporal delay method. The separation is achieved through time-domain processing rather than complex frequency or energy domain analysis, significantly reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system changes the time parameter by introducing a controlled delay period between measurements. This parameter change exploits the different half-lives of radon and thoron to achieve separation. Instead of changing energy or frequency parameters requiring complex electronics, the simple time delay parameter achieves the same separation goal with minimal added complexity.
3Productivity
If immediate measurement is performed without delay, then measurement time is reduced, but thoron cannot be distinguished from radon
Solution Approach 1:
The system uses periodic measurement cycles: first measurement at time zero captures total activity, then after a predetermined delay period captures thoron-decayed activity. This periodic action with controlled intervals exploits the radioactive decay rates to achieve isotope discrimination while maintaining reasonable measurement speed through efficient cycling.
Solution Approach 2:
The system skips the intermediate time period where thoron is still present by introducing a deliberate delay before the second measurement. This rushing through the decay period allows the thoron signal to diminish sufficiently before measurement, enabling clear distinction from radon without requiring complex real-time separation during the transition period.
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 solution enables real-time, cost-effective separation of radon and thoron concentrations, improving measurement accuracy and reducing the need for expensive semiconductor sensors or high-specification digital signal processing, while maintaining high sensitivity and low noise levels.
Implementation Method 1
an ionization chamber having a metallic cylindrical box structure, having nozzles for receiving and discharging air, and generating an electrical field therein when bias power is applied to a surface
Implementation Method 2
Rn-222 with a half-life of 3.8 days and Rn-220 with a half-life of 56 seconds are the most stable. The other radon classified of radon has a half-life of 1 seconds or shorter
Data Source
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AI summary
An apparatus for measuring radon and thoron using an ionization chamber is proposed. The apparatus includes: a pump for air inflow suctioning and sending external air to at least one channel; a first sensor module outputting an alpha particle detection signal of an electrical signal by detecting alpha (α) particles discharged from radon and thoron; an air inflow delay module delaying air for a predetermined delay time and then outputting the air; a second sensor module outputting an alpha particle detection signal of an electrical signal by detecting alpha (α) particles discharged from radon and thoron; and a control module discriminating normal or abnormal alpha particle detection signals, counting the normal alpha particle detection signals discriminated for a predetermined measurement time, and calculating radioactive ray concentration values on the basis of the counted number of times of the normal alpha particle detection signals.