Scintillator Dose Measurement via Coincidence Counting
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Solution Overview
Problem
Current methods for determining the irradiation dose deposited in a material by ionizing radiation, such as ionization chambers and scintillator-based systems, face limitations including low precision for low doses, bulkiness, and the need for nonlinear correction curves, making them unsuitable for accurate and direct dose measurement, especially in confined spaces.
Innovation Solution
A method involving a scintillator irradiated by ionizing radiation, with a first photodetector detecting excitation events and a second photodetector in single photon counting mode detecting scintillation photons, counting coincidence events to calculate the dose using a predetermined proportionality factor, allowing for direct and precise dose determination independent of event number and detector noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ionization chamber is used to measure dose, then medium and high doses can be measured, but low doses cannot be measured accurately due to current measurement limitations
Solution Approach 1:
The patent replaces the ionization chamber's electrical current measurement system with a photodetection system that converts ionizing radiation directly into light signals via scintillation, which are then detected by photomultiplier tubes. This substitution enables detection of low doses by converting extremely small electrical currents into measurable optical signals, overcoming the fundamental limitation of current measurement at low dose levels.
Solution Approach 2:
The patent changes the measurement parameter from electrical current (in ionization chambers) to light intensity (in scintillation detectors). By measuring the intensity of scintillation light rather than electrical current, the system achieves superior sensitivity for low dose measurements, as photomultiplier tubes can detect extremely faint light signals that correspond to very low radiation doses.
2Measurement precision
If correction factors are applied to ionization chamber measurements to account for density differences, then dose in material can be estimated, but measurement precision is reduced
Solution Approach 1:
The patent uses a scintillator material that is homogeneous with the material being measured, eliminating the need for density correction factors. The scintillator replaces the gas-filled ionization chamber, and since the scintillator has similar physical properties to solid materials, the light output directly corresponds to the dose deposited in the material without requiring corrections for density differences between the detector medium and the target material.
3Measurement precision
If a scintillator with photomultiplier tube is used, then low doses can be detected, but nonlinear correction curves are required reducing direct determination capability
Solution Approach 1:
The patent replaces the conventional single photomultiplier tube system with a coincidence detection system using two photodetectors. This substitution transforms the nonlinear single-channel detection into a linear two-channel coincidence counting system, where the number of coincidence events is directly proportional to the radiation dose, eliminating the need for nonlinear correction curves while maintaining low dose detection capability.
4Measurement precision
If conventional scintillation detection is used, then dose can be determined, but the method requires an abacus for nonlinear correspondence between dose and detected scintillation
Solution Approach 1:
The patent replaces the conventional single photodetector system with a coincidence detection system using two photodetectors. This substitution creates a linear relationship between the number of coincidence events and the radiation dose, allowing direct determination of dose from the coincidence count rate without requiring an abacus or nonlinear correction curves, thereby significantly improving ease of operation.
5Measurement precision
If ionization chambers are used for dose measurement, then dose can be measured, but the equipment is bulky preventing use in confined spaces
Solution Approach 1:
The patent extracts the scintillation detection function from the bulky ionization chamber structure. By using a scintillator material that can be made in very small dimensions while maintaining detection capability, the system achieves dose measurement in a compact form factor suitable for confined spaces, eliminating the need for large ionization chamber enclosures.
Solution Approach 2:
The patent changes the detection mechanism from electrical current measurement in a large gas-filled chamber to optical signal detection in a small scintillator crystal. This parameter change enables the detector to be miniaturized while maintaining or improving measurement precision, as the scintillation process occurs in a much smaller volume than the ionization process in gas.
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 approach enables precise measurement of low irradiation doses with high sensitivity and compactness, suitable for confined spaces, eliminating the need for bulky equipment and nonlinear correction factors, thereby improving measurement accuracy and usability.
Implementation Method 1
Under the effect of the incident ionizing radiation, the scintillator is excited and emits light. This light results from two contributions: i) direct excitation of the scintillator, without ionization, leading to so-called prompt light emission; ii) the ionization of the scintillator and the production of pairs of charge carriers
Implementation Method 2
the ionization of the scintillator and the production of pairs of charge carriers, according to a process similar to that induced in a conventional ionization chamber
Implementation Method 3
The total light emitted by the scintillator is received by the photomultiplier tube, which converts it into an electrical signal
Data Source
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AI summary
The invention relates to a method for determining an irradiation dose deposited in a scintillator (5) by ionising radiation, said method comprising the steps of: irradiating the scintillator (5) for a pre-determined time; detecting an instant at which the scintillator (5) is excited, using a first photodetector (11); subsequently, detecting an instant at which a scintillation photon is received, using a second photodetector (14) operating in single photon counting mode; identifying each sequence formed by the detection of an excitation instant by the first photodetector (11) and the detection of a reception instant by the second photodetector (14) at a coincidence event; counting the number of coincidence events; and obtaining the irradiation dose deposited during the irradiation time as a function of the number of coincidence events counted and a pre-determined proportionality factor.