Presentation Information
[O12-P97]Evaluation of Detected Energy Based on Radiation Detector Performance
*Takuto Takahashi1,2 (1. Fukushima Prefectural Fukushima High School, 2. Accel Kitchen)
Keywords:
Radiation,Scintillator
1. Background and Objective
Current radioactivity analysis typically requires sample collection and measurement using large-scale equipment. I hypothesized whether these processes could be performed directly on-site and investigated whether the "Cosmic Watch" detector possesses sufficient energy resolution to identify radionuclides. The primary objective was to determine the optimal parameters for evaluating energy levels to enable portable, real-time analysis.
2. Detection Mechanism
This study utilized the "Cosmic Watch," a detector employing a scintillator that emits light upon radiation incidence. This light is converted into electrical signals by a Silicon Photomultiplier (SiPM) and amplified via a non-inverting circuit. An Arduino then digitizes these signals into ADC values (0–1024), which serve as an index for the pulse height's relative intensity. To address semiconductor dark current noise—a challenge identified in previous research (Kumagai et al., 2021)—I implemented a methodology to differentiate noise from radiation by optimizing the amplification gain.
3. Experiment ①: Analysis of Cosmic Ray Detection via Amplification Gain Variation
The objective was to verify how changes in the circuit's amplification gain affect the distribution of energy peaks and the degree of noise interference. Using a CsI scintillator, I conducted measurements across five gain levels: 1.5, 1.8, 2.0, 3.0, and 4.0. To ensure a standardized comparison, all detection counts were normalized to hourly rates. The results indicated that clear energy peaks were visible at gains of 1.5, 1.8, and 2.0; however, at gains of 3.0 and 4.0, the peaks became indistinguishable as noise signals were simultaneously amplified. This suggests that while higher gain increases sensitivity, it also elevates the noise floor to a point where cosmic ray signals, which have a naturally broad distribution and low pulse height, merge with the noise, making definitive peak identification difficult.
4. Experiment ②: Detection of Specific Energy Peaks Using Radioactive Soil
Based on the results of Experiment ①, the amplification gain was fixed at 2.0 to balance sensitivity and noise suppression. The objective was to verify if specific energy peaks from radioactive cesium could be detected in soil samples. I performed measurements on contaminated soil and applied a background subtraction process during analysis to isolate the sample's inherent radiation. The results showed a significant increase in total counts compared to the background, particularly within the ADC range of 500 to 1024. Although the detector successfully captured radiation from the soil, the resulting energy distribution was too wide to confirm unique photopeaks required for radionuclide identification. This may be attributed to interference from other isotopes within the soil or the performance limitations of the portable hardware, suggesting that more refined experimental conditions are necessary for precise analysis.
5. Summary and Future Outlook
This study confirmed that varying the amplification gain significantly shifts the distribution and visibility of signal peaks. While the successful detection of radiation from soil was achieved at a gain of 2.0, the current energy resolution remains a barrier to definitive identification. Future research will focus on implementing advanced peak detection algorithms and improving environmental noise isolation to isolate specific radionuclides effectively.
References:
Kumagai, K. et al., "Partial Correlation between Ground-level Muon Detection Frequency and Surface Temperature, Humidity, and Atmospheric Pressure by Weather in Akita Prefecture," Journal of Science EGGS, 4, 2110004 (2021).
Acknowledgments:
I would like to express my gratitude to Dr. Katsuo Tanaka, Senior Researcher at Waseda University and CEO of Accel Kitchen LLC, as well as Mr. Ryuta Saito of Tohoku University and Accel Kitchen LLC, and other mentors for their cooperation in this research. I also wish to thank Mr. Keiichiro Kikuchi of Fukushima Prefectural Fukushima High School for his guidance and advice.
Current radioactivity analysis typically requires sample collection and measurement using large-scale equipment. I hypothesized whether these processes could be performed directly on-site and investigated whether the "Cosmic Watch" detector possesses sufficient energy resolution to identify radionuclides. The primary objective was to determine the optimal parameters for evaluating energy levels to enable portable, real-time analysis.
2. Detection Mechanism
This study utilized the "Cosmic Watch," a detector employing a scintillator that emits light upon radiation incidence. This light is converted into electrical signals by a Silicon Photomultiplier (SiPM) and amplified via a non-inverting circuit. An Arduino then digitizes these signals into ADC values (0–1024), which serve as an index for the pulse height's relative intensity. To address semiconductor dark current noise—a challenge identified in previous research (Kumagai et al., 2021)—I implemented a methodology to differentiate noise from radiation by optimizing the amplification gain.
3. Experiment ①: Analysis of Cosmic Ray Detection via Amplification Gain Variation
The objective was to verify how changes in the circuit's amplification gain affect the distribution of energy peaks and the degree of noise interference. Using a CsI scintillator, I conducted measurements across five gain levels: 1.5, 1.8, 2.0, 3.0, and 4.0. To ensure a standardized comparison, all detection counts were normalized to hourly rates. The results indicated that clear energy peaks were visible at gains of 1.5, 1.8, and 2.0; however, at gains of 3.0 and 4.0, the peaks became indistinguishable as noise signals were simultaneously amplified. This suggests that while higher gain increases sensitivity, it also elevates the noise floor to a point where cosmic ray signals, which have a naturally broad distribution and low pulse height, merge with the noise, making definitive peak identification difficult.
4. Experiment ②: Detection of Specific Energy Peaks Using Radioactive Soil
Based on the results of Experiment ①, the amplification gain was fixed at 2.0 to balance sensitivity and noise suppression. The objective was to verify if specific energy peaks from radioactive cesium could be detected in soil samples. I performed measurements on contaminated soil and applied a background subtraction process during analysis to isolate the sample's inherent radiation. The results showed a significant increase in total counts compared to the background, particularly within the ADC range of 500 to 1024. Although the detector successfully captured radiation from the soil, the resulting energy distribution was too wide to confirm unique photopeaks required for radionuclide identification. This may be attributed to interference from other isotopes within the soil or the performance limitations of the portable hardware, suggesting that more refined experimental conditions are necessary for precise analysis.
5. Summary and Future Outlook
This study confirmed that varying the amplification gain significantly shifts the distribution and visibility of signal peaks. While the successful detection of radiation from soil was achieved at a gain of 2.0, the current energy resolution remains a barrier to definitive identification. Future research will focus on implementing advanced peak detection algorithms and improving environmental noise isolation to isolate specific radionuclides effectively.
References:
Kumagai, K. et al., "Partial Correlation between Ground-level Muon Detection Frequency and Surface Temperature, Humidity, and Atmospheric Pressure by Weather in Akita Prefecture," Journal of Science EGGS, 4, 2110004 (2021).
Acknowledgments:
I would like to express my gratitude to Dr. Katsuo Tanaka, Senior Researcher at Waseda University and CEO of Accel Kitchen LLC, as well as Mr. Ryuta Saito of Tohoku University and Accel Kitchen LLC, and other mentors for their cooperation in this research. I also wish to thank Mr. Keiichiro Kikuchi of Fukushima Prefectural Fukushima High School for his guidance and advice.