11:45 AM - 12:00 PM
[HCG22-11] Classification of molten particles collected in Hiroshima City based on FIB-TOF-SIMS analysis
Keywords:“black rain” caused by atomic bombs, molten particles, TOF-SIMS
[Introduction]
Soil samples are currently being examined as part of the re-delineation of the area where the “black rain” is said to have fallen, but it is hoped that new samples reflecting the environment at that the time will be found because of the decrease in radiation dose and soil agitation[1]. One sample that has attracted our attention is a group of particles called molten particles collected by Wannier et al. in Hiroshima City[1]. However, the molten particles should have various origins, such as meteorites and volcanoes. Therefore, it is necessary to obtain information to identify the particles. In this study, we used a focused ion beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) systems[3] developed in our laboratory, which is capable of simultaneous imaging of all elements.
[Methods]
(1) Isotope ratio anomalies in neutron capture reactions
We focused on isotope ratio anomalies of elements in neutron capture reactions caused by neutron flux irradiation by the atomic bomb. In this study, 10B(n,α)7Li, which is called BNC reaction, was focused on and analyzed by with the TOF-SIMS. The isotope ratio analysis showed that the most of the yellow particles had high isotope ratios of both B and Li, and a positive correlation was observed, which is presumed to be observed in the BNC reaction. This indicates the possibility that some of the yellow molten particles are of the atomic-bomb origin.
(2) Classification and characteristics of each color of Hiroshima molten particles
Since it is difficult to distinguish global fallout from molten particles based on isotopic ratio anomalies alone, we focused on the fact that molten particles are classified into four colors (black, red, silver, and yellow) and compared the composition and the textures of the cross-sections of the particles. As a result, there was no particle-specific characteristics in the composition. However, we found that each color has its own unique texture. This allowed us to produce basic data that captured the characteristics of Hiroshima molten particles.
Acknowledgments: This study was conducted as part of the Ministry of Health, Labour and Welfare (MHLW) “Research and Study on Atomic Bombing Weather and Soil in FY2024.
Soil samples are currently being examined as part of the re-delineation of the area where the “black rain” is said to have fallen, but it is hoped that new samples reflecting the environment at that the time will be found because of the decrease in radiation dose and soil agitation[1]. One sample that has attracted our attention is a group of particles called molten particles collected by Wannier et al. in Hiroshima City[1]. However, the molten particles should have various origins, such as meteorites and volcanoes. Therefore, it is necessary to obtain information to identify the particles. In this study, we used a focused ion beam time-of-flight secondary ion mass spectrometry (FIB-TOF-SIMS) systems[3] developed in our laboratory, which is capable of simultaneous imaging of all elements.
[Methods]
(1) Isotope ratio anomalies in neutron capture reactions
We focused on isotope ratio anomalies of elements in neutron capture reactions caused by neutron flux irradiation by the atomic bomb. In this study, 10B(n,α)7Li, which is called BNC reaction, was focused on and analyzed by with the TOF-SIMS. The isotope ratio analysis showed that the most of the yellow particles had high isotope ratios of both B and Li, and a positive correlation was observed, which is presumed to be observed in the BNC reaction. This indicates the possibility that some of the yellow molten particles are of the atomic-bomb origin.
(2) Classification and characteristics of each color of Hiroshima molten particles
Since it is difficult to distinguish global fallout from molten particles based on isotopic ratio anomalies alone, we focused on the fact that molten particles are classified into four colors (black, red, silver, and yellow) and compared the composition and the textures of the cross-sections of the particles. As a result, there was no particle-specific characteristics in the composition. However, we found that each color has its own unique texture. This allowed us to produce basic data that captured the characteristics of Hiroshima molten particles.
Acknowledgments: This study was conducted as part of the Ministry of Health, Labour and Welfare (MHLW) “Research and Study on Atomic Bombing Weather and Soil in FY2024.