Development of a method to measure radioisotopes in organic materials with high sensitivity for the next generation of astroparticle physics experiments

2023 Fiscal Year Final Research Report

• Project/Area Number: 21H01105
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Tohoku University
• Principal Investigator: Ichimura Koichi 東北大学, ニュートリノ科学研究センター, 助教 (80600064)
• Co-Investigator(Kenkyū-buntansha): 坂口 綾 筑波大学, 数理物質系, 教授 (00526254)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 極低放射能 / 放射線計測 / 微量元素分析 / ICP-MS / ゲルマニウム検出器

Outline of Final Research Achievements

The development of an ultra-low background detector is necessary for the search for extremely rare events such as neutrinoless double beta decay. It is also necessary to develop a method for measuring radioactivity in the detector components of such ultra-low background detectors with high sensitivity. In this research project, we have established a method for measuring trace amounts of uranium and thorium in organic materials by combining an ashing device and inductively coupled plasma mass spectrometry. The detection limit of the method was found to be one picogram per gram of organic material for now. We also established a method to measure RI amount with world-class high sensitivity by constructing a low-background shielding for the ultra-low background high-purity germanium detector. Using these methods, we measured RI amounts in candidate components for the next generation of extremely rare event search detectors.

Free Research Field

非加速器素粒子実験

Academic Significance and Societal Importance of the Research Achievements

本研究により、次世代極稀事象探索検出器のスクリーニングをより高感度で行うことが可能になった。灰化装置と誘導結合プラズマ質量分析法を組み合わせた有機物中の放射性不純物量測定に関し、数グラムの有機物を灰化することが出来ること、および有機物1グラムあたり1ピコグラムの濃度での測定に必要なクリーン環境や実験器具の洗浄方法を提示できた。今後濃縮法との組み合わせやクリーン環境や実験器具の整備を行うことでさらに高感度測定出来ることも示すことができた。極低放射能ゲルマニウム検出器に関しても10 kg程度の試料まで測定することが可能であり、様々な極稀事象探索検出器のための測定に活用することができる。