Decay study of rare fission products with background reduction and time-stumped list mode data acquisition

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K05327
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Nagoya University
• Principal Investigator: Shibata Michihiro 名古屋大学, アイソトープ総合センター, 教授 (30262885)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 崩壊核分光 / オンライン同位体分離 / 核分裂生成物

Outline of Final Research Achievements

The nuclear decay data of a short-lived neutron-rich nuclei with a mass number around 150 have not been investigated in detail due to the small fission yield of 235U. The on-line isotope separator (KUR-ISOL) installed at the Kyoto University Reactor is an effective device can separate the nuclei of interests from fission products with high intensity. β-ray detectors which can installed in the through hole of the high solid angle Ge detector (clover detector) were developed, and β-γ coincidence measurements were performed using a time-stumped high-speed list mode data acquisition system. By reducing the background radiation in the reactor room, the nuclei of interests were measured. More detailed decay schemes of 153,154Pr were proposed, but, the γ-rays in the decay of 155Pr could not be identified. It was suggested that the fission yield and/or half-life of 155Pr may be smaller than the reported ones.

Free Research Field

応用核物理学

Academic Significance and Societal Importance of the Research Achievements

235Uの核分裂生成物の崩壊核データは、原子力の分野では崩壊熱の評価に重要であり、核物理の観点からは、原子核が変形する様子を知るのに興味深い領域である。本研究では、崩壊データが十分でない153～155Prを対象に京大原子炉附置のオンライン同位体分離装置(KUR-ISOL)で、高効率クローバー型Ge検出器にβ線検出器を組み合わせて、炉室内のバックグラウンドの影響を低減させて、時間情報を含む高速データ収集系を用いてβーγ同時計数測定を行った。153,154Prについては、より詳しい崩壊図式を作成することができた。一方、155Prについては、崩壊γ線は確認には至らなかった。