2020 Fiscal Year Final Research Report

Understanding of the r-process environment through the precise nuclear spectroscopic works of the unknown nuclei in the vicinity of neutron magic number N=126

Research Project

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Project/Area Number	17H01132
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Research Field	Particle/Nuclear/Cosmic ray/Astro physics
Research Institution	High Energy Accelerator Research Organization
Principal Investigator	HIRAYAMA Yoshikazu 大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 研究機関講師 (30391733)
Co-Investigator(Kenkyū-buntansha)	宮武宇也大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 教授 (50190799) 渡邉裕大学共同利用機関法人高エネルギー加速器研究機構, 素粒子原子核研究所, 准教授 (50353363)
Project Period (FY)	2017-04-01 – 2021-03-31
Keywords	元素合成 / レーザー共鳴イオン化 / 質量測定 / 国際情報交換 / ベルギー
Outline of Final Research Achievements	In order to study the properties of heavy short-lived nuclei more precisely, we have successfully developed the following three items; (1) laser system and related equipment for the precise laser resonance ionization spectroscopy of the short-lived nuclei which are in the gas-jet with good directivity, (2) 3 dimensional-tracking-type multi-segmented proportional gas counter with high detection efficiency and low background rate to detect the electrons emitted from rare short-lived nuclei for the precise nuclear decay spectroscopy, (3) install and operation of multi-reflection time of flight mass-spectrograph in order to measure the nuclear mass with one millionth precision. By using the equipment, we could successfully measure the nuclear half-lives and masses of rare heavy nuclei produced at the KISS (KEK isotope separation system) facility.
Free Research Field	実験核物理
Academic Significance and Societal Importance of the Research Achievements	精密な短寿命核の性質（崩壊寿命や質量）を測定可能な実験装置を開発し、これらを駆使して187Ta、198Irなど約２０種類程の希少短寿命核の性質を研究した。これらの希少短寿命核は非常に高温（10億度）で高い中性子密度の星の中で生成されたと考えられている。その性質を研究することは、金や白金といった身の回りに存在する重い安定な元素が誕生した天体環境の謎を解き明かす上で不可欠であり、学術的意義は非常に高い。