Development of high-density and high-precision analytical method of cosmic-ray produced radionuclei in ice core samples

本研究通过改进/发展加速器质谱仪的离子源和探测器以及改进样品制备技术，成功地发展了冰芯样品中宇宙线产生的长寿命放射性核的分析方法，即^&lt；10&gt；Be、^&lt；26&gt；Al和^&lt；36&gt；Cl。在南极洲富士穹顶获取的真实冰芯样本中，可以检测到这三种放射性核素。在小于10g的冰芯样品中，可以清楚地探测到公元1500-1800年“小冰期”期间太阳活动变化的影响。另一个具有挑战性的课题是分析冰芯样品中的铝和铝，尽管还需要进一步提高束流强度和电离效率，以减少必要的珍贵冰芯样品的数量。另一方面，^&lt；10&gt；Be/^&lt；36&gt；CL数据显示与其他地方以前的报告有相当大的偏差。这可能表明初始^&lt；10&gt；Be/^&lt；36&gt；Cl值随时间/地点的不同而变化，这表明很难使用^&lt；10&gt；Be/^&lt；36&gt；Cl值进行测年。这项研究建立的技术将用于分析从富士圆顶获得的3000米冰芯样品中的这些放射性核素，以便进行补充测年，并阐明过去100万年来的太阳气候变化、地磁变化和全球气候变化。

In this study, development of analytical methods for cosmic ray-produced long-lived radionuclei in the ice core sample, i.e., ^<10>Be, ^<26>Al and ^<36>Cl, have been successfully conducted by modifying / developing ion sources and detectors of accelerator mass spectrometer (AMS) as well as improving sample preparation techniques. All these three radionuclei could be detected in the real ice core samples obtained at Dome Fuji in Antarctica. The effect of solar activity change during "little ice age" between 1500-1800 AD could be detected clearly in the ^<10>Be data obtained from ice core samples with less than 10 g weight. Another challenging topics of analyzing ^26<Al> in ice core samples were also succeeded, although further improvement of beam strength as well as ionization efficiency will be needed for decreasing necessary amount of precious ice core samples. ^<10>Be/^<36>Cl data, on the other hand, showed considerable deviation from the previous reports obtained in other places. This may suggest the variation of initial ^<10>Be/^<36>Cl values depending on the time/location, indicating difficulties to use ^<10>Be/^<36>Cl data for dating purposes. The techniques established in this study will be used for the analysis of these radionuclei in the 3,000 m ice core sample obtained from Dome Fuji in order to conduct supplemental dating as well as to elucidate solar climate change, geomagnetic change and global climate change in the last million years.