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

在本研究中，通过改进/开发加速器质谱仪（AMS）的离子源和探测器以及改进样品制备技术，成功地开发了冰芯样品中宇宙射线产生的长寿命放射性核的分析方法，即^<10>Be, ^<26>Al和^<36>Cl。所有这三种放射性核都可以在南极富士圆顶获得的真实冰芯样本中检测到。从质量小于10 g的冰芯样品中获得的^<10> be数据可以清楚地探测到1500-1800年“小冰期”太阳活动变化的影响。在冰芯样品中分析^26<Al>的另一个具有挑战性的课题也取得了成功，尽管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，^<10>Be/^<36>Cl数据与以前在其他地方获得的报告有相当大的偏差。这可能表明初始的^<10>Be/^<36>Cl值随时间/地点而变化，表明难以使用^<10>Be/^<36>Cl数据进行测年。本研究中建立的技术将用于分析从Dome Fuji获得的3000 m冰芯样本中的这些放射性核，以进行补充定年，并阐明过去100万年的太阳气候变化，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.