Determination of Natural Radioactivities, Especially Cosmic-Ray-Produced Radioactivities in Meteorites.

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The work was composed of 2 parts. First, using gamma-ray counter, cosmic ray produced radioactivities in chondrites, and second, using mass spectrometer, long lived radioactive nuclides in meteorites, were determined.Both works were starting from the improvement of the equipments, because natural radioactive nuclides which should be measure, exist extremely small amounts. It is necessary to improve sensitivities and resolutions of devices for the present purpose(report on improvement of mass spectrometer: report No.1 in next page). Details of each work are as follows:(1). Determination of Cosmic Ray Produced Radioactive Nuclides in Chondrite(1)-1. Cosmic Ray Produced ^<26>Al and ^<53>Mn in Chondrites which fell or found in Japan: Details of methods and results were described in reports No.3.(1)-2. Cosmic Ray Produced Stable Rare Gases: For comparison of the above data, rare gases in Japanese chondrites were determined(report No.2).(1)-3. Chondrite Aomori: Cosmic ray produced radioactive nuclides in the chondrite Aomori were redetermined. Results will be included in report No.4.(1)-4. Chondrite Kokubunji: Radioactivities of five specimens of the chondrites were measured. As a results, it is concluded that the original body of the chondrite was larger than 500kg, and when it collide earth's atmosphere, it lost more than 90%. This data will be published soon(report No.5).(2) ^<87>Rb-^<87>Sr Relation in Primitive Enstatite Chondrites: Rb-Sr systems of two E3, Qingzhen(observed fall) and Yamato-6901(find), one E5, Yilmia (find) and one E6, Kailpur(observed fall) were investigated and found that those primitive chondrites did not have age of 4.6xlO^9 years(report No.6 and 7v.