著者

平賀 章三 市川 米太

出版者

日本地質学会

雑誌

地質学論集

巻号頁・発行日

vol.29, pp.207-216, 1988-02

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The pumice-tuff for the blind test is dated by the quartz inclusion method. The samples were collected in Omachi clty, Nagano Prefecture,and their ages are assumed to be O.3 to O.4 Ma geologically.The assessed TL age is O.29±0.03 Ma(11%error). If the dry condition had been continued over the geological time,the expected age is O.26±0.02 Ma (7%),otherwise for wet condition O.32±0.02 Ma(7%)is expected. In this TL dating,taking account of the propagation of error,the associated error is assessed,based on the experimental error due to the reproducibility of the TL intenslty. The method of error assessment is described in detail on each stage of TL dating. Thus it was revealed that the quartz inclusion method is useful with the sufficient precision for the age of the order of l05 year,though depending on the TL characteristic of the sample.

著者

市川 米太 長友 恒人

出版者

奈良教育大学

雑誌

奈良教育大学紀要. 自然科学 (ISSN:05472407)

巻号頁・発行日

vol.23, no.2, pp.3-13, 1974-11

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In an earlier paper of this bulletin, the authors described how the thermoluminescent (TL) method may be an effective one for the dating of ancient pottery and it has an advantage over radiocarbon method. The present paper is concerned with some salient points in the development of the TL technique at our laboratory during the past 10 years. The results recently obtained from the typical potteries are shown, which contain the dating results for a series of shards from Ban-Chiang and those for a series of shards from Nara. The quartz and feldspar embedded in clay matrix have been exposed by the natural radiation since the last heating. The TL emitted from the ancient pottery is a measure of the total dose of this radiation. On the assumption that the natural dose-rate has been constant, the time elapsed since the firing of the pottery is estimated from the accumulated radiation dose and the dose per year. The TL dating used in the present investigation is the method which is known by the name of the inclusion method or the large grain method. For the estimation of the accumulated radiation dose we measured the TL of qualtz and feldspar inclusions with diameters of greater than 0.3 mm. Consequently, we could neglect the contribution from alpha particles which will only penetrate into the inclusions approximately 0.023 mm on average and are typically only from 10 to 20 % as efficient as beta or gamma radiation in the creation of TL. The environmental radiation and the radiation from the pottery itself were measured with CaSO4; Tm TL dosimeter developed by Matsushita Electric Ind. Co., Ltd.

著者

市川 米太

出版者

奈良学芸大学

雑誌

奈良学芸大学紀要. 自然科学 (ISSN:03693937)

巻号頁・発行日

vol.12, pp.51-57, 1964-02-29 (Released:2017-02-24)

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A new method for dosimetry of atomic bomb radiation in Hiroshima and Nagasaki is presented. Concerning the distribution of absorbed dose of atomic bomb radiation, only a few results already rapDrted ware insufficient to discuss the relation-ship between radiation hazard and radiation dose. Roof-tiles irradiated by the atomic bomb give off a glow, called thermoluminescence. By measuring the glow intensity, the radiation dose of the bomb can be measured. The equivalent gamma dose of bomb radiation is obtained by comparing the bomb glow curve with the Co60 gamma glow one. Glow curve from bomb radiation in the past is different in shape from that of the Co60 radiation at present. In general, the glow curve from Co60 radiation has three peaks at about 150゜C, 230゜C and 300 ゜C. But the glow curve from past radiation was found not to show any peak at about 150゜C, this is due, we interpret, to the decay at the normal temperature during the past 17years. The glow curve resulting from the bomb radiation was classified into three types, the first one is of the glow curve which does not decay at 230-C, the second is one which decays partly at 230゜C and the third is one which decays perfectly. The equivalent gamma doses which are shown in Table 1. were obtained from the sample of the first type.