|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1994 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1993 : ¥1,400,000 (Direct Cost : ¥1,400,000)
This study focussed on some basic problems to attain a high accuracy radiocarbon dating of ancient cultural properties and documents, by using a Tandetron accelerator mass spectrometer of the Dating and Materials Research Center, Ngaoya University.
As a first step, a sample preparation method was developed to produce graphite from Co_2, using Fe as a catalyst and H_2 as a reducer. When a graphitized sample is used, carbon amount necessary for one measurement was reduce to 1 mg, and one sigma errors of ^<14>C dates to <plus-minus>40 years. It proved that the sample graphitization is indispensable for ^<14>C dating of cultural properties with rather limited sample amount available. As a second step, we have established a procedure to obtain a more accurate ^<14>C dates by correcting the effect of carbon isotopic fractionation of carbon samples.
Repoducibility tests are conducted for several graphite materials prepared from each ancient cultural sample. The tests indicated that ^<14>C measurements should be repeated more than 3 times to get a highly reliable results. In addition, a program for calibration from ^<14>C date to calendar year, developed using dendrochronology of wood samples grown mainly in North America and Europe, has been applied successfully to the Japanese samples.
Radiocarbon dating was conducted for some Japanese cultural-property samples, such as old paper documents, document container boxes, wooden statues, ancient iron swords, iron statues, silk cloth samples, ancient ship fragments, old bone samples, etc. The calendar years of those samples, estimated by calibrating the ^<14>C dates measured with a Tandetron AMS,are consistent with historical estimations. The radiocarbon dating is also proved to be useful to figure out imitations.