1992 Fiscal Year Final Research Report Summary
Ultrasensitive methods of measuring isotope ratios of heavy elements using accelerator mass spectrometry
| Project/Area Number |
02554003
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAMURA Masanobu Kyoto Univ.Dept.Phys.Lecturer, 大学院・理学研究科, 講師 (90025479)
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| Co-Investigator(Kenkyū-buntansha) |
KOHNO Masuchika Kyoto Univ.Dept.Nucl.Eng.Instruc., 大学院・工学研究科, 教務職員
OGINO Koya Kyoto Univ.Dept.Nucl.Eng.Instruc., 大学院・工学研究科, 助手 (40026034)
MURAKAMI Tetsuya Kyoto Univ.Dept.Phys.Instruc., 大学院・理学研究科, 助手 (50219896)
TAZAWA Yuji Kyoto Univ.Dept.Phys.Instruc., 大学院・理学研究科, 助手 (60124757)
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| Project Period (FY) |
1990 – 1992
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| Keywords | ACCELERATOR MASS SPECTROMETRY / ISOTOPE RATIO / ULTRASENSITIVE METHODS OF MEASURING / DATING / ENVIRONMENT MEASUREMENT / LONG-LIVED RADIOISOTOPES |
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| Research Abstract |
An accelerator mass spectrometry (AMS) system based on an 8UDH Pelletron at Kyoto University was developed. Long-lived radioisotopes of ^<36>Cl, ^<41>Ca and ^<129>I were interesting to study for dating and environment measurements. We were starting the AMS program with ^<14>C measurements in order to test and improve the reliability of our AMS system. We introduced a sputter ion source with 59 samples and operated the sample manipulation mechanism manually by monitoring its position with television and linear potentiometers. With x-y slits at the ion source, the beam transmission through the tandem accelerator was stable. The terminal voltage was controlled using ^<13>C_<4+> ions whic were dissociated at the terminal from molecular ions of ^<13>CH^-. ^<14>C ions were counted by a silicon detector. The background peaks of ^<14>N^<4+> and (^7Li_2) ^<4+> ions were separated using a 3 mum thick Al foil in front of the detector. We used sequential injection with slow cycling by varying the magnetic field of the bending magnet. The transmission was measured for ^<12>C and ^<13>C ions and we estimate the transimission for ^<14>C using the stripping efficiency. Sample materials of NBS oxalic acid standard were oxidized and the resulting CO_2 was purified cryogenically in a vacuum preparation system. It was converted to graphite by reducing the CO_2 on Fe catalyst with H_2 gas.
For the ^<36>Cl measurements, we tested the gas ionization chamber as the DELTAE counter in order to separate the isobar (^<36>S) and also tested the electrostatic deflector to reduced the backgroud ions of different charge states.
The graphitized sample of NBS was measured using sequential injection of ^<12>C,^<13>C and ^<14>C ions. Measured ^<14>C/^<12>C ratios show the reproducibility of our AMS system. We will start the research program of ^<14>C measurements and optimize the detector system for heavy elements.
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