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  • Author or Editor: T. Nozaki x
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Abstract  

From 1960s to 1980s many groups in the world actively studied and utilized charged particle activation analysis (CPAA) mainly for absolute determination of B, C, N, and O in high-purity substances, particularly semiconductor materials. Here, after a short historical note on CPAA, works of the author’s group mainly at RIKEN are outlined and then his opinion is shown about how to anticipate on the present shrinking of CPAA.

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Abstract  

A technique has been developed for oxygen depth profiling in a thickness range of 5 to about 100 mg cm−2 by activation with the16O(3He, p)18F reaction. An apparatus was set up for the activation of oxygen with a uniform probability along the depth, and a method has been devised for step-wise etching of the activated sample. This technique has been applied to the study of oxygen behaviour in heat treatment of silicon under various conditions.

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Abstract  

Charged particle activation analysis has proved to be useful for the determination of surface oxygen under any atmospheric conditions. The16O(3He, p)18F reaction was used for activation. The sample in a form of two plates was contacted intimately with each other and bombarded with3He particles of such an energy as to give the maximum cross section at the inside surfaces of the plates. The18F thus formed in the forward plate was then measured. Oxygen in the gap between the two plates can be shown to cause no noticeable interference. This method was applied to silicon, aluminium and lead in four different ambient pressures.

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Abstract  

Carrier- and salt-free42K milked from an42Ar–42K generator was utilized for isotope dilution analysis of potassium in ultra-pure water. Potassium in the sample marked with the42K was shown to be concentrated easily 60 times by crown-ether extraction and acid back-extraction to be determined by atomic absorption spectrophotometry. The same extractions proved to be effective for removing the reagent blank. Cerenkov radiation counting was often suitable for42K measurement. The42K was used also for studying the interaction of ultra-low concentrations of potassium with vessel walls.

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Abstract  

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however, some pretreatment of the samples will be necessary.

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Abstract  

Previously undetermined three rare earth elements (REE's), Pr, Nd and Er, in acidic hot spring and crater lake waters were determined at ppb levels by neutron actavation analysis with the standard addition technique. Errors on final detemined values were 7.1–56%. Combining the present results and the results previously obtained amounts to the determination of all 14 naturally occuring REE's in the waters.

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Abstract  

Determination of Th and U in acidic hot spring and crater lake waters was investigated by neutron activation analysis (NAA). Before neutron irradiation, Th and U were preconcentrated and separated from interfering nuclides such as alkali metals and halogens by coprecipitation with aluminium. Irradiation was carried out in two ways, viz., irradiation with Cd foil wrapping (epithermal NAA) and irradiation without Cd foil wrapping (normal NAA). The final determined values of Th and U were at ppb levels. Higher reliability of the determined values was obtained for Th than for U. It was found that epithermal NAA was more effective for the determination of these two actinides than normal NAA and was more effective for the determination of U than that of Th.

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Abstract  

Determination of the rare earth elements (REE's) in acidic hot spring and crater lake waters by neutron activation analysis (NAA), in which activation was performed mostly by epithermal neutrons (epithermal NAA) was investigated. Nine REE's, La, Ce, Sm, Eu, Tb, Ho, Tm, Yb and Lu, out of fourteen naturally existing REE's were determined at ppb levels with satisfactory precision. The epithermal NAA was found to be more effective in the determination of Sm, Tb, Ho and Yb than normal NAA, in which activation was performed mainly by thermal neutrons. Combined use of the epithermal and normal NAA's enabled the determination of eleven REE's, La, Ce, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu.

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Abstract  

Hot spring water and crater lake water samples were analyzed for their rare earth elements: (REE's) by neutron activation method, which, in the irradiation, sample preparation, incorporated a coprecipitation process in which aluminium was used as a collector. Ten REE's, La, Ce, Sm, Eu, Gd, Tb, Dy, Tm, Yb and Lu, were consequently detected and determined at the ppb level with satisfactory precision. It was shown that the aluminium coprecipitation is effective in enhancing concentrations of the REE's and reducing the amounts of interfering nuclides before neutron irradiation.

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Abstract  

Convenient processes are described for the charged particle activation analysis for carbon, nitrogen, and oxygen in semiconductor silicon. Suitable activation reactions and incident particle energies were selected, and the interferences examined; the activation curves for the Si+3He→11C and Si+3He→18F reactions, which may seriously interfere with3He activation analysis, were measured, and the interference caused by the fission of the matrix itself is discussed. A simple technique for the separation of11C present in silicon is proposed. Reliable determination of as low as several parts per billion of the three elements has thus become possible. Semiconductor silicons of various origin were analyzed for C, N and O, and the behaviour of these elements during zone-melting is reported.

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