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A three-detector measuring system making use of a pure-Ge detector combined with two Si(Li) detectors has been developed. The efficiency curve of the pure-Ge detector has been determined easily as relative efficiencies to those of the existing Si(Li) detectors, since this system allows us to analyze a sample with the pure-Ge and the Si(Li) detectors simultaneously under the same irradiating conditions. It is found that detection efficiencies of the pure-Ge detector decrease just above the absorption edge of Ge owing to absorption of X-rays in the dead layer of the detector. Accuracy of the efficiency curve thus obtained was confirmed by analyzing a few samples whose elemental concentrations are known. It is confirmed that a pure-Ge detector can be used in place of a Si(Li) detector for the purpose of analysis of elements Z ≧ 19, since its energy resolution is almost equal to that of a high-performance Si(Li) detector and efficiencies at high energies are far better. Moreover, it becomes possible to detect prompt γ-rays and to analyze light elements such as fluorine, which arouses much interest from the point of view of environmental contamination. Detection limit of fluorine is found to be less than 0.1 ppm for water samples.

We recently developed and reported a three-detector measuring system making use of a pure-Ge detector combined with two Si(Li) detectors. The efficiency curve of the pure-Ge detector was determined as relative efficiencies to those of the existing Si(Li) detectors and accuracy of it was confirmed by analyzing a few samples whose elemental concentrations were known. It was found that detection of fluorine becomes possible by analyzing prompt γ-rays and the detection limit was found to be less than 0.1 ppm for water samples. In this work, a method of quantitative analysis of fluorine has been established in order to investigate environmental contamination by fluorine. This method is based on the fact that both characteristic x-rays from many elements and 110 keV prompt γ-rays from fluorine can be detected in the same spectrum. The present method is applied to analyses of a few environmental samples such as tealeaves, feed for domestic animals and human bone. The results are consistent with those obtained by other methods and it is found that the present method is quite useful and convenient for investigation studies on regional pollution by fluorine.

The path to the synthesis of super heavy elements is strongly hindered by the competition between fusion and quasi-fission in heavy ions reactions at near barrier energies. We report on a recent experimental investigation performed at the ALTO facility of IPN Orsay, France on the heavy-ion collision around the Coulomb barrier of ³²S+¹⁹⁷Au. The fission-fragment mass and total kinetic energy were measured by the double arm mass spectrometer for binary fragments CORSET, using the double time of flight approach. The asymmetric structure on top of the predominant symmetric one may suggests the contribution from either quasi-fission or pre-equilibrium fission or might be driven by shell effects in the compound nucleus fission. To get further insight on such puzzling cases situated at the crossroads of the various opened channels, we extended the measurement to coincident prompt γ -rays, of low and high energy. For this purpose, the prompt γ-rays following fission were detected by the coupled high efficiency ORGAM array consisting of 10 Compton suppressed Germanium detectors (BGO shielded), located at backward angles and the first cluster of the future PARIS calorimeter consisting of 9 close packed phoswich detectors and another single phoswich, together covering a wide angular and energy range.