[en] The author gives an overview of his research works in the field of gamma spectroscopy. First, he recalls some results of experiments performed for the study of peculiar structures associated with different modes of nucleus rotation, and notably in the case of collective rotation of deformed and even super-deformed nuclei. Then, he details tools and methods used to experimentally determine the level scheme. The main characteristics of steady and radioactive beams are briefly presented, and their complementarities and differences are highlighted. Specific spectrometers and sensors are described. In a last chapter, the author discusses several research projects he is involved in, and more particularly the 'gamma tracking' which is the fundamental principle for gamma multi-sensors of the next generations

No abstract available

[en] Recently spectacular technical developments have been achieved to increase the resolving power of large γ-ray spectrometers. With these new eyes, physicists are able to study the intricate nature of atomic nuclei. Concurrently more and more complex multidimensional analyses are needed to investigate very weak phenomena. In this article, we first present a software (DATABASE) allowing high fold coincidences γ-rays events to be stored on hard disk. Then, a non-conventional method of analysis, anti-gating procedure, is described. Two physical examples are given to explain how it can be used and Monte Carlo simulations have been performed to test the validity of this method

[en] A new method for optimizing the processing of events from a highly efficient large array γ-ray detector is described in this article. The spherical gates technique, developed to project high-fold events, consists of optimizing n-dimensional gate shape as a function of peak width and shape of each detector. Formulas in closed form are proposed for determining the projected statistics from coincidence fold and peak shape and for estimating the increased quality of projected spectra. This procedure has been tested on high-fold, high statistics data sets including superdeformed cascades. Compared to the classical 'square-gate' technique, better peak-to-background ratios as well as a reduction in fluctuations are observed. A quality parameter is defined to characterize the optimal parameter set. This method leads roughly to a gain in spectral quality equivalent of one fold. It is also shown that the efficiency of the method increases with coincidence fold. This should be particularly suited for future higher-fold data sets. The consequences of a γ-peak profile with a left tailing due to neutron damage is also studied and a method for processing correctly this kind of data is proposed. (author)

[en] A long run performed with EUROGAM II allowed remeasuring the ¹⁴⁹Gd superdeformed (SD) band 1. The ΔI = 4 bifurcation in band 1 is confirmed and two resolved γ-ray transitions linking the SD band 1 and the normal deformed states have been observed. (author)

[en] The quadrupole moments of the first two superdeformed (SD) bands in the nucleus ¹⁵¹Tb have been measured with the doppler shift attenuation method (DSAM) using the EUROGAM γ-ray spectrometer. The first excited band (B2) is identical to the yrast SD band of ¹⁵²Dy in terms ofdynamical moments of inertia and γ-ray energies. The measured relative quadrupole moments of the yrast band (B1) with respect to the band B2 are nicely reproduced by self-consistent Hartree-Fock calculations. The variation of the Q₀ value at the bottom of the yrast band suggests a large admixture between wave functions in the normal and the SD wells. This could explain the rather high deexcitation spin for the yrast band. (orig.)

[en] With the advent of multi-detector arrays, many tasks that are usually performed by physicists, such as energy calibration, become very time consuming. There is therefore a need to develop more and more complex algorithms able to mimic human expertise. Fuzzy logic proposes a theoretical framework to build algorithms that are close to the human way of thinking. In this paper we apply fuzzy set theory in order to develop an automatic procedure for energy calibration. The algorithm, based on fuzzy concepts, has been tested on data taken with the EUROBALL IV γ-ray array

[en] The aim of this work is to get more information about the population mechanism of superdeformed (SD) bands in the A ≅150 mass region. Usually, SD bands were populated in heavy-ion induced fusion reactions and most of them have been seen in xn exit channels. With the new generation of gamma-ray arrays, we are able to see SD structures populated in charged particle channels. Four experiments have been performed at the Vivitron accelerator in Strasbourg using the EUROGAM 2 spectrometer to study these phenomena (especially in α-particle channels). (author)

No abstract available

[en] An experiment has been performed to investigate the structure at high spin of the neutron-deficient polonium isotopes using the Recoil Filter Detector coupled to the EUROBALL IV gamma array. High spin states of ^200,201Po have been populated by the ³⁰Si+¹⁷⁶Yb reaction at a beam energy of 160 MeV. We report here the performances of the RFD + EUROBALL IV coupling. (author)