[en] The efficiency increasing in four π (EUROGAM, EUROBALL, DIAMANT) is achieved by an increase in the granularity, hence in the event counting rate in the acquisition system. Consequently, an evolution of the architecture of readout systems, coding and software is necessary. To achieve the required evaluation we have implemented a parallel architecture to check the quality of the events. The first application of this architecture was to make available an improved data acquisition system for the DIAMANT multidetector. The data acquisition system of DIAMANT is based on an ensemble of VME cards which must manage: the event readout, their salvation on magnetic support and histogram construction. The ensemble consists of processors distributed in a net, a workstation to control the experiment and a display system for spectra and arrays. In such architecture the task of VME bus becomes quickly a limitation for performances not only for the data transfer but also for coordination of different processors. The parallel architecture used makes the VME bus operation easy. It is based on three DSP C40 (Digital Signal Processor) implanted in a commercial (LSI) VME. It is provided with an external bus used to read the raw data from an interface card (ROCVI) between the 32 bit ECL bus reading the real time VME-based encoders. The performed tests have evidenced jamming after data exchanges between the processors using two communication lines. The analysis of this problem has indicated the necessity of dynamical changes of tasks to avoid this blocking. Intrinsic evaluation (i.e. without transfer on the VME bus) has been carried out for two parallel topologies (processor farm and tree). The simulation software permitted the generation of event packets. The obtained rates are sensibly equivalent (6 Mo/s) independent of topology. The farm topology has been chosen because it is simple to implant. The charge evaluation has reduced the rate in 'simplex' communication mode to 5.3 Mo/s and at 4.4 Mo/s in 'full-duplex' mode. The obtained results are very satisfactory for an autonomous acquisition of DIAMANT

[en] Absolute measurements of neutron fluence are an essential prerequisite of neutron-induced cross section measurements, neutron beam lines characterisation and dosimetric investigations. Precise neutron flux measurements can be performed with respect to the H(n,p) elastic cross section. The use of this technique, with silicon proton recoil detectors, is not straightforward below incident neutron energy of 1 MeV, due to a high background in the detected proton spectrum. Experiments carried out at the AIFIRA facility identified its origin. Based on these investigations, a gaseous recoil-proton detector has been designed, with a reduced low energy background. Preliminary results of the first tests of the developed detector are discussed here. (authors)

[en] After the recent discovery of two-proton radioactivity, an important effort has been made in order to observe each emitted particle individually. Such kind of studies may result in energy and angular correlation measurements of the protons, which are required to give a precise theoretical description of this exotic decay mode. In this frame, we performed an experiment at the GANIL/SISSI/LISE3 facility, where we used a Time Projection Chamber to observe tracks of protons in the decay of ⁴⁵Fe, produced in projectile fragmentation reactions

[en] Studies of β-delayed emission of protons for ⁴³Cr and ⁵¹Ni were performed with a Time Projection Chamber. This detection setup allows to reconstruct in the three-dimensional space the tracks of the protons emitted. For the first time, β-delayed emission of two protons is directly observed for ⁴³Cr and ⁵¹Ni. The question about correlations between protons can be accessed. Finally, we show that ⁴³Cr can emit up to three delayed protons.

[en] In the present paper, we present measurements that led to the discovery of two-proton radioactivity. After the first observation of this decay mode for ⁴⁵Fe, new measurements evidenced this decay mode also for ⁵⁴Zn and most likely ⁴⁸Ni. A new detector based on the time-projection chamber principle allowed now to visualize the two protons directly

[en] The decay of the ground-state two-proton emitter ⁴⁵Fe was studied with a time-projection chamber and the emission of two protons was unambiguously identified. The total decay energy and the half-life measured in this work agree with the results from previous experiments. The present result constitutes the first direct observation of the individual protons in the two-proton decay of a long-lived ground-state emitter. In parallel, we identified for the first time directly two-proton emission from ⁴³Cr, a known β-delayed two-proton emitter. The technique developed in the present work opens the way to a detailed study of the mechanism of ground state as well as β-delayed two-proton radioactivity

[en] Two-proton radioactivity is an exotic decay mode for very proton-rich nuclei. It was observed experimentally for the first time in 2002 for the nucleus ⁴⁵Fe but the two protons could not be directly detected. So a new detector has been developed, a Time Projection Chamber, to individually observe the two protons emitted. It was used successfully during two experiments for the study of ⁴⁵Fe and ⁵⁴Zn. Energy correlations have been studied and the relative angle between the two protons is calculated.

[en] The two-proton radioactivity has been observed experimentally in 2002, at projectile fragmentation facilities, more than 40 years after the first theoretical prediction of this process. First observations were indirect measurements, using standard silicon detector devices. Since then, a new generation of experiments allowed for a direct observation, and opened the field of more detailed studies, using tracking devices for the detection of the emitted protons.

[en] Two-proton radioactivity was observed in two experiments in 2002 in the decay of ⁴⁵Fe. However, these experiments did not allow the observation of the two protons directly. In the present paper, we present a new setup based on the principle of a time projection chamber which enabled us for the first time to identify directly the two protons. The new setup permits the observation and reconstruction in three dimensions of the traces of the protons. We will discuss the setup and describe its performances.

[en] The two protons emitted in the decay of ⁵⁴Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p² configuration for the two-proton emission. After ⁴⁵Fe, the present result on ⁵⁴Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope.