[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] Absolute measurements of neutron fluence are an essential prerequisite of neutron-induced cross section measurements, dosimetric investigations and neutron beam lines characterisation. Independent and precise neutron flux measurements can be performed with respect to the H(n,p) elastic cross section. However, the use of silicon proton recoil detectors is not straightforward below incident neutron energy of 1 MeV, due to a high background in the detected proton spectrum. A new gaseous proton-recoil detector based on a double ionisation chamber, has been designed to answer the challenge. The detector is constituted by a H-rich deposit (polypropylene, mylar foil or tristearin deposit), and a segmented ΔE-E ionization chamber (4*4*12 cm³), read by a 64 pads Micromegas-based detection plane. The chamber is filled with gas (CF₄ or N₂-CO₂) at an adjustable pressure, from few tens of mbar to few tens of 100 mbar, to reduce as much as possible the detector sensitivity to Compton electrons. Tests have confirmed the low electron sensitivity of the detector, making it well suited for neutron energies down to 200 keV in a gammas and electrons dense environment. The ΔE-E coincidences, coupled to a 3D proton track analysis, enables the disentanglement between direct and scattered neutrons

[en] Today with the advent of intense radioactive beams, we have access to nuclear spectroscopy and reaction studies of nuclei far from stability. It has been demonstrated that Time Projection Chambers (TPC) method can be very effective as an active target for such studies yielding low thresholds, efficiency and luminosity. To this end a Generic Electronic system for TPCs (GET) is in development and will cover small to medium sized instrumentation (64 to 32 k channels) with a relatively wide charge dynamic ranges for event rates of up to 1 kHz. The 64-channel AGET (ASIC for GET) front-end circuit has been developed to perform the amplification, detection and analog storage of the shaped detector signal before its digitization by an external 12-bit ADC. This design offers a large flexibility in sampling frequency (100 MHz max.), peaking time (16 values from 50 ns to 1 μs), gain (4 ranges from 120 fC to 10 pC per channel) and signal polarity (negative or positive). Fabricated using 0.35 μm CMOS technology, the AGET prototype is under test and the first results are presented. (authors)

[en] Proton-rich isotopes of zinc and germanium, ⁵⁷Zn and ⁶¹Ge, have been produced by fragmentation of a ⁷⁰Ge beam at the LISE3 facility of GANIL. Their main decay characteristics have been studied after implantation in a double-sided silicon strip detector. In addition, the production cross-sections of proton-rich isotopes in the copper-to-germanium region have been determined. These cross-sections are much lower than predicted by the EPAX formula. These findings question to some extent the production rates expected for present and future fragmentation facilities. (orig.)

[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] Spherical time projection chambers (TPC), also known as spherical proportional counters, are employed in the search for rare phenomena, such as light Dark Matter candidates. The spherical TPC exhibits a number of essential features, making it a promising candidate for the search of neutrinoless double beta decay (ββ0ν). A tonne-scale spherical TPC experiment could cover a region of parameter space relevant for the inverted mass hierarchy with a few years of data taking. In this direction, the major R&D goal of the R2D2 effort is the demonstration of the required energy resolution. First results from an argon-filled prototype detector are reported, demonstrating an energy resolution of 1.1% FWHM for 5.3 MeV α tracks in the 0.2 to 1.1 bar pressure range. This is a major milestone in terms of energy resolution, paving the way for further studies with xenon gas, and the possible use of this technology for ββ0ν searches. (paper)

[en] Two-proton radioactivity was observed in 2002 in the decay of ⁴⁵Fe. However, the experiments performed at that time did not allow the observation of the two protons directly. We present here a new setup based on the principle of a time-projection chamber that 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 and to determine thus their individual energies and their relative angle. We will discuss the setup in all necessary details and describe its performances in the context of two-proton radioactivity and β- delayed two-proton emission studies.