The proliferation of neutron detection applications based upon 3He counter has triggered a critical shortage of 3He gas. Nowadays there is an increasing demand for alternative neutron detectors that can cover large solid angles, have low sensitivity to gamma background and low cost. We present a low cost neutron detector based upon 3 cm diameter, 150 cm long cylindrical metal tube coated on the inside with a thin layer of 10B-enriched boron carbide (10B4C) fulfilled by 1 atm nitrogen.

We report the results of our investigations on high quality single crystal chemical vapor deposition (SC-CVD) diamonds to be used as ionizing radiation detectors. Recent progress in growth of synthetic diamonds of very high purity and high homogeneity has opened perspectives to a new type of UV photosensors in order to work with large volume two-phase liquid-Ar and/or liquid-Xe detectors, nowadays under design for next generation dark matter search. SC-CVD diamonds supplied by Brevetti Bizz firm of San Bonifacio (VR, Italy) were investigated and the results are presented and discussed. (C) 2012 Elsevier B.V. All rights reserved.

Nowadays there are mainly three types of detectors available for measuring radon concentrations: charcoal canisters, alpha-tracks and E-PERMs. We carried out measurements with the three types of detectors and we tested their performances over a wide range of radon concentrations, temperatures and humidities. We compared the results obtained with the different detectors and we critically evaluated the results.

A systematic study of alpha-beam heating effect on a windowless gas target through Rutherford scattering is described. For such measurements, an ion implanted commercial silicon detector to reveal 100-250 keV alphas is used coupled with a low-noise home-made preamplifier. The results Oil density reduction of the gas in the target due to beam heating are discussed and their importance for high precision cross section measurements at very low energies are underlined. (c) 2006 Elsevier B.V. All rights reserved.

We report on a new measurement of (14)N(p,gamma)(15)O for the ground state capture transition at E(p) = 360, 380 and 400 keV, using the 400 kV LUNA accelerator. The true coincidence summing effect-the major source of error in the ground state capture determination-has been significantly reduced by using a Clover-type gamma detector.

We analyse the total photonuclear cross section in the energy range from 0.2 to 1.2 GeV, recently measured in Frascati on C, Be and U. By employing a simple resonance-hole model for the various baryonic resonances, which exist in the above range, we find that the experimental cross sections can be fairly well reproduced if one assumes that the nuclear medium strongly increases the width of all resonances above the Delta

The GRAAL facility produces a highly polarized gamma-ray beam by Compton scattering of laser photons on the electrons of the European Synchrotron Radiation Facility (ESRF) at Grenoble. Preliminary results have been obtained with the LAGRANGE detector showing its excellent performances

Context. The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T similar or equal to 30 x 10(6) K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the red giant branch (RGB) phase of the star or to the pollution of the primordial gas by an early population of massive asymptotic giant branch (AGB) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. Aims. The activation of this cycle depends on the rate of the (15)N(p, gamma)(16)O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. Methods. We present a new measurement of the (15)N(p, gamma)(16)O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 x 10(6) K and 780 x 10(6) K. This range includes the (15)N(p, gamma)(16)O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. Results. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level.

In the framework of investigation of meson photo-production on proton and neutron in a deuterium target at the GRAAL experiment, we present a method to identify the vertex of interaction when in reaction products there are at least two charged particles, by the information provided by the cylindrical multiwire proportional chambers. By this device, we are able to obtain the direction of charged particles that leave the target after a photo-production reaction. For each charged particle, the device provides the coordinates of two points in the laboratory reference system, and the z-axis represents the beam direction. We calculate the trajectory of each charged particle and its cross point, representing the vertex of the reaction.

One of the very interesting aspects of high energy heavy-ion collisions experiments is a detailed study of the thermodynamical properties of strongly interacting nuclear matter away from the nuclear ground state. In this direction, many efforts were focused on searching for possible phase transitions in such collisions. We investigate thermodynamic instabilities in a hot and dense nuclear medium where a phase transition from nucleonic matter to resonance-dominated Delta-matter can take place. Such a phase transition can be characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the strangeness concentration) in asymmetric nuclear matter. In analogy with the liquid-gas nuclear phase transition, hadronic phases with different values of antibaryon-baryon ratios and strangeness content may coexist. Such a physical regime could be, in principle, investigated in the future high-energy compressed nuclear matter experiments which will make it possible to create compressed baryonic matter with a high net baryon density.

We report on the status of the 3He( 3He,2p) 4He experiment at the underground accelerator facility LUNA (Gran Sasso). The lowest projectile energies for the measured cross section correspond already to energies below the center of the solar Gamow peak (E 0=22 keV). The data provide no evidence for the existence of a hypothetical resonance in the energy range investigated. Although no extrapolation is needed anymore (except for energies at the low-energy tail of the Gamow peak), the data must be corrected for the effects of electron screening, clearly observed the first time for the 3He( 3He,2p) 4He reaction. The effects are however larger than expected and not understood, leading presently to the largest uncertainty on the quoted S(0) value for bare nuclides (=5.40 MeVb)

The Sigma beam asymmetry in the photoproduction of neutral pions from quasi-free nucleons in a deuteron target was measured for the first time between 0.60 and 1.50 GeV, with the GRAAL polarized and tagged photon beam. The asymmetry values from the quasi-free proton were found equal to the ones extracted from a pure proton target. The asymmetries from quasi-free proton and quasi-free neutron were found equal up to 0.82 GeV and substantially different at higher energies. The results are compared with recent partial-wave analyses.