Studying the radiation protection properties of materials via γ-ray attenuation over a wide range of γ-quanta

A setup for investigating the radiation protection properties of materials used in the manufacture of special protective clothing is described. The setup contains a collimated γ-ray source, a detector based on NaI (Tl) crystal, a movable platform for examining large areas of a material, and a data acquisition system based on a digital signal processor. A procedure for measuring the surface density of all absorbing elements in a material from the attenuation of γ-rays over a wide range of energies is described.     

Latest results from GRAAL collaboration

The GRAAL experimental set-up consists of a polarized and tagged photon beam that covers an energy range from a minimum of 600 MeV up to a maximum of 1500 MeV, of a liquid Hydrogen or Deuterium target and of the 4π Lagrange detector optimized for photon detection. It allows the study of pseudo-scalar and vector meson photoproduCtion on the nucleon in the energy range corresponding to the second and the third resonance regions. In the following, the ∑ beam asymmetries in η and π0 photoproduction on quasi-free nucleon are shown. Also single and double polarization observables in K＋A photoproduction on free proton are shown; they are important to confirm the role of new or poorly known resonances in the 1900 MeV mass region.     

Effects of boundaries on the thermodynamic properties of a Fermi gas

The discussion concerns an ideal gas bounded by an impermeable rough surface. The density of states is calculated for various limiting cases and is averaged for randomly distributed roughness. The changes in some thermodynamic parameters due to this surface are calculated for a highly degenerate Fermi gas.     

Measurement of η photoproduction on the proton from threshold to 1500 MeV

Beam asymmetry and differential cross-section for the reaction γp → ηp were measured from production threshold to 1500MeV photon laboratory energy. The two dominant neutral decay modes of the η -meson, η → 2γ and η → 3π⁰ , were analyzed. The full set of measurements is in good agreement with previously published results. Our data were compared with three models. They all fit satisfactorily the results but their respective resonance contributions are quite different. The possible photoexcitation of a narrow state N(1670) was investigated and no evidence was found.