The High Intensity Two Axis Neutron Diffractometer D20 First Results

D20 has a high flux on the sample and a large position sensitive detector (PSD) with a detection zone of 160 degrees in 2 theta (1600 microstrip detection cells). D20 is equipped with two monochromators of fixed vertical focalisation providing wavelengths of 0.9, 1.3 and 2.4 Angstrom at take-off angles of 28 and 42 degrees. The divergence before monochromator may be 10' or 27'. The large stationary PSD and the high flux at sample, the choice of wavelength and resolution makes D20 a Versatile instrument. It provides scientifically and experimentally a broad range of applications from numerous successive short acquisitions to follow the evolution of a sample up to long acquisitions to obtain a very high precision in intensity. Among the experiments that have been performed since the commissioning of the instrument, several examples are showing the different fields studied on D20: Thermodiffractometry: phase transitions (crystallisation, amorphisation, hydration of cement). Magnetism: determination of magnetic structures (intermetallic compounds R2T3Xg). Kinetics: dynamic studies in solid state chemistry (cement precursors, batteries). Multi-stroboscopy: dynamic studies on particle orientation in flowing systems. Texture: quantitative texture analysis of composite materials (SIC whiskers in beta-Si3N4). Very small samples: magnetic order or preferred orientation of tiny samples. Disordered systems: variation of the structure factors with density (mercury, 1 and 2000 bars). Physisorption: study of solid layers absorbed from liquid alcanes on graphite.