Lidar Technology Based on Fiber System and its Application

The sodium atom existed in the metal layer of the earth’s atmosphere has a high atomic number density and a large scattering cross section. Sodium layer can act as a good tracer for atmospheric detection in the middle and lower-thermosphere (MLT) region. The sodium fluorescence lidar uses ultrashort pulsed laser to excite sodium atoms, which enabling simultaneous detection of wind and temperature in the middle and upper atmosphere. This paper reports on the development of sodium fluorescence laser radar in recent years, especially the integration of fiber-coupled optical switches and fiber-coupled acousto-optic frequency modulation technologies, which greatly improved the stability and reliability of lidar system and reduced the maintenance of lidar operation, laying a good foundation for the application of lidar observations under harsh environments. This technology has been applied to the sodium wind/temperature lidar in Yangbajing, Tibet and has been running stably for a long time.

Electron Backscatter Diffraction in Conservation Science: Phase Identification of Pigments in Paint Layers

Electron backscatter diffraction (EBSD) was used in Conservation Science for characterization of ancient materials collected from works of art. The results demonstrate the feasibility of EBSD analysis on heterogeneous matrices as very small samples of paint layers collected from paintings. Two reference pigments were selected from those used by artists to investigate the relationship existing between EBSD pattern quality and properties of the investigated material (i.e., average atomic number, density, and Mohs hardness). The technique was also tested to investigate the pigment phases on two real samples collected from Romanino's Santa Giustina altarpiece, an oil on wood painting dated 1514 (Civic Museum, Padova, Italy). Results show for the first time the acquisition of EBSD patterns from painting samples mounted in resin, i.e., painting cross sections, opening a new powerful tool to elucidate the pigment phases avoiding large sampling on works of arts and to further study the complex mechanisms of pigment deterioration.

A Monte Carlo Study of Radiation Trapping Effects

A Monte Carlo simulation of radiative transfer in an atomic beam is carried out to investigate the effects of radiation trapping on electron–atom collision experiments. The collisionally excited atom is represented by a simple electric dipole, for which the emission intensity distribution is well known. The spatial distribution, frequency and free path of this and the sequential dipoles were determined by a computer random generator according to the probabilities given by quantum theory. By altering the atomic number density at the target site, the pressure dependence of the observed atomic lifetime, the angular intensity distribution and polarisation of the radiation field is studied.