Optimization of cw sodium laser guide star efficiency

Context: Sodium laser guide stars (LGS) are about to enter a new range of laser powers. Previous theoretical and numerical methods are inadequate for accurate computations of the return flux and hence for the design of the next-generation LGS systems. Aims: We numerically optimize the cw (continuous wave) laser format, in particular the light polarization and spectrum. Methods: Using Bloch equations, we simulate the mesospheric sodium atoms, including Doppler broadening, saturation, collisional relaxation, Larmor precession, and recoil, taking into account all 24 sodium hyperfine states and on the order of 100 velocity groups. Results: LGS return flux is limited by "three evils": Larmor precession due to the geomagnetic field, atomic recoil due to radiation pressure, and transition saturation. We study their impacts and show that the return flux can be boosted by repumping (simultaneous excitation of the sodium D2a and D2b lines with 10-20% of the laser power in the latter). Conclusions: We strongly recommend the use of circularly polarized lasers and repumping. As a rule of thumb, the bandwidth of laser radiation in MHz (at each line) should approximately equal the launched laser power in Watts divided by six, assuming a diffraction-limited spot size.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysics, AA/2009/1310

Atom-Atom and Atom-Molecular Interactions with Participation of Excited Polarized Atoms of Light Inert Gases

Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

TURBULIZATION METHOD OF FORMATION OF HIGHLY DISPERSED DROPLETS

The article critically analyzes traditional methods of forming drops of defoliants and liquid chemicals. As an object of study, a sprayer with a perforated turbulator was selected, which ensures the formation of fine droplets on a short spraying torch. The degree of crushing of the working fluid, design parameters and operating modes of the proposed sprayer are investigated. Based on theoretical studies, analytical dependencies that reveal the physical properties of the sprayed liquid are analyzed, a description of the device and the principle of operation of the sprayer equipped with a perforated turbulator is given. The above analytical dependencies allowed more purposefully improving the design of the proposed atomizer