  We present a new kind of generator of internal waves which has been designed
for three purposes. First, the oscillating boundary conditions force the fluid
particles to travel in the preferred direction of the wave ray, hence reducing
the mixing due to forcing. Secondly, only one ray tube is produced so that all
of the energy is in the beam of interest. Thirdly, temporal and spatial
frequency studies emphasize the high quality for temporal and spatial
monochromaticity of the emitted beam. The greatest strength of this technique
is therefore the ability to produce a large monochromatic and unidirectional
beam.
