[en] The microscopic instabilities arising from the intense plasma--electric current interaction in the Focus experiments were studied by means of the scattering of laser light. It is shown that the suprathermal fluctuations of density make their appearance with preferential directions of propagation. After a resistive phase the current is carried in the form of intense beams of particles (electrons and ions). A study of the x-ray emission spectrum generated in two units of the Mather type, with energies of 27 kJ and 340 kJ, leads to a characterization of the electron beams. In the same way, the properties of the dueteron beams are derived from the neutron emission that they generate in the two machines. Finally, an experiment with a geometry of the Filippov type is operated and the results obtained are compared with those of the Mather geometry