DIAGNOSTIC OF ARGON DISCHARGES THROUGH DIODE-LASERS

The measurement of the optical transmission through the plasma of a la ser beam, swept in frequency around the resonance absorption lines of atomic or ionic species, allows the direct acquisition of new informat ion on the kinetics of both neutral and ionic species, separating the contributions of the different components of the plasma. The high inte nsity of the laser allows one to obtain a good signal-to-noise ratio i n absorption spectroscopy, even in the presence of the high luminous b ackground of the plasma. This technique has been applied to several ex perimental condition. We have studied the plasma parameters of an Ar l aser tube discharge in a current densities range between 400 and 1200 A/cm(2). Both transitions leaving from the neutral 1s(5)(P-3(2)) metas table level (in the near IR) and from the metastable or long-lived 3p( 4)(P-3)3d(4)F ionic levels were observed (in the red). Information was obtained about the temperatures, the population densities in the meta stable states, and the cataphoretic speed in the discharge both for ne utral and for single-ionized species. Particular care was devoted to i nvestigate the properties of the discharge in a transverse magnetic fi eld, which is able to enhance the laser emission power.