ELECTRICAL AND OPTICAL STUDIES OF THE ARGON PLASMA JET

A preliminary study has been made of the physical processes occurring in an argon plasma jet flowing at Mach 2.5. Axial electron and ion temperatures and densities were measured as functions of distance along the jet, using spectroscopic and electrical probe techniques. Estimates were also made of the degree of ionization, the electron–ion recombination coefficient, and the ambipolar diffusion coefficient. It was found that electron temperatures (~4000° K) were about twice as large as the effective rotational temperatures of N2 molecules (~1500° K) and thus of ion temperatures. Electron densities were ~1012 cm−3. The degree of ionization was ~6 × 10−4. The dominant mechanism for deionization was found to be dissociative recombination (between electrons and A2+ ions) over the first 8 cm of the jet, after which ambipolar diffusion appeared to become important.