Effective recombination coefficients in argon surface-wave-produced plasma

The authors present experimental data for the effective recombination coefficient in a pulsed surface-wave-produced plasma. To determine these data they studied the relaxation of electron density to equilibrium. A 2.45 GHz Surfatron was used in order to couple the HF energy, and three different Pyrex cylindrical tubes of internal radius a=1.5, 2.5 and 4.5 mm, with a corresponding external radius b=a+1.5, were employed. The gas used in the discharge was argon, in the 0.5-12 Torr pressure range. They obtained the total losses by ambipolar diffusion and recombination, divided by pressure, as a function of the quotient between the effective surface wave electric field and gas pressure. At the lower end of the pa range diffusion losses dominate but recombination becomes more important for higher values of pa.