Information from probe characteristics in negative ion containing plasma

Abstract

The effect of negative ions on the probe characteristic is studied theoretically. The reliability of results obtained from probe characteristics is analyzed. The methods of determining the energy distribution functions of charged particles is analyzed as an inverse ill-posed problem. A Tikhonov's regularization procedure for detection of negative ions from a probe characteristic is described. This method parallels the Dryvestein method with the key difference stemming from the fact that experimental determination of the second derivative of the probe characteristic is avoided. For a small ratio of negative ion to electron densities and quite plasma, the energy distribution, temperature and density for the electrons and negative ions can be estimated only from the probe characteristic and the errors in the experimental data. The model functions, simulating experimental energy distribution for the electrons and negative ions, are introduced to test applicability limitations of the method. In addition, the comparative advantages of the method are presented as well. (C) 1998 American Institute of Physics. [S0021-8979(98)05320-1].