# Introduction

The density of a plasma cannot be measured directly, but its absorbance of a laser beam can be obtained experimentally. The absorbance along a straight line is proportional to the corresponding line integral over the density . Assuming a radial symmetric plasma column (see Fig. 1), absorbance and density are related via the Abel transformation:

 (1)

which can be rewritten as linear integral equation of the form:

 with (2)

Due to the singularity of the integral kernel at , the inversion of (2) turns out to be an ill-conditioned problem which we will tackle by applying the Maximum Entropy-Method.

Danilo Neuber 2003-10-03