Approaching the edges of a surfatron microwave plasma by Thomson scattering

The radial and axial profiles of a cylindrical surfatron plasma created at intermediate pressure in argon were mapped by Thomson scattering. This technique provides accurate, non-perturbing access. The direct imaging capacity of a triple-grating spectrometer equipped with an iCCD camera allows investigating radial and axial profiles. The obtained radial ne(r) values match a Bessel function, even if the plasma column is strongly contracted. The axial profile is linear, depending on the pressure. However, the end of the plasma column shows a discontinuity.