[en] Configuration of the flight channel of an electron high-current pulse accelerator used for determining beam parameters is considered. The channel is formed by surfaces of two tubular coaxial electrodes. Electrodes are accomplished to be stepped in their axial cross section in such a manner, that a product of corresponding radii of external and internal electrodes is a constant value along the flight channel length, and a step length along an axis constitutes not less than 6 differences of the flight channel external and internal radii. Relations, allowing one to define the beam characteristic radius according to measured values of total magnetic fluxes induced by electron motion in the channel, are presented