The expansion of the plasma channel generated in low pressure gas

The ambipolar expansion of the plasma channel generated in low pressure gas has been investigated As it has been shown if the magnetic field is absent and if the ion range is much more than plasma radius the channel expansion is given by it mean square radius relation R(t)=R0(1+(t/t0)²)^1/2, where t0=R0(M/2(Te0+T0))^1/2; R0 is the initial value of the mean square plasma radius: M is the ion mass; Te0,Ti0 - are the initial temperatures of the electron and ion components. If the ion range much less than the plasma radius the channel expansion is described by the relation R(t)=R0(1+(t/t1)²)^2/5, t1=0.2(3π^1/2σiNnNR0)^1/2t0, σiN - is the cross section of the ion collisions with the neutrals; nN - is the neutral density. To prevent the rapid expansion of the plasma Channel one can by imposing the longitudinal magnetic field of quite large value. For various system parameter relationships the analytic channel expansion representations as well as the conditions under which the magnetic field don´t affect the plasma expansion have been obtained.