Reply To: minimal size device for focus fusion to work?

[asymmetric_implosion]

Another interpretation of Lee’s paper on dynamic impedance is that the electrodes needs to be shaped differently in >2MA machines. In a conventional plasma focus, the electrodes are in a coaxial geometry with right circular cylinders. Higher neutron yields have been realized when the anode, the inner electrode, is made into a cone. The same can be done with the cathode rods.

The dynamic impedance is a velocity effect of the moving plasma sheet in the axial phase of the plasma focus. You cannot slow down the plasma without reducing the yield, however, you can alter the electrodes. The inductance of a coaxial geometry is given as the mu_0/(2*Pi)*ln(r_c/r_a)*z, where r_c is the cathode radius, r_a is the anode radius and z is the axial position and mu_0 is the permeability of free space. If the ratio of r_c to r_a is decreasing with axial position, the effective dynamic impedance can be reduced.