Most of the energy needed to form the spark is provided by the work of the imploding target on the spark fuel.
In fact, at the first stage, energy of the imploding plasma is concentrated in the kinetic energy of the shell.
One can imagine that the thickness of the imploding "sheath" may control the final pinch dimension.
Thus, these instabilities limit the radius of the imploding shell to several times its thickness.
The middle term can be identified as the internal energy continuously created by shock heating in the accreting-mass layer at the imploding magnetic piston.
In the last scheme, the pulsed current is carried in a large diameter preformed liner, imploding onto a small diameter coaxial target.
Owing to the fast imploding phase, it is not necessary to make the fast discharge tube as thin as the slow discharge one.
These instabilities degrade the symmetrical performance of the imploding shell.
