  Some features of neutron emission from dense plasma focus suggest that the
participating deuterons have energy in the range of 105 eV and have a
directionality of toroidal motion. Theoretical models of these devices assume
that the plasma evolves through a purely irrotational flow and thus fail to
predict such solenoidal flow on the scale of the plasma dimensions. Predictions
of a relaxation theory are consistent with experimental data [S K H Auluck,
Physics of Plasmas,18, 032508 (2011)], but the assumptions upon which it is
based are not compatible with known features of these devices. There is thus no
satisfactory theoretical construct which provides the necessity for solenoidal
flow in these devices. This paper proposes such theoretical construct, namely,
the principle of constrained dynamics, and describes an experiment which
provides support for this idea. The experiment consisted of low inductance,
self-breaking spark discharge in helium at a pressure ~100 hPa between two
pointed electrodes separated by 30-50 mm distance kept inside a vacuum chamber
mounted on a low inductance high voltage capacitor. The current derivative
signal showed reproducible sharp dips at all the extrema of the damped
sinusoidal discharge. A planar diamagnetic loop centered with and perpendicular
to the discharge axis consistently showed a signal representing rate of change
of axial magnetic flux. A qualitative explanation of observed phenomena is
obtained using a simple model using the proposed principle.
