In this paper we present an experimental work concerning the effect of gas admixture on the pinch dynamics in a Filippov type (25 kV, 288 μF) plasma focus, DENA[1]. Deuterium pressure of 0.3 - 1.5 torr and krypton admixture of 0.5% - 3% by volume, have been used as working gases. The main results have been obtained for the optimum pressure of deuterium and deuterium + krypton.
A study of the time - resolved pulsed neutron signals by the time-of-flight technique made at angles of 0 and π/2 radians, shows that the contribution of non-thermal neutron production in the quiet phase of deuterium discharges is not considerable; this is inconsistent for the Mather type plasma focus[2]. Furthermore, the addition of krypton admixture to the deuterium working gas causes a sudden increase in the non-thermal neutron production.
A survey of the experimental results presents that the propbabilities of multi-spike discharges are 75% and 20% with and without krypton admixture, respectively. The dip of negative spike in the current derivative signal for the case of krypton admixture is four times more than deuterium only gas discharges. The lifetimes of the pinches, measured in terms of current derivatives, were 60 - 180 ns with the gas admixture and 180 - 200 ns without admixture discharges. A factor, independent of working gas, has been defined to investigate the radius and lifetime of the pinch. As a result, the decreasing of this factor is correspond to the increase in the radius and duration of the pinch.
It has been concluded that there is a direct relationship between the pinch radius decreament and enhancement of the non-thermal productions in the quiet phase.

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