D–D Fusion Neutron Emission and Plasma Dynamics in 3.1-kJ Plasma Focus Operating With O2 and D2+Ar Gas Mixtures

A total of 474 electric discharges were performed in the 3.1-kJ plasma focus device of Mather type (called PFZ-200 and located at CTU in Prague) operating with O
2
and (100%-x)02+xAr gas mixtures (x is the percentage of argon mass to the total mass of the mixture). The experiments were characterized by constant initial mass and deuterium pressure (340 Pa or 280 Pa) in the experimental chamber of PFZ-200. For the deuterium pressure equal to 340 Pa, the following argon mass fractions (x) were used:
$0.9(\pm 0.5)\%$
(0.3 Pa),
$2.8 (\pm0.7)\%$
(1.0 Pa), and
$10.4(\pm 0.6)\%$
(4.0 Pa). Moreover, for the deuterium pressure equal to 280 Pa, the following argon mass fractions (x) were used:
$1.1 (\pm 0.6)\%$
(0.3 Pa),
$3.4(\pm 0.9)\%$
(1.0 Pa), 9.6
$(\pm 0.8$
I% (3.0 Pa), and
$17.5 (\pm$
O.7)% (6.0 Pa). Electric and magnetic probes, silver neutron activation counter, fast 4-frame XUV pinhole camera, 2-frame Schlieren and Wollaston laser imaging, XUV and SXR PIN photodiodes and high-speed scintillation probes were used to study plasma dynamics and radiation emission during the experiments. The results of experiments showed an increase in the total D–D fusion neutron emission yield (on average) for
$99.1\%\mathrm{D}_{2}+0.9\%\text{Ar}, 98.9\%\mathrm{D}_{2}+1.1\%\text{Ar}$
, and
$96.6\%\mathrm{D}_{2}+3.4\%\text{Ar}$
mixtures in reference to discharges in pure O
2
, Scenarios of plasma/discharge evolution were determined, and distinct modes/types of compression were observed. The existence of different compression types for different discharges is connected to the presence or absence of azimuthal filamentary-like structures. Observed changes in plasma dynamics and radiation emission during discharges in different initial pressures and gas mixtures will be presented.