Plasma foci of compact sizes and operating with low energies (from tens of joules to few hundred joules) have found application in recent years and have attracted plasma-physics scientists and engineers for research in this direction. We are presenting a low energy and miniature plasma focus which operates from a capacitor bank of 8.4 μF capacity, charged at 4.2–4.3 kV and delivering approximately 52 kA peak current at approximately 60 nH calculated circuit inductance. The total circuit inductance includes the plasma focus inductance. The reported plasma focus operates at the lowest voltage among all reported plasma foci so far. Moreover the cost of capacitor bank used for plasma focus is nearly 20 U.S. dollars making it very cheap. At low voltage operation of plasma focus, the initial breakdown mechanism becomes important for operation of plasma focus. The quartz glass tube is used as insulator and breakdown initiation is done on its surface. The total energy of the plasma focus is approximately 75 J. The plasma focus system is made compact and the switching of capacitor bank energy is done by manual operating switch. The focus is operated with hydrogen and deuterium filled at 1–2 mbar.

In this work, the formation of clusters in a supersonic jet expansion has been investigated. Clusters of argon, carbon-dioxide, nitrogen, and oxygen have been generated in the gas jet with three different types of nozzles (0.5 mm diameter, 0.8 mm diameter, and a conical nozzle with 0.8 mm diameter aperture). The mean size and density of the clusters have been measured as a function of backing pressure. Here, density of clusters refers to the density of the cluster collection. Rayleigh scattering experimental data and Mach-Zehnder interferometer data have been combined to estimate the average size and density of clusters. CO2 and Ar clusters form easily at about a backing pressure of 2 bars, while N2 and O2 clusters do not form easily. N2 and O2 begin to cluster at a backing pressure of about 18–24 bars. The mean cluster radius of Ar varies from 6.6 Å to 24 Å and the cluster radius of CO2 varies from about 8.8 Å to 35 Å as the backing pressure increases from 3 bars to 14 bars. In the same range of backing pressures, the average cluster gas density changes from 37.3 × 1015 cm−3 to 1.6 × 1015 cm−3 for Ar clusters and changes from 10.52 × 1015 cm−3 to 0.22 × 1015 cm−3 for CO2 clusters. It is assumed that the condensation into clusters is total. The mean cluster radius of N2 is smaller and varies approximately from 4.2 Å to 8.6 Å and the cluster radius of O2 varies from about 4.9 Å to 12.4 Å as the backing pressure increases in the range of 18 bars to 35 bars. In the same range of backing pressures, the average cluster density changes from 48.2 × 1016 cm−3 to 3.7 × 1016 cm−3 for N2 clusters and from 21.5 × 1016 cm−3 to 1.3 × 1016 cm−3 for O2 clusters.

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