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Plasma focus devices represent a class of hot and dense plasma sources that serve a dual role in fundamental plasma research and practical applications. These devices allow the observation of various phenomena, including the z-pinch effect, nuclear fusion reactions, plasma filaments, bursts, shocks, jets, X-rays, neutron pulses, ions, and electron beams. In recent years, considerable efforts have been directed toward miniaturizing plasma focus devices, driven by the pursuit of both basic studies and technological advancements. In this paper, we present the design and construction of a compact, portable pulsed plasma source based on plasma focus technology, operating at the ~2–4 Joule energy range for versatile applications (PF-2J: 120 nF capacitance, 6–9 kV charging voltage, 40 nH inductance, 2.16–4.86 J stored energy, and 10–15 kA maximum current at short circuit). The components of the device, including capacitors, spark gaps, discharge chambers, and power supplies, are transportable within hand luggage. The electrical characteristics of the discharge were thoroughly characterized using voltage and current derivative monitoring techniques. A peak current of 15 kiloamperes was achieved within 110 nanoseconds in a short-circuit configuration at a 9 kV charging voltage. Plasma dynamics were captured through optical refractive diagnostics employing a pulsed Nd-YAG laser with a 170-picosecond pulse duration. Clear evidence of the z-pinch effect was observed during discharges in a deuterium atmosphere at 4 millibars and 6 kilovolts. The measured pinch length and radius were approximately 0.8 mm and less than 100 μm, respectively. Additionally, we explore the potential applications of this compact pulsed plasma source. These include its use as a plasma shock irradiation device for analyzing materials intended for the first wall of nuclear fusion reactors, its capability in material film deposition, and its utility as an educational tool in experimental plasma physics. We also show its potential as a pulsed plasma thruster for nanosatellites, showcasing the advantages of miniaturized plasma focus technology. [ABSTRACT FROM AUTHOR]

Damages induced on the tungsten surface at two different operating conditions of a kilojoule plasma focus device are studied. In one condition, the tungsten samples were exposed to axial plasma shocks that are formed after pinch disruption, and in the other condition, the pinch phenomenon was absent or weak. Melting, craters, and cracking on the surfaces were observed in both cases. In the former case, the charged particle beams and post-pinch material ejection will play a role in impacting the surface; however, in the latter case those phenomena will have small contributions because of the absence or weak formation of the pinch. A damage factor of ∼ 10 9 W m−2 s0.5 was estimated at a distance of 3 cm from the pinch exit using the method given in Akel et al. [J. Fusion Energy 35, 694–701 (2016)] and Klimov et al. [J. Nucl. Mater. 390, 721–726 (2009)] for the former case. The present work suggests that at pressures lower than the pinch-occurring pressure, only axial plasma shock effects on the targeted surface can be studied and that they can be separated from the effects produced by the charged particle beams mixed with axial plasma shocks in the case of pinch occurrence. [ABSTRACT FROM AUTHOR]

X-ray pulses (full width at half maximum ∼ 90 ns, dose rate ∼ 107 Gy s−1) were used to irradiate the monolayer of peripheral blood mononucleated cells using the PF-2kJ kilojoule plasma focus device. Four different exposure conditions were evaluated using 5, 10, 20, and 40 pulses, with the mean dose measured by TLD-100 being 0.12 ± 0.02 mGy, 0.14 ± 0.03 mGy, 0.22 ± 0.06 mGy, and 0.47 ± 0.09 mGy, respectively. Cytogenetic analysis showed an increase in all types of chromosomal aberrations following exposure to x-ray pulses. The distribution of dicentrics and centric rings was overdispersed after 5, 10, 20, and 40 pulses. Additionally, after 20 and 40 pulses, the presence of tricentric chromosomes is detected. Chromosome aberration frequencies found in this study were always higher than the estimated frequencies of chromosome aberrations using published dose–effect curves for conventional radiation sources. The overdispersion observed, the elevated maximum relative biological effectiveness (RBEM) and the presence of tricentric chromosomes at the relatively low doses of exposure (<0.5 Gy) seem to indicate that low doses of pulsed x-rays of low energy show similar biological effects as those observed for high-LET radiation. X-ray pulses emitted by PF-2kJ were found to be more efficient in inducing chromosome aberrations, even more than α particles. [ABSTRACT FROM AUTHOR]

In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray source to study the effects of pulsed radiation in cancer cells. Low dose hyper-radiosensitivity (LDHRS) effects have been explored in various cancer cell lines using conventional x-ray irradiation. To the best of our knowledge, the LDHRS effects have not yet been explored using pulsed x-rays. Cell death was evaluated in human colorectal (DLD-1 and HCT-116) and breast (MCF-7) cancer cell lines (monolayer cell cultures) irradiated with 10 (∼0.24 Gy), 20 (0.61 Gy), and 40 (∼1.1 Gy) pulses (FWHM ∼ 90 ns, dose rate ∼107 Gy/min with a dose of 0.025 Gy per pulse). The LDHRS cell death effect in the DLD-1 cell line irradiated with pulsed x-ray is three times higher than the reported for a conventional continuous x-ray source at two times higher doses. LDHRS was also observed in HCT-116 and MCF-7 cells exposed to 10 and 20 x-ray pulses, respectively, which are reported not to exhibit LDHRS when conventional continuous x-ray sources are used. Besides, a normal colorectal cell line, CCD-841-CoN, does not show a significant cell death at 10 pulses. These preliminary results suggest a selective effect of low-dose pulsed x-rays on cancer cells. The present work demonstrates the applicability of plasma focus devices for cancer research. Further possibilities in the exploration of pulsed x ray of high-dose rate and low total dose in radiotherapy research are opened. [ABSTRACT FROM AUTHOR]

In the present work, a kilo-joule plasma focus device, PF-2kJ, is used as a pulsed neutron generator. Time of flight and neutron spectroscopic measurements suggest neutron energies larger than 5 MeV in the radial and axial directions. The anisotropy in neutron emission suggested a beam-target nuclear fusion mechanism. A simulation tool kit Geant4 is used to interpret and verify the experimentally observed spectroscopic results of neutrons' energies. Based on the findings, it is hypothesized that the pinch and pre-pinch phases invoke suitable conditions for the D–D reaction that produces proton and tritium. The produced tritium nuclei further collide with deuterons in the pinch and post-pinch phases and produce high-energy neutrons. However, the observed high-energy neutrons could be of mixed origin of beam-target nuclear fusion mechanism and D–T fusion reactions. [ABSTRACT FROM AUTHOR]

A series of experiments carried out in a gas embedded compressional Z-pinch are presented. A dc micro discharge of 150 [micro]A between two conical sharp edged electrodes is established to produce a hollow cylindrical discharge. A few nanoseconds before the application of the main voltage, a pulsed laser is focused through the anode onto the cathode. With this preionization scheme an initial coaxial current structure is established. [H.sub.2] and [D.sub.2] at a pressure of 1/3 atm were used as a working gas. The experiments have been carried out using a pulse power generator capable of delivering current of up to I [approximately]200 kA with a dI/dt > [10.sup.12] A/s. The use of [H.sub.2] and [D.sub.2] allows the study of discharges with the same electrical properties, but with different dynamics. At early times this preionization scheme produces a coaxial double column pinch, which as current rises, coalesces into a single column becoming a gas embedded compressional Z-pinch. Diagnostics used are current and voltage monitors, single frame holographic interferometry and shadowgraphy, visible streak camera, and single frame image converter camera. Electron density, line density, pinch radius, and plasma motion are obtained from the optical diagnostics. It was found that the maximum electron density achieved on axis is greater than twice the expected value according with the filling pressure used in the discharges, which contrasts with a traditional gas embedded pinch in which the density is lower than the expected value from filling pressure. The expansion rate of the plasma column is reduced to a third of the observed value for the single channel laser initiated gas embedded pinch. These measurements agree with the existence of a central current channel in this new configuration of gas embedded pinch. The experimental results clearly show that compression is achieved with the composite preionization scheme. Index Terms - Gas discharges, plasma confinement, plasmas.

The behavior of a medium energy ([approximately]1 kJ) pulse-power-driven vacuum spark is shown to depend on the electrode material and form of the anode in otherwise similar conditions of operation. The dynamical evolution of the discharge is followed from its soft X-ray emission. The electrode materials compared are titanium and aluminum with a form of anode that is tubular or conical. The use of a tubular anode favors a more uniform sheath and a better formation of a dense Z-pinch and the ensuing hot spots are found to be at least twice as bright. The position of the brightest spots differs according to the material and the electrode shape, and is found to coincide with the shape of the sheath. The energy output is measured and the density of the plasma in the hot spots may be calculated. Index Terms - Plasma measurements, plasma pinch, X-ray measurements.

Experimental observations are presented of pre-breakdown electron beam generation in a Transient Hollow Cathode Discharge (THCD) in a vacuum. The discharge driver consists of a 400 kV maximum voltage, 25 nF Marx operated at 450 J stored energy coupled to a 120 ns, 1.5 Ohm coaxial line. Electron beams with peak currents up to tens of kA are observed when a pulsed Nd-YAG laser is used to produce a plasma at the back of the cathode surface, inside the Hollow Cathode Region (HCR). It is found that a plasma density of a few 10 to the eighteenth power cm to the -3 in a volume of a few cubic mm is required to generate intense electron beams. Optimal conditions are determined by varying the position of the laser focal spot inside the HCR and the time delay between the laser and the applied voltage. The main features of the electron beams are similar to those observed in conventional THCD at pressures in the 10-200 mtorr range.

A multiframe technique that uses Fresnel holography is described. Splitting of the initial pulse by means of 50/50 beam splitters provides two sets of eight consecutive pulses with approximately the same energy but with different angles. Each interferogram is recorded separately. The technique has been used to obtain time-resolved Fresnel holographic interferograms of transient electrical discharges, such as Z pinch. A frequency-doubled, Q-switched Nd:YAG laser (6-ns FWHM) is used. A delay between consecutive pulses of 10 ns is achieved, and it is mainly limited by the physical size of the laboratory. Interferograms obtained on a gas-embedded Z pinch are shown.