The correct modeling of velocity distribution functions for particles in steady-state plasmas is a central element in the study of nuclear fusion and also in the description of space plasmas. In this paper, a statistical mechanical formalism for the description of collisionless plasmas in a steady state is presented, based solely on the application of the rules of probability and not relying on the concept of entropy. Beck and Cohen's superstatistical framework [Beck and Cohen, Physica A 322, 267 (2003)] is recovered as a limiting case, and a “microscopic” definition of inverse temperature $\beta$ is given. Nonextensivity is not invoked a priori but enters the picture only through the analysis of correlations between parts of the system.

Plasma focus devices may arise as useful source to perform experiments aimed to study the effects of pulsed radiation on human cells in vitro. In the present work, a table top hundred joules plasma focus device, namely “PF-400J”, was adapted to irradiate colorectal cancer cell line, DLD-1. For pulsed x-rays, the doses (energy absorbed per unit mass, measured in Gy) were measured using thermoluminescence detectors (TLD-100 dosimeters). The neutron fluence and the average energy were used to estimate the pulsed neutron doses. Fifty pulses of x-rays (0.12 Gy) and fifty pulses of neutrons (3.5 μGy) were used to irradiate the cancer cells. Irradiation-induced DNA damage and cell death were assessed at different time points after irradiation. Cell death was observed using pulsed neutron irradiation, at ultralow doses. Our results indicate that the PF-400J can be used for in vitro assessment of the effect of pulsed radiation in cancer cell research.

Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled $520\text{−}\mu \mathrm{m}$-diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to $0.3\mathrm{GA}{\mathrm{cm}}^{-2}$ greatly increase Joule heating with respect to conventional capillary discharge $Z$ pinches, reaching unprecedented degrees of ionization for a high-$Z$ plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to ${\mathrm{Xe}}^{28+}$, while xenon impurities in hydrogen discharges reach ${\mathrm{Xe}}^{30+}$. The unique characteristics of these hot, $\sim 300:1$ length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers.

A method to determine the presence of hard X-ray emission processes from a dense plasma focus (205 J, 22 kV, 6.5 mbar H2) using Ultra High Frequency (UHF) measurements and deep learning techniques is presented. Simultaneously, the electromagnetic UHF radiation emitted from the plasma focus was measured with a Vivaldi UHF antenna, while the hard X-ray emission was measured with a scintillator-photomultiplier system. A classification algorithm based on deep learning methods, using two dimensional convolutional layers, was implemented to predict the hard X-ray signal standard deviation value using only the antenna signal measurement. Two independent datasets consisting of 999 and 1761 data pairs each, were used in the analysis. Different realizations of the training/validation process using a deep learning model, obtained overall better results in comparison to other machine learning methods like k-neighbors, decision trees, gradient boost and random forest. The results of the deep learning algorithm, and even its comparison with other machine learning methods, indicate that a relationship between the electromagnetic UHF radiation and hard X-ray emission can be established, enabling the indirect detection of hard X-ray pulses only using the UHF antenna signal. This indirect detection presents the opportunity to have a simple and low-cost diagnostic, compared to the methods currently used to characterize the pulses of X-rays emitted from plasma focus discharges.