Table of contents

The International Conferences on Research and Applications of Plasmas (PLASMA) have been organized every two years since 1993. The scope of the PLASMA conference series, which idea was originally to facilitate the exchange of knowledge and to spread the collaboration between the scientists and engineers from the Eastern European Countries, covers most of issues of broadly understood plasma physics and technology.

PLASMA-2017, organized by the Institute of Plasma Physics and Laser Microfusion (IPPLM), took place from 18th September to the 22nd September 2017 at the Central Agriculture Library in Warsaw, Poland. The conference covered scientific areas like:

I. Elementary processes and general plasma physics

II. Plasmas in tokamaks and stellarators (MCF)

III. Plasmas generated by laser beams and Inertial Confinement Fusion (ICF)

IV. Plasma produced by Z-pinch and Plasma-Focus discharges

V. Low-temperature and dusty plasma

VI. Space plasmas and laboratory astrophysics

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

The recent development of laser technology has resulted in the construction of short-pulse lasers capable of generating fs light pulses with PW powers and intensities exceeding 10²¹ W/cm², and has laid the basis for the multi-PW lasers, just being built in Europe, that will produce fs pulses of ultra-relativistic intensities ~ 10²³ – 10²⁴ W/cm². The interaction of such an intense laser pulse with a dense target can result in the generation of collimated beams of ions of multi-MeV to GeV energies of sub-ps time durations and of extremely high beam intensities and ion fluencies, barely attainable with conventional RF-driven accelerators. Ion beams with such unique features have the potential for application in various fields of scientific research as well as in medical and technological developments. This paper provides a brief review of state-of-the art in laser-driven ion acceleration, with a focus on basic ion acceleration mechanisms and the production of ultra-intense ion beams. The challenges facing laser-driven ion acceleration studies, in particular those connected with potential applications of laser-accelerated ion beams, are also discussed.

The paper concerns measurements of runaway electrons (REs) which are generated during discharges in tokamaks. The control of REs is an important task in experimental studies within the ITER-physics program. The NCBJ team proposed to study REs by means of Cherenkov-type detectors several years ago. The Cherenkov radiation, induced by REs in appropriate radiators, makes it possible to identify fast electron beams and to determine their spatial- and temporal-characteristics. The results of recent experimental studies of REs, performed in two tokamaks - COMPASS in Prague and FTU in Frascati, are summarized and discussed in this paper. Examples of the electron-induced signals, as recorded at different experimental conditions and scenarios, are presented. Measurements performed with a three-channel Cherenkov-probe in COMPASS showed that the first fast electron peaks can be observed already during the current ramp-up phase. A strong dependence of RE-signals on the radial position of the Cherenkov probe was observed. The most distinct electron peaks were recorded during the plasma disruption. The Cherenkov signals confirmed the appearance of post-disruptive RE beams in circular-plasma discharges with massive Ar–puffing. During experiments at FTU a clear correlation between the Cherenkov detector signals and the rotation of magnetic islands was identified.

The paper reports on soft x-ray emission from high-current discharges in PF-1000U facility operated at 170 kJ. The discharges at static conditions were performed with pure deuterium (D2) and a mixture of D₂ and neon (Ne). In shots with the gas-puffing 1 cm³ of D₂ or a (D₂+Ne) mixture was injected 2 ms before the discharge initiation. Time-integrated x-ray images from a Be-filtered pinhole camera showed that the pinch microstructure depends strongly on gas conditions. In shots with the D₂-, (D₂+Ne)- or He-puffing distinct "filaments" and "hot-spots" were observed. Time-resolved x-ray pulses were recorded with 4 filtered PIN-diodes which recorded signals from 2 regions of 3 cm in diameter (at z = 3 cm and 6 cm from the anode). From a ratio of x-ray pulses, measured behind different filters, it was estimated that at the static D₂-filling electron temperatures (T_e ) were from 90 eV to 200 eV. At the D₂-filling and -puffing additional x-ray spikes were emitted from "hot-spots" with T_e twice higher. In shots at the (D₂+10%Ne)-filling T_e was 4 keV. In shots with the (D₂+Ne)-mixture puffing intense "hot-spots" were formed, and T_e reached 2.2-7.5 keV. At the same conditions "filaments" were reproducible macroscopically, but "hot-spots" were irreproducible.

Influence of powerful plasma impacts on several materials used for the construction of energy systems, i.e. different grades of steels as well as tungsten coatings, has been discussed. Irradiations of these materials with hydrogen and helium plasma streams have been performed in several high-current-pulse and quasi-stationary plasma accelerators which provided the variation of a power load upon the exposed surface as well as changes of the particle flux in wide ranges: the energy flux density in the range of 1-25 MJ/m², particle flux - up to 10²⁶-10²⁹ ion/m²s, the plasma stream velocity - up to about 500 km/s, and the pulse duration in the range of 1-250 μs.

A response of the investigated materials to extreme plasma loads, which are relevant to transient events in fusion reactors, is briefly discussed. It is demonstrated that a broad combination of mechanisms of powerful plasma interactions with various materials includes not only a surface damage caused by different erosion mechanisms, but under certain conditions it may also result in a significant improvement of material properties in the near-surface surface layer of several tens-μm in thickness. Some improvement of the structure and substructure of such a layer may be caused by the high-speed quenching, the shock wave formation and material alloying with plasma- and coating-species. The creation of unique surface structures and a considerable improvement of physical and mechanical properties of different materials can be achieved by the pulsed plasma alloying, i.e. pre-deposited coating modifications and mixing caused by the impacting plasma streams.

Results are reported of an experiment performed at the Eclipse laser facility in CELIA, Bordeaux, on the generation of strong electromagnetic pulses. Measurements were performed of the target neutralization current, the total target charge and the tangential component of the magnetic field for the laser energies ranging from 45 mJ to 92 mJ with the pulse duration approximately 40 fs, and for the pulse durations ranging from 39 fs to 1000 fs, with the laser energy approximately 90 mJ. It was found that the values obtained for thick (mm scale) Cu targets are visibly higher than values reported in previous experiments, which is argued to be a manifestation of a strong dependence of the target electric polarization process on the laser contrast and hence on the amount of preplasma. It was also found that values obtained for thin (μm scale) Al foils were visibly higher than values for thick Cu targets, especially for pulse durations longer than 100 fs. The correlations between the total target charge versus the maximum value of the target neutralization current, and the maximum value of the tangential component of the magnetic field versus the total target charge were analysed. They were found to be in very good agreement with correlations seen in data from previous experiments, which provides a good consistency check on our experimental procedures.

In the reported studies the attention was focused on an analysis of optical spectra of the visible radiation emitted from stainless steel (SS) samples exposed to intense pulses from a ND:YAG laser or pulsed plasma streams produced by a Rod Plasma Injector (RPI) IBIS. Operational regimes of the RPI IBIS facility, which can generate intense deuterium-plasma streams, were studied and corresponding energy fluxes were determined. Optical emission spectra from the laser- or plasma-irradiated SS samples were recorded at different energies supplied. It was proved that intensities of the emitted spectral lines of Fe I and Cr I species depend strongly on deuterium-plasma energy deposited upon the irradiated target.

Establishment of fueling system is one of the critical issues for the future fusion reactors. Fueling experiment supersonic molecular beam injection (SMBI) have been carried out in the central-cell of GAMMA 10. In GAMMA 10, electron cyclotron resonance heating (ECRH) is used at plug/barrier-cells for the formation of the axial confining potential. Recently, ECRH was applied during SMBI to plug the loss particles and increased the plasma density in the central-cell compared to without ECRH. This result suggests that the particles are confined during SMBI due to the injection of ECRH at plug/barrier-cells in GAMMA 10.

In this work, the ceramic micro- and nanofibers were formed using atmospheric pressure thermal plasma reactor. The catalytic (copper, titanium) particles and their mixtures were deposited on the surface of zeolite fibers during their formation. The prepared catalytic fibers were analyzed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), BET (Brunauer–Emmett–Teller) surface area measurements and Energy-dispersive X-ray spectroscopy (EDS). The SEM analysis showed that the obtained fiber diameters are in the range from 10 μm to few hundred nanometers. Some of the catalytic particles were deposited without changes and some were melted or burst. The XRD analysis showed that the zeolite fiber without the catalytic particles is amorphous as there are no crystal phase peaks. After the deposition of catalytic particles the peaks of the catalytic metals and their oxides appear. The BET method showed that the surface area of the catalytic fiber is 13-18 m2/g. The EDS analysis showed that the quantity of catalytic particles in the catalytic fiber is 7-18 %.

In this contribution we present OES measurements in the JET tokamak of the deuterated NH (ND) radical and the correlation between results of those experiments and measurement of ammonia production. The observation region covers most of the divertor and its outer throat. Measurements are performed in different magnetic configurations. The results include temporal and spatial dependence of the molecular emission intensity and study of the emission band shape (vibrational and rotational temperatures) during different JET pulses, with or without nitrogen seeding. Results are a step towards the understanding of nitrogen-containing molecule creation and destruction in the divertor plasma.

This paper presents results of two-dimensional particle-in-cell simulations of proton acceleration at the interactions of a 130 fs, linearly polarized laser pulse of intensity from the range 10²¹ –10²³ W/cm², predicted for the ELI (Extreme Light Infrastructure) lasers, with thin hydrocarbon (CH) or hydride (ErH3) targets. It is shown that for the targets of the areal density σ > 0.1 mg/cm² and laser intensities below 10²² W/cm² a higher efficiency of proton acceleration is achieved for hydride targets. However for the highest, ultra-relativistic laser intensities (~ 10²³ W/cm²) considerably higher proton energies and proton beam intensities are achieved for thin (σ ≤ 0.1 mg/cm²) CH targets. In this case, at short distances from the irradiated CH target (< 50 um), the generated proton pulses are very short (< 20 fs), and the proton beam intensities and the proton current densities reach extremely high values, > 10²¹ W/cm² and > 10¹² A/cm², respectively, which are much higher than those attainable in conventional accelerators. Such proton beams can open the door for new areas of research in nuclear physics and high energy-density physics as well as can be useful for materials research.

Elastic deformation in transparent mediums is usually studied by the photoelasticity method. For opaque mediums the method of film coating and strain gauge method are used. After the external load was removed, the interference pattern corresponding to elastic deformation of the material disappears. It is found that the elastic deformation state of the thin glass plate under the action of concentrated load can be fixed during the deposition of a thin metal film. Deposition of thin copper films was carried out by passing of plasma through the copper tube installed inside the Plasma Focus installation. After removing of the load, interference pattern on the glass plates was observed in the form of Newton's rings and isogers in non-monochromatic light on the CCD scanners which uses uorescent lamps with cold cathode. It is supposed that the copper film fixes the relief of the surface of the glass plate at the time of deformation and saves it when the load is removed. In the case of a concentrated load, this relief has the shape of a thin lens of large radius. For this reason, the interference of coherent light rays in a thin air gap between the glass of the scanners atbed and the lens surface has the shape of Newton's rings. In this case, when scanning the back side of the plate, isogyres are observed. The presented method can be used in the analysis of the mechanical stress in a various optical elements.

The generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. The dependence of parameters of the shock generated in the target by the impact of a gold projectile on the impacted target material and the laser driver energy is examined. It is found that both in case of low-density (CH, Al) and high-density (Au, Cu) solid targets the shock pressures in the sub-Gbar range can be produced in the LICPA-driven collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10 – 20 %, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.