The propagation of linear and nonlinear dust ion acoustic waves (DIAWs) are studied in a collisionless magnetized plasma which consists of warm ions having anisotropic thermal pressure, nonthermal (energetic) electrons and static dust particles of positive and negative charge polarity. The anisotropic ion pressure is defined using double adiabatic Chew-Golberger-Low (CGL) theory. In the linear regime, the propagation properties of the two possible modes are investigated via ion pressure anisotropy, dust particle polarity and nonthermality of electrons. Using reductive method Zakharov-Kuznetsov (ZK) equation is derived for the propagation of two dimensional electrostatic dust ion acoustic solitary waves in dusty plasmas. It is found that both compressive and rarefactive solitons are formed in presence of nonthermal electrons using Cairn's distribution [R.A. Cairns, A.A. Mamun, R. Bingham, R.O. Dendy, R. Bostrom, C.M.C. Nairn and P.K. Shukla, Geophys.Res. Lett. **22**, 2709 (1995)] in the system. The ion pressure anisotropy, nonthermality of electrons and charge polarity of the dust particles have significant effects on the amplitude and width of the dust ion acoustic solitary waves in such anisotropic nonthermal magnetized dusty plasmas. The numerical results are also presented for illustration. Our finding is applicable to space dusty plasma regimes having anisotropic ion pressure and nonthermal electrons. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The electric discharge generated between the electrodes of a classic spark plug could not assure a fast and total combustion of the air – hydrocarbon mixture. To be able to improve the quality of the combustion process through the ignition system improvement it is necessary to have a complete diagnostic of the discharge produced by a spark plug, from physical and chemical point of view. This work presents a comparative study of the reduced electric field and the vibrational temperature for a classic spark produced in air at atmospheric pressure, as functions of pulses widths applied by the power supply. The reduced electric field was calculated by using the rotational temperature values established by a previous study, considering them as temperature plasma gas temperatures. The vibrational temperature was determined by using the N2second positive molecular emission spectra. The spark plug was supplied with trains of pulses containing one or two pulses having variable widths provided by a special power supply.

The results obtained for the vibrational temperature of nitrogen molecules are close to these obtained for the rotational temperature calculated by using a spectroscopic diagnostic method based on the OH UV molecular band spectra (between 2000 and 3500 K). The electron temperature values, imposed by the reduced electric field (up to 2000 Td), are superior to 10000 K. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of non-equidistant grids on momentum conservation is studied for simple test cases of an electrostatic 1D PIC code. The aim is to reduce the errors in energy and momentum conservation. Assuming an exact Poisson solver only numerical errors for the particle mover are analysed. For the standard electric field calculation using a central-difference scheme, artificial electric fields at the particle position are generated in the case when the particle is situated next to a cell size change. This is sufficient to destroy momentum conservation. A modified electric field calculation scheme is derived to reduce this error. Independent of the calculation scheme additional fake forces in a two-particle system are found which result in an error in the total kinetic energy of the system. This contribution is shown to be negligible for many particle systems. To test the accuracy of the two electric field calculation schemes numerical tests are done to compare with an equidistant grid set-up. All tests show an improved momentum conservation and total kinetic energy for the modified calculation scheme of the electric field. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Potential formation in front of an electrode that has the potential which is close to the plasma potential is studied by particle-in-cell (PIC) simulations. The code BIT1 [D. Tskhakaya, R. Schneider, J. Comp. Phys., **225**, 829 (2007)] is used for this purpose. It is shown that this code is very appropriate for our analysis because of its ability to create charged particles by uniform volume production in the entire system and to maintain in the same time the Maxwellian electron velocity distribution function prescribed in the input file. It turns out that some modifications of the code are necessary in order to achieve small sheath potential drops and to detect the cutoff in the electron velocity distribution function. The modifications of the code are described. The small sheath potential drop is achieved by introducing a finite reflectivity of the electrons at the left electrode, while the expected cutoffs of the electron velocity distribution function are found by tracking the reflected electrons as separate particle species. The simulation results are compared to the theoretical model of Jelić [N. Jelić, Phys. Plasmas, **18**, 113504 (2011)]. The matching is very good and this is a sign that the PIC simulations are very appropriate tool for the analysis of this type of problems. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In theory of the spectral line shapes, the conventional scheme use two approximations for the local electric field (microfield) due to all charged particles of the plasma. The quasi-static approximations for the ions and the impact approximation for the electrons. The first approximation consists to say that the electric field is constant during the characteristic time. In this work we shall transpose the idea of the first approximation, to the angular velocity of the microfield whereas its strength is kept constant and equal to its mean value. We shall use the Holtsmark approach and the independent particles model (due to Margeneau and Lewis) to compute the static distribution function of the angular velocity of the microfield. In the first approach (Holtsmark), the distribution shows a Lorentzian behavior, whereas the second approach (Margenau and Lewis) shows a gaussian behavior. Subsequently, we have applied the obtained static distribution to show the effect on the broadening of Lyman-alpha line for a plasma composed of *He*^{+} ions. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The resonant interaction between three waves propagating perpendicularly to an external magnetic field in a plasma is considered. We present the explicit expressions for the three wave coupling coefficients of a warm multi-component plasma. The results of previous work on the generation of THz radiation by laser plasma interaction are significantly improved.

Plasma chemical reactions in CH4/Ar and C_{2}H_{m}/Ar (*m* = 2*,* 4*,* 6) gas mixtures in a dielectric barrier discharge at medium pressure (300 mbar) have been investigated. From mass spectrometry the production of H_{2} and formation of larger hydrocarbons such as C_{n}H_{m} with up to *n* = 12 is inferred. Hydrogen release is most pronounced for CH_{4} and C_{2}H_{6} gas mixtures. Fourier Transform InfraRed (FTIR) spectroscopy reveals the formation of substituted alkane (sp^{3}), alkene (sp^{2}), and alkyne (sp) groups from the individual gases which are used in this work. Abundant formation of acetylene occurs from C_{2}H_{4} and to a lesser extent from C_{2}H_{6} and CH_{4} precursor gases. The main reaction pathway of acetylene leads to the formation of large molecules via C_{4}H_{2} and, eventually, to nano-size particles. The experimental results are in reasonable agreement with simulations which predict a pronounced electron temperature and gas pressure dependency. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Energy spectra of ions of various charged states at different cross-section of a titanium plasma flow produced with a dc vacuum arc were studied. It was established that ions with different charges states were spatially separated during their travel through a plasma transport system based on a curved magnetic field. Ions with greater charge states were concentrated in the inner part of the curved plasma flow, i.e. closer to the centre of curvature of the field lines, so that the average charge state of ions in this area was higher than that at the outer part of the flow. A computer simulation of guiding a multi-species plasma flow by a curved magnetic field qualitatively agreed with the experimental data. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A parallel Particle in Cell/Monte Carlo Collision (PIC/MCC) numerical code for glow discharge plasma simulations is developed and verified. This method is based on simultaneous solution of the Lorentz equations of motion of super particles, coupled with the Poisson's equation for electric field. Collisions between the particles are modelled by the Monte Carlo method. Proper choice of particle weighting is critically important in order to perform adequate and efficient PIC simulations of plasma. Herein, effects of particle weighting on the simulations of capacitive radio-frequency argon plasma discharges are studied in details. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

14 pin probe head with free-standing proud pins in three radially staggered planes. The pins are separated poloidally by 5.4 mm and radially by 4 mm. The operation regime of the tips is indicated. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports on probe measurements of the electron energy distribution function and plasma potential in the divertor region of the COMPASS tokamak during D-shaped plasmas. The probe data have been processed using the novel first-derivative technique. A comparison with the results obtained by processing the same data with the classical probe technique, which assumes Maxwellian electron energy distribution functions is presented and discussed. In the vicinity of the inner and outer strike points of the divertor the electron energy distribution function can be approximated by a bi-Maxwellian, with a dominating low-energy electron population (4-7 eV) and a minority of higher energy electrons (12-25 eV). In the private flux region between the two strike points the electron energy distribution function is found to be Maxwellian with temperatures in the range of 7-10 eV. The comparative analysis using both techniques has allowed a better insight into the underlying physical processes at the divertor region of the COMPASS tokamak. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In the tokamak ASDEX Upgrade the influence of a non-axisymmetric *n* = 2 error field on the turbulence in the far scrape-off layer of a low density L-mode discharge has been studied. There is no density pump-out with the non-axisymmetric perturbation but an increase of the scrape-off layer density at the outer midplane. While the relative ion saturation current fluctuation level in the far scrape-off layer is decreasing, the skewness rises and especially the excess kurtosis grows by a factor of 1.5–3. The frequency of intermittent events (blobs) is increasing by 50 %. Also the poloidal velocity grows with the magnetic perturbation while the typical turbulent structure size becomes smaller by a factor 5–10 about 20–25 mm outside the separatrix. The local spectral density has been calculated from a two-point measurement of the ion saturation current. It is used to derive a dispersion relation. Two poloidal propagation velocities depending on the wave number have been found. One is an upper limit for the bulk *E × B* velocity and the second one the lower limit of the phase velocity. There is a significant contribution of the phase velocity to the propagation speed in the far scrape-off layer. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The First derivative probe technique for a correct evaluation of the plasma potential in the case of non-Maxwellian EEDF is presented and used to process experimental data from COMPASS tokamak. Results obtained from classical and first derivative techniques are compared and discussed. The first derivative probe technique provides values for the plasma potential in the scrape-off layer of tokamak plasmas with an accuracy of about ±10%. Classical probe technique can provide values of the plasma potential only, if the electron and ion temperatures are known as well as the coefficient of secondary electron emission. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A reciprocating probe head with six pins was used for localized measurements of electric fields and densities in the scrape-off layer (SOL) of ASDEX Upgrade (AUG) up to the edge shear layer (SL) near the Last Closed Flux Surface (LCFS). The edge SL is characterized by a strong sudden change in the poloidal velocity *vθ* close to the separatrix. The probes were used to determine this velocity by different methods which are critically compared to each other concerning their reliability. By the first method the poloidal velocity was deduced from the radial electric field *E _{r}* measured by two radially staggered probe pins, with

Experimental investigations of the plasma potential by means of a ball-pen probe and self-emitting Langmuir probe technique were performed on the tokamaks COMPASS and ASDEX Upgrade. A spontaneous transition between the cold and self-emitting Langmuir probe has been observed during the deep reciprocation in the vicinity or even inside the last closed flux surface (LCFS) of both tokamaks. These measurements of the plasma potential allow us to compare two independent probe techniques based on heating and non-heating processes. The observed different conditions of the spontaneous transition can be ascribed to different physical mechanisms. Nevertheless, the comparison of the power spectra of ball-pen probe and self-emitting Langmuir probe indicates very good agreement in all measurements and therefore these two probe techniques are interchangeable. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Measurement and control of divertor heat flux are a crucial issue for realization of fusion burning plasma. However, time-dependent heat flux is often difficult to be estimated experimentally, because thermal diffusion process in thermal probe tips takes time longer than the discharge duration of present experiments. A new reconstruction method for time dependent heat flux from the measurement of the thermal probe tip temperature is proposed in this paper. The heat flux of the Large Helical Device divertor leg was analyzed by the proposed method as the function of the time for the first time. This indicates that heat flux measurement with thermal probes would become a monitoring tools even for the future fusion devices. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In the present contribution, experimental and numerical simulation results are presented on the influence of the electrons reflected by the insulator shaft of the probe on both probe characteristic and local disturbance produced by these electrons within relatively strong magnetized plasmas. The reduction mechanism of the electron component of the probe characteristic with increasing the magnetic field strength can also be investigated by the new experimental setup.

Both electron current intensity increase and diminish of the negative slope region of the current-voltage characteristics are explained based on the electrons kinetics near the probe. Essentially, the explanation is based on the idea that slow electrons with kinetic energy lower than *eV _{f}*, where

Plasmas evolve under sharp conditions such as localized currents, charge separation and absorption or emission of particles. The plasma-wall interaction is one of these singularities. Numerical methods based upon differences usually fail under these abrupt boundary conditions leading to new spurious noise and singularities of numerical nature. Here, we extend the path-sum integral numerical method to account for abrupt boundary conditions in plasma drift-diffusion equations. The boundary-path-integral solution also shows the advantages of the smoothing affects of the diffusive short-time propagators for unbounded domains. The proposed scheme is free of artificial numerical smoothing functions to mask sharp behaviours. This stable, robust and grid-free algorithm is applied to test cases of plasma-wall interaction with an advancing scheme that simultaneously copes with disparate electron and ion time scales. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the influence of plasma-neutral collisions in the sheath in front of a probe electrode based on the results of particle-in-cell simulations. The simulated space potential profiles indicate that the sheath potential drops with increasing neutral gas pressure *P _{n}*. According to collisionless theory, the apparent electron temperature is three times higher than that corresponding to the collisionless case at

We report on a development of an alternative method of HED plasma diagnostics using the ideas of the method of moments [I.M. Tkachenko, J. Ortner, and J. Alcober, J. de Physique IV **10**, 195 (2000)]. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An electric solar sail (e-sail) is a promising propellantless propulsion concept for the exploration of the Solar System. An e-sail consists of an array of bare conductive tethers at very high positive/negative bias, capable of extracting solar-wind momentum by Coulomb deflection of protons. The present work focuses on the positivebias case with a potential profile that must be correctly modeled. Ion scattering does occur at some point of the profile and the resulting thrust is determined; that thrust scales slower with distance to the Sun, than it was previously suggested in the literature. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)