[en] Disturbed Bilateral Relations offer a way of categorizing plasma processes by their deviation from equilibrium. This method can be used to create a simple plasma model that solves key plasma parameters, namely the electron temperature, electron density and heavy particle temperature. An implementation of this method is presented, and the results validated against a detailed plasma simulation, for a wide range of parameters

[en] Slow pulsed capillary discharges are currently under investigation for use as plasma channel waveguides in laser-wakefield acceleration and XUV generation. In this work, a parameter study is performed on this device using a combination of two models, namely a non-local thermal equilibrium (non-LTE) plasma model and a wall temperature model that is coupled to it. This model has been validated against experiments. In the present study, two parameters are varied, the initial density and the channel radius. These parameters have a strong influence on the guiding properties. The results of this parameter study can be summarized in a single, empiric formula describing the matched spot size as a function of the initial density and the channel radius. This formula is expected to give a good prediction of the matched spot size, provided that no wall ablation occurs, diffusion is limited and that the current pulse is sufficient in amplitude and duration for formation of a well-ionized, stable plasma. This has been verified for the parameter range studied here

[en] In this work, we study a cascaded arc in argon that is used as a broadband light source for spectroscopic applications. In this arc, the arc channel is geometrically constricted. A numerical model is used to investigate the plasma parameters and light output of the arc. It is found that constricting leads to a higher electron density in the constricted area, which strongly enhances the local broadband emission of the plasma. A parameter study, in which the current is varied, is performed. The simulated arc voltages are compared with measured arc voltages, and excellent agreement is found. Furthermore, it is found that the emissivity increases strongly for increasing current, making the current a suitable control parameter to control the light output of the arc

[en] Transverse interferometric measurements are presented of the plasma channel formed in a hydrogen-filled capillary discharge waveguide recently used to generate 1 GeV electrons in a laser-driven plasma accelerator for the first time. The measurements were found to be in good agreement with nonlocal thermal equilibrium simulations, but showed significant differences with the results of a quasistatic model developed by Bobrova et al. [Phys. Rev. E. 65, 016407 (2001)]. The measurements are used to determine scaling laws for the axial electron density and matched spot size of the plasma channel, enabling optimization of the channel to specific applications

[en] Slow pulsed capillary discharges in round capillaries are currently under investigation for use as plasma channel laser waveguides in laser-wakefield acceleration, x-ray lasers, and higher-harmonic generation. In this study, a capillary discharge with a square cross section is presented. The electron density, which determines the laser guiding properties, can be measured by means of transverse interferometry in this device. Using a numerical model of the plasma and the capillary wall, an analysis of the discharge is made. The results predict that the square channel is capable of guiding circular laser pulses. The guiding properties are quite similar to those of a round channel with nearly the same diameter as the channel width. This suggests the results obtained by measuring the square capillary discharge are applicable for round channels as well. It was found that the wall heating was inhomogeneous, which makes the wall more susceptible to ablation. The heating of the wall changes the transverse optical pathlength in the interferometry experiments

[en] Slow pulsed capillary discharges are under investigation for use as plasma channel waveguides in laser-wakefield acceleration and high-harmonics generation. The channel radius has a strong influence on the plasma and guiding properties. Hence, it is expected that the guiding properties can be manipulated by locally modifying the radius. This presumption has been investigated by means of a numerical simulation of a channel with a periodically modulated radius. The simulation revealed a strongly nonlinear response of the plasma and wall properties to the modulation. However, no modulation of the laser guiding properties is observed

[en] A hydrogen plasma flame produced by an axial injection torch powered at the microwave frequency of 2.45 GHz is studied using the method of disturbed Bilateral Relations (dBR). The application of this method which relates the influence of equilibrium disturbing, as produced by transport, to equilibrium restoring processes, reveals that the most dominant excitation balance is the Excitation Saturation Balance. Moreover, a global discharge model leads to an electron density of n_e = 4.10²⁰m^-3 and an electron temperature of T_e 0.86 eV. The gas temperature was estimated to be T_h = 0.3 eV. The values of n_e and T_e were found to be in good agreement with the value obtained with the modified Boltzmann-plot and the crossing method of Stark broadening. The dBR method points out that the first level in partial local Saha equilibrium will be the level with principal quantum number p = 10 which is in fair agreement with experimental results