Authors:S.S. Fatima; N.U. Rehman, Maria Younus, I. Ahmad Abstract: The atmospheric-pressure plasma needle is a promising source that can be used efficiently for different industrial applications. A radio frequency (RF) (13.56 MHz) generator was used to generate a He–O2/Ar mixture plasma. The ground-state oxygen atomic density [O] was calculated as a function of discharge parameters by “actinometry”. The Ar-I (2p1 1s2) line at 750 nm and the O-I (3P 3S) line at 844 nm were used to estimate the [O] atomic density. The rotational temperature TR of He–O2/Ar mixture was measured from the rotational levels of the “first negative system” (FNS) N2+B2Σu+,ν′X2Σg+,ν′′ by using the “Boltzmann plot”. The effect of discharge parameters on the atomic oxygen density [O] and the gas temperature was monitored. These results show that [O] density increases with RF power and O2 concentration, but decreases with the gas flow rate. Whereas the gas temperature increases with increase in the input RF power, it decreases with increase in the gas flow rate and O2 concentration in the mixture. Since the [O] atomic density contributes to plasma-based biomedical applications, the proposed optimum conditions for plasma-based decontamination of heat-sensitive materials in the present study are 0.6% oxygen, 500 sccm flow rate, and 26 W RF power. PubDate: 2017-10-16T23:20:48.262714-05: DOI: 10.1002/ctpp.201700058

Authors:Cheng Wang; Haichao Cui, Zelong Zhang, Weiluo Xia, Weidong Xia Abstract: An arc plasma can present various forms under the influence of an external magnetic field. In this study, a magnetically rotating arc plasma generator has been developed to produce three arc modes, namely rigid arc, distorted arc, and diffuse arc, which are obtained by controlling the gas flow rate. The evolution of these arc modes are experimentally studied and discussed. Results show that, as the gas flow rate increases, the arc mode is first transformed from the rigid to the distorted mode, and then to the diffuse mode. Comparisons show that the location of the arc attachment is a key factor in determining the rigid and distorted modes. The diffuse arc is observed under larger gas flow rates, but the completely diffuse arc can exist only within a narrow range of gas flow rates. Compared to the distorted arc, the diffuse arc has not only better stability but also a wider high-temperature plasma zone, which indicates that the diffuse mode may be more useful in industry. PubDate: 2017-10-11T00:14:01.876206-05: DOI: 10.1002/ctpp.201700056

Authors:N.A. Tahir; F. Burkart, R. Schmidt, A. Shutov, D. Wollmann, A.R. Piriz Abstract: This paper presents numerical simulations of the thermodynamic and hydrodynamic response of a solid copper cylindrical target that is subjected to the full impact of one future circular collider (FCC) ultra-relativistic proton beam. The target is facially irradiated so that the beam axis coincides with the cylinder axis. The simulations have been carried out employing an energy deposition code, FLUKA, and a 2D hydrodynamic code, BIG2, iteratively. The simulations show that, although the static range of a single FCC proton and its shower in solid copper is ∼1.5 m, the full beam may penetrate up to 350 m into the target as a result of hydrodynamic tunnelling. Moreover, simulations also show that a major part of the target is converted into high energy density (HED) matter, including warm dense matter (WDM) and strongly coupled plasma. PubDate: 2017-10-06T05:25:48.398015-05: DOI: 10.1002/ctpp.201700075

Authors:Ayatola Zh. Gabdulin; Tlekkabul S. Ramazanov, Zhandos A. Moldabekov Abstract: The two-dimensional (2D) Yukawa liquid with an additional screened dipole–dipole interaction is considered in connection with the 2D system of charged dust particles in complex plasmas. Particularly, the sound speed and diffusion in the case the Yukawa interaction potential dominant over the screened dipole–dipole interaction are analysed. Increase in the value of the sound speed and suppression of the super-diffusion due to the additional dipole–dipole interaction are reported. This effect is explained by the stronger inter-particle correlations induced by the additional dipole–dipole interaction. PubDate: 2017-10-06T05:20:31.609764-05: DOI: 10.1002/ctpp.201700068

Authors:C. Dietz; M. Kretschmer, B. Steinmüller, M.H. Thoma Abstract: Complex plasmas are low-temperature plasmas containing micrometer-sized particles. They are useful as models for strongly coupled many-body systems. Since the microparticles are strongly affected by gravity, microgravity experiments with complex plasmas are conducted. Here we report on recent microgravity experiments with the experimental facility PK-4 performed in parabolic flights. In particular, we discuss electrorheological and demixing experiments and the image analysis tools used. PubDate: 2017-10-06T05:15:56.0281-05:00 DOI: 10.1002/ctpp.201700055

Authors:B. Soltani; M. Habibi, H. Zakeri-khatir Abstract: Landau damping is one of the most important mechanisms for the description of wave dissipation and efficient power absorption in helicon plasma sources. Numerical analysis using the MATLAB code is carried out to determine the dispersion relation of the helicon plasma and calculate the axial wavenumber for m = 0 mode in both Trivelpiece-Gould (TG) and helicon plasma density regimes. In addition, the MATLAB code is coupled to the CST Microwave Studio (Ms) code to examine the collisionless power absorption due to Landau damping in a helicon source driven by a single-loop antenna. The effects of some parameters, such as the electron temperature (Te), the external magnetic field strength (B0), and the antenna excitation frequency (f), on the Landau damping are investigated for electron density ranging from 1 × 1016 to 1 × 1020 m–3. Our findings indicate that, for a given set of plasma parameters, Landau damping shows different behaviors on the power deposition. For instance, increasing the excitation frequency has considerable effect on the collisionless absorbed power in the range of values from 3 × 1017 to 3 × 1019 m–3 of the electron density. Also, for f = 13.56 MHz, Te = 3 eV, and B0 = 100 G, there is a specific electron density (i.e., ne = 2 × 1018 m–3) beyond which increasing the electron temperature causes a decrease in the collisionless power absorption; the opposite is true for lower plasma density (i.e., ne PubDate: 2017-09-25T04:56:57.734555-05: DOI: 10.1002/ctpp.201700020

Authors:Guang-Qing Xia; Qiu-Yun Wu, Liu-Wei Chen, Shi-Yuan Cong, Ya-Jie Han Abstract: Helicon discharge is characterized by its high ionization efficiency. In order to obtain the desired density, the configuration design of the helicon discharge tube is carried out, and the discharge characteristics are then studied to explore the correlation between the plasma parameters and the input discharge parameters. Finite-length helicon discharge theory is employed to calculate the plasma resistance Rp, and then the optimal tube length Ls, the radius rp, and the tube–antenna gap d are confirmed. The partial and energy loss mechanisms of the tube are investigated based on low-pressure discharge particle collision theory. The results show that, for a 10-cm-long Nagoya III type antenna, with a tube radius of 4 cm and length of 20 cm, the Rp versus ne curves have peak values at ne higher than 1012 cm−3 when the magnetic field intensity B0 ≥ 200 G. We find that a local minimum of Ploss exists when p0 is ∼1.5–3.0 mTorr; meanwhile, the radial confinement reduces Te and Ploss at constant p0. PubDate: 2017-09-25T04:42:09.447323-05: DOI: 10.1002/ctpp.201700050

Authors:A.E. Dubinov; I.N. Kitayev Abstract: This paper considers ion-acoustic waves in a plasma in which the ions move unidirectionally. The dispersion equation is considered and analysed as a two-dimensional problem. It is shown that the ion-acoustic waves can be in the form of backward waves (BWs). The area boundaries in the plane {kx, ky} where the BW exists are found. PubDate: 2017-09-11T09:52:04.571276-05: DOI: 10.1002/ctpp.201700040

Authors:M. Mahdavi; F. Khodadadi Azadboni Abstract: The Weibel instability plays an important role in stopping hot electrons and energy deposition mechanism in fast ignition of inertial fusion process. In this paper, the ion Weibel instability in counter propagating electron-ion plasmas is investigate. The obtained results show that the growth rate of Weibel instability will be decreased about 40% with the anisotropy velocity as vxe = 2vze = 20; the ion density ratio, b = n0i1/n0i2, and density gradient, are increasing 50 and 90% respectively. The ion streaming in density gradient of dense plasma leads to increasing the Weibel instability growth rate and its amplification through ion streaming in the large wavenumber. The maximum unstable wavenumber has been decreased with decreasing the ion beam density ratio. For fixed ion density ratio, increasing 90% of the density gradient in the near of fuel plasma corona leads to reducing growth rate and unstable wavenumber about 43 and 42% respectively. PubDate: 2017-08-22T01:21:19.729693-05: DOI: 10.1002/ctpp.201700027

Authors:H. Takahashi; A. Okamoto, S. Kitajima, T. Kobayashi, P. Boonyarittipong, T. Miura, D. Nakamura, J. Kon, T. Saikyo, Y. Tanaka, M. Goto Abstract: The influence of electron energy distribution on helium recombining plasma diagnostics is investigated using a helium collisional-radiative model. The population densities of excited helium atoms are calculated for Maxwellian and non-Maxwellian distribution plasma cases. In the case of the Maxwellian distribution plasma, the electron temperature and electron density determined by the Boltzmann plot method agree well with the input plasma parameters. On the other hand, it is indicated that the electron temperature and electron density are significantly underestimated in the bi-Maxwellian distribution plasma case, even though the density of the hot electron components is three orders smaller than that of the bulk electrons. This result indicates that in a non-Maxwellian helium recombining plasma, evaluation of the particle balance based on line emissions from excited helium atoms would be difficult because the reaction rate of atomic and molecular processes is strongly dependent on the electron temperature and density. PubDate: 2017-08-15T01:05:35.803819-05: DOI: 10.1002/ctpp.201700014

Authors:Quan Shi; Shuyu Dai, A. Kirschner, Dezhen Wang Abstract: The impact of rough surface morphology on the angular distribution of eroded impurities has been investigated with the three-dimensional (3D) rough surface code SURO and a newly developed analytic model. The property of the rough surface structure can be described by the shadow angle of the rough surface in SURO, which is defined as the ratio of the horizontal characteristic length to the initial surface roughness. The SURO simulation results show that the influence of the rough surface on the angular distribution of eroded impurities comes into play when the shadow angle is larger than a threshold value. The larger shadow angle of the rough surface leads to a stronger shift of the angular distribution of the eroded impurities. Different rough surface topographies have been used in the SURO code to check the angular distribution of the eroded impurities. It is found that the shift tendency of the angular distribution is similar for different structures of the rough surface. Based on the numerical modelling results, an analytical model has been developed to investigate the impact of the shadow angle on the angular distribution of the eroded impurities, which shows the consistent result as the SURO simulations. PubDate: 2017-08-15T00:41:00.843403-05: DOI: 10.1002/ctpp.201700022

Pages: 311 - 311 Abstract: The schematic of the analytic model, local angle αloc, and azimuthal angle ϕ of the eroded impurity in the local coordinate. Figures 7a of the paper by Quan Shi et al. PubDate: 2017-09-13T05:17:25.706568-05: DOI: 10.1002/ctpp.201790020

Authors:Amir Jamali; Serajoddin Razavizadeh, Atousa Aliahmadi, Hamid Ghomi Pages: 316 - 321 Abstract: Inorganic antibacterial agents such as metal nanoparticles (NPs) are very important in biomedical and pharmaceutical areas. There are many methods of synthesizing these NPs, but all of them have their own disadvantages. In this study, ultrasonic-assisted spark discharge is employed to produce colloidal silver (Ag) and zinc oxide (ZnO) NPs which are stable without using any stabilizers or surfactants. Different tests such as X-ray diffraction, field emission scanning electron microscopy, and ultraviolet–visible absorption spectroscopy are used for the characterization of the quantity and quality of these NPs, and their antibacterial activity is evaluated by the disk diffusion method and determination of the minimum inhibitory concentrations against Escherichia coli. The results show that the overall antibacterial activity of Ag NPs is higher than that of ZnO NPs. PubDate: 2017-09-13T05:17:24.351279-05: DOI: 10.1002/ctpp.201600021

Authors:Marek Laca; Matěj Jan Morávek, Lukáš Schmiedt, Věra Hrachová, Adolf Kaňka Pages: 336 - 350 Abstract: In our contribution, the positive column of oxygen DC glow discharge is investigated using methods of computational physics at medium pressures (200–687 Pa) and discharge currents from 20 to 40 mA. Under mentioned conditions, the attributes of the DC oxygen discharge are particular, what is based on the existence of two forms: H-form and T-form. One-dimensional fluid model of the stable H-form has been developed. Not only radial profiles of various species in cylindrical tube but also the reaction among them and their interaction with the walls are taken into account. The model is built on the continuous description of concentration of species and drift-diffusion approximation of the particle flux. The results of the simulation are in good agreement with experimental ones. PubDate: 2017-09-13T05:17:25.201888-05: DOI: 10.1002/ctpp.201600063