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The effect of biasing on the edge plasma electrical fluctuations and their control was investigated. Biasing was applied to both positive and negative polarity in the range of +380 to −380 V. As soon as biasing was applied, the electrical fluctuations, fluctuations frequency and Hα emission reduced significantly and all of them showed the positive effect of biasing in the edge plasma electrical fluctuations reduction. Experiments also showed that positive biasing is more effective than negative biasing.

Ignition is the point at which a nuclear fusion of hydrogen isotopes reaction becomes self-sustaining. This occurs when the energy being given off by the fusion reactions heats the fuel mass more rapidly than various loss mechanisms cool it. At this point, the external energy needed to heat the fuel to fusion temperatures is no longer needed. As the rate of fusion varies with temperature, the point of ignition for any given machine is typically expressed as a temperature. On the other hand, energy confinement time is expressed by an equilibrium state. Analytical solutions of Grad-Shafranov equation (GSE) can be used for theoretical studies of plasma equilibrium, transport and Magnetohydrodynamic stability of tokamaks. In this paper we have presented two families of exact solutions. With applying these solutions to IR-T1 tokamak, a small, air core, low beta and large aspect ratio tokamak with a circular cross section, we calculated poloidal magnetic flux. Due to the generality and high accuracy of the second exact solution for all of the magnetic configurations of interest, the result of this solution for IR-T1 tokamak is good (tokamak-relevant) equilibrium compare to the first exact solution for this tokamak. We intend to use these analytical solutions as benchmark of numerical equilibrium codes.

ZnO is a wide-band-gap semiconductor material that is now being developed for many applications, including ultraviolet (UV) light-emitting diodes, UV photodetectors, transparent thin-film transistors, and gas sensors. It can be grown as boules, as thin films, or as nanostructures of many types and shapes. However, as with any useful semiconductor material, its electrical and optical properties are controlled by impurities and defects. We have reviewed the growth and analysis of carbon molecular crystals by the plasma enhanced chemical vapour deposition method. The three main synthesis methods of Carbon Nanocrystals (CNCs) are the arc discharge, the laser ablation and the chemical vapour deposition with a special regard to the later one. By two different methods ZnO layers were coated on the tubes. RF sputtering was one of the ways to directly deposit ZnO thin layer on the MWCNCs. On the other hand, we used thermally physical vapour deposition for making thin Zn film to oxidize it later. Scanning electron microscopy and also Raman spectroscopy measurements of the prepared samples confirmed the presence of ZnO nanolayers on the CNC bodies.

Analytical solutions of electromagnetism driven Grad-Shafranov equation (GSE) can be used for theoretical studies of plasma equilibrium, transport and Magnetohydrodynamic stability of tokamaks. In this research, an extended analytic solution to the Grad-Shafranov equation was presented. The solution describes standard tokamaks configurations. It allows the simulation magnetic surfaces of plasmas with elongation and triangularity, with an independent choice of pressure and plasma current. We have determined equilibrium magnetic surfaces in IR-T1 tokamak. With applying these solutions to IR-T1 tokamak, a small, air core, low beta and large aspect ratio tokamak with a circular cross section, we have calculated poloidal magnetic flux. Due to the generality and high accuracy of the first exact solution for all of the magnetic configurations of interest, the result of this solution for IR-T1 tokamak is acceptable equilibrium compare to the second one for this tokamak. These analytical solutions can be used as an input of feedback control system.

Nuclear fusion is a nuclear reaction in which two or more atomic nuclei (such as a deuterium–tritium) come very close and then collide at a very high speed and join to form a new high energy nucleus (Helium). Determination of accurate plasma horizontal position during plasma discharge is essential to transport it to a control system based on feedback. The solutions of Grad-Shafranov equation (GSE) analytically can be used for theoretical studies of plasma equilibrium, transport and magneto hydrodynamic stability. Here we have presented specific choices for source functions, kinetic pressure and poloidal plasma current, to be quadratic in poloidal magnetic flux and derive an analytical solution for Grad-Shafranov equation. With applying this solution to NSTX tokamak, we calculated poloidal magnetic flux, toroidal current density and normalized pressure profiles for this tokamak. Toroidal and poloidal flows can considerably change the equilibrium parameters of tokamak. These effects on the equilibrium of tokamak plasmas are numerically investigated using the code FLOW. As a comparative approach to equilibrium problem, the code is used to model equilibrium of NSTX tokamak for case pure toroidal flow. Comparison of the results of these two methods for NSTX tokamak shows good agreement between two and that our analytical solution can be served as good benchmark against the equilibrium code FLOW.

Capacitive probe with two pins that can measure floating potential of plasma in the tokamak is described. Probe is compared with a Langmuir probe. Small probes size and short connections allow to achieve better performance.

Graphene-based nanostructures exhibit electronic properties that are not present in extended graphene. Graphene nanoribbons (GNRs) are expected to display extraordinary properties in the form of nanostructures. The effect of percent and position of nitrogen atoms on electronic and thermoelectric properties of a GNR is studied using Landauer approach and density functional theory. For this purpose the density of States, electronic current and thermal current have been calculated. Moreover, an analytical model for the thermo-conductance of the nanosized junction in two-dimensional graphene nanosystems developed. The results show that increasing of nitrogen atoms, increases the splitting of p-orbitals as well as band gap at Fermi level. Also the presence of nitrogen impurities is shown to yield resonant backscattering, whose features are strongly dependent on the position of the dopants. It is demonstrated that increasing N concentration decrease the thermal conductivity due to multi-scattering. In addition I–V characteristics exhibit robust nonlinear behaviors, which are strongly dependent on the position and theconcentration of the nitrogen atoms.

High confinement mode (H-mode) in tokamaks is characterized by the formation of a transport barrier at the edge of the plasma. The H-mode increases the plasma energy confinement time by around a factor of two compared to the Low confinement mode (L-mode). This result made a great step towards achieving the higher temperatures and pressures needed to create ignition conditions. The Grad–Shafranov Equation describes the magnetic flux distribution of plasma in an axisymmetric system like a tokamak. In this paper, we have calculated the magnetic flux surfaces in IR-T1 tokamak by two methods. An analytical solution of magnetic surfaces approximated by equilibrium calculation of GS equation based on first three (and then four) terms of expansion in flux function. Results of two methods are in good agreement with each other.

Determination of accurate plasma horizontal position during plasma discharge is essential to transport it to a control system based on feedback. By using the plasma-circuits linearized model, Proportional Integral Derivative (PID) based controllers and a first order transfer function representing the power supply (PS) dynamics of vertical coil system for IR-T1 tokamak, we analyzed step feedback response of the overall system of IR-T1 tokamak and corresponding Bode diagrams for two cases with and without the plasma resistance and the eddy currents distribution. Also we did experiments for determination of plasma horizontal displacement in this tokamak. This work is done by four magnetic probes that are installed on the circular contour of the tokamak. This data used as input to the feedback controller to validate the performance of it. Results of feedback response analysis show that the controller has good performance. Due to approximations in the controller design, construction, installation and implementation of the controller is necessary and this is the purpose of our future works.

WO3 thin film is one of the most important and applied metal oxide semiconductors that have attracted the scientist’s attention in recent decades. WO3 thin films by two different methods: reactive and non-reactive RF magnetron sputtering deposited on soda lime glass. The effect of presence and absence of oxygen gas in system and RF power on structural, morphological and optical properties of thin films were investigated. The XRD analysis of the films shows the amorphous structure. Spectrophotometer analysis and calculation show that the optical properties of reactive sputtered layers were better than the non-reactive sputtered thin films. By changing deposition parameters, over 70 % transmission achieved for WO3 films. The results showed that reactive sputtering method improved the optical properties of layers and increased band gap up to 3.49 eV and on the other hand reduced roughness of thin films. On the whole, presence of oxygen in the chamber during sputtering improved properties of WO3 thin films.

Together with the problem of confinement, plasma–wall interactions present the major constraints toward a magnetic fusion reactor. The solutions of Grad–Shafranov equation (GSE) analytically can be used for theoretical studies of plasma equilibrium, transport and magneto-hydrodynamic stability. Here we introduce specific choices for source functions, kinetic pressure and poloidal plasma current, to be quadratic in poloidal magnetic flux and derive an analytical solution for GS equation. With applying this solution to IR-T1 tokamak, we have calculated the poloidal magnetic flux, toroidal current density and normalized pressure profiles for this tokamak. Toroidal and poloidal flows can considerably change the equilibrium parameters of tokamak. These effects on the equilibrium of tokamak plasmas are numerically investigated using a code FLOW. As a comparative approach to equilibrium problem, the code is used to model equilibrium of IR-T1 tokamak for case pure toroidal flow.

We have reviewed carbon nanotubes (CNTs) production on a silicon wafer by thermal chemical vapor deposition (TCVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs.

Large-area boron doped graphene was synthesized on Cu foil (as a catalyst) by Hot Filament Chemical Vapor Deposition (HFCVD) using boron oxide powder and ethanol vapor. To investigate the effect of different boron percentages, grow time and the growth mechanism of boron-doped graphene, scanning electron microscopy (SEM), Raman scattering and X-ray photoelectron spectroscopy (XPS) were applied. Also in this experiment, the I – V characteristic carried out for study of electrical property of graphene with keithley 2361 system. Nucleation of graphene domains with an average domain size of ~20 µm was observed when the growth time is 9 min that has full covered on the Cu surface. The Raman spectroscopy show that the frequency of the 2D band down-shifts with B doping, consistent with the increase of the in-plane lattice constant, and a weakening of the B–C in-plane bond strength relative to that of C–C bond. Also the shifts of the G-band frequencies can be interpreted in terms of the size of the C–C ring and the changes in the electronic structure of graphene in the presence of boron atoms. The study of electrical property shows that by increasing the grow time the conductance increases which this result in agree with SEM images and graphene grain boundary. Also by increasing the boron percentage in gas mixer the conductance decreases since doping graphene with boron creates a band-gap in graphene band structure. The XPS results of B doped graphene confirm the existence of boron in doped graphene, which indicates the boron atoms doped in the graphene lattice are mainly in the form of BC 3 . The results showed that boron-doped graphene can be successfully synthesized using boron oxide powder and ethanol vapor via a HFCVD method and also chemical boron doping can be change the electrical conductivity of the graphene.

In tokamak plasma, impurities present a number of problems. One is the radiative power loss, principally due to line radiation from partially stripped ions. Another is fuel dilution. This arises because impurity atoms produce many electrons and, for a given plasma pressure, these electrons lake the place of fuel particles. At high concentrations impurities prevent the plasma being heated. This is particularly a problem during the plasma start-up phase since impurities radiate most strongly at low temperatures before they become highly ionized. Impurities can also lead to disruptions as a result of edge cooling and consequent current profile modification. On the other hand, these problems can be prevented by control of plasma equilibrium (which is defined by Grad–Shafranov (GS) equation). Numerous methods exist to solve the GS equation, describing the equilibrium of plasma confined by an axisymmetric magnetic field. In this paper, we have proposed a new numerical solution to the GS equation of an axisymmetric, transformed in cylindrical coordinates solved with the Chebyshev collocation method, when the source term (current density function) on the right hand side is linear. The Chebyshev collocation method is a method for computing highly accurate numerical solutions of deferential equations. We describe a circular cross section of tokamak and present numerical result of magnetic surfaces on the IR-T1 tokamak and then compare the results with an analytical solution.

In this contribution, we have studied the magnetic system of ITER, and plasma equilibrium using the semi-empirical technique. Tokamak magnet systems consist of four main sub-systems: Toroidal field coils, Central solenoid coils, Poloidal field coils, and Correction coils. The plasma horizontal position is calculated from the vertical field coil characteristics. The calculation is made focusing on the vertical field coil current and voltage changes due to a horizontal displacement of plasma column. The results are compared and discussed.

The ITER superconducting magnet systems consists of four main sub-systems: toroidal field (TF) coils, central solenoid coils, poloidal field coils, and correction coils. Like many other ITER systems, the magnet components are supplied in-kind by six domestic agencies. The technical specifications, manufacturing processes and procedures required to fabricate these components are particularly challenging. The management structure and organization to realize this procurement within the tight ITER construction schedule is very complex. On the other hand, toroidal magnetic field ripple in tokamak is an important issue in plasma equilibrium and stability studies. Toroidal magnetic field is created by toroidal torus with finite number of coils, therefore the field has a ripple in torus space. In this paper, we have reviewed the ITER magnetic coils materials, and also we have estimated the amplitude of TF ripples and its dependence to numbers of coils using the “Comsol Multiphysics” software. The calculations which performed for three: 8, 16 and 32 toroidal coils, indicates that increasing the number of toroidal coils lead to reduction of magnetic field ripple and lead to more stable plasma, but diagnostic access to plasma is reduces.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the Editors-in-Chief.After a thorough investigation, the Editors have concluded that the acceptance of this article was based upon the positive advice of at least one illegitimate reviewer report. The report was submitted from an email account which was provided to the journal as a suggested reviewer during the submission of the article. Although purportedly a real reviewer account, the Editors have concluded that this was not of an appropriate, independent reviewer.This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. Apologies are offered to the reviewers whose identities were assumed and to the readers of the journal that this deception was not detected during the submission process.In addition, the corresponding author was not able to explain the reason for adding the author names B. Mahdavipour and A. Hatami to the article upon revision.

Image processing technique (IPT) is a computational technique which is a simple, wide and great for many purposes. In this paper, we used IPT to obtain plasma source such as sun and sunspot temperatures. Sun image was taken by a telescope and DSLR camera and imported to MATLAB software. Using the IPT, we cropped two areas and evaluated their RGB values, using a code which was written according to Python software. We computed wavelengths and then by substituting wavelengths in Wien’s law, we obtained sun’s surface and sunspot temperature’s. The temperature errors for surface and sunspot were 0.57% and 13% respectively.

Determination of accurate plasma horizontal position during plasma discharge and a control system based on feedback is essential to transport it to a safe position near the set point. The design of feedback controller is usually based on primitive modeling of the plasma itself. By using the plasma-circuits linearized model, proportional integral derivative based controllers and a model for the power supply of vertical coil system with some values for its poles, we analyzed step feedback response of the overall system of IR-T1 tokamak and corresponding Bode diagrams for two cases with and without the plasma resistance and the eddy currents distribution. Although experimental validation of the plasma model and also the overall system behavior is an important exercise, the results predicted in simulation can give us good insight about system.

Using a three-dimensional numerical simulation, the dependencies of the electron cloud (virtual cathode) on the distance between the coils in the Polywell fusion reactor were examined. In the Polywell, the role of a stable and energetic virtual cathode is crucial for fusion. It is shown that by increasing the spacing coils, the electron confinement time increases initially and then remains constant. Using the simulation results, an optimum range for the spacing of coils was suggested, which leads to a longer and more effective confinement. The results obtained can be used to design future devices in order to have a more effective virtual cathode.

A structural change of perturbed magnetic configurations (such as magnetic islands) during disruption phase in IR-T1 tokamak was studied. The singular value decomposition (SVD) mode analysis and the (m,n) modes identification were presented. We also presented the SVD technique to analyze the tokamak magnetic fluctuations, time evolution of magnetohydrodynamics (MHD) modes, spatial structure of each time vector, and the energy content of each modes. We also considered different scenarios for plasma from steady-state to predisruption, complete disruption, creation of tearing modes, and finally magnetic islands.

Fabrication of Cadmium Telluride (CdTe) solar cells in large scale on flexible metal foils due to overcome soda lime glass substrate disadvantages lead us to the fabrication of CdTe semiconductor on flexible Cu foil substrates using RF magnetron sputtering. The effects of thickness parameter on the structural, optical and morphological properties of the nanostructures have been studied. X-ray diffraction analysis showed that the films exhibited zinc blende polycrystalline nature of CdTe structure with the (111) orientation as the most prominent peak and it was found that increasing the deposition time increases the crystallinity of the films. Surface properties such as structure, grain size and roughness noticeably affected by varying deposition time, which the shape shifting from nanorod structure to nanofilm was observed from 10 min deposition time to 20 min. The investigation of optical properties by UV–Vis–NIR spectrophotometer shows the improvement in the visible region absorption of CdTe/Cu structure by increasing the deposition time. Therefore, the results indicating growth of CdTe on Cu foil substrate by RF magnetron sputtering without formation of an oxide layer on the surface and optical absorption improvement with respect to crystallinity.

The three main synthesis methods of Carbon nanotubes (CNTs) are the arc discharge, the laser ablation and the chemical vapour deposition (CVD) with a special regard to the latter one. CNTs were produced on a silicon wafer by Thermal Chemical Vapor Deposition (TCVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs. The ideal reaction temperature was 850 °C and the deposition time was 15 min.

In this research the hot filament chemical vapor deposition technique application for growth of monoclinic tungsten trioxide crystal nano-walls on Si substrates without using catalysts was presented. The products were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and four-point probe instrument. The FESEM images and XRD patterns show that crystallinity of the samples was improved when the substrate temperature increases to 800 °C. The peaks intensity of WO3 are enhanced by increasing the substrate temperature, which can be understood based on the fact that the thermal energy enable atoms to diffuse, as a result, a more perfect crystal structure was obtained. From FESEM images, it can be seen that by increasing the temperature the nano-walls structure appears and continues to grow sharper. The width of the nano-walls is in the range of 80–300 nm and lengths of them are about 5 μm. The electrical measurement results show that the resistivity decreased with increasing the substrate temperature, in such a way high crystallinity samples with sheet resistance of 36 Ω/sq and sharper nano-walls morphology were obtained with a temperature of 800 °C. Also measurements of binding energies of both the XPS spectra W4f and O1s core-level electrons indicated that the sample is stoichiometric with maximum substrate temperature.

The theory of tenuous hollow relativistic electron beam in the magnetron-type helix loaded waveguide was presented in the presence of sheath and axial magnetic field. The dispersion relation was obtained with the aid of the proper boundary conditions. The effects of electron beam, helix, and vane parameters on the gain and Doppler-shifted frequency were investigated numerically. The numerical results show that the presence of the vane considerably increases the gain. It has been shown that the maximum values of the gain occur at lower harmonics and the maximum values of the Doppler-shifted frequency occur at higher harmonics. The results show that the gain of the system increases when the helix move away from the vane.

The superconducting magnet system of ITER consists of four main sub-systems: toroidal field coils, central solenoid coils; poloidal field coils; and correction coils. Like many other ITER systems, the magnet components are supplied in-kind by six domestic agencies. The technical specifications, manufacturing processes and procedures required to fabricate these components are particularly challenging. The management structure and organization to realize this procurement within the tight ITER construction schedule is very complex. On the other hand, all plasma processes including linear and early nonlinear stages of MHD instabilities, transport and plasma flows, waves, micro-instabilities and turbulence, represent different kinds of deviations from MHD equilibrium and thus require accurate calculations of equilibrium configurations. The simplest useful mathematical model to describe equilibrium in fusion plasmas is achieved by combining MHD equations with Maxwell’s equations. The final result is the Grad–Shafranov (GS) equation. Analytical solutions to the GS equation are an aid to theoretical investigations into plasma equilibrium, stability and transport in axisymmetric plasmas. In this paper a special analytical solution for GS equation and also simulation of equilibrium by TEQ code for ITER were presented.

Carbon materials doped with only one kind of C–N bonding configuration are a great outlook for studying doping effects on the electronic structure and electrical properties. Synthesis of nitrogen-doped few-layer graphene films on Cu foil is achieved by low pressure chemical vapor deposition (LPCVD). For investigation of nitrogen doped effect on structural, morphological and electrical properties of graphene the reactive gas was a mixture of CH 4 and NH 3 with the different ratio CH 4 and NH 3 by volume at the constant pressure of the growth chamber. The N-doped graphene (NG) samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS). Also in this experiment, the I – V characteristic carried out for study of electrical property of N-doped graphene at different gases mixing ratio with keithley 2361 system. The Raman spectroscopy showed D, G and 2D bound in doped and undoped graphene while we find the intensity of the 2D peak decreases and D peak intensity increases with the increase in the percent of NH 3 in gas mixture. Likewise the presence of weak 2D band in all sample suggest that the produced samples are few layer graphene. SEM images showed dendritic-like morphology in undoped graphene and we observed that point like defect created among this morphology by increasing the nitrogen in synthesis process. The XPS results of sample with 25% NH 3 in gas mixture confirm the existence of nitrogen in doped graphene which indicates the nitrogen atoms doped in the graphene lattice are mainly in the form of pyridinic nitrogen. The study on electrical properties emphasized that the dependence of current with voltage for all samples was linear like behavior, and sample conductivity was decreased with increasing the percent of nitrogen in gas mixture. The results showed that nitrogen-doped graphene can be successfully synthesized and also chemical nitrogen doping can be change the electrical conductivity of the graphene.

The high-energy current of runaway electrons during a major disruption in tokamak reactors can cause serious damage to the first wall of the reactor and reduce its lifetime. Therefore, it is important to find methods for decreasing the generation of runaway electrons and their energy. The safety factor plays an important role in determining the stability criteria for a wide range of MHD modes. Since runaway electrons suffer only rarely from collisions and are hardly sensitive to electrostatic turbulence, their transport is governed by the magnetic lines structure. On the other hand, since the safety factor is related to the magnetic lines structure, changes in safety factor may have important effects on the diffusion of runaway electrons. In this paper, the generation of runaway electrons and their transport is investigated theoretically. Moreover, by changing the discharge voltage of ohmic and toroidal capacitors, different values of the edge safety factor is generated. In fact, in this experiment, the researchers try to increase the diffusion of runaway electrons by using safety factor changes in the IR-T1 tokamak.

Activated carbon is one of the important and widely used porous materials for removal of pollutants from gas streams or liquid solutions. One of the important parameters in determination of quality of activated carbon as an adsorbent material is the capacity for removal of pollutants. The removal capacity of activated carbon is directly proportion to impregnation ratio, carbonization temperature, carbonization time, activation temperature and activation time in synthesis process. In this study the optimum of these processing parameters in synthesis of activated carbon in order to reach the maximum capacity for removal of SO2 as a challenge gas was determined. Series of activated carbon samples was synthesized under different processing parameters as impregnation ratio, carbonization temperature, carbonization time, activation temperature and activation time. Samples were tested for SO2 removal according to ANSI/ASHRE standard 145.1 (2008). Results showed that the maximum total capacity for removal of activated carbon and for removal of as a challenge gas at optimum processing parameters was 1.4 × 10−4 % mass.

We have reviewed the synthesis of nanocomposite zinc oxide deposited carbon nanotube with two different methods. Initially the multi-walled carbon nanotubes (MWCNT) were prepared by the plasma enhanced chemical vapour deposition technique. Then By two different methods ZnO layers were coated on the tubes. RF sputtering was one of the ways to directly deposit ZnO thin layer on the MWCNTs. On the other hand, we used the thermally physical vapour deposition for making thin Zn film to oxidize it later. Scanning electron microscopy and also Raman spectroscopy measurements of the prepared samples confirmed the presence of ZnO nanolayers on the CNT bodies. By the field emission microscopy measurements we found that ZnO deposited CNTs have a more efficient emissivity than that of CNTs alone.

Improved properties of aluminum zinc oxide (AZO) thin films deposited by the magnetron sputtering at room temperature are reported. AZO is one of the most promising transparent conducting oxide materials, which widely used in thin film solar cells. In this study the optimization process of the DC magnetron sputtered AZO films was carried out at room temperature by studying its structural, optical, electrical and morphological properties at different deposition times (5, 10, 15, 20 and 25 min). It can be utilized as a front contact for the cadmium telluride (CdTe) based thin film solar cells. The structural study shows that the preferred orientation of grains is along plane (002), with a hexagonal structure of the grains. The electrical and optical characteristics show that the films has an average transmission of 70 % and a resistivity of the order of 10−4 Ω cm. The morphology analysis suggests the formation of packed grains with a homogeneous surface.

We have reviewed the plasma edge fluctuations analysis over a wide range of plasma and field parameters in the IR-T1 tokamak. Fluctuation levels and spectra were measured using two arrays of Langmuir probes on the edge region. Under almost all conditions the edge plasma was turbulently unstable, with a broadband fluctuation spectrum in the drift wave range of frequencies f = 10–1000 kHz. A stable state was observed only in the very cold, low-current discharge formed at unusually high neutral filling pressure. Otherwise, the relative fluctuation level as monitored by the ion saturation current was very high while the fluctuation power spectra were roughly invariant in shape. The relative fluctuation level was always highest near the wall and decreased monotonically toward the plasma centre.

Transparent and conducting indium tin oxide (ITO) thin films were deposited on soda lime glass substrates by RF plasma magnetron sputtering at room temperature. The effect of thickness (100, 200 and 300 nm) on the physical (structural, optical, electrical) properties of ITO thin films was investigated systematically. It is observed that with an increase in thickness, the X-ray diffraction data indicate polycrystalline films with grain orientations predominantly along (222) and (400) directions; the average grain size increases from 10 to 30 nm; the optical band gap increases from 3.68 to 3.73 eV and the transmission decrease from 80% to 70% . Four-point probes show a low resistivity (2.4×10−5 Ω cm) values for film with a thickness 300 nm. Present work shows that the ITO is a promising transparent conductive oxide material for the solar cell application.

Reduced-activation steels were developed to enhance safety and reduce adverse environmental effects of future fusion power plants. Martensitic and bainitic steels were developed during the 1985–90 timeframe, and the feasibility of their use for fusion was investigated in an international collaboration from 1994 to present. This work continues to improve the steels and the formation of very small nano-metric precipitates through standardized heat treatments in Cr–W–V alloy system using the microscopic observations. Metallography studies have revealed that the microstructure of alloy after tempering has been tempered martensite. Also after tempering, the matrix structure of alloy and the formation of nano-scale precipitates on grain and lath boundaries were confirmed by SEM observations. By the application of XRD spectra analysis and TEM electron diffraction patterns, it was shown that the type of precipitates extracted from alloy, would be M23C6 and M7C3that include a cubic and trigonal crystal structure, respectively.

In this study, diamond films were synthesized on directed Si and improved nucleation nano-iron layer Si substrates using B2O3 in ethanol and hydrogen gas mixture by hot filament chemical vapor deposition method. To investigate the role of catalyst in purity, cluster size, growth rate and conductivity of grown boron-doped films, the boron to carbon ratio was constant. Raman spectroscopy, field emission scanning electron microscopy and four point probe techniques were applied to characterize the properties of films. It was found that nano-iron layer leads to deposit boron-doped diamond film with better structural quality as well as more effective boron doping concentration. This rising in the conductivity of the grown film on Fe-coated substrate can be mainly attributed to the catalytic activity of iron to increase the diamond cluster size as well as reduce the formation of pores and amorphous phases. Moreover, a 25 % increase in film thickness assisted by iron-catalyst was observed.

The porous glass has a high chemical, thermal, and mechanical resistance, which results from a rigid and incompressible silica network. In the present manuscript, porous glasses were prepared and characterized by partial sintering of waste glasses. Polyvinyl alcohol was added as a binder to the glass powder and the mixture was uniaxially cold pressed under two different forces, followed by sintering at 850°C. The effects of thermal history, particle size of glass powder, binder content, and applied pressing forces on pore size and total porosity of fabricated porous glasses were investigated, and final products with the average porosity of 25% were prepared. The average pore size of the specimens was determined using mercury porosimetry. The morphology of the porous glasses was observed by scanning electron microscopy. The results showed that the average pore size of the samples decreased by increasing binder content due to better compaction of the mixed powder.

The aim of this research is to demonstrate the growth of titanium dioxide nanorods. In our testing, growth of nanorods was achieved using the hot filament chemical vapor deposition method. We studied the effects of temperature and time on the growth of nanorods. We also investigated the effect of Co catalyst on the growth of nanorods so that we could measure the Ti content at different times and temperatures. Our samples were studied using scanning electron microscopy, Raman spectroscopy, energy-dispersive x-ray spectroscopy, dot mapping, and x-ray diffraction. Diameter and length of nanorods were 262.07 nm and 719.41–821.38 nm, respectively. Raman spectroscopy was indicative of two peaks (anatase and rutile). The anatase peaks were 650°C, 490, 509, 558, 613, 787 cm−1; and the rutile peak was 435 cm−1. Results show that titanium dioxide nanorods had their best growth and penetration when Co was used as a catalyst at a time of 30 min and a temperature of 650°C.

Fifty to hundred nanometers carbon nanotube and zinc oxide (CNT–ZnO) nanocomposite were successfully synthesized with two different methods. We have initially prepared multi-walled carbon nanotubes (MWCNTs) by the plasma enhanced chemical vapour deposition method. By two different methods, then, ZnO layers were coated on the tubes. Radio frequency sputtering was one of the ways to directly deposit ZnO thin layer on the MWCNTs. Alternatively, we used thermally physical vapour deposition for making thin Zn film to oxidize it later. Scanning electron microscopy and also Raman spectroscopy measurements of the prepared samples confirmed the presence of ZnO nanolayers on the CNT bodies. By field emission (FE) measurements we found that ZnO deposited CNTs have a more efficient emissivity than that of CNTs alone. FE behavior of CNTs was improved by ZnO coating on the tubes. These changes were more sensible by oxidation technique than by sputtering of ZnO. Uniformly coated ZnO layers on CNTs would not significantly changes the FE properties. But, bead-shaped ZnO coated on tubes by the oxidation manner, were scattered on the tubes and behave as a good emitter source.

Diamond-like carbon (DLC) possesses an array of valuable properties: outstanding abrasion and wear resistance; chemical inertness; exceptional hardness; low coefficient of friction; and high dielectric strength. Methods used to deposit DLC include ion beam deposition, cathodic arc spray, pulsed laser ablation, argon ion sputtering, and plasma-enhanced chemical vapor deposition. In the present work, carbon nano-structures were doped by boron atoms to synthesize icosahedral boron carbide using Hot Filament Chemical Vapor Deposition(HFCVD) system. Raman spectroscopy, X-ray diffraction technique, Debye-Scherrer calculation, Tuinstra-Koenig formula and scanning electron microscopy results were presented and discussed.

Carbon nano-structures were doped by boron atoms to synthesize icosahedral boron carbide using Hot Filament Chemical Vapor Deposition method. Raman spectroscopy revealed two broad peaks centered on 1,334 and 1,573 cm−1, the origin of which is sp3 hybrid of diamond (D-band) and sp2 hybrid of graphite (G-band), respectively. These peaks stem from aromatic compounds with sp2 hybrid, demonstrating a local collection of amorphous B13C2 on the substrate surface. Furthermore, D and G peaks are illustrative of more damage inside the structure. X-ray diffraction patterns indicated significant peaks assigned to icosahedral (B13C2) structures in planes (012), (021), and (024). Debye–Scherrer calculation showed that, the crystal size of the products was in range of 5–80 nm. Additionally, the graphite grain size was evaluated by Tuinstra–Koenig formula at a 42–73 nm interval. The decrease observed in the intensity of G and D peaks may stem from disrupting the vibrational behavior of the film and diminution of polariza...

Scintillator is a material that exhibits scintillation when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, absorb its energy and scintillate. Sometimes, the excited state is metastable, so the relaxation back down from the excited state to lower states is delayed (necessitating anywhere from a few nanoseconds to hours depending on the material). The process then corresponds to either one of two phenomena, depending on the type of transition and hence the wavelength of the emitted optical photon: delayed fluorescence or phosphorescence. On the other hand, study of hard X-ray emission from the energetic electrons is an important issue in tokamaks. Suggestion of methods to reduce these electrons and therefore emitted hard X-ray is important for tokamak plasma operation. In this work, we investigated the effects of external applied fields on hard X-ray intensity and Mirnov activity using the NaI scintillator and fast Fourier transform analysis.

In this contribution application of Hot Filament Chemical Vapor Deposition (HFCVD) technique for growth of the nanorods and nanocrystals was presented. Also the effects of temperature, time and the Co catalyst on the growth of nanorods and nanostructures were studied. Carbon nanostructures were doped by boron atoms to synthesize icosahedral boron carbide using HFCVD. The samples were studied using scanning electron microscopy (SEM), Raman spectroscopy, energy-dispersive X-ray spectroscopy (EDX), dot mapping, atomic force microscopy (AFM) and X-ray diffraction (XRD).

An alloy composition of reduced-activation Cr–W–V ferritic steels for nuclear fusion reactors was studied. The formation of nano-metric precipitates through standardized heat treatments in Cr–W–V alloy system is investigated using microscopic observations. Metallography studies have revealed that the micro-structure of alloy after tempering has been Martensite. Also after tempering, the matrix structure of alloy and the formation of nano-scale precipitates on grain and lath boundaries were confirmed by the Scanning Electron Microscope observations. By the application of X-ray Diffraction spectra analysis and transmission electron microscopy (TEM) electron diffraction patterns, it was shown that the type of precipitates extracted from alloy, would be M23C6 and M7C3 that include a cubic and trigonal crystal structure, respectively. TEM analysis has revealed that the morphology of these structural components is mainly spherical and blocky shapes and the average length and thickness of them would be 65 and 50 nm, respectively.