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Electron energy distribution function (EEDF) in the IR-T1 Tokamak edge plasma is measured. In this paper, application of the first derivative method for processing the electron part of I–V characteristics is report. This method is based on the kinetic theory in a non-local approach. Results show that in the confined plasma EEDF is not strictly Maxwellian and is Bi-Maxwellian. Also proposed procedure allows evaluating additional plasma parameters such as plasma potential in Tokamak edge plasma.

The effective ion charge,Z eff, represents the average charge of ionsZ i of gasses inside the system, which indicates the level of the impurities in the plasma. Several techniques have been applied to estimateZ eff, like mass spectroscopy, anomaly factor and Bremsstrahlung radiation. We estimatedZ eff in the IR-T1 tokamak through anomaly factor. The IR-T1 tokamak is a small air-core transformer tokamak with circular cross section and with out conducting shell and divertor. Its aspect ratio is $$\frac{R}{a} = \frac{{45 cm}}{{12.5 cm}}.$$ For a tokamak discharge of 30 kA plasma current and 1.5 V of loop voltage and by anomaly factor we observed thatZ eff value is about 1.5.

In thermal interaction of laser pulse with a deuterium-tritium (DT) plane, the thermal waves of electrons are generated instantly. Since the thermal conductivity of electron is a nonlinear function of temperature, a nonlinear heat conduction equation is used to investigate the propagation of waves in solid DT. This paper presents a self-similar analytic solution for the nonlinear heat conduction equation in a planar geometry. The thickness of the target material is finite in numerical computation, and it is assumed that the laser energy is deposited at a finite initial thickness at the initial time which results in a finite temperature for electrons at initial time. Since the required temperature range for solid DT ignition is higher than the critical temperature which equals 35.9 eV, the effects of quantum correction in thermal conductivity should be considered. This letter investigates the effects of quantum correction on characteristic features of nonlinear thermal wave, including temperature, penetration depth, velocity, heat flux, and heating and cooling domains. Although this effect increases electron temperature and thermal flux, penetration depth and propagation velocity are smaller. This effect is also applied to re-evaluate the side-on laser ignition of uncompressed DT.

Tin oxide (SnO2) is one of the most promising transparent conducting oxide materials, which is widely used in thin film gas sensors. We investigate the dependence of the deposition time on structural, morphological and hydrogen gas sensing properties of SnO2 thin films synthesized by dc magnetron sputtering. The deposited samples are characterized by XRD, SEM, AFM, surface area measurements and surface profiler. Also the H2 gas sensing properties of SnO2 deposited samples are performed against a wide range of operating temperature. The XRD analysis demonstrates that the degree of crystallinity of the deposited SnO2 films strongly depends on the deposition time. SEM and AFM analyses reveal that the size of nanoparticles or agglomerates, and both average and rms surface roughness is enhanced with the increasing deposition time. Also gas sensors based on these SnO2 nanolayers show an acceptable response to hydrogen at various operating temperatures.

In this paper we present the fabrication of cadmium telluride (CdTe) nanostructures by means of RF magnetron sputtering followed by low-energy ion implantation and post-thermal treatment. We have thoroughly studied the structural, optical, and morphological properties of these nanostructures. The effects of nitrogen ion bombardment on the structural parameters of CdTe nanostructures such as crystal size, microstrain, and dislocation density have been examined. From x-ray diffractometer (XRD) analysis it could be deduced that N+ ion fluence and annealing treatment helps to form (3 0 0) orientation in the crystalline structure of cadmium-telluride films. Fluctuations in optical properties like the optical band gap and absorption coefficient as a function of N+ ion fluences have been observed. The annealing of the sample irradiated by a dose of 1018 ions cm−2 has led to great enhancement in the optical absorption over a wide range of wavelengths with a thickness of 250 nm. The enhanced absorption is significantly higher than the observed value in the original CdTe layer with a thickness of 3 μm. Surface properties such as structure, grain size and roughness are noticeably affected by varying the nitrogen fluences. It is speculated that nitrogen bombardment and post-annealing treatment results in a smaller optical band gap, which in turn leads to higher absorption. Nitrogen bombardment is found to be a promising method to increase efficiency of thin film solar cells.

The effect of the positive bias on Reynolds stress (RS) and its effect on the radial turbulent transport at the edge plasma (r/a = 0.9) and scrape-off layer (SOL) region of plasma in tokamak are investigated. The radial and poloidal electric fields (Er, Ep) and ion saturation current (Is) are measured by multi-purpose probe (MPP). This probe is fabricated and constructed for the first time in the IR-T1 tokamak. The most advantage of this probe is that the variations of Er and Ep can be measured in different radii at the single shot. Thus the information of different radii can be compared with high precision. The bias voltage is fixed at Vbias = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9. Moreover, the phase difference between radial and poloidal electric fields, and temporal evolution of the RS spectrum detected by MPP are calculated. RS magnitude on the edge (r/a = 0.9) is more than its value in the SOL (r/a = 1.02). With the applied bias 200 V, RS and the magnitude of the phase difference between Er and Ep are increased, while the radial turbulent transport is decreased simultaneously. Thus it can be concluded that RS affects radial turbulence. Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a = 0.9 in the presence of bias.

The growth behavior of carbon nanotubes synthesized from C2H2 at the temperature range of 700 to 900°C and using thermal chemical vapor deposition (TCVD) method has been investigated. Thin films of nickel (Ni) catalyst, were coated on SiO2 substrates by ion beam sputtering technique. The formation of catalytic nickel nanoparticles was much increased when using NH3 as the environment gas which implies both the formation and the separation of graphitic layer. Scanning electron microscopy (SEM) and Raman results show that the temperature of growth is the effective parameter on the formation of carbon nanotubes (CNTs). Key words: Carbon nanotubes, chemical vapor deposition, temperature.

In this paper we investigate the effects of visible to near infrared (NIR) laser illumination on the optical transmission (OT) and morphological changes (MC) of thin, curved surfaces of polycarbonate (PC) as employed by industry. The second harmonic of Nd:YAG laser (532 nm) and two diode lasers (665 and 980 nm) were used as sources. We have shown that the morphological changes and optical transmission of the PC elements are influenced by visible to infrared coherent illumination. The morphological changes of the PC surfaces are determined using atomic force microscopy (AFM), demonstrating the appreciable changes caused by the shorter wavelengths (higher energy). When analyzing the OT spectra of PC thin films, a measurable decrease in the OT of the PC surfaces which were illuminated by 532, 665 and 980 nm, in particular 532 nm, for energy densities greater than 25 J/cm^2 can be seen.

Following the first result of generating nuclear fusion energy without dangerous radioactive radiation by laser ignition of the proton-11 Boron reaction (HB11), we applied this method to evaluate other fusion reactions with no primary neutron production as the proton-7 Lithium reaction (HLi7) and of the burning of solid density helium isotope 3 He (He3-He3). The new method is a combination of now available laser pulses of 10 petawatt (PW) power and duration in the range of picoseconds (ps) or less. The new mechanism follows the initial theory of Chu and of Bobin for side-on ignition of solid state density fusion fuel developed in about 1972 where some later known physics phenomena had to be added. The essential innovation is the use of the discovery of a predicted anomaly when the mentioned laser pulses are sufficiently clean, i.e. free from prepulses by at least a contrast ratio 108 where acceleration by the nonlinear (ponderomotive) force is dominating.Copyright © 2010 by ASME

A method for the measurement of the plasma position in the IR‐T1 tokamak in toroidal coordinates is developed. A sine‐coil, which is a Rogowski coil with a variable wiring density is designed and fabricated for this purpose. An analytic solution of the Biot‐Savart law, which is used to calculate magnetic fields created by toroidal plasma current, is presented. Results of calculations are compared with the experimental data obtained in no‐plasma shots with a toroidal current‐carrying coil positioned inside the vessel to simulate the plasma movements. The results are shown a good linear behavior of plasma position measurements. The error is less than 2.5% and it is compared with other methods of measurements of the plasma position. This method will be used in the feedback position control system and tests of feedback controller parameters are ongoing.

The measurement of current-carrying plasma column displacement is very important for plasma position control. Two methods for this purpose are introduced. In this paper, calculation and construction of these coils is explained. Multiple moment method has been used and derived for construction of sensing coils Also Fourier Transform has been used and derived for continuous coils. The comparison of their advantages are investigated. For IR-T1 Tokamak, Two Cosine coils & two Saddle Sine coils were designed and constructed, which have been placed diametrically around minor radius of torus. Then an electronic circuit was designed for adding and integrating the Cosine and Saddle Sine coils output with proper gain. The contribution of each coils in final output is calculated. For compensation of unwanted pickups voltage from the time varying fields each signal with adjustable gain is added to main signal, until removing the additional field effects. The final output holds good proportionality to H.D.

Since displacement is very important for plasma position control, in IR‐T1 tokamak a combination of two cosine coils and two saddle sine coils is used for horizontal displacement measurement. According to the multiple moment theory, the output of these coils linearly depends to radial displacement of plasma column. A new circuit for adding these signals to feedback system designed and unwanted effects of other fields in final output compensated. After compensation and calibration of the system, the output of horizontal displacement circuits applied to feedback control system. By considers the required auxiliary vertical field, a proportional amplifier and driver circuit are constructed to drive power transistors these power transistors switch the feedback bank capacitors. In the experiment, a good linear proportionality between displacement and output observed by applying an appropriate feedback field, the linger confinement time in IR‐T1 tokamak obtained, applying this system to discharge increased the plasma duration and realizes repetitive discharges.

The thermoelectric properties of a T-shaped graphene nanodevice (TGN) are investigated by means of the Landauer approach using the π-electron tight-binding model. The dependence of thermopower on the temperature is studied and the results are qualitatively in agreement with many features recently observed in thermoelectric measurements on graphene nanodevice which suggests the existence of a minimum when the EF is several kBT away from the Dirac point. Thermoconductance κ is proportional to transmission coefficient and thermal current has a linear dependence on the temperature. Further, both the electrical and thermal current of electrons in TGN are calculated. The results could be useful in designing efficient graphene-based thermoelectric devices.

In this article after introducing the IR‐T1 tokamak and its diagnostic systems a brief discussion on the range of grossly stable operating conditions of its plasma by Hugill diagram is presented. Hard disruption instability is studied experimentally in the next part, which confirms that MHD behavior in small tokamaks can be characterized by a single parameter q(a), safety factor at plasma edge. Finally the characteristics of the new regime of IR‐T1 are reported. By our new model of triggering different fields (toroidal, ohmic and vertical), the plasma duration time is increased up to 35 ms with Ip of about 25 kA. By modifying capacitance and charging voltage of ohmic and vertical fields the spike oscillations which was appeared in the plasma behavior is taken out. The role of cleaning the vacuum chamber and using heavier gas for glow discharge and the effect of base pressure is described in detail.

In the edge plasma of the CT‐6B and IRAN‐T1 tokamaks the shape of plasma column based on MHD behavior has been studied. The bulk of plasma behavior during plasma column rotation as non‐rigid body plasma has been investigated. We found that mode number and rotation frequency of plasma column are different in angle position, so that the mode number detected from Mirnov coils array located in poloidal angle on the inner side of chamber is more than outer side which it can be because of toroidal magnetic field effects. The results of IR‐T1 and CT‐6B tokamaks compared with each other, so that in the CT‐6B because of its coils number must be less, but because of its Iron core the effect of toroidal magnetic field became more effective with respect to IR‐T1. In addition, it is shown that the plasma column behaves as non‐Rigid body plasma so that the poloidal rotation velocity variation in CT‐6B is more than IR‐T1. A relative correction for island rotation frequency has been suggested in connection with IRAN‐T1 a...

Summary form only given. In this paper, a thick metal film (/spl sim/10 nm-1000 nm) is deposited at DC sputtering magnetron sets and the Copper film is formed by annealing at an elevated temperature. Studied of this solid-phase reaction have revealed the crucial role of material transport in the film but the underlying diffusion mechanisms still remained poorly understood. For ultra-thin Copper films deposited on Brass, the mechanisms governing this solid-phase reaction will likely to be different. In the present study, the initial stages of Cu growth on Brass and substrate were investigated. At high temperature, a complete reaction can be achieved giving rise to a perfect Cu/Brass grown film. Improvement of this upon annealing is characterized by an appreciable decrease of their full width at half maximum.

Summary form only given. In our investigation thin films of copper and brass were prepared by DC magnetron sputtering and coated on flat glasses. The effect of the thickness of brass and copper on electrical and optical properties was studied. The result shows that the resistively of thin films is a function of applied voltage. Furthermore it shows that the decrease in resistively with increased thickness is due to an increase in carrier concentration with increased film thickness.

Summary form only given. As we know, the type of plasma is very important to sputtering process. Therefore, in this paper we used the radiofrequency probe to measuring the conductivity of DC plasma in different conditions of experimental, magnetic field and pressure and changes of gases. Then we obtained the optimum conditions for deposition of thin films.

Ion implantation has been used to modify the mechanical properties of a wide range of metals and alloys using plasma techniques for ion sources and plasma surface treatment [1]. In this study AISI 52100 steel disks, containing 1.5 wt% Cr as the major alloying element, were implanted with nitrogen and carbon dioxide ions at the energy of 90 KeV, with dose in the range 1 × 1018 to 1 × 1019 N2+ ions cm−2, and 3 × 1018 to 1 × 1019 for co2+ ions cm−2. Ion beam current densities and sample temperature, during implantation were 3–6 μA/cm2 and 170°C, respectively. Experiments show, hardness of sample, increases 30–49% using N2+ ions, and 5–17% using co2+ ions. In order to explain the results, formation of beta‐CrN and carbide pahses have been carried out using X‐ray diffraction technique.

Summary form only given, as follows. Internal disruptions or sawtooth oscillations have been observed and investigated with and without a weak resonant helical field (RHF). IR-T1 is a small air core transformer tokamak with circular cross-section (R=45 cm, a=12.5 cm, Bt

Summary form only given, as follows. Measurements of soft X-ray emission from the IR-T1 tokamak plasma have been analysed with tomographic reconstruction methods. IR-T1 is a small air core transformer tokamak with circular cross-section and without copper shell and divertor (R=45 cm, a=12.5 cm, Bt

Summary form only given. Tokamak discharges are usually rather turbulent with a large spectrum of electric and magnetic fluctuations. Mirnov oscillations are caused by rotating magnetic island inside the plasma column originated by resistive instabilities. Depending on the size of the plasma column, the frequency spectrum of Mirnov oscillation is in the range from a few to tens of kHz. We employ the technique to analyze signals measured in the IR-T1 tokamak without and with resonant helical field (RHF). The time-resolved analysis just described applies to the time series of the signal produced by each Mirnov pick-up coil. In actual experimental condition, a large number of coils are used to discriminate the poloidal m toroidal n mode numbers of the oscillations. The characteristics of modes can then be further investigated by applying standard time correlation techniques. Since we suppose that the observed signals are produced by a rotation of magnetic islands, the signals of two neighbour Mirnov pick-up coils must be related by a delay. We see that the resonant helical field has almost no influence on the plasma current and loop voltage and there is a slight decrease of the floating potential at the plasma edge. The characteristic frequency of poloidal propagation of the magnetohydrodynamic (MHD) fluctuations can be determined by using the correlation techniques described. For this calculation we have used the signals from the coils located on the vacuum chamber with low magnetic field because they are better correlated than the one from the coils in the high field side. We have shown that time-resolved spectral analysis can be easily applied to analyse the (MHD) oscillations in tokamak.

The radial dependence of edge plasma turbulence is investigated in the IR-T1 tokamak. The radial profile of the fluctuation level and spectra are measured using an array of Langmuir probes (rake probe) in the r/a = 0.75–1.2 region. In all radial positions the edge plasma is turbulently unstable, with a broad band fluctuation spectrum in the frequency range f = 10–1000 kHz. The relative fluctuation level, as monitored by the ion saturation current J+, is always highest near the wall and decreases monotonically toward the plasma center, while the shape of the fluctuation power spectra is almost unchanged. The result of this experiment shows that in contrast to the more inner regions, the plasma near the wall does not simply have a small density fluctuation about a mean, but rather a shredded structure in which one can imagine that discrete shreds of plasma interact with one another rather than with the average background.

A special analytical solution of the Grad–Shafranov equation (GSE) is presented with source functions, where the plasma pressure is linear in ψ and the squared poloidal current has both a quadratic and a linear ψ term. Half of internal inductance plus poloidal beta and plasma position have been calculated for a typical discharge of IR-T1 tokamak with circular cross-section. In the presented solution, six parameters are measured by the magnetic measurements. The calculated parameters approach the values measured by discrete magnetic coils in the middle of IR-T1 discharge.

The radial propagation of electrostatic fluctuation is considered extremely important for understanding cross-field anomalous transport. In this paper, two arrays of Langmuir probes are used to analyze electrostatic fluctuations in the edge of IR-T1 tokamak plasma in both the radial and the poloidal directions. The propagation characteristics of the floating potential fluctuations are analyzed by the two-point correlation technique. The wavenumber spectrum shows that there is a net radially outward propagation of turbulent fluctuations in the edge and scrape-off layer (SOL) regions. Hence, edge turbulence presumably originates from core fluctuations.

The effects of the argon gas pressure, charging voltage and anode shape on the current sheath dynamics in a low energy (4.9 kJ) Mather type plasma focus (PF) were investigated. The formation and dynamics of the current sheath were monitored by using two magnetic probes, which were inserted radially and axially to explore the evolution of the plasma sheath and to estimate the range of its velocity during the break-down and run-down phases. The radial magnetic probe measurements showed a rather constant current sheath velocity near the insulator, which was more sensitive to the variations of the gas pressure than the charging voltage, and the current sheath did not lose its uniformity by expanding away from the insulator during the break-down phase. The results found from the axial magnetic probe signals revealed a higher current sheath velocity inside the step region of the step anode than the cylindrical one. The simulated axial current sheath trajectories (Lee's model) that were obtained after the fitting process of the current signals showed good agreement both for the cylindrical anode throughout the run-down phase and the step anode before the step region. Inside the step region, the separation between the simulated and the experimental trajectories of the step anode was increased at greater axial distances.

Cadmium telluride (CdTe) is a p-type II-VI compound semiconductor, which is an active component for producing photovoltaic solar cells in the form of thin films, due to its desirable physical properties. In this study, CdTe film was deposited using the radio frequency (RF) magnetron sputtering system onto a glass substrate. To improve the properties of the CdTe film, effects of two experimental parameters of deposition time and RF power were investigated on the physical properties of the CdTe films. X-ray Diffraction (XRD), atomic force microscopy (AFM) and spectrophotometer were used to study the structural, morphological and optical properties of the CdTe samples grown at different experimental conditions, respectively. Our results suggest that film properties strongly depend on the experimental parameters and by optimizing these parameters, it is possible to tune the desired structural, morphological and optical properties. From XRD data, it is found that increasing the deposition time and RF power leads to increasing the crystallinity as well as the crystal sizes of the grown film, and all the films represent zinc blende cubic structure. Roughness values given from AFM images suggest increasing the roughness of the CdTe films by increasing the RF power and deposition times. Finally, optical investigations reveal increasing the film band gaps by increasing the RF power and the deposition time.

In this research we have investigated on a Runaway electron generation in IR-T1 tokamak. For this purpose we used the hard X-ray spectroscopy and magnetic diagnostic. Hard X-ray emission produces due to collision of the Runaway electrons with the plasma particles or tokamak limiters. Runaway electrons in tokamaks can cause serious damage to the first wall of the reactor and decrease its life time. Also, hard X-ray emission generated from high energy Runaway electrons lead to the plasma energy loss. Therefore, suggesting methods to minimize Runaway electrons in tokamaks are very important. Applying external resonant field is one of the methods for controlling the Magnetohydrodynamic (MHD) activity. Present study attempts to investigate the effects of limiter biasing and Resonant Helical magnetic Field (RHF) on the generation of Runaway electrons. For this purpose, plasma parameters such as plasma current, MHD oscillation, loop voltage, emitted hard X-ray intensity, H α impurity, safety factor in the presence and absence of external fields, were measured. Frequency activity was investigated with FFT analysis. The results show that applying resonant fields can control the MHD activity, and then hard X-ray emitted from the Runaway electrons.

Studies of plasma interaction with titanium coated ferritic steel is performed on IR‐T1 tokamak. Titanium coating is one of the candidates for the plasma facing materials in a tokomak. Titaniumization is carried out by a sputtering method. Some of the samples were baked (3 hours at 460 °C) before sputtering. Atomic Force Microscopy (AFM) analyses before and after discharge in r/a = l .04 carried out. The samples (with distinctive titanium layers) were placed at different depths inside the vacuum vessel of the IR‐T1 tokamak in the SOL region. A comparison of the titanium coated steel with bare ferritic steel exposed to plasma tokamak and glow discharges is made in this research. Depth of impurity penetration and retention, and the surface roughness are measured by using surface analysis methods. Rutherford backscattering method is used to measure the content of nitrogen, oxygen and titanium, before and after discharges. The result is shown a change in roughness with respect to position of samples.