Search

The challenges on carbon nanotubes and graphene are still the subject of many research works due to its unique properties. There are three main methods to synthesis carbon nanotubes in which chemical vapor deposition (CVD) method can use for large scale production. The principle of CVD is the decomposition of various hydrocarbons over transition metal supported catalyst. KIT-6 molecular sieve was used as a support to prepare cobalt catalyst for CVD method using metal impregnation method to produce cobalt loadings of 2, 4 and 6 wt%. The catalysts were characterized by XRD, FTIR &TEM. Carbon nanotubes (CNTs) synthesized on Co-KIT-6 was also characterized by XRD, TGA, SEM & Raman spectra. Graphene was synthesized by Hummers method, which is the most common method for preparing graphene oxide. Graphene oxide was prepared by oxidation of graphite using some oxidizing agents like sulphuric acid, sodium nitrate and potassium permanganate. This graphene oxide is further treated with hydrazine solution to convert it into chemically converted graphene and also decorated with nickel metal and characterized. Hummer’s method is important for large scale production of graphene. Both Graphene and carbon nanotubes are used in different fields due to its unique properties. Both Graphene and carbon nanotubes are fabricated in counter electrode of Dye sensitized solar cells (DSSC). By cyclic voltammetry study, it confirms that both materials are good and efficient to replace platinum in the DSSC.

Over the past few years, significant growth has been observed in using MEMS based passive components in the RF microelectronics domain, especially in transceiver system. This is due to some excellent properties of the MEMS devices like low loss, low cost and excellent isolation. This paper presents a design of high performance MEMS passive band pass filter, consisting of L and C with improved quality factor and insertion loss less than the reported filters. In this paper we have presented a design of 2nd order band pass filter with 2.4GHz centre frequency and 83MHz bandwidth for Bluetooth application. The simulation results showed improved Q-factor of 34 and Insertion loss of 1.7dB to 1.9dB. The simulation results needs to be validated by fabricating the device, fabrication flow of which is also presented in the paper.

In the present paper a novel functionally graded piezoelectric (FGP) actuated Poly-Si micro cantilever probe is proposed for atomic force microscope. The shear piezoelectric coefficient d15 has much higher value than coupling coefficients d31 and d33, hence in the present work the micro cantilever beam actuated by d15 effect is utilized. The material properties are graded in the thickness direction of actuator by a simple power law. A three dimensional finite element analysis has been performed using COMSOL Multiphysics® (version 4.2) software. Tip deflection and free vibration analysis for the micro cantilever probe has been done. The results presented in the paper shall be useful in the design of micro cantilever probe and their subsequent utilization in atomic force microscopes.

In this paper three types of carbon nanotubes, namely, zigzag (n, 0), armchair (n= m), and chiral (n, m) are investigated with and without doping using simulation technique. The electronic properties like band structure and density of states of these three configurations with different values of n and m vectors are analysed and compared using Atomistix Toolkit (ATK) software. When the band structures of the designed configurations, reported in this paper are compared, it is observed that when the value of (n-m) vector is divisible by three, the CNTs behave as metals, otherwise they behave as semiconductors. The density of states of carbon nanotubes depicts the energy gap around the Fermi level. For the tube with chiral chirality, density of states is zero near the Fermi level, for semiconductor behaviour there is small gap in density of states near Fermi level and gap increases as the behaviour changes to insulator.

The preliminary assessment of a Lower Hybrid Current Drive (LHCD) system for the DEMOnstration power plant (DEMO) is mainly focused on the R&D needs of the less conventional RF components of the Main Transmission Line (MTL) and of the launcher. 500 kW, CW klystrons will be used to deliver the RF power to independent Passive Active Multijunction (PAM) launcher modules at 5 GHz. This paper describes the criteria followed to investigate the optimum solution for the RF window used as vacuum barrier between the MTL and the launcher, an open issue in the LHCD system for ITER too. The best candidate, capable of withstanding a power level of, or above, 0.5 MW in CW operation and to satisfy the electrical and thermonuclear requirements, is a Pill-Box assembly, based on a thin single disk of CVD-diamond as dielectric, water cooled at the edge. A thickness of 3 mm, much shorter than half a wavelength of the TE°11 mode in the dielectric as in the conventional window (unfeasible and too expensive with CVD-diamond at these frequencies), is sufficient to limit the exerted stress at the edge under the fracture stress for a maximum pressure applied of 0.9 MPa. In this paper the simulation results of conventional and thin CVD-diamond vacuum windows are presented comparing S-parameters, losses and electric fields in both matching condition and with VSWR = 2, using WR284 and WR229 as input/output rectangular waveguide. © 2014 American Institute of Physics.

Tore Supra is dedicated to long pulse operation at high power, with a record in injected energy of 1 GJ (2.8 MW × 380 s) and an achieved capability of 12 MW injected power delivered by 3 RF systems: Lower Hybrid Current Drive (LHCD), Ion Cyclotron Resonance Heating (ICRH) and Electron Cyclotron Resonance Heating (ECRH). The new WEST project (W [tungsten] Environment in Steady-state Tokamak) aims at fitting Tore Supra with an actively cooled tungsten coated wall and a bulk tungsten divertor. This new device will offer to ITER a test bed for validating the relevant technologies for actively cooled metallic components, with D-shaped H-mode plasmas. For WEST operation, different scenarii able to reproduce ITER relevant conditions in terms of steady state heat loads have been identified, ranging from a high RF power scenario (15 MW, 30 s) to a high fluence scenario (10 MW, 1000 s). This paper will focus on the evolution of the RF systems required for WEST. For the ICRH system, the main issues are its ELM resilience and its CW compatibility, three new actively cooled antennas are being designed, with the aim of reducing their sensitivity to the load variations induced by ELMs. The LH system has been recently upgraded with new klystrons and the PAM antenna, the possible reshaping of the antenna mouths is presently studied for matching with the magnetic field line in the WEST configuration. For the ECRH system, the device for the poloidal movement of the mirrors of the antenna is being changed for higher accuracy and speed.Tore Supra is dedicated to long pulse operation at high power, with a record in injected energy of 1 GJ (2.8 MW × 380 s) and an achieved capability of 12 MW injected power delivered by 3 RF systems: Lower Hybrid Current Drive (LHCD), Ion Cyclotron Resonance Heating (ICRH) and Electron Cyclotron Resonance Heating (ECRH). The new WEST project (W [tungsten] Environment in Steady-state Tokamak) aims at fitting Tore Supra with an actively cooled tungsten coated wall and a bulk tungsten divertor. This new device will offer to ITER a test bed for validating the relevant technologies for actively cooled metallic components, with D-shaped H-mode plasmas. For WEST operation, different scenarii able to reproduce ITER relevant conditions in terms of steady state heat loads have been identified, ranging from a high RF power scenario (15 MW, 30 s) to a high fluence scenario (10 MW, 1000 s). This paper will focus on the evolution of the RF systems required for WEST. For the ICRH system, the main issues are its ELM resil...

Since the Chinese anti-missile test in 2007 the problem of space debris and their threat to all space assets has become known to a larger community. Today, advances in laser sources and large mirrors including adaptive optics have matured and are in principle available. The paper first addresses the current situation of accumulated space debris and future predictions of collisions in space. Second, different solutions to mitigate the debris problem will be reviewed with emphasis on the use of high power pulsed lasers as derived from fundamental relations governing the momentum imparted to the debris by the laser pulse and causing their re-entry into the atmosphere with subsequent burn up. Unfortunately the required laser specifications lead to a demand of laser sources which cannot be satisfied with currently available devices. Therefore, two novel laser architectures will be presented. Finally, operational concepts and safety aspects will be addressed in order to evaluate the prospects of laser debris removal.Since the Chinese anti-missile test in 2007 the problem of space debris and their threat to all space assets has become known to a larger community. Today, advances in laser sources and large mirrors including adaptive optics have matured and are in principle available. The paper first addresses the current situation of accumulated space debris and future predictions of collisions in space. Second, different solutions to mitigate the debris problem will be reviewed with emphasis on the use of high power pulsed lasers as derived from fundamental relations governing the momentum imparted to the debris by the laser pulse and causing their re-entry into the atmosphere with subsequent burn up. Unfortunately the required laser specifications lead to a demand of laser sources which cannot be satisfied with currently available devices. Therefore, two novel laser architectures will be presented. Finally, operational concepts and safety aspects will be addressed in order to evaluate the prospects of laser debris re...

This paper investigates the mechanics of a gigahertz oscillator comprising a nanotube oscillating within the centre of a uniform concentric ring or bundle of nanotubes. The study is also extended to the oscillation of a fullerene inside a nanotube bundle. In particular, certain fullerene‐nanotube bundle oscillators are studied, namely C60‐carbon nanotube bundle, C60‐boron nitride nanotube bundle, B36N36‐carbon nanotube bundle and B36N36‐boron nitride nanotube bundle. Using the Lennard‐Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the fullerene and the nanotube bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques which provides considerable insight into the underlying mechanisms....

Three dimensional (3D) channel networks are the key to promise the uniform distribution of nutrients inside 3D hepatic tissue engineering scaffolds and prompt elimination of metabolic products out of the scaffolds. 3D chitosan/gelatin porous scaffolds with predefined internal channels were fabricated and a combination of light microscope, laser confocal microscopy and micro‐CT were employed to characterize the structure of porous scaffolds. In order to evaluate the flow field distribution inside the micro‐structured 3D scaffolds, a computer reconstructing method based on Micro‐CT was proposed. According to this evaluating method, a contrast between 3D porous scaffolds with and without predefined internal channels was also performed to assess scaffolds’ fluid characters. Results showed that the internal channel of the 3D scaffolds formed the 3D fluid channel network; the uniformity of flow field distribution of the scaffolds fabricated in this paper was better than the simple porous scaffold without micro‐fluid channels.Three dimensional (3D) channel networks are the key to promise the uniform distribution of nutrients inside 3D hepatic tissue engineering scaffolds and prompt elimination of metabolic products out of the scaffolds. 3D chitosan/gelatin porous scaffolds with predefined internal channels were fabricated and a combination of light microscope, laser confocal microscopy and micro‐CT were employed to characterize the structure of porous scaffolds. In order to evaluate the flow field distribution inside the micro‐structured 3D scaffolds, a computer reconstructing method based on Micro‐CT was proposed. According to this evaluating method, a contrast between 3D porous scaffolds with and without predefined internal channels was also performed to assess scaffolds’ fluid characters. Results showed that the internal channel of the 3D scaffolds formed the 3D fluid channel network; the uniformity of flow field distribution of the scaffolds fabricated in this paper was better than the simple porous scaffold without micro‐...

Free-Piston Stirling Engines (FPSE) have the potential to provide high reliability, long life, and efficient operation. Therefore, they are excellent candidates for the dynamic power conversion module of a space-based, power-generating system. FPSE can be coupled with many potential heat sources (radioisotope, solar, or nuclear reactor), various heat input systems (pumped loop, heat pipe), heat rejection (pumped loop or heat pipe), and various power management and distribution systems (ac, dc, high or low voltage, and fixed or variable load). This paper reviews potential space missions that can be met using free-piston Stirling engines and discusses options of various system integration approaches. This paper briefly outlines the program and recent progress.

This paper presents design and fabrication of a 1-DOF (degree-of-freedom) drive mode and 2-DOF sense mode micro-gyroscope. It is an inherently robust structure and offers a high sense frequency bandwidth. The proposed design utilizes resonance of the1-DOF drive mode oscillator and employs dynamic amplification concept in sense modes to increase the sensitivity while maintaining robustness. The 2-DOF in the sense direction renders the device immune to process imperfections and environmental effects. The design is simulated using FEA software (CoventorWare®). The device is designed considering process compatibility with SU-8 based UV-LIGA process, which is an economical fabrication technique. The complete fabrication process is presented along with SEM images of the fabricated device. The device has 9 µm thick Nickel as the key structural layer with an overall reduced key structure size of 2.2 mm by 2.1 mm.

Graphene nano ribbons are the strips of graphene sheet which opens band gap in graphene. This opening of band gap increases the on off ratio of these GNR devices and allows its use in logic circuit applications. GNR in transistors give vital applications in these areas. A GNRFET shows large conductance with respect to gate voltages. The effect of temperature on this conductance is seen in this paper by simulating a GNRFET model in VNL. A GNRFET with zigzag electrodes and armchair channel is studied. The conductance with respect to temperature is seen. A temperature range of 0 to 2000 K is selected for the study.

A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible method to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.

The scaling of CMOS transistors has resulted in intensified short channel effects, indicating that CMOS has reached its physical limits. Alternate non silicon based materials namely carbon based graphene, carbon nanotubes are being explored for usability as channel and interconnect material due to their established higher mobility and robustness. This paper presents a drift-diffusion based circuit simulatable Verilog-A compact model of graphene field effect transistor (GFET) for channel length of 100nm.The focus is on the development of simulatable device model in Verilog A based on intrinsic parameters and obtain the current, high cutoff frequency and use the model into circuit level simulations to realize an inverter and a 3-stage ring oscillator using Synopsys HSPICE. The applications are so chosen that their switching characteristics enable the determination of the RF frequency ranges of operation that the model can achieve when used in digital applications and also to compare its performance with exi...

Surface texturing as well as boundary slip is an effective approach to increase the tribological performance, friction and load support of lubricated mechanical components. However, in a textured bearing with boundary slip, cavitation, which is generally neglected, is important, and it alters the flow behavior. Therefore, in this paper a novel analytical equation was proposed based on a modified Reynolds equation considering boundary slip and cavitation. The modified Reynolds equation was derived by following the general approach to deduce the Reynolds equation from the Navier-Stokes equation by assuming classical assumptions, except that boundary slip was present. A theoretical investigation was carried out to study the effect of boundary slip including cavitation on the pressure distribution of a pocket bearing. Different slip configurations (full slip, single slip and semi slip) were studied and compared to various pocket depths. The results indicated that the presence of boundary slip both on the lead...

The high selectivity of the adsorption layer for low-boiling alkanes is shown, the separation factor (α) couple iso-butane / butane is 1.9 at a column temperature of 50 °C.The paper presents sorption and selective properties of planar gas chromatography column on aluminum plate with multi-walled carbon nanotubes as the stationary phase.

This paper presents the design of a Memristor based startup circuit for self biased circuits. Memristor has many advantages over conventional CMOS devices such as low leakage current at nanometer scale, easy to manufacture. In this work the switching characteristics of memristor is utilized. First the theoretical equations describing the switching behavior of memristor are investigated. To prove the switching capability of Memristor, a startup circuit based on memristor is proposed which uses series combination of Memristor and capacitor. Proposed circuit is compared with the previously reported MOSFET based startup circuits. Comparison of different circuits was done to validate the results. Simulation results show that memristor based circuit can attain on (I = 12.94 µA) to off state (I = 1 .2 µA) in 25 ns while the MOSFET based startup circuits take on (I = 14.19 µA) to off state (I = 1.4 µA) in more than 90 ns. The benefit comes in terms of area because the number of components used in the circuit are lesser than the conventional startup circuits.

The paper presents the process design and simulation of silicon-on-insulator (SOI)-based dual-gate metal oxide field-effect transistor (DG-MOSFET) stacked with different dielectric layers on the top of gate oxide. A detailed 2D process simulation of SOI-MOSFETs and its electrical characterization has been done using SILVACO® TCAD tool. A variation in transconductance was observed with different dielectric layers, AlN-gate MOSFET having the highest tranconductance value as compared to other three dielectric layers (SiO2, Si3N4 and Al2O3).

This paper describes the synthesis of nanotube from different grades (Tread * A(non-ASTM), N134,N121,N660 and N330)of carbon black using DC arc discharge method at 40A current for 60sec. Carbon black samples of different grades were procured from industry (Aditya Birla Science and Technology Limited, India). Scanning Electron Micrographs (SEM) of the deposited carbon nanostructures suggests that MWCNTs are formed at 40A and for a minimal exposure time of 60sec.The result formed indicates the N330 grade of carbon black gets converted to MWCNTs (Multiwall Carbon nanotube) as compared to other grades.

In this paper, a temperature dependent equivalent circuit model for graphene nanoribbon (GNR) interconnects is proposed. The stability analysis of GNR interconnects is performed using this proposed model and its performance is compared with respect to that of the copper based interconnects. The analysis is performed for different interconnect systems for 16nm ITRS technology node. With increase in the length of interconnects, the relative stability increases. GNR interconnect shows less increase of resistance with the increase in temperature as compared to Cu interconnects.

In this paper, we demonstrate the possibility of generating spiraling light beams using binary spiral axicons. The influence of the laser wavelength and the axicon numerical aperture on the shape and size of generated spiraling beams is investigated experimentally. We have shown experimentally the possibility of generating spiral beams of different length when laser beams of different wavelengths illuminate a binary spiral axicon. Such beams can be used to manipulate micro- and nanoobjects.

This paper presents the design and simulation of a MEMS Capacitive Magnetometer using FEM (Finite Element Method) tool COMSOL Multiphysics 4.3b and results from this simulation are closely matched with analytically calculated results. A comb drive structure is used for actuation purpose which operates at resonant frequency of device is 11.791 kHz to achieve maximum displacement. A magnetic field in z-axis can be detected by this comb drive structure. Quality factor of MEMS capacitive magnetometer obtained is 18 and it has good linear response in the magnetic field range of 100 µT.

Additive production techniques have the advantage of manufacturing parts without needing a forming tool. One of the most used additive manufacturing processes is "Fused Deposition Modeling" (FDM) which allows the production of prototypes and end-use parts. Due to the manufacture layer by layer, also complex part geometries can be created in one working step. Furthermore, lightweight parts with specific inner core structures can be manufactured in order to achieve good weightrelated strength properties. In this paper the mechanical behavior of lightweight parts manufactured with the 3D production system Fortus 400mc from Stratasys and the material Polyetherimide (PEI) with the trade name Ultem*9085 is analyzed. The test specimens were built up with different inner structures and building directions. Therefore, test specimens with known lightweight core geometries (e.g. corrugated and honeycomb cores) were designed. A four-point bending test was conducted to analyze the strength properties as well as the weight-related strength properties. Additionally the influence of the structure width, the structure wall thickness and the top layer thickness was analyzed using a honeycomb structure.

The current status of the mechanical and electromagnetic design for the ICRF antenna system for W7-X is presented. Two antenna plugins are discussed: one consisting of a pair of straps with pre-matching to cover the first frequency band 25-38 MHz and a second one consisting of two short strap triplets to cover a frequency band around 76 MHz. This paper focusses on the two strap antenna for the lower frequency band. Power coupling of the antenna to a reference plasma profile is studied with the help of the codes TOPICA and Microwave Studio, that deliver the scattering matrix needed for the optimization of the geometric parameters of the straps and antenna box. Radiation power spectra for different phasings of the two straps are obtained using the code ANTITER II and different heating scenarii are discussed. The potential for heating, fast particle generation and current drive is discussed. The problem of RF coupling through the plasma edge and of edge power deposition is summarized. The system contains a prematching capacitor to limit the maximum voltage in the system, and the large mutual coupling between the 2 straps is counterbalanced by the use of a decoupler. The mechanical design highlights the challenges encountered with this antenna: adaptation to a large variety of plasma configurations, the limited space within the port to accommodate the necessary matching components and the watercooling needed for long pulse operation.

A 2.0 MW CW lower hybrid current drive (LHCD) system based on 3.7 GHz klystron sources, is in advanced stage of commissioning, which would drive and sustain plasma current, non-inductively, in superconducting steadystate tokamak (SST1) for long pulse operation. Four klystrons, each rated for 0.5 MW CW rf power, delivers 2.0 MW of rf power to four layer of the LHCD system, which finally feeds the rf power to grill antenna. The antenna system along with vacuum window and vacuum transmission line is successfully integrated on the machine. Its vacuum and pressurization compatibility has been successfully established. To validate the high power performance of LHCD system for SST1 machine, stage-wise commissioning of LHCD system in staggered manner is planned. It has been envisaged that LHCD power may be gradually increased initially, since full power may not be required during the initial phases of SST1 plasma operation. Also if the system is integrated in steps or in phases, then integration issues, as well as high power operational issues, if any, can be addressed, attended and handled in a simpler way before integrating all the layers to the grill antenna. To begin with, one klystron is connected to one layer, out of four layers, which energizes a quarter of the grill antenna. Gradually, the rf power and its pulse length is increased to validate high power performance of the system. Arcing and reflections are observed as rf power is gradually increased. The problems are analysed and after taking appropriate remedial action the system performance is improved for operation up to 160kW. Several trains of short pulses are launched in SST1 vacuum vessel for rf conditioning of the LHCD system. Normally, reflections are high when power is launched in vacuum; therefore the pulse length is restricted up to 100 milliseconds. The high power performance of this layer, connected with grill antenna is validated by launching high power microwaves in vacuum vessel of SST1 machine and experimental results obtained during the validation is presented in this paper. Based on this experience, the rest of the layers would be connected to the grill antenna to validate the LHCD system for full rated power.

The additive assisted laser sintering was recently developed at IKT: A carbon black (CB) additive is used to adjust the polymer's laser absorption behavior with the aim to improve the interconnection of sintered powder layers. In this paper a parameter study, Polyetheretherketone (PEEK) samples were prepared with different contents of carbon black and were laser sintered with varying thermal treatment. The samples were mechanically tested and investigated by optical light and transmission electron microscopy. An influence on the morphology at the border areas of particles and intersections of laser sintered layers was found. Depending on the viscosity of the raw material and CB content, different shapes of lamellae were observed. These (trans-) crystalline or polymorph structures, respectively, influence the thermal and mechanical behavior of the virgin PEEK. Moreover, the thermal treatment during the sintering process caused an improvement of mechanical properties like tensile strength and elongation at break.

Recent progress in integrating the latest LHCD model based on ray-tracing into the Integrated Plasma Simulator (IPS) is reported. IPS, a python based framework for time dependent tokamak simulation, was expanded recently to incorporate LHCD simulation using GENRAY/CQL3D (ray-tracing/3D Fokker-Planck package). Using GENRAY/CQL3D in the IPS framework, it becomes possible to include parasitic LHCD power loss near the plasma edge, which was found to be important in experiments particularly at high density as expected on reactors. Moreover, it allows for evolving the velocity distribution function in 4 D (ν∥, ν⊥, r/a, t) space self-consistently. In order to validate the code, IPS is applied to LHCD experiments on Alctor C-Mod. In this paper, a LHCD experiment performed at the density of ne∼0.5×1020m−3 where good LHCD efficiency and the development of internal transport barrier (ITB) was reported, is modelled in a predictive mode and the result is compared with experiment.

This paper investigates strategies to alter the nano-and-microstructures of carbon-based filler-reinforced polymer matrix composites (PMCs). The matrix materials being studied in this work include polyphenylene sulfide (PPS) and liquid crystal polymer (LCP). A set of experiments were performed to investigate various strategies (i) to fabricate a morphological structure within the polymer matrix; (ii) to develop a thermally and electrically conductive network of nano-scaled fillers; and (iii) to produce a thermally conductive but electrically insulative network of hybrid fillers of nano-and-micro scales. The PMCs' structure-to-property relationships, including electrical and thermal properties, were revealed. In particular, the composites' effective thermal conductivities could be increased by as much as 10-folded over the neat polymers. By structuring the embedded electrically conductive pathways in the PMCs, their electrical conductivities could be tailored to levels that ranged from those of electrical insulators to those of semi-conductors. These multifunctional carbon-based filler-reinforced PMCs are envisioned to be potential solutions of various engineering problems. For example, light-weight thermally conductive PMCs with tailored electrical conductivities can serve as a new family of materials for electronic packaging or heat management applications.

Ion cyclotron resonance heating (ICRH) is one of the main auxiliary heating systems used in present-day tokamaks and is planned to be installed in ITER. In the initial full-field phase of ITER operating with hydrogen majority plasmas, fundamental resonance heating of helium-3 ions is one of a few ICRH schemes available. Past JET experiments with the carbon wall revealed a significant impact of impurities on the ICRH performance in (3He)–H plasmas. A significant reduction of the helium-3 concentration, at which the transition from minority ion to mode conversion heating occurs, was found to be due to a high plasma contamination with carbon ions. In this paper we discuss the effect of Be and another impurity species present at JET after the installation of a new ITER-like wall on the transition helium-3 concentration in (3He)–H plasmas. We suggest a potential method for controlling helium-3 level needed for a specific ICRH regime by puffing an extra helium-4 gas to the plasma.

The material development in the field of bioplastics is steadily increasing. It is important to examine the processability but the Investigation of further process steps is also very important. In this paper the weldability of bioplastics is discussed. Compounds of Polylactide (PLA) and Polybutyleneadipate-terephthalate (PBAT) are produced by a twin screw extruder with different mixing ratios. Tensile specimens are produced by injection moulding and the tensile tests are carried out. In order to verify the weldability, some tensile specimens are cut in halfes and butt welded. Afterwards a tensile test is performed with the welded samples and the results are compared with the values of the unwelded samples. For understanding the results, the morphology of the welds were examined and correlated. It has been found that blends with a mixing ratio of 50:50 have the lowest welding factor, because of the immiscibility of PLA and PBAT. Weld images show segregated areas that reduce the force transmission.

In this paper two promising ways to improve the material characteristics of PLA and PHB-V are presented by showing their positive effects on mechanical, optical, and thermal properties. The optimization is achieved by increasing the crystallization from the melt of the polymer chains and the other by means of a reinforcement of the matrices by bio-based materials. In the case of crystallization specific nucleating agents and optimized process parameters promote optimized crystallization conditions and lead particularly in toughness to significant improvements. In addition to crystallization the introduction of cellulose-based reinforcing materials is also a good alternative to improve the ductility of a biopolymer matrix considerably. Due to their polar surface structure cellulose fibres are favouring a very good interaction to the also polar biopolymers. In addition, the polar surfaces of both materials results in very homogeneous dispersion within the compound.

A 140GHz electron cyclotron resonance heating and current drive (EC H&CD) project for EAST Tokamak is launched in 2011 with a total power of 4MW and pulse length of 100 s. The main objectives of the system are to provide central H&CD, assist start-up and control of MHD activities. The system comprises four gyrotrons each with nominal output power of 1MW at 140GHz. The RF power, transmitted through four evacuated corrugated waveguides will be injected into plasma from the low field side (radial port). The front steering equatorial launcher directs the RF beam over ±25° toroidally and scans over 38° poloidally. At present, the construction of the first 1MW system is undergoing for the expected campaign in the end of 2013. In this paper, the current status of the development and the design of the 140-GHz ECRH system are presented.

On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequency spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 1019 m−3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.

A megawatt-level, 28 GHz electron heating system is being designed to support non-inductive (NI) plasma current (Ip) start-up and local heating and current drive (CD) in H-mode discharges in the National Spherical Torus Experiment Upgrade (NSTX-U). The development of fully NI Ip start-up and ramp-up is an important goal of the NSTXU research program. 28 GHz electron cyclotron (EC) heating is predicted to rapidly increase the central electron temperature (Te(0)) of low density NI plasmas generated by Coaxial Helicity Injection (CHI). The increased Te(0) will significantly reduce the Ip decay rate of CHI plasmas, allowing the coupling of fast wave heating and neutral beam injection. Also 28 GHz electron Bernstein wave (EBW) heating and CD can be used during the Ip flat top in NSTX-U discharges when the plasma is overdense. Ray tracing and Fokker-Planck numerical simulation codes have been used to model EC and EBW heating and CD in NSTX-U. This paper presents a pre-conceptual design for the 28 GHz heating system and some of the results from the numerical simulations.

Laser Shock Processing is developing as a key technology for the improvement of surface mechanical and corrosion resistance properties of metals due to its ability to introduce intense compressive residual stresses fields into high elastic limit materials by means of an intense laser driven shock wave generated by laser with intensities exceeding the 109 W/cm2 threshold, pulse energies in the range of 1 Joule and interaction times in the range of several ns. However, because of the relatively difficult-to-describe physics of shock wave formation in plasma following laser-matter interaction in solid state, only limited knowledge is available in the way of full comprehension and predictive assessment of the characteristic physical processes and material transformations with a specific consideration of real material properties. In the present paper, an account of the physical issues dominating the development of LSP processes from a moderately high intensity laser-matter interaction point of view is presented along with the theoretical and computational methods developed by the authors for their predictive assessment and new experimental contrast results obtained at laboratory scale.

We describe a novel technique for measuring the energies of beta decay electrons. The technique relies on the detection of coherent radiation emitted by an electron in a cyclotron orbit in a strong magnetic field. Since the frequency of cyclotron orbit depends on the particle Lorentz boost, the detection and measurement of the coherent radiation emitted is tantamount to measuring the kinetic energy of the electron. As the technique inherently involves a nondestructive frequency measurement, it can in principle achieve a high resolution and accuracy. A new experimental effort, known as Project 8, will apply this technique to a sensitive measurement of the beta endpoint of tritium, which is sensitive to the absolute mass scale of the neutrino. In this paper we describe experimental progress towards demonstrating the Project 8 technique, and present the configuration of a pilot experiment.

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collisional cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma jets on the objects, slowing them slightly, and causing them to re-enter and burn up in the atmosphere. In this paper, we reassess this approach in light of recent advances in low-cost, light-weight segmented design for large mirrors, calculations of laser-induced orbit changes and in design of repetitive, multi-kilojoule lasers, that build on inertial fusion research. These advances now suggest that laser orbital debris removal (LODR) is the most costeffective way to mitigate the debris problem. No other solutions have been proposed that address the whole problem of large and small debris. A LODR system will have multiple uses beyond debris removal. International cooperation will be essential for building and operating such a system.

Laser processing of materials has achieved significant successes in such areas as pulsed laser deposition, micro-and nanostructuring and surface modification and analysis. However, materials synthesis, fabrication and process monitoring with atomic and molecular specificity at the micro-and nanoscale is just now on the horizon. If the grand challenges attendant to those objectives were met, one could fairly conceive of photonic fabrication systems with important similarities to those of the semiconductor industry while enlarging the palette of materials that could be built, assembled and fabricated using the unique electronic and vibrational interactions of light with matter. This paper discusses the possibilities for meeting some of these grand challenges, starting from selected examples of novel approaches to laser-materials interactions across a range of wavelengths, pulse durations, intensities, and pulse-sequencing strategies. The implications for the design of new lasers and new materials-processing strategies are considered.

This paper investigates laser micro cutting of wide band gap materials for semiconductor industry purposes. Laser is an alternative to blade sawing for hard materials such as sapphire (α-Al2O3) and silicon carbide (SiC) which are useful for new functions. An ultraviolet (355 nm) diodepumped solid-state (DPSS) nanosecond laser is used in this investigation. The properties of the materials are analyzed by the means of ellipsometry and X-ray diffraction in order to understand laser/matter interaction physics. The effect of pulse energy and feed rate (scanning speed) is studied on the depth of the cutting street of α-Al2O3 and SiC. The depth of the grooves increases with laser energy (10 to 147.5 μJ/pulse with typical frequencies of 40 to 160 kHz) It decreases with the feed rate (10 to 150 mm/s) until saturation except for certain conditions for α-Al2O3. Indeed, results show periodic patterns produced by phase explosion that can influence on the achieved depth. The shape, size and periodicity of the recast ma...

We propose to employ small orbit perturbations, induced by photon pressure from ground-based laser illumination, for collision avoidance in space. Possible applications would be a) protecting space assets from impacts with debris and b) stabilizing the orbital debris environment. In comparison to schemes aimed at de-orbiting debris using laser ablation, collision avoidance requires much less force and hence needs less sophisticated laser/telescope systems. In earlier research we concluded that a system consisting of a 10kW class laser, directed by a 1.5m telescope with adaptive optics, could avoid a significant fraction of collisions in low earth orbit. This paper describes our recent efforts which include refining our original analysis, employing higher fidelity simulations and presenting our planned experimental approach.

A new cryogenic system is under construction at the National High Magnetic Field Laboratory (NHMFL) for the cooling of the Series-Connected Hybrid (SCH) magnet as well as the existing 45 T hybrid system. The SCH is a vertical bore, 36 T magnet under development at the NHMFL and it will be installed at the NHMFL in 2013. The 45 T hybrid magnet system producing a 45 T steady field has been operating successfully as a user facility since 1999. The existing cryogenic system at the NHMFL has been in service since 1994 and it is used for supplying Liquid Helium (LHe) to the users and also cooling the 45 T hybrid magnet. The new system has a specified refrigeration capacity of 750 W at 4.5 K and will replace the current refrigerators after its construction due to the increasing maintenance in current refrigerators and the increasing LHe demand by the users at the NHMFL. The design of the new cryogenic system, consisting of a main refrigerator, a distribution system and a gas management and purification system, and its status are presented in this paper.

We have modified scanning transmission x‐ray microscopes (STXM) at the Canadian Light Source and the Advanced Light Source with total electron yield (TEY) detection (TEY‐STXM). This provides improved surface‐sensitive detection, simultaneous with existing bulk‐sensitive transmission detection in the STXM microscopes. We have explored sample‐current and channeltron‐based electron yield detection. Both approaches provide improved surface sensitive imaging and spectroscopy, although channeltron‐based detection is superior. TEY‐STXM provides surface sensitive imaging of ultrathin films such as phase‐separated Langmuir‐Blodgett monolayer films, as well as differentiation of surface and bulk oxides of patterned metallic thin films. This paper will outline the experimental challenges of this method and the opportunities for correlative surface and bulk measurements of complex samples.

A graph is called edge‐transitive, if its automorphisms group acts transitively on the set of its edges. In this paper, we prove every connected cubic edge‐transitive graph of order 10p2 is a symmetric graph, where p is a prime.

In this paper, we propose a cost‐efficient thin film synthesis of the nanocomposite of Graphene and Chitosan using solution casting technique. Characterizations of the thin films clearly indicate the presence of dispersed flakes of Graphene in Chitosan. Spectroscopic studies reveal the presence of nanoparticles of Carbon in the composite though they also indicate presence of Oxygen which transcend from the bulk Graphite crystals. Preliminary amperometric studies reveal an increase in current with absorption of moisture and a potential humidity sensing ability of the nanocomposite thin film.

The present paper reports the investigations on structural relaxation of Se58Ge42−xPbx (9⩽x⩽20) glasses through the study of phase transformation and thermodynamics carried out using differential scanning calorimetry (DSC). The DSC thermograms at constant heating rates exhibit single glass transition and double crystallization on heating, indicating the occurrence of phase separation in these glasses. It has been found through the X‐ray diffraction (XRD) that glasses get crystallized into GeSe2 and PbSe/Se phases after annealing for 2 hrs at an intermediate temperature between first and second crystallization. Kinetics of phase transformation of these glasses studied earliar through the kinetic parameters like activation energy of glass transition and crystallization, avrami exponent, dimensionality of growth show that increase in lead (Pb) contents increases the thermal stability of the glassy samples.The thermodynamic study made through the determination of parameters like specific heat, entropy differe...

This paper presents an experimental investigation on AC conductivity and dielectric behavior of carbon black reinforced high density polyethylene (HDPE‐CB) and HDPE‐CB filled with multiwalled carbon nanotubes (MWNTs‐CB‐HDPE) and Polyaniline (PAni) coated MWNTs‐CB‐HDPE nanocomposites. The electrical properties such as dielectric constant (e′), dissipation factor (tan δ) and AC conductivity (σac) of nanocomposites have been measured with reference to the weight fraction (0.5 and 1 wt% MWNTs), frequency (75 KHz‐30 MHz), temperature (25–90 °C) and sea water ageing. The experimental results showed that the increased AC conductivity and dielectric constant of the nanocomposites were influenced by PAni coated MWNTs in HDPE‐CB nanocomposites. The value of dielectric constant and tan δ decreased with increasing frequency. Further more, above 5 MHz the AC conductivity increases drastically whereas significant effect on tan δ was observed in less than 1 MHz.