Numerical simulation of mather, filippov and concentric plasma focus using Lee model

In this study, numerical simulations of concentric, Mather and Filippov dense plasma focus (DPF) devices using Lee Model have been performed to test the universality of Lee Model. It includes the configuring of the Lee Model Code to work as any DPF devices from measured current waveform to modelling for diagnostics, evolution of the diagnostics-time histories for the dynamics, energies and plasma properties computed from the measured total current waveform by the code. DPF is a potential source of neutrons. The current research focus is on computing the neutron yield,Yn, from DPF by numerical experiments. Published experimental results from these DPF are then compared and analyzed with numerical simulations results in terms of Yn at different operational parameters. The numerical simulations were executed using the 5-phase Lee Model Code version RADPFV5.15de. The computed Yn from a concentric deuterium-tritium KPU-200 DPF is 1.44 X 1013 neutrons per shot at pressure 14.25 Torr and charging voltage 47.7 kV. For the 1.4 kJ DPF, the optimum, Yn was 2.9 X 107 neutrons/shot at 5.5 Torr deuterium pressure. The optimum computed Yn for 11.2 kJDPF at 4.1 Torr was 1.447 X 10s neutrons/shot. For 28.8 kJ device, the optimum computed Yn of 1.24 X 109neutrons/shot was obtained at 2.2 Torr deuterium pressure at 20 kV. For the 480 kJ device, the optimum yield of 1.8 X 1011 neutrons/shot was obtained at pressure 7.6 Torr and charging voltage of 27 kV. Analysis of the results shows that the optimum Yn was achieved only at optimum operating conditions. For the Dena Filippov DPF with discharge energies of 5 kJ and 90 kJ at pressures ranging from 0.1 Torr to 2.5 Torr, the computed Yn is 1.5 X 109 neutrons/shot in agreement with the experimental result of 1.2 X 109 neutrons/shot using deuterium gas. The computed Yn of Iranian First Filippov Type Plasma Focus (IFFT-PF) with deuterium as working gas at pressure of 0.6 Torr is 3.4 X 106 neutrons/shot as compared to the published value o f 3 . 1 x l 0 6 neutrons/shot. These results show that the computed Yn is in good agreement with the measured Yn at charging voltage of 16 kV for Dena device and 26 kV for IFFT-PF. The modelling, results and applications of the Lee Model code are of profound interest

Modeling and simulation for the equilibrium of single mode fiber fusion

Fabrication of fiber coupler using fusion requires stable torch flame. Stable torch flame is needed to have a good performance of fabrication. A model was required to observe the stable by equilibrium state of silicon dioxide fiber and nitrogen gas used for fabrication of fiber coupler. Continuity equation was applied to show the model of kinetic reaction derived from process of fiber molecule and nitrogen gas. Arrhenius equation form based on temperature variation and integration of kinetic model was examined. Validation of kinetic model towards thermodynamic equilibrium is evaluated by a zero dimensional and time dependence. Nitrogen species density is modelled by a continuity equation and extended form of Arrhenius equation. These equations were used to integrate the change of density over time. The integration was performed to acquire density and the reaction rate of each reaction where temperature and time dependence were imposed. A comparison was made with global model within pressure range of 1-100mTorr and the temperature of electron is set to be higher than other nitrogen species. Results show that the chemical kinetic model agrees only for high pressure because of no power imposition. The global model provides the power in the pressure range for electron and nitrogen at high density by a factor of 3 to 5. This model is plausible for evaluating experimental process in the fabrication of fiber coupler

All-optical switches based on GaAs/AlGaAs quantum dots vertical cavity

In this paper, an all-optical switch based on self-assembled GaAs/AlAs quantum dots (QDs) within a vertical cavity is designed and proposed. Two essential aspects of this novel device have been investigated, which include the QD/cavity nonlinearity with appropriately designed mirrors and the intersubband carrier dynamics inside QDs. The vertical-reflection-type switches have been investigated with an asymmetric cavity that consists of 12 periods of GaAs/Al0.8Ga0.2As and 25 periods for the front and back mirrors, respectively. The thicknesses of the GaAs and AlGaAs layers are chosen to be 89 and 102 nm, respectively. To give a dot-in-a-well (DWELL) structure, the 65 nm dimension of Si was recommended to deposit within a 20 nm AlAs QW. Results obtained have shown that all-optical switching via the QD excited states has been achieved with a time constant down to 275-fs and over 29.5 nm tunable wavelengths. These results demonstrated that QDs within a vertical cavity have great potential to realize low-power, consumption polarization-insensitive and micrometer-sized switching devices for future optical communication and signal processing systems

Atom bottom-up manipulation controlled by light for nanobattery use

We propose a new design of the atom bottom-up technique that uses an optical trapping tool to form the atom trapping layer within a thin film grating. By using a PANDA ring resonator, where atoms can be trapped, pumped and controlled by light, where finally, the trapped atoms/molecules can be selected, filtered, and embedded within the required thin film grating layers, which later can form the nanobattery. In application, P-type or N-type atom can be prepared, trapped and embedded within the desired thin film layers, where finally, the nanobattery can be manipulated. The theoretical background of light pulse in a PANDA ring resonator is also reviewed

Survei pengimejan elektrik dan georadar dalam kajian tanah runtuh Taman Hill View,Ampang Selangor

Electrical resistivity and Ground Penetrating Radar (GPR) surveys were carried out at Taman Hill View, Ampang, Selangor landslide area. This landslide site was a part of three similar landslides which occurred at Bukit Antarabangsa, Hulu Klang, Selangor. The landslide had occurred along the road to Bukit Antarabangsa and Athenaeum Tower. The objectives of these studies were to characterise the sliding material and to determine the depth of bedrock below the sliding surface using the electrical resistivity imaging technique as well as to recognise the fractured or weak zone using the GPR technique. The spacing between electrodes used in the survey was 2 to 2.5 m and the survey lines were chosen close to the borehole locations. With a total of 41 electrodes and spacing between each electrode of 2 to 2.5 m, the maximum current electrode spacing in this survey would be between 80-100 m resulting in the deepest subsurface depth investigated approximately at 20 to 25 m. A 100 MHz electromagnetic wave was used in the Ground Penetration Radar survey. The resistivity imaging result showed the weathered granite profile with resistivity value ranging from 2 to 7000 Ωm. The patterns also show that this area had a lot of fractured or weak zones up to a depth of 4 to 5 m based on the occurrence of low resistivities zones in between the high resistivities. These highly fractured and faulted zones also appeared in the GPR sections as shown by the presence of shifted reflectors and layer discontinuity

Spectroscopic diagnostics of laser induced plasma and self-absorption effects in Al lines

Self-absorption (SA) can drastically affect the emission signal which makes quantitative and, in extreme cases, qualitative investigations very challenging in laser induced plasma spectroscopy. In this study, plasma parameters are spectroscopically studied and SA in aluminum emission lines is investigated at various laser energies and gate delays. Q-switched Nd:YAG laser installed on LIBS2500plus system (1064 nm, 6 ns, 10 Hz) was used for ablation. The sample was ablated in air with different laser energies between 5 and 650 mJ, and spectra were recorded at various gate delays between 0 and 23.75 μs. Intensities of spectral lines Al I 308.2 and 309.3 nm were monitored for the range of laser energies and gate delays. The intensity of spectral lines was increased in response to the increasing laser energy. Rapid increase in intensities was observed for the first microsecond after plasma ignition. The maximum intensity of Al is observed at a gate delay of 1.25 μs. Plasma conditions are investigated on the basis of electron density and temperature in response to the change in laser energy and gate-delay. The electron temperature increased from 15 413 K to 20 200 K and the electron density from 5.0 × 1016 cm−3 to 3.5 × 1018 cm−3 with increase in laser energy from 5 to 650 mJ. The electron temperature is exponentially decreased from 26 733 K to 16 649 K and the electron density is reduced from 2.0 × 1017 cm−3 to 1.0 × 1016 cm−3 for increase in the gate delay from 0 to 23.75 μs. The self-absorption effect in resonant spectral lines of Al is estimated on the basis of SA coefficient calculated using FWHM of spectral lines. The highest values of SA coefficient are found for the lowest laser energies and longest gate delays. It states that the SA is significant when the plasma temperature is low and also, when plasma is least dense. It is fairly obvious to conclude that SA effects are least prevalent when the plasma plume is induced by high laser energies and measurements are made at short gate delays

Self-catalysed vapor-liquid-solid growth mechanism of ZnO nanowires grown on silicon substrate pre-coated with ZnO buffer layer

The present article reports the growth mechanism of zinc oxide (ZnO) nanowires grown on silicon substrate pre-coated with ZnO buffer layer by thermal evaporation method. ZnO nanowires are grown for different growth time of 0, 30, 90 and 120 mins with controlled supply of Ar and O2 gas at 650oC. The structural, morphological and crystallinity properties of ZnO nanowires are analyzed by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). FESEM images infers that, the nanowires growth is driven by self-catalysed vapor-liquid-solid mechanism, where the buffer layer serve as nucleation site. EDX spectra show the uniform composition and purity of ZnO nanowires. A strong (002) peak is detected in XRD spectra which indicates that the preferred growth orientation of the nanowires is toward the c-axis with a hexagonal wurtzite structure. The HRTEM microscopic graphs confirm the growth of nanowire along the preferred [0001] axis. Based on the analysis of grown ZnO nanowires, the probable growth mechanism is schematically presented

Filter design using multi-bragg reflectors

In this paper, we present the use of mathematical modeling of dielectric mirror known as known as a Bragg reflector for optical design. A device system consists of the identical alternating layers using high and low refractive indices. Results obtained have shown that the model applications such as quarter-wavelength layers, unequal-length layers, short-pass and long-pass filters, and transmission filter design can be simulated and plotted