ION FLUX BEHAVIOR IN HIGH DENSITY PLASMAS

The available electron cyclotron resonance plasma sources have been simulated in two-dimensional configuration space (Z, R) and three-dimensional velocity space (V_z, V_r, V_θ). Using a hybrid model, we treat ions as particles and electrons as fluid. The simulation is specified for plasma parameters of the available apparatus and is focused on the ion flux distributions. For a set of given operating conditions, the spatial distributions of electron temperature, plasma potential, plasma density, ionization rate and the contours map of distributions of particles in different volume cells in velocity space are obtained; statistics on ions that hit the bottom surface are also reported. The distributions of ion flux vectors on different cross-section planes in the plasma are given, and the phenomena of large radial diffusione of ions across magnetic force lines are also demonstrated. Finally, the influences of microwave power and neutral gas pressure on the distributions of ion flux vectors on ZR-plane, ion flux radial distributions and ion currents to all walls have been studied.     

(2+2)RESONANCE ENHANCED MULTIPHOTON IONIZATION-FRAGMENTATION STUDY OF DIMETHYLAMINE

The multiphoton ionization spectra of dimethylamine are given in the 445-470 nm region. A time of flight mass spectrometer was used,and experiment was done under collision free condition. It is found that (2+2) resonance enhanced multiphoton ionization through (n_N,3s) Rydberg state produces parent ions which endure pseudo-α and C—N bond cleavages. The former forms CH₃N⁺H=CH₂ ions,and the latter gives CH₂=N⁺H₂ ions .     

Modified vacuum vibrator ion source for phosphorous and boron ions

A modified version of vacuum vibrator ion source is designed, fabricated and used to obtain phosphorous and boron ions. Its main features (i) controlled amplitude of vibrations at the spark position and (ii) small quantity requirements of materials. Pure powders of boron and red phosphorous were used respectively to get boron and phosphorous ions and in each case the ion current obtained was of the order of 1μA. The results obtained from silver electrodes are compared with those obtained from other metal electrodes. Silver is found to be a suitable electrode material for production of phosphorous and boron ions.     

FORMATION AND MAGNETIC PROPERTIES OF A NOVEL Gd3(Fe,Ti)29Ny NITRIDE

The novel Gd₃(Fe_0.978Ti_0.022)₂₉ compounds and their nitride have been synthesized. The X-ray diffraction patterns of the Gd₃(Fe,Ti)₂₉N_y and its parent compounds were indexed in the Nd₃(Fe,Ti)₂₉-type structure with a monoclinic symmetry and space group P2₁/c, Both the nitride and the parent compounds exhibit ferrimagnetlc coupling. Nitrogenatio led to an increase in Curie temperature and saturation magnetization. The Curie temperatures are 517K for the parent and 765K for the nitride. The saturation magnetizations σ_s at 4.2K are 101.9A·m²/kg for the parent and 128A·m²/kg for the nitride. Both the nitride and parent exhibit a planar anisotropy. Nitrogenation led to a decrease of the contribution of Fe-sublattice to planar anisotropy. The anisotropy fields at 4.2K are 9.8T for the parent and 6.5 T for the nitride.     

A preliminary study of a negative hydrogen PIG-type ion source for the compact cyclotron

A Penning ion gauge (PIG)-type ion source has been used for the generation of negative hydrogen ions (H^-) as the internal ion source of the compact cyclotron. The discharge characteristics of the ion source are systematically studied for hydrogen operation at different discharge currents and gas flow rates on the prototype cyclotron. The preliminary study results for the low DC voltage H^- extraction measurements are presented in this paper. The H^- beam current is measured by the order of magnitude from several tens to hundreds of microamperes at different parameter conditions. The discussion and analysis for the experimental results are good for improving the design and working stability of the ion source.     

Transport properties and battery discharge characteristics of the Ag+ ion conducting composite electrolyte system (1−x)[0.75AgI: 0.25AgCl]: xFe2O3

Ion transport and battery discharge characteristic studies are reported for a new Ag⁺ ion conducting two-phase composite electrolyte system (1−x)[0.75AgI: 0.25AgCl]: xFe₂O₃, where 0 ≤ x ≤ 0.5 in molar weight fraction. An alternative single-phase host-matrix ‘annealed [0.75AgI: 0.25AgCl] mixed system/ solid solution’ has been used in place of the traditional host, AgI. Submicron size particles (<1 μm) of Fe₂O₃ has been used as second phase dispersoid. The composition 0.8[0.75AgI: 0.25AgCl]: 0.2Fe₂O₃, exhibiting the highest room temperature conductivity has been referred to as the optimum conducting composition (OCC). The reason for an enhancement of an order of magnitude in the conductivity from that of the pure host has been identified through direct determination of ionic mobility (μ) and mobile ion concentration (n) using transient ionic current (TIC) technique. The XRD study confirmed the coexistence of the constituent phases. The ionic transference number is found to be very close to unity. This reveals the fact that the silver ions are the sole charge carriers in the system. The results are discussed in the light of space-charge models proposed for the two-phase composite electrolyte systems. Solid state batteries, fabricated using OCC as electrolyte, Ag-metal as anode and mixtures of iodine & graphite, viz. (C+I₂), (C+KI₃), (C+(CH₃)₄NI₃), (C+(C₂H₅)₄NI₃), etc. as cathodes, were discharged under different load conditions. The battery with (C+I₂) cathode performed satisfactorily specially under low current drain states. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

THE MULTIPLE IONIZATION OF ARGON INDUCED BY PARTIALLY STRIPPED CARBON IONS

The cross section ratios of the double, triple and quadruplicate ionization to the single ionization of argon by 1.5-7.5 MeV partially stripped carbon ions are measured by using time-of-flight technique. The Auger transition and the charge exchange process in the multiple ionization of argon are studied. The ratios of cross sections of the direct multiple ionization to those of the direct single ionization are obtained by subtracting the parts of the Auger transition and the charge exchange process from the measured data. It is found that the cross section ratios of the direct multiple ionization to those of the direct single ionization are in good agreement with the predicted mniti-step (ν/q_eff)^-2n+2 law.     

Magnetic properties of TlCoS2 and TlCoSe2 layered compounds

The TlCoS₂ and TlCoSe₂ compounds are synthesized and their magnetic properties are studied in the temperature range 77–300 K. It is established on the basis of x-ray diffraction analysis that these compounds possess a hexagonal structure. Examination of the magnetization and paramagnetic susceptibility has shown that TlCoS₂ and TlCoSe₂ are ferrimagnets. The Curie temperature for TlCoS₂ is equal to 112 K, and T _C for TlCoSe₂ is less than 77 K. The effective magnetic moments are equal to 4.6 μ_B (TlCoS₂) and 4.85 μ_B (TlCoSe₂) and agree well with the theoretical values. __________ Translated from Fizika Tverdogo Tela, Vol. 42, No. 8, 2000, pp. 1449–1450. Original Russian Text Copyright ? 2000 by Sadykhov, Kerimova, Asadov, Veliev.     

New expressions for g—factors of the mixed ground state of 3d^9 ions with a compressional tetragonal symmetry and its application to NaCl：Ni^＋（I）

We deduce new expressions for g-factors of the 3d⁹ ions with a compressional tetragonal symmetry, in which we consider not only the contribution from the spin-orbit coupling of the central transition metal ion but also that of the ligand orbits as well as the admixture of ²B_1g into ²A_1g (ground state). By using the new formulae, the electron paramagnetic resonance g-factors for NaCl:Ni⁺(I) are studied. Thus, the puzzle that the g_‖-shift is positive is reasonably explained.     

DYNAMICS of H+2 in TWO-COLOR ULTRASHORT LASER PULSE

Numerical simulations of ionization and dissociation processes of hydrogen molecular ion H₂⁺ interacting with two-color intense ( 10¹⁴W/cm²-10¹⁵W/cm²) ultrashort (the duration ≈ 22fs) laser pulse are made. The result shows that the ionization and dissociation processes are strongly dependent upon the relative phase between the two color fields. It means that, in the case of ultrashort pulse, the phase coherence control of ionization and dissociation processes can be realized.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.     

Real-time restoration of rotational blurred image using gradient-loading

The key to the restoration of rotational motion blurred image is how to restore the image under a low cost and to correct the irreversibility of the degradation function matrix.Based on the special qualities of degradation function matrix and precise deduction in space-domain, we present a new approach using gradient-loading for restoration of rotational blurred image.By easily adding a gradient operator, the irreversibility of the original matrix is corrected and can be applied for inverse filtering then.Gradientloading is the optimized approach which combines the advantages of both the approaches using constrained least square filtering and traditional diagonal-loading.Compared with the approach using least square filtering, its peak signal-to-noise ratio (PSNR) is improved from 3.18 to 6.46dB, while the computing time is reduced to 1/2-1/3.Experimental results demonstrate the effectiveness, noise-resistibility, robustness, and low complexity of this approach, which make it more suitable for real-time environment.     

All-Optical Logic Device Using Bent Nonlinear Tapered Y-Junction Waveguide Structure

We propose an all-optical logic device made of a bent tapered Y-junction waveguide with a Kerr-type nonlinear interface. It could provide an AND gate, OR gate, and exclusive-OR (XOR) gate. We could obtain different transmission results by adjusting the bending angle. The numerical simulation results show that the device functions as AND, OR, and XOR gates.     

Real-time, continuous-wave terahertz imaging by a pyroelectric camera

Real-time, continuous-wave terahertz (THz) imaging is demonstrated. A 1.89-THz optically-pumped farinfrared laser is used as the illumination source, and a 124 × 124 element room-temperature pyroelectric camera is adopted as the detector. With this setup, THz images through various wrapping materials are shown. The results show that this imaging system has the potential applications in real-time mail and security inspection.