Analysis of the Zeeman effect on D_α spectra on the EAST tokamak

Based on the passive spectroscopy,the D_α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis(OSMA) system in EAST tokamak.The Zeeman splitting of the D_α spectral lines has been observed.A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and ±σ components of the D_α atomic spectra to acquire the information of the local plasma.The spectral line shape was investigated according to emission spectra from different regions(e.g.,low-field side and high-field side) along the viewing chords.Each polarization component was fitted and classified into three energy categories(the cold,warm,and hot components) based on different atomic production processes,in consistent with the transition energy distribution by calculating the gradient of the D_α spectral profile.The emission position,magnetic field intensity,and flow velocity of a deuterium atom were also discussed in the context.     

Analysis of extreme ultraviolet spectral profiles of laser-produced Cr plasmas

Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr~(5+)–Cr~(10+)ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.     

时间分辨原子发射光谱诊断脉冲放电气体束等离子体

建成了一套脉冲放电气体束和原子发射光谱等离子体诊断实验装置,利用这套实验装置测量了不同放电条件下等离子体的时间分辨发射光谱,并采用玻尔兹曼作图法和Hα谱线斯塔克展宽法研究了等离子体的原子温度、离子温度和自由电子密度等参数的演化。实验结果表明,脉冲放电的总电量对等离子体参数的演化有较大影响;脉冲放电气体束等离子体中的离子温度远高于原子温度,自由电子密度相对较低,等离子体处于非局域热平衡状态。A special designed pulsed discharge nozzle (PDN) ion source and a plasma diagnostics system based on the atomic emission spectroscopy were constructed. The time-resolved emission spectra of Argon atoms and ions in the region of 300-800 nm were observed and analyzed. The plasma temperatures, including atomic and ionic temperatures, were simulated by Boltzmann plot method, and the free electron density was simulated through the Stark broadening of Hα line. The evolution of these plasma parameters were investigated by high-resolution time-resolved emission spectra. The results show that the total energy struck on the pulsed gas beam is the most important factor which determines the plasma properties and its evolution. The plasma in PDN is concluded into non-local thermodynamic equilibrium (non-LTE) during the evaluation because of the low electron density and the big difference between the temperatures of Argon atoms and ions in all discharge conditions.     

Field Emission Characteristics of BN Films Treated with H2 and O2 Plasma

BN films were synthesized on the (100)-oriented surface of n-Si (0.008-0.02Ωm) by rf magnetron sputtering physical vapor deposition (PVD). A BN film was first treated with H2 plasma for 60 rain and then the H2 treated sample was treated with O2 plasma for 15rain. The films were characterizes by using Fourier transform infrared spectra (FTIR) and atomic force microscopy (AFM). The field emission characteristics of BN films were measured in an ultrahigh vacuum system. A turn-on electric field of 8 V/μm and a current of 400μA/cm^2 were obtained for the BN film treated with H2 plasma. The results show that the surface plasma treatment makes no apparent influence on the surface morphology of the BN films. The transformations of the sample emission characteristics have to do with the surface negative electron affinity (NEA) of the films possibly. The turn-on electric field of the BN film treated with H2 plasma is lower than that without treatment, which possibly attributes to the surface NEA effect. The surface NEA of the H2 treated BN film is lost after O2 plasma treatment.     

Automatic baseline correction of infrared spectra

A fast automatic algorithm is proposed for baseline correction of infrared (IR) spectral signals.It is devised based on iterative curve fitting where orthogonal polynomials are used.The algorithm can process both emission and absorption spectra automatically without human intervention.Orthogonal polynomials are used for curve fitting to reduce computation time.Both emission and absorption spectra are obtained and the results demonstrate the feasibility and practicability of this algorithm.     

Analysis of Charge State Distribution by Non-Local Thermodynamic-Equilibrium Spin-Orbit-Split-Array Collisional Radiative Model

A collisional radiative model based on the spin-orbit-split-arrays is used to determine the charge state distribution of gold plasmas. The ab initio atomic structure code of Cowan and the spin-orbit-split-array model were used to calculate all the emission spectra of the different gold species, and a non-local thermodynamic-equilibrium model was coupled to calculate the ion populations at a given plasma density and electron temperature. The charge state distribution and other plasma parameters were determined by comparing the experimental spectra with the theoretical simulated soectra of gold plasmas.     

Experimental investigation of barium spectra in crossed electric and magnetic fields

This paper has studied the barium spectra in external magnetic and electric fields on the recently-built system based on a super-conducting solenoid with high stability of better than 1 Gauss. Firstly, we compared the spectra in a high pure magnetic field of $B=4.00000$\,T for different polarized laser, $\sigma^{+}$ and $\sigma^-$. We prove that after a proper shift, the $\sigma^+$ and $\sigma^-$ spectra are completely identical. We also investigated the dependence of the spectral feature in the high magnetic field on an additionally applied crossing electric field. Along with the increase of the electric field, there is an energy shift for every spectral line. Based on a transformative Hamiltonian, we explained this energy shift well.     

SECRAL等离子体韧致辐射谱的测量

The axial emitted bremsstrahlung spectra were measured on SECRAL(Superconducting ECR ion source with Advanced design in Lanzhou)using an HPGe detector.The spectral temperature T_(spe) was obtained from the linear fit of the spectra in the semi-log present.The evolution of T_(spe) with microwave power and magnetic field configuration is investigated in this paper.     

Decomposition reaction of phosphate rock under the action of microwave plasma

The decomposition reaction of phosphate rock under the action of microwave plasma was investigated.Phosphate rock and its decomposition products were characterized by x-ray diffraction(XRD),energy disperse spectroscopy(EDS),and chemical analysis.The measurements of electron temperature(T_e) and electron density(N_e) of plasma plume under atmospheric pressure were carried out using optical emission spectroscopy(OES).The electron temperature(T_e) was determined based on the calculation of the relative intensity of the O Ⅱ(301.91 nm) and O Ⅱ(347.49 nm) spectral lines.Correspondingly,electron densities were obtained using the Saha ionization equation which was based on the C Ⅰ(247.86 nm) line and the C Ⅱ(296.62 nm) line under the assumption of local thermodynamic equilibrium(LTE).The relationship between the relative intensity of the active components and the gas output was studied by the spectrometer.Finally the reaction mechanism of the decomposition of the phosphate rock under the action of the atmospheric pressure microwave plasma was proposed.The results showed that with the increase of CO flow and microwave power,the electron temperature and electron density in the plasma show a decreasing and increasing trend.The CO is dissociated into gaseous carbon ions under the action of microwave plasma,and the presence of gaseous carbon ions promotes the decomposition of the phosphate rock.     

Stark-Broadened Profiles of the Spectral Line P_α in He Ⅱ Ions

We report a systematic method to perform calculations of spectral line broadening parameters in plasmas.This method is applied to calculate Stark-broadening line profiles of Pα(n=4→n = 3) transitions under certain specific plasma conditions,by treating this case as an example.In the framework of the fully relativistic Dirac Rmatrix theory,we calculate the electron-impact broadening operators,which are assumed to be diagonal matrix to simplify the situation.The electric microfield distribution function is calculated by retaining Hooper's formalism.The dipole matrix elements and atomic structure parameters used in these calculations have been obtained from atomic structure GRASP code.Based on this required data,we calculate the Stark-broadened line profiles of the Paschen spectral lines in He Ⅱ ions in a systematic manner.Overall,there is a very good agreement between our calculated Stark-broadened line profiles and other line broadening numerical simulation codes(SimU and MELS).Our reported spectral line-broadening data have real applications in plasma spectroscopy,plasma diagnosis and aiso piay a fundamentai role in plasma modeling.     

Time-Resolved Measurement of Radiatively Heated Iron 2p-3d Transmission Spectra

An experimental measurement of radiatively heated iron plasma transmission spectra was performed on Shenguang II laser facility. In the measurement, the self？emission spectrum, the backlighting spectrum, and the absorption spectrum were imaged with a flat filed grating and recorded on a gated micro channel plate detector to obtain the time-resolved transmission spectra in the range 10-20 ？ （approximately 0.6-1.3 keV）. Experimental results are compared with the calculation results of an unsolved transition array （UTA） code. The time-dependent relative shift in the positions of the 2p-3d transmission array is interpreted in terms of the plasma temperature variations.     

Intensities and spectral features of the ~4I_(13/2)-~4I_(15/2) potential laser transition of Er~(3+) centers in CaF_2-CeF_3 disordered crystal

A CaF_2-CeF_3 disordered crystal containing 1.06% of Er~(3+) ions was grown by the temperature gradient technique.Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the ~4I_(13/2)→~4I_(15/2) transition of Er~(3+). In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the ~4I_(13/2) emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of 0.73 × 10~(-20) cm~2, and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature ~4I_(13/2)→~4I_(15/2) emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb~(3+) ions in heavily doped CaF_2 erbium ions in the CaF_2-CeF_3 crystal reside in numerous sites with dissimilar relaxation rates.     

Correction and analysis of lead content in soil by laser-induced breakdown spectroscopy

The laser-induced breakdown spectroscopy is used to analyze the lead content in soils. The analyzed spectral line profile is fitted by Lorentzian function for determining the background and the full-width at half-maximum （FWHM） intensity of spectral line. A self-absorption correction model based on the information of spectral broadening is introduced to calculate the true value of spectral line intensity, which refers to the elemental concentration. The results show that the background intensity obtained by spectral profile fitting is very effective and important due to removing the interference of spectral broadening, and a better precision of calibration analysis is acquired by correcting the self-absorption effect.     

Landau damping in a bounded magnetized plasma column

The damping decrement of Landau damping and the effect of thermal velocity on the frequency spectrum of a propagating wave in a bounded plasma column are investigated.The magnetized plasma column partially filling a cylindrical metallic tube is considered to be collisionless and non-degenerate.The Landau damping is due to the thermal motion of charge carriers and appears whenever the phase velocity of the plasma waves exceeds the thermal velocity of carriers.The analysis is based on a self-consistent kinetic theory and the solutions of the wave equation in a cylindrical plasma waveguide are presented using Vlasov and Maxwell equations.The hybrid mode dispersion equation for the cylindrical plasma waveguide is obtained through the application of appropriate boundary conditions to the plasma-vacuum interface.The dependence of Landau damping on plasma parameters and the effects of the metallic tube boundary on the dispersion characteristics of plasma and waveguide modes are investigated in detail through numerical calculations.     

Modification of Boundary Fluctuations by LHCD in the HT—7 Tokamak

Measurements of boundary fluctuations and fluctuation driven electron fluxes have been performed in ohmic and lower hybrid current drive enhanced confinement plasma using a graphite Langmuir probe array on HT-7 tokamak. The fluctuations are significantly suppressed and the turbulent fluxes are remarkably depressed in the enhanced plasma. We characterized the statistical properties of fluctuations and the particle flux and found a non-Gaussian character in the whole scrape-off layer with minimum deviations from Gaussian in the proximity of the velocity shear layer in ohmic plasma. In the enhanced plasma the deviations in the boundary region are all reduces obviously. The fluctuations and induced electron fluxes show sporadic bursts asymmetric in time and the asymmetry is remarkably weakened in the lower hybrid current driving (LHCD) phase. The results suggest a coupling between the statistical behaviour of fluctuations and the turbulent flow.     

Influence of number and depth of magnetic mirror on Alfvnic gap eigenmode

Alfvnic gap eigenmode(AGE) can eject energetic particles from confinement and thereby threaten the success of magnetically controlled fusion. A low-temperature plasma cylinder is a promising candidate to study this eigenmode, due to easy diagnostic access and simple geometry, and the idea is to arrange a periodic array of magnetic mirrors along the plasma cylinder and introduce a local defect to break the field periodicity. The present work validates this idea by reproducing a clear AGE inside a spectral gap, and more importantly details the influence of the number and depth(or modulation factor)of magnetic mirror on the characteristics of AGE. Results show that AGE is suppressed by other modes inside the spectral gap when the number of magnetic mirrors is below a certain value, which leads to a weakened Bragg's effect. The structure and frequency of AGE remain unchanged for a decreased number of magnetic mirrors, as long as this number is enough for the AGE formation. The width of spectral gap and decay constant(inverse of decay length) of AGE are linearly proportional to the depth of magnetic mirror, implying easier observation of AGE through a bigger mirror depth. The frequency of AGE shifts to a lower range with the depth increased, possibly due to the unfrozen plasma with field line and the invalidity of small-perturbation analysis. Nevertheless, it is exciting to find that the depth of field modulation can be increased to form AGE for a very limited number of magnetic mirrors. This is of particular interest for the experimental implementation of AGE on a low-temperature plasma cylinder with limited length.     

Simulation of natural convection under high magnetic field by means of the thermal lattice Boltzmann method

The thermal lattice Boltzmann method (TLBM), which was proposed by J. G. M. Eggels and J. A. Somers previously, has been improved in this paper. The improved method has introduced a new equilibrium solution for the temperature distribution function on the assumption that flow is incompressible, and it can correct the effect of compressibility on the macroscopic temperature computed. Compared to the previous method, where the half-way bounce back boundary condition was used for non-slip velocity and temperature, a non-equilibrium extrapolation scheme has been adopted for both velocity and temperature boundary conditions in this paper. Its second-order accuracy coincides with the ensemble accuracy of lattice Boltzmann method. In order to validate the improved thermal scheme, the natural convection of air in a square cavity is simulated by using this method. The results obtained in the simulation agree very well with the data of other numerical methods and benchmark data. It is indicated that the improved TLBM is also successful for the simulations of non-isothermal flows. Moreover, this thermal scheme can be applied to simulate the natural convection in a non-uniform high magnetic field. The simulation has been completed in a square cavity filled with the aqueous solutions of KCl (11wt%), which is considered as a diamagnetic fluid with electrically low-conducting, with Grashof number Gr=4.64× 10^4 and Prandtl number Pr=7.0. And three cases, with different cavity locations in the magnetic field, have been studied. In the presence of a high magnetic field, the natural convection is quenched by the body forces exerted on the electrically low-conducting fluids, such as the magnetization force and the Lorentz force. From the results obtained, it can be seen that the quenching efficiencies decrease with the variation of location from left, symmetrical line, to the right. These phenomena originate from the different distributions of the magnetic field strengths in the zones of the symmetrical central line of the magnetic fields. The results are also compared with those without a magnetic field. Finally, we can conclude that the improved TLBM will enable effective simulation of the natural convection under a high magnetic field.     

Curvature and Zeeman effects on persistent currents in a multi-walledcarbon nanotorus

Taking into account both the intrinsic curvature and Zeeman effects, persistent currents in a multi-walled carbon nanotorus are explored by using a supercell method, within the tight-binding formalism. It is shown that in the absence of the Zeeman effect, the intrinsic curvature induces some dramatic changes in energy spectra and thus changes in the shape of the flux-dependent current. A paramagnetism--diamagnetism transition is observed. With consideration of the Zeeman splitting energy, the period of persistent current is destroyed, and a diamagnetism--paramagnetism transition is obtained at high magnetic field. In addition, we further explore the effect of external electric field energy (E_ef) on persistent current, indicating that it changes unmonotonously with E_ef.     

Optical properties of ZnO thin films on SiO_2 substrates deposited by radio frequency magnetron sputtering

The optical properties of both the annealed and as-deposited ZnO thin films by radio frequency (RF) magnetron sputtering on SiO2 substrates were studied. In the annealed films, two pronounced well defined exciton absorption peaks for the A and B excitons were obtained in the absorption spectra, a strong free exciton emission without deep-level emissions was observed in the photoluminescence (PL) spectra at room temperature. It was found that annealing the films in oxygen dramatically improved the optical properties and the quality of the films.     

Mixed heavy metal effect on emission properties of Er~(3+)-doped borosilicate glasses

Er3+-doped heavy metal borosilicate glasses were prepared using conventional melting and quenching method. The emission spectra of 4I13/2 → 4I15/2 transition were observed upon excitation at 974 nm and the lifetime of 4I13/2 level of Er3+ was measured. Based on these data, the fluorescence properties of Er3+ are investigated on the emission and gain characteristics at the 1.5 μm bands. In particular, the effect of relative heavy metal content on fluorescence properties is discussed.