Effect of atmospheric pressure pulsed discharge spatial inhomogeneity on Ar I and H I lines: Electron number density study

The spatial inhomogeneity of pulsed atmospheric pressure discharge in argon is investigated using the electron number density N_e diagnostics procedure applied to asymmetrically broadened Ar I lines. A dedicated fitting procedure is used for describing Ar I 703.0 nm line shape recorded from argon gas discharge and H I (at 486.13 and 656.28 nm) lines recorded from Ar-H₂ gas mixture discharge. The results revealed the change in N_e in both axial and radial directions. The additional Ar I lines at 614.5, 710.7, 731.2, and 731.6 nm, recorded from integral spatial radiation, are analysed as well to confirm the results from the plasma column region. The possibility of using AlO (B²∑⁺–X²∑⁺) and CN (B²∑⁺–X²∑⁺) molecular bands for gas temperature T_g measurements in this type of gas discharge source is demonstrated and T_g used as an input parameter for the N_e diagnostics procedure. For the proper identification of molecular band spectral lines, the Fortrat parabolas are constructed. The results obtained from Ar I 703.0 nm line indicate three different N_e values, with N_e1 ≈ 0.6 × 10¹⁶ cm⁻³, N_e2 ≈ 3.6 × 10¹⁶ cm⁻³, and N_e3 ≈ 19 × 10¹⁶ cm⁻³ measured from the plasma column. These N_e values increase in the cathode and anode region.     

Stark broadening and displacement of isolated He I lines

Experimental results for Stark broadened He I lines emitted by a helium plasma jet (N_e≈3×10¹⁶ cm^-3) are compared with theory; agreement is well enough for widths whereas shifts calculations present generally large discrepancies with experimental data.     

Spectroscopic study of plasma during electrolytic oxidation of magnesium- and aluminium-alloy

We present the results of an optical emission spectroscopy study of Plasma during Electrolytic Oxidation (PEO) of magnesium- and aluminum-alloy. Plasma electron number density N_e diagnostics is performed either from the H_β line shape or from the width or shift of non-hydrogenic ion lines of aluminum and magnesium. The line profile analysis of the H_β suggests presence of two PEO processes characterized by relatively low electron number densities N_e≈1.2×10¹⁵ cm^?3 and N_e≈2.3×10¹⁶  cm^?3. Apart from these two low N_e processes, there is the third one related to the ejection of evaporated anode material through micro-discharge channels. This process is characterized by larger electron density N_e=(1.2–1.6)10¹⁷ cm^?3, which is detected from the shape and shift of aluminum and magnesium singly charged ion lines. Two low N_e values detected from the H_β and large N_e measured from the widths and shift of ion lines suggest presence of three types of discharges during PEO with aluminum- and magnesium-alloy anode. On the basis of present and earlier results one can conclude that low N_e processes do not depend upon anode material or electrolyte composition.The electron temperature of 4000 K and 33,000 K are determined from relative intensities of Mg I and O II lines, respectively. The attention is drawn to the possibility of N_e application for T_e evaluation using Saha equation what is of importance for PEO metal plasma characterization. During the course of this study, difficulties in the analysis of spectral line shapes are encountered and the ways to overcome some of the obstacles are demonstrated.     

Measurement of excited state number densities of oxygen and nitrogen in a non-equilibrium plasma

Number densities of several excited states of atomic oxygen and nitrogen have been measured in the decaying non-thermal plasma of a θ-pinch afterglow. The spatial variation of the electron density and temperature as functions of time after initiation of main bank discharge have also been measured to facilitate a comparison of the excited state number densities with model calculations. Measurements of the atomic oxygen excited states indicate that quintet to triplet spin exchange collisions and doubly excited states must be included in the model. The measured populations of the excited atomic nitrogen states agree well with those calculated at high density (N_e≈ 10¹⁴ cm^?3), but disagree badly at lower densities (N_e ≈ 10¹² cm^?3). The discrepancies seem to be real since they are larger than expected measurement uncertainty.     

Atomic Model Calculations of Gain Saturation in the 46.9 nm Line of Ne‐like Ar

The gain saturation in the 46.9 nm line of the Ar⁺⁸ laser is analyzed using an atomic kinetics code. The dependence of the gain (G) on the electron kinetic temperature (T_e) in the region (50 ‐150 eV) is calculated in the quasi steady‐state approximation for the different values of the electron density (N_e) and the plasma radius (r_pl). The influence of radiat on trapping, ion random and mean velocities, Stark line broadening and refraction losses on the gain saturation is taken into consideration. For r_pl = 150‐600 μm, the amplplication (G > 0 cm^‐1) exists in the large temperature/density domain (T_e = 60‐150 eV, N_e = 0.5‐10 × 10¹⁸ cm^‐3). However, the value G_s ∼ 1.4 cm^‐1 required for the gain saturation at the typical plasma length L_pl ∼ 15 cm is reached in the extremely narrow density regions at the high temperatures. The saturation is reached for r_pl = 600 μm at T^s_e = 150 eV in the region N^s_e = 1.8‐2 × 10¹⁸ cm ^‐3, for r_pl = 300 μm at T^s_e = 125 eV and N^s_e = 2.5‐3 × 10¹⁸ cm^‐3, and for r_pl = 150 μm at T^s_e = 110 eV and N^s_e = 3‐4 × 10¹⁸ cm^‐3. The broadest density region (N^s_e = 2 ‐8 × 10¹⁸ cm^‐3) is predicted for the narrowest column (r_pl = 150 μm) at the highest temperature (T^s_e = 150 eV). The operation in the broadest density region N^s_e, should make easier achievement of the gain saturation in the experiments.     

Anomalous Cs I 5d-5⨍ lineshape in a non-debye plasma

Laser-induced cesium plasmas were diagnosed by emission spectroscopy, yielding electron densities in the range N_e = 10¹⁶?5 × 10¹⁷ cm^-3 and electron temperatures in the range T_e = 0.2-1 eV. The experimental lineshapes for T_e = 0.5 eV were found to be in good agreement with theory. For the more strongly coupled plasmas at N_e = 1-2 × 10¹⁶ cm^-3 and T_e = 0.2 eV, however, the Cs I 5d-5? lineshape was more asymmetric than predicted.     

Steady state and transient self-interaction of a laser beam in a strongly ionized moving plasma

The steady state and transient self-interaction of a laser beam with a strongly ionized plasma flowing transverse to the direction of propagation have been investigated by a phenomenological approach using perturbation theory, WKB and paraxial ray approximations. The effect of the transverse motion of the plasma has been included by a convection term in the energy balance equation and is found to result in the non-symmetrical heating of electrons. As a result the beam is shifted towards the direction of transverse flow of the plasma by an amount that increases with the flow velocity. The extent of asymmetry in self-focusing along the transverse directions is, however very small. In a typical case of 7.6×10⁵ watt laser of ω=10⁴ GHz and initial beam widthr ₀=0.05 cm the transverse shiftx _p=0.1r ₀ is predicted in a distance of propagationz=0.34 cm in a strongly ionized plasma of electron densityN _e=10¹⁶ cm^?3 and transverse flow velocityW ₀=10⁷ cm/sec.     

Etude spectroscopique de l'effet d'anode

Spectral lines of LiI emitted by an anodic plasma, produced during electrolysis of a KCl-LiCl mixture, have been observed. This paper deals with diagnostic studies of this plasma and is based on a comparison of observed line profiles for LiI(2P-3D), (2P-4S) and (2P-4D, 4F) with calculated values derived from the Griem-Baranger impact theory. We have found, from the ensemble of the results, that the electron density in the plasma center is N_e(0) ? 1·8×10¹⁷ cm^-3, the electron temperature is T_e(0) ? 9×10³ °K, and the plasma thickness is l ? 200 μ.     

电子回旋共振等离子体特性及其对生长氮化镓晶膜的影响

为了解并优化在电子回旋共振等离子体辅助化学汽相沉积GaN晶膜的工艺研究中的等离子体特性,利用朗缪尔探针及法拉第筒系统地测量了离子密度(N_i)、等离子体势(V_p)、电子温度(T_e)及离子流强(J_i)等多个等离子体参量随微波功率(P_w)及沉膜室气压(p)变化的关系.给出了在P_w＝850W,p＝0.22Pa时,上述等离子体参量的轴向及径向分布.GaN晶膜的生长速率、电学及晶体学性能 关键词：     

Determination of the electron concentration and temperature,as well as the reduced electric field strength,in the plasma of a high-voltage nanosecond discharge initiated in atmospheric-pressure nitrogen by a runaway electron beam

We report on the results of spectroscopic measurements of electron concentration N _e and temperature T _e , as well as the reduced electric field strength E/N in the plasma of a high-voltage nanosecond discharge in the gap with a strongly nonuniform electric field distribution, which is filled with nitrogen under the atmospheric pressure. The possibility of using the method for determining T _e and E/N, which is based on the determination of the ratio of the peak intensities of the ionic N ₂ ⁺ (λ = 391.4 nm) and molecular N₂ (λ = 394 nm) nitrogen bands, is proved. We detected the mean values of quantities N _e , T _e , and E/N amounting to ～2 × 10¹⁴ cm^?3, ～2 eV, and ～240 Td, respectively. In addition, the dynamics of these quantities is determined.     

Experimental Stark widths and shifts of two ultraviolet C(II) lines

Photoelectric measurements of Stark widths and shifts of the components of the C(II) multiplet UV13 at 2837 Å were made with a wall-stabilized arc in a gas mixture of argon, hydrogen and carbon dioxide. Plasma diagnostics have been carried out to determine the electron density and the temperature. For experiments performed under two different physical conditions, the values n_e(1) = 4.95 × 10¹⁶ cm^?3, T(1) = 11,430 K and n_e(2) = 6.78 × 10¹⁶ cm^?3, T(2) = 12,080 K were obtained. Agreement between our widths and experimental data of Plati?a et al. is within error limits; a discrepancy of a factor of 4 appears in a comparison of our data with those of Kusch.     

Theory of the hot free carrier intraband-absorption coefficient of n-inversion layers

The absorption coefficient K of a quasi two dimensional (2D) hot free electron gas is calculated for the first time as a function of the lattice temperature T, the photon angular frequency w, the carrier density N_s as well as the electron temperature T_e when the carriers are scattered by ionized impurities, acoustic phonons and polar optical phonons. Analytical expressions are derived in the limiting cases of non-degeneracy and degeneracy of the electron system. In the quantum limit ħw/k_BT_e ≳ 1 where the interaction between the electron and the photon is inelastic K sensitively depends on the limiting scattering mechanism showing that the electron motion is completely controlled by the photon field. In the classical limit ħw/k_BT_e ⪡ 1 the absorption decreases proportional to w¹ independent of the limiting scattering mechanism in agreement with the experimental data deduced from far-infrared absorptivity measurements on GaAs heterolayers.     

Optical emission spectroscopic studies on laser ablated TiO2 plasma

Optical emission spectroscopic investigations of the plasma produced during Nd:YAG laser ablation of sintered TiO₂ targets, in oxygen and argon gas environments are reported. The spatial variations of electron temperature (T_e) and electron number density (N_e) are studied. The effect of oxygen/argon pressure on electron temperature (T_e) and electron number density (N_e) is presented. The kinematics of the emitted particles and expansion of plume edge are discussed. Spatio-temporal variations of various species in TiO₂ plasma were recorded and corresponding velocities were calculated. The effect of oxygen pressure on intensity of neutral/ion species and their corresponding velocities is also reported.     

Die Erzeugung von Seriengrenzkontinua mit Hilfe von Gleitfunken zur Absolutmessung im Vakuum-Ultraviolett

A lithium plasma is produced by discharging a 40 kV, 0,3 μF capacitor through a lithium-hydride-capillary (diameter 2 mm, length 20 mm) in vacuum (p～10^?4 Torr). During the first half-cycle (0,6 μs) Bremsstrahlung of Li III is observed in the visible and infrared, and the Lyman series of Li III together with the recombination continuum in the vacuum UV (100 Å). The high members of the Lyman series are broadened by Stark effect giving an electron density of about 6 · 10¹⁸ cm^?3. In the infrared the radiation is emitted from an optically thick plasma at a time when the free-free continuum in the visible is emitted from an optically thin plasma. Temporal development of electron temperatureT _e and electron density N_e has been measured from the absolute intensity in these spectral regions. Typical values ofT _e=230 000° K andN _e 5 · 10¹⁸ cm^?3 e.g. have been obtained. For these values the relaxation time for an ionisation equilibrium is short compared to the observation time. The complete ionisation of Li III has been checked by absorption measurements near 100 A. Thus the absolute intensity of the recombination continuum could be calculated. An experimental arrangement was built to measure simultaneously the time history of the intensity in the vacuum ultraviolet, in the visible, and infrared spectral regions.     

Stark broadening of lines from multiply-charged carbon ions in a high-density arc plasma

Profiles of C(III) and C(IV) lines emitted in the VUV and visible regions from a pulsed arc (N_e=1.5×10¹⁸ cm^-3, T_e=5.3×10⁴K) have been measured with time resolution. The experimental results are in satisfactory agreement with the predictions of electron impact theory for (3-3) and (3-4) transitions for which the energy separation between the upper level and the nearest perturbing level is smaller than the electron thermal energy. For lines from (2-2) transitions for which the plasma is optically thick, damping constants determined experimentally agree with theoretical values within a factor of two.     

3 MeV electron irradiation-induced defects in CuInSe2 thin films

3 MeV electron irradiation induced-defects in CuInSe₂ (CIS) thin films have been investigated. Both of the carrier concentration and Hall mobility were decreased as the electron fluence exceeded 1×10¹⁷ cm⁻². The carrier removal rate was estimated to be about 1 cm⁻¹. To evaluate electron irradiation-induced defect, the electrical properties of CIS thin films before and after irradiation were investigated between 80 and 300 K. From the temperature dependence of the carrier concentration in non-irradiated thin films, we obtained N_D=1.8×10¹⁷ cm⁻³, N_A=1.7×10¹⁶ cm⁻³ and E_D=18 meV from the SALS fitting to the experimental data on the basis of the charge balance equation. After irradiation, a new defect level was formed, and N_T0=1.4×10¹⁷ cm⁻³ and E_T=54 meV were also obtained from the same procedure. From the temperature dependence of Hall mobility, the ionized impurity density was discussed before and after the irradiation.     

Emission characteristics and parameters of tin and CuSbSe2 laser plumes

The emission characteristics and parameters of laser plumes of tin and CuSbSe₂ compound are studied at distances of 1 and 7 mm from the target. The recombination times of singly and doubly charged tin ions are, respectively, 116 and 27 ns at a distance of 1 mm from the target and 148 and 64 ns at a distance of 7 mm. In the case of the CuSbSe₂ compound, the recombination times of antimony and copper ions are determined to be, respectively, 60 and 75 ns at a distance of 1 mm and 707 and 976 ns at a distance of 7 mm. The time-averaged temperatures and concentrations of electrons of the tin laser plasma are determined at a distance of 7 mm from the target (T _e = 0.42 eV and n _e = 2.9 × 10¹⁵ cm^?3), and the same parameters for the laser plasma based on the CuSbSe₂ compound are determined at distances of 1 and 7 mm from the target (T _e = 0.62 eV, n _e = 1.4 × 10¹⁶ cm^?3 and T _e = 0.86 eV, n _e = 8.4 × 10¹⁵ cm^?3).     

Anomalous slowdown of relaxation in an ultracold plasma

Recent experiments by T.C. Killian et al. [Phys. Rev. Lett. 83, 4776 (1999)], in which an ultracold plasma (N _e～2×10⁹ cm^?3, T _e～0.1K, and T _i～10 μK) with anomalously long lifetime of ～100 μs was obtained, are explained based on a previously developed theory. The results of computer simulations of the plasma transition into a metastable state and initial heating of electrons up to several K are presented. An expression earlier obtained for the rate of the metastable plasma recombination agrees with the measured anomalously long lifetime. A conclusion is drawn that the previously predicted new physical object—a metastable overcooled plasma—is realized experimentally.     

Infrared absorption in In-doped degenerate Hg1−xCdxTe

The infrared absorption spectra, including absorption edge spectra and below-gap absorption spectra, were investigated both experimentally and theoretically for an In-doped degenerate HgCdTe sample with an electron concentration N_e = 7.0 × 10¹⁷ cm^-3 for wavelengths 7 μm<L<17 μm at the temperatures 77 K <T< 300 K. The possibility of applying free-carrier absorption theory developed for InSb to HgCdTe is discussed. It is concluded that the virtual crystal approximation works fairly well for HgCdTe and that the two-mode Callen effective charge should be used in the calculation of free-carrier absorption coefficients to account for the two-mode character of the optical phonons of HgCdTe. Good agreement between theory and experiment in the below-gap absorption spectra was obtained. The concentration of ionized impurities was found to be N_imp=3.4 × 10¹⁸ cm^-3. A good account of the behaviour of absorption edge in the light of Burstein-Moss effect has also been given.