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.     

Cover Picture: Contrib. Plasma Phys. 10/2014

Spatio‐temporal evolution of electron density at 6 microseconds under f = 20 kHz, ε_r = 9.0, RC = 5.0 × 10^–6 cm³ s^–1 and V_appl = 1.7 kV with 50 ppm N₂ impurities in He‐N₂ gas. (Figure 3e of the paper by M.M. Iqbal and M.M. Turner)     

Cover Picture: Contrib. Plasma Phys. 9/2014

Spatio‐temporal evolution of electron density at 6 microseconds under f = 20 kHz, ε_r = 9.0, RC = 5.0 × 10^–6 cm³ s^–1 and V_appl = 1.7 kV with 50 ppm N₂ impurities in He‐N₂ gas. (Figure 3e of the paper by M.M. Iqbal and M.M. Turner)     

A monte-carlo/molecular dynamics study of the diffusional recombination kinetics of C(a) + O(a) → CO(g) on Pt(111)

The diffusion constants for C and O adsorbates on Pt(111) surfaces have been calculated with Monte-Carlo/Molecular Dynamics techniques. The diffusion constants are determined to be D_C(T)=(3.4 × 10^?3e^{$\text{?13156}\text{T}$})cm²s^?1 for carbon and D_O(T) = (1.5×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1 for oxygen. Using a recently developed diffusion model for surface recombination kinetics an approximate upper bound to the recombination rate constant of C and O on Pt(111) to produce CO_(g) is found to be (9.4×10^?3 e^{$\text{?9089}\text{T}$}) cm² s^?1.     

脉冲电容器用细电滞回线铁电陶瓷材料的研究

采用低锆区的Pb(Zr_0.42Sn_0.40Ti_0.18)O₃(PZST42/40/18)铁电陶瓷为基, 通过少量La和Ba取代Pb同时Nb取代(Zr, Sn, Ti)复合取代的方法得到掺杂PZST42/40/18细电滞回线铁电陶瓷, 其最大极化强度P_max≈20.66μC/cm², 剩余极化强度P_r≈0.55μC/cm^{关键词： 细电滞回线 铁电陶瓷 PZST 脉冲电容器}     

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.     

Absolute cross sections of electron attachment to molecular clusters. Part II: Formation of (H2O) N? , (N2O) N? , and (N2) N?

Absolute cross sections σ⁻(E, N) of electron attachment to clusters (H₂O) _N , (N₂O) _N , and (N₂) _N for varying electron energy E and cluster size N are measured by using crossed electron and cluster beams in a vacuum. Continua of σ⁻(E) are found that correlate well with the functions of electron impact excitation of molecules’ internal degrees of freedom. The electron is attached through its solvation in a cluster. In the formation of (H₂O) _N ⁻ , (N₂O) _N ⁻ , and (N₂) _N ⁻ , the curves σ⁻(N) have a well-defined threshold because of a rise in the electron thermalization and solvation probability with N. For (H₂O)₉₀₀, (N₂O)₃₅₀, and (N₂)₂₆₀ clusters at E = 0.2 eV, the energy losses by the slow electron in the cluster are estimated as 3.0 × 10⁷, 2.7 × 10⁷, and 6.0 × 10⁵ eV/m, respectively. It is found that the growth of σ⁻ with N is the fastest for (H₂O) _N and (N₂) _N clusters at E → 0 as a result of polarization capture of the s-electron. Specifically, at E = 0.1 eV and N = 260, σ⁻ = 3.0 × 10⁻¹³ cm² for H₂O clusters, 8.0 × 10⁻¹⁴ cm² for N₂O clusters, and 1.4 × 10⁻¹⁵ cm² for N₂ clusters; at E = 11 eV, σ⁻ = 9.0 × 10⁻¹⁶ cm² for (H₂O)₂₀₀ clusters, 2.4 × 10⁻¹⁴ cm² for (N₂O)₃₅₀ clusters, and 5.0 × 10⁻¹⁷ cm² for (N₂)₂₆₀ clusters; finally, at E = 30 eV, σ⁻ = 3.6 × 10⁻¹⁷ cm² for (N₂O)₁₀ clusters and 3.0 × 10⁻¹⁷ cm² for (N₂)₁₂₅ clusters. Original Russian Text ? A.A. Vostrikov, D.Yu. Dubov, 2006, published in Zhurnal Tekhnicheskoĭ Fiziki, 2006, Vol. 76, No. 12, pp. 1–15.     

Temperaturen in Ionenlaserplasmen

Plasma temperatures of the wall-stabilized low pressure Ar-arc, which has been optimized for maximum inversion density of the Ar II 4p- 4s laser transitions (i.e.kT _e?4 eV), have been determined experimentally and compared with literature data. Ion temperature is obtained from the Doppler linewidths of Ar II transitions, which have been measured both spectroscopically and indirectly by measuring the gain of the 4880 å laser line. Neutral temperature is obtained from the Doppler linewidths of Ar-I-transitions and by relating fill pressure and calculated values of the corresponding gas density. Ion- and neutral temperature are reported to reach values ofT _i? 30000 K andT _a? 25 000 K, respectively. In the range under present concern (kT _e?4 eV, 15≦jR [A cm^?1]≦150)T _i as well asT _a is a function of the characteristic parameterjR alone (j=current density,R=tube radius).     

Untersuchungen zum Existenzbereich einer BOLTZMANN-Verteilung im Argonbogenplasma

Using as plasma source a wall stabilized argon arc working within a restricted parameter range (inner tube diameter = 7 mm, pressure = 30–120 Torr, current = 5-20 A)) the existence of a Boltzmann equilibrium between spectral energy levels is checked by comparing measured occupation number densities of higher excited levels (N_{m, exp}) with the corresponding number densities calculated under the assumption of Boltzmann equilibrium (N_{m, calc}). The methods for determination of the quantities N_{m, exp'} T_g (2300–5405°K), T_e (7170–9950°K) and N_e (0.33 – 2.4 × 10¹⁵ cm^?3) needed for this comparison are described. It can be shown within the limit of experimental error that a Boltzmann equilibrium exists at least for electron densities of N_e > 3 · 10¹⁴ cm^?3. The problem of energy balance of that type of arcs used in these experiments is discussed.     

Acoustic perturbations in a pulsedRF-plasma

The response of a stationary weakly ionized plasma to a density perturbation in the neutral gas component was studied in a neon plasma with the following typical properties: electron density ¯N _e≈8×10¹² cm^?3, electron temperature on the axis of the vesselT _e0≈3.0 eV; neutral gas densityN _n≈1×10¹⁷cm^?3 and neutral gas temperatureT _n0≈600 °K. A neutral density perturbation, generated 50 cm apart from the plasma, produces a fluctuation in the ion density and a sharp spike in the differential voltage of a floating double probe. The experimental observations demonstrate the propagation of an ion sheath and of an electric field perturbation together with the neutral density perturbation. An interpretation of the plasma response to acoustic wave pulses has been proposed by Ingard and Schulz in a theory on acoustic wave modes in a weakly ionized gas. The experimental results are in good agreement with the theoretical expectations.     

Influence of Plasma Resistance and Fluctuation on Probe Characteristics in Detached Recombining Plasmas

In order to find the causes of the strong anomaly of current‐voltage characteristics of Langmuir probe observed in detached recombining plasmas in a linear divertor plasma simulator, NAGDIS‐II, we have investigated plasma resistance along a magnetic field and potential fluctuations in the detached recombining plasmas. Simple calculation on the ratio between the plasma length, at which plasma resistance and resistance of ion sheath formed around a probe tip become equal, and an electron collection length indicates that the evaluation of electron temperature T_e becomes inaccurate at T_e of less than 0.6 eV when plasma density and neutral pressure are 1.0 × 10¹⁸ m^—3 and 10 mtorr, respectively. The potential fluctuation in detached recombining plasmas was found to be so large compared to T_e/e, which can also modify the probe characteristics.     

Measurements of Flow Velocity in the Plasma Generator PSI‐2

The plasma flow velocity in the Plasma Generator PSI‐2 has been investigated by using of Mach probe. PSI‐2 is a stationary high‐current arc discharge in which the quasi‐neutral plasma expands along the magnetic field lines. The low‐temperature (T_e < 20 eV), medium density (n_e ∼ 10¹⁸— 10¹⁹ m^—3 ) plasma in the discharge is similar to the plasma in the divertor region of tokamaks. From the ratio of ion saturation currents collected from opposite sides of the probe the flow velocities (Mach numbers) in argon and hydrogen discharges are obtained.     

Recombination measurements at low energies with Ar16+ and Ar18+ ions in a dense, cold electron target

Recombination of multiply charged ions with electrons at very low relative energies has become a major topic of interest, due to the observation of rates which are enhanced beyond the expectations for radiative recombination. We present results for Ar¹⁶⁺ and Ar¹⁸⁺ ions from systematic measurements along the argon isonuclear sequence using a high density cold electron beam target (n_e = 7 × 10⁹ cm^-3) at the UNILAC of GSI. The transverse and longitudinal temperatures of the electron beam were determined from DR resonance features observed with metastable Ar¹⁶⁺ (2³S) ions. The rate at E_rel = 0 for radiative recombination of completely stripped Ar¹⁸⁺ calculated with electron beam temperatures kT_∥ = 0.002 eV, kT_⊥ = 0.2 eV amounts to α = 10^-9 cm³ s^-1. This is exceeded by nearly a factor of 10 by the rate measured in experiments with Ar¹⁸⁺ ions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Generation and characterization of a bright X-ray source using picosecond laser

High-resolution soft X-ray spectra of H-like and He-like ions were produced from laser irradiated silicon and aluminum targets. Plasma size was about 100 μm. X-ray spectra were analyzed to determine plasma parameters. We compared the line shape of resonance transitions and their intensity ratios to corresponding dielectronic satellites and the intensities of the inter combination lines of He-like ions, with the results of model calculations. Such comparison gave average values of the electron density N _e=(1?1.9)×10²¹ cm^?3 and the electron temperature T _e=460–560 eV for Si plasmas and about 560 eV for Al plasmas produced by the first and the second laser harmonics. According to our estimations, more than 10¹² photons were produced within the resonance line spectral width and in the solid angle 2π steredian during the total decay period.     

Electron temperature (T e) measurements by Thomson scattering system

Thomson scattering technique based on high power laser has already proved its superoirity in measuring the electron temperature (T _e and density (n _e) in fusion plasma devices like tokamaks. The method is a direct and unambiguous one, widely used for the localised and simultaneous measurements of the above parameters. In Thomson scattering experiment, the light scattered by the plasma electrons is used for the measurements. The plasma electron temperature is measured from the Doppler shifted scattered spectrum and density from the total scattered intensity. A single point Thomson scattering system involving a Q-switched ruby laser and PMTs as the detector is deployed in ADITYA tokamak to give the plasma electron parameters. The system is capable of providing the parameters T _e from 30 eV to 1 keV and n _e from 5 × 10¹²cm⁻³−5 × 10¹³cm⁻³. The system is also able to give the parameter profile from the plasma center (Z=0 cm) to a vertical position of Z=+22 cm to Z=−14 cm, with a spatial resolution of 1 cm on shot to shot basis. This paper discusses the initial measurements of the plasma temperature from ADITYA.     

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 Electric Fields Inside a Dense Plasma of a Current Sheet

For the first time there have been analyzed profiles of electric-field-sensitive n_a spectral lines of the Li-like impurity ions CIV, NV, OVI emitted by a hot dense plasma of a plane current sheet. Theoretical profiles of these lines have been calculated with an allowance for Anomalous Electric Fields (AEF). By comparing the experimental and theoretical profiles of the lines it has been established for the first time that in the plane current sheet there were developed AEF of rms strengths F₀ ≈ (100–120) kV/cm in the time interval from τ = ?0.2 μs to τ = 0 (the time τ was counted from the instant of the maximum intensity of the spectral line OVI 5291 Å). These results have been backed up by a similar analysis of the experimental profiles of the spectral line HeII 4686 Å of the primary gas of the discharge. The AEF reached these strengths at the same instant of time, τ = ?0.2 μs, when electron and ion temperatures reached their maxima: T_e ? 100 eV, T_i ≈ 300 eV. The instant τ = ?0.2 μs corresponds to a transition from the metastable stage to the explosive phase of the current sheet evolution. At this time the ratio of the AEF energy density to the thermal energy density of the plasma was § ≡ F²₀/[8π/N_eT_e + N_iT_i)] ≈ 10^?3, which exceeded a similar ratio for the thermal wave field by three orders of magnitude.     

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.     

Electron Temperature Dependence of the Dissociative Recombination Coefficient of Molecular Argon Ions Ar+2 with Electrons

A dual mode (TM₀₁₀ cylindrical cavity/cylindrical waveguide) microwave apparatus is used to study the ion mobility and dissociative recombination of molecular argon ions with electrons in the afterglow period of a d.c. glow discharge as a function of electron temperature when electrons were heated by microwaves up to T_e ≤ 10300K, with T₊ = T_gas = 300K. The electron temperature dependence of the total rate coefficient of dissociative recombination may be represented by α (Ar⁺₂) = (8.1 ± 0.5) × 10^–7[300/T_e(inK)]^0.64cm³s^–1 which is in very good agreement with most previous experimental results but not with the recent theoretical calculations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)