Average Electron Temperature Research Articles

VLA H92α and H115β Recombination Line Observations of the Galactic Center HiiRegions: The Sickle (G0.18−0.04) and the Pistol (G0.15−0.05)

The Very Large Array has been used in the CnB and DnC configurations to observe the remarkable Galactic center sources, the Sickle and the Pistol, near l = 018, b = -004. These H II regions have an unusual morphology and may be physically associated with the linear nonthermal filaments at l = 018, which appear to intersect the sources. The H92α (8.31 GHz) and H115β (8.43 GHz) radio recombination lines arising from these sources have been observed with angular resolutions of 6'' and 9'', respectively. In addition, there is a probable detection of the helium line in the Pistol (Y+ ~ 14% ± 6%), while in the Sickle, no helium lines were detected with an upper limit of Y+ ~ 5% (3 σ). A complex velocity field has been observed in both sources. The LSR velocity in the Sickle varies from 0 to 75 km s-1, with an average velocity of ~35 km s-1; the average velocity of the Pistol is ~115 km s-1. The recombination line properties of the Sickle and the Pistol (FWHM line widths, line-to-continuum ratios, β-to-α ratio) are consistent with photoionization from hot stars. The β-to-α line ratio of ~0.35 ± 0.07 over most of the Sickle and Pistol does not differ significantly from the LTE value of 0.28. The average LTE electron temperature, T*e, for the Sickle (~5500 K) is similar to typical Galactic center H II regions, and T*e for the Pistol is somewhat lower (~3600 K). An additional H II component in the line profiles of three regions of the Sickle in which the nonthermal filaments are present suggests that an interaction between the ionized gas and the nonthermal filaments is occurring. The probable detection of He92α in the Pistol and the nondetection in the Sickle may be due to a difference in the radiation field of the ionizing sources.

Langmuir probe study of the charged particle characteristics in an analytical radio frequency-glow discharge. Roles of discharge conditions and sample conductivity

The application of a tuned Langmuir probe to the measurement of the charged particle characteristics of electron number density, ion number density, electron energy distribution function, average electron energy and electron temperature, in an analytical radio frequency (r.f.)-glow discharge is described. Studies focus on the roles of discharge operating conditions and plasma sampling position for conductive (copper) and nonconductive (Macor) samples. Based on the data obtained here, apparent differences in plasma characteristics between conductive and nonconductive samples can be reasonably explained. For example, the sputtering of conductive samples results in plasmas with obviously higher electron and ion number densities than the sputtering of nonconductive samples (e.g. n i = 1.8 × 10 10 cm −3 and n e = 1.5 × 10 9 cm −3 for copper, and n i = 8 × 10 9 cm −3 and n e = 5 × 10 8 cm −3 for Macor under the conditions of argon pressure = 4 Torr, r.f. power = 30 W and sampling distance = 4.5 mm). Conversely, nonconductive samples yield electrons with higher energies (average electron energies of 15 and 7.5 eV and temperatures of 6.5 and 3.5 eV respectively for the Macor and copper samples). Lower d.c. bias potentials for the case of sputtering nonconductive samples yield reduced sputtering rates and charged particle densities, though the electrons in the latter case have higher energies and thus improved excitation capabilities. The differences between r.f.- and d.c.-glow discharge optical emission spectra are also discussed relative to reported electron energy characteristics. Studies such as these will lay the ground-work for extensive evaluation of inter-matrix type standardization for r.f.-glow discharge atomic emission spectrometry.

An optical field-induced ionization X-ray laser using a preformed plasma scheme

Soft X-ray amplification by optical field-induced ionization (OFI) of a preformed plasma is investigated. A small-signal gain of 20 cm/sup -1/ and a gain-length product of 4 at 13.5 nm on the Lyman-/spl alpha/ transition in hydrogen-like lithium have been obtained using the modified OFI scheme. Experimental and numerical results ensure that we have produced a plasma with a significantly lower electron temperature than what is expected by an above-threshold ionization model. To explain the results, a two component plasma model in which relatively high temperature electrons are produced by OFI in a cold electron bath of the preformed plasma is presented. The model indicates that the average electron temperature of the OFI plasma rapidly decreases since a high-temperature part of the electrons escapes from the focal volume without interaction. The initial electrons produced prior to the field ionization, which survive after the OEI, also significantly contribute to the rapid three-body recombination. Based on the ionization-induced refractive index change, the pulse propagation of a high-intensity pump laser during the OFI is also discussed. >

Photon-energy distribution of hot-carrier photoemission from LOCOS and trench-isolated MOSFETs

Two-dimensional (2-D) photon-energy distributions emitted from hot-carriers in LOCOS and trench-isolated CMOS devices with a narrow channel width of about 10 μm are measured. The 2-D photoemission images show different characteristics depending on the photon energy. Relatively large spatial fluctuations of normalized photoemission-intensity profiles for each photon energy are observed, while all the profiles show similar trapezoidal shapes along the channel width direction. Average electron temperatures are about 3700 and 3500 K for n- and p-MOSFETs, respectively, independently of the isolation technologies. Quite characteristic photoemission profiles and 2-D images are observed in trench-isolated n-MOSFETs after high bias-voltage stress.

A detailed investigation of heterojunction transport using a rigorous solution to the Boltzmann equation

A detailed study of electron transport across an Np/sup +/ heterojunction diode is performed using a rigorous numerical solution to the Boltzmann equation. Results are presented for the I-V characteristic and the average electron energy, temperature, energy flux, and quasi-Fermi levels as a function of position. Comparison with a simple analytical treatment shows good agreement for the current and quasi-Fermi level splitting versus bias. The distribution functions near the heterojunction interface are also investigated and found to be distinctly non-Maxwellian. Finally, the results are used to examine the boundary conditions of hydrodynamic quantities at the heterojunction.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modeling electronegative plasma discharges

A macroscopic analytic model for a three-component electronegative plasma has been developed. Assuming the negative ions to be in Boltzmann equilibrium, a positive ion ambipolar diffusion equation is found. The electron density is nearly uniform, allowing a parabolic approximation to the plasma profile to be employed. The resulting equilibrium equations are solved analytically and matched to an electropositive edge plasma. The solutions are compared to a simulation of a parallel-plane rf driven oxygen plasma for two cases: (1) p=50 mTorr, ne0=2.4×1015 m−3, and (2) 10 mTorr, ne0=1.0×1016 m−3. In the simulation, for the low power case (1), the ratio of negative ion to electron density was found to be α0≊8, while in the higher power case α0≊1.3. Using an electron energy distribution that approximates the simulation distribution by a two-temperature Maxwellian, the analytic values of α0 are found to be close to, but somewhat larger than, the simulation values. The average electron temperature found self-cosistently in the model is close to that in the simulation. The results indicate the need for determining a two-temperature electron distribution self-consistently within the model.

Phenomenological modeling of turbulence in Z-pinch implosions

A phenomenological investigation into the effects of magnetohydrodynamic (MHD) turbulence on the initial stagnation dynamics of aluminum wire array and argon gas puff Z-pinch implosions is performed. The increases that turbulence produces in the plasma viscosity, heat conductivity, and electrical resistivity are modeled by using multipliers for these quantities in one-dimensional (1-D) MHD calculations. The major effect of these increases is to soften the 1-D implosions by decreasing the densities that are achieved on axis at stagnation. As a consequence, a set of multipliers can be found that reasonably duplicates the average electron temperatures, ion densities, and mass of the K-shell emission region that were measured at stagnation for a variety of Physics International aluminum wire array and argon gas puff experiments. It is determined that the dependence of these measured quantities on the multipliers is weak once a level of enhancement is reached, where agreement between calculations and experiments is attained. The scaling of K-shell yield with load mass for a fixed implosion velocity is then reexamined, and the minimum load mass needed to efficiently produce K-shell emission by thermalization of kinetic energy is calculated for aluminum and argon using this phenomenological soft implosion modeling. The results show an upward shift in the minimum mass by a factor of 6 when compared to the original nonturbulent hard implosion calculations.

Impurity screening in high density plasmas in tokamaks with a limiter configuration

Impurity screening in high density plasmas in tokamaks with a limiter configuration is investigated by means of a simple semi-analytical model. An iterative scheme is devised, in order to determine self-consistently the values of scrape-off layer thickness, edge electron density and temperature, and main plasma contamination parameter Z eff , as a function of given average electron density and temperature in the main plasma and given input power. The model is applied to the poloidal limiter case of the Frascati Tokamak Upgrade, and results are compared with experimental data. A reasonable agreement between the trends is found, emphasizing the importance of a high edge plasma density for obtaining a clean main plasma in limiter tokamaks.

On the formation and evolution of plasmoids: A survey of ISEE 3 geotail data

ISEE 3 magnetometer and electron plasma measurements from the 1983 Geotail Mission were surveyed to determine the magnetic and plasma properties of plasmoids and their evolution with distance downtail. Events were selected on the basis of a bipolar magnetic signature in either the geocentric solar magnetospheric Bz and/or By component; most had Bz bipolar signatures. We found 366 events consistent with this signature while ISEE 3 was in the plasma sheet. ISEE 3 observed plasmoids all along its trajectory whenever it was in the plasma sheet. Plasmoids are characterized by high‐speed plasma flow. Plasmoid length was determined using both the magnetometer and the electron plasma velocity data. We found the average length of plasmoids is 16.7 ± 13.0 RE, significantly smaller than previous estimates. Many plasmoids have a well‐defined magnetic core field, characterized by a field strength maximum at the center of the pass through the structure. Plasmoids appear to be relatively stable structures once their formation process is complete. The size, velocity, magnetic core strength, and Bz field amplitude of plasmoids do not depend on distance beyond 100 RE downtail. The average electron temperature inside plasmoids drops by a factor of 2 and the electron density increases by a factor of 2 as plasmoids propagate from near Earth distances (within 100 RE of the Earth) to the deep tail. We conclude that the stable size of the plasmoids, the density increase and the temperature decrease are consistent with a flux of cold electrons into the plasmoid. The strong correlation of interplanetary magnetic field By an hour before the event with the strength and direction of By observed inside plasmoids, the existence of events with the bipolar signature in both the By and Bz components, and the possible mass flux all are consistent with plasmoids being “open” magnetic structures.

Dynamical picture of rf current drive phenomena in tokamaks

A dynamical picture of the rf current drive phenomenon is derived according to a Dawson-like treatment of Landau damping instead of the quasilinear theory, in which the parameter dependence of induced current drive efficiency corresponding to the experimental results is estimated. The N∥ dependence indicates that the spectrum gap can be made small for larger temperature, lower density, and higher injected frequency. The drive efficiency is usually proportional to the average electron temperature at the optimized condition. The efficiency increases with density at the lower-density region and decreases with density at the higher-density region. The optimum density for maximum efficiency shifts to the higher-density region with increasing N∥, frequency, and electron temperature. This picture may provide some insight in the understanding of the current drive phenomenon in tokamaks as a zeroth-order approximation.

Simulation of substrate current characteristics of submicron MOSFETs

A method for economical prediction of substrate currents in submicron-scale MOSFETs is described and validated by comparison of simulation and experimental results. Two-dimensional energy transport simulation is used to obtain average electron energies and temperature, and hole transport is described using the standard drift-diffusion method. Relatively little computation time is required to give a physically correct picture of device operation on a SUN 3/60 or equivalent work station.

Plasma evolution from laser-driven gold disks. I. Experiments and results

Gold disk targets were irradiated with green (λ=0.53 μm) laser light at intensities between 0.5 and 5×1014 W/cm2 using shaped laser pulses. Plasma conditions near and below critical density (nc≂4×1021/cm3) were determined from three diagnostics. Streaked one-dimensional images of the M-band emission (2–3.5 keV) along the laser axis yield the peak emission trajectory. Temporally and spatially averaged measurements of the hard x-ray spectrum (4–25 keV) were used to determine the average coronal electron temperature. Holographic interferometry was used to determine the electron density profiles and scale lengths along the laser axis. The peak emission trajectory, electron temperature, and scale lengths are all in good agreement with simulations, but the magnitudes of the electron density profiles are not, as discussed in an accompanying paper [Phys. Fluids B 2, 2448 (1990)].

Self-consistency of the principle of profile consistency results for sawtoothing tokamak discharges

The principle of profile consistency states that for fixed limiter safety factor qa there are unique natural equilibrium profile shapes for the current density j(r) (and consequently q(r)) and the electron temperature Te(r) for any tokamak plasma, independent of the shapes of the heating power deposition profiles. The mathematical statements of the three basic consequences of this principle for sawtoothing discharges (i.e. discharges with q(0) ≤ 1) are: (1) r1/a = F1(l/qa) (≈ 1/qa, empirically); (2) ⟨Te⟩/Te0 = F2(l/qa); and (3) a unique scaling law for the central electron temperature,where q(r1) = 1, ⟨Te⟩ is the volume average electron temperature, and F3(qa) = qa/q0. Since Ohm's law relates j(r) to Te(r), the principle of profile consistency dictates that this unique set of functions F1, F2 and F3 remain the same for all sawtoothing discharges in any tokamak, regardless of its size (i.e. a and R), Ip, VL, BT, etc. The paper presents a rather complete and detailed analysis of this self-consistency of the measured values of Te(r), F1, F2 and F3 for sawtoothing TFTR discharges. In particular, the analytical predictions of the profiles of Coppi's Gaussian, exponential, modified exponential and trapezoidal models, as well as the model profiles of Kadomtsev and Campbell et al. are compared with TFTR and TFR data. Some of the principal results are: (1) The empirical profile consistency relation r1/a = 1/qa is an acceptable solution of q(r1) = 1 for all qa dependent profiles. (2) A comparison between experiment and the present analytic results yields [⟨Te⟩/Te0]EXP ≈ [⟨Te⟩/Te0]AN + 0.05 for the profiles of Coppi's Gaussian model, and for the profiles of the models of Kadomtsev and Campbell et al. (3) For all qa independent profiles, F3(qa) = qa/q0 = constant, and, consequently,for all qa dependent profiles, F3(qa) = qa/q0 ∼ qa when r1/a ≈ 1/qa, and, consequently,.(4) Coppi's and Ohkawa's forms of xe(r) yield,while the INTOR value of xe(r) yields.(5) For r1/a ≈ 1/qa, the profiles of Coppi's Gaussian model and those of the models of Kadomtsev and Campbell et al. all predict that the normalized sawtooth amplitude ΔTe/Te ∼ 1/qa, in agreement with the experimental observations. (6) For qa dependent models, universality of profiles exists in suitably reduced co-ordinates when r1/a ≈ 1/qa.

Investigation of resonance and excimer radiation from a dielectric barrier discharge in mixtures of mercury and the rare gases

The excitation of resonance and excimer radiation in mixtures of mercury and the rare gases has been investigated. The gas mixtures were excited in a dielectric barrier discharge. The emission features of such discharges which are mostly in the UV and VUV range were studied in detail. Whereas resonance radiation dominates in mixtures of mercury with He, Ne, and Ar, efficient excimer formation takes place in mixtures of mercury with Kr and Xe. All the emission features of the HgXe excimer which are expected between and around the resonance lines of mercury were found and measured. A theoretical model of HgXe excimer formation is presented. This model takes both the discharge formation and the charged particle kinetics as well as the excimer and excited species formation into account. Experimentally determined Boltzmann temperatures show a decline with mercury density as is predicted by the theory for the average electron temperature. Furthermore it is, e.g., possible to calculate the efficiency of the generation of the various species observed. Due to the geometrical flexibility and high obtainable power levels, dielectric barrier discharges are very well suited for the generation of UV radiation. Apart from well-established techniques like UV lithography, disinfection, or UV curing, also new techniques in photochemistry such as, e.g., photochemical vapor deposition, profit from these new sources.

Small‐scale plasma, magnetic, and neutral density fluctuations in the nightside Venus ionosphere

Pioneer Venus orbiter measurements have shown that coherent small‐scale waves exist in the electron density, the electron temperature, and the magnetic field in the lower ionosphere of Venus just downstream of the solar terminator (Brace et al., 1983). The waves become less regular and less coherent at larger solar zenith angles, and Brace et al. suggested that these structures may have evolved from the terminator waves as they are convected into the nightside ionosphere, driven by the day‐to‐night plasma pressure gradient. In this paper we describe the changes in wave characteristics with solar zenith angle and show that the neutral gas also has related wave characteristics, probably because of atmospheric gravity waves. The plasma pressure exceeds the magnetic pressure in the nightside ionosphere at these altitudes, and thus the magnetic field is carried along and controlled by the turbulent motion of the plasma, but the wavelike nature of the thermosphere may also be coupled to the plasma and magnetic structure. We show that there is a significant coherence between the ionosphere, thermosphere, and magnetic parameters at altitudes below about 185 km, a coherence which weakens in the antisolar region. The electron temperature and density are approximately 180° out of phase and consistently exhibit the highest correlation of any pair of variables. Waves in the electron and neutral densities are moderately correlated on most orbits, but with a phase difference that varies within each orbit. The average electron temperature is higher when the average magnetic field is more horizontal; however, the correlation between temperature and dip angle does not extend to individual wave structures observed within a satellite pass, particularly in the antisolar region. The importance of fluctuations in the magnetic dip angle is that they inhibit vertical conduction and produce a small effective dip angle which reduces the heat flux necessary to maintain the observed temperatures.

Detection of H53-alpha emission from M82 - A reliable measure of the ionization rate and its implications

view Abstract Citations (63) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of H53 alpha Emission from M82: A Reliable Measure of the Ionization Rate and Its Implications Puxley, P. J. ; Brand, P. W. J. L. ; Moore, T. J. T. ; Mountain, C. M. ; Nakai, N. ; Yamashita, T. Abstract Emission in the hydrogen recombination line H53α has been detected, for the first time, in another galaxy: the nearby "starburst" system M82. This line is produced primarily by spontaneous emission and provides the most direct, extinction-independent estimate of the ionization rate in the star-forming complex. The line strength implies an ionization rate of 1.1 x 10^54^ s^-1^, approximately 5 times larger than that inferred from Brα observations, and indicates a dust extinction at 4 microns of more than 1 mag (A_v_ ~ 27 mag). Comparison of the 3.3 mm free-free continuum and H53α fluxes implies an average electron temperature of T_e_ ~ 5 x 10^3^ K. Analysis of the line excitation conditions, using the H53α emission in conjunction with that in the far-IR O^2+^ and N21 forbidden lines, together with the IR luminosity, suggests that only a very restricted range of stellar masses are formed. Less plausible interpretations are (1) that approximately two-thirds of the direct stellar emission escapes from the central 40" without encountering dust and (2) that much of the line emission and IR luminosity arises via fast (~ 100 km s^-1^) shocks. Publication: The Astrophysical Journal Pub Date: October 1989 DOI: 10.1086/167891 Bibcode: 1989ApJ...345..163P Keywords: Emission Spectra; Interstellar Matter; Irregular Galaxies; Star Formation; Electron Energy; Far Infrared Radiation; Forbidden Bands; Ionization; Recombination Reactions; Stellar Mass; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M82; GALAXIES: INTERSTELLAR MATTER; INTERSTELLAR: GRAINS full text sources ADS | data products SIMBAD (1) NED (1)

Behavior of downstream plasmas generated in a microwave plasma chemical-vapor deposition reactor

The behavior of electron-cyclotron resonant (ECR) and non-ECR H2 plasmas generated in a microwave plasma chemical-vapor deposition reactor have been studied as a function of magnetic field strength and absorbed microwave power. Plasma diagnostics were performed with a planar electrostatic probe, microwave power measurements, and visual inspection. The probe measurements were concerned with the plasma impingent on a sample table placed downstream from the active core of the plasma. ECR plasmas were found to be more efficient, stable, uniform, and dense than plasmas not generated by ECR. All properties of the ECR plasmas measured by the downstream probe showed a gentle monotonic increase with the magnetic field strength. This was attributed to a reduction in the spacing between the probe and the resonant zone. In the ECR plasmas the average electron temperature was 3 eV and the average density was 1016 m−3. The degree of ionization was on the order of 5×10−4.

A new target configuration producing an effective population inversion at energy levels of Mg XI 1s3p and 1s4p

A microtube target with lateral jet nozzle has recently been developed. Strong population inversion was observed along the whole jet nozzle between the energy level of MgXI 1s3p 1P o 0 and that of 1s4p 1P o 0, while the average laser irradiance was around 3.5×10 13 W cm -2 on the inner wall of the microtube targets. A corresponding average electron temperature of 470–520 eV and density of 2×10 20 cm -3 at the inversion area of the plasma medium was measured. Possible mechanisms of the population inversion under the average high temperature condition have been analysed.

POPULATION INVERSION OF ENERGY LEVELS OF MgXI 1s3p AND 1s4p UNDER THE CONDITION OF AVERAGE HIGH TEMPERATURE AND HIGH ELECTRON DENSITY

The microtube target with side jet burner is designed. Strong population inversion is observed along the whole side jet burner between the energy leveles of MgXI Is3p 1P00 and Is4p 1P00 while the average laser irradiance reached about 3.5×1013W·cm-2 on the inner wall of the microtube targets. The corresponding environment average electron temperature 470-520 eV and density of 2×10cm-3 of plasma at the inversion area is measured. The possible mechanisms of population inversion under the average high temperature condition has been analysed.

Simultaneous SMM flat crystal spectrometer and Very Large Array observations of solar active regions

High-resolution images of the quiescent emission from two solar active regions at 20 cm (VLA) and soft X-ray (SMM FCS) wavelengths are compared. There are regions where the X-ray coronal loops have been completely imaged at 20 cm wavelength. In other regions, the X-ray radiation was detected without detectable 20 cm radiation, and vice versa. The X-ray data were used to infer average electron temperatures of about 3-million K and average electron densities of about 2.5 x 10 to the 9th/cu cm for the X-ray emitting plasma in the two active regions. The thermal bremsstrahlung of the X-ray emitting plasma is optically thin at 20 cm wavelength. The 20 cm brightness temperatures were always less than T(e), which is consistent with optically thin bremsstrahlung. The low T(B) can be explained if a higher, cooler plasma covers the hotter X-ray emitting plasma. Thermal gyroresonance radiation must account for the intense 20 cm radiation near and above sunspots where no X-ray radiation is detected.