Two-dimensional Electron Temperature Research Articles

Optical emission spectroscopy of fiber laser sustained Xe plasma

Laser-sustained plasma (LSP), a unique method of obtaining high brightness broadband light sources, has been used for rapid optical inspection of wafer defects and has thus attracted great interest. Then Xe plasma sustained under high pressure by a continuous fiber laser was investigated using optical emission spectroscopy (OES). Emission spectra of spatial integration diagnosis have shown that with the increase of laser power and the decrease of Gaussian beam focusing number F, the electron temperature fitted by Boltzmann plot method increased from 0.45 eV to 0.85 eV, the corresponding electron density was roughly an order of magnitude of 1016-1017 cm-3, and the calculated absorption coefficient of plasma was distributed in 0.9–1.5 cm-1. To further analyze the spatial distribution of plasma parameters, the spatial resolved OES of LSP was acquired, and the two-dimensional electron temperature and electron density were determined. The non-uniform distribution of the plasma parameters was analyzed due to the existence of thermal gravity convection and forced convection. The serious self-reversal of emission lines of 881.94 nm and 823.16 nm was observed and analyzed.

Two-dimensional electron temperature and density profiles of Hall thruster plume plasmas using tomographically reconstructed optical emission spectroscopy

Two-dimensional electron temperature and density profiles in the plume region of 300 W-class Hall thruster Ar plasmas were obtained using tomographically reconstructed optical emission intensity profiles combined with a collisional-radiative (CR) model. A total of 1242 lines of sight were used by rotating the thruster to apply inverse Radon transform-based tomographic reconstructions and Abel inversion. The reconstruction accuracy of the developed diagnostic system was evaluated using a priori images derived from plasma pictures, and the reconstruction error was less than 1% in the region of interest, exhibiting higher accuracy than the Abel inversion. From the Ar Hall thruster plasma, more than 12 different two-dimensional profiles of Ar I emission intensity within a spectral range of 600–1000 nm were obtained 6 mm from the exit plane of the thruster. A CR model using 31 allowed transitions at 15 different states from the ground state to the 2p i states was incorporated with the tomographically reconstructed emission intensity sets. Consequently, two-dimensional electron temperature and density profiles in the range of 5–18 eV and 2.0 × 1016–4.7 × 1017 m−3 were obtained, respectively, exhibiting reasonable agreement with the double Langmuir probe measurements.

A spectral clustering based method for automatic plasma pattern identification in electron cyclotron emission imaging on EAST Tokamak

Electron cyclotron emission imaging (ECEI) diagnostic system of Experimental Advanced Superconducting Tokamak (EAST) can provide two-dimensional electron temperature fluctuation on the cross section of the EAST Tokamak. A major task in ECEI data analysis is to recognize patterns in ECEI signals. In this paper, we present a machine learning method to automatically identify the temporal and spacial location of plasma patterns inside ECEI data of EAST tokamak. The method is based on spectral clustering of ECEI signals of different channels. It is applied to ECEI data of 5 discharges obtained from EAST tokamak and the results can verify the effectiveness of our method. Theoretically it can be applied to recognize patterns in many temporal and spacial diagnostics.

Temporal evolution of two-dimensional electron temperature and ion flux on a substrate in a pulsed-power inductively coupled plasma

The two-dimensional temporal behavior of plasma was investigated at the wafer-level when applied power was turned on/off, which is one cycle of the pulsed plasma. For the measurement of transient plasma, the floating harmonic method and a post-processing method were used to obtain the ion flux and the electron temperature with a 1 ms time resolution. The results show that the transient behaviors of plasma such as antenna power absorption are observed in pulsed inductively coupled plasma. Antenna-shaped ion flux is observed when the power is turned on, and the radial profiles of the ion flux are followed by a diffusion solution when the power is turned off. Furthermore, the electron temperature shows pulsed plasma characteristics.

Two-Dimensional Electron Temperature and Density Measurement during Strong Guide-Field Reconnection by using Slide-Type Thomson Scattering System

Two-Dimensional Electron Temperature and Density Measurement during Strong Guide-Field Reconnection by using Slide-Type Thomson Scattering System

Two-Dimensional Distribution of Electron Temperature in Ergodic Layer of LHD Measured from Line Intensity Ratio of CIV and NeVIII

Two-dimensional distribution of impurity lines emitted from ergodic layer with stochastic magnetic field lines in Large Helical Device (LHD) has been observed using a space-resolved extreme ultraviolet (EUV) spectrometer. The two-dimensional electron temperature distribution in the ergodic layer is successfully measured using the line intensity ratio of Li-like NeVIII 2s-3p ( 2 S1/2- 2 P3/2: 88.09 A, 2 S1/2- 2 P1/2: 88.13 A) to 2p-3s ( 2 P1/22 S1/2: 102.91 A, 2 P3/2- 2 S1/2: 103.09 A) transitions emitted from radial location near Last Closed Flux Surface (LCFS). The intensity ratio analyzed with ADAS code shows no dependence on the electron density below 10 14 cm −3 . The result indicates a little higher temperature, i.e., 220 eV, in the poloidal location at high-field side near helical coils called O-point compared to the temperature near X-point, i.e., 170 eV. The electron temperature profile is also measured at the edge boundary of ergodic layer using the line intensity ratio of Li-like CIV 2p-3d ( 2 P1/2- 2 D3/2: 384.03 A, 2 P3/2- 2 D5/2: 384.18 A) to 2p-3s ( 2 P1/2- 2 S1/2: 419.53 A, 2 P3/2- 2 S1/2: 419.71 A) transitions. The intensity ratios analyzed with CHIANTI, ADAS and T.Kawachi codes show a slightly higher temperature near O-point, i.e., 25 eV for CHIANTI, 21 eV for ADAS and 11 eV for T.Kawachi’s codes, compared to the temperature at X-point, i.e., 15 - 21 eV for CHIANTI, 9 - 15 eV for ADAS and 6 - 9 eV for T.Kawachi codes. It suggests that the transport coefficient in the ergodic layer is varied with three-dimensional structure.

Energetic study of the transition to nonlinear state in two-dimensional electron temperature gradient fluid turbulence

Eigenmode projection has been used in analysis of the two-dimensional numerical solution of electron temperature gradient (ETG) turbulence. The secondary Kelvin–Helmholtz instability (KHI) that breaks up the primary ETG structure at the onset of saturation is found to be associated with strong excitation of damped eigenmodes and strong energy damping. While the KHI structure induces some fine scale motions, which can be dissipated by collisional damping, the structure also damps directly at low poloidal wavenumbers through stable eigenmodes. The latter process is persistent in time, while the former occurs only transiently at the initial breakdown of the linearly dominant ETG structure. The persistence of energy damping by stable eigenmodes during and after the transition is enabled by nonlinear advection of electron pressure. Thus, KHI in this system couples with electron pressure advection to generate a dissipative structure at low poloidal wavenumber.

HT-7 Multipoint Nd Laser Thomson Scattering Apparatus

A compact, low cost, multipoint Thomson scattering diagnostic system for HT-7 superconducting tokamak has been in operation since 1999. Its capability of measuring electron temperatures is in the range of 200 eV to 2 keV at a density of a few times 1012 cm-3, with a spatial resolution of 2.4 cm for 5 spatial points and a temporal resolution of 1 ms similar 1 s for 8 time points. The main components of the diagnostic system include a 20-25 J Nd:glass laser with 35 ns pulse width (8 pulses per burst), a KDP frequency-doubling unit, spherical mirrors of multipass input optical system, a wide-angle collection objective, a bandpass glass filter for reducing the stray light to zero, a f/2.5 polychromator, a fiberglass collimator, a photomultiplier's box with electronic preamplifier, high gain and high signal/noise ratio, CAMAC data acquisition and so on. The multipass optical system has been successful at increasing the quantity of scattered photons by passing the probing laser beam 10 times through the plasma under investigation. The HT-7 Thomson scattering diagnostic has provided successfully the information on two-dimensional electron temperature in the plasma of HT-7 tokamak with LHCD and IBW.

Spectroscopic Characterization of an Argon-NeonZ-Pinch Plasma at Stagnation

The density, temperature, and radiation coupling are investigated in strongly radiating Ar-Ne $Z$-pinch plasmas at stagnation using a novel high resolution space- and time-resolving x-ray spectrometer. One- and two-dimensional electron temperature profiles are obtained from the slope of the Ne recombination continuum. The electron density and ion temperature are determined from comparisons of the heliumlike Ar Rydberg series with detailed line-profile calculations. 2D nonlocal thermodynamic equilibrium calculations predict a radiating region denser and cooler than measured.

Temperature and density measurements in a non-axisymmetric, continuously operating fusion experiment using a heavy ion beam probe

Two-dimensional electron temperature and density data have been obtained in the midplane of the non-axisymmetric magnetic confinement device ELMO Bumpy Torus (EBT) through the use of a heavy ion beam probe. This beam probe differs from others operated on toroidal or open magnetic geometries in its combination of complete computer control with the steady-state nature of EBT which allows, under normal operating conditions, for extensive calibration of the system in situ, minimizing both alignment and acquisition errors, along with the use of synchronous detection to dramatically improve the quality of the detected signal over what is typically possible in fast pulse devices. These techniques are important and applicable to long pulse devices where the beam probe may be an ideal diagnostic to measure, for example, parameters of the edge plasma. While the EBT beam probe was implemented to obtain profiles of plasma space potential, we have found that it can also be used effectively to measure the temperature and density profiles in the midplane between magnetic field coils. The data obtained support the contention that the formation of a hollow temperature profile in the T-Mode sufficiently inverts the plasma pressure such that stability of the core plasma would be expected even without diamagnetic effects from the hot electron rings which have previously been considered essential.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Diffusion effects in short-channel GaAs MESFETs

Diffusion effects in short-channel GaAs MESFETs are studied using a two-dimensional electron temperature simulation. A structure that consists of two n +− n contacts on a thin channel region was used as a test vehicle for the study. This structure was found to have a higher cutoff frequency than conventionally doped devices with the same gate length due to decreased gate capacitance and a selective modulation of the device transconductance. These results suggest that the performance of short-channel microwave MESFETs may be influenced strongly by electron diffusion.

The effect of drain bias upon frequency response in GaAs MESFETs

An explanation of the degradation of the frequency response of GaAs MESFETs with drain bias based on the basis of monotonic decrease in saturation velocity at large electric field strength is presented. Device simulations made using the two-dimensional electron temperature model show the current cutoff frequency decreasing with an increase of drain-source voltage in a manner similar to that observed for laboratory devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>