Variation Of Electron Temperature Research Articles

Variations of electron density and temperature in ionosphere based on the DEMETER ISL data

Observations of the Langmuir Probe Instrument (ISL, Instrument Sonde de Langmuir) onboard the DEMETER satellite during four years from 2006 to 2009 were used to analyze the tempo-spatial variations of electron density (Ne) and temperature (Te) in the ionosphere. Twenty four research bins with each covering an area with 10° in longitude and 2° in latitude were selected to study the spatial distributions of Ne and Te. The results indicate that both Ne and Te have strong annual variations in the topside ionosphere at 660 km altitude. The semiannual anomaly and equinoctial asymmetry which are usually well known as the features of F-layer also exist in the topside ionosphere at low- and mid-latitudes. The yearly variation of Ne is opposite to the peak electron density of the F2-layer (NmF2) at higher latitudes in daytime and both are similar in nighttime. Also the yearly variations of Te at low-latitude are contrary to that at 600 km in daytime and similar in nighttime. An interesting feature of nighttime Te at low-latitude is an obvious annual variation in the northern hemisphere and semiannual variation in the southern hemisphere. The yearly variations of Te in daytime have negative and positive correlation with Ne at mid- and high-latitudes, respectively. Both Ne and Te in the neighborhood bins at the same latitude have a high correlation. In ionospheric events analyzing, this information may help to understand the characteristics of the variation and to distinguish the reliable abnormality from the normal background map.

Time-resolved imaging of millimeter waves using visible continuum from the positive column of a Cs–Xe dc discharge

We present a high-sensitivity technique for time-resolved imaging of millimeter waves (MMWs) using the visible continuum (VC) from the positive column (PC) of a medium-pressure Cs–Xe dc discharge. For the MMW imaging application, a uniform plasma slab of the PC of a Cs–Xe discharge with 10×8 cm2 aperture and 2 cm in thickness was generated for 45 Torr xenon. The imaging technique is based on the fact that the intensity of the e-Xe bremsstrahlung continuum from the PC increases in the visible region when the electrons in the plasma are heated by MMWs. It is shown that in the MMW intensity range from zero to the threshold of the microwave-induced plasma breakdown, the intensity of the VC from the PC of a Cs–Xe discharge increases approximately as a second-order polynomial function of the MMW intensity. The obtained experimental data agree well with our calculations of the dependence of the VC intensity on electron temperature. The Ka-band MMW field patterns at the output of conical horn antennas and in the quasioptical beam were imaged using the discharge technique. It is shown that the technique can be used for time-resolved measurement of the profiles of watt- and subwatt-level MMWs. An energy flux sensitivity of the technique of about 10 μJ/cm2 in the Ka-band was demonstrated. The temporal resolution of the technique is about 0.8 μs. Our modeling of the transient behavior of the electron temperature in the PC shows that the time history of the electron temperature variation coincides well with the measured time history of the VC intensity variation.

Spectroscopic studies of laser ablated ZnO plasma and correlation with pulsed laser deposited ZnO thin film properties

AbstractIn this paper, measurement of various plasma parameters during pulsed laser deposition of ZnO thin films on Si (100) substrates is reported. The variations of electron number density and electron temperature with ambient pressure and target substrate distance is obtained via spectroscopic measurements. The structural and optical properties of ZnO thin films were analyzed using X-ray diffraction, scanning electron microscope, and photoluminescence and then correlated with spectroscopic results to find optimum conditions for the deposition of high quality ZnO thin films.

Spatially Resolved Spectroscopic Study of Arcjet Helium Plasma Expanding through a Rectangular Converging and Diverging Nozzle

An arcjet discharge device with a rectangular converging and diverging nozzle was developed, which allowed us to optically observe high-density plasma inside the anode nozzle. Spectroscopic observation along the plasma expansion axis was carried out to examine the characteristics of the arc plasma inside the nozzle. Analyzing intense continuum and line emission spectra, we successfully obtained spatial variations in electron temperature and density. Moreover, we found that two-dimensional optical measurement is highly useful in visualizing the transition from atmospheric thermal plasma to a strongly nonequilibrium recombining plasma due to adiabatic expansion.

Variations of daytime and nighttime electron temperature and heat flux in the upper ionosphere, topside ionosphere and lower plasmasphere for low and high solar activity

A database of the electron temperature ( T e ) comprising of most of the available LEO satellite measurements is used for studying the solar activity variations of T e . The T e data are grouped for two levels of solar activity (low LSA and high HSA), five altitude ranges between 350 and 2000 km, and day and night. By fitting a theoretical expression to the T e values we obtain variation of T e along magnetic field lines and heat flux for LSA and HSA. We have found that T e increases with increase in solar activity at low and mid-latitudes during nighttime at all altitudes studied. During daytime the T e response to solar activity depends on latitude, altitude, and season. This analysis shows existence of anti-correlation between T e and solar activity at mid-latitudes below 700 km during the equinox and winter day hours. Heat fluxes show small latitudinal dependence for daytime but substantial for nighttime.

Overview of results from the National Spherical Torus Experiment (NSTX)

The mission of the National Spherical Torus Experiment (NSTX) is the demonstration of the physics basis required to extrapolate to the next steps for the spherical torus (ST), such as a plasma facing component test facility (NHTX) or an ST based component test facility (ST-CTF), and to support ITER. Key issues for the ST are transport, and steady state high β operation. To better understand electron transport, a new high-k scattering diagnostic was used extensively to investigate electron gyro-scale fluctuations with varying electron temperature gradient scale length. Results from n = 3 braking studies are consistent with the flow shear dependence of ion transport. New results from electron Bernstein wave emission measurements from plasmas with lithium wall coating applied indicate transmission efficiencies near 70% in H-mode as a result of reduced collisionality. Improved coupling of high harmonic fast-waves has been achieved by reducing the edge density relative to the critical density for surface wave coupling. In order to achieve high bootstrap current fraction, future ST designs envision running at very high elongation. Plasmas have been maintained on NSTX at very low internal inductance li ∼ 0.4 with strong shaping (κ ∼ 2.7, δ ∼ 0.8) with βN approaching the with-wall β-limit for several energy confinement times. By operating at lower collisionality in this regime, NSTX has achieved record non-inductive current drive fraction fNI ∼ 71%. Instabilities driven by super-Alfvénic ions will be an important issue for all burning plasmas, including ITER. Fast ions from NBI on NSTX are super-Alfvénic. Linear toroidal Alfvén eigenmode thresholds and appreciable fast ion loss during multi-mode bursts are measured and these results are compared with theory. The impact of n > 1 error fields on stability is an important result for ITER. Resistive wall mode/resonant field amplification feedback combined with n = 3 error field control was used on NSTX to maintain plasma rotation with β above the no-wall limit. Other highlights are results of lithium coating experiments, momentum confinement studies, scrape-off layer width scaling, demonstration of divertor heat load mitigation in strongly shaped plasmas and coupling of coaxial helicity injection plasmas to ohmic heating ramp-up. These results advance the ST towards next step fusion energy devices such as NHTX and ST-CTF.

Electron Temperature Measurement in IR-T1 Tokamak by ECE Diagnostic

A suitable instrument for electron temperature measurement in Tokamak is electron cyclotron emission diagnostic. We used a heterodyne radiometer in Iran-Tokamak-1 (IR-T1) to measure this parameter. This 5 channel system works in Kα-band and has a very fast response time and good resolution frequency for IR-T1 tokamak. This receiver was used outside the Tokamak, perpendicular to Bt, and with second harmonic of X-mode, variation of electron temperature was measured.

Optical emission spectroscopic studies on laser ablated TiO 2 plasma

Optical emission spectroscopic investigations of the plasma produced during Nd:YAG laser ablation of sintered TiO 2 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 TiO 2 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.

Reply to comment on “Diagnostics of 13.56 MHz RF sustained Ar–N2plasma by optical emission spectroscopy” by N. Sadeghi and F.J. Gordillo-Vazquez

)remains constant in equation (5) for all above mentionedparameters. The same is also valid in reference [6].Figure 1 is added in this reply that shows the variationof electron temperature with Ar % in the mixture, whichshows that the trend for variation of electron temperatureis same with Ar % but electron temperature measuredwith Langmuirprobe is slightly greaterthan electrontem-perature calculated with equation (5). Recently this resultis submitted for publication.In this paper, we don’t calculate the rate coefficientsbut used the reported values from references [2,5,6], there-fore, the raised objection is not valid.

Latitudinal variation of the topside electron temperature at different levels of solar activity

A database of electron temperature ( T e ) measurements comprising of most of the available satellite measurements in the topside ionosphere is used for studying the solar activity variations of the electron temperature T e at different latitudes, altitudes, local times and seasons. The T e data are grouped into three levels of solar activity (low, medium, high) at four altitude ranges, for day and night, and for equinox and solstices. We find that in general T e changes with solar activity are small and comparable in magnitude with seasonal changes but much smaller than the changes with altitude, latitude, and from day to night. In all cases, except at low altitude during daytime, T e increases with increasing solar activity. But this increase is not linear as assumed in most empirical T e models but requires at least a parabolic approximation. At 550 km during daytime negative as well as positive correlation is found with solar activity. Our global data base allows to quantify the latitude range and seasonal conditions for which these correlations occur. A negative correlation with solar activity is found in the invdip latitude range from 20 to 55 degrees during equinox and from 20 degrees onward during winter. In the low latitude (20 to −20 degrees invdip) F-region there is almost no change with solar activity during solstice and a positive correlation during equinox. A positive correlation is also observed during summer from 30 degrees onward.

Langmuir probe characterization of laser ablation plasmas

For laser ablation plumes that are significantly ionized, Langmuir probes have proved to be a useful tool for measuring the plume shape, ion energy distribution, and electron temperature. Typically in laser ablation plasmas the flow velocity is supersonic, which complicates the interpretation of the current-voltage probe characteristic. In this paper we describe some recent developments on the application of Langmuir probes for laser ablation plume diagnosis. We have investigated the behavior of the probe when it is orientated perpendicular, and parallel, to the plasma flow, and show how an analytical model developed for plasma immersion ion implantation, can quantitatively describe the variation of the ion current with probe bias for the case when the plasma flow is along the probe surface. The ion signal recorded by a probe in the parallel position is proportional to the ion density and the square root of the bias voltage. It is shown that the current varies as mi−1/2 so that by comparing the ion signals from the parallel and perpendicular positions it is possible to estimate the mass of the ions detected. We have also determined the temporal variation of electron temperature. A planar probe oriented parallel to the plasma flow, where the ion current due to the plasma flow is eliminated, gives a more reliable measurement of Te (<0.6 eV). The measured Te is consistent with the measured ion current, which is dependent on Te when the time taken for an element of plasma to traverse the probe is longer than the time taken for the matrix ion sheath extraction phase.

Spectroscopic study on rotational and vibrational temperature of N2 and N2+ in dual-frequency capacitively coupled plasma

By using optical emission spectroscopy, the vibrational and rotational temperatures of N2 and N2+ in capacitively coupled plasma (CCP) discharges driven by dual-frequency 41MHz and 2MHz are investigated. The vibrational and rotational temperatures are measured based on the N2+ first negative system and N2 second positive system overlapped molecular emission optical spectrum, using the method of comparing the measured and calculated spectra with a least-square procedure. The influence of the rotational and vibrational temperatures with input power of the high frequency (HF) and low frequency (LF) as well as the gas pressure is discussed. It is found that the vibrational or rotational temperatures of N2 and N2+ are decoupled in dual-frequency CCP discharge. The influence of the LF power on N2+ rotational and vibrational temperature is much more than that of N2, while the influence of HF power is just opposite to the case of LF power. The reason for this is thought to be the variation of electron temperature when applying HF or LF power. Additionally, the increase of gas pressure makes the difference between the vibrational and rotational temperature decrease.

Electron temperature fluctuations in NGC 346

Context. The existence and origin of large spatial temperature fluctuations in H ii regions and planetary nebulae are assumed to explain the differences between the heavy element abundances inferred from collisionally excited and recombination lines, although this interpretation remains significantly controversial. Aims. We investigate the spatial variation in electron temperature inside NGC 346, the brightest H ii region in the Small Magellanic Cloud. Methods. Long slit spectrophotometric data of high signal-to-noise were employed to derive the electron temperature from measurements derived from localized observations of the [O iii](λ4959 + λ5007)/λ4363 ratio in three directions across the nebula. Results. The electron temperature was estimated in 179 areas of 5 �� × 1. �� 5 of size distributed along three different declinations. A largely homogeneous temperature distribution was found with a mean temperature of 12 269 K and a dispersion of 6.1%. After correcting for pure measurements errors, a temperature fluctuation on the plane of the sky of t 2 s = 0.0021 (corresponding to a dispersion of 4.5%) was obtained, which indicates a 3D temperature fluctuation parameter of t 2 ≈ 0.008. A large scale gradient in temperature of the order of −5.7 ± 1.3 K arcsec −1 was found. Conclusions. The magnitude of the temperature fluctuations observed agrees with the large scale variations in temperature predicted by standard photoionization models, but is too small to explain the abundance discrepancy problem. However, the possible existence of small spatial scale temperature variations is not excluded.

Optical emission spectroscopy of atmospheric pressure microwave plasmas

The optical emission behaviors of Ar, He, and Ar+He plasmas generated in air using an atmospheric pressure microwave plasma source have been studied employing optical emission spectroscopy (OES). Emissions from various source gas species and air were observed. The variations in the intensities and intensity ratios of specific emissions as functions of the microwave power and gas flow rate were analyzed to investigate the relationship between the emission behavior and the plasma properties. We find that dependence of the emission behavior on the input microwave power is mainly determined by variations in electron density and electron temperature in the plasmas. On the other hand, under different gas flow rate conditions, changes in the density of the source gas atoms also significantly affect the emissions. Interestingly, when plasma is generated using an Ar+He mixture, emissions from excited He atoms disappear while a strong Hα signal appears. The physics behind these behaviors is discussed in detail.

Physical parameters along the boundaries of a mid-latitude streamer and in its adjacent regions

Context. Coronal streamers appear to be strictly associated with the generation of the slow solar wind, even if a firm identification of the sources of the particle flux within these structures is still an unresolved issue. Aims. The purpose of this work is to contribute to a better knowledge of the physical characteristics of streamers and of their surroundings in a wide range of heliocentric distances and at both high radial and latitudinal resolutions. Methods. The analysis is based on spectral observations of a narrow, mid-latitude streamer performed with UVCS/SOHO during one week in May 2004: H Lyα and O VI resonance doublet line intensities and profiles were obtained at different heliocentric distances and latitudes. In addition, white-light polarized brightness images were taken in the same days of observation, through the LASCO/SOHO C2 coronagraph. Results. The radial variations in electron density and temperature, H I and O VI kinetic temperatures, and outflow velocities were derived from the observed line intensities, profiles, and O VI line intensity ratios between 1.6 and 5.0 R ⊙ , in two regions, 2-3 arcmin wide, located along the boundaries and in a narrow strip (5-10 arcmin) outside the streamer structure. Significantly high kinetic temperatures and outflow velocities were found in the out-of-streamer region above 3.0 R ⊙ for the Ovi ions and, for the first time, Hi atoms, compared to those obtained along the streamer boundaries. Moreover, the O VI kinetic temperatures and velocities turn out much higher than the H I ones at any heliocentric distance in all the observed regions. A higher anisotropy is also noticed for the O VI kinetic temperature in the region flanking the streamer. Conclusions. The slow coronal wind is found to flow with significantly different speeds and kinetic temperatures along the boundaries of the streamer and in the out-of-streamer regions at all heights, above 3.0-3.5 R ⊙ . This fact, consistent with previous studies, indicates that two components of slow wind probably form in the observed regions: one originates just above the streamer cusp and flows with velocities a little higher than 100 km s -1 , while the other flows along the open magnetic field lines flanking the streamer with velocities slightly lower than the slow wind asymptotic heliospheric value of ∼400 km s -1 , around 5.0 R ⊙ .

Experimental study on parameters of dust plasma in SiH4/C2H4/Ar discharges

Measurements of dust plasma parameters were carried out in the discharges of (SiH4/C2H4/Ar) mixtures. Dust particles were formed in the capacitively coupled radio-frequency discharge of these reactive mixtures in a cylindrical chamber. Langmuir probe was employed for diagnosing and measuring the important plasma parameters such as electron density and electron temperature. The results showed that the electron density dropped, and in contrast the electron temperature rose when the dust particles formed. The curves of the electron density and temperature versus the RF power and pressure were presented and analysed. Further, it was found that the variations of electron temperature and the size of dust void with the RF power followed the similar trends. These trends might be useful for understanding more about the characteristics of dusty voids.

Diurnal, seasonal, latitudinal and solar cycle variation of electron temperature in the topside F-region of the Indian zone ionosphere

Abstract. Electron temperature Te observed by the SROSS C2 satellite at equatorial and low latitudes during the low to high solar activity period of 1995–2001 at the height of ~500 km is investigated in terms of local time, season, latitude, solar sunspot number Rz and F10.7 cm solar flux. The satellite covered the latitude belt of 31° S–34° N and the longitude range of 40°–100° E. The average nighttime (20:00–04:00 LT) Te varies between 750–1200 K and then rises sharply in the sunrise period (04:00–06:00 LT) to the morning high from 07:00 to 10:00 LT and attains a daytime (10:00–14:00 LT) average of 1100–2300 K. The morning enhancement is more pronounced in the equinoxes. A secondary maximum in Te is also observed around 16:00–18:00 LT in the June solstice and in the equinoxes. Daytime electron temperature was found to be higher in autumn compared to that in spring in all latitudes. Between the solstices, the amplitude of the morning enhancement is higher in winter compared to that in summer. Both day and nighttime Te observed by the SROSS C2 satellite bears a positive correlation with solar activity when averaged on a shorter time scale, i.e. over the period of a month. But on a longer time scale, i.e. averaged over a year, the daytime electron temperature gradually decreases from 1995 till it reaches the minimum value in 1997, after which Te again continues to rise till 2001. The variations are distinctly seen in summer and in the equinoxes. The sunspot activity during solar cycle 23 was minimum in 1996 and maximum in 2000. Annual average electron temperature, therefore, appears to follow the variation of solar activity with a time lag of about one year, both at the bottom and top of solar cycle 23, indicating an inherent inertia of the ionosphere thermosphere regime to variations in solar flux.

Hot carrier photoluminescence in InN epilayers

The energy relaxation of electrons in InN epilayers is investigated by excitation- and electric field-dependent photoluminescence (PL). From the high-energy tail of PL, we determine the electron temperature of the hot carriers. It was found that the electron temperature variation can be explained by a model in which the longitudinal optical (LO)-phonon emission is the dominant energy relaxation process. The LO-phonon lifetime is fitted to be 0.89 ps, which is higher than the theoretical phonon lifetime. This deviation is attributed to the presence of the non-equilibrium hot-phonon effects.

Rocket observations of propagating waves in the night time equatorial F-region over Brazil

A Brazilian SONDA III rocket carrying plasma diagnostic experiments was launched from the Brazilian rocket launching stations in Alcântara (2.31°S, 44.4°W Geog. Lat.) to measure the height profiles of electron density, electron temperature and the ambient electric field. High frequency capacitance probe was used to measure the height profile of the electron density and the Langmuir probe was used to measure the electron density and the spatial structures of plasma irregularities. An electric field double probe was used to measure the electric field fluctuations associated with the F-region plasma irregularities. Spectral analysis of the fluctuations in electron density and electric field indicated the presence of propagating waves in the night time F-region over a large height range. The electron temperatures estimated from the LP data showed abnormally high values in the base of the F-region during the upleg of the rocket and practically normal values in the same height region during the downleg. A brief study of the characteristic features of the spectra of electron density and electric field fluctuations and the associated electron temperature variations are presented and discussed here.

Effect of recombination and ionization on the analysis of Mach and single probes in un-magnetized and magnetized plasmas of MAP-II and DiPS devices

For the analysis of atomic processes such as recombination and ionization in the divertor plasmas, we have developed a fast-scanning multiple probe system, which is composed of single, Mach and emissive probes along with Thomson scattering system at the material and plasma (MAP)-II divertor simulator with low magnetic field (about 200G). Measured spatial variations of electron density, electron temperature, flow velocity and plasma potential will be given in comparison with those by Thomson scattering method. To analyze the data, a new fluid model on the ion collection to a probing object in un-magnetized plasmas is developed including electron–ion recombination, molecular activated recombination and ionization. This system is applied to another divertor simulator, divertor plasma simulator (DiPS), with higher magnetic field (up to 2kG).