Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly orient...Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly oriented pyrolytic graphite crystal spectrometer measured the time-integrated spectral distribution of Cu under varying laser intensities.Using the two-dimensional radiation-hydrodynamics code FLASH and the spectral analysis code FLYCHK,we simulated the temporal evolution of plasma density and temperature distributions,as well as the emission intensities of spectral lines at different temperatures and densities.The simulation results revealed that the two-electron satellite lines(J)and the resonance line(W)emissions of Cu originate predominantly from the radiation region near the critical density surface,with a density range from approximately 0.5 nc to 1.0 nc,and radiate primarily during the laser irradiation period.By analyzing the J/W intensity ratio of the measured spectral lines,we estimated the electron temperatures near the critical-density surface under different laser intensities.展开更多
This article provides a short review on the importance of the detailed analysis of a Langmuir probe I-V trace in a multi-Maxwellian plasma,and discuss proper procedures analyzing Langmuir probe I-V traces in bi-Maxwel...This article provides a short review on the importance of the detailed analysis of a Langmuir probe I-V trace in a multi-Maxwellian plasma,and discuss proper procedures analyzing Langmuir probe I-V traces in bi-Maxwellian and triple-Maxwellian Electron Energy Distribution Function(EEDF)plasmas.Discus⁃sion and demonstration of procedures include the treatment of the ion saturation current,electron saturation cur⁃rent,space-charge effects on the I-V trace,and most importantly how to properly isolate and fit for each electron group present in an I-V trace reflecting a mult-Maxwellian EEDF,as well as how having a multi-Maxwellian EEDF affects the procedures of treating the ion and electron saturation currents.Shortcomings of common improp⁃er procedures are discussed and demonstrated with simulated I-V traces to show how these procedures gives false measurements.展开更多
A 100-channel double-foil soft X-ray array imaging(DSXAI)diagnostic system has been developed for the HL-2A tokamak to obtain tomographic bremsstrahlung emissivity and electron temperature(T_(e)).This system employs a...A 100-channel double-foil soft X-ray array imaging(DSXAI)diagnostic system has been developed for the HL-2A tokamak to obtain tomographic bremsstrahlung emissivity and electron temperature(T_(e)).This system employs a double-foil technique to determine T_(e) by comparing the soft X-ray(SXR)emissivities from the same plasma location through two beryllium(Be)foils of differing thickness.The DSXAI system comprises five photocameras mounted at two different poloidal cross-sections,separated toroidally by 15°,allowing for three distinct poloidal viewing angles.Each photocamera features 20 channels,offering a temporal resolution of approximately 4μs and a spatial resolution of about 8 cm,with no channel overlap.Each photocamera contains two identical optical systems,each defined by an aperture slit and a photodiode array.The double-foil configuration is realized by placing these two optical systems,each with a different Be foil,in close proximity.Initial experimental results demonstrate that the DSXAI diagnostic system performs well,successfully reconstructing 2-dimensional(2D)tomographic SXR emissivity and T_(e) on the HL-2A tokamak.This study provides valuable insights for the future implementation of similar diagnostic systems on fusion reactors like ITER.展开更多
In this article, four kinds of optical emission spectroscopic methods of determining electron temperature are used to investigate the relationship between electron temperature and pressure in the cylindrical plasmas o...In this article, four kinds of optical emission spectroscopic methods of determining electron temperature are used to investigate the relationship between electron temperature and pressure in the cylindrical plasmas of dc glow discharges at low pressures in laboratory by measuring the relative intensities of ArI lines at various pressures. These methods are developed respectively on the basis of the Fermi-Dirac model, corona model, and two kinds of electron collision cross section models according to the kinetic analysis. Their theoretical bases and the conditions to which they are applicable are reviewed, and their calculation results and fitting errors are compared with each other. The investigation has indicated that the electron temperatures obtained by the four methods become consistent with each other when the pressure increases in the low pressure argon plasmas.展开更多
Stationary long pulse plasma of high electron temperature was produced on EAST for the first time through an integrated control of plasma shape, divertor heat flux, particle exhaust, wall conditioning, impurity manage...Stationary long pulse plasma of high electron temperature was produced on EAST for the first time through an integrated control of plasma shape, divertor heat flux, particle exhaust, wall conditioning, impurity management, and the coupling of multiple heating and current drive power. A discharge with a lower single null divertor configuration was maintained for 103 s at a plasma current of 0.4 MA, q95 ≈7.0, a peak electron temperature of 〉4.5 keV, and a central density ne（0）-2.5×10^19 m^-3. The plasma current was nearly non-inductive （Vloop 〈0.05 V, poloidal beta - 0.9） driven by a combination of 0.6 MW lower hybrid wave at 2.45 GHz, 1.4 MW lower hybrid wave at 4.6 GHz, 0.5 MW electron cyclotron heating at 140 GHz, and 0.4 MW modulated neutral deuterium beam injected at 60 kV. This progress demonstrated strong synergy of electron cyclotron and lower hybrid electron heating, current drive, and energy confinement of stationary plasma on EAST. It further introduced an example of integrated ＂hybrid＂ operating scenario of interest to ITER and CFETR.展开更多
As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and elec...As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering（LTS） system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5？×10^19m^-3 to7.1？×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy（OES） system was established as well. The results showed that the electron excitation temperature（configuration temperature） measured by OES is significantly higher than the electron temperature（kinetic electron temperature） measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium（LTE）. This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.展开更多
Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are emp...Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.展开更多
The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numeric...The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm [（3s^23p^5）5p →（3s^23p^5）4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm [（3s^23p^5）4p → （3s^23p^5）4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm （N2（C^3Пu →B3Пg）） to 391.4 nm （N2^＋（B2 ∑u^＋→ ∑g^＋））. Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.展开更多
Observation data recorded by the European Incoherent Scatter Scientific Association in TromsФ, Norway in August 2009 were analyzed to determine the heating effects in polar summer ionospheric modification experiments...Observation data recorded by the European Incoherent Scatter Scientific Association in TromsФ, Norway in August 2009 were analyzed to determine the heating effects in polar summer ionospheric modification experiments. There are two types of increases in electron temperature： large relative increases in a narrow range near 150 km and greater absolute increases in a wider range at 150-400 km. The percentage increase in temperature linearly increases with heating power, but the rate of increase decreases with increasing pump frequency. A clear two-dimensional distribution was found for the measurement made on August 15, and the beating effects are greater closer to the direction of the geomagnetic field. The heating effects obviously depend on the angle between the heating beam and geomagnetic field; as the angle increases, the heating effect decreases.展开更多
Based on the theory of plasma continuous radiation, the relationship between the emission intensity of bremsstrahlung and recombination radiation and the plasma electron temperature is obtained. During the development...Based on the theory of plasma continuous radiation, the relationship between the emission intensity of bremsstrahlung and recombination radiation and the plasma electron temperature is obtained. During the development process of a return stroke of ground flash, the intensity of continuous radiation spectrum is separated on the basis of the spectrums with obviously different luminous intensity at two moments. The electron temperature of the lightning discharge channel is obtained through the curve fitting of the continuous spectrum intensity. It is found that electron temperature increases with the increase of wavelength and begins to reduce after the peak. The peak temperature of the two spectra is close to 25 000 K. To be compared with the result of discrete spectrum, the electron temperature is fitted by the O I line and N II line of the spectrum respectively. The comparison shows that the high temperature value is in good agreement with the temperature of the lightning core current channel obtained from the ion line information, and the low temperature at the high band closes to the calculation result of the atomic line, at a low band is lower than the calculation of the atomic line, which reflects the temperature of the luminous channel of the outer corona.展开更多
A new edge tangential multi-energy soft x-ray（ME-SXR） diagnostic with high temporal（≤ 0.1 ms） and spatial（~1 cm） resolution has been developed for a variety of physics topics studies in the EAST tokamak plasma....A new edge tangential multi-energy soft x-ray（ME-SXR） diagnostic with high temporal（≤ 0.1 ms） and spatial（~1 cm） resolution has been developed for a variety of physics topics studies in the EAST tokamak plasma. The fast edge electron temperature profile（approximately from r a~ 0.6 to the scrape-off layer） is investigated using ME-SXR diagnostic system. The data process was performed by the ideal ‘multi-foil＇ technique, with no priori assumptions of plasma profiles. Reconstructed ME-SXR emissivity profiles for a variety of EAST experimental scenarios are presented here for the first time. The applications of the ME-SXR for study of the effects of resonant magnetic perturbation on edge localized modes and the first time neon radiating divertor experiment in EAST are also presented in this work. It has been found that neon impurity can suppress the 2/1 tearing mode and trigger a 3/1 MHD mode.展开更多
An Nd:YAG single pulse nanosecond laser of 532 nm wavelength with an 8 ns pulse width was projected on the soil samples collected from the campus of Bengbu College under 1 standard atmospheric pressure. Laser-induced ...An Nd:YAG single pulse nanosecond laser of 532 nm wavelength with an 8 ns pulse width was projected on the soil samples collected from the campus of Bengbu College under 1 standard atmospheric pressure. Laser-induced breakdown spectroscopy at different sample temperatures was achieved. The intensity and signal-to-noise ratio (SNR) changes of different characteristic spectral lines could be analyzed when the sample temperature changes.The evolution of plasma electron temperature and electron density with the sample temperature was analyzed through Boltzmann oblique line method and Stark broadening method.The cause of the radiation enhancement of laser-induced metal plasma was discussed. Experimental results demonstrated that the spectral intensity, SNR, the electron temperature and electron density of plasma are positively related to the sample temperature, and reach saturation at 100℃.展开更多
In this paper, a low pressure Ar/N2 shock plasma jet with clearly multicycle al- ternating zones produced by a DC cascade arc discharge has been investigated by an emission spectral method combined with Abel inversion...In this paper, a low pressure Ar/N2 shock plasma jet with clearly multicycle al- ternating zones produced by a DC cascade arc discharge has been investigated by an emission spectral method combined with Abel inversion analysis. Plasma emission intensity, electron, vi- brational and rotational temperatures of the shock plasma have been measured in the expansion and compression zones. The results indicate that the ranges of the measured electron temperature, vibrational temperature and rotational temperature are 1.1 eV to 1.6 eV, 0.2 eV to 0.7 eV and 0.19 eV to 0.22 eV, respectively, and it is found for the first time that the vibrational and rota- tional temperatures increase while the electron temperature decreases in the compression zones. The electron temperature departs from the vibrational and the rotational temperatures due to non-equilibrium plasma effects. Electrons and heavy particles could not completely exchange energy via collisions in the shock plasma jet under the low pressure of 620 Pa or so.展开更多
In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the seconda...In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the secondary electron emission in the Hall thruster, by the particle-in-cell （PIC） method. The numerical results show that when the electron temperature is relatively low, the change of sheath potential drop is relatively large, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is relatively high, the surface potential maintains a persistent oscillation, and the stability of the sheath reduces. As the electron temperature increases, the secondary electron emission coefficient on the wall increases. For three kinds of propellants （At, Kr, and Xe）, as the ion mass increases the sheath potentials and the secondary electron emission coefficients reduce in sequence.展开更多
Effects of electron temperature on dielectric function and localization of laser beams in underdense collisional plasmas are investigated. Simulation results show that the electron temperature has a strong effect on t...Effects of electron temperature on dielectric function and localization of laser beams in underdense collisional plasmas are investigated. Simulation results show that the electron temperature has a strong effect on the dielectric constant and the laser beam localization. It is observed that due to the influence of the electron temperature, the dielectric function presents some interesting and complicated nonlinear variations, and gives rise to the laser beam lo- calization. Moreover, the amplitudes of the beam width and the beam intensity are subjected to continuously oscillatory variation in the region of localization. In addition, the effects of several parameters on the dielectric function and the beam localization are discussed.展开更多
We measured electron temperatures through a hollow cathode-type discharge tube using several different floating probe methods. This method detected a shift in the floating potential when an AC voltage was applied to a...We measured electron temperatures through a hollow cathode-type discharge tube using several different floating probe methods. This method detected a shift in the floating potential when an AC voltage was applied to a probe through an intermediary blocking capacitor. The shift in the floating potential is described as a function of the electron temperature and the applied AC voltage. In this study, the effects of the frequency and waveform on the electron temperatures were systematically investigated. The electron temperature measured when using the floating probe method with applied sinusoidal and triangular voltages was lower than that measured with an applied rectangular voltage.The value in the high frequency range was close to that of the tail electron temperature.展开更多
The reliability of diagnostic systems in tokamak plasma is of great significance for physics researches or fusion reactor.When some diagnostics fail to detect information about the plasma status,such as electron tempe...The reliability of diagnostic systems in tokamak plasma is of great significance for physics researches or fusion reactor.When some diagnostics fail to detect information about the plasma status,such as electron temperature,they can also be obtained by another method:fitted by other diagnostic signals through machine learning.The paper herein is based on a machine learning method to predict electron temperature,in case the diagnostic systems fail to detect plasma temperature.The fully-connected neural network,utilizing back propagation with two hidden layers,is utilized to estimate plasma electron temperature approximately on the J-TEXT.The input parameters consist of soft x-ray emission intensity,electron density,plasma current,loop voltage,and toroidal magnetic field,while the targets are signals of electron temperature from electron cyclotron emission and x-ray imaging crystal spectrometer.Therefore,the temperature profile is reconstructed by other diagnostic signals,and the average errors are within 5%.In addition,generalized regression neural network can also achieve this function to estimate the temperature profile with similar accuracy.Predicting electron temperature by neural network reveals that machine learning can be used as backup means for plasma information so as to enhance the reliability of diagnostics.展开更多
In order to estimate the electron temperature soft x-ray imaging diagnostics using a double filter technique has been developed in the HT-7 tokamak. The chosen thicknesses of the Be foil are 12.5 μm and 70 μm, respe...In order to estimate the electron temperature soft x-ray imaging diagnostics using a double filter technique has been developed in the HT-7 tokamak. The chosen thicknesses of the Be foil are 12.5 μm and 70 μm, respectively. In this article both the main design of the diagnostic configuration and the method to estimate the electron temperature are presented. The results agree with those estimated from the soft x-ray pulse height analyzer （PHA）. The main causes of systematic error have also been investigated.展开更多
This study presents a novel floating probe method to measure electron temperatures using a hollow cathode-type discharge tube. The proposed method detects a shift in the floating potential when an AC voltage is applie...This study presents a novel floating probe method to measure electron temperatures using a hollow cathode-type discharge tube. The proposed method detects a shift in the floating potential when an AC voltage is applied to a probe through an intermediary blocking capacitor. The shift in the floating potential is described as a function of the electron temperature and the applied AC voltage. The floating probe method is simpler than the Langmuir probe method because it does not require the measurement of volt-ampere characteristics. As the input AC voltage increases, the electron temperature converges. The electron temperature measured using the floating probe method with an applied sinusoidal voltage shows a value close to the first （tail） electron temperature in the range of the floating potential.展开更多
Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited...Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited so that it is not conducive to revealing the deep physical mechanism.In this work,Bayesian probability inference with machine learning methods have been applied to the electron cyclotron emission and Thomson scattering diagnostic systems on HL-2A/2M,and the effects of integrated data analysis(IDA)on the electron temperature of HL-2A with Bayesian probability inference are demonstrated.A program is developed to infer the whole electron temperature profile with a confidence interval,and the program can be applied in online analysis.The IDA results show that the full profile of the electron temperature can be obtained and the diagnostic information is more comprehensive and abundant with IDA.The inference models for electron temperature analysis are established and the developed programs will serve as an experimental data analysis tool for HL-2A/2M in the near future.展开更多
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDA25051000,XDA25010100,XDA25010300,XDA25030100,and XDA25030200)。
文摘Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research.Experiments involving laser-irradiated copper(Cu)foil were performed at the Shenguang-II facility.A highly oriented pyrolytic graphite crystal spectrometer measured the time-integrated spectral distribution of Cu under varying laser intensities.Using the two-dimensional radiation-hydrodynamics code FLASH and the spectral analysis code FLYCHK,we simulated the temporal evolution of plasma density and temperature distributions,as well as the emission intensities of spectral lines at different temperatures and densities.The simulation results revealed that the two-electron satellite lines(J)and the resonance line(W)emissions of Cu originate predominantly from the radiation region near the critical density surface,with a density range from approximately 0.5 nc to 1.0 nc,and radiate primarily during the laser irradiation period.By analyzing the J/W intensity ratio of the measured spectral lines,we estimated the electron temperatures near the critical-density surface under different laser intensities.
文摘This article provides a short review on the importance of the detailed analysis of a Langmuir probe I-V trace in a multi-Maxwellian plasma,and discuss proper procedures analyzing Langmuir probe I-V traces in bi-Maxwellian and triple-Maxwellian Electron Energy Distribution Function(EEDF)plasmas.Discus⁃sion and demonstration of procedures include the treatment of the ion saturation current,electron saturation cur⁃rent,space-charge effects on the I-V trace,and most importantly how to properly isolate and fit for each electron group present in an I-V trace reflecting a mult-Maxwellian EEDF,as well as how having a multi-Maxwellian EEDF affects the procedures of treating the ion and electron saturation currents.Shortcomings of common improp⁃er procedures are discussed and demonstrated with simulated I-V traces to show how these procedures gives false measurements.
基金supported by the National Magnetic Confinement Fusion Science Program of China (Nos.2022YFE03100004,2017YFE0301700,2017YFE0301701 and 2022YFE03060003)National Natural Science Foundation of China (Nos.12375226,12175227,11875255 and 11975231)+2 种基金the China Postdoctoral Science Foundation (No.2022M723066)the Fundamental Research Funds for the Central Universitiesthe Collaborative Innovation Program of Hefei Science Center,CAS (No.2022HSCCIP022)。
文摘A 100-channel double-foil soft X-ray array imaging(DSXAI)diagnostic system has been developed for the HL-2A tokamak to obtain tomographic bremsstrahlung emissivity and electron temperature(T_(e)).This system employs a double-foil technique to determine T_(e) by comparing the soft X-ray(SXR)emissivities from the same plasma location through two beryllium(Be)foils of differing thickness.The DSXAI system comprises five photocameras mounted at two different poloidal cross-sections,separated toroidally by 15°,allowing for three distinct poloidal viewing angles.Each photocamera features 20 channels,offering a temporal resolution of approximately 4μs and a spatial resolution of about 8 cm,with no channel overlap.Each photocamera contains two identical optical systems,each defined by an aperture slit and a photodiode array.The double-foil configuration is realized by placing these two optical systems,each with a different Be foil,in close proximity.Initial experimental results demonstrate that the DSXAI diagnostic system performs well,successfully reconstructing 2-dimensional(2D)tomographic SXR emissivity and T_(e) on the HL-2A tokamak.This study provides valuable insights for the future implementation of similar diagnostic systems on fusion reactors like ITER.
文摘In this article, four kinds of optical emission spectroscopic methods of determining electron temperature are used to investigate the relationship between electron temperature and pressure in the cylindrical plasmas of dc glow discharges at low pressures in laboratory by measuring the relative intensities of ArI lines at various pressures. These methods are developed respectively on the basis of the Fermi-Dirac model, corona model, and two kinds of electron collision cross section models according to the kinetic analysis. Their theoretical bases and the conditions to which they are applicable are reviewed, and their calculation results and fitting errors are compared with each other. The investigation has indicated that the electron temperatures obtained by the four methods become consistent with each other when the pressure increases in the low pressure argon plasmas.
基金supported by the National Magnetic Confinement Fusion Science Foundation of China(Nos.2015GB102000 and 2014GB103000)
文摘Stationary long pulse plasma of high electron temperature was produced on EAST for the first time through an integrated control of plasma shape, divertor heat flux, particle exhaust, wall conditioning, impurity management, and the coupling of multiple heating and current drive power. A discharge with a lower single null divertor configuration was maintained for 103 s at a plasma current of 0.4 MA, q95 ≈7.0, a peak electron temperature of 〉4.5 keV, and a central density ne（0）-2.5×10^19 m^-3. The plasma current was nearly non-inductive （Vloop 〈0.05 V, poloidal beta - 0.9） driven by a combination of 0.6 MW lower hybrid wave at 2.45 GHz, 1.4 MW lower hybrid wave at 4.6 GHz, 0.5 MW electron cyclotron heating at 140 GHz, and 0.4 MW modulated neutral deuterium beam injected at 60 kV. This progress demonstrated strong synergy of electron cyclotron and lower hybrid electron heating, current drive, and energy confinement of stationary plasma on EAST. It further introduced an example of integrated ＂hybrid＂ operating scenario of interest to ITER and CFETR.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2013GB109005)the Fundamental Research Funds for the Central Universities(Nos.DUT15RC(3)072,DUT15TD44,DUT16TD13)
文摘As advanced linear plasma sources, cascaded arc plasma devices have been used to generate steady plasma with high electron density, high particle flux and low electron temperature. To measure electron density and electron temperature of the plasma device accurately, a laser Thomson scattering（LTS） system, which is generally recognized as the most precise plasma diagnostic method, has been established in our lab in Dalian University of Technology. The electron density has been measured successfully in the region of 4.5？×10^19m^-3 to7.1？×10^20m^-3 and electron temperature in the region of 0.18 eV to 0.58 eV. For comparison,an optical emission spectroscopy（OES） system was established as well. The results showed that the electron excitation temperature（configuration temperature） measured by OES is significantly higher than the electron temperature（kinetic electron temperature） measured by LTS by up to 40% in the given discharge conditions. The results indicate that the cascaded arc plasma is recombining plasma and it is not in local thermodynamic equilibrium（LTE）. This leads to significant error using OES when characterizing the electron temperature in a non-LTE plasma.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.10905047)
文摘Two curved crystal spectrometers are set up on the ＂QiangGuang-1＂ generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several ＂bright spots＂ indicate electron temperatures between （450 eV- 520 eV） ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV±30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a - 1 MA facility.
文摘The electronic excitation temperature of a surface dielectric barrier discharge （DBD） at atmospheric pressure has been experimentally investigated by optical emission spectroscopic measurements combined with numerical simulation. Experiments have been carried out to deter- mine the spatial distribution of electric field by using FEM software and the electronic excitation temperature in discharge by calculating ratio of two relative intensities of atomic spectral lines. In this work, we choose seven Ar atomic emission lines at 415.86 nm [（3s^23p^5）5p →（3s^23p^5）4s] and 706.7 nm, 714.7 nm, 738.4 nm, 751.5 nm, 794.8 nm and 800.6 nm [（3s^23p^5）4p → （3s^23p^5）4s] to estimate the excitation temperature under a Boltzmann approximation. The average electron energy is evaluated in each discharge by using line ratio of 337.1 nm （N2（C^3Пu →B3Пg）） to 391.4 nm （N2^＋（B2 ∑u^＋→ ∑g^＋））. Furthermore, variations of the electronic excitation tempera- ture are presented versus dielectric thickness and dielectric materials. The discharge is stable and uniform along the axial direction, and the electronic excitation temperature at the edge of the copper electrode is the largest. The corresponding average electron energy is in the range of 1.6- 5.1 eV and the electric field is in 1.7-3.2 MV/m, when the distance from copper electrode varies from 0 cm to 6 cm. Moreover, the electronic excitation temperature with a higher permittivity leads to a higher dissipated electrical power.
基金supported by the National Natural Science Foundation of China (Grant nos. 40831062,41004065)National Supportive Project of Science and Technology of China (Grant no.2006BAB18B06)the State Key Laboratory of Space Weather (Grant no.08262DAA4S) and National Key Laboratory of Electromagnetic Environment
文摘Observation data recorded by the European Incoherent Scatter Scientific Association in TromsФ, Norway in August 2009 were analyzed to determine the heating effects in polar summer ionospheric modification experiments. There are two types of increases in electron temperature： large relative increases in a narrow range near 150 km and greater absolute increases in a wider range at 150-400 km. The percentage increase in temperature linearly increases with heating power, but the rate of increase decreases with increasing pump frequency. A clear two-dimensional distribution was found for the measurement made on August 15, and the beating effects are greater closer to the direction of the geomagnetic field. The heating effects obviously depend on the angle between the heating beam and geomagnetic field; as the angle increases, the heating effect decreases.
基金supported by National Natural Science Foundation of China(Grant No.11647150)Young Talents Program of Gansu Province of China(2016)Scientific Research Program of the Higher Education Institutions of Gansu Province of China(Grant No.2016A-068)
文摘Based on the theory of plasma continuous radiation, the relationship between the emission intensity of bremsstrahlung and recombination radiation and the plasma electron temperature is obtained. During the development process of a return stroke of ground flash, the intensity of continuous radiation spectrum is separated on the basis of the spectrums with obviously different luminous intensity at two moments. The electron temperature of the lightning discharge channel is obtained through the curve fitting of the continuous spectrum intensity. It is found that electron temperature increases with the increase of wavelength and begins to reduce after the peak. The peak temperature of the two spectra is close to 25 000 K. To be compared with the result of discrete spectrum, the electron temperature is fitted by the O I line and N II line of the spectrum respectively. The comparison shows that the high temperature value is in good agreement with the temperature of the lightning core current channel obtained from the ion line information, and the low temperature at the high band closes to the calculation result of the atomic line, at a low band is lower than the calculation of the atomic line, which reflects the temperature of the luminous channel of the outer corona.
基金supported by National Magnetic Confinement Fusion Science Program of China under Contracts Nos.2015GB101000,2013GB106000,and 2013GB107000National Natural Science Foundation of China under Contracts Nos.11575235,11422546 and 11505222Youth Foundation of ASIPP under Grant No.Y45ETY2306
文摘A new edge tangential multi-energy soft x-ray（ME-SXR） diagnostic with high temporal（≤ 0.1 ms） and spatial（~1 cm） resolution has been developed for a variety of physics topics studies in the EAST tokamak plasma. The fast edge electron temperature profile（approximately from r a~ 0.6 to the scrape-off layer） is investigated using ME-SXR diagnostic system. The data process was performed by the ideal ‘multi-foil＇ technique, with no priori assumptions of plasma profiles. Reconstructed ME-SXR emissivity profiles for a variety of EAST experimental scenarios are presented here for the first time. The applications of the ME-SXR for study of the effects of resonant magnetic perturbation on edge localized modes and the first time neon radiating divertor experiment in EAST are also presented in this work. It has been found that neon impurity can suppress the 2/1 tearing mode and trigger a 3/1 MHD mode.
基金supported by the National Natural Science Foundation of China(No.11604003)Anhui Province Key Laboratory of Optoelectronic Materials Science and Technology(OMST201703)the Natural Science Foundations of Bengbu College(No.2017ZR11zd)
文摘An Nd:YAG single pulse nanosecond laser of 532 nm wavelength with an 8 ns pulse width was projected on the soil samples collected from the campus of Bengbu College under 1 standard atmospheric pressure. Laser-induced breakdown spectroscopy at different sample temperatures was achieved. The intensity and signal-to-noise ratio (SNR) changes of different characteristic spectral lines could be analyzed when the sample temperature changes.The evolution of plasma electron temperature and electron density with the sample temperature was analyzed through Boltzmann oblique line method and Stark broadening method.The cause of the radiation enhancement of laser-induced metal plasma was discussed. Experimental results demonstrated that the spectral intensity, SNR, the electron temperature and electron density of plasma are positively related to the sample temperature, and reach saturation at 100℃.
基金supported by the National Magnetic Confinement Fusion Science Program of China(Nos.2013GB109005,2009GB106004)National Natural Science Foundation of China(Nos.11175035,10875023)the Fundamental Research Funds for the Central Universities of China(DUT 12ZD(G)01,DUT 11ZD(G)06)
文摘In this paper, a low pressure Ar/N2 shock plasma jet with clearly multicycle al- ternating zones produced by a DC cascade arc discharge has been investigated by an emission spectral method combined with Abel inversion analysis. Plasma emission intensity, electron, vi- brational and rotational temperatures of the shock plasma have been measured in the expansion and compression zones. The results indicate that the ranges of the measured electron temperature, vibrational temperature and rotational temperature are 1.1 eV to 1.6 eV, 0.2 eV to 0.7 eV and 0.19 eV to 0.22 eV, respectively, and it is found for the first time that the vibrational and rota- tional temperatures increase while the electron temperature decreases in the compression zones. The electron temperature departs from the vibrational and the rotational temperatures due to non-equilibrium plasma effects. Electrons and heavy particles could not completely exchange energy via collisions in the shock plasma jet under the low pressure of 620 Pa or so.
基金supported by the National Natural Science Foundation of China(Grant Nos.10975026,11275034,and 11175052)the Key Project of Science andTechnology of Liaoning Province,China(Grant No.2011224007)the Fundamental Research Funds for the Central Universities of Ministry of Educationof China(Grant No.3132014328)
文摘In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the secondary electron emission in the Hall thruster, by the particle-in-cell （PIC） method. The numerical results show that when the electron temperature is relatively low, the change of sheath potential drop is relatively large, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is relatively high, the surface potential maintains a persistent oscillation, and the stability of the sheath reduces. As the electron temperature increases, the secondary electron emission coefficient on the wall increases. For three kinds of propellants （At, Kr, and Xe）, as the ion mass increases the sheath potentials and the secondary electron emission coefficients reduce in sequence.
基金Project supported by the Autonomous Innovation Fund,China (Grant Nos.0109012922 and 0109012926)the Youth Foundation of Department of Education of Hubei Province,China (Grant No.Q20101602)
文摘Effects of electron temperature on dielectric function and localization of laser beams in underdense collisional plasmas are investigated. Simulation results show that the electron temperature has a strong effect on the dielectric constant and the laser beam localization. It is observed that due to the influence of the electron temperature, the dielectric function presents some interesting and complicated nonlinear variations, and gives rise to the laser beam lo- calization. Moreover, the amplitudes of the beam width and the beam intensity are subjected to continuously oscillatory variation in the region of localization. In addition, the effects of several parameters on the dielectric function and the beam localization are discussed.
文摘We measured electron temperatures through a hollow cathode-type discharge tube using several different floating probe methods. This method detected a shift in the floating potential when an AC voltage was applied to a probe through an intermediary blocking capacitor. The shift in the floating potential is described as a function of the electron temperature and the applied AC voltage. In this study, the effects of the frequency and waveform on the electron temperatures were systematically investigated. The electron temperature measured when using the floating probe method with applied sinusoidal and triangular voltages was lower than that measured with an applied rectangular voltage.The value in the high frequency range was close to that of the tail electron temperature.
基金supported by the National Magnetic Confinement Fusion Science Program(Nos.2018YFE0301104,2018YFE0301100)State Key Laboratory of Advanced Electromagnetic Engineering and Technology(No.AEET2020KF001)National Natural Science Foundation of China(Nos.12075096,51821005)。
文摘The reliability of diagnostic systems in tokamak plasma is of great significance for physics researches or fusion reactor.When some diagnostics fail to detect information about the plasma status,such as electron temperature,they can also be obtained by another method:fitted by other diagnostic signals through machine learning.The paper herein is based on a machine learning method to predict electron temperature,in case the diagnostic systems fail to detect plasma temperature.The fully-connected neural network,utilizing back propagation with two hidden layers,is utilized to estimate plasma electron temperature approximately on the J-TEXT.The input parameters consist of soft x-ray emission intensity,electron density,plasma current,loop voltage,and toroidal magnetic field,while the targets are signals of electron temperature from electron cyclotron emission and x-ray imaging crystal spectrometer.Therefore,the temperature profile is reconstructed by other diagnostic signals,and the average errors are within 5%.In addition,generalized regression neural network can also achieve this function to estimate the temperature profile with similar accuracy.Predicting electron temperature by neural network reveals that machine learning can be used as backup means for plasma information so as to enhance the reliability of diagnostics.
基金supported by National Natural Science Foundation of China (Nos. 10375070, 10305012)
文摘In order to estimate the electron temperature soft x-ray imaging diagnostics using a double filter technique has been developed in the HT-7 tokamak. The chosen thicknesses of the Be foil are 12.5 μm and 70 μm, respectively. In this article both the main design of the diagnostic configuration and the method to estimate the electron temperature are presented. The results agree with those estimated from the soft x-ray pulse height analyzer （PHA）. The main causes of systematic error have also been investigated.
文摘This study presents a novel floating probe method to measure electron temperatures using a hollow cathode-type discharge tube. The proposed method detects a shift in the floating potential when an AC voltage is applied to a probe through an intermediary blocking capacitor. The shift in the floating potential is described as a function of the electron temperature and the applied AC voltage. The floating probe method is simpler than the Langmuir probe method because it does not require the measurement of volt-ampere characteristics. As the input AC voltage increases, the electron temperature converges. The electron temperature measured using the floating probe method with an applied sinusoidal voltage shows a value close to the first （tail） electron temperature in the range of the floating potential.
基金supported by the National Magnetic Confinement Fusion Energy Research and Development Program of China(Nos.2019YFE03090100,2019YFE03040004)the National Science Foundation for Young Scientists of China(No.12005052)。
文摘Data analysis on tokamak plasmas is mainly based on various diagnostic systems,which are usually modularized and independent of each other.This leads to a large amount of data not being fully and effectively exploited so that it is not conducive to revealing the deep physical mechanism.In this work,Bayesian probability inference with machine learning methods have been applied to the electron cyclotron emission and Thomson scattering diagnostic systems on HL-2A/2M,and the effects of integrated data analysis(IDA)on the electron temperature of HL-2A with Bayesian probability inference are demonstrated.A program is developed to infer the whole electron temperature profile with a confidence interval,and the program can be applied in online analysis.The IDA results show that the full profile of the electron temperature can be obtained and the diagnostic information is more comprehensive and abundant with IDA.The inference models for electron temperature analysis are established and the developed programs will serve as an experimental data analysis tool for HL-2A/2M in the near future.
