Electron temperature and electron number density are important parameters in the characterization of plasma. In this paper the electron temperature and electron number density of soil plasma generated by laser ablatio...Electron temperature and electron number density are important parameters in the characterization of plasma. In this paper the electron temperature and electron number density of soil plasma generated by laser ablation combined with nanosecond discharge spark at different discharge voltages have been studied. Saha-Boltzmann plot and Stark broadening are used to determine the temper- ature and electron number density. It is proved that local thermal equilibrium is fulfilled in the nanosecond spark enhanced plasma. The enhanced optical emission, signal to noise ratio and the stability in term of the relative standard deviation of signal intensity at different spark voltages were investigated in detail. A relative stable discharge process was observed with use of a 10 kV discharge voltage under the carried experimental configuration.展开更多
Single-pulse and double-pulse optical emission spectroscopy （OES） analyses were carried out in air by using ultrashort laser pulses at atmospheric pressure. The aim of this work is to use spectroscopic methods to an...Single-pulse and double-pulse optical emission spectroscopy （OES） analyses were carried out in air by using ultrashort laser pulses at atmospheric pressure. The aim of this work is to use spectroscopic methods to analyze the early phase of laser-induced plasma after the femtosecond laser pulse. The temporal behavior of emission spectra of air plasma has been characterized. In comparison with the single-pulse scheme, the plasma emission obtained in the double-pulse scheme presents a more intense continuum along with several additional ionic lines. As only one line is available in the single-pulse scheme, the plasma temperature measurements were performed using only the relative line-to-continuum intensity ratio method, whereas the relative line-to-line intensity ratio method and the relative line-to-continuum intensity ratio method were used simultaneously to estimate the electron temperature in the double-pulse scheme. The results reveal that the temperature values obtained by the two methods in the double-pulse scheme agree. Moreover, this shows that the relative line-to-continuum intensity ratio method is suitable for early phase of laser-induced plasma diagnostics. The electron number density was estimated using the Stark broadening method. In the early phase of laser-induced plasma, the temporal evolution of the electron number density exhibits a power law decrease with delay time.展开更多
Laser-induced steel plasma is generated by focusing a Q-switched Nd：YAG visible laser（532 nm wavelength） with an irradiance of 1 x 109 W/cm2 on a steel sample in air at atmospheric pressure.An Echelle spectrograph ...Laser-induced steel plasma is generated by focusing a Q-switched Nd：YAG visible laser（532 nm wavelength） with an irradiance of 1 x 109 W/cm2 on a steel sample in air at atmospheric pressure.An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions.Using time-resolved spectroscopic measurements of the plasma emissions,the temperature and electron number density of the steel plasma are determined for many times of the detector delay.The validity of the assumption by the spectroscopic methods that the laser-induced plasma（LIP） is optically thin and is also in local thermodynamic equilibrium（LTE） has been evaluated for many delay times.From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value,the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns,900 ns and 1000 ns.展开更多
A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP)discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmiss...A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP)discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation.Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium,and that the electron number density increases with the augment of pressure,radio frequency(RF)power,and RF frequency.However,the electron number density first increases and then decreases as the discharge gap increases.The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-dB higher than that of helium.At the same time,the transmission attenuation increases with the augment of the RF power and RF frequency,but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap.The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band.It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.展开更多
We studied the spatial evolution of the Fe-Ni plasma generated by the fundamental （1064 nm） and second （532 nm） harmonics of a Q-switched Nd： YAG laser. The experimentally observed line profiles of the neutral ir...We studied the spatial evolution of the Fe-Ni plasma generated by the fundamental （1064 nm） and second （532 nm） harmonics of a Q-switched Nd： YAG laser. The experimentally observed line profiles of the neutral iron （Fe I） have been used to extract the plasma temperature （T e ） using the Boltzmann plot method, whereas the electron number density （N e ） has been deter- mined from the Stark broadening. In addition, we studied the spatial behavior of T e and N e with the variation of laser energy for iron plasma by placing the target material （iron-nickel alloy） in air at atmospheric pressure for both modes of the Nd： YAG laser.展开更多
The development of space science has generated important computer codes for the simulation of the interaction between complex space structures(artificial satellites,solar panels,etc.)and the surrounding plasma.The bas...The development of space science has generated important computer codes for the simulation of the interaction between complex space structures(artificial satellites,solar panels,etc.)and the surrounding plasma.The basic equation to be solved is the Poisson equation for the electric potential around a structure.Here,we try to study analytically the shadowing effect of a spacecraft on an electrode for the electron number density and the electron temperature.We suggest that the electron temperature should be taken as a variable and not as a parameter.However,its computation involves the knowledge of the histogram of the distribution of the frequencies of the electron velocities inside the computational cells.Also,we have illustrated the possibilities of artefacts due to the design and geometry of scientific instruments for the measurement of the electron number density and the electron temperature in the ionosphere.We suggest an optimal design for an electrode and its guard ring.展开更多
Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,...Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,half and tenth value layers,mean free path,effective atomic and electronic cross sections,effective atomic number,and effective electron density of fifteen essential amino acids have been determined for 133Ba,137Cs,and 60Co gamma-ray sources.The MCNP-4C code and the XCOM program have been used to calculate these parameters.The results have been compared to the available experimental and theoretical data.The theoretical results agreed with the experimental data,with RD values of ≤±7%.In the energy region of 81-1332.5 keV,it was found that the μm,σa,and revalues of the amino acids decreased as the photon energy increased,and the increasing density of amino acids had no steady effect on these quantities.Additionally,results demonstrated that the HVL,TVL,and MFP values increased with the increase in photon energy.The μm,σa,and Zeff values of aspartic acid were the highest among those of all amino acids,and they were the lowest for isoleucine.The Zeff value of each sample containing H,C,N,and O atoms was nearly constant in the studied energy region.The Neffvalues of the studied amino acids varied in the range of 3.14×10^23-3.44×10^23 electron/g.Furthermore,the Neffvalues were approximately independent of the amino acid type in this energy region.展开更多
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant No. 61178034）, Zhejiang Provincial Natural Science Foundation of China （Grant No. Y1100268）, and partially supported by Key Research Project of University of Zhejiang Province, China （Grant No. ZD2009006）, and the Program for Innovative Research Team, Zhejiang Normal University, Jinhua, Zhejiang Province, China.
文摘Electron temperature and electron number density are important parameters in the characterization of plasma. In this paper the electron temperature and electron number density of soil plasma generated by laser ablation combined with nanosecond discharge spark at different discharge voltages have been studied. Saha-Boltzmann plot and Stark broadening are used to determine the temper- ature and electron number density. It is proved that local thermal equilibrium is fulfilled in the nanosecond spark enhanced plasma. The enhanced optical emission, signal to noise ratio and the stability in term of the relative standard deviation of signal intensity at different spark voltages were investigated in detail. A relative stable discharge process was observed with use of a 10 kV discharge voltage under the carried experimental configuration.
基金supported by National Natural Science Foundation of China(Nos.11135002,11075069,91026021 and 11075068)the Scholarship Award for Excellent Doctoral Student Granted by the Ministry of Education of China
文摘Single-pulse and double-pulse optical emission spectroscopy （OES） analyses were carried out in air by using ultrashort laser pulses at atmospheric pressure. The aim of this work is to use spectroscopic methods to analyze the early phase of laser-induced plasma after the femtosecond laser pulse. The temporal behavior of emission spectra of air plasma has been characterized. In comparison with the single-pulse scheme, the plasma emission obtained in the double-pulse scheme presents a more intense continuum along with several additional ionic lines. As only one line is available in the single-pulse scheme, the plasma temperature measurements were performed using only the relative line-to-continuum intensity ratio method, whereas the relative line-to-line intensity ratio method and the relative line-to-continuum intensity ratio method were used simultaneously to estimate the electron temperature in the double-pulse scheme. The results reveal that the temperature values obtained by the two methods in the double-pulse scheme agree. Moreover, this shows that the relative line-to-continuum intensity ratio method is suitable for early phase of laser-induced plasma diagnostics. The electron number density was estimated using the Stark broadening method. In the early phase of laser-induced plasma, the temporal evolution of the electron number density exhibits a power law decrease with delay time.
文摘Laser-induced steel plasma is generated by focusing a Q-switched Nd：YAG visible laser（532 nm wavelength） with an irradiance of 1 x 109 W/cm2 on a steel sample in air at atmospheric pressure.An Echelle spectrograph coupled with a gateable intensified charge-coupled detector is used to record the plasma emissions.Using time-resolved spectroscopic measurements of the plasma emissions,the temperature and electron number density of the steel plasma are determined for many times of the detector delay.The validity of the assumption by the spectroscopic methods that the laser-induced plasma（LIP） is optically thin and is also in local thermodynamic equilibrium（LTE） has been evaluated for many delay times.From the temporal evolution of the intensity ratio of two Fe I lines and matching it with its theoretical value,the delay times where the plasma is optically thin and is also in LTE are found to be 800 ns,900 ns and 1000 ns.
基金Project supported by the Key Research and Development Plan of Anhui Province,China(Grant No.201904a07020013).
文摘A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP)discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation.Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium,and that the electron number density increases with the augment of pressure,radio frequency(RF)power,and RF frequency.However,the electron number density first increases and then decreases as the discharge gap increases.The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-dB higher than that of helium.At the same time,the transmission attenuation increases with the augment of the RF power and RF frequency,but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap.The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band.It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.
文摘We studied the spatial evolution of the Fe-Ni plasma generated by the fundamental （1064 nm） and second （532 nm） harmonics of a Q-switched Nd： YAG laser. The experimentally observed line profiles of the neutral iron （Fe I） have been used to extract the plasma temperature （T e ） using the Boltzmann plot method, whereas the electron number density （N e ） has been deter- mined from the Stark broadening. In addition, we studied the spatial behavior of T e and N e with the variation of laser energy for iron plasma by placing the target material （iron-nickel alloy） in air at atmospheric pressure for both modes of the Nd： YAG laser.
文摘The development of space science has generated important computer codes for the simulation of the interaction between complex space structures(artificial satellites,solar panels,etc.)and the surrounding plasma.The basic equation to be solved is the Poisson equation for the electric potential around a structure.Here,we try to study analytically the shadowing effect of a spacecraft on an electrode for the electron number density and the electron temperature.We suggest that the electron temperature should be taken as a variable and not as a parameter.However,its computation involves the knowledge of the histogram of the distribution of the frequencies of the electron velocities inside the computational cells.Also,we have illustrated the possibilities of artefacts due to the design and geometry of scientific instruments for the measurement of the electron number density and the electron temperature in the ionosphere.We suggest an optimal design for an electrode and its guard ring.
文摘Amino acids are the building blocks of proteins,which are the most abundant macromolecules in living cells.From the standpoint of the photon interaction cross sections of amino acids,the mass attenuation coefficients,half and tenth value layers,mean free path,effective atomic and electronic cross sections,effective atomic number,and effective electron density of fifteen essential amino acids have been determined for 133Ba,137Cs,and 60Co gamma-ray sources.The MCNP-4C code and the XCOM program have been used to calculate these parameters.The results have been compared to the available experimental and theoretical data.The theoretical results agreed with the experimental data,with RD values of ≤±7%.In the energy region of 81-1332.5 keV,it was found that the μm,σa,and revalues of the amino acids decreased as the photon energy increased,and the increasing density of amino acids had no steady effect on these quantities.Additionally,results demonstrated that the HVL,TVL,and MFP values increased with the increase in photon energy.The μm,σa,and Zeff values of aspartic acid were the highest among those of all amino acids,and they were the lowest for isoleucine.The Zeff value of each sample containing H,C,N,and O atoms was nearly constant in the studied energy region.The Neffvalues of the studied amino acids varied in the range of 3.14×10^23-3.44×10^23 electron/g.Furthermore,the Neffvalues were approximately independent of the amino acid type in this energy region.
