Nonlinear screening of a test charge in plasma by electrons trapped or untrapped is studied. The obtained results are in rigorous estimations mathematically in comparison with the corresponding Debye screening forms.M...Nonlinear screening of a test charge in plasma by electrons trapped or untrapped is studied. The obtained results are in rigorous estimations mathematically in comparison with the corresponding Debye screening forms.Meanwhile their validity is physically discussed and some confusions in literature are clarified.展开更多
Plasma shielding is a critical limiting factor in enhancing the quality and efficiency of femtosecond laser processing.This study investigates the temporal evolution of femtosecond-laser-induced plasma in water,unveil...Plasma shielding is a critical limiting factor in enhancing the quality and efficiency of femtosecond laser processing.This study investigates the temporal evolution of femtosecond-laser-induced plasma in water,unveiling a transient recovery window occurring between plasma recombination completion and shockwave generation.During this window,the plasma density returns to baseline levels and exerts a negligible influence on probe light transmission.Furthermore,the plasma recombination time exhibits a strong dependence on the pump pulse energy.The pump pulse energy densities of 2.15,2.77,and 3.72 J/cm^(2) correspond to plasma recombination time of 231.0,125.4,and 112.2 ps,respectively.This advancement could potentially offer a valuable reference for optimizing pulse sequences in high-repetition-rate processing.展开更多
Lens-to-sample distances, delay time, atmospheric condition, laser pulse energy, etc. had obvious effects on the analytical performance of laser-induced breakdown spectroscopy. In this paper, these parameters are inve...Lens-to-sample distances, delay time, atmospheric condition, laser pulse energy, etc. had obvious effects on the analytical performance of laser-induced breakdown spectroscopy. In this paper, these parameters are investigated in greater detail and we will explain how they have influences on the analytical performance. The results show that the focal plane under the sample surface can improve precision and detection limit, and the delay time should be decided according to sensitivity and accuracy. Spectral line intensity is stronger in argon than helium, nitrogen and air gas environment. Pulse energy should exceed energy threshold （about 50 m J） which can generate plasma, and the energy should not exceed about 300 mJ to avoid plasma shielding. Under optimum parameters, concentration relative standard deviation of C, Si, Mn, P, S, Ni, and Cr for low-alloyed steel （sample number 11278） which were measured 11 times is 2.37%, 2.18%, 2.23%, 7.8%, 9.34%, 1.92%, and 2.13%, respectively. And the detection limit of C, Si, Mn, P, S, Ni, and Cr for pure steel is 0.0045%, 0.0072%, 0.0069%, 0.0027%, 0.0024%, 0.0047%, and 0.0024%, respectively.展开更多
文摘Nonlinear screening of a test charge in plasma by electrons trapped or untrapped is studied. The obtained results are in rigorous estimations mathematically in comparison with the corresponding Debye screening forms.Meanwhile their validity is physically discussed and some confusions in literature are clarified.
基金supported by the National Natural Science Foundation of China(No.82227805)the Hubei Province Science and Technology Plan Project(No.2022BCA049)+1 种基金the Advanced Biomedical Imaging Facility(No.2105-420118-8901-121873)the Bioimaging Core Facility of WNLO。
文摘Plasma shielding is a critical limiting factor in enhancing the quality and efficiency of femtosecond laser processing.This study investigates the temporal evolution of femtosecond-laser-induced plasma in water,unveiling a transient recovery window occurring between plasma recombination completion and shockwave generation.During this window,the plasma density returns to baseline levels and exerts a negligible influence on probe light transmission.Furthermore,the plasma recombination time exhibits a strong dependence on the pump pulse energy.The pump pulse energy densities of 2.15,2.77,and 3.72 J/cm^(2) correspond to plasma recombination time of 231.0,125.4,and 112.2 ps,respectively.This advancement could potentially offer a valuable reference for optimizing pulse sequences in high-repetition-rate processing.
文摘Lens-to-sample distances, delay time, atmospheric condition, laser pulse energy, etc. had obvious effects on the analytical performance of laser-induced breakdown spectroscopy. In this paper, these parameters are investigated in greater detail and we will explain how they have influences on the analytical performance. The results show that the focal plane under the sample surface can improve precision and detection limit, and the delay time should be decided according to sensitivity and accuracy. Spectral line intensity is stronger in argon than helium, nitrogen and air gas environment. Pulse energy should exceed energy threshold （about 50 m J） which can generate plasma, and the energy should not exceed about 300 mJ to avoid plasma shielding. Under optimum parameters, concentration relative standard deviation of C, Si, Mn, P, S, Ni, and Cr for low-alloyed steel （sample number 11278） which were measured 11 times is 2.37%, 2.18%, 2.23%, 7.8%, 9.34%, 1.92%, and 2.13%, respectively. And the detection limit of C, Si, Mn, P, S, Ni, and Cr for pure steel is 0.0045%, 0.0072%, 0.0069%, 0.0027%, 0.0024%, 0.0047%, and 0.0024%, respectively.
