Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us t...Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of ω1, ω2 and ω3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.展开更多
Based on the results of plasma experiments and research work done by Dawson and Jones, Trubnikov, Endean, and other researchers, three requirements for producing and maintaining plasma ball lightning have been found: ...Based on the results of plasma experiments and research work done by Dawson and Jones, Trubnikov, Endean, and other researchers, three requirements for producing and maintaining plasma ball lightning have been found: 1) rotation of plasma, 2) the density of charged particles nc > 3.15 × 10-10ω2,3) a stable confinement of plasma. In this model, the energy density of ball lightning ranged from 10-2 J / cm3 to 104 J/ cm3, the formation, shape, stability, energy, maintaining processes and other properties of ball lightning were explained reasonably.展开更多
Due to the severe restrictions imposed by legislative frameworks, the removal of polyacrylamide(PAM) rapidly and effectively from produced wastewater in offshore oilfields before discharge is becoming an urgent challe...Due to the severe restrictions imposed by legislative frameworks, the removal of polyacrylamide(PAM) rapidly and effectively from produced wastewater in offshore oilfields before discharge is becoming an urgent challenge. In this study, a novel advanced oxidation process based on plasma operated in the gas–liquid interface was used to rapidly decompose PAM, and multiple methods including viscometry, flow field-flow fractionation multi-angle light scattering, UV–visible spectroscopy, and attenuated total reflectanceFourier transform infrared spectroscopy were used to characterize the changes of PAM.Under a discharge voltage of 25 kV and pH 7.0, the PAM concentration decreased from 100 to 0 mg/L within 20 min and the total organic carbon(TOC) decreased from 49.57 to1.23 mg/L within 240 min, following zero-order reaction kinetics. Even in the presence of background TOC as high as 152.2 mg/L, complete removal of PAM(100 mg/L) was also achieved within 30 min. The biodegradability of PAM improved following plasma treatment for 120 min. Active species(such as O3 and H2O2) were produced in the plasma. Hydroxyl radical was demonstrated to play an important role in the degradation of PAM due to the inhibitory effect observed after the addition of an ·OH scavenger, Na2CO3. Meanwhile, the release of ammonia and nitrate nitrogen confirmed the cleavage of the acylamino group.The results of this study demonstrated that plasma, with its high efficiency and chemicalfree features, is a promising technology for the rapid removal of PAM.展开更多
We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on ...We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on the emission spectra centered around 6.7 nm from thin-film Gd targets were first investigated.It is found that the conversion efficiency of the produced plasma is saturated when the laser intensity goes beyond 2×10^(11)W cm^(-2).We have systematically compared the emission spectra of the laser-produced plasma with the changes in the thicknesses of the thin-film Gd targets.It is proved that a minimum-mass target with a thickness of 400 nm is sufficient to provide the maximum conversion efficiency,which also implies that this thickness is the ablation depth for the targets.These findings should be helpful in the exploration of next-generation EUV sources,as the thin-film Gd targets will reduce the debris during the plasma generation process compared with the bulk targets.展开更多
Extreme ultraviolet lithography(EUVL)has been demonstrated to meet the industrial requirements of new-generation semiconductor fabrication.The development of high-power EUV sources is a long-term critical challenge to...Extreme ultraviolet lithography(EUVL)has been demonstrated to meet the industrial requirements of new-generation semiconductor fabrication.The development of high-power EUV sources is a long-term critical challenge to the implementation of EUVL in high-volume manufacturing(HVM),together with other technologies such as photoresist and mask.Historically,both theoretical studies and experiments have clearly indicated that the CO 2 laser-produced plasma(LPP)system is a promising solution for EUVL source,able to realize high conversion efficiency(CE)and output power.Currently,ASML’s NXE:3400B EUV scanner configuring CO_(2) LPP source sys-tem has been installed and operated at chipmaker customers.Mean-while,other research teams have made different progresses in the development of LPP EUV sources.However,in their technologies,some critical areas need to be further improved to meet the requirements of 5 nm node and below.Critically needed improvements include higher laser power,stable droplet generation system and longer collector life-time.In this paper,we describe the performance characteristics of the laser system,droplet generator and mirror collector for different EUV sources,and also the new development results.展开更多
In this paper we present a high repetition rate experimental platform for examining the spatial structure and evolution of Biermann-generated magnetic fields in laser-produced plasmas.We have extended the work of prio...In this paper we present a high repetition rate experimental platform for examining the spatial structure and evolution of Biermann-generated magnetic fields in laser-produced plasmas.We have extended the work of prior experiments,which spanned over millimeter scales,by spatially measuring magnetic fields in multiple planes on centimeter scales over thousands of laser shots.Measurements with magnetic fiux probes show azimuthally symmetric magnetic fields that range from 60 G at 0.7 cm from the target to 7 G at 4.2 cm from the target.The expansion rate of the magnetic fields and evolution of current density structures are also mapped and examined.Electron temperature and density of the laser-produced plasma are measured with optical Thomson scattering and used to directly calculate a magnetic Reynolds number of 1.4×10^(4),confirming that magnetic advection is dominant at≥1.5 cm from the target surface.The results are compared to FLASH simulations,which show qualitative agreement with the data.展开更多
The effect of an external electric field on laser-generated plasma has been studied.It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external elec...The effect of an external electric field on laser-generated plasma has been studied.It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external electric field.An eight-fold emission intensity enhancement in Cu I spectral lines are measured as compared to the signal intensity in the absence of an external electric field.The plasma parameters remain the same initially,up to a few microseconds after the generation of plasma,and this feature makes it more interesting for the quantitative analysis of any sample using laser induced breakdown spectroscopy(LIBS).In the presence of an external electric field,fluctuations(contraction and expansion)in the laser-generated plasma are observed which increase the plasma decay time and consequently result in enhanced signal intensity.展开更多
Simple arguments are used to construct a model to explain the extreme ultraviolet radiation conversion efficiency(EUV-CE) of a tin-based droplet target laser produced plasmas by calculating the laser absorption effici...Simple arguments are used to construct a model to explain the extreme ultraviolet radiation conversion efficiency(EUV-CE) of a tin-based droplet target laser produced plasmas by calculating the laser absorption efficiency,radiation efficiency,and spectral efficiency.The dependence of drive laser pulse duration and laser intensity on EUV-CE is investigated.The results show that at some appropriate laser intensity,where the sum energy of the thermal conduction,out-off band radiation and plasma plume kinetic losses is at a minimum,the EUV-CE should reach a maximum.The EUV-CE predicted by the present simple model is also compared with the available experimental and simulation data and a fair agreement between them is found.展开更多
The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas we...The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas were measured in the wavelength range of 1.0–8.5 nm under different power densities. The atomic spectral data of the unresolved transition arrays from highly charged Yb ions were calculated based on Cowan's suite of codes, including configuration interaction. The calculated Gaussian envelope of the emission determined by the weighted spontaneous transition rates was compared with the experimental spectra, and a good agreement between them was obtained. The spatial-temporal evolutions of the plasmas under the experimental conditions are simulated based on the collisional-radiative model, enabling the understanding of the mechanism of the plasma conditions for optimal water window waveband emission output.展开更多
A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained a...A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.展开更多
文摘Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of ω1, ω2 and ω3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.
文摘Based on the results of plasma experiments and research work done by Dawson and Jones, Trubnikov, Endean, and other researchers, three requirements for producing and maintaining plasma ball lightning have been found: 1) rotation of plasma, 2) the density of charged particles nc > 3.15 × 10-10ω2,3) a stable confinement of plasma. In this model, the energy density of ball lightning ranged from 10-2 J / cm3 to 104 J/ cm3, the formation, shape, stability, energy, maintaining processes and other properties of ball lightning were explained reasonably.
基金supported by National Natural Scientific Foundation of China(No.2159081)the Ministry of Science and Technology,People’s Republic of China(No.2012AA063401)
文摘Due to the severe restrictions imposed by legislative frameworks, the removal of polyacrylamide(PAM) rapidly and effectively from produced wastewater in offshore oilfields before discharge is becoming an urgent challenge. In this study, a novel advanced oxidation process based on plasma operated in the gas–liquid interface was used to rapidly decompose PAM, and multiple methods including viscometry, flow field-flow fractionation multi-angle light scattering, UV–visible spectroscopy, and attenuated total reflectanceFourier transform infrared spectroscopy were used to characterize the changes of PAM.Under a discharge voltage of 25 kV and pH 7.0, the PAM concentration decreased from 100 to 0 mg/L within 20 min and the total organic carbon(TOC) decreased from 49.57 to1.23 mg/L within 240 min, following zero-order reaction kinetics. Even in the presence of background TOC as high as 152.2 mg/L, complete removal of PAM(100 mg/L) was also achieved within 30 min. The biodegradability of PAM improved following plasma treatment for 120 min. Active species(such as O3 and H2O2) were produced in the plasma. Hydroxyl radical was demonstrated to play an important role in the degradation of PAM due to the inhibitory effect observed after the addition of an ·OH scavenger, Na2CO3. Meanwhile, the release of ammonia and nitrate nitrogen confirmed the cleavage of the acylamino group.The results of this study demonstrated that plasma, with its high efficiency and chemicalfree features, is a promising technology for the rapid removal of PAM.
基金supported by National Natural Science Foundation of China(Nos.61427812,61805118,12104216 and 12241403)the Natural Science Foundation of Jiangsu Province of China(Nos.BK20192006,BK20180056 and BK20200307)。
文摘We have studied laser-produced plasma based on mass-limited thin-film Gd targets for beyond the current extreme ultraviolet(EUV)light source of 13.5 nm wavelength based on tin.The influences of the laser intensity on the emission spectra centered around 6.7 nm from thin-film Gd targets were first investigated.It is found that the conversion efficiency of the produced plasma is saturated when the laser intensity goes beyond 2×10^(11)W cm^(-2).We have systematically compared the emission spectra of the laser-produced plasma with the changes in the thicknesses of the thin-film Gd targets.It is proved that a minimum-mass target with a thickness of 400 nm is sufficient to provide the maximum conversion efficiency,which also implies that this thickness is the ablation depth for the targets.These findings should be helpful in the exploration of next-generation EUV sources,as the thin-film Gd targets will reduce the debris during the plasma generation process compared with the bulk targets.
基金supported by the National Key R&D Program of China(2019YFB1704600).
文摘Extreme ultraviolet lithography(EUVL)has been demonstrated to meet the industrial requirements of new-generation semiconductor fabrication.The development of high-power EUV sources is a long-term critical challenge to the implementation of EUVL in high-volume manufacturing(HVM),together with other technologies such as photoresist and mask.Historically,both theoretical studies and experiments have clearly indicated that the CO 2 laser-produced plasma(LPP)system is a promising solution for EUVL source,able to realize high conversion efficiency(CE)and output power.Currently,ASML’s NXE:3400B EUV scanner configuring CO_(2) LPP source sys-tem has been installed and operated at chipmaker customers.Mean-while,other research teams have made different progresses in the development of LPP EUV sources.However,in their technologies,some critical areas need to be further improved to meet the requirements of 5 nm node and below.Critically needed improvements include higher laser power,stable droplet generation system and longer collector life-time.In this paper,we describe the performance characteristics of the laser system,droplet generator and mirror collector for different EUV sources,and also the new development results.
基金the Department of Energy(DOE)under award number DE-SC0019011the National Nuclear Security Administration(NNSA)Center for Matter under Extreme Conditions under award number DE-NA0003842+1 种基金the National Science Foundation Graduate Fellowship Research Program under award number DGE-1650604support by the U.S.DOE NNSA under Subcontracts 536203 and 630138 with Los Alamos National Laboratory,Subcontract B632670 with LLNL and support from the Cooperative Agreement DE-NA0003856 to the Laboratory for Laser Energetics University of Rochester。
文摘In this paper we present a high repetition rate experimental platform for examining the spatial structure and evolution of Biermann-generated magnetic fields in laser-produced plasmas.We have extended the work of prior experiments,which spanned over millimeter scales,by spatially measuring magnetic fields in multiple planes on centimeter scales over thousands of laser shots.Measurements with magnetic fiux probes show azimuthally symmetric magnetic fields that range from 60 G at 0.7 cm from the target to 7 G at 4.2 cm from the target.The expansion rate of the magnetic fields and evolution of current density structures are also mapped and examined.Electron temperature and density of the laser-produced plasma are measured with optical Thomson scattering and used to directly calculate a magnetic Reynolds number of 1.4×10^(4),confirming that magnetic advection is dominant at≥1.5 cm from the target surface.The results are compared to FLASH simulations,which show qualitative agreement with the data.
文摘The effect of an external electric field on laser-generated plasma has been studied.It is observed that the laser-generated plasma can be used for the ignition of a spark in the presence of a low voltage external electric field.An eight-fold emission intensity enhancement in Cu I spectral lines are measured as compared to the signal intensity in the absence of an external electric field.The plasma parameters remain the same initially,up to a few microseconds after the generation of plasma,and this feature makes it more interesting for the quantitative analysis of any sample using laser induced breakdown spectroscopy(LIBS).In the presence of an external electric field,fluctuations(contraction and expansion)in the laser-generated plasma are observed which increase the plasma decay time and consequently result in enhanced signal intensity.
基金Supported by the National Natural Science Foundation of China under Grant No. 61078024
文摘Simple arguments are used to construct a model to explain the extreme ultraviolet radiation conversion efficiency(EUV-CE) of a tin-based droplet target laser produced plasmas by calculating the laser absorption efficiency,radiation efficiency,and spectral efficiency.The dependence of drive laser pulse duration and laser intensity on EUV-CE is investigated.The results show that at some appropriate laser intensity,where the sum energy of the thermal conduction,out-off band radiation and plasma plume kinetic losses is at a minimum,the EUV-CE should reach a maximum.The EUV-CE predicted by the present simple model is also compared with the available experimental and simulation data and a fair agreement between them is found.
基金support from Guangdong Major Project of Basic and Applied Basic Research (No. 2019B030302003)Hubei Key Laboratory of Optical Information and Pattern Recognition open fund (No. 201908)。
文摘The Nd:YAG laser with a wavelength of 1.064 μm was used to generate plasmas on a high-purity solid ytterbium(70 Yb) target in a vacuum chamber. The soft x-ray time-and space-integration spectra from the Yb plasmas were measured in the wavelength range of 1.0–8.5 nm under different power densities. The atomic spectral data of the unresolved transition arrays from highly charged Yb ions were calculated based on Cowan's suite of codes, including configuration interaction. The calculated Gaussian envelope of the emission determined by the weighted spontaneous transition rates was compared with the experimental spectra, and a good agreement between them was obtained. The spatial-temporal evolutions of the plasmas under the experimental conditions are simulated based on the collisional-radiative model, enabling the understanding of the mechanism of the plasma conditions for optimal water window waveband emission output.
基金This work is supported by the National Key Research and Development Program of China(No.2017YFA0402300)National Natural Science Foundation of China(Nos.11874051,11564037,61741513,11904293)the Special Fund Project for Guiding Scientific and Technological Inno-vation of Gansu Province(No.2019zx-10).
文摘A state diagnosis of laser-produced plasma in air generated by a 1064 nm pulse laser was investigated by the Thomson scattering(TS)method.The evolutions of the electron temperature and electron density were obtained as a function of the time delay which ranged from 300-3200 ns.The heating effect produced by the 532 nm probe beam with different energies on the air plasma at different interaction times was further studied using a time-resolved optical emission spectroscopy technique.The influence of the probe beam on the electron density was found to be negligible,whereas its influence on electron temperature is evident.In addition,the heating effect of the probe beam on the plasma strongly depends on the energy of the probe beam,and gradually weakens with increasing time delay.Our results are helpful for further understanding the TS method and its application in plasma diagnostics.
