Thomson scattering (TS), as a popular and reliable diagnostic technique, has successfully measured electron temperatures and electron number densities of plasmas for many years. However, conventional TS techniques usi...Thomson scattering (TS), as a popular and reliable diagnostic technique, has successfully measured electron temperatures and electron number densities of plasmas for many years. However, conventional TS techniques using Nd:YAG lasers operate only at tens of hertz. Here, we present the development of a high-repetition-rate TS instrument based on a high-speed, pulse-burst laser system to greatly increase the temporal resolution of measurements. Successful instrument prototype testing was carried out by collecting TS light from laboratory helium and argon plasmas at 10 kHz. Calibration of the instrument detection sensitivity using nitrogen/ oxygen rotational Raman scattering signal is also presented. Quantitative electron number densities and electron temperatures of the plasma were acquired at 10 kHz, for stable plasma discharges as, respectively,~0.9 eV and ~5.37×10^21 m^-3 for the argon plasma, and ~1 eV and ~6.5×10^21 m^-3 for the helium plasma.展开更多
Dielectrics with high permittivity and temperature stability are important for the development of high-temperature multilayer ceramic capacitors(MLCCs).In this study,Ca_(1-x)Na_(x)Ti_(1-x)Nb_(x)SiO_(5)(abbreviated as ...Dielectrics with high permittivity and temperature stability are important for the development of high-temperature multilayer ceramic capacitors(MLCCs).In this study,Ca_(1-x)Na_(x)Ti_(1-x)Nb_(x)SiO_(5)(abbreviated as CTS-x NN)ceramics were prepared by solid-phase reaction method.The introduction of NN weakens the long-range ordered displacement of Ti,leading to a significant increase in the dielectric temperature stability.The CTS-2%NN samples exhibit high permittivity(53)and TCC≤±170 ppm/℃in the range of-55℃to 300℃.The CTS-based ceramics behave high dielectric temperature stability.In addition,the bandgap of the CTS-based ceramics increased significantly,which is favorable for improving the breakdown strength of the material.For x=4%samples,the breakdown strength reaches 621kV/cm.Thus,the designed CTS-based dielectrics are promising for high-temperature capacitors.展开更多
As the effect of climate plays a significant role in corona discharge under combined voltages,the variation of corona inception voltage with different air pressure and humidities is studied.An experimental platform,ba...As the effect of climate plays a significant role in corona discharge under combined voltages,the variation of corona inception voltage with different air pressure and humidities is studied.An experimental platform,based on a rod-to-plane electrode,is constructed with adjustable air pressure from 0.06 MPa to 0.10 MPa and with a relative humidity(RH)from 20%to 90%.The variation of ultraviolet(UV)photon count and corona inception voltage is obtained at various climate conditions under different applied voltages:the single AC,single DC,and combined AC-DC.It turns out that all the corona inception voltages decline with the drop of air pressure and the rise of humidity under different applied voltages.The influence between different voltages primarily relies on space charge,as more AC components make it easier to accumulate positive ions.The existence of AC makes ions move forward and backward while the existence of DC dominates the polarity of corona and general drift directions.At last the fitting formula of hybrid corona inception voltage combining air pressure and relative humidity is given.展开更多
基金supported by the US Department of Energy’s STTR program under Grant No.DE-SC0018672(Program Manager:Dr Matthew Lanctot)
文摘Thomson scattering (TS), as a popular and reliable diagnostic technique, has successfully measured electron temperatures and electron number densities of plasmas for many years. However, conventional TS techniques using Nd:YAG lasers operate only at tens of hertz. Here, we present the development of a high-repetition-rate TS instrument based on a high-speed, pulse-burst laser system to greatly increase the temporal resolution of measurements. Successful instrument prototype testing was carried out by collecting TS light from laboratory helium and argon plasmas at 10 kHz. Calibration of the instrument detection sensitivity using nitrogen/ oxygen rotational Raman scattering signal is also presented. Quantitative electron number densities and electron temperatures of the plasma were acquired at 10 kHz, for stable plasma discharges as, respectively,~0.9 eV and ~5.37×10^21 m^-3 for the argon plasma, and ~1 eV and ~6.5×10^21 m^-3 for the helium plasma.
基金supported by the National Key Research and Development Program of China(No.2021YFB3800604).
文摘Dielectrics with high permittivity and temperature stability are important for the development of high-temperature multilayer ceramic capacitors(MLCCs).In this study,Ca_(1-x)Na_(x)Ti_(1-x)Nb_(x)SiO_(5)(abbreviated as CTS-x NN)ceramics were prepared by solid-phase reaction method.The introduction of NN weakens the long-range ordered displacement of Ti,leading to a significant increase in the dielectric temperature stability.The CTS-2%NN samples exhibit high permittivity(53)and TCC≤±170 ppm/℃in the range of-55℃to 300℃.The CTS-based ceramics behave high dielectric temperature stability.In addition,the bandgap of the CTS-based ceramics increased significantly,which is favorable for improving the breakdown strength of the material.For x=4%samples,the breakdown strength reaches 621kV/cm.Thus,the designed CTS-based dielectrics are promising for high-temperature capacitors.
基金supported by the National Natural Science Foundation of China(51877082)Fok Ying-Tong Education Foundation(151058)the Fundamental Research Funds for the Central Universities(2019MS011).
文摘As the effect of climate plays a significant role in corona discharge under combined voltages,the variation of corona inception voltage with different air pressure and humidities is studied.An experimental platform,based on a rod-to-plane electrode,is constructed with adjustable air pressure from 0.06 MPa to 0.10 MPa and with a relative humidity(RH)from 20%to 90%.The variation of ultraviolet(UV)photon count and corona inception voltage is obtained at various climate conditions under different applied voltages:the single AC,single DC,and combined AC-DC.It turns out that all the corona inception voltages decline with the drop of air pressure and the rise of humidity under different applied voltages.The influence between different voltages primarily relies on space charge,as more AC components make it easier to accumulate positive ions.The existence of AC makes ions move forward and backward while the existence of DC dominates the polarity of corona and general drift directions.At last the fitting formula of hybrid corona inception voltage combining air pressure and relative humidity is given.
