There are two different definitions for specifying the mean effective ion charge Zeff in plasmas： a） from the Spizer electrical resistivity of the plasma and b） from bremsstrahlung radiation losses of the plasma. I...There are two different definitions for specifying the mean effective ion charge Zeff in plasmas： a） from the Spizer electrical resistivity of the plasma and b） from bremsstrahlung radiation losses of the plasma. In this paper Zeff in the centre of tokamak ohmic discharges has been determined from information on sawtooth-relaxations of the steady state plasma, based on the analysis for the power balance of the plasma electrons in the plasma centre during the period of recovery after the sawtooth crashes. This method is found to supply reliable results for tokamak parameters. While its application requires some efforts in data analysis, it can provide a reliable determination of Zeff, independent of the information from bremsstrahlung radiation losses of the plasma.展开更多
High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been co...High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been considered as a promising alternative to overcome the limitations of ferromagnetic skyrmions,such as the skyrmion Hall effect and stray magnetic field.Here,by using the Lorentz transmission electron microscopy,the interconversion between the single domain,labyrinth domain and skyrmion state can be observed by the combined manipulation of electric current and magnetic field in a Hall balance(a SAF with the core structure of[Co/Pt]_(4)/NiO/[Co/Pt]_(4)showing perpendicular magnetic anisotropy).Furthermore,high-density room temperature skyrmions can be stabilized at zero field while the external stimulus is removed and the skyrmion density is tunable.The generation and manipulation method of skyrmions in Hall balance in this study opens up a promising way to engineer SAF-skyrmion-based memory devices.展开更多
基于Ga N高电子迁移率晶体管（HEMT）技术,研制了在0.8-4 GHz频率下,输出功率大于50 W的宽带平衡式功率放大器。采用3 d B耦合器电桥构建平衡式功率放大器结构;采用多节阻抗匹配技术设计了输入/输出匹配网络,实现了功率放大器的宽带特性...基于Ga N高电子迁移率晶体管（HEMT）技术,研制了在0.8-4 GHz频率下,输出功率大于50 W的宽带平衡式功率放大器。采用3 d B耦合器电桥构建平衡式功率放大器结构;采用多节阻抗匹配技术设计了输入/输出匹配网络,实现了功率放大器的宽带特性;采用高介电常数Al2O3基材实现了小型化功率放大器单元;采用热膨胀系数与Si C接近的铜-钼-铜载板作为Ga N HEMT管芯共晶载体,防止功率管芯高温工作过程中因为热膨胀而烧毁。测试结果表明,在0.8-4 GHz频带内,功率放大器功率增益大于6.4 d B,增益平坦度为±1.5 d B,饱和输出功率值大于58.2 W,漏极效率为41%-62%。展开更多
基金Project supported by the Nuclear Science Foundation （Grant No1997517）.
文摘There are two different definitions for specifying the mean effective ion charge Zeff in plasmas： a） from the Spizer electrical resistivity of the plasma and b） from bremsstrahlung radiation losses of the plasma. In this paper Zeff in the centre of tokamak ohmic discharges has been determined from information on sawtooth-relaxations of the steady state plasma, based on the analysis for the power balance of the plasma electrons in the plasma centre during the period of recovery after the sawtooth crashes. This method is found to supply reliable results for tokamak parameters. While its application requires some efforts in data analysis, it can provide a reliable determination of Zeff, independent of the information from bremsstrahlung radiation losses of the plasma.
基金supported by the Science Center of the National Science Foundation of China(Grant No.52088101)the National Natural Science Foundation of China(Grant Nos.11874408,52130103,51901025,and 11904025)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33030100)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.CAS Y201903)。
文摘High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been considered as a promising alternative to overcome the limitations of ferromagnetic skyrmions,such as the skyrmion Hall effect and stray magnetic field.Here,by using the Lorentz transmission electron microscopy,the interconversion between the single domain,labyrinth domain and skyrmion state can be observed by the combined manipulation of electric current and magnetic field in a Hall balance(a SAF with the core structure of[Co/Pt]_(4)/NiO/[Co/Pt]_(4)showing perpendicular magnetic anisotropy).Furthermore,high-density room temperature skyrmions can be stabilized at zero field while the external stimulus is removed and the skyrmion density is tunable.The generation and manipulation method of skyrmions in Hall balance in this study opens up a promising way to engineer SAF-skyrmion-based memory devices.
文摘基于Ga N高电子迁移率晶体管（HEMT）技术,研制了在0.8-4 GHz频率下,输出功率大于50 W的宽带平衡式功率放大器。采用3 d B耦合器电桥构建平衡式功率放大器结构;采用多节阻抗匹配技术设计了输入/输出匹配网络,实现了功率放大器的宽带特性;采用高介电常数Al2O3基材实现了小型化功率放大器单元;采用热膨胀系数与Si C接近的铜-钼-铜载板作为Ga N HEMT管芯共晶载体,防止功率管芯高温工作过程中因为热膨胀而烧毁。测试结果表明,在0.8-4 GHz频带内,功率放大器功率增益大于6.4 d B,增益平坦度为±1.5 d B,饱和输出功率值大于58.2 W,漏极效率为41%-62%。
