微波诱导等离子体合成纳米α-Fe-氧化铁-碳化铁粉料

微波诱导等离子体合成纳米α－Ｆｅ－氧化铁－碳化铁粉料刘洪波（广东石油化工高等专科学校广东茂名５２５０００）关键词微波诱导等离子体纳米微晶α－Ｆｅ氧化铁碳化铁中图分类号Ｏ６１４．８１１近年来，纳米粉体材料的制备和应用研究十分活跃。这是由于纳米粉料（又称...     

高倍聚光太阳模拟器的设计

研究了一种高倍聚光、高均匀性太阳模拟器,它主要由短弧氙灯、椭球聚光镜、高速快门和积分器构成,辐射功率超过5 kW,辐射峰值超过1 800个太阳常数（标准AM1.5∶1太阳常数=1 kW/m2）。介绍了该模拟器的光学设计,主要工程特点和仿真结果。应用蒙特卡洛光线追迹技术优化几何配置,以使光源到目标面的辐射能量转换效率最大化。仿真结果显示：在直径20 mm的圆形目标区域其平均辐射超过1 000 kW/m2,相应的辐照不均匀度小于6%。利用该装置模拟了高倍聚光太阳系统的辐射特性,为研究高效率太阳能电池的热化学过程和测试先进的高温材料提供了实验平台。     

大面积准直型太阳模拟器的设计与研制

设计并研制了一种大面积准直型太阳模拟器,其有效辐照面直径达到1 100 mm,平均辐照度达到1.3个太阳常数（AM0）,光束准直角为±1.59°。首先给出了太阳模拟器的光学系统,分别从光源选择和布局,椭球镜设计和准直镜设计进行了阐述;介绍了太阳模拟器的光机结构;进行了系统的仿真和实现。实验表明,太阳模拟器的平均辐照度达到1 760 W/m²,辐照不均匀度达到±4.6%,辐照体不均匀度达到±5.96%,辐照不稳定度达到±1.36%,光谱匹配在300~1 400 nm波长范围内满足ASTM E927-10中AM0 B级要求,为航天有效载荷的热真空试验和热平衡试验提供了一个准确可靠的平台。     

Linear analysis of plasma pressure-driven mode in reversed shear cylindrical tokamak plasmas

The linear behavior of the dominant unstable mode ($m=2$, $n=1$) and its high order harmonics ($m=2n$, $n\ge 2$) are numerically investigated in a reversed magnetic shear cylindrical plasma with two $q=2$ rational surfaces on the basis of the non-reduced magnetohydrodynamics (MHD) equations. The results show that with low beta (beta is defined as the ratio of plasma pressure to magnetic field pressure), the dominant mode is a classical double tearing mode (DTM). However, when the beta is sufficiently large, the mode is driven mainly by plasma pressure. In such a case, both the linear growth rate and mode structures are strongly affected by pressure, while almost independent of the resistivity. This means that the dominant mode undergoes a transition from DTM to pressure-driven mode with the increase of pressure, which is consistent with the experimental result in ASDEX Upgrade. The simulations also show that the distance between two rational surfaces has an important influence on the pressure needed in mode transition. The larger the distance between two rational surfaces, the larger the pressure for driving the mode transition is. Motivated by the phenomena that the high-$m$ modes may dominate over low-$m$ modes at small inter-resonance distance, the high-$m$ modes with different pressures and $q$ profiles are studied too.