Generation of fast protons in moderate-intensity laser－plasma interaction from rear sheath

Forward fast protons are generated by the moderate-intensity laser--foil interaction. Protons with maximum energy 190~keV are measured by using magnetic spectrometer and CR-39 solid state track detectors along the direction normal to the rear surface. The experimental results are also modeled by the particle-in-cell method, investigating the time-varying electron temperature and the rear sheath field. The temporal and spatial structure of the sheath electrical field, revealed in the simulation, suggests that these protons are accelerated by target normal sheath acceleration (TNSA) mechanism.     

Near‐3‐MeV protons from target‐normal‐sheath‐acceleration femtosecond laser irradiating advanced targets

Advanced targets based on graphene oxide and gold thin film were irradiated at high laser intensity (10¹⁸–10¹⁹ W/cm²) with 50‐fs laser pulses and high contrast (10⁸) to investigate ion acceleration in the target‐normal‐sheath‐acceleration regime. Time‐of‐flight technique was employed with SiC semiconductor detectors and ion collectors in order to measure the ion kinetic energy and to control the properties of the generated plasma. It was found that, at the optimized laser focus position with respect to the target, maximum proton acceleration up to about 3 MeV energy and low angular divergence could be generated. The high proton energy is explained as due to the high electrical and thermal conductivity of the reduced graphene oxide structure. Dependence of the maximum proton energy on the target focal position and thickness is presented and discussed.     

Effects of non‐extensive electrons on the sheath of dusty plasmas with variable dust charge

In this study, a detailed investigation of the problem of sheath is presented using the fluid model in a magnetized three‐component dusty plasma system comprising positive ions, dust grains with variable charge and q‐non‐extensive electrons (i.e., the electrons evolve far away from their Maxwellian thermodynamic equilibrium [q = 1]). The effects of q‐non‐extensivity parameter on the plasma sheath parameters are studied numerically. A significant change is observed in the quantities characterizing the sheath with the presence of the super‐extensive electrons (q < 1) and sub‐extensive electrons (q > 1). In addition, based on the orbital motion limited theory, by taking various forces acting on the dust particle into consideration, the dynamics of the dust located within the sheath, that is, the dust grain charging inside the sheath, is examined under different values of q. It is found that the q‐non‐extensivity has affected significantly the dynamics and the charging process of the dust grains in the sheath.     

磁化等离子体的鞘层结构

采用流体方法数值研究了斜磁场作用下的等离子体鞘层结构.模拟结果显示磁场对鞘层结构有显著的影响,特别是在磁鞘边界附近离子的密度分布产生了明显的变化.分别讨论了离子垂直入射和斜入射两种情况,当离子斜入射进鞘层时,其运动情况要相对复杂一些.在适当的条件下,洛伦兹力的作用使离子在某些区域产生相对聚集,离子密度分布产生波动. 关键词： 鞘层 等离子体 磁场     

利用LIF法诊断微波等离子体鞘层

简要地阐明了利用激光诱导荧光法（ＬＩＦ）诊断等离子体特性的原理，分别对二能级情况（共振荧光）与三能级情况（非共振荧光）采用饱和荧光法测量粒子浓度的公式进行了推导。在此基础上，提出了利用ＬＩＦ法测量微波等离子体鞘层（特别是高压脉冲动态鞘层）的组分及其空间分布与能量分布的实验方法。     

钛型不锈钢焊条渣壁过渡形成条件的探讨

渣壁过渡是焊条金属熔滴理想的过渡形态。本文探讨了形成渣壁过渡的两个基本条件,并提出了钛型不锈钢焊条药皮成分,焊条外径影响熔滴过渡形态的关系图,以判断此类不锈钢焊条熔滴过渡形态,并指导其配方设计。     

仙客来(Cyclaman Persicum,Mill)组织培养中不定芽形态发生的组织细胞学研究

分别用仙客来种苗的子叶和叶柄作为外植体,培养在附加2,4 D、细胞分裂素和细胞激动素的1/2MS培养基上诱导不定芽的发生,研究了愈伤组织和不定芽形成过程中的组织细胞学变化.对两种不同外植体不定芽发生过程中的切片观察表明,两种外植体的组织脱分化始于维管束周围的维管束鞘细胞,随后开始分裂的是与其临近的薄壁细胞并能很快形成胚性分生细胞团.经30d左右的培养,进一步分化形成芽原基.子叶愈伤的芽原基通常出现在愈伤的边缘.叶柄脱分化比子叶快,不定芽可以起源于表层的分生细胞团,也可以由愈伤深处的分生组织分化而形成.     

脉冲偏压上升沿特性对等离子体浸没离子注入鞘层扩展动力学的影响

等离子体浸没离子注入(PIII)是用于材料表面改性的一种廉价高效、非视线的技术.采用等离子体粒子模型，通过假设电子密度服从Boltzmann分布，求解Poisson方程和Newton方程，跟踪离子在等离子体鞘层中的运动形态及特性并进行统计分析，研究了不同上升速率和形状的6种波形上升沿对鞘层时空演化、离子注入能量和剂量的影响.结果表明，在PIII过程中，脉冲上升沿影响了等离子体鞘层的扩展，且不同波形诱导的鞘层厚度间存在最大差值.电场强度在鞘层的外边缘区域存在陡降区，离子的运动为非匀加速过程.可以通过调整脉冲 关键词： 等离子体浸没离子注入 鞘层 粒子模型 上升沿     

110kV单芯电缆金属护套感应电压计算及分段

电缆线路较长时将引起过高的金属护套感应电压,从而降低电缆的使用寿命,并危及人身安全。建立三相线芯对屏蔽层感应电压计算模型,推导出单芯电缆金属护套的感应电压表达式,得到了正常运行条件下不同长度的单芯电缆线路感应电压。     

双螺旋辊式新型磨浆机螺旋套磨损机理的研究

利用金相组织分析和电子显微分析技术,结合生产实际,对已磨损的输料段和磨浆段的螺旋套进行磨损表面形貌分析,探讨螺旋套磨损机理.结果表明:输料段正螺旋套能够将纸浆料旋转送入机壳内,不承受较大的挤压应力,但由于纸浆料中含有腐蚀介质,其主要的磨损失效形式以腐蚀磨损为主,磨料磨损为辅;磨浆段反螺旋套本身无正输送能力,浆料在正输送组件作用下形成高压区,纤维与浆料之间产生较大摩擦力,导致纤维分离,进而使之分丝帚化和压溃,浆料水分降低,其主要的磨损失效形式为高应力磨料磨损,并伴有腐蚀磨损.