电磁脉冲辐射对小鼠睾丸血-睾屏障的影响

采用常规苏木精-伊红染色（Hematoxylin-Eosin staining,HE staining）、硝酸镧示踪电镜和埃文思兰（Evans Blue,EB）尾静脉注射三种方法,综合观察100kV／m和400kV／m两种不同强度电磁脉冲辐射对小鼠睾丸血-睾屏障的影响。三种方法观察结果基本一致,两种强度的电磁脉冲辐射均可造成小鼠睾丸支持细胞和血-睾屏障不同程度的损伤,400kV／m辐射组损伤更甚,辐射后1d即可见大量生精细胞的凋亡与坏死,支持细胞亦发生形态结构的变化,血-睾屏障严重损伤,随后大量第Ⅷ期生精小管内出现基底室与近腔室的分离,大量凋亡与坏死的生精细胞向管腔的排放,至辐射后21d仍可见到血-睾屏障损伤;100kV／m辐射组的损伤较400kV／m辐射组稍轻,辐射后14d支持细胞、生精上皮以及血-睾屏障的损伤已基本恢复。结果提示一定强度的电磁脉冲可以造成小鼠血-睾屏障的损伤,这种损伤呈辐射强度依赖性,并且与损伤后恢复时间相适应。     

瞬发γ光子在柱腔体中产生的内电磁脉冲

本文推导了柱二维初级电子的连续性方程和动量方程,给出用欧拉方法、拉格朗日法和质点网格方法分别计算的初级电流及其产生的内电磁脉冲。在弱电场(E≤10~4V/m)的条件下,这三种方法得到的结果与非自洽法的结果比较接近。     

烟羽辐射模拟装置的研制及测试

环境γ监测设备对小剂量率变化的灵敏度是评价其辐射特性的一项重要指标。本文介绍了一种自行研制的烟羽辐射模拟装置,该装置由137Cs放射源及其传动系统、铅屏蔽体、不同厚度的铅衰减环、控制单元等组成。利用蒙特卡罗模拟和G(E)函数法对距离装置放射源3 m、离地面1 m高度处的空气比释动能率进行了计算,由上述两种方法得到的结果相对偏差在5%以内。结果表明,此烟羽辐射模拟装置在装载MBq量级的137Cs源时,预计可提供10 nGy/h~50 nGy/h的辐射场,可用于环境γ监测设备对小剂量率变化的灵敏度测试。     

烟羽辐射模拟装置的研制及测试北大核心CSCD

环境γ监测设备对小剂量率变化的灵敏度是评价其辐射特性的一项重要指标。本文介绍了一种自行研制的烟羽辐射模拟装置,该装置由137Cs放射源及其传动系统、铅屏蔽体、不同厚度的铅衰减环、控制单元等组成。利用蒙特卡罗模拟和G(E)函数法对距离装置放射源3 m、离地面1 m高度处的空气比释动能率进行了计算,由上述两种方法得到的结果相对偏差在5%以内。结果表明,此烟羽辐射模拟装置在装载MBq量级的137Cs源时,预计可提供10 nGy/h^50 nGy/h的辐射场,可用于环境γ监测设备对小剂量率变化的灵敏度测试。     

瞬发γ光子在平板腔体中产生的内电磁脉冲

用非自洽和自洽方法计算、分析了在铝平板腔体中产生的电流和电磁脉冲。在弱电场强度E(E<10~4V/m)、小模型尺寸的条件下,用五种计算方法得到了比较接近的计算结果。     

电磁脉冲辐射对小鼠睾丸TGF-βs表达的影响

探讨转化生长因子-β(Transforming growth factor-β,TGF-β)超家族成员TGF-β1、TGF-β3和TGFβ-R1在电磁脉冲辐射后成年小鼠睾丸中的表达变化及其意义.采用场强为400 kV/m的辐射场对20只成年雄性Balb/c小鼠进行200次重复全身照射,另20只假照射,于辐射后1、7、1...     

核辐射条件下磁性器件的动态效应

核爆炸瞬间释放的中子、γ射线和核电磁脉冲对磁性材料及器件会产生各种影响,引起性能变化。中子能使磁性材料产生永久性损伤的主要原因是高能中子与材料相互作用使晶格原子产生位移效应。γ辐射可引起电离效应,产生瞬时光电流,对材料及器件造成瞬时干扰,甚至永久性损伤。静态实验证明,当中子流量达10~(16)中子/厘米~2、γ剂量率为10~8拉德(硅)/秒时,磁性器件的性能无显著改变。核爆瞬间,在相当大的范围内产生强大的电磁脉冲,其电场强度为10~4—10~5伏/米,脉冲波形持续时间为几百10~(-9)秒,频谱范围从10~2千赫兹到10~2兆赫兹。由于磁性器件外部屏蔽不完善或结构本身的孔隙,使外部电磁脉冲可以渗透到内部。即使屏蔽很完善,在几百公里范围内的强γ辐射也会在器件内部感生内电磁脉冲。这些都会干扰或破坏磁性器件的正常工作性能。因此在核辐射条件下,研究这些材料和器件的动态性能具有重要意义。     

基于电偶极子辐射模型的三维成像算法

提出了一种基于电偶极子辐射模型的三维成像算法.在研究后向投影算法原理的基础上,利用散射模型分析了近、远场成像的关系,提出先采用电偶极子辐射模型对采样数据进行近场化处理,再将处理后的数据反向投影到成像区域,获得成像图像.利用FDTD数值仿真实现对目标的三维成像,验证了算法的有效性,分析了耦合对成像效果的影响.     

电磁脉冲辐射场试验中的光纤传输测量系统

辐射波电磁脉冲模拟器是进行大型电子系统电磁脉冲效应试验研究的重要设备。针对辐射波电磁脉冲模拟器试验的特点及其对测量系统的要求,介绍了基于光纤传输的电磁脉冲测量系统的构成,测量系统的分类及测量系统的标定方法。并对电磁脉冲测量系统的不确定度评定方法进行了讨论。通过辐射场试验,给出了测量系统的应用实例及对测量结果的分析。     

两种分布加载电磁脉冲天线的FDTD方法模拟

为了研究电磁脉冲(EMP)对各种电子系统的效应规律，需要设计一种合适的EMP辐射天线。采用时域有限差分(FDTD)方法考察了柱形和锥形两种分布加载行波天线的瞬态辐射特性，详细讨论了各种天线参数对辐射特性的影响。给出了FDTD模拟天线瞬态辐射过程的关键算法，并将计算结果与公开文献进行了比较，证明了结论的可靠性。     

Asymmetry of Neoclassical Transport by Dipole Electric Field

Effects of dipole electric fields on neoclassical transport are studied. Large asymmetry in transport is created. The dipole fields, which are in a negative R-direction, reduce the ion drift, increase electron drift, and change the steps of excursion due to collisions. It is found that different levels of dipole field intensities have different types of transport, For the lowest level of the dipole field, the transport returns to the neoclassical one. For the highest level of the dipole field, the transport is turned to be the turbulence transport similar to the pseudo-classical transport. Experimental data may be corresponded to a large level of the dipole field intensity.     

Equilibrium Reconstruction of Anisotropic Pressure Profile in the Levitated Dipole Experiment

The Levitated Dipole Experiment (LDX) is an innovative confinement concept that uses an internal superconducting dipole field to confine plasma. Plasma equilibrium is calculated by a least-squares fit of an anisotropic pressure model to magnetic measurements constrained by X-ray images. Reconstructions have been done for different heating schemes using two-frequency electron cyclotron heating at 2.45 and 6.4 GHz. Results show that a maximum local β ∼ 20% has been achieved using two frequency heating at a combined full power of 5 kW. Analysis of the reconstruction results shows that the magnetic sensors are sensitive primarily to changes in the plasma dipole moment. This is partly due to the fact that the dipole current decreases as the plasma current increases (as required by flux conservation through the superconducting dipole) and the magnetic sensors detect the sum of these changes. This paper will present details of the reconstruction procedure and describe how new magnetic sensors will aid in resolving the pressure profile more accurately.     

Novel Dipole Trapped Spheromak Configuration

We report the observation and characterization of a spheromak formed in the Swarthmore Spheromak Experiment (SSX) and trapped in a simple dipole magnetic field. The spheromak is studied in the prolate (tilt unstable) 0.4 m diameter, L = 0.6 m length copper flux conserver in SSX. This configuration is stable to the tilt, despite the prolate flux conserver. The spheromak is characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), ion Doppler spectroscopy for T _i and flow, interferometry for n _e , and soft X-ray analysis for T _e . Three dimensional MHD simulations of this configuration verify its gross stability.     

Study of possibilities for a spin flip in high energy electron ring HERA

In a high energy electron ring the spins of electrons become spontaneously polarized via the emission of spin-flip synchrotron radiation. By employing a radio frequency radial dipole field kicker, particle spin directions can be rotated slowly over many turns. A model which couples three dimensional spin motion and longitudinal particle motion was constructed to describe nonequilibrium spin dynamics in high energy electron storage rings. The effects of a stochastic synchrotron radiation on the orbital motion in the accelerator synchrotron plane and its influence on the spin motion are studied. The main contributions to the spin motion, the synchrotron oscillations and the stochastic synchrotron radiation, have different influence on the spin polarization reversal in different regions of the parameter space. The results indicate that polarization reversal might be obtained in high energy electron storage rings with a significant noise even with relatively small strengths of a perturbing magnetic field. The only experimental datum available agrees with the model prediction, however further experimental data would be necessary to validate the model.     

Conceptual design of Dipole Research Experiment (DREX)

A new terrella-like device for laboratory simulation of inner magnetosphere plasmas,Dipole Research Experiment,is scheduled to be built at the Harbin Institute of Technology (HIT),China,as a major state scientific research facility for space physics studies.It is designed to provide a ground experimental platform to reproduce the inner magnetosphere to simulate the processes of trapping,acceleration,and transport of energetic charged particles restrained in a dipole magnetic field configuration.The scaling relation of hydromagnetism between the laboratory plasma of the device and the geomagnetosphere plasma is applied to resemble geospace processes in the Dipole Research Experiment plasma.Multiple plasma sources,different kinds of coils with specific functions,and advanced diagnostics are designed to be equipped in the facility for multi-functions.The motivation,design criteria for the Dipole Research Experiment experiments and the means applied to generate the plasma of desired parameters in the laboratory are also described.     

The Compact Levitated Dipole Configuration for Plasma Confinement

A new magnetic configuration for magnetic confinement of fusion plasmas is proposed. This configuration is closely related to the levitated dipole configuration, and shares the same mechanism for plasma stability. The difference between the two configurations rests in the use of shaping coils to alter the far field region of the dipole field, resulting in greatly reduced total reactor volume given equivalent plasma parameters and core volume. In this paper we will discuss the magnetic geometry of the compact levitated dipole configurations and employ stability theory in the low beta limit to predict its properties.     

Investigation of the Possibility of Using UNK Superconducting Dipole Magnets for Producing Rapid-Cycling Magnetic Fields

The superconducting dipoles developed as part of the UNK project have reached a magnetic field 6 T at a rate of up to 0.8 T/sec. Experimental data are presented on the conditioning, rate dependences, and dynamic losses for magnets with two types of superconducting cable (zebra and oxide). Possible ways to decrease the heat release in a dipole operating in rapid-cycling magnetic fields are examined. The results of an analysis of heat release and temperature conditions are presented for a dipole with a winding made of improved current-carrying components.     

Effects of resonant magnetic perturbations on the loss of energetic ions in tokamak pedestal

Resonant magnetic perturbations (RMPs) are extensively applied to mitigate or suppress the edge localized mode in tokamak plasmas, but will break the axisymmetric magnetic field configuration and increase the loss of energetic ions. The mechanism of RMPs induced energetic ion loss has been extensively studied, and is mainly attributed to resonant effects. In this paper, in the perturbed non-axisymmetric tokamak pedestal, we analytically derive the equations of guiding center motion for energetic ions including the bounce/transit averaged radial drift velocity and the toroidal precession frequency modified by strong radial electric field. The loss time of energetic ions is numerically solved and its parametric dependence is analyzed in detail. We find that passing energetic ions cannot escape from the plasma, while deeply trapped energetic ions can escape from the plasma. The strong radial electric field plays an important role in modifying the toroidal precession frequency and resulting in the drift loss of trapped energetic ions. The loss time of trapped energetic ions is much smaller than the corresponding slowdown time in DIII-D pedestal. This indicates that the loss of trapped energetic ions in the perturbed non-axisymmetric pedestal is important, especially for the trapped energetic ions generated by perpendicular neutral beam injection.     

Effect of Ion Engine Exhaust on the Radiation Field of a Dipole Antenna Part I: Infinite Slab Model for the Exhaust Ion Beam

A theory of the effect of an ion rocket engine exhaust on the radiation pattern of a dipole antenna is presented. The electromagnetic equations are combined with those describing the exhaust plasma beam to calculate its equivalent effective dielectric constant. In part I of this paper, the beam is represented by an infinite slab of a homogenous plasma medium, as is usually considered in space charge neutralization studies of this type of engine. The equations of propagation of electromagnetic waves through the beam medium, are used to calculate the total dipole radiation field. The method of steepest descent is applied for the evaluation of the integrals. It is found that the dipole radiation pattern depends greatly on the beam characteristic parameters.