上海光源增强器动态升能过程分析

上海光源增强器采用FODO型磁聚焦结构, 由28个FODO单元组成, 周长180m, 可将直线加速器引出的100MeV的电子束加速至3.5GeV, 用于储存环的注入, 重复频率为2Hz. 增强器的动态升能过程将直接影响到储存环的注入效率. 报告上海光源增强器动态升能过程中磁铁磁场、高频电压的上升过程、涡流效应及影响以及束流参数的变化等.     

利用平均场法计算里德堡原子的 偶极阻塞效应

利用平均场法计算了里德堡原子的偶极相互作用,分析了主量子数、拉比频率以及原子密度等对偶极阻塞效应的影响。随着主量子数以及原子密度的增大,原子间的相互作用增强,里德堡原子的偶极阻塞效应越明显;激光功率的增加,能提高里德堡原子的激发几率,但激发几率会趋于饱和,此时里德堡原子间的偶极阻塞效应最为显著。里德堡原子的偶极阻塞效应广泛应用于量子信息等领域。     

tune调制对储存环横向稳定性影响的模拟研究

对包含非线性六极场储存环的线性tune(Qx,Qy)加以余弦调制,通过计算粒子轨道沿相角畸变的动力学孔径,研究了tune调制对储存环中粒子运动横向稳定性的影响.从模拟结果可以看出,tune调制对粒子稳定性的影响是一种长期效应.当调制振幅很小、调制tune远离共振岛tune值时,对粒子稳定性的影响很小,随着调制振幅增大,调制tune接近共振岛tune,影响越来越明显.     

位移测量中真空室偶极涡流的影响及其扣除

一、真空室上偶极涡流对测量的影响 在托卡马克放电中,出现宏观不稳定性时,等离子体电流会出现小的正尖峰,并在整个大环上沿水平方向向内快速收缩。这时真空室(薄不锈钢壳)上会感应出很大偶极涡流,如图1所示,真空室上偶极电流分布为     

托卡马克极向场线圈的优化方法

托卡马克等离子体的三角形变和拉长比对约束和磁流体稳定性有很强的影响，因此在托卡马克装置极向场设计中，在基于物理和工程考虑所预先选定的等离子体平衡位形几何参数下，如何优化确定外部极向场线圈位置和电流，是一个具有重要实际意义的研究课题.为优化确定托卡马克极向场线圈，给出了一个有效的多变量平衡优化方法，能以事先规定的等离子体平衡位形的一些几何参数为目标函数，优化确定极向场线圈位置和电流.并应用它于HT-7U平衡位形计算，得到了所需的结果. 关键词： 等离子体平衡 极向场线圈 优化     

水下低频振荡涡流场声散射调制机理与特性研究

水下涡流场对声波的散射问题是声波在复杂流场中传播的基本问题,在水下目标探测和流场声成像领域具有重要意义.针对水下低频振荡涡流场声散射调制问题建立了理论分析模型与数值计算方法,探究了其声散射调制声场的产生机理与时空频特性.首先,基于运动介质的波动方程,通过引入势函数将波动方程分解为流声耦合项和非耦合项,并对流声耦合项进行频域分析处理,揭示了水下振荡涡流场的声散射调制机理;其次,采用间断伽辽金数值方法对水下低频振荡涡流场中声传播过程进行了数值模拟,分析了低马赫数条件下,不同入射声波频率、涡流场的振荡频率和涡核尺度对涡流场声散射调制声场时空频特性的影响规律,并结合理论分析模型对其特性进行了解释.研究表明:低马赫数下,振荡涡流场对声波的散射可产生包含涡流场振荡频率双边带调制谐波的散射调制声场,且随着入射声波频率、涡核尺度的增大,散射调制声场强度增强,总散射声场空间分布具有对称性和明显主瓣,且主瓣方位角趋近于入射波传播方向;在频率比远大于1条件下,涡流场振荡频率对散射调制声场强度影响较小.     

Kerr效应对压缩光场中二能级原子系统偶极压缩的影响

研究了在考虑Ｋｅｒ效应的情况下，单个二能级原子与压缩相干态辐射场相互作用中原子的偶极压缩效应，讨论了Ｋｅｒ效应以及其它一些因素，诸如失谐量、相干振幅分量、初始压缩光场的压缩参量等对原子偶极压缩行为产生的不同影响。     

EAST极向场线圈及磁测量系统的修正

采用网格法计算空间磁场,应用最小二乘法优化极向场线圈、单匝环、磁探针位置参数及标定系数获得了更准确的位置坐标,明显地改善了磁场和磁通的计算误差,也为等离子体平衡反演算法提供更准确的格林函数。     

铁芯变压器对极向场的影响

本文叙述了对HL-1装置铁芯变压器作无限长均匀磁化假定后,给出了极向场线圈(包括等离子体电流环)在空气区产生的磁场解析表达式,及数值计算,并在一比四模拟变压器上做了实验,计算结果与实验结果符合。     

两个原子与双模腔场多光子相互作用过程中光场的相位性质

研究了偶极－偶极关联的两个全同二能级原子与双模强相干光场多光子共振相互作用过程中光场相位的演化性质,分别讨论了三种不同原子初态下,初态场强度和原子间偶极相互作用对光场相位概率分布,相位扩散及频率漂移的影响。     

超导磁共振主磁体励磁测控系统设计与开发

医用超导磁共振主磁体在励磁过程中出现的交流损耗和传导漏热等情况,是超导磁体失超的根本原因;为了控制和保证励磁过程的稳定性、可靠性和安全性,开发和完善励磁的测控系统就显得格外重要;设计并开发了基于LabVIEW平台的超导磁共振主磁体励磁测控系统;系统数据通过在虚拟仪器平台上调用动态链接库文件(DLL),控制泰克公司KE2700系列集成式采集卡采集得到;传感器选择根据相应功能需要配置;操作台仪器控制、数据采集程序和人机界面由LabVIEW编写;搭配保护电路,保护超导线圈,降低失超损失;实现数据采集、参数控制、失超保护、匀场测试等功能。系统满足设计开发目的,平台搭建稳定可靠;功能相对完善,具体操作简易,交互界面友好,后期修改和功能扩展灵活;经工程实际运行测试验证,提高了研究和工作效率,达到设计要求,有实际应用价值。     

Effect of pulse magnetic field stimulation on calcium channel current

This study aimed to investigate the effect of low frequency and high amplitude pulse magnetic field (PMF) on Calcium ion channel current of cells. Measurements were done on the Human Embryonic Kidney 293 cells (HEK 293), which have only Calcium ion channels functioning. The whole cell current was measured by patch clamp method, with the clamped voltage ramping from −90 mV to +50 mV across the cell membrane. A PMF was generated by a 400-turn coil connected to a pulse current generator. The frequency of the pulse was 7 Hz, the width of the pulse was 3 ms, and the amplitude of the pulse, or the flux density, was ranging from 6 to 25 mT. The results showed that the profile of the whole cell Calcium channel current could be modified by the PMF. With the PMF applied, the phase shifting occurred: the onset of the channel opening took place several mili-seconds earlier than that without the PWF and correspondingly, the whole cell current reached its maximum earlier, and the current returned back to zero earlier as well. When the PWF was stopped, these effects persisted for a period of time, and then the current profile “recovered” to its original appearance. The decrease of the onset time and peak current time could be due to the local electric potential induced by the PWF and the direct interaction between PMF and ion channels/ions. The exact mechanisms of the observed effects of PMF on the cell are still unknown and need to be further studied.     

A possible gravity measurement with antihydrogen

A neutral probe such as antihydrogen offers appealing experimental advantages, compared to a charged probe such as antiproton, for a measurement of the gravitational behaviour of antimatter. The feasibility of this approach is preliminarily investigated. A direct extension of the sextupolar ring technique used by Paul is not feasible but the use of a straight sextupole seems to be promising.     

Runaway Electron Beam Instability in Slide-Away Discharges in the HT-7 Tokamak

Slide-away discharges are achieved by decreasing the plasma density or ramping down the plasma current in runaway discharges in the HT-7 tokamak. In the case of plasma current ramp down, the ratio of the electron plasma frequency to the electron cyclotron frequency is higher than in the stationary pulses when the discharge goes into a slide-away regime. The instability regime is characterized by relaxations in the electron cyclotron emission due to relativistic anomalous Doppler effect which transfers energy from parallel to perpendicular motion. The triggering of relativistic anomalous Doppler effect at higher density by ramping down of plasma current may provide a alternative runaway energy control scenario.     

高温超导无绝缘线圈励磁电压特性研究

本文通过实验研究了焊锡浸渍、励磁电流PI控制、励磁速率以及励磁幅值对高温超导无绝缘线圈励磁电压特性的影响。实验结果表明:高温超导无绝缘线圈励磁电压具有时延特性,焊锡浸渍、励磁电流PI控制分别会增大和减小时延特性,而励磁速率和励磁幅值不会影响时延特性;励磁电压幅值随励磁速率增大而增大;焊锡浸渍可降低励磁电压幅值,而励磁电流控制对励磁电压幅值影响不明显。     

合肥光源储存环束流软慢加速控制

 合肥光源储存环为非满能量注入,束流以200MeV的能量注入到储存环后慢加速到800MeV。介绍了慢加速的理论依据及储存环主电源控制系统的硬件结构,详细描述了束流软慢加速方法中的慢加速表计算及慢加速过程控制。机器运行结果表明:软慢加速方法控制灵活,慢加速过程运行平稳,束流损失很少,能很好地满足合肥光源机器运行和研究的需要。     

Multiphysics modelling of the separation of suspended particles via frequency ramping of ultrasonic standing waves

A model was developed to determine the local changes of concentration of particles and the formations of bands induced by a standing acoustic wave field subjected to a sawtooth frequency ramping pattern. The mass transport equation was modified to incorporate the effect of acoustic forces on the concentration of particles. This was achieved by balancing the forces acting on particles. The frequency ramping was implemented as a parametric sweep for the time harmonic frequency response in time steps of 0.1 s. The physics phenomena of piezoelectricity, acoustic fields and diffusion of particles were coupled and solved in COMSOL Multiphysics? (COMSOL AB, Stockholm, Sweden) following a three step approach. The first step solves the governing partial differential equations describing the acoustic field by assuming that the pressure field achieves a pseudo steady state. In the second step, the acoustic radiation force is calculated from the pressure field. The final step allows calculating the locally changing concentration of particles as a function of time by solving the modified equation of particle transport. The diffusivity was calculated as function of concentration following the Garg and Ruthven [1] equation which describes the steep increase of diffusivity when the concentration approaches saturation. However, it was found that this steep increase creates numerical instabilities at high voltages (in the piezoelectricity equations) and high initial particle concentration. The model was simplified to a pseudo one-dimensional case due to computation power limitations. The predicted particle distribution calculated with the model is in good agreement with the experimental data as it follows accurately the movement of the bands in the centre of the chamber.     

低起始温度的线性升温热处理对直拉硅中氧沉淀的影响

研究了直拉硅片从不同的温度线性升温(Ramping)到750℃,然后在750℃退火64 h过程中的氧沉淀行为. 结果表明,Ramping对硅片中氧沉淀的形成有明显的促进作用,且起始温度越低促进作用越强. 这是因为在Ramping处理中,低温(450—650℃)热处理阶段氧的扩散速率显著增强,促进了氧沉淀核心的形成,且较低的Ramping升温速率有利于氧沉淀核心的稳定和继续长大. 进一步的实验结果还表明,低起始温度的Ramping处理可应用于硅片的内吸杂工艺,能促进氧沉淀的生成提高硅片的内吸杂能力,减少热预 关键词： 直拉硅 氧沉淀 退火     

Effects of an applied low frequency field on the dynamics of a two-level atom interacting with a single-modefield

The effects of an applied low frequency field on the dynamics of a two-level atom interacting with a single-mode field are investigated. It is shown that the time evolution of the atomic population is mainly controlled by the coupling constants and the frequency of the low frequency field, which leads to a low frequency modulation function for the time evolution of the upper state population. The amplitude of the modulation function becomes larger as the coupling constants increase. The frequency of the modulation function is proportional to the frequency of the low frequency field, and decreases with increasing coupling constant.