IH型漂移管直线加速器的束流动力学研究（英文）

为了提高兰州重离子加速器冷却储存环（HIRFL-CSR）的运行效率、改善加速器输出束流品质,并实现几个加速装置分时供束,提高整个重离子加速装置的利用率,特为（HIRFL-CSR）增建一台新的注入器--CSRLINAC。在108.48 MHz的RFQ之后的CSR-LINAC主加速段,主要由一台108.48 MHz和两台216.96 MHz的IH型漂移管直线加速器组成,用于加速荷质比为1/8.5~1/3之间的重离子,其最大的束流流强为3 mA,并将粒子从0.3 MeV/u加速到3.71 MeV/u。运用KONUS动力学原理,在满足设计指标的情况下,首先利用TraceWin程序进行中能束线MEBT设计,后针对高频腔体设计和束流匹配的基本参数的系列讨论,特别是对CSR-LINAC的中能束流匹配线、参数选择和IH型KONUS结构的漂移管直线加速器进行设计模拟优化。最终得出,在保证腔体设计指标和95.3%的传输效率的情况下,该紧凑型直线加速结构经过三个腔体的加速后,束流的纵向归一化均方根发射度增长仅有25%;同时发现,当流强达到3 mA时,存在空间电荷效应,导致其纵向相宽增长约25%,最大横向包络也存在16.5%的涨落。In order to improve the operation efficiency of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), a heavy ion linac (linear accelerator) was proposed and designed as a new injector for HIRFL-CSR. Following the 108.48 MHz Radio-Frequency Quadrupole (RFQ), three tanks in total with Interdigital H-mode drift tube linac (IH-DTL) structure are installed to boost the beam energy from 0.3 to 3.71 MeV/u, and the beam current of ions with charge-to-mass ratio from 1/8.5 to 1/3 can reach to 3 mA. The first tank operatesat the same frequency as the RFQ, and the rest two operate at 216.96 MHz. The “Combined Zero-Degree Synchronous Particle Structure” (KONUS) beam dynamics was used in the beam dynamics design. The overview of the physics design on the main accelerating components, including RF design and beam dynamics design are introduced in this paper. The optimized structure design, fabrication status and simulation results are presented in this contribution. It shows that under the condition of assurance of 95.3% transmission efficiency, the normalized rms emittance is about 25%. When the beam current is up to 3 mA, owing to the space charge effect, the increase of longitudinal phase spread and transverse envelope are about 25% and 16.3%, respectively.     

A transverse electric current in triglycine sulphate ferroelectric crystal

The application of a prolonged transverse electric field at a temperature T_A < T_C leads to unexpected qualitative changes in dielectric and thermal properties of the uniaxial ferroelectric triglycine sulphate (TGS) crystal, where T_C is the critical temperature of the paraelectric-ferroelectric phase transition. The new properties can be still observed even after the transverse field has ceased to be applied as long as the temperature of the sample does not exceed T_A. However, annealing the sample above T_C leads to the restoration of the original state of the crystal. An electric current flowing along the direction perpendicular to the polar axis of the uniaxial TGS ferroelectric crystal was measured below the temperature T_A at which the prolonged transverse electric field had been formerly applied to the crystal for a few hours. The experimental data resemble the classic pyroelectric current flowing along the polar axis.     

用杂化CIS-DFT方法研究外电场对乙烯激发态的影响

采用杂化CIS-DFT方法研究了外电场对乙烯分子基态和激发态性质的影响,结果表明外电场对分子几何结构,总能量,偶极矩,极化率,振子强度和激发能有显著影响.CIS-DFT的优点在于能确定外场下分子的对称性,给出正确的激发顺序以及分子轨道的电子组态,由此导出乙烯分子的激发态,结果与实验一致.首次研究了乙烯分子的外电场效应.与其他从头算方法相比,杂化CIS-DFT方法计算精确和效率相对较高,可用于研究大分子体系.     

Change in the IR spectra of polar liquids in an electric field

The IR absorption spectra of thin nitrobenzene, ethylene glycol, and glycerin layers in an electric field are investigated. It was established that the spectrum change and electro-optical effects depend on the molecular structure of these liquids. Grodno State University, 22, Ozheshko St., Grodno, 230023, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 441–444, May–June, 1998.     

Pu2分子激发态的外场效应

在相对论有效原子实势近似下,用B3LYP密度泛函方法计算优化得到了分子轴方向不同电偶极场（-0.002～0.002a.u.）作用下,Pu2的基态 ( )几何结构、电偶极矩和分子总能量.在优化构型下,用同样的基组采用含时密度泛函(TDDFT)方法(TD-B3LYP),研究了同样外电场条件下,对Pu2的激发能和振子强度的影响.计算结果表明,在外场作用下,对Pu2的前5个激发态电子跃迁光谱属于可见-红外光谱,波长为642.49～943.77nm,这是钚原子的奇异特征;激发能与外电场的关系近似满足Grozema等人提出的关系;电场对振子强度的影响比较复杂,但仍满足跃迁选择定则.     

Pu2分子激发态的外场效应

在相对论有效原子实势近似下,用B3LYP密度泛函方法计算优化得到了分子轴方向不同电偶极场（-0.002～0.002a.u.）作用下,Pu2的基态 ( )几何结构、电偶极矩和分子总能量.在优化构型下,用同样的基组采用含时密度泛函(TDDFT)方法(TD-B3LYP),研究了同样外电场条件下,对Pu2的激发能和振子强度的影响.计算结果表明,在外场作用下,对Pu2的前5个激发态电子跃迁光谱属于可见-红外光谱,波长为642.49～943.77nm,这是钚原子的奇异特征;激发能与外电场的关系近似满足Grozema等人提出的关系;电场对振子强度的影响比较复杂,但仍满足跃迁选择定则.     

Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30°C are studied to show the possible existence of double relaxation times τ ₂ and τ ₁ for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters γ and δ are obtained from X _ij ^′ /X _0ij and X _ij ^″ /X _0ij and w _j →0 where X _ij ^′ and X _ij ^″ are real and imaginary parts of the complex orientational susceptibility X _i ^* and X _0ij is the low frequency susceptibility which is real. X _ij ’s are involved with the measured dielectric relative permittivities ε _ij ^′ , ε _in ^″ , ε _0ij and ε _∞ij of solutions. The theoretical weighted contributions c ₁ and c ₂ towards dielectric dispersions by Fröhlich’s method are compared with the experimental ones obtained from the graphical variation of X _ij ^′ /X _0ij and X _ij ^″ /X _0ij with weight fractions w _j ’s at w _j → 0. The measured dipole moments μ ₂ and μ ₁ of the whole and the flexible part of a polar molecule in terms of the linear coefficients β’s of X _ij ^′ ’s with w _j ’s and the estimated τ ₂ and τ ₁ reveal their associations with aliphatic solvents. The theoretical dipole moments μ _theo’s from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated μ’s suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.     

Relaxation phenomena of polar non-polar liquid mixtures under low and high frequency electric field

Simultaneous calculation of the dipole moment μ_j and the relaxation time τ_j of a certain number of non-spherical rigid aliphatic polar liquid molecules (j) in non-polar solvents (i) under 9.8 GHz electric field is possible from real ε′_ij and imaginary ε″_ij parts of the complex relative permittivity ε*_ij. The low frequency and infinite frequency permittivities ε_0ij and ε_∞ij measured by Purohitet al [1,2] and Srivastava and Srivastava [3] at 25, 35 and 30°C respectively are used to obtain static μ_s. The ratio of the individual slopes of imaginary σ″_ij and real σ′_ij parts of high frequency (hf) complex conductivity σ*_ij with weight fractionsw _jatw _j → 0 and the slopes of σ″_ij— σ′_ij curves for differentw _js [4] are employed to obtain τ_js. The former method is better in comparison to the existing one as it eliminates polar-polar interaction. The hf μ_js in Coulomb metre (C m) when compared with static and reported μs indicate that μ_s s favour the monomer formations which combine to form dimers in the hf electric field. The comparison among μs shows that a part of the molecule is rotating under X-band electric field [5]. The theoretical μ_theos from available bond angles and bond moments of the substituent polar groups attached to the parent molecules differ from the measured μ_js and μs to establish the possible existence of mesomeric, inductive and electromeric effects in polar liquid molecules.     

均匀磁场中电子运动轨道的剖析

对于带电粒子在均匀磁场中的运动,流行的教科书只给出系统的能级和波函数,本对其运动轨道的细节加以分析,并给出其直观的物理图象。     

Polarization control over electric and magnetic dipole resonances of dielectric nanoparticles on metallic films

We reveal unusually strong polarization sensitivity of electric and magnetic dipole resonances of high‐index dielectric nanoparticles placed on a metallic film. By employing dark‐field spectroscopy, we observe the polarization‐controlled transformation from high‐Q magnetic‐dipole scattering to broadband suppression of scattering associated with the electric dipole mode, and show numerically that it is accompanied by a strong enhancement of the respective fields by the nanoparticle. Our experimental data for silicon nanospheres are in an excellent agreement with both analytical calculations based on Green's function approach and the full‐wave numerical simulations. Our findings further substantiate dielectric nanoparticles as strong candidates for many applications in enhanced sensing, spectroscopy and nonlinear processes at the nanoscale.

     

电偶极子位于均匀介质球中时球外电场的研究

采用分离变量法求解了电偶极子位于均匀介质球中时复连通域的拉普拉斯方程和泊松方程,求出了球内外两种不同介质的电势分布和球面上的极化电荷分布;通过求解二阶非线性微分方程得到了球外的电场线函数;利用计算软件Math-ematica 5.0,作出了相应的相互正交的等势线簇图形和电场线簇图形,并且进行了必要的讨论.     

高能等离子体入射对磁场膨胀影响的模拟研究（已撤稿）

采用三维模型，使用混合网格质点法对等离子体入射偶极子磁场产生的磁场膨胀进行数值模拟.在模拟中考虑了高能等离子体注入两种不同类型磁场的情况：等离子体注入没有背景磁场的偶极子磁场和等离子体注入有背景磁场的偶极子磁场.研究表明背景磁场的存在不仅改变了粒子的分布，还改变了磁场膨胀的程度.还研究了注入的高能等离子体的速度对磁场膨胀的影响，结果表明入射的高能等离子体速度越大，磁场膨胀的程度就越大.对于低的入射速度，入射粒子在偶极子磁场中的回旋半径与偶极子磁场的特征长度相比较小，粒子被磁场束缚，对偶极子磁场的影响可以忽 关键词： 网格质点法 磁场膨胀 偶极子磁场     

Phase velocity of a transverse electric wave propagating in a magnetized electron beam

In this paper three-dimentional simulations are carried out to the phase velocity of a transverse electric wave which propagates in a relativistic electron beam magnetized by a wiggler field and an axial guide magnetic field. Results show that the phase velocities are quite different from each other as the axial guide magnetic field changes its direction.     

Self-force on an electric dipole in the spacetime of a cosmic string

We calculate the electrostatic self-force on an electric dipole in the spacetime generated by a static, thin, infinite and straight cosmic string. The electric dipole is held fixed in different configurations, namely, parallel, perpendicular to the cosmic string and oriented along the azimuthal direction around this topological defect, which is stretched along the z$z$ axis. We show that the self-force is equivalent to an interaction of the electric dipole with an effective dipole moment which depends on the linear mass density of the cosmic string and on the configuration. The plots of the self-forces as functions of the parameter which determines the angular deficit of the cosmic string are shown for those different configurations.     

Anisotropic temperature of charged particles in a variable electric field

The time dependence of the longitudinal and transverse temperatures in a completely ionized plasma immersed in a variable uniform electric field is analyzed by solving gas dynamics equations based on a bi-Maxwellian distribution. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 64–72, December, 2008.     

Role of stochastic heating in wakefield acceleration monitored by optical injection

It is shown that stochastic heating can play an important role in Laser Wake Field Acceleration. When considering low density plasma interacting with a high intensity wave perturbed by a low intensity counterpropagating wave, stochastic heating can provide electrons with the right momentum for trapping in the wake field. The influence of stochastic acceleration on the trapping of electrons is compared to the one of cold injection by considering several polarizations of the colliding pulses. For some value of the plasma density and pulse duration, a transition from an injection due to stochastic acceleration to a cold injection dominated regime – regarding the trapped charge – has been observed from PIC code simulations. When the plasma density exceeds some value, stochastic heating becomes important and is necessary in some circumstances to get electrons trapped into the wakefield.     

Nonlinear Characteristics of an Intense Laser Pulse Propagating in Partially Stripped Plasmas

The nonlinear optic characteristics of an intense laser pulse propagating in partially stripped plasmas are investigated analytically. The phase and group velocity of the laser pulse propagation as well as the three general expressions governing the nonlinear optic behavior, based on the photon number conservation, are obtained by considering the partially stripped plasma as a nonlinear optic medium. The numerical result shows that the presence of the bound electrons in partially stripped plasma can significantly change the propagating property of the intense laser pulse.     

互易定理计算分层半空间上方任意取向偶极子的远区场

利用互易定理推导了考虑直达波和界面反射波时半空间分层界面上任意取向偶极子在上半空间远区辐射场的解析表达式. 进一步考虑电偶极子距离分界面为某一高度情形, 在考虑直达波和反射波程差基础上导出相应辐射场公式. 辐射场解析表达式中分层半空间TM和TE波反射系数可以通过连分数方法或传播矩阵法计算获得. 本文推导过程物理概念清晰, 所得解析结果适于计算观察点远离界面情形下偶极子的远区辐射场. 数值计算结果表明, 利用本文结果可以快速分析半空间上方任意取向偶极子的远区辐射场.     

铁电半导体耦合光伏器件的历史与最新进展

本文介绍了新型铁电-半导体耦合光伏器件的发展历史和现状, 阐述了所观察到的非经典行为, 即开路电压在直流偏置电场控制下的迟滞的现象. 将之与含有光诱导偶极子场的有机光伏器件和量子点电池、压电光电子器件、铁电光伏器件、钙钛矿电池等进行比较, 发现偶极子极化电场在多种光伏器件中均存在, 甚至可能起到主导作用. 因此, 提出了偶极子场半导体器件的概念, 期望从更广义的范围涵盖结场型器件和非结场型偶极子器件, 为促进光伏发电领域更多的创新提供思路.     

真空盒对二极铁场均匀性影响的研究

通过计算机模拟计算与实验相结合, 讨论了真空盒磁导率对二极磁铁磁场分布的影响. 结果表明当真空盒磁导率μ_r≠1时, 真空盒将影响磁铁磁场分布, 在磁场均匀性要求很高时, 必须考虑真空盒的材料与尺寸对磁场均匀性的影响.