CSRm变谐波加速

在研究兰州重离子冷却储存环(HIRFL-CSR)纵向相振荡运动特性的基础上,对主环(CSRm)内重离子的加速过程进行了模拟研究。选取由扇聚焦回旋加速器（SFC）剥离注入的能量为7 MeV/u,动量散度为±0.5%的12C6+典型离子,模拟了CSRm内束流的加速过程,加速的最终能量为1 GeV/u。在加速过程中采用了变换谐波的方式,解决了较低能量下的加速问题。模拟结果给出了不同时刻粒子在纵向相空间的分布以及各主要高频参数随时间的变化曲线。     

CSRm纵向束流绝热俘获研究

在研究重离子储存环纵向相振荡运动特性的基础上,对CSR主环CSRm内重离子的绝热俘获及加速过程进行了模拟,得出与CSR机器特性相适应的高频参数,并给出了高频参数在绝热俘获过程中随时间的变化曲线     

CSRe减速模拟

对兰州重离子加速器冷却储存环实验环中束流的减速过程进行了模拟研究,采用变换谐波的方式将粒子减速到较低能量,以适应高精度原子物理实验的需要.根据模拟结果得到了减速过程各个时刻粒子在纵向相空间分布,并给出了高频参数在减速过程中的变化曲线.     

HIAF-CRing 中的俘获加速效率研究(英文)

以HIAF-CRing上典型离子238U34+为研究对象,对其纵向俘获和加速的动力学过程进行了研究。累积后的粒子能量为800 MeV/u, 经过绝热俘获和加速后,粒子被加速至1 130 MeV/u。研究结果表明,通过选择适当的俘获时间、绝热参数以及相空间面积因子等参数,应用优化后的高频俘获加速曲线,可以获得更高的俘获和加速效率。通过粒子纵向动力学追踪软件ESME 上进行模拟,得到了优化后的高频相位、高频电压曲线,使得俘获效率达到99.3%,加速效率近乎100%。同时确定出了CRing 高频腔加速U34+ 所需满足的特性参数,即电压需达到40 kV,频率范围是0:31s0:34 MHz。To reduce the beam loss during the capture and acceleration processes of CRing in HIAF project, the longitudinal beam motion is investigated using the typical ion of 238U34+during the two processes mentioned above. The ions will be captured adiabatically firstly and then will be accelerated from 800 to 1130 MeV/u with a high efficiency using optimized RF voltage and RF phase program. After that the bunched beam will be debunched for the later beam compression. Simulation of these processes by tracking appropriate distributions with the longitudinal beam dynamics code ESME has been used tofind optimum parameters such as RF phase, RF voltage. The variation of the parameter during the RF cycle and the character parameters of the RF cavity are presented.      

变加速直线运动黑洞的量子热效应

给出了作变加速直线运动的蒸发黑洞的辐射温度。此温度不仅随时间变化,而且在视界的同时面上不是常数。这种黑洞的视界位置随时间变化,而且形状不是球对称的。 关键词：     

激光加速电子束团的输出特性研究

通过仔细研究俘获加速CAS(captureandaccelerationscenario)机制中电子束团的输出特性,发现其出射电子有3类不同的运动轨道即掠过(pass-by)、非弹性散射(IS)、CAS.由于实际入射电子束团的线度远大于强激光脉冲的线度,因此只有位于入射电子束团中心区域的电子才可能被俘获加速.对于目前所能获得的聚焦激光场强(～10²¹W/cm²)和实际的电子束团(～10⁸个电子)而言,最大的输出能量可达到450MeV以上,同时被加速电子的数目可达到10⁴—10⁵个.这表明CAS可望发展成为小型台式加速器的新加速原理     

用Excel软件拟合求解变加速直线运动问题

结合一道考试题的命制及求解,运用Exce软件,拟合求解变加速直线运动,得到了结果并绘制出v-t和a-t的图像.     

变梯度倾斜场加速管的简化场型公式

本文导出了中心粒子轨迹具有“零进、零出”约束条件的变梯变倾斜场加速管工艺段的简化场型公式。     

从一道习题看电磁感应中变加速直线运动的数据制约关系

在有关"电磁感应"教学内容中,很多习题涉及到变加速直线运动,它能很好地培养学生的综合能力.本文以一道热门试题为例,探讨合外力、加速度、速度、位移等各物理量的数据之间相互制约关系.     

变加速动力学与舒适性问题

用变加速动力学的急动度(加加速度)概念,分析了车辆、电梯的乘座舒适性与高层钢结构建筑的风振舒适性问题.     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.     

Longitudinal RF capture and acceleration simulation in CSNS RCS

China Spallation Neutron Source (CSNS) is a high power proton accelerator-based facility. Uncontrolled beam loss is a major concern in designing the CSNS to control the radioactivation level. For the Rapid Cycling Synchrotron (RCS) of the CSNS, the repetition frequency is too high for the longitudinal motion to be fully adiabatic. Significant beam loss happens during the RF capture and initial acceleration of the injection period. To reduce the longitudinal beam loss, beam chopping and momentum offset painting methods are used in the RCS injection. This paper presents detailed studies on the longitudinal motion in the RCS by using the ORBIT simulations, which include different beam chopping factors, momentum offsets and RF voltage optimization. With a trade-off between the longitudinal beam loss and transverse incoherent tune shift that will also result in beam losses, optimized longitudinal painting schemes are obtained.     

Oscillation properties of matter-wave bright solitons in harmonic potentials

We investigate the oscillation periods of bright soliton pair or vector bright soliton pair in harmonic potentials. We demonstrate that periods of low-speed solitons are greatly affected by the position shift during their collisions. The modified oscillation periods are described by defining a characterized speed, with the aid of asymptotic analysis on related exact analytic soliton solutions in integrable cases. The oscillation period can be used to distinguish the inter- and intra-species interactions between solitons. However, a bright soliton cannot oscillate in a harmonic trap, when it is coupled with a dark soliton (without any trapping potentials). Interestingly, it can oscillate in an anti-harmonic potential, and the oscillation behavior is explained by a quasi-particle theory. The modified period of two dark-bright solitons can be also described well by the characterized speed. These results address well the effects of position shift during soliton collision, which provides an important supplement for previous studies without considering phase shift effects.     

DLA光源质量对光栅-外腔谱合成系统光束质量的影响

在二极管激光阵列(DLA)光栅-外腔谱合成系统中,由于DLA存在子单元光束发散角、“smile”效应的位置偏差及指向性偏差等因素的综合作用,将导致合成光束的光束质量降低。综合考虑DLA子单元光束发散角、“smile”效应等因素对谱合成系统中光束传输特性的影响,建立了DLA光栅-外腔谱合成系统的光传输模型,进而对谱合成系统中DLA子单元光束发散角、“smile”效应的位置偏差及指向性偏差等因素对合成光束的光束质量影响进行了定量分析。结果表明,DLA光源质量会明显影响合成光束的光束质量：DLA子单元光束发散角和“smile”效应引入的指向性偏差越大,合成光束的光束质量就越差;“smile”效应引入的位置偏差在合束方向上对合成光束的光束质量没有影响,而在非合束方向上引入的位置偏差将会明显降低合成光束的光束质量。在实际工作应用中,需要采取措施提高DLA光源质量,以减小对合成光束的光束质量影响。     

二维各向同性变频率谐振子的超对称性及其不变量的超对称量子力学精确解

采用超对称量子力学与不变量相结合的方法讨论了二维各向同性变频率谐振子,给出了二维各向同性变频率谐振子的不变量,采用超对称量子力学方法精确求解了不变量的本征值和本征函数,并且给出了当频率恒定时,二维常频率谐振子的本征值和本征函数的精确解.最后对不变量的超对称性进行了讨论.     

Second harmonic magnetoacoustic responses of magnetic nanoparticles in magnetoacoustic tomography with magnetic induction

Due to the unique magnetic, mechanical and thermal properties, magnetic nanoparticles(MNPs) have comprehensive applications as the contrast and therapeutic agents in biomedical imaging and magnetic hyperthermia. The linear and nonlinear magnetoacoustic responses determined by the magnetic properties of MNPs have attracted more and more attention in biomedical engineering. By considering the relaxation time of MNPs, we derive the formulae of second harmonic magnetoacoustic responses(2H-MARs) for a cylindrical MNP solution model based on the mechanical oscillations of MNPs in magnetoacoustic tomography with magnetic induction(MAT-MI). It is proved that only the second harmonic magnetoacoustic oscillations can be generated by MNPs under an alternating magnetic excitation. The acoustic pressure of the 2H-MAR is proportional to the square of the magnetic field intensity and exhibits a linear increase with the concentration of MNPs. Numerical simulations of the 2H-MAR are confirmed by the experimental measurements for various magnetic field intensities and solution concentrations using a laser vibrometer. The favorable results demonstrate the feasibility of the harmonic measurements without the fundamental interference of the electromagnetic excitation, and suggest a new harmonic imaging strategy of MAT-MI for MNPs with enhanced spatial resolution and improved signal-to-noise ratio in biomedical applications.     

Second harmonic generation in layered TunS2 in the vicinity of the low-temperature phase transitions

Second-harmonic generation in the ternary layered semiconductor TlInS₂ excited with the wavelength λ = 1.06 μm of YAG: Nd^{3 +} laser is investigated in the temperature range corresponding to the low-temperature phase transitions. It is shown that the intensity of the second-harmonic signal corresponding to the non-linear coefficients d_eff, d₂₁, d₂₂ reveals peculiarities close to the commensurate-incommensurate phase transitions. The temperature hysteresis of the second-harmonic signal in the low-temperature region (below and close to T_i2 = 206K) is explained assuming that an incomplete lock-in transition in TlInS₂ takes place at T_c1 =204K within the temperature range between a ferroelectric (T_c2 = 201K) and an incommensurate (T_i2 = 206 K) phases. It is shown that the monoclinic point group symmetry C₂ is preserved also at temperatures lower than the phase transition temperature Tc4 = 79K to a weak ferroelectric state.