大型FFAG磁铁的2维POISSON设计

 为减小边缘场效应，大型固定磁场交变梯度（FFAG）磁铁的磁场分布由修整线圈和磁极形状两者共同来实现。通过2维POISSON模拟计算，确定了修整线圈电流和位置的分布以及磁极形状, 得到了局域磁场梯度指数与设计值之间的最大差异只有0.5％的磁场分布。为提高POISSON模拟计算的效率，POISSON输入文件中有关线圈电流和位置、磁极形状的输入和调整由程序自动完成。     

THE POWER SPECTRUM OF THE MASS IN A SANDPILE MODEL WITH STOCHASTIC SLIDE

The power spectrum of the mass in a theoretical sandpile model with stochastic slide is examined. The simulations show that the power spectrum has the form of l/f^α, and the exponent α may vary with the average time interval between the successive events af the sands flowing off the sandpile. The conditions of generating 1/f noise are also discussed.     

混凝土构件长期干缩应力的计算

本文用有限元法从砼的水分扩散方程中求出湿度和自由干缩应变场,分别由砼的线性和非线性蠕变理论及拉应变软化模型,推导出计算砼构件的干缩应力的递推公式,并编制了电算程序。计算表明,非线性理论的结果与线性理论的结果相差不大,而拉应变软化模型的结果与前两者有较大差异。     

Status of CSNS H- ion source

A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source (CSNS). In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.     

基于大涡模拟下风力机翼型非定常转捩流动的动态模态分解分析

翼型绕翼流动对风力机整机性能产生重要影响.本文基于大涡模拟方法,得到风力机翼型非定常转捩流动.通过对压力流场的动态模态分解(DMD)分析,发现翼型层流分离泡的生成和发展为流动主要非定常特征,且该特征具有主要频率.预估得到高增长率T-S扰动波频率与DMD模态频率接近,发现高频变化的分离泡由边界层分离点下游不远处的T-S扰动波诱导K-H不稳定性而主导,以及中低频的DMD模态表现为T-S扰动波所引起的湍流结构.对比不同攻角下的DMD分解结果,发现上表面分离泡会逐渐向前移动,长度变短;而下表面分离泡略微后移,长度变化不大.     

复合材料力学的Hamilton体系和辛几何方法(Ⅲ)——弯曲问题和板的振动*

把本文第一部分建立的方法用于求解各向异性板的弯曲问题和振动问题.     

RF power coupling for the CSNS DTL

The China Spallation Neutron Source (CSNS) drift tube linac (DTL) consists of four tanks and each tank is fed by a 2.5 MW klystron. Accurate predication of RF coupling between the RF cavity and ports is very important for DTL RF coupler design. An iris-type coupler is chosen to couple the RF power to the DTL accelerating cavity. The physical design of the DTL coupler and the calculations of RF coupling between the cavity and coupler are carried out. The results from the numerical simulations are in excellent agreement with the analytical results.     

用于散裂中子源直线加速器超导段相速度设计分析

对用于散裂中子源的质子直线加速器的超导加速段进行了初步设计,其中,包括加速腔腔形的设计和优化、超导加速段的结构布局.另外,对超导加速腔的加速单元数的选择及设计值β_G的确定、加速腔的优化原则及束流的动力学性质进行了讨论.     

强流AVF型Hui旋加速器中的空间电荷效应和束晕

详细推导了AVF型Hui旋加速器中束团粒子在曲线坐标系中的动力学方程（考虑和不考虑空间电荷相互作用力两种情况）,在假定动力学方程中各参值的前提条件下,用Lunge-Kutta方法对考虑空间电荷时的动力学方程进行了数值计算,结果表明,束晕的形成和发展同样也是强流Hui旋加速器中束流损失的一个主要原因,但束晕形成的机制不同于直线加速器的情况,它不是由共振和混沌引起,而是由于粒子的排斥运动和束团内粒子的涡流运动引起的。