放射性次级束流分离器的分离性能北大核心CSCD

放射性次级束流分离器(HFRS)是强流重离子加速器装置(HIAF)上开展放射性次级物理研究的重要装置。HFRS是飞行时间型(PF)碎片分离器,具有大磁刚度、大接受度、大孔径磁铁以及高动量分辨的特点。HFRS采用Bρ-ΔE-Bρ方法纯化弹核碎裂或裂变反应产生的放射性核素,是开展高精度储存环内实验及环外实验研究的重要工具。主要介绍HFRS分离纯化奇异核的能力,采用MOCADI程序模拟单降能器与双降能器下典型弹核碎裂反应和裂变反应中粒子的鉴别和纯化。模拟结果表明:HFRS具有很好的消色散和聚焦特性,对于弹核碎裂反应中轻核的分离采用单降能器系统即可得到很好的纯化效果;而弹核碎裂反应中重核的分离则需采用双降能器系统才可得到很好的纯化效果;对于裂变反应,由于裂变反应的能散较大,则在采用双降能器系统时也仅仅能得到一定的纯化效果。     

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.     

浅谈小学作文的现状和出路

本文从实际出发,探讨小学语文教学中的最大难点——作文,分析当前的现状,同时积极探求其出路,并在问题的阐述中着力突现以学生长期发展为本的教育理念,注重自主性学习和技能指导的可操作性。     

二手房交易价格鉴证工作的体会与对策

随着我国房地产市场的不断发展，房地产交易的范围变得越来越大。伴随着我国住房结构的变化，住房交易市场也越来越完善。完善的住房市场，包括新房市场和旧房市场，还包括出售市场和出租市场。随着住房市场的逐步完善，二手房交易将会越来越活跃。主要分析了二手房交易价格鉴证工作的体会与对策，以供同专业的人员参考。     

SHER-HIAF ring lattice design

The Super Heavy Experimental Ring （SHER）, which is one of the rings of the next accelerator complex High Intensity Heavy Ion Accelerator Facility （HIAF） at IMP, has to be optimized for e-cooling. Its lattice is designed for two modes： the first is the isochronous mode, which is a time-of-flight mass spectrometer for short-lived secondary nuclei, the second is the storage ring mode, which is used for collecting and cooling the secondary rare isotope beams from the transport line. In order to fulfil its purpose, the ion optics can be set to different ion optical modes.     

Bunch compression study using the envelope model in CSRm

The feasibility of attaining a short-pulse-duration heavy ion beam with a nanosecond pulse length is studied in the main ring of the Heavy Ion Research Facility in Lanzhou (HIRFL). Such a heavy ion beam can be produced by non-adiabatic compression, and it is implemented by fast rotation in the longitudinal phase space. In this paper, the possible beam parameters during longitudinal bunch compression are studied by using the envelope model. The result shows that a shortest heavy ion bunch ²³⁸U²⁸⁺ of 29 ns with energy of 200 MeV/u can be obtained, which can satisfy high energy density physics research.     

Commissioning of electron cooling in CSRe

The 400 MeV/u 12C6＋ ion beam was successfully cooled by the intensive electron beam near 1 A in CSRe.The momentum cooling time was estimated near 15 s.The cooling force was measured in the cases of difierent electron beam profiles,and the difierent angles between the ion beam and electron beam.The lifetime of the ion beam in CSRe was over 80 h.The dispersion in the cooling section was confirmed as positive close to zero.The beam sizes before cooling and after cooling were measured by the moving screen.The beam diameter after cooling was about 1 mm.The bunch length was measured with the help of the signals from the beam position monitor.The difiusion was studied in the absence of the electron beam.     

钢质波纹管空心楼板施工技术

钢质波纹管现浇空心楼板是一种非抽芯式空心楼板,由于该波纹管壁薄质轻,在混凝土浇筑过程容易发生上浮及位移,施工过程中通过采取固定措施,从而保证混凝土浇筑的顺利进行。     

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.     

冷却储存环CSRm中螺线管场耦合效应研究

介绍了重离子冷却储存环中螺线管场对束流水平方向和垂直方向产生耦合的原理, 由耦合运动方程及耦合系数推导出螺线管场耦合的补偿方法. 结合兰州冷却环主环实际的单元结构,工作点选在束流稳定的差共振附近, 模拟计算了冷却环主环在电子冷却段没有螺线管、有螺线管和增加补偿螺线管三种情况下的束流发射度及此三种情况下冷却环主环的动力学孔径. 通过模拟计算可知螺线管的存在将引起束流的水平方向和垂直方向严重耦合, 由于耦合效应, 垂直方向的发射度将超出其接受度, 致使束流大量损失. 针对这种情况, 提出了在螺线管两端的合适位置增加一组补偿螺线管的校正方案. 模拟结果表明这种措施行之有效.