一种K500超导迴旋加速器垫补线圈功率消耗的优化方法

在K500超导迴旋加速器原先设计中并未考虑垫补线圈功率消耗的优化问题。此文提出了一种带限制条件的最小二乘法来重新分配大小主线圈中电流比例以达到优化目的。采用优化法与未采用的Bellomo计算相比较,结果是令人满意的。     

The Cyclotron Waves in Layered Conductors

We have studied theoretically the propagation of electromagnetic waves in layered conductors placed in a strong magnetic field B ₀. It is shown that the wave process is very sensitive to the orientation of B ₀ with respect to the layers. The weakly damping modes with the frequencies near the cyclotron resonance frequency can propagate at orientations of the magnetic field vector, for which the drift velocity of charge carriers along the B ₀-direction is close to zero. The cyclotron waves spectrum is analyzed with regard to the Fermi-liquid interaction of electrons.     

20～100 MeV紧凑型回旋加速器轴向注入系统实验台架的物理设计

建立 2 0～ 1 0 0MeV紧凑型回旋加速器轴向注入系统实验台架 ,用以进行提高回旋加速器的注入流强与效率的实验研究。在该实验台架的物理设计与元件设计中 ,主要考虑H- 束从离子源引出后传输到回旋加速器中心区的输运线元件选用、物理参数匹配计算、物理元件设计等问题。设计对象是2 2MeV和 70MeV回旋加速器的轴向注入系统 ,并将两者的布局、元件及几何尺寸、物理参数的选取统一 ,以便于实验台架的建立 ,从而形成适应性强的强流回旋加速器轴向注入系统。整个系统只需做少量调整就可满足能量为 2 0～ 1 0 0MeV的回旋加速器注入要求。     

18F-生产条件和影响因素初探

以TR19型回旋加速器为例，探讨了正电子核素18F的生产条件和影响因素。结果表明，靶18O-H2O的丰度、束流强度、轰击时间是影响18F产额的主要因素，18O-H2O的丰度越高，18F产额越高；质子束流强度为10～35 µA时，18F产额随束流增加而增加；轰击时间为20～60 min时，18F产额随打靶时间增加而增加。此外，离子源和电磁场也应设置在一定的参数内，以提高18F产额，提高工作效率     

100MeV强流质子回旋加速器主真空室辐射剂量的数值研究

中国原子能科学研究院正在设计研究的100MeV强流质子回旋加速器中真空室内的残余气体和磁场中的洛仑兹剥离将导致部分负氢离子束流损失，并在真空室内产生辐射剂量。本工作采用蒙特卡罗方法模拟计算该加速器运行时真空室外壁上沿圆周方向的辐射剂量分布，计算得出其最大值约为143Sv/h。同时，研究了在加速器停机后真空室内部的剩余辐射剂量场分布及其随时间的衰减规律。      

One-Dimensional Vertical Electron Cyclotron Emission Imaging Diagnostic for HT-7 Tokamak

At the first stage of the electron cyclotron emission imaging （ECEI） diagnostic project on HT-7, a 16-channel vertical-resolved ECEI diagnostic has been developed and installed on HT-7 tokamak to measure electron cyclotron emission with a temporal resolution of 0.5 usec. The system works at a fixed frequency of 97.5 GHz. The sample volumes of the system are aligned vertically with a vertical channel spacing of 11 mm, and can be shifted across the plasma cross-section by varying the toroidal magnetic field. The high spatial resolution of the system is achieved by utilizing a low-cost linear mixer/receiver array and an optical imaging system. The focus location may be shifted horizontally when translating one of the optical imaging elements. The details of the system design and laboratory testing of the ECEI optics are presented together with the preliminary experimental results.     

The role of oxygen in electron cyclotron resonance etching of silicon carbide

The electron cyclotron resonance (ECR) etching of silicon carbide (SiC) was studied using SF₆ + O₂ based plasma. The role of O₂ was studied by varying the O₂ flow rate while keeping the total gas flow constant. It was found that oxygen enhances the etch rate at low O₂ fraction through releasing more fluorine atoms, while lowers the etch rate at high O₂ fraction by diluting fluorine atoms and forming an oxide-like layer. The etched surface roughness was found to be affected by the surface oxidation and oxygen ion related physical ion bombardment. The role of oxygen in chemical etching of carbon was found to be insignificant. In general, the etched surface is smooth and free of micromasking effect that can arise from Al contamination and C rich layer.     

100MeV强流质子回旋加速器主磁铁电磁力的数值模拟

本工作研究计算中国原子能科学研究院目前正在设计、建造中的100MeV强流质子回旋加速器CYCIAE-100主磁铁电磁力。计算中选用虚位移法和麦克斯韦应力张量法两种方法。在利用电磁场三维有限元分析程序计算得到紧凑型等时性回旋加速器主磁铁电磁场的基础上,先采用虚位移法估算电磁吸力,然后基于麦克斯韦应力张量法在MATLAB环境下编写数值计算程序,详细研究磁极和磁轭受到的电磁吸力。两种方法的计算结果接近。计算得到的主磁铁磁极间吸力大于磁极与盖板间吸力,二者之差由磁极和盖板间的螺栓承担。电磁力的计算结果为主磁铁结构变形计算和结构方案选取提供了依据。     

Preparation and preliminary evaluation of [^55Co]（II）vancomycin

Co-55 （t1/2=17.53 h） was produced by 150 uA irradiation of a natural nickel target using 15 MeV protons. It was separated from the irradiated target material by two ion exchange chromatography steps with a radiochemical yield of 〉95% and was used for the preparation of [^55Co]vancomycin （[^55Co]VAN）. Optimization studies were performed using Co-57 due to its longer half-life. Cobalt-57 （t1/2=271.79 d） was produced by irradiation of a natural nickel target with 150 pA current of 22 MeV protons. The 57Co was separated from the irradiated target material using a no-carrier-added method with a radiochemical yield of 〉97%. Both products were controlled for radionuclide and chemical purity. The solutions of [^55Co]VAN were prepared （radiochemical yield〉80%） starting with 55Co acetate and vancomycin at room temperature after 30 min. A precise solid phrase extraction （SPE） method was developed using Si Sep-Pak in order to purify/reconstitute the final formulation for animal studies. [^55Co]VAN showed a radiochemical purity of more than 99%. The resultant specific activity was about 1.15 TBq/mmol. It is proved that the tracer is stable in the final product and in presence of human serum at 37℃ up to 24 h. Biodistribution study of [55Co]VAN in normal rats was undertaken for up to 72 h.     

ECR等离子体对硅表面的低温大面积氮化

利用电子回旋共振微波放电氮等离子体对单晶硅表面进行了低温大面积氮化的探索 ,通过样品表征和等离子体成分探测 ,分析讨论了氮化机理。结果表明 ,这种方法可以用于硅表面的低温氮化处理 ,获得大面积的均匀氮化硅表层。