20kV射频堆积腔的物理设计

分析了重离子束的射频堆积过程。在此基础上,根据兰州重离子加速器冷却储存环（HIRFL-CSR）内束流流强为10     

基于腔式探头的束团到达时间测量算法优化

腔式探头具有高信噪比和高灵敏度的特性,TM010模式下在近轴附近的腔体输出信号与束流横向位置无关,信号幅度与电荷量呈正比,信号相位由束团到达时间决定,因此非常适用于高分辨率的束团到达时间测量。上海硬X射线自由电子激光装置（SHINE）对束团到达时间的测量精度要求非常高,期望运用基于谐振腔的束团到达时间监测系统,可实现在100 pC电荷量下分辨率好于25 fs的技术指标。对于高Q的谐振腔信号,单点采样的信噪比随信号的衰减而降低,因此肯定存在一最佳的信号处理窗口。为分析最佳处理窗口与相关参数的定量关系,采用数值仿真和束流实验相结合的办法来研究这个问题。分析发现,存在最佳数据处理时间窗口,该参数只与信号衰减时间常数有关,而与系统采样率、系统信噪比、系统模拟带宽无关。在最佳数据处理时间窗口条件下,束流到达时间测量不确定性可获得最佳值。     

Development of synchrotron control for Heavy-Ion Medical Accelerators

The power supplies for the main bending and quadrupole magnets of the Heavy-Ion Medical Accelerator (HIMAC) in Chiba are controlled by preset current and voltage patterns, which are created by a pattern-creation program. It has been observed that a deviation between the preset current and the actual one becomes very large when newly created patterns are applied to the power supplies. This deviation is attributed to the incorrect parameters used for calculations of the voltage pattern in the pattern-creation program. In order to reduce the deviation, we have analyzed the values of resistance and inductance using the actual data of the current and voltage patterns. As a result, more than 10% difference was found between the conventional and newly calculated parameters. By applying the new parameters to the pattern-creation program a reduction of the deviation was confirmed.     

Impact of Accelerators on Technology

Accelerators and accelerator technology has rapidly expanded into Medicine and Industry. The 2500 accelerators in the USA, which represent about 2/3 the worldwide census of accelerators are primarily devoted to practical applications, although the major impact on technology has been produced by a relatively few excellent facilities. Approximately 80% of the current accelerators in the USA are found to be in medical and industrial use representing a capital investment by industry of $200,000,000. Of greater importance is their impact on the treatment of cancer, and the improvement or creation of better products for industrial and consumer use. The development of new accelerators and techniques are required in order to insure continuing benefits to the public.     

Some Medical Applications of Accelerators

The present uses of accelerators in nuclear medicine and radiation therapy are summarized. Attention is called to the widespread use of these devices for production of radioisotopes for diagnostic purposes and of x rays for treatment of cancer. Developments presently underway to make use of high energy heavy nuclear particles for both isotope production and therapy are discussed and an overview is presented of one of a new family of accelerators nearing completion. In view of the large fraction of the total population who stand to benefit from better diagnostic and therapy modalities, the question is posed whether more adequate resources should not be made available for improving diagnostic and therapeutic capabilities while minimizing radiation dose to the patient.     

Computer Control of High Energy Accelerators

The complexity of high energy accelerators has increased to the point where digital control techniques offer significant advantages. The basic techniques and equipment have been developed over the last ten years for use in chemical and steel plants. Some of these techniques can be usedin modified form on high energy accelerators. The amount of time required for analog-to-digital conversion and for computer input-output operations limits computers to supervisory type control. The relatively slow output rates from the computer, in combination with the precise timing requirements of the synchrotron, indicate that a special buffer is required between the computer and the synchrotron. This buffer should be able to store and execute the instructions necessary to adjust all variables (magnitude and time) that are under computer control. Present control computers are so well perfected that most of the development effort goes into suitable sensing equipment and into computer programs. Injector alignment, analysis of coasting beam, control of tune, and control of characteristics of the beam to each of several experiments are some of the functions that appear to be realizable.     

双层错位DOI脑PET探测器晶体厚度组合优化设计

双层错位晶体阵列是正电子发射断层成像（PET）仪获取作用深度（DOI）信息的一种低成本且简便的方案。为获得晶体厚度最优组合方案,本文使用GATE软件进行蒙特卡罗仿真研究。模拟兼容核磁共振成像（MRI）的嵌入式脑PET,环内径345 mm,使用硅酸钇镥（LYSO）晶体,2层晶体总厚度20 mm,内层晶体从0 mm到10 mm共11种厚度（间隔1 mm）;进行点源模拟实验,点源位于中心断层x轴上,偏移从x=0 cm到x=10 cm共6种情况（间隔2 cm）。计算中心点灵敏度;采用滤波反投影算法重建图像,评估径向空间分辨率。结果显示,双层晶体的设计相比于单层晶体灵敏度略有下降,但系统径向空间分辨率显著提高且其均匀性得到改善。随着内层晶体厚度的增大,视野平均径向空间分辨率先减小后增大,在内层晶体厚度为8 mm时达到最小。综上所述,所设计的双层错位DOI脑PET探测器晶体厚度最优组合方案为内层晶体厚度8 mm、外层晶体厚度12 mm。     

Optimization Design of Crystal Thickness Combination for Dual-layer-offset DOI Detector for Brain PET

Dual-layer-offset crystal array is a low cost and simple scheme for positron emission tomography (PET) system to achieve depth of interaction (DOI) information. Different thickness combinations of two layer crystals influence system performances. Monte Carlo simulations using GATE toolkit were implemented to optimize the design by evaluating the performances of the system with different thickness combinations in this study. Eleven magnetic resonance imaging (MRI) compatible brain PET inserted systems with an inner diameter of 345 mm, dual layer LYSO of 20 mm total thickness and inner layer thickness varied from 0 mm to 10 mm with a step size of 1 mm were built. Six point sources in the x-axis of the center slice from x=0 cm to x=10 cm with an interval of 2 cm were simulated. The sensitivity at the center was calculated and the radial resolutions were evaluated using the reconstructed points by the filtered back projection algorithm. The results show that dual-layer crystal design has a slight sensitivity decrease, but can significantly improve the radial spatial resolution and the resolution uniformity compared with the single-layer design. With the thickness increase of the inner crystal, the average radial spatial resolution decreases and then increases, and achieves minimal at inner layer with a thickness of 8 mm. In conclusion, 8 mm in the inner layer and 12 mm in the outer layer is the optimal design for the brain PET system with 20 mm dual-layer-offset crystal proposed in this study.     

The Future of High Energy Accelerators

This paper begins with a review of those high energy accelerators which are now in operation. Accelerators under construction are discussed and very high energy machines, still far in the future, are listed and described. Possible uses of cryogenic and superconducting magnets are mentioned. Colliding beam projects in operation and planned are presented. High energy physics has become very expensive. The total investment in Brookhaven's 33-GeV accelerator complex is now over $60 million and is still rising. Merely to operate the accelerator and its experimental areas requires the services of over 400 people. Our power bill is about $1 million per year. All of this is to produce new knowledge, very fundamental in nature but without evident immediate application. With the budget of the United States in a state of unbalance and with growing sentiment that money spent should show immediate results, is it wise or even sensible to think of new and more expensive steps along the route to the solution of the many mysteries of the nucleus and its components? I think that it is wise and that frontier fields like that of high energy physics must be pursued vigorously if we are to maintain our intellectual and technical position in the world. Sooner or later our experimental results will have important impacts on our life, probably in quite unforeseeable fashions. Nuclear physics began its history before the turn of the century; only in the last two decades has it resulted in a new power industry.     

粒子加速器的回顾与展望

在回顾 2 0世纪加速器能量提高和技术的发展的基础上 ,展望了粒子加速器向高能量前沿、高亮度前沿、实际应用以及新原理、新技术的发展。     

Simulation Analysis of Transmission-Line Impedance Transformers for Petawatt-Class Pulsed Power Accelerators

Based on the transmission line code TLCODE, a 1D circuit model for a transmission- line impedance transformer was developed and the simulation results were comp...     

Relevance of Plasma Science to Particle Accelerators

In following the theme of this Symposium, Plasma Science and Its Applications, we may be suggesting to some readers that the other applications of Plasma Science somehow justify the existence of a field traditionally devoted to fusion energy. In fact, we do not believe that plasma science can or should be justified for its spin-off contributions. Nevertheless, the unity of science would be seriously threatened by a precipitous decline in the support for plasma science. It is that unity which repeatedly has been verified as one looks for how advances in one field are crucial to several other seemingly fundamentally different fields. Thus it is in this case, as a representative of the community of Particle Accelerator Scientists, that we show four significant areas in which the methods and the results of plasma science have been applied to Accelerator Science. We have deliberately skipped plasma ion sources which are perhaps the most obvious application of plasmas to accelerators. Two of our four examples are cases in which the computational methods of plasma science have been adopted, and two are examples in which the plasmas themselves are employed. One of each category are now actively in use and the other one in each category is being used to develop or design new devices.     

不同加速剂对LiF高温水解反应的影响

主要研究了U_3O_8、WO_3和Cr_2O_3三种加速剂对LiF高温水解反应的影响,讨论了有无加速剂、加速剂种类、加速剂用量和反应时间等对LiF高温水解转化效率的影响。采用X射线衍射法(XRD)对LiF水解固态产物的组成进行了表征,结果发现,当水解温度为650℃时,三种加速剂对LiF水解反应的加速效果满足以下规律:WO_3U_3O_8Cr_2O_3。另外,还研究了LiF在三种加速剂存在下的水解产物,且推测出其相对应的反应机理,从而为这些加速剂的实际应用提供重要参考依据。