High Power Klystrons

This paper will review the evolution of high power klystrons and their applications in supplying rf energy for linear accelerators. Other types of possible rf sources were considered for SLAC, and the reasons for the selection of klystrons will be given. A brief review of klystron types in use for various accelerators will also be given, but the emphasis will be on the work done by Stanford and its subcontractors in developing klystrons capable of achieving peak powers in excess of 20 MW and average powers of 20 kW for use with the two-mile Stanford linear accelerator.     

Linear electron accelerators for industry and medicine

Linear accelerators are described together with accelerator systems based on them, which have been designed and produced in the linear-accelerator and cyclotron division at the D. V. Efremov Fundamental Electron Applications Research Institute. Brief information is given on future developments in resonant linear accelerators and systems based on them. D. V. Efremov Fundamental Electron Applications Research Institute. Translated from Atomnaya énergiya, Vol. 87, No. 2, pp. 145–151, August, 1999.     

Energy transmission by relativistic electron beams

The feasibility of energy transfer over long distances by high-energy electron beams propagating inside an autonomous, flexible vacuum ion duct, is examined. Since the electrons do not lose energy in the ion duct, itself, the energy transfer efficiency is determined by the efficiencies of a linear resonance electron accelerator at the energy source and of an accelerator-recovery system at the delivery site. Unfortunately, existing linear resonance accelerators do not have a sufficiently high efficiency. Thus, ways of raising the efficiency from the present level of 60–70% to the required ≥90% are discussed. If a high efficiency is achieved in the resonance electron accelerator, then it is possible to design high-power, efficient (≥95%) systems for transfer of energy over long distances, with efficiencies that are independent of the transmission distance or the energy flux. Translated from Atomnaya énergiya, Vol. 105, No. 4, pp. 225–232, October, 2008.     

Recent Advances in DC Methods of Particle Acceleration

Four recent developments have contributed significantly to broadening the scope of dc particle-acceleration systems: 1. Tandem principle of utilizing the generated high-voltage several times; 2. Insulating-core transformer for generating high-voltage dc power; 3. Inclined-field acceleration tube that minimizes the "total voltage effect, a previous limitation of dc acceleration systems; 4. Ion-source and beam-optical designs to increase useful ion intensities and to improve efficiency of transporting accelerated dc beams. These developments are currently being incorporated, in various combinations, into several dc accelerator designs, including: a. Sub-Mev electron and positive-ion accelerators with high beam power; b. Tandem Van de Graaff accelerators with at least 10 million-volt potential; c. Powerful Tandem accelerator at moderate voltage and very high current. Typical systems arising out of these advances are described in the light of applications now being exploited in research and industry.     

RADIATION HAZARD AND PROTECTION OF LOW ENERGY ACCELERATORS

In this paper,the origin and type of radiation hazards as well as the main aspects of radiation protection for low-energy accelerators are discussed in general,and the problems of radiation protection and the experimental results of the operational monitoring of the five accelecrators in the Institute of Nuclear Science and Technology,Sichuan University,namely,one 1.2M cyclofron,two Cockroft-waltons and two Van de Graafts,as well as a powerful electron accelerator for industrial irradiation are described.The discussion and evaluation are made according to the requirments of the national standards GB5172-85.     

聚束系统设计与计算程序

LMOVE程序是一个模拟粒子纵向运动的FORTRAN语言程序。它可以计算由三电极双间隙聚束器(或这种聚束器的组合)、单狭缝谐波聚束器、静电加速管和自由飘浮空间组成的束流脉冲化系统。程序采用大量粒子模拟束团在纵向相空间内的运动,并用Monte-Carlo方法随机产生相空间内各代表点的初始条件。因此,较为适合模拟粒子在配有聚束器件的静电加速器中的纵向运动。本程序不考虑粒子的空间电荷效应。     

Precipitation behavior of M23C6 carbides and its effect on mechanical properties of Ni-based Alloy 690

ABSTRACT

The effect of solution annealing and aging treatment on the intergranular carbide precipitation behavior of alloy 690 tubes for steam generators is investigated. The carbides precipitated on the grain boundaries were identified as chromium-rich M₂₃C₆ carbide, which has a cube-cube orientation relationship with the matrix on one side of neighboring grains. The carbide precipitation behavior is closely related to the interaction between the solubility of carbon in Ni-based matrix and diffusion of alloying elements. The ultimate tensile strength and elongation of the solution annealed alloy 690 tubes at 300°C are 638.8 ± 12.4 MPa and 43.2 ± 4.2%, respectively. In the early stage of precipitation, the ultimate tensile strength increased to 720.4 ± 13.5 MPa. The carbides function as reinforcement in alloy 690 and provide strength enhancement with aging time reached 15 hours. However, when the aging time passed 15 hours, this property gradually decreased to 710.6 ± 12.6 MPa due to the low bonding strength between the carbide and matrix.     

正弦波速调管聚束理论及其应用

以正弦波速调管聚束理论为基础。详尽阐述了速调管聚束的具体实现方法,给出了相应的计算公式。实际应用该法,为NS-200加速器设计了聚束装置。     

用于2 GeV固定场交变梯度质子加速器的高品质因数、高分路阻抗波导型高频腔设计

在核工业、民用及基础研究领域，高能强流质子加速器有着十分广泛而重要的应用，中国原子能科学研究院提出了1台2 GeV连续波固定场交变梯度质子加速器的解决方案。在该方案中，工作在44.4 MHz的大功率高品质因数、高分路阻抗波导型高频腔研制极其重要。本文首先对工作在44.4 MHz的矩形、欧米伽形、跑道形及船形等4种形状的波导型高频腔进行了模拟计算研究，经比较发现，船形高频腔具有最高的品质因数和分路阻抗，是2 GeV连续波固定场交变梯度质子加速器的较好选择。在此基础上，为掌握船形高频腔的实际加工工艺，同时利用现有230 MeV超导回旋加速器的功率源设备开展高功率实验研究，设计了71.26 MHz的缩比例船形高频腔样机。     

中国粒子加速器的发展现状和趋势

我国的粒子加速器近20年来发展迅速,在加速器不同的类型、规模和应用方向上全面向世界先进水平靠近。本文以几个主要加速器研究或应用方向如先进光源、强流质子-重离子加速器、粒子对撞机、民生应用型加速器为主线,介绍其中几台典型装置的建设和发展,以及它们在国际上的地位和在相应学科研究中所发挥的作用。同时,也介绍我国在加速器物理和技术方面的快速进步,这些进步不仅对已经建造和正在建造的大型加速器装置是个极为重要的支持,也是加速器学科的自身发展,并为未来更先进的加速器装置的发展提供了可能性。本文对我国未来若干年的加速器事业发展作了展望,期望我国的加速器在10年后将全面处于国际先进水平,同时也对我国在激光等离子体尾场加速领域近些年来的飞速发展作一个简单评述。     

Ion source brightness and nuclear microprobe applications

The ion source used to provide beams for nuclear microprobe systems must ideally satisfy several demands. Of primary importance is the beam brightness. It is clearly desirable to employ the brightest possible source in order to focus the smallest possible probe size on the specimen, with the highest possible beam current. Also important is the need for minimal maintenance, particularly for ion sources used inside single ended accelerators.

We report here on measurements conducted on the beam from the RF ion source in our 5U Pelletron accelerator. We have found that the beam brightness is highly heterogenous, with the paraxial rays about an order of magnitude brighter than the surrounding rays. This is desirable for nuclear microprobe operation because probe forming lens systems optimised for large demagnification magnitude can exploit the high brightness of the paraxial region. We find several other accelerators around the world also exhibit this characteristic.     

Properties of Electrodeposited Tungsten Coatings on Graphite Substrates for Plasma Facing Components

Tungsten coating on graphite substrate is considered as one of promising candidate materials of plasma facing components. In this study, tungsten coatings on graphite substrate were successfully prepared by direct current (DC) and pulse current (PC) electrodeposition methods in Na₂WO₄–WO₃ molten salt under the air atmosphere. Pores were found on the surfaces of the tungsten coatings produced by DC electrodeposition method. For the coatings fabricated by PC method, compact and smooth tungsten coatings were successfully obtained. The crystal structure, morphology, density, microhardness, adhesive strength, oxygen content and the thermal conductivity of the coatings fabricated by PC method were investigated. The obtained tungsten coatings had a body centered cubic structure. After electro-deposition for 100 h, the thickness of the tungsten coating reached 810.02 ± 10.40 μm and the oxygen content was 0.03 wt%. The thermal conductivity of the tungsten coating was 134.29 W m^?1 K^?1. The density of the tungsten coating was 18.83 g cm^?3. The hardness of the coating was 492.0 ± 7.8 HV. After deuterium plasma irradiation, the tungsten coatings were prone to blistering.     

Design and Development of a Power Supply System for NBI Test Stand of EAST

A neutral beam injector (NBI) test stand was constructed to develop a multi-megawatt prototype ion source as an auxiliary heating system on experimental advanced superconducting tokamak. A power supply system for the NBI test stand components such as a set of dc power supplies for plasma generator, a dc high voltage power supply of a tetrode accelerator, a transmission line and a surge energy suppressor. Stable arc discharges of the plasma generator with hydrogen gases for 100 s long pulse have been produced by six Langmuir probes feedback loop regulation mode to control the arc power supply. The 4 MW hydrogen ion beam of 1 s is extracted with beam energy of 80 keV and the beam current of 52 A. The dc high voltage power supply for the plasma grid of the prototype ion source was designed to contribute maximum voltage of 100 kV and current of 100 A. The high voltage power output is continuously adjustable to satisfy with plasma physics experiment in operation frequency of 10 Hz. To prevent damage of the beam source at high voltage breakdown, core snubber using deltamax soft magnetic materials have been adopted to satisfy the input energy into the accelerator from the power supply can be reduced to about 5 J in the case of breakdown at 80 kV. For the transmission line, a disc shape multi cable coaxial configuration was adopted and which the dimension of the diameter is 140 mm at the core snubber. The major issues of discharge characteristics with long pulse and beam extraction with high power for the prototype ion source were investigated on the NBI test stand.     

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.     

Effect of spring water on the radon concentration in the air at Masutomi spa in Yamanashi Prefecture,Japan

The concentrations of ²²²Rn existing in air have been studied by using a convenient and highly sensitive Pico-rad detector system at Masutomi spa in Yamanashi Prefecture, Japan. The measurements in air were carried out indoors and outdoors during the winter of 2000 and the summers of 1999 and 2005. The concentrations of ²²²Rn in spring water in this region were measured by the liquid scintillation method. The concentrations of natural radionuclides contained in soils surrounding spa areas were also examined by means of the γ-ray energy spectrometry technique using a Ge diode detector to investigate the correlation between the radionuclides contents and ²²²Rn concentrations in air at each point of interest. The atmospheric ²²²Rn concentrations in these areas were high, ranging from 5 Bq/m³ to 2676 Bq/m³. The radon concentration at each hotel was high in the order of the bath room, the dressing room, the lobby, and the outdoor area near the hotel, with averages and standard deviations of the concentration of 441 ± 79 Bq/m³, 351 ± 283 Bq/m³, 121 ± 5 Bq/m³, and 23 ± 1 Bq/m³, respectively. The source of ²²²Rn in the air in the bath room is more likely to be the spring water than the soil. The spring water plays carries the radon to the atmosphere. Our measurements indicated that the ²²²Rn concentration in the air was affected by the ²²²Rn concentration in spring water rather than that in soil.     

100MeV电子直线加速器激励系统

文章描述了100MeV电子直线加速器激励系统的原理、结构、调试结果和主要技术性能。该系统的中功率速调管放大器能够输出15kW的脉冲功率,经微波输出部分分别激励6只高功率速调管。结果表明,系统结构简单,性能良好,完全满足加速器的使用要求。     

Basic information on new regulatory criteria requiring on-site emergency preparedness for accelerator facilities in Japan

For basic information on new regulatory criteria, the dose rate around a thick target bombarded by proton, electron, or carbon beam having incident energy of 10 MeV–50 GeV (per nucleon in case of carbon) was simulated using the PHITS Monte Carlo code. Based on this simulation, the benchmark which is ‘1 Sv/h at 1 m away from the beam line’ assuming 1% beam loss was evaluated, and compared with the criteria in France and Canada. Based on this evaluation, a new regulatory criteria has been established for requiring on-site emergency preparedness for accelerator facilities in Japan, which is required for the ion accelerator beyond the ion beam of 100 MeV/nucleon and 0.5 kW beam power, and the electron accelerator beyond the electron beam of 50 MeV energy and 1 kW beam power.     

A Comparison of Triodes and Klystrons for Particle Accelerator Applications

In the frequency range between 200 and 1200 mcs, it is possible to use either klystrons or triodes for particle accelerator applications. This paper analyzes the bases of choice between these tube types from a systems point of view. It treats development status, initial and operating costs, reliability, system complexity, and all pertinent technical factors. The tentative specifications of the proton linear accelerator r-f system proposed by Los Alamos are used as a basis for comparison, and the conclusions reached on this system are extrapolated to higher and lower frequencies. It is concluded that either triodes or klystrons can be used in most, if not all, applications and that in almost every significant respect, in the frequency range considered, the klystron system is superior to the triode system.     

The effect of beam loading on the characteristics of an electron linear accelerator

A secondary field, caused by moving bunches of particles in decelerating structures, was found. The basic properties of electron linear accelerators depending on the effect of beam loading were analyzed. The operation of a linear accelerator in stationary and transitional modes, and with short pulse loading, was studied in detail.