Design and test of voltage and current probes for EAST ICRF antenna impedance measurement

On the experimental advanced superconducting tokamak(EAST), a pair of voltage and current probes(V/I probes) is installed on the ion cyclotron radio frequency transmission lines to measure the antenna input impedance, and supplement the conventional measurement technique based on voltage probe arrays. The coupling coefficients of V/I probes are sensitive to their sizes and installing locations, thus they should be determined properly to match the measurement range of data acquisition card. The V/I probes are tested in a testing platform at low power with various artificial loads. The testing results show that the deviation of coupling resistance is small for loads RL??2.5 Ω, while the resistance deviations appear large for loads RL??1.5 Ω, which implies that the power loss cannot be neglected at high VSWR. As the factors that give rise to the deviation of coupling resistance calculation, the phase measurement error is the more significant factor leads to deleterious results rather than the amplitude measurement error. To exclude the possible ingredients that may lead to phase measurement error, the phase detector can be calibrated in steady L-mode scenario and then use the calibrated data for calculation under H-mode cases in EAST experiments.     

Measurement of Ion Cyclotron Emissions by Using High-Frequency Magnetic Probes in the LHD

Two pairs of high-frequency magnetic probes were installed in the Large Helical Device (LHD). During the injection of a perpendicular neutral beam, ion cyclotron emissions (ICEs) with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies (ICRF) heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv¶en eigenmodes (TAE) and the rise of intensity of lost ion °ux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic ¯eld strength, since the ion cyclotron frequency increases with the magnetic ¯eld strength.     

强流回旋加速器静电注入偏转板设计方法研究

从离子在回旋加速器静电注入偏转板中的运动方程出发，对注入偏转板完成了了计算机辅助设计，并给出辅助加工数据。计算设计和束流仿真过程全部在ＰＣ－４８６微机上完成，形成一个注入偏转板设计软件包，并且可以与已开发的“智能化回旋加速器主磁铁ＣＡＥ系统”配套使用，使回旋加速器的整机开发前进了一步。     

Investigation of the confinement of high energy non-neutral proton beam in a bent magnetic mirror

By using the particle-in-cell (PIC) simulation method, we studied how the proton beam is confined in a bent magnetic mirror. It is found that the loss rate of the charged particles in a bent mirror is less than that in the axi-symmetric mirror. For a special bent mirror with the deflection angle of the coils α = 45°, it is found that the loss rate reaches maximum value at certain ion number density where the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency. In addition, the loss rate is irrelevant to the direction of the proton beam. Our results may be helpful to devise a mirror. In order to obtain the least loss rate, we may choose an appropriate deflection angle, and have to avoid a certain ion number density at which the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency.     

Invited Paper-Single Turn Extraction

The salient features of the resonance extractio ystem for the MSU cyclotron have already been described in a series of studies includings the generation of turn separation via the resonance mechanism, the design calculations for the electrostatic and magnetic channels, and the development of the air-core magnetic channel. A report issued in connection with this conference describes the status and presents pertinent data on the performanc of the cyclotron, including the extraction system. Since the issuing of that report, the electrostatic channel has been installed for preliminary tests. Experiments have verified that a suitable field bump drives the beam into this channel with clean turn separation, and that the turn pattern observed under these conditions agrees with orbit computations; the upper part of Fig. 1 shows the turn patter obtained from the differential and integral probe with the deflector in place (the azimuth of the probe is 160° before that of the channel entrance). The air-core magnetic channel is approaching completion and when this channel is installed, the extraction system will beame fully operational.     

回旋加速器引出系统的传输矩阵和引出束发射度

推导了静电引出通道的等效简阶振荡方程(轴向),给出了引出系统的一阶传输矩阵:分析了引出束初始发射度椭圆矩阵的确定方法;给出了束发射度计算结果,并与国外同类型加速器的实测作了比较。     

Influence of the Phase of the Antenna Current Standing Wave on the Power Flux in Ion Cyclotron Heating

For ion cyclotron resonance heating, the current on the antenna surface exists in a form of standing wave, and the phase of the poloidal current standing wave affects significantly on the performance of the coupling. In this paper, a coupling calculation is carried out based on a practical model for the loop antenna. The ion cyclotron wave coupling performance depends greatly on the antenna current propagation constant and the phase of standing wave. For a small antenna-current-propagation constant, the antenna coupling performance is more sensitive to a ?/2 change in the phase of standing wave.     

用于回旋加速器射频低电平系统的通用DSP固件程序设计

针对回旋加速器射频系统幅度、相位、启动逻辑、联锁保护、在线参数修改等控制需求,编写了一种基于有限状态机的通用DSP固件程序。该固件程序将射频系统启动过程划分为5个状态:封锁RF信号、搜索腔体谐振点、提升射频功率、匹配相位、幅相闭环控制。该固件程序通过串口与本地上位机和远程控制机进行实时通信,支持在线修改射频系统启动参数;采用异步事件驱动方式,实现对打火和反射功率过大等异常情况快速响应。该固件程序成功应用于CYCIAE-100回旋加速器射频低电平系统中,在CYCIAE-100回旋加速器调束过程中,完成了射频系统的启动控制和设备保护,满足加速器控制系统的需求。     

An automatic phase-matching technique of CYCIAE-100 cyclotron

The RF system of CYCIAE-100 cyclotron has two cavities,which are driven separately by two identical 100-kW RF amplifiers.Due to the power on sequence issue of the three DDSs in the LLRF systems,each time when the system is individually switched on,the phase relationship may not satisfy the requirements of beam acceleration.Instead of adding an extra reset logic to the system,a search and validation algorithm based on the decision tree has been carried out to make sure the phase of the two cavities is correct right after applying power to the cavities,taking advantage of existing hardware resources.In the first year of operation,there are more than 20 times of scheduled shutdown of the cyclotron system.For each time when the cyclotron RF system is completely shutdown and powered on again,the operator confirmed that the phase matching of the two cavities can be done automatically within 30 s.The related work,including the optimization of the phase detector and the development and validation of the algorithm,is reported in this paper.     

用于硼中子俘获治疗的强流质子回旋加速器中心区结构优化设计

中国原子能科学研究院目前正在研制用于硼中子俘获治疗（BNCT）的强流质子回旋加速器,该加速器设计引出能量14 MeV、质子束流强大于1 mA。相比引出流强为400 μA的PET回旋加速器,BNCT强流质子回旋加速器对中心区相位接收度和轴向聚焦的要求更高。为实现mA量级的束流的加速和引出,BNCT强流质子回旋加速器采取了增加负氢束流注入能量、增大磁铁镶条孔径、使用用于增大Dee盒头部张角的阶梯状结构及调整加速间隙的入口和出口高度等一系列中心区结构优化设计,有效地提高了中心区的相位接收度,改善了轴向电聚焦。在新的离子源注入能量下通过数值计算得到实测场下的轴向电聚焦和间隙高度的关系,选取合适的间隙高度获得最佳的轴向聚焦,从而确定了mA量级束流的注入和加速的中心区结构。同时在设计中考虑空间电荷效应的影响,计算了不同流强下的束流尺寸变化。中心区结构在实测磁场下的优化设计计算结果表明,BNCT强流质子回旋加速器中心区的束流对中好于0.5 mm,相位接收度大于40°,中心区最高可接收流强3 mA。目前,新的中心区结构已进入机械加工阶段。     

Measurement of fast-neutron spectra by time of flight

Summary The time-of-flight neutron spectrometer used with the cyclotron opens up broad new possibilities of use of the cyclotron for the study of nuclear reactions. We shall enumerate several of them. The efficiency of the spectrometer can be brought up to several tens of percent, which permits the study with existing neutron fluxes of secondary processes (for example, the spectra of scattered neutrons entirely free from the background of -rays produced in the target. The spectrometer gives the possibility of studying neutron spectra on a background of harder and more intense groups, thanks to which the first works on the study of neutron spectra [20,21] already gave new physical results. The use of several counters, connected in the spectrometer circuit and in coincidence circuits with each other, allows the study of neutron spectra accompanied by a definite secondary particle, and also of the angular correlations of particles emitted by the target (for example, the angular correlation of -quanta with neutrons of definite energy).The difficulties encountered in the work are mostly connected with instability of the cyclotron. The taking of a spectrum with the existing one-channel circuit requires about an hour. During this time, the phase of ejection of the particles from the cyclotron may change relative to the HF phase because of a change of some of its parameters, and this seriously damages the accuracy of the measurements.In work with deuterons, there are rather large backgrounds of neutrons and -rays produced outside the target. These may be taken into account by making difference measurements (target — flag), since the counting rate is sufficiently high. But the instability of the cyclotron makes the backgrounds variable, which decidedly decreases the reliability of the procedure.To increase the accuracy of the results obtained with the spectrometer, we are now conducting work in two directions: stabilization of the cyclotron and construction of a multichannel circuit.We are deeply grateful to N. A. Vlasov and S. P. Kalinin for their constant interest in the work and their great help in the solution of both theoretical and practical problems.We also thank the collaborators of the cyclotron laboratory, who have aided in the carrying out of this work.     

The residual zonal flow in tokamak plasmas with a poloidal electric field

In a tokamak plasma with auxiliary heating by cyclotron waves, a poloidal electric field will be produced, and as a consequence influence the residual zonal flow(RZF) level. The poloidal electric field can also be induced through biasing electrodes at the edge region of tokamaks.Numerical evaluation for a large aspect ratio circular cross section tokamak for the electron cyclotron wave heating indicates that the RZF level decreases significantly when the poloidal electric field increases. Qualitatively, the ion cyclotron wave heating is able to increase the RZF level. It is difficult to apply the calculation to the real cyclotron wave heating experiments since we need to know factors such as the plasma profiles, the exact power deposition and the cross section geometry, etc. It is possible to use the cyclotron wave heating to control the zonal flow and then to control the turbulence level in tokamak experiments.     

Excitation and Propagetion of Modified Fluctuation in a Toroidal Plasma in KT—5C Device

Understanding the propagation of the turbulent perturbation in the tokamak edge plasma is an important issue to actively modify or control the turbulence,reduce the anomalous transport and improve plasma confinement.To realize active modification of the edge perturbation,a high dynamic output,broad-band,low-cost power amplifier is set up,and used to drive the active probes in the experiments on KT-5C Tokmak.By using small-size magnetic probes together with Langmiur probes,It is observed that the modified perturbation by the active probes with sufficiently driving power may spread with electrostatic mode,and electromagnetic mode as well.     

Numerical Simulation of Main Magnet Electromagnetic Force and Deformation for CYCIAE-100 Project

The achievement of magnetic field plays a crucial part in the design of CYCIAE-100 cyclotron, which is assumed to satisfy various beam dynamics requirements. In the compact cyclotron, magnet deformation caused by gravity, electromagnetic force and atmospheric pressure, impacts the distribution of the field on the middle plane and the space nearby. If the deformation caused by gravity and electromagnetic force is small enough, the field change can be compensated in the field mapping and shimming phase. Otherwise,     

EAST离子回旋系统液态相移器的理论设计

对EAST离子回旋系统液态相移器的原理进行了理论分析和计算,结果表明:利用液态相移器可产生相位差,从而可用离子回旋波进行电流驱动。另外,液态相移器也可与单支节液态调配器结合使用,构成传输线阻抗匹配系统。     

用飞行时间法鉴别粒子的在线三体谱仪的改进

针对迴旋加速器加速相位的不稳定,研制了频率自动微调系统,并用靶上二体事件单能粒子的时间线谱作监控修复信号,减小了迴旋加速器等系统的不稳定而带来的时间幌动,将迴旋加速器上谱仪鉴别粒子的时间分辨降低到<3ns。     

电子回旋波Ohkawa机制电流驱动计算

从电子回旋波电流驱动的机制出发,理论推导出了Boozer-Fisch电流与Ohkawa电流的计算表达式,并给出了具体的计算方法。数值模拟结果表明:电子回旋波的波功率沉积在托卡马克高场侧的离轴位置时,Ohkawa电流较小,Boozer-Fisch电流能达到较大值;波功率沉积在低场侧的离轴位置时,通过调整波参数,有效抑制Boozer-Fisch电流,能充分利用Ohkawa电流的优势使离轴驱动电流同样能达到较大值。     

A PIXE mini-beam setup at the bonn cyclotron for archeometric metal analyses

The exact analysis of the elemental composition at and around a soldering joint of an antique piece of jewelry can elucidate the joining technologies and give hints of the genuineness of the object. As analytical method we use PIXE, which is nondestructive, multielemental and with fundamental parameter calculations gives absolute concentration values. To obtain the necessary spot size of the H₂⁺ beam at the Bonn cyclotron we use a piezo-controlled diaphragm, whose demagnified image is focussed on the target by two magnetic quadrupole triplets. With an electrostatic deflector the beam spot of 0.1 × 0.3 mm² size can be moved 2 mm in each direction on the target. With a laser beam, which simulates the ion beam, an irregularly shaped archeological object can be positioned. The laser is also used to obtain the alignment of the target surface to the ion beam direction and the small beam size makes it easier to find a flat part on the surface of the object; both of these are important preconditions for using the fundamental parameter method. A scan over a joint of modern gold alloys demonstrates the ability to detect soldering joints. The analysis of four pieces of Roman gold jewelry found in the area of Cologne and Bonn shows examples of brazing with a solder as well as diffusion soldering.     

120 cm cyclotron

The basic data on a cyclotron with a pole-piece diameter of 120 cm are given. The arrangement of the principal parts of the system, the design features of the individual units, the radio frequency (rf) installation, the method of measuring and correcting the magnetic field, the features of the deflection system, and the method of focusing the beam on a remote target are all described. Deuterons are accelerated to an energy of 13.7 Mev in this machine. The use of a deflection system with focusing properties makes it possible to use magnetic quadruple lenses with small apertures which bring practically the entire deflected beam to a remote target. The parameters of the machine are such, that it will be possible to increase significantly theenergyof the accelerated ions in the future.The authors wish to thank E. G. Komar for valuable advice, F. K. Arkhangel'skii for great help in tests of the first cyclotron and D. G. Alkhazov for discussion of a number of problems connected with the design of the cyclotron.     

An External Heavy Ion Source for the Berkeley 88-Inch Cyclotron

A heavy ion source of the PIG type has been installed on the axial injection line at the 88-Inch Cyclotron. It is now in the testing phase. Arc powers up to 4 kW have been run, and hydrogen and nitrogen beams have been injected and accelerated in the cyclotron.