Transport of Intense Ion Beams

The possibility of using intense bursts of heavy ions to initiate an inertially confined fusion reaction has stimulated interest in the transport of intense unneutralized heavy ion beams by quadrupole or solenoid systems. We have examined this problem in somne detail, using numerical integration of the coupled envelope equations for the quadrupole case. The general relations which emerge are used to develop examples of high energy transport systems and as a basis for discussing the limitations imposed by a transport system on achievable intensities for initial acceleration.     

一台可产生直流束和微秒脉冲束的ECR离子源

ECR离子源与其他离子源相比具有一些优点。例如在放电室中具有较低的工作气压,能产生均匀的高密度等离子体,由于无热阴极可耐腐蚀气体,工作寿命长、发射度小、高原子离子比和束流强度大。所以,应用在中子发生器中具有良好发展前景。专门应用于中子发生器的ECR离子源既可引出直流离子束,又可引出微秒脉冲离子束。介绍了这种ECR离子源的工作原理和结构,给出了测量到的主要参数和脉冲波形。     

New Method of Large-Area DC Ion Beam Formation with Multiple Electron Beams, (I)

A study was made of the correlation between the focusing of an ion beam and the spatial distribution of the ion density in the source plasma, which determines the geometrical shape of the plasma boundary, using a duoplasmatron ion source. It was revealed that the focusing of the ion beams extracted from a gaseous plasma through a large-area single aperture is sensitively influenced by the concavity of the plasma boundary, which concavity varies with the radial density profile of the plasma ions at the plasma boundary.     

New Method of Large-Area DC Ion Beam Formation with Multiple Electron Beams, (II)

A new method to form a small divergence dc ion beam using a large-area single-hole electrode instead of a multiaperture electrode is described. A distinctive feature of this method is to make use of multiple electron beams in an ion source to control the spatial ion density distribution at the region of ion beam formation; the electron beams play a role to aid formation of the concave plasma boundary, which is required to extract a convergent ion beam from gaseous plasma according to the experimental facts described in Part (I). In this experiment, it was verified with three slab-like electron beams that formation of the concave boundary was possible in a stable and steady state. This electrode system can be applied to some types of the present high current ion sources to obtain large-area dc ion beams.     

CIAE强流ECR离子源研制

本文介绍了研制的一台强流ECR微波离子源,其能从7 mm直径的圆孔引出大于150 mA的氢离子束(75 keV),质子比达90%。该离子源采用独特的结构提高了离子源寿命。离子源在75 keV、110 mA束流条件下连续工作超过220 h,束流中断2次,不间断工作时间超过150 h。     

The Development of a Megawatt-Level High Current Ion Source

Neutral beam injection is one of the main plasma heating methods in nuclear fusion devices. In order to support the scientific study of the Experimental Advanced Superconducting Tokamak (EAST), a megawatt-level high current ion source is designed and manufactured in the ASIPP, and the progress and preliminary test results will be presented in this paper.     

Numerical Calculation of High Energy and High Current Negative Ion Beam System

In next generation large fusion devices, neutral beam injection with high energy and high power is a main tool for core plasma heating, non-induced current drive, current profile and ignition burn temperature control in high density plasma. Becase a negative ion with high energy has still higher neutral conversion efficiency, to develop the negative     

Symmetric Neutralized Ion Beams for Magnetic Fusion Applications

A symmetric neutralized ion beam (SNIB) is composed of positive and negative ions, and is capable of propagating across a transverse magnetic field due to the polarization of the beam. Such a beam may be of use as an alternative or complement to conventional neutral beam injection (NBI) in magnetic confinement fusion devices. SNIBs of energies from hundreds of keV up to a few MeV can be efficiently produced through a novel application of radio frequency quadrupole (RFQ) accelerators. Because the cross-field propagation ability of the SNIB depends mainly on beam density, SNIBs of significantly lower energy than the 1 MeV envisioned for ITER neutral beams can in principle reach the center of a magnetically confined plasma. Some challenges that need to be overcome for this technique to be viable are identified; nevertheless, the approach is attractive when compared to the bulky, high voltage, conventional neutral beam systems. Distributed injection of many beams is possible due to the relative compactness of a SNIB module.     

Study the Characteristic of the Hot Cathode of High Current Ion Source

The difference of hot cathode operation mode has great influence on the arc discharge of high current ion source. Based on the analysis of the theory of hot filament with two operation modes and combined with ion source experiments, the paper studies the effects of hot filament operation modes on ion source arc discharge.     

箍缩反射离子二极管产生的强流脉冲离子束特性

通过对离子束流密度分布的测量和对被离子束轰击的铜箔不同半径处表面微观形貌的分析,研究了200kV箍缩反射离子二极管产生的离子束特性。结果表明：轴线上离子束流密度最大。     

Preliminary Research Results for the Generation and Diagnostics of High Power Ion Beams on FLASH II Accelerator

The preliminary experimental results of the generation and diagnostics of highpower ion beams on FLASH II accelerator are reported, The high-power ion beams presently are being produced in a pinched diode, The method for enhancing the ratio of ion to electron current is to increase the electron residing time by pinching the electron flow, Furthermore, electron beam pinching can be combined with electron reflexing to achieve ion beams with even higher efficiency and intensity. The anode plasma is generated by anode foil bombarded with electron and anode foil surface flashover. In recent experiments on FLASH II accelerator, ion beams have been produced with a current of 160 kA and an energy of 500 keV corresponding to an ion beam peak power of about 80 GW. The ion number and current of high power ion beams were determined by monitoring delayed radioactivity from nuclear reactions induced in a ^12C target by the proton beams, The prompt γ-rays and diode bremsstrahlung X-rays were measured with a PIN semi-conductor detector and a plastic scintillator detector, The current density distribution of ion beam were measured with a biased ion collector array. The ion beams were also recorded with a CR-39 detector.     

Properties of Ion Beams Generated by Nitrogen Plasma Focus

Numerical experiments have been systematically carried out using the modified Lee model code on various plasma focus devices operated with nitrogen gas. The ion beam properties (ion beam energy, ion beam flux, ion beam fluence, beam ion number, ion beam current, power flow density, and damage factor) of the plasma focus have been studied versus gas pressure for each plasma focus device. The results show that, for these studied plasma focus devices, the mean ion energies decrease with increasing gas pressure, while the beam ion number increases with higher pressure. The fluence, flux, ion current, power flow density and damage factor have maximum values at the optimum pressure. It is shown that, the maximum power flow densities range from 10¹² to 10¹⁴ W m^?2 and the damage factor values reach almost 10⁹–10¹¹ W m^?2 s^0.5. The obtained results provide much needed benchmark reference values and scaling trends for ion beams of a plasma focus operated in nitrogen gas. These results could be used as an indicator for ion properties emitted from nitrogen plasma focus for various applications including material processing.     

Atomic Collision Experiments Utilizing Low-Velocity, Highly-Charged Ion Beams

Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandems in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S6-16+ on He and Ar at 6-20 MeV and P(b) measurements for MO x-rays produced in Cl16+ + Ar collisions at 20, 10 and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed.     

强流脉冲离子束核物理参数诊断技术初步研究

在“闪光二号”加速器产生的强流脉冲离子束(IPIB)调试过程中采用复合法进行参数诊断。主要测量质子与C靶的核反应所产生的放射性核素的活度，从而确定离子数目。采用PIN探测器和闪烁体光电倍增管(光电管)监测瞬发γ射线和轫致辐射X射线，用热释光探测器(TLD)监测漂移管外部的轫致辐射并确定了相应的屏蔽方法。采用偏压离子收集阵列测量离子束流密度分布，采用固体核径迹探测器CR-39初步测量离子束流。     

脉冲离子束轰击靶的热效应数值模拟

分析了脉冲离子轰击靶膜和衬底的热效应,在能量较低的情形下,离子轰击处理为靶膜表面热流输入。采用有限元程序,对能量为600keV、束流为12mA的不同束斑半径的脉冲离子流轰击Cu基Ti靶的热传导进行了数值计算,得到了热传导清晰物理图象。     

Ion Temperature Effect on Weakly Collisional DC Plasma Sheath

Using a collisional two-fluid model, we investigate the ion temperature effect on the sheath formation criterion as well as the sheath structure in electropositive plasmas. In this work, temperature dependence of the characteristics of a weakly collisional DC plasma sheath is examined numerically. It will be shown in the constant cathode electric potential, the more the ion temperature, the low the thickness of sheath. Moreover, for a special set of physical parameters, the sheath formation criterion is not fulfilled for ion temperature under a minimum value.     

A High Precision DC Restorer

The performance of high resolution pulse amplitude spectrometers is often seriously degraded at high counting rates due to baseline problems of various kinds. A variation on the Robinson double-diode dc restorer is presented which makes it possible to obtain high resolution with Li-drifted Ge spectrometers at counting rates greater than 50,000 per second.     

On the Generation and Focusing of Intense Ion Beams for Pellet Fusion

The current limits of magnetic focusing systems are examined and approximate formulas for long solenoids and periodic channels with short lenses (solenoids and quadrupole doublets) are derived. The characteristics and limitations of conventional sources, pulsed ion diodes, and collective-field accelerators for the generation of intense, energetic ion beams are compared. Use of a collective-ion accelerator with debuncher is suggested as injector into an induction accelerator.