Investigation of Impurity Ion Transport with Laser Blow-off in HL-2A Tokamak

Transient perturbation methods are most appropriate to study particle transport in tokamaks. Two most commonly used techniques of impurity injection are laser blow-off and gas puffing. The laser blow-off injection technique is undoubtedly the best one to study impurity transport because the injection time and the alnount of injected material can be controlled in a certain phase of the discharge with a minimum perturbation of the plasma parameters. The information of the impurity transport is obtained from the detection of emission of injected impurity ions located in different spatial regions. The radiation includes line emission, soft X-ray emission and plasma global radiation.     

Investigation of Impurity Ion Transport with Laser Blow-off in HL-2A Tokamak

Non-recycling impurities are injected into ohmic HL-2A plasma for the first time. The impurities of titanium and aluminium are injected in the discharges with varying plasma density and current. The convection and diffusion process of the injected impurity ions during the inward phase are qualitatively investigated. The results show that the transport of impurities is much slower in the central region of the plasma than outside of it and that it is greatly enhanced during sawtooth crashes.     

Studies of the Geodesic Acoustic Mode Zonal Flow in HL-2A Tokamak Plasmas

Zonal flows are universal phenomena in nature and have attracted interse interest in the magnetic fusion plasma physics community in recent years. The active studies in this field are aimed at an understanding of nonlinear physics processes responsible for coherent structure formation and for anomalous transport in plasmas.     

The First Results of Supersonic Molecular Beam Injection in the HL-2A Tokamak

HL-2A tokamak, the first tokamak with divertor in China, has been constructed and put into operation in 2002. The main parameters are R=1.65 m, a=0.4 m, BT=2.8 T, Ip = 0. 48 MA. The divertor of HL-2A is unique, because it is characterized with a large closed divertor chamber. The device has double divertor chamber, but now it is operating with lower single null configuration to study the physics of divertor for the next step design of a divertor. Supersonic molecular beam injection （SMBI） system with LN2 cooling trap was first installed and demonstrated on the HL-2A tokamak in 2004. The first results of SMBI into HL-2A plasma are to demonstrate the function of the HL-2A divertor and to observe the cold pulse propagation during multi-pulse SMBI on HL-2A Tokamak.     

HL-2A中性束大功率离子源的研制

2007年3月,为HL-2A中性束注入器研制的大功率离子源在核工业西南物理研究院成功通过了测试.该离子源为圆柱结构的桶式离子源型;加速器采用三电极的加减速系统.实验运行参数如下:灯丝加热电流1100A,电压12V,弧放电电压120V,弧放电电流1050A,等离子体密度达2.5×1012/cm3,离子流密度0.44A/cm2;在距等离子体电极5mm的平面上,等离子体的均匀性好于5%,工作脉宽2s.离子源物理设计、工程考虑、实验研究结果等将在本文介绍.     

HL-2A中性束大功率离子源的研制

2007年3月, 为HL-2A中性束注入器研制的大功率离子源在核工业西南物理研究院成功通过了测试. 该离子源为圆柱结构的桶式离子源型; 加速器采用三电极的加减速系统. 实验运行参数如下: 灯丝加热电流1100A, 电压12V, 弧放电电压120V, 弧放电电流1050A, 等离子体密度达2.5×10¹²/cm³, 离子流密度0.44A/cm²; 在距等离子体电极5mm的平面上, 等离子体的均匀性好于5%, 工作脉宽2s. 离子源物理设计、工程考虑、实验研究结果等将在本文介绍.     

HL-2A装置Nd:YAG激光汤姆逊散射多道测量系统

 利用Nd:YAG激光汤姆逊散射多道测量系统对等离子体多空间点的电子温度和密度进行了测量。用标准光源和电扫描单色仪构成的标定系统对散射光谱的响应系数进行了标定。给出了等离子体中心附近6空间点的温度和密度的测量结果,时间分辨率为100 ms,空间分辨率约为2.2 cm。对实验结果的不确定度进行了估计,为-12% ~ 12%。实验结果证明：系统可测量等离子体温度的空间范围为-35 ~ -3 cm,实验数据稳定可靠。     

HL-2A装置Nd:YAG激光汤姆逊散射多道测量系统

利用Nd:YAG激光汤姆逊散射多道测量系统对等离子体多空间点的电子温度和密度进行了测量。用标准光源和电扫描单色仪构成的标定系统对散射光谱的响应系数进行了标定。给出了等离子体中心附近6空间点的温度和密度的测量结果,时间分辨率为100 ms,空间分辨率约为2.2 cm。对实验结果的不确定度进行了估计,为-12% ~ 12%。实验结果证明：系统可测量等离子体温度的空间范围为-35 ~ -3 cm,实验数据稳定可靠。     

Installation and Primary Results of a Neutral Particle Analyzer on HL-2A Tokamak

The target of nuclear fusion research is to realize effective and sustainable fusion reaction of hydrogen isotope ions and to get the thermonuclear energy economically. Naturally the parameters of plasma ions are of importance and measurement of the parameters of ions has been an essential concern to the nuclear fusion research work since 1950s. However, the ions are confined by the mag- netic field, one can measure the neutral particles emitting from the plasma to obtain the parameters of ions. The diagnosing of neutral particles is a method by measuring the neutral particles from the plasma to obtain the information （such as energy） of ions, and it is important and foundational to the experi ments as well.     

First Heat and Particles Transport Study in the Globus-M2 Spherical Tokamak with Neutral Beam Injection at the Current Ramp-Up

Technical Physics - The article presents the results of studying the transfer of heat and particles in the Globus-M2 spherical tokamak in discharges with neutral injection at the current ramp up....     

Primary Results of ECRH Experiment and Electron Heat Transport on the HL-2A Tokamak

As an ordinary mainly auxiliary heating on tokamak plasma, electron cyclotron resonance heating （ ECRH ） is an useful method to the study of electron heat transport and confinement performance. In this work, primary results of ECRH experiments on the HL-2A tokamak are presented. The features of confinement and electron heat transport during ECRH are analyzed.     

Pellet Injection Experiments in the HL-2A Tokamak

The advantages of pellet injection as a competitive means of fuelling a tokamak are well known. They include： （ 1 ） deep deposition of fuel, （ 2 ） better fuelling efficiency, （ 3 ） purer plasma, and so on. Meanwhile, improving plasma performance by pellet injection has been proven in many tokamak experiments. The deposition of pellet particles following pellet injection causes a temporal change of the local plasma temperature and density gradients which affects the transport properties of the plasma, so pellet injection can be used as a method of studying the transport process as well.     

Electron Heat Transport during Center Fuelling by Pellet Injection on HL-2A Tokamak

The improved energy confinement has been observed in many tokamaks with center pellet injection since 1980＇s. The pellet enhanced performance （ PEP ） was achieved with high power additional heating in JET and other large tokamaks. The mechanism of the PEP mode has been analyzed theoretically . The analysis shows that a few mechanisms are involved in the reduction of anomalous transport and the relative weight of these mechanisms depends on the experimental conditions. In this paper we report the pellet injection experiment results without auxiliary heating on HL-2A tokamak. Our works focus on the investigation of the electron heat transport in ohmic discharges with center pellet fuelling.     

Control of LHCD on the HL-2A Tokamak

in order to study non-indutive plasma current production, the lower hybrid current drive（LHCD） experiment on the HL-2A tokamak is carried out. Simultaneously a microcomputer has been used to control the whole LHCD system. During the experiment this year, we can monitor and protect the LHCD system by use of the microcomputer control system, which will imediately switch off the microwave power to be launched into the tokamak if the plasma is disrupted. All this ensure that the microwave is injected into the equipment correctly.     

Plasma Behavior with Hydrogen Supersonic Molecular Beam and Cluster Jet Injection in the HL-2A Tokamak

After more than ten years of practice, SMBI has been developed to become a useful fuelling method that is already considered to be an improvement over conventional gas puffing （GP）. The HL-2A tokamak is the first tokamak with divertors in China. The main parameters of HL-2A are R = 1.65 m, α=0.4 m, BT=2.8 T and Ip=0.48 MA. The divertor of the machine now is operated with lower single null configuration. Large hydrogen cluster （〉100 atoms） can be produced at low temperature gas.     

Characteristic of Disruption on HL-2A Tokamak

The tokamak disruption is a dramatic event in which the plasma confinement is suddenly destroyed. Detailed experimental studies of disruptions have been made in many machines. During disruption, the plasma current and plasma thermal energy content collapse in an uncontrollable way, thereby applying mechanical forces and heat loads onto the vacuum vessel components. For that reason, the disruptions in a tokamak must be investigated and the physical processes leading to and occurring at the disruption need to be understood.     

Pellet Enhanced Performance on the HL-2A Tokamak

Enhanced confinement has been achieved by the centre fuelling of pellet injection on the HL-2A tokamak. The energy confinement time increases from 50ms to 140ms after the pellet injection. Experimental results show that the improvement of the confinement is related to the decrease of the electron heat transport. Several phenomena which may lead to the improved confinement have been observed in the experiments. After the pellet injection the hollow electron temperature profile and the peaked electron density profile can be sustained for about 200ms, but the improved confinement remains at about 500ms. Sawtooth features and MHD modes have been observed by soft x-ray array and the Mirnov probes. The weak （or reversed） magnetic shear is thought to be an important cause of the low electron heat transport.