HL-2A 装置边缘湍流与带状流相互作用的实验研究

利用组合静电探针阵列研究了HL-2A装置中湍流与带状流相互作用的动力学过程。实验结果表明,在粒子注入后的等离子体恢复阶段,边界区径向电场剖面逐渐变陡,湍流相干尺度和带状流幅度相应增加,而湍流强度随之降低。这些实验提供了带状流与边缘湍流相互作用的直接实验证据,暗示了能量转移是引起带状流增长的主要原因。

An improved TDE technique for derivation of 2D turbulence structures based on GPI data in toroidal plasma

This paper reports an improved time-delay estimation(TDE)technique for the derivation of turbulence structures based on gas-puff imaging data.The improved TDE technique,integrating an inverse timing search and hierarchical strategy,offers superior accuracy in calculating turbulent velocity field maps and analyzing blob dynamics,which has the power to obtain the radial profiles of equilibrium poloidal velocity,blob size and its radial velocity,even the fluctuation analysis,such as geodesic acoustic modes and quasi-coherent mode,etc.This improved technique could provide important 2D information for the study of edge turbulence and blob dynamics,advancing the understanding of edge turbulence physics in fusion plasmas.

Evolution of edge turbulent transport induced by L-mode detachment in the HL-2A tokamak

This paper presents the characteristics of L-mode detachment,together with the behavior of edge turbulent transport and plasma confinement on the HL-2A tokamak.Partially detached and pronounced detached states have been achieved in L-mode plasma.Stored energy was maintained before and after detachment.Edge turbulence and its transport have increased obviously in the partially detached state.In the pronounced detached state,redistribution of the density and temperature profiles due to detachment leads to low amplitude of electron temperature and pressure,as well as very weak edge turbulence and transport.Despite strong plasma radiation in the pronounced detached state,reduced edge turbulent transport contributes to maintaining stored energy in detached L-mode plasma in HL-2A.Different detachment states play an important role in the redistribution of density and temperature profiles,which requires further study.

HL-2A装置上灰尘研究的初步结果

利用HL-2A装置原有的可见光CCD UC-610相机观测到了在等离子体放电过程中存在大量的灰尘,并通过扫描电子显微镜(SEM)和X射线能谱仪(EDX)了解到了辐照石墨样品的表面形貌及杂质元素成分。

Experimental and modeling researches of dust particles in the HL-2A tokamak

The investigation of dust particle characteristics in fusion devices has become more and more imperative.In the HL-2A tokamak,the morphologies and compositions of dust particles are analyzed by using scanning electron microscopy（SEM） and energy dispersive x-ray spectroscopy（EDX） with mapping.The results indicate that the sizes of dust particles are in a range from 1 μm to 1 mm.Surprisingly,stainless steel spheres with a diameter of 2.5μm-30 μm are obtained.The production mechanisms of dust particles include flaking,disintegration,agglomeration,and arcing.In addition,dynamic characteristics of the flaking dust particles are observed by a CMOS fast framing camera and simulated by a computer program.Both of the results display that the ion friction force is dominant in the toroidal direction,while the centrifugal force is crucial in the radial direction.Therefore,the visible dust particles are accelerated toriodally by the ion friction force and migrated radially by the centrifugal force.The averaged velocity of the grain is on the order of^100 m/s.These results provide an additional supplement for one of critical plasma-wall interaction（PWI） issues in the framework of the International Thermonuclear Experimental Reactor（ITER） programme.

Upgrade of an integrated Langmuir probe system on the closed divertor target plates in the HL-2A tokamak

A newly designed divertor Langmuir probe diagnostic system has been installed in a rare closed divertor of the HL-2A tokamak and steadily operated for the study of divertor physics involved edge-localized mode mitigation,detachment and redistribution of heat flux,etc.Two sets of probe arrays including 274 probe tips were placed at two ports(approximately 180°separated toroidally),and the spatial and temporal resolutions of this measurement system could reach6 mm and 1μs,respectively.A novel design of the ceramic isolation ring can ensure reliable electrical insulation property between the graphite tip and the copper substrate plate where plasma impurities and the dust are deposited into the gaps for a long experimental time.Meanwhile,the condition monitoring and mode conversion between single and triple probe of the probe system could be conveniently implemented via a remote-control station.The preliminary experimental result shows that the divertor Langmuir probe system is capable of measuring the high spatiotemporal parameters involved the plasma density,electron temperature,particle flux as well as heat flux during the ELMy H-mode discharges.

The Supervisory Control System for the HL-2A Neutral Beam Injector

Supervisory control and protection system of the neutral beam injector （NBI） in the HL-2A tokamak is presented. The system is used for a safe coordination of all the main NBI subsystems. Because the system is based on computer networks with its transmission medium of optical fiber, its advantages in high operational stability, reliability, security and flexible functional expandability are clearly shown during the NBI commissioning and heating experiment in HL-2A.

HL-2A装置偏滤器靶板热通量的研究

用HL-2A装置下偏滤器室内的红外测温系统和靶板朗缪尔探针系统分别测量了HL-2A偏滤器靶板上的等离子体沉积功率分布,并进行了对比分析。对HL-2A外偏滤器靶板热流的径向和环向沉积结构分布特征的分析表明,HL-2A装置上靶板热流在径向上基本上呈指数衰减分布,其衰减长度在5~7mm左右。

Dust Charging and Dynamics in Tokamaks

Fundamental characteristics of charging of a dust particle and its dynamics in SOL/divertor plasma in tokamaks are studied. According to the OML （orbit motion limited） theory, the charging process is extremely faster, with a charging time of nanoseconds, than the dynamics process of the dust particle in SOL/divertor plasma, with a characteristic time of mil- liseconds, which means that the local charge state can be taken as the equilibrium charge state. It was clarified that the equilibrium charge Zd, eq can be determined in the form of Zd, eq/RdTe, which is a function of both the normalized relative speed of plasma ion flow with respect to the velocity of the dust particle and the plasma temperature ratio. After the investigation of domi- nant forces acting on dust particles, the friction forces due to the plasma ion absorption and ion Coulomb scattering are found of the same order for the case of low relative speed. The critical radius of a dust particle, for which the gravity is larger than the friction forces due to plasma ions, is obtained.

Effect of edge turbulent transport on scrape-off layer width on HL-2A tokamak

Effect of edge turbulent transport on scrape-off layer(SOL)width has been investigated in Ohmically heated L-mode plasma under limiter configurations on HL-2A tokamak.It has been found that SOL width is doubled when plasma current decreases about 20%.With larger plasma current,E×B shear is stronger and has greater suppression effect on edge turbulent transport.SOL width is larger when power of relative density fluctuation level in the edge region is larger.It is concluded that edge turbulent transport plays a significant role on SOL width.These experimental findings may provide a better understanding and controlling of power exhaust for present and future fusion devices.

Scaling Laws of Heat Flux Width in the HL-2A Closed Divertor Tokamak

The scaling law of divertor heat flux width is one of the key topics of magnetic confinement fusion,which is almost inversely proportional to the poloidal magnetic field on some opened divertor tokamaks.This work focuses on the scaling laws of the closed divertor heat flux width in the HL-2 A tokamak under different discharge conditions,such as the Ohmic,L-and H-modes.The results indicate that there are basic similarities of the scaling laws of the heat flux width between the opened and closed divertors.However,a larger spreading width in the private flux region is found,which is relevant to a small expansion factor of the magnetic flux in the closed divertor.

Impact of the mass isotope on plasma confinement and transport properties in the HL-2A tokamak

The impact of the mass isotope on plasma conflnement and transport properties has been investigated in Ohmically-heated hydrogen and deuterium plasmas in the HL-2 A tokamak.Experimental results show that under similar discharge parameters the deuterium plasma has better conflnement and lower turbulent transport than the hydrogen one,and concomitantly,it is found that the magnitude of geodesic acoustic mode zonal flows,the tilting angle of the Reynolds stress tensor and the turbulence correlation lengths are all larger in the edge region of the deuterium plasma.The results provide direct experimental evidence on the importance of the nonlinear energy coupling between ambient turbulence and zonal flows for governing the isotope effects in fusion plasmas.

TZ-2高压电源调制器的研制

本文介绍了HL-2A装置的电子回旋共振加热使用的高压电源调制器的研制。该电源为电子回旋管供电，要求操作简便和运用灵活并具有较高稳定度，高压隔离好，且要有快速保护功能，以确保HL-2A装置放电期间人身安全和设备安全。在2006年假负载、电子回旋管的调试和HL-2A装置的电子回旋共振加热物理实验中，该调制器达到设计参数指标，使高压电源满足了实验的要求。