Deuterium and Impurity Flux Measurements in the Boundary Plasma of T-10

Time resolved measurements of deuterium and impurity fluxes in the boundary layer of T-10 tokamak were carried out using carbon strips as deposition probes. Analysing these probes by RBS and ERD deuterium impact energies of 25–40 eV could be estimated from the saturation behaviour of deuterium in carbon. The high impurity concentration level and it's time behaviour give indications for local impurity producing sources playing an important role for the impurity transport in the near wall plasma.     

Laser Blow-Off Injected Impurity 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. Short bursts of impurities, injected using the laser blow-off injection technique, are among other transient perturbation methods, undoubtedly best suited to study impurity transport The injection time and the amount of injected material can be controlled in order to study a certain phase of the discharge with a minimum perturbation of the plasma parameters. Furthermore, the source is of very short duration and thus provides an experimentally more direct measure of impurity transport.     

Investigations of Impurity Atom Deposition in the Limiter Shadow of the T-10 Tokamak by Means of Auger Electron Spectroscopy

The impurity flux in the limiter shadow region of the T-10 tokamak has been studied by exposing a solid probe to the plasma and subsequent investigation of deposits by surface analysis techniques. The main constitutents of the inner construction materials of T-10 could be detected by AES and SIMS. The deposited amount of impurities has been shown to rise with a decrease of the distance between probe and plasma. Long term observations of the metal impurity composition in the limiter shadow region by means of the deposition probe have shown a gradual decrease of the relative Ni concentration, which is explained as a successive deposition of stainless steel limiter material on the Inconel liner. The observed spatial asymmetry of the impurity flux and the deposition profiles for different elements on the probe are discussed.     

First Results of Biasing Experiments on the T-10 Tokamak

The first results of the electrode biasing experiments performed on the T-10 tokamak are presented. Positive voltage applied to an electrode inserted inside the tokamak limiter results in the H-mode transition characterised by a decrease of D emission intensity, a rise of line-average plasma density and an increase in energy lifetime. Growth of core electron and ion temperatures during the electrode biasing implies the formation of the thermal barrier in addition to the particle transport barrier.     

The Progression of the Impurities Injected into the Plasma Following by Soft X-ray Arrays on HL-2A Tokamak

Small amounts of metallic impurity is injected by laser blow-off on HL-2A tokamak in order to study transport phenomena. The particle transport is interpretated along     

Numerical Modelling of Impurity Retention in the ITER Tokamak Scrape-off Layer Plasma

The hydrogen plasma and carbon ions flows generated at the target plates in the ITER tokamak scrape-off layer are numerically investigated. A 2D model of hydrogen plasma and impurity ions is presented. The model is based on the electron-ion Braginski fluid equations [1] for hydrogen plasma and rate equations for impurities. Arbitrary level of impurity ions concentration is assumed. Recycling of hydrogen, sputtering and self sputtering of carbon atoms at the target plates are taken into account. Equations of the model are solved in the slab geometry using 2D-multifluid numerical code EPIT [2]. Problems of impurity ions retention and radiation in the divertor volume are analyzed. Results of calculations for ITER tokamak boundary plasma are presented, showing that poor retention is likely at high impurity concentration in the divertor volume. The radiation power can be a significant part of ingoing energy.     

Rotating Mach Probe for Ion Flow Measurements on the CASTOR Tokamak

A rotating Mach probe is designed and used for measurement of plasma flows on the CASTOR tokamak. Measurements are performed at standard discharge conditions as well as in shots with edge plasma polarization. The one dimensional fluid model is developed to deduce the parallel and perpendicular Mach numbers from experimental data.     

Probe Measurements in a Beam Plasma Discharge

The influence of the beam energy and beam current density on the parameters of the plasma is investigated. The efficiency of carrier generation by collective interactions (Langmuir-oscillations) is compared with that by the single collision mechanism. The additional negative charging of the static probe caused by the beam electrons is used for the determination of the beam electron density.     

Modifications of the Surface of a Stainless Steel Limiter During Operation in the T-10 Tokamak

Parts of a stainless steel limiter used in the T-10 tokamak for about 1000 discharges have been analyzed by several standard analysis techniques as SEM, EDS, SAM, AES, RBS and SIMS with respect to modifications of surface structure and chemical composition. Erosion phenomena due to melting and evaporation, arcing, and sputtering could be observed on limiter parts exposed to the plasma flux. In these regions the chemical composition was changed only slightly, whereas in regions shielded by other internal structures of T-10 impurity layers with a thickness up to about 3000 Å were deposited. Additionally on the limiter surface there has been found a considerable number of microscopic particles. They seem to originate from different internal components of T-10, as the fixed W/Mo-limiter, a Ti-anode, and Inconel made parts of the vessel.     

Edge Plasma Biasing Experiments on the CASTOR Tokamak: Spectroscopic Investigation and Microwave Measurements

The effects of edge plasma biasing have been recently investigated by different spectroscopic diagnostics on the CASTOR tokamak. Measurements in visible, VUV and XUV ranges complement the knowledge of processes during a biasing phase, and confirm the occurrence of several types of plasma biasing regimes — so called radiating regime, non-radiating regime, and reduced H regime. The use of edge plasma biasing to study the possibility of Electron Bernstein Wave conversion has been demonstrated.     

EAST托卡马克杂质输运蒙特卡洛模拟

介绍DIVIMP程序的基本思想和采用的物理模型,研究EAST托卡马克欧姆放电条件下碳杂质的产生与输运.模拟结果与实验测量具有较好的一致性,说明将该程序应用于EAST装置中杂质输运模拟的合理性.并利用DIVIMP程序预测EAST在8MW加热功率条件下钨杂质的输运特性.     

Properties of the Tokamak Edge Plasma

A short review of some features of the edge plasma in limiter tokamaks is given. The limits of the simple 1-D SOL model and the relation between the core plasma are discussed. MARFE phenomena and detached plasma are closely connected with the particle and energy balance of the SOL. Their occurrence is based on the relation of plasma parameters of the edge plasma to those of the core. Important problems of plasma wall interactions are the detection of the impurity sources and sinks and the study of the impurity transport and shielding. The non-uniform character of plasma wall interactions and their dependence on the discharge performance still renders difficult any theoretical forecast of impurity distribution and transport and calls for better diagnostics.     

Runaway Electron Measurements in the EAST Tokamak

An experimental study of runaway electrons in the EAST tokamak has been performed by a recently developed multi‐channel hard x‐ray diagnostics based on NaI(TL) scintillator detectors. It is found that in the current quench phase, the inductive loop voltage plays an important role in the generation of runaway electrons. And the avalanche mechanism was the main mechanism for runaway electrons after the disruptions. The distribution and transportation of runaway electrons were also investigated by multi‐channel hard x‐ray diagnostics. It is also found that the intensity of runaway electrons emission in the core plasma was much higher than those in the downside of the cross‐section, while the emission intensity of runaway electrons in the core plasma was almost the same. Calculated shrinking coefficient of runaway electrons emission after the plasma disruption was about 26 m/s according to the experimental data (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simulation of a Planar Emissive Probe in a Mid‐Sized Tokamak Plasma

Planar emissive probe is studied for the first time using a massively parallel particle‐in‐cell code BIT1 [22]. The probe is immersed in a plasma similar to edge plasmas of mid‐sized tokamaks. Dependence of the floating potential on electron emission from the probe is studied. With increasing emission the floating potential increases, but then saturates ～2T_e below the actual plasma potential (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tangential System of Thomson Scattering for Tokamak T-15

Two systems of Thomson scattering diagnostics, with vertical and tangential probing, are used in the D-shaped plasma cross section in tokamak T-15. The tangential system allows measuring plasma temperature and density profiles along the major radius of the tokamak. This paper presents the tangential system project. The system is based on a Nd:YAG laser with wavelength of 1064 nm, pulse energy of 3 J, pulse duration of 10 ns, and repetition rate of 100 Hz. The chosen geometry allows collecting light from ten uniformly spaced points. Optimization of the registration system has been accomplished. The collected light will be transmitted through an optical fiber bundle with diameter of 3 mm and quartz fibers (numerical aperture is 0.22). Six-channel polychromators based on high-contrast interference filters have been chosen as spectral equipment. The radiation will be registered by avalanche photodiodes. The technique of electron temperature and density measurement is described, and estimation of its accuracy is carried out. The proposed system allows measuring the electron temperature with accuracy not worse than 10% within the range of 50 eV to 10 keV on the pinch edge over the internal contour, from 20 eV to 9 keV in the plasma central region, and from 2 eV to 400 eV on the pinch edge over the outer contour. The estimation is made for electron density of not less than 2.6 × 10¹³ cm^–3.     

Doppler Broadening and Magnetic Field Effects on Some Ion Impurity Spectra Emitted in the Boundary Layer of a Tokamak Plasma

Examples are presented of Doppler broadening measurements on singlet, doublet and triplet emission spectra from the following impurity ions found in the boundary layer of the TEXTOR tokamak: Cii, Ciii, Civ, Siii, and Siiii. The shapes of these spectral lines are significantly influenced by the confining magnetic field of some 2T, in some cases exhibiting an appreciable Paschen-Back effect which complicates their appearance. It is shown that reliable values for the particular ion temperature can be obtained from the Doppler widths of the various Zeeman components, when the presence of the magnetic field is properly accounted for. Such temperatures derived from partially ionised impurity species should, however, be cautiously interpreted, as the ions in question probably do not exist for long enough in the particular ionisation stage to achieve thermal equilibrium with the background deuterons and protons. This interpretation of our results is supported by a simple one-dimensional model of ionisation and collisional heating processes in the plasma boundary.     

Analysis of the Limiter Material Erosion in T-3M Tokamak

The limiter material erosion dynamics under disruption instability in T-3M tokamak was studied. Erosion mechanisms of graphite (uglesitall) and boron nitride were examined. It was shown that the erosion of the limiter arises not only at the moment of disruption, but also before it, when the MHD perturbations of plasma column emerge. We had evidence of the superthermal electrons playing a significant role in the limiter erosion. The erosion decreases with the plasma density rising above the threshold value.     

光谱法测量托卡马克等离子体

对托卡马克内部的等离子体进行光谱测量可以得到其内部各种等离子体的状态以及分布等信息。对于不同的测量对象,可以采用各种不同的测量仪器组合以得到较好的结果。文章列出了几种主要的实验方案以及各种方案的测量范围,还有部分测量结果。另外,根据实验的需要设计了另外一种实验组合方案。