在新闭合偏滤器Ⅱ位形下ASDEX—U H模式放电的运行极限

报道了对ASDEX－U新闭合偏滤器Ⅱ的加气,高密度H模式放电的系统研究,重点放在很宽的外部可控等离子体参数范围内的运行极限（H－L转变,密度极限）上,发现,当接近高密度时,H模式阈功率大大超出普遍认可的预言Ph^th ncBt。在接近H－L模反转变时,获得了最高密度（密度极限）。该密度极限通常与偏滤器的完全脱离有关。为了基于脱离的模型和Greenwald极限,研究并讨论密度极限定标。     

核电站群堆运行模式下热释光剂量计的管理方法探讨

探讨了大亚湾核电站以及其他核电站所采取的热释光剂量计(TLD)的管理方法,对其管理模式的优缺点进行分析和评价.针对核电站多基地的群堆运行模式,提出了一种全新的管理方法-智能管理模式,它是一种既可保证测量的准确度又能大大降低生产成本、提高管理效率的最优化管理模式.     

Space-resolved vacuum-ultraviolet spectroscopy for measuring impurity emission from divertor region of EAST tokamak

The measurement of impurity distribution in the divertor region of tokamaks is key to studying edge impurity transport. Therefore, a space-resolved vacuum-ultraviolet (VUV) spectrometer is designed to measure impurity emission in the divertor region on EAST. For good spectral resolution, an eagle-type VUV spectrometer with 1 m long focal length with spherical holograph grating is used in the system. For light collection, a collimating mirror is installed between the EAST plasma and the VUV spectrometer to extend the observing range to cover the upper divertor region. Two types of detectors, i.e. a back-illuminated charge-coupled device detector and a photomultiplier-tube detector, are adopted for the spectral measurement and high-frequency intensity measurement for feedback control, respectively. The angle between the entrance and exit optical axis is fixed at 15°. The detector can be moved along the exit axis to maintain a good focusing position when the wavelength is scanned by rotating the grating. The profile of impurity emissions is projected through the space-resolved slit, which is set horizontally. The spectrometer is equipped with two gratings with 2400 grooves/mm and 2160 grooves/mm, respectively. The overall aberration of the system is reduced by accurate detector positioning. As a result, the total spectral broadening can be reduced to about 0.013 nm. The simulated performance of the system is found to satisfy the requirement of measurement of impurity emissions from the divertor area of the EAST tokamak.     

Divertor detachment operation in helium plasmas with ITER-like tungsten divertor in EAST

Detachment in helium (He) discharges has been achieved in the EAST superconducting tokamak equipped with an ITER-like tungsten divertor. This paper presents the experimental observations of divertor detachment achieved by increasing the plasma density in He discharges. During density ramp-up, the particle flux shows a clear rollover, while the electron temperature around the outer strike point is decreasing simultaneously. The divertor detachment also exhibits a significant difference from that observed in comparable deuterium (D) discharges. The density threshold of detachment in the He plasma is higher than that in the D plasma for the same heating power, and increases with the heating power. Moreover, detachment assisted with neon (Ne) seeding was also performed in L- and H-mode plasmas, pointing to the direction for reducing the density threshold of detachment in He operation. However, excessive Ne seeding causes confinement degradation during the divertor detachment phase. The precise feedback control of impurity seeding will be performed in EAST to improve the compatibility of core plasma performance with divertor detachment for future high heating power operations.     

Influence of impurity seeding on the plasma radiation in the EAST tokamak

Plasma radiation characteristics in EAST argon(Ar) gas and neon(Ne) gas seeding experiments are studied.The radiation profiles reconstructed from the fast bolometer measurement data by tomography method are compared with the ones got from the simulation program based on corona model.And the simulation results coincide roughly with the experimental data.For Ar seeding discharges,the substantial enhanced radiations can be generally observed in the edge areas at normalized radius ρ_(pol)~0.7–0.9,while the enhanced regions are more outer for Ne seeding discharges.The influence of seeded Ar gas on the core radiation is related to the injected position.In discharges with LSN divertor configuration,the Ar ions can permeate into the core region more easily when being injected from the opposite upper divertor ports.In USN divertor configuration,the W impurity sputtered from the upper divertor target plates are observed to be an important contributor to the increase of the core radiation no matter impurity seeding from any ports.The maximum radiated power fractions f_(rad)(P_(rad)/P_(heat)) about 60%–70% have been achieved in the recent EAST experimental campaign in 2015–2016.     

OEDGE modeling of plasma contamination efficiency of Ar puffing from different divertor locations in EAST

Modeling with OEDGE was carried out to assess the initial and long-term plasma contamination efficiency of Ar puffing from different divertor locations,i.e.the inner divertor,the outer divertor and the dome,in the EAST superconducting tokamak for typical ohmic plasma conditions.It was found that the initial Ar contamination efficiency is dependent on the local plasma conditions at the different gas puff locations.However,it quickly approaches a similar steady state value for Ar recycling efficiency ＞0.9.OEDGE modeling shows that the final equilibrium Ar contamination efficiency is significantly lower for the more closed lower divertor than that for the upper divertor.     

Modelling of hydrogen isotope retention in the tungsten divertor of EAST during ELMy H-mode

In this work, we study hydrogen isotopes (HI) inventory inside tungsten plasma-facing materials during high confinement mode discharges with repetitive edge localized modes (ELMy H-mode) based on the operating parameters of the EAST device, since tungsten is considered as the primary plasma-facing material and the ELMy H-mode is an important operation regime for EAST and future devices. The upgraded Hydrogen Isotope Inventory Processes Code (HIIPC) is applied with the incident depth profile provided by SRIM-2013 to make the study. The code is first verified by comparison with experimental measurements. The effects of the incident ion energy and ion flux on the retention are then studied. Finally, using the parameters obtained from EAST diagnostics, the HI retention inside the W divertor during ELMy H-mode is studied, which indicates the retained HI can be increased dramatically mainly due to ion-induced trap sites by ELMs.     

Electron density calculation based on Stark broadening of D Balmer line from detached plasma in EAST tungsten divertor

The electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak (EAST) is calculated based on D_ε line (396.9 nm) Stark broadening (SB) measurements. The quasistatic approximation is employed in the SB calculation of the D_ε line. The influences of other broadening mechanisms on the calculation error of electron density have been evaluated. The SB method is applied to the study of spatial distribution and time evolution of the electron density in the W divertor. Two electron density bands are observed in the detached divertor plasma during an L-mode discharge sustained by low hybrid wave (LHW) heating, which could be related to the striated particle flux distribution induced by LHW. After the onset of detachment, the upper electron density band corresponding to outer strike point firstly increases then decreases, while the lower density band corresponding to striated particle flux increases continually although the electron densities from Langmuir Probes at the divertor plate keep a descending trend. This could indicate a downward movement of the radiation region that approximately moves along the magnetic field lines after the onset of detachment.     

The design, analysis and alignment of EAST divertor

The divertor of EAST is composed of inner-target, outer-target and dome. Every kind of target has 16 separate modules along toroidal direction. The structure of divertor includes support, heat sink and the first wall graphite. The shape and dimension of divertor are optimized for flexible operation of different elongation and triangularity of plasma. The eddy current and halo current interact with high toroidal magnetic field will produce large forces on divertor, so the structure of divertor must bear these electromagnetic forces. The first wall of divertor must have high assembly accuracy of 0.5 mm. The traditional method using optical instruments to survey directly is impractical because of the especial location of divertor. The benchmark templet integrates with optical instruments to align the divertor is proved simple and effective.     

Achieving temporary divertor plasma detachment with MARFE events by pellet injection in the EAST superconducting tokamak

A new pellet injection system has been equipped on the experimental advanced superconducting tokamak(EAST) in the 2012 campaign,with a pellet size of Ф 2 mm?×?2 mm,a frequency of1 Hz–10 Hz and velocity of 150 m s~(-1)–300 m s~(-1).The deuterium pellet is well-known for plasma fuelling as well as for? triggering the edge localized mode(ELM).In the 2012 campaign,pellet injection experiments were successfully carried out on EAST.Temporary plasma detachment achieved by deuterium pellets has been observed in a double null(DN) divertor configuration,with multi-pellet injections at a repetition frequency of 2 Hz.The partial detachment of the outer divertors and complete detachment of the inner divertors was achieved after 35 ms of each pellet injection,which have a duration of 30–60 ms with the maximum degree of detachment(DOD) reaching 3.5 and 37,respectively.Meanwhile,the multifaceted asymmetric radiation from the edge(MARFE) phenomena was also observed at the high field side(HFS) near both the lower and upper X-points with radiation loss suddenly increased to about 15%–70%,which may be the main cause of divertor plasma detachment.The temporary detachment induced by pellet injection may act as a new way to study divertor detachment behaviors.     

Simulation studies of tungsten impurity behaviors during neon impurity seeding with tungsten bundled charge state model using SOLPS-ITER on EAST

An investigation into tungsten (W) impurity behaviors with the update of the EAST lower W divertor for H-mode has been carried out using SOLPS-ITER. This work aims to study the effect of external neon (Ne) impurity seeding on W impurity sputtering with the bundled charge state model. As the Ne seeding rate increases, plasma parameters, W concentration (), and eroded W flux () at both targets are compared and analyzed between the highly resolved bundled model 'jett' and the full W charge state model. The results indicate that 'jett' can produce divertor behaviors essentially in agreement with the full W charge state model. The bundled scheme with high resolution in low W charge states (20+) has no obvious effect on the Ne impurity distribution and thus little effect on W sputtering by Ne. Meanwhile, parametric scans of radial particle and thermal transport diffusivities (and) in the SOL are simulated using the 'jett' bundled model. The results indicate that the transport diffusivity variations have significant influences on the divertor parameters, especially for W impurity sputtering.     

中国聚变工程实验堆雪花偏滤器脱靶运行的SOLPS模拟

在中国聚变工程实验堆(China Fusion Engineering Test Reactor,CFETR)的工程概念设计中,为探索有效降低偏滤器靶板热负荷的途径,相对于国际热核聚变实验堆(International Thermonuclear Experimental Reactor,ITER)特别增加了两个极向场线圈用于产生近年来新提出的雪花偏滤器位形。脱靶运行状态下,偏滤器靶板上的热负荷显著降低,但同时由于偏滤器温度的降低,杂质约束性能会变差,因此需要对CFETR雪花偏滤器的脱靶运行状态进行研究。基于边界等离子体物理模拟软件SOLPS(Scrape-off Layer Plasma Simulation),通过数值模拟研究了CFETR雪花偏滤器的脱靶运行状态。模拟中通过主等离子体室内的D2充气改变等离子体密度。当充气速度足够高时,CFETR雪花偏滤器实现完全脱靶,靶板上的离子流和热负荷都显著降低。但此时偏滤器区域等离子体温度已经非常低,杂质将容易通过X点进入芯部,有产生辐射不稳定性的风险。因此,对于CFETR雪花偏滤器较为合适的工作状态应当是部分脱靶运行。