Diagnostics for first plasma study on EAST tokamak

The first plasma was obtained in the EAST on September 26th, 2006. Single-null (SN) and double-null (DN) diverted plasmas were achieved successfully in the EAST tokamak on January 22nd, 2007. The employed plasma diagnostics for first plasma study of EAST are as follows: a vertical one-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer for measuring the line average density, a 10-channel soft X-ray array for intensity measurement, a 16-channel heterodyne Electron Cyclotron Emission (ECE) for measuring the electron temperature profile, a 8-channel XUV bolometer array to measure plasma radiation losses, a 3-channel hard X-ray array for intensity measurement, an electromagnetic measurement system, a 35-channel Hα radiation array, 20 probes for divertor plasma, a one-channel visible bremsstrahlung emission, an impurity optical spectrum measurement system and two optical spectroscopic multi-channel analyzers (OMA). The first experimental results of diagnostic systems are summarized in this Letter.     

Simulations of filamentary structure in an edge-localized mode burst on EAST using BOUT++ code

In this paper, simulation on the filamentary structure for the low-hybrid wave heating H-mode on experimental advanced superconducting tokamak (EAST) is carried out for the first time using BOUT++, and the speed and width of edge localized mode (ELM) filaments have been evaluated during the simulation. The evolutions of the ELM filaments are illustrated temporally and spatially. Then the results are compared with the experimental observations. It is found that at the peak gradient region in the outer midplane, the radial speed of the filaments is changed frequently and varied from 0.016 to 0.38 km/s. For the contrast, the poloidal speed oscillates in a narrower range of 0.68–0.88 km/s. The calculation results show the width of ELM filaments oscillates during the simulation, the minimum width is around 8.3 mm, and the maximum value is 41.24 mm. The distributions of the ELM filament widths with the radial position indicate the width is decreased with the radial position. Furthermore, by tracing one single filament, the radial width is decreased gradually when the filament is moving outward, which is also consistent with experiment conclusion. The consistencies also indicate the availability and practicability of the six-field two-fluid model of BOUT++ on the study of ELMs.     

MODELING THE SPATIAL DISTRIBUTION OF THE ECONOMIC COSTS AND BENEFITS OF ILLEGAL GAME MEAT HUNTING IN THE SERENGETI

ABSTRACT. Illegal game meat hunting in the Serengeti National Park, Tanzania, and adjacent game reserves provides an important source of protein and cash income to local communities. We construct a profitability model that describes the spatial distribution of the economic costs and benefits of illegal hunting in the Serengeti during the late 1980s and early 1990s. Costs included capital investment in hunting weapons, W_R, and the opportunity cost of hunting, W_O, both held to be constants; and two spatially variable components, the logistic effort of traveling to hunting areas, W_L, and the penalties incurred if arrested, W_P. Benefit was the expected income from the sale of meat from resident wildlife species. The model suggests: (1) W_R is the most important cost. (2) W_L is the second most important cost and likely to determine the spatial distribution of hunting activity if hunters seekto minimize costs. (3) W_O and W_P are of minor importance, the former because alternative sources of income provide low pay, the latter because the overall chance of being arrested is low. (4) W_P exceeds W_L only in areas close to the boundary of protected areas. (5) Although resident wildlife contributes only a minor share of illegal offtake compared to the migratory herds, hunting resident wildlife is profitable in 68% of the area. This suggests that hunting of resident and migratory wildlife is highly profitable and may explain why the utilization of the target populations has become increasingly unsustainable.     

Predictions and observations of low-shear beta-induced shear Alfvén–acoustic eigenmodes in toroidal plasmas

New global MHD eigenmode solutions arising in gaps in the low frequency Alfvén–acoustic continuum below the geodesic acoustic mode (GAM) frequency have been found numerically and have been used to explain relatively low frequency experimental signals seen in NSTX and JET tokamaks. These global eigenmodes, referred to here as Beta-induced Alfvén–Acoustic Eigenmodes (BAAE), exist in the low magnetic safety factor region near the extrema of the Alfvén–acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes shifts as the safety factor, q  , decreases. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta <2%$<2\mathrm{\%}$ as well as in NSTX plasmas at relatively high-beta >20%$>20\mathrm{\%}$. In contrast to the mostly electrostatic character of GAMs the new global modes also contain an electromagnetic (magnetic field line bending) component due to the Alfvén coupling, leading to wave phase velocities along the field line that are large compared to the sonic speed. Qualitative agreement between theoretical predictions and observations are found.     

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介绍了EAST真空室内巡视系统(IVVS)系统对EAST真空室第一壁进行巡检操作的工作原理,并基于系统部分材料出气率测试对其真空性能进行了分析.获得了在有效抽速为1064L·s–1的条件下,IVVS系统试验样机所采用的真空容器的极限真空度为3.37×10–3Pa.为优化IVVS真空性能,结合材料放气率试验,将部分材料更换为放气率低的材料,对系统进行烘烤处理,并对其中的相关结构提出了优化方案.优化后系统的真空性能有明显提高,在同等抽速条件下的极限真空度在1×10–4Pa范围内,能够满足EAST接受的真空环境要求.此外,抽气机组增添低温泵可以更进一步提高系统的真空性能.     

Polyyne bending frequencies: why they vary with the square of the harmonic in the infinite limit

The vibrational frequencies of several linear polyynes HC _N H, HC _N I and IC _N I, for even-valued N up to 60, have been obtained using computational quantum chemistry. The bending normal modes have the appearance of classical transverse normal modes of a vibrating string fixed at both ends, for which the frequencies vary with the first power of the harmonic. Our calculations, however, reveal that in the limit of infinite chain length and infinite mass on the ends of the ‘molecular string’, the bending frequencies vary with the square of the harmonic, at all levels of theory. A derivation is presented to explain the discrepancy.     

EAST真空室内巡视系统的真空性能研究分析

介绍了EAST真空室内巡视系统(IVVS)系统对EAST真空室第一壁进行巡检操作的工作原理,并基于系统部分材料出气率测试对其真空性能进行了分析。获得了在有效抽速为1064L•s^–1的条件下,IVVS系统试验样机所采用的真空容器的极限真空度为3.37×10^–3Pa。为优化IVVS真空性能,结合材料放气率试验,将部分材料更换为放气率低的材料,对系统进行烘烤处理,并对其中的相关结构提出了优化方案。优化后系统的真空性能有明显提高,在同等抽速条件下的极限真空度在1×10^–4Pa范围内,能够满足EAST接受的真空环境要求。此外,抽气机组增添低温泵可以更进一步提高系统的真空性能。