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Numerical study of fast ion behavior in the presence of magnetic islands and toroidal field ripple in the EAST tokamak

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Chinese Physics B 2014年第10期23卷 334-341页

作者：张伟胡立群孙有文丁斯晔张子君刘松林 Institute of Plasma Physics Chinese Academy of Sciences

A peculiar first orbit loss type was found apart from the normal ones when we use ORBIT code to simulate fast ion orbits in the EAST tokamak. Fast ion orbits were studied in the presence of toroidal field （TF） ripple and magnetohydro- dynamic （MHD） perturbations. We analyzed the properties of the drifted orbits in detail and compared their differences, finding that the combined effects of ripple and magnetic islands are much greater than the effects of either one of them alone. Then we investigated the orbitdeviations as a function of pitch angle in different radial positions. The modeling results demonstrate that the loss of trapped particles is mainly caused by the ripple, while MHD＇perturbation mainly plays an important role in the passing particles. Furthermore we modeled the loss rate using different equilibriums. Results prove that a higher beta can indeed improve the confinement of fast ions, while a little change in the q profile can make the topologies of magnetic islands become quite different and results in quite different total particle losses.

关键词： fast ion toroidal field ripple magnetic island orbit drift

Observation of Impurity Accumulation After Hydrogen Multi-Pellet Injection in Large Helical Device

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Plasma Science and Technology 2013年第3期15卷 230-234页

作者：董春凤 Shigeru MORITA Motoshi GOTO 王二辉 Gen MOTOJIAMA Izumi MURAKAMI Ryuichi SAKAMOTO Norimasa YAMAMOTO National Institute for Fusion Science Department of Fusion Science Graduate University for Advanced Studies Center of Applied Superconductivity & Sustainable Energy Research Chubu University

Impurity accumulation is studied for neutral beam-heated discharges after hydrogen multi-pellet injection in Large Helical Device （LHD）. Iron density profiles are derived from radial profiles of EUV line emissions of FeXV-XXIV with the help of the collisional-radiative model. A peaked density profile of Fe2a＋ is simulated by using one-dimensional impurity transport code. The result indicates a large inward velocity of -6 m/s at the impurity accumulation phase. However, the discharge is not entirely affected by the impurity accumulation, since the concentration of iron impurity, estimated to be 3.3x10-5 to the electron density, is considerably small. On the other hand, a flat profile is observed for the carbon density of C6＋, which is derived from the Zeff profile, indicating a small inward velocity of -1 m/s. These results suggest atomic number dependence in the impurity accumulation of LHD, which is similar to the tokamak result.

关键词： impurity accumulation EUV spectrometer inward velocity

Minimum length key in MST cryptosystems

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Science China(Information Sciences) 2017年第5期60卷 142-152页

作者： Haibo HONG Licheng WANG Haseeb AHMAD Yixian YANG Zhiguo QU School of Computer Science and Information Engineering Zhejiang Gongshang University Information Security Center State Key Laboratory of Networking and Switching TechnologyBeijing University of Posts and Telecommunications Jiangsu Engineering Center of Network Monitoring Nanjing University of Information Science & Technology

As a special factorization category of finite groups, logarithmic signature(LS) is used as the main component of cryptographic keys that operate within secret key cryptosystems such as PGM and public key cryptosystems like M ST1, M ST2 and M ST3. An LS with the shortest length is called a minimal logarithmic signature(MLS) that constitutes of the smallest sized blocks and offers the lowest complexity, and is therefore desirable for cryptographic constructions. However, the existence of MLSs for finite groups should be firstly taken into an account. The MLS conjecture states that every finite simple group has an MLS. If it holds, then by the consequence of Jordan-H¨older Theorem, every finite group would have an MLS. In fact, many cryptographers and mathematicians are keen for solving this problem. Some effective work has already been done in search of MLSs for finite groups. Recently, we have made some progress towards searching a minimal length key for MST cryptosystems and presented a theoretical proof of MLS conjecture.

关键词： MLS conjecture finite groups (minimal) logarithmic signature minimum length key MST cryp tosystems

Space-Resolved VUV and EUV Spectrometers in HL-2A

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Plasma Science and Technology 2013年第2期15卷 110-114页

作者：崔正英周航宇 S.MORITA 傅炳忠孙平高亚东 M.GOTO 徐媛董春凤杨青巍 Southwestern Institute of Physics Chengdu 610041 China National Institute for Fusion Science Toki 509-5292 Gifu Japan

A normal incidence vacuum ultraviolet （VUV） and a grazing incidence extreme ultraviolet （EUV） spectrometers have been developed for the edge and core impurity measure- ments in HL-2A tokamak. The VUV and the EUV spectrometers cover wavelength ranges of 300-3200 A and 50-500A, respectively. A spatial resolution of 2 mm has been achieved for the VUV spectrometer when a space-resolved slit 50 #m in width is used. The space-resolved slit is placed between the entrance slit and the grating of the spectrometer. The spectral resolutions of 0.15/~ for the VUV spectrometer in the wavelength coverage of the concave 1200 grooves/mm grating and of 0.22A for the EUV spectrometer at λ=200A with a flat-field laminar-type holo- graphic grating are obtained. The sensitivity of the VUV spectrometer was calibrated in situ with the plasma bremsstrahlung radiation. The experimental results from both spectrometers are presented, especially the line intensity radial profiles measured by the VUV spectrometer.

关键词： VUV spectra EUV spectra spectrometer spatial resolution

Results of ICRF Heating Experiments from the EAST 2010 Campaign

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Plasma Science and Technology 2015年第3期17卷 188-190页

作者：何钟鑫张新军赵燕平 Institute of Plasma Physics Chinese Academy of Sciences

Radio frequency （RF） plasma heating in ion cyclotron range of frequencies （ICRF） was successfully performed on the Experimental Advanced Superconducting Tokamak （EAST）. This is mainly because lithium wall conditioning was routinely used to reduce both impurity and hydrogen （H） recycling and to improve the ICRF power absorption. Mainly ICRF heating of the H minority regime at 27 MHz has been applied in deuterium plasmas. The ion cyclotron resonance heating （ICRH） is found to depend strongly on plasma preheating. The ICRH efficiency can be much improved in conjunction with the lower hybrid wave （LHW）. Effective ion and electron heating was observed with the H minority heating mode. The increase of the stored energy reached 30 kJ in L-mode plasma by using the ICRF power of 1.0 MW alone when the H cyclotron resonance layer was at plasma center.

关键词： ICRF minority heating EAST

The role of shrub(Potentilla fruticosa)on ecosystem CO_(2) fluxes in an alpine shrub meadow

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Journal of Plant Ecology 2010年第2期3卷 89-97页

作者： Yuichiro Yashiro Yoko Shizu Mitsuru Hirota Ayako Shimono Toshiyuki Ohtsuka River Basin Research Center Gifu University1-1 YanagidoGifuGifu 501-1193Japan Graduate School of Life and Environmental Science University of Tsukuba1-1-1 TennodaiIbaraki 305-8521Japan Department of Ecology and Environmental Science Umea UniversityUmea 901-87Sweden

Aims Recent studies have shown that alpine meadows on the Qinghai-Tibetan plateau act as significant CO_(2)*** the plateau,alpine shrub meadow is one of typical grassland *** major alpine shrub on the plateau is Potentilla fruticosa L.(Rosaceae),which is distributed widely from 3200 to 4000 *** species play an important role on carbon sequestration in grassland *** addition,alpine shrubs are sensitive to climate change such as global *** global warming,the biomass and productivity of *** will increase on Qinghai-Tibetan ***,understanding the carbon dynamics in alpine shrub meadow and the role of shrubs around the upper distribution limit at present is essential to predict the change in carbon sequestration on the ***,the role of shrubs on the carbon dynamics in alpine shrub meadow remains *** objectives of the present study were to evaluate the magnitude of CO_(2)exchange of *** shrub patches around the upper distribution limit and to elucidate the role of *** on ecosystem CO_(2)fluxes in an alpine *** We used the static acrylic chamber technique to measure and estimate the net ecosystem productivity(NEP),ecosystem respiration(Re),and gross primary productivity(GPP)of *** shrub patches at three elevations around the species’upper distribution *** CO_(2)fluxes and environmental factors were measured from 17 to 20 July 2008 at 3400,3600,and 3800 m *** examined the maximum GPP at infinite light(GPPmax)and maximum Re(Remax)during the experimental time at each elevation in relation to aboveground biomass and environmental factors,including air and soil temperature,and soil water *** Findings Patches of *** around the species’upper distribution limit absorbed CO_(2),at least during the *** NEP at infinite light(NEPmax)and GPPmax of shrub patches in the alpine meadow varied among the three elevations,with t

关键词： alpine meadow ecosystem respiration gross primary productivity net ecosystem productivity Potentilla fruticosa shrub patch

Observation of the Two-Dimensional Distribution of Impurity Line Emissions Using a Space-Resolved EUV Spectrometer in LHD

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Plasma Science and Technology 2013年第2期15卷 106-109页

作者：王二辉 S.MORITA M.GOTO 董春凤 Department of Fusion Science Graduate University for Advanced StudiesToki 509-5292Gifu Japan National Institute for Fusion Science Toki 509-5292 Gifu Japan

A space-resolved EUV spectrometer for measuring the one-dimensional distribution of impurity line emissions in Large Helical Device （LHD） has been upgraded to measure two- dimensional distributions of impurity line emissions with an extension of working wavelength range to 30-650% The two-dimensional measurement is performed by scanning the observation chord horizontally. A rectangular plasma region of 520 × 700 mm2 in vertical and horizontal sizes can be observed during a single horizontal scan. The horizontal scan requires a time duration of 5 s at least. The spatial resolution is 10 mm in the vertical direction when a spatial-resolution slit of 0.2 mm in width is adopted. Although a spatial resolution in the toroidal direction is 75 mm, it is a function of CCD exposure time and horizontal scanning speed. Two-dimensional distribution of EUV line emissions from several impurities has been successfully observed for the first time from steady discharges in LHD. In this paper two-dimensional distributions of He II （303.78A）, C V （40.27A）, C VI （33.73A） and Fe XX （132.85A） located at different radial positions are presented with simple analysis on the magnetic field structure of LHD.

关键词： EUV spectrometer impurity line emission two-dimensional distribution

Observation of MHD Instabilities Driven by Energetic Electrons in the Large Helical Device

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Plasma Science and Technology 2015年第4期17卷 276-279页

作者： Mitsutaka ISOBE Kunihiro OGAWA Akihiro SHIMIZU Masaki OSAKABE Shin KUBO K.TOI the LHD Experiment Group National Institute for Fusion Science Toki 509-5292Japan Department of Fusion Science The Graduate University for Advanced Studies(SOKENDAI)Toki 509-5292Japan Department of Energy Engineering and Science Nagoya UniversityNagoya 464-8463Japan

Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density（n_e〈0.2×10^（19）m^（-3））plasmas with strong second harmonic electron cyclotron resonance heating（ECRH）on the Large Helical *** X-ray measurements indicated that energetic electrons are generated in these ECRH *** magnetic fluctuations are suppressed in higher density discharges where energetic electrons are not *** ECRH power modulation experiment indicated that the observed magnetohydrodynamic（MHD）mode has an acoustic nature rather than an Alfvenic nature.

关键词： LHD ECRH energetic electron MHD instability

Estimate of the Deposition Profile of Carbon Pellets Using a High-Speed VUV Imaging System in the LHD

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Plasma Science and Technology 2013年第12期15卷 1178-1183页

作者：明廷凤 Satoshi OHDACHI Yasuhiro SUZUKI LHD Experiment Group The Graduate University for Advanced Studies 322-60roshi-cho Toki 509-5292 Japan National Institute for Fusion Science 322-60roshi-cho Toki 509-5292 Japan

The deposition profile of the impurity pellet is measured by a two-dimensional fast- framing vacuum ultraviolet （VUV） camera system in the large helical device （LHD）. The fast framing camera selectively measures the emission from the hydrogen-like ions of carbon （C VI） with a frame rate of several kHz. From the emission profile of the hydrogen-like carbon ions, which are in the process of ionization, the initial deposition profile of the carbon is estimated using a simple one-dimensional transport model.

关键词： VUV impurity transport carbon pellet injection LHD