共查询到20条相似文献,搜索用时 281 毫秒
1.
介绍了在HT-6M托卡马克上,利用双低杂波的组合,成功地实现了准稳态的高约束模式运行. 能量约束时间提高两倍以上,粒子的约束在较高密度下依然改善3倍以上.通过应用波扩散及 电流径向扩散方程计算低杂波电流传播的方法,对一组典型的数据进行数值模拟.计算表明 ,在HT-6M低杂波实验中,由于纵场较低,密度较高,低杂波的能量沉积在离磁轴较远的位 置,使等离子体电流密度分布成为反剪切位形,内部输运垒地形成,大大提高了等离子体的 约束状况.实验数据也给出了反剪切的证据.
关键词:
托卡马克
低杂波
约束改善 相似文献
2.
Hobirk J Wolf RC Gruber O Gude A Günter S Kurzan B Maraschek M McCarthy PJ Meister H Peeters AG Pereverzev GV Stober J Treutterer W;ASDEX Upgrade Team 《Physical review letters》2001,87(8):085002
In the ASDEX Upgrade tokamak, high poloidal beta up to beta(pol) = 3 at the Greenwald density with H-mode confinement has been reached. Because of the high beta, the plasma current is driven almost fully noninductively, consisting of 51% bootstrap and 43% neutral beam driven current. To reach these conditions the discharge is operated at low plasma current ( I(P) = 400 kA) and high neutral beam heating power ( P(NBI) = 10 MW). The discharge combines an edge (H mode) and internal transport barrier at high densities without confinement-limiting MHD activities. The extrapolation to higher plasma currents may offer a promising way for an advanced scenario based fusion reactor. 相似文献
3.
Mank G Messiaen AM Ongena J Unterberg B Dumortier P Finken KH Jaspers R Koslowski HR Kramer-Flecken A Rapp J Samm U van Wassenhove G Weynants RR 《Physical review letters》2000,85(11):2312-2315
Confinement quality as good as ELM-free H-mode at densities substantially above the Greenwald density limit ( &nmacr;(e,0)/n(GW) = 1.4) has been obtained in discharges with a radiative boundary under quasistationary conditions for 20 times the energy confinement time. This is achieved by optimizing the gas-fueling rate of RI-mode discharges which tailors their favorable energy confinement and leads to discharges with beta values just below the operational limit beta(n) = 2 of TEXTOR-94, thereby effectively avoiding confinement back transitions or disruptions. In addition, this high-density regime is favorable for helium removal and results in figures of merit tau(*)(p,He)/tau(E) approximately 10-15, relevant for a future fusion power reactor. 相似文献
4.
Shiraiwa S Ide S Itoh S Mitarai O Naito O Ozeki T Sakamoto Y Suzuki T Takase Y Tanaka S Taniguchi T Aramasu M Fujita T Fukuda T Gao X Gryaznevich M Hanada K Jotaki E Kamada Y Maekawa T Miura Y Nakamura K Nishi T Tanaka H Ushigusa K;JT- Team 《Physical review letters》2004,92(3):035001
A new operational scenario of advanced tokamak formation was demonstrated in the JT-60U tokamak. This was accomplished by electron cyclotron and lower hybrid waves, neutral beam injection, and the loop voltage supplied by the vertical field and shaping coils. The Ohmic heating (OH) solenoid was not used but a small inboard coil (part of the shaping coil), providing less than 20% of total poloidal flux, was used. The plasma thus obtained had both internal and edge transport barriers, with an energy confinement time of 1.6 times H-mode scaling, a poloidal beta of 3.6, and a normalized beta of 1.6, and a large bootstrap current fraction (>90%). This result opens up a possibility to reduce, and eventually eliminate, the OH solenoid from a tokamak reactor, which will greatly improve its economic competitiveness. 相似文献
5.
利用Harris模型,通过求解等离子体平衡方程,计算俘获粒子份额,分别对常规剪切和中心负剪切下tokamak中的自举电流的大小和剖面准直性进行了计算和分析.自举电流分布与等离子体平衡电流分布之间的剖面准直性可以通过调整等离子体的密度、温度和电流分布参数,以及描述等离子体形状的拉长度k和三角变形因子d来获得.中心负剪切位形有利于自举电流产生,并有好的剖面准直性.通过计算比较,分别在常规剪切位形下和中心负剪切位形下获得了一组优化的等离子体参数,在这组参数下,自举电流有较大的份额和好的剖面准直性
关键词:
tokamak
自举电流
剖面准直性 相似文献
6.
H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range. These H-mode discharges are characterized by a sudden drop in Dα emission and a spontaneous rise in main plasma density. Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D2 gas from a pipe near the grill mouse. The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode, and current drive (CD) efficiency decreases due to the increase in density. Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported. 相似文献
7.
在给定等离子体密度分布下,从电子、离子的能量方程出发,根据不同运行模式下等离子体的热传导率不同,分别求出了中心负剪切模式,常规剪切H模式和L模式下的等离子体温度分布,然后通过求解波迹方程与相对论情况下的Fokker-Planck方程,分别计算了这些模式下的电子回旋波电流驱动和波功率沉积.得到在中心负剪切下,驱动电流最大,驱动效率最高,功率沉积和电流分布区间跨度大;在常规剪切H模式下,驱动电流较小,分布区间跨度比较窄,驱动效率相对较低;在常规剪切L模式,驱动电流效率最低,分布区间跨度也非常集中.
关键词:
托卡马克
电子回旋波电流驱动
中心负剪切
常规剪切 相似文献
8.
Shvyd'ko YV Lerche M Jäschke J Lucht M Gerdau E Gerken M Rüter HD Wille HC Becker P Alp EE Sturhahn W Sutter J Toellner TS 《Physical review letters》2000,85(3):495-498
H-mode operation has been achieved in high current (I(p)>200 kA) plasmas in the START spherical tokamak for both neutral-beam-injection-heated and Ohmic discharges. The transition to H mode features the development of well-defined edge pedestals in density and temperature, which signifies the formation of an edge-transport barrier, and associated edge-localized modes. Recent operation at plasma currents exceeding 250 kA shows that these features are accompanied by increases in energy confinement time. This is the first clear demonstration of the H-mode regime in a spherical tokamak. 相似文献
9.
Pietrzyk ZA Angioni C Behn R Coda S Goodman TP Henderson MA Hofmann F Sauter O 《Physical review letters》2001,86(8):1530-1533
Current profile tailoring by electron cyclotron heating (ECH) and current drive (ECCD) is used to improve central electron energy confinement in the TCV tokamak. Counter-ECCD on axis alone achieves this goal in a transient manner only. A stable scenario is obtained by a two-step sequence of off-axis ECH, which stabilizes magnetohydrodynamics modes, and on-axis counter-ECCD, which generates a flat or inverted current profile. This high-confinement regime, with central temperatures up to 9 keV (at a normalized beta(N) approximately 0.6), has been sustained for the entire duration of the heating pulse, or over 200 electron energy confinement times and 5 current redistribution times. 相似文献
10.
以平衡程序Jsolver 为基础开展了紧凑型聚变裂变混合堆先进等离子体平衡位形设计,重点研究了反剪切运行模式,并在此位形下研究了自举电流的计算、分布及份额。 相似文献
11.
以平衡程序Jsolver 为基础开展了紧凑型聚变裂变混合堆先进等离子体平衡位形设计,重点研究了反剪切运行模式,并在此位形下研究了自举电流的计算、分布及份额。 相似文献
12.
本文对环径比为2(A=2)的托卡马克反应堆中氘氚燃烧等离子体的特性,利用一类简单的平衡位形,即Solov’ev位形,进行了研究。作为基准,采用了Troyon比压极限和Greenwald密度极限,以及 ITER的H-模约束定标关系。我们发现,除了增大拉长比外,大的三角变形也有利于提高比压值及获得高的聚变功率输出。与 ITER设计相比,对相同的总等离子体电流而言,A=2的反应堆因边缘安全因子很大,具有可以避免破裂不稳定性的优点。由于减小环径比时环内侧的可利用空间相应减小,这类反应堆的一个主要缺点是环向磁场强度也会减小,从而降低聚变堆品质。实际研究工作中要对这些方面做出某种折衷。另外,虽然由于我们采用了简单的位形,我们不能对自举电流的准直性进行优化,但是通过本研究仍然可以对中等环径比反应堆系统(目前是研究工作的空白)的特点获得了解。 相似文献
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14.
HT-6M托卡马克通过边界欧姆加热实现了改善约束的H模,利用中性粒子测量方法成功地研究了等离子体H模放电的中性粒子变化.观察到边界欧姆加热H模放电期间从等离子体逃逸的中性粒子比纯欧姆加热明显减少;约束改善后等离子体中心热区的中性原子密度下降,得到了反映等离子体约束改善的中性粒子特征.实验结果与其他诊断进行了比较和讨论
关键词: 相似文献
15.
Terranova D Alfier A Bonomo F Franz P Innocente P Pasqualotto R 《Physical review letters》2007,99(9):095001
Enhanced confinement regimes with quasihelical symmetry are reproducibly obtained in the modified reversed field pinch eXperiment (RFX)-mod by reducing the level of internal chaos through the combination of a smooth magnetic boundary (through a virtual shell scheme) and the oscillating poloidal current drive technique. The plasma moves from a chaotic multiple helicity towards a quasi-single-helicity regime with a magnetic island showing high temperature and soft x-ray emissivity. The chaos reduction involves also the plasma outside the island allowing for a global enhanced confinement with an improvement up to 50%. 相似文献
16.
研究了在托卡马克装置中中性束注入时快离子自举电流的产生。利用快离子分布函数在两小增量δ=ρp/a (ρp是极向拉莫尔半径,a是小半径)和δ*=τB/τs(τB是俘获粒子反弹周期,τs是慢化时间)下进行展开的方法求解漂移动力学方程;给出了快离子自举电流的一般表达式。计算了圆截面大纵横比托卡马克中快离子自举电流密度分布和总的快离子自举电流的大小,研究表明:在中性束垂直注入时快离子自举电流约占总电流10%;自举电流的大小既敏感地依赖于中性束注入的角度——平行注入时较小、接近垂直时迅速增大,同时也较强的依赖于快离子的产生速度与临界速度的比值,即vb/vc,而vb2∝E(束能量);自举电流的大小随注入束能量的增加而迅速增大。 相似文献
17.
Conway GD Angioni C Ryter F Sauter P Vicente J;ASDEX Upgrade Team 《Physical review letters》2011,106(6):065001
A complex interaction between turbulence driven E × B zonal flow oscillations, i.e., geodesic acoustic modes (GAMs), the turbulence, and mean equilibrium flows is observed during the low to high (L-H) plasma confinement mode transition in the ASDEX Upgrade tokamak. Below the L-H threshold at low densities a limit-cycle oscillation forms with competition between the turbulence level and the GAM flow shearing. At higher densities the cycle is diminished, while in the H mode the cycle duration becomes too short to sustain the GAM, which is replaced by large amplitude broadband flow perturbations. Initially GAM amplitude increases as the H-mode transition is approached, but is then suppressed in the H mode by enhanced mean flow shear. 相似文献
18.
19.
Increased nonlinear coupling between turbulence and low-frequency fluctuations at the L-H transition
The nonlinear coupling between small scale high-frequency turbulence and larger scale lower-frequency fluctuations increases transiently in transitions to improved confinement in the DIII-D tokamak. This increase starts before the rapid turbulence suppression and E x B shear-flow development in the region that becomes the H-mode transport barrier/shear flow region. After the transition, the coupling returns to L-mode levels. These results are consistent with expectations for spontaneous transitions to improved confinement triggered by a turbulence-driven sheared flow. 相似文献
20.
Kiptily VG Baranov YF Barnsley R Bertalot L Hawkes NC Murari A Popovichev S Sharapov SE Stork D Yavorskij V 《Physical review letters》2004,93(11):115001
Gamma-ray spectra from nuclear reactions between fusion-born alpha (alpha) particles and Be impurities were measured for the first time in deuterium-tritium plasmas in the Joint European Torus. The time dependence of the measured spectra allowed the determination of the density evolution of fast alpha particles. Correlation between the decay time of the gamma-ray emission and the plasma parameters in different plasma scenarios was established. Results are consistent with classical slowing down of the alpha particles in discharges with high plasma currents and monotonic q-profiles. In low plasma current discharges and in the discharges with large on-axis current holes (extreme reversal central magnetic shear), the gamma-ray emission decay times are shorter than the classical slowing down times, indicating an alpha-particle confinement degradation in such discharges in line with theoretical predictions. 相似文献