Transition between internal transport barriers with different temperature-profile curvatures in JT-60U Tokamak plasmas

A spontaneous transition phenomena between two states of a plasma with an internal transport barrier (ITB) is observed in the steady-state phase of the magnetic shear in the negative magnetic shear plasma in the JT-60U tokamak. These two ITB states are characterized by different profiles of the second radial derivative of the ion temperature inside the ITB region (one has a weak concave shape and the other has a strong convex shape) and by different degrees of sharpness of the interfaces between the L mode and the ITB region, which is determined by the turbulence penetration into the ITB region.     

Evolution of the current density profile associated with magnetic island formation in JT-60U

Evolution of the current density profile associated with magnetic island formation of an m/n=2/1 tearing mode was measured using a motional Stark effect (MSE) diagnostic for the first time in the JT-60U tokamak. With the island growth, the current density profile turned flat at the radial region of the island, followed by an appearance of a hollow structure. As the island shrank, the flat region became narrower, and it finally diminished after the disappearance of the island. The fluctuation of the local poloidal magnetic field from MSE showed a strong correlation with a slow island rotation. This indicates that the observed deformation in the current density profile is localized at the island O point.     

JT-60U装置温度分布剖面不变性的实验研究

在一系列H模放电条件下，建立了一个旨在研究等离子体温度分布剖面不变性的数据库。介绍了数据库建立过程中要解决的关键问题和所用软件，对等离子体温度分布剖面不变性及芯部约束与边缘参数的关系进行了研究。     

Quasisteady high-confinement reversed shear plasma with large bootstrap current fraction under full noninductive current drive condition in JT-60U

A quasisteady reversed shear plasma with a large bootstrap current fraction ( approximately 80%) has been obtained for the first time in the JT-60U tokamak. The shrinkage of reversed shear region was suppressed by the bootstrap current peaked at the internal transport barrier (ITB) layer and the ITBs at a large radius were sustained, which, by combination with an H-mode edge pedestal, resulted in a high confinement or 2.2 times the H-mode scaling for 6 times energy confinement time or 2.7 s. Furthermore, a full noninductive current drive was obtained by the bootstrap current and the beam driven current.     

Modification to poloidal charge exchange recombination spectroscopy measurement in JT-60U tokamak

With consideration of the effects of the atomic process and the sight line direction on the charge exchange re-combination spectroscopy （CXRS）, a code used to modify the poloidal CXRS measurement on Tokamak-60 Upgrade （JT-60U） in Japan Atomic Energy Research Institute is developed, offering an effective tool to modify the measurement and analyse experimental results further. The results show that the poloidal velocity of ion is overestimated but the ion temperature is underestimated by the poloidal CXRS measurement, and they also indicate that the effect of observation angle on rotation velocity is a dominant one in a core region （r/a 〈 0.65）, whereas in an edge region where the sight line is nearly normal to the neutral beam, the observation angle effect is very small. The difference between the modified velocity and the neoclassical velocity is not larger than the error in measurement. The difference inside the internal transport barrier （ITB） region is 2-3 times larger than that outside the ITB region, and it increases when the effect of excited components in neutral beam is taken into account. The radial electric field profile is affected greatly by the poloidal rotation term, which possibly indicates the correlation between the poloidal rotation and the transport barrier formation.[第一段]     

First EMC3-EIRENE modelling of JT-60SA edge plasmas with/without resonant magnetic perturbation field

The first EMC3-EIRENE modelling for the JT-60SA edge plasmas with/without the resonant magnetic perturbation field (RMP) was conducted. Both core degradation in the vacuum approximation and strike-point splitting were observed due to the application of the RMP, as in previous studies in other devices. Toroidally averaged divertor heat fluxes with and without the RMP were fitted by using a one-dimensional diffusive model function, showing similar profiles. To extract the modulation components of the divertor heat flux profile, the proper orthogonal decomposition (POD) method was applied. By using the POD outputs, a modulation ratio with respect to the toroidally averaged profile was quantitatively calculated.     

Measurement of natural plasma flow along the field lines in the scrape-Off layer on the JT-60U divertor tokamak

The plasma profile and parallel plasma flow in the scrape-off layer (SOL) were systematically measured using reciprocating Mach probes installed at the outer midplane and near the divertor magnetic null (x point) in the JT-60U tokamak with a single null divertor. For the ion vertical drift due to the toroidal magnetic field gradient (ion nablaB drift) directed towards the divertor, SOL plasma flow along the magnetic field lines away from the divertor ("flow reversal") was discovered at the midplane far from the divertor. A quantitative evaluation of the ion "Pfirsch-Schluter flow," wherein the parallel flow is naturally produced in a toroidal plasma, was consistent with the measurement.     

Hypergeometric solutions of the qKZ equation at level zero

We discuss relations between different integral formulae for solutions of the quantized Knizhnik-Zamolodchikov (qKZ) equation at level zero in the U_q ( ₂) case for q < 1. Smirnov type formulae of M. Jimbo et al. are derived from the general approach of A. Varchenko and the author. The consideration is parallel to the qKZ equation in the rational ₂ case done by A. Nakayashiki, S. Pakuliak and the author.     

高气压均匀直流辉光放电等离子体的光学特性

在高气压(大于100 Torr, 1 Torr=1.33322×10² Pa)平板位形的均匀直流辉光放电中, 一定条件下观察到平行排列的明暗相间的等离子体辉纹. 结合等离子体的光发射谱诊断, 研究了气体组分对等离子体光学特性的影响. 研究发现, 随着甲烷浓度的增加, 辉纹间距减小, 相应的电子激发温度降低. 当甲烷浓度增加时, 等离子体中低电离能的粒种增加, 粒子平均电离能减小, 这种情况下, 电子被电场加速较短的距离所获得的能量就可以激发粒子, 产生可见的光发射, 表现为辉纹间距缩短. 随着氩气的引入, 能够观察到明显的辉纹, 且增大氩气含量, 辉纹间距增加, 这与氩的较高电离能有关, 而相应的电子激发温度增加. 研究结果表明, 随着工作气体的改变, 等离子体辉纹间距呈现出一种对电子温度的响应.     

托卡马克等离子体中的电子回旋波电流驱动

通过将波迹方程与相对论情况下的完全Fokker-Planck方程联合进行求解,研究了寻常波基频电子回旋波从托卡马克等离子体中平面弱场侧发射时的电流驱动。数值结果表明:随着等离子体电子密度、温度的提高, 功率沉积和电流分布的位置将向等离子体的边缘方向偏移,并且产生的总的驱动电流随之减小;入射波极向发射角和环向发射角度的改变对功率沉积、电流分布及其大小产生明显的影响。     

The odd-parity level at 687.59 keV in236U

The spin-parity of the 687.59 keV level in²³⁶U populated in the decay of²³⁶Np is determined to be 2^? in disagreement with recent 1^? assignments from reaction data, but in accordance with previous radioactive²³⁶Np decay studies. The 687 keV ground state transition is shown to have a pureM2 character. The 642 keV 2^?→2⁺ transition hasE1:M2:E3 mixing ratios of 64∶30∶6. The half-life of the 2^? state is 3.78 ± 0.09 ns. The hindrance factor of the E1-part fits an E1 transition withΔK=2, theM2-part has the same transition rate as the M2 transitions in the neighbouring²³⁷Np nucleus and the E3-part is enhanced by two orders of magnitude relative to the Weisskopf estimate. The data are compared to analogous transitions in the rare earth region.     

Highly resolved fluid flows: "liquid plasmas" at the kinetic level

Fluid flow around an obstacle was observed at the kinetic (individual particle) level using "complex (dusty) plasmas" in their liquid state. These "liquid plasmas" have bulk properties similar to water (e.g., viscosity), and a comparison in terms of similarity parameters suggests that they can provide a unique tool to model classical fluids. This allows us to study "nanofluidics" at the most elementary-the particle-level, including the transition from fluid behavior to purely kinetic transport. In this (first) experimental investigation we describe the kinetic flow topology, discuss our observations in terms of fluid theories, and follow this up with numerical simulations.     

Inversion of hydrogen level populations in stationary plasmas

Large inversions in the dense two-temperature hydrogen plasma are obtained by solving balance equations with inelastic collisions between heavy particles taken into account.     

0.7 Structure and zero bias anomaly in ballistic hole quantum wires

We study the anomalous conductance plateau around G=0.7(2e2/h) and the zero bias anomaly in ballistic hole quantum wires with respect to in-plane magnetic fields applied parallel B parallel and perpendicular B perpendicular to the quantum wire. As seen in electron quantum wires, the magnetic fields shift the 0.7 structure down to G=0.5(2e2/h) and simultaneously quench the zero bias anomaly. However, these effects are strongly dependent on the orientation of the magnetic field, owing to the highly anisotropic effective Landé g-factor g* in hole quantum wires. Our results highlight the fundamental role that spin plays in both the 0.7 structure and zero bias anomaly.