Propagation of Electrostatic Waves near the Lower Hybrid Frequency in a Toroidal Plasma, NOVA-I

Resonance cones in a lower hybrid range of frequency are observed and confirmed under the combined influence of toroidicity and inhomogenity in a toroidal device NOVA-I. The resonance cone is investigated in two different plasma sources, i.e. (A) a steady plasma of low density (Nₑ, ～5×10⁹ cm⁻³), and (B) a pulsed tokamak plasma of high density (Nₑ～2×10¹³ cm⁻³). In case (A), the experimental results agree well with the trajectories computed from a simple cold plasma dispersion relation. Even in the high density tokamak plasma of case (B), a wave penetration toward the plasma center is observed and its behavior also agrees qualitatively with the thoery

A Small Tokamak “NOVA II”

A small tokamak, NOVA II, has been designed and constructed. The major radius is 30 cm, the minor radius 6 cm and the maximum toroidal field 15 kG. The device has a removable shell assembly for studying the stabilizing effect of a conductive shell. The basic concept of design and the specifications of the principal components are described. In preliminary experiments, stable discharge was maintained for 15 msec or longer. The electron temperatures measured by diamagnetism and conductivity are both above 100 eV. An electron density of 1-2×10¹³ cm⁻³ was observed by a 6 mm microwave interferometer. Spectroscopy of impurity lines and intensity measurement of hard X-ray radiation are also described

Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak

A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E × B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed

多階層複雑・開放系における粒子循環の物理とマクロ制御

Fusion reactor research and development via a half-century has progressed to a validation of engineering and physics of nuclear burning as a source of energy generation through the construction of ITER. Although "steady state operation (SSO)" is an indispensable prerequisite for a reactor, the immediate goal of ITER is 400 seconds. In SSO the circulation control of the fuel particles will be the subject of challenging studies due to plasma wall interaction, though it is not a problem in pulsed operation. The present study is aimed at clarifying the particle circulation in three systems, core, boundary, and first wall. Elementary processes, the system interaction, a circulation model, and control of the particle circulation, are subjects to build the foundation for SSO. For this study the viewpoint of "Physics and macro control of particle circulation in a multi hierarchical complex-open system" is introduced. The elucidation of the circulation in each system and the mutual interference leads to the key macro control of the whole system

First Wall Particle Flux Measurements by an F82H Permeation Probe in QUEST

First wall particle flux measurements in the QUEST spherical tokamak have been conducted, using a permeation probe that employs a first wall candidate ferritic steel alloy F82H as the membrane and also SUS304 as a comparative reference membrane. Permeation measurements have been done during the conditioning steady-state discharges heated with 2.45 GHz and 8.2 GHz ECR. Diffusion and recombination coefficients measured in a laboratory-scale plasma device: VEHICLE-1 are used to interpret the results from the permeation probe measurements in QUEST. These permeation membranes have been analyzed with XPS to evaluate the effects of surface impurities

Characteristic of a pdCu membrane as atomic hydrogen probe for QUEST

A permeation probe is a useful device for detecting the atomic hydrogen flux to plasma-facing walls. Recently, we developed a new type of probe using 60Pd-40Cu alloy (PdCu) as the permeation material. The deuterium behaviors in PdCu samples were investigated using nuclear reaction analysis (NRA) and permeation observations, and the diffusion coefficient and recombination coefficients were determined from these observations. It was found that the sensitivity of a 0.02-mm-thick probe was as high as 0.5 below 473K and was independent of the incident flux. The response time at 473K was 0.41s and 1.3s under an incident flux of 1020m−2s−1 and 1019m−2s−1, respectively. Thus, we concluded that the new PdCu probe can effectively detect the incident atomic hydrogen with high sensitivity and a suitable response time

First Wall Particle Flux Measurements by an F82H Permeation Probe in QUEST

0000-0001-9773-8121First wall particle flux measurements in the QUEST spherical tokamak have been conducted, using a permeation probe that employs a first wall candidate ferritic steel alloy F82H as the membrane and also SUS304 as a comparative reference membrane. Permeation measurements have been done during the conditioning steady-state discharges heated with 2.45 GHz and 8.2 GHz ECR. Diffusion and recombination coefficients measured in a laboratory-scale plasma device: VEHICLE-1 are used to interpret the results from the permeation probe measurements in QUEST. These permeation membranes have been analyzed with XPS to evaluate the effects of surface impurities