Report of the Second Fusion Energy Sciences Committee of Visitors

This report summarizes the findings and recommendations of the second Committee of Visitors (COV) whose charge was to review the manner in which the U. S. Department of Energy’s Office of Fusion Energy Science (OFES) manages certain programs under its charter. The specific programs reviewed by this COV involve confinement innovation and basic plasma sciences. The charge letter from the Department of Energy is included as Appendix A.     

Plasma Flows within the Context of Biasing Experiments

The understanding and reduction of turbulent transport in magnetic confinement devices is not only an academic task, but also the matter of practical interest, since high confinement is chosen as the regime for ITER and possible future reactors it reduces both the size and the cost. Since the pioneering work on CCT a lot of work has been devoted to the effect of electric field biasing carried out on many tokamaks, which in general leads to a strongly varying radial electric fields as a function of radius and a resulting sheared E×B flow, giving rise to improved confinement properties.The issue of plasma flows is utterly fundamental for understanding of tokamaks aimed at the achievement of fusion energy. This appears in the well known neoclassical theory as the most accomplished and self-consistent basis for understanding of fusion plasmas. It pertains to the novel concept of "zonal flows" emerging from the recent development of gyro-kinetic transport codes. The poloidal and toroidal flows are also cruc     

球形环研究概述

球形环是一种先进的磁约束核聚变研究装置 ,它保留了传统托卡马克装置的许多特点 ,比如说封闭磁面系统 ,中等旋转变换磁力线和好的等离子体约束性能等 ,同时又有低环径比 ,低纵向磁场 ,从而具有结构紧凑 ,造价相对低廉等优点 ,是有潜力的磁约束核聚变途径之一。概述了球形环的装置、实验、理论等方面的研究现状和有待探索的问题     

Preliminary Results of Drift Instability by Fast Optical Images in KT-5D Toroidal Plasma

Drift instability in plasma generated by electron cyclotron resonance （ECR） in KT- 5D device was investigated by using a fast camera and Langmuir probes. The similarity between the distribution of light intensity from the images and the plasma pressure indicates a nearly linear relationship. The discharge images taken by the camera and the plasma parameters measured by the probes also indicate the existence of low frequency turbulent events with a time scale less than a few mini-seconds.     

Analysis of the Plasma Properties Affected by Magnetic Confinement with Special Emphasis on Helicon Discharges

A one-dimensional radial non-uniform fluid model is employed to study plasma behaviors with special emphasis laid on helicon discharges. The plasma density ne, electron temperature Te, electron azimuthal and radial drift velocities are investigated in terms of the plasma radius rp, magnetic field intensity B0 and gas pressure p0, by assuming radial ambipolar diffusion and negligible ion cyclotron movement. The results show that the magnetic confinement plays an important role in the discharge equilibrium, especially at low pressure, which significantly reduces Te compared with the case of a negligible magnetic field effect, and higher B0 leads to a greater average plasma density. Te shows little variations in the plasma density range of 1011 cm-3- 1013 cm-3 for p0 〈 3.0 mTorr. Comparison of the simulation results with experiments suggests that the model can make reasonable predictions of Te in low pressure helicon discharges.     

Effects of the Hot Electron Interchange Instability on Plasma Confined in a Dipolar Magnetic Field

The Levitated Dipole Experiment (LDX) explores confinement and stability of plasma created within the dipole field of a strong superconducting magnet. During initial experiments, long-pulse, quasi-steady state discharges that last more than 10 s and have peak beta of more than 20% are studied. The plasma is created by multi-frequency electron cyclotron resonance heating (ECRH) at 2.45 and 6.4 GHz. A population of energetic electrons, with mean energies above 50 keV, dominates the plasma pressure. Creation of high pressure, high beta plasma is possible only when intense hot electron interchange (HEI) instabilities are stabilized by sufficient neutral gas fueling. The instabilities resonate with the magnetic drift motion of the energetic electrons and can cause rapid radial transport. Measurements of the electrostatic and magnetic fluctuations of the HEI instability are described along with observations of the instability’s spectral characteristics. Fluctuations of the outer poloidal field induced by the HEI show a rapid evolution of the perturbed pressure profile.      

Fusion Simulation Project: Integrated Simulation and Optimization of Magnetic Fusion Systems

This is the final report of a panel established as a subcommittee of the U. S. Department of Energy (DOE) Fusion Energy Sciences Committee (FESAC) on Integrated Simulation and Optimization of Magnetic Fusion Systems (ISOFS). The report was requested by the DOE in February 2002 and the approved report was transmitted to the DOE by the FESAC in December 2002. The report addresses the challenge of how to develop fully integrated capability for predicting the performance of externally-controlled systems including turbulent transport, macroscopic stability, wave-particle physics, and multi-phase interfaces.     

21 世纪主要能源展望

本文将讨论２１世纪主要能源，它包括化石燃料能源，裂变能和聚变能。下世纪人类将进一步发展核能，核能比起化石燃料能源可以避免化石燃料对环境所造成的影响，裂变能在２１世纪将变成更为重要的能源，聚变能从下世纪中叶开始将提供商业发电，它将为人类提供未来能源的最佳选择。     

RF plugging of mirror plasma

Discovery of superconducting materials that operate at high temperatures revive interest in the use of rf field for plasma confinement [1]. This paper discusses feasibility of a scheme where resonant rf cavities are attached to the mirror ends of an open system for plasma confinement.     

Magnetic Reconnection in the Spheromak: Physics and Consequences

Magnetic reconnection in the spheromak changes magnetic topology by conversion of injected toroidal flux into poloidal flux and by magnetic surface closure (or opening) in a slowly decaying spheromak. Results from the Sustained Spheromak Physics Experiment, SSPX, are compared with resistive MHD simulations using the NIMROD code. Voltage spikes on the SSPX gun during spheromak formation are interpreted as reconnection across a negative-current layer close to the mean-field x-point. Field lines are chaotic during these events, resulting in rapid electron energy loss to the walls and the low T _e < 50 eV seen in experiment and simulation during strong helicity injection. Closure of flux sufaces (and high T _e ) can occur between voltage spikes if they are sufficiently far apart in time; these topology changes are not reflected in the impedance of the axisymmetric gun. Possible future experimental scenarios in SSPX are examined in the presence of the constraints imposed by reconnection physics. Work performed under the auspices of the U. S. DOE by U. California LLNL under contract No. W-7405-Eng-48.