Welcome to the Levitated Dipole eXperiment (LDX) web site. LDX is a novel experimental device designed to explore the physics of plasma confinement in a magnetic dipole field. What makes it unique? Besides levitating a 1/2 ton superconducting ring, we will conduct the first experimental test on the theory of plasma confinement by adiabatic compressibility. If this concept turns out to be correct, levitated dipoles may one day make an attractive magnetically confined fusion energy source. LDX is a collaboration between Columbia University's Dept. of Applied Physics and the MIT Plasma Science & Fusion Center and is funded by the Department of Energy's Office of Fusion Energy.

Previous studies [1-4] indicate that a levitated dipole would be favorable for a D-He3 fuel cycle based power source. The D-D cycle is the most promising because of the availability of deuterium. Recently we have considered utilizing a levitated dipole for the D-D cycle based power source. Fusion reactors based on the deuterium-deuterium (D-D) reaction would be superior to D-T based reactors in so far as they can greatly reduce the power produced in neutrons and do not requires the breeding of tritium. In a recent article titled "Helium Catalyzed D-D Fusion in a Levitated Dipole" we have proposed a fusion power source, based on an alternative fuel cycle which we call ``helium catalyzed D-D". We have explored the application of a levitated dipole as a D-D power source and found that a dipole may have the unique capability of producing excellent energy confinement accompanied by low particle confinement. Additionally a levitated dipole device would be intrinsically steady state and extract power as surface heating, permitting a thin walled vacuum vessel and eliminating the need for a massive neutron shield. We find that a dipole based D-D power source can potentially provide a substantially better utilization of magnetic field energy with a comparable mass power density as compared to a D-T based tokamak power source.

SOURCE - MIT Plasma Science & Fusion Center
SOURCE - Levitated Dipole eXperiment

Introduction

The dipole magnetic field is the simplest and most common magnetic field configuration in the universe. It is the magnetic far-field of a single, circular current loop, and it represents the dominate structure of the middle magnetospheres of magnetized planets and neutron stars. The use of a dipole magnetic field generated by a levitated ring to confine a hot plasma for fusion power generation was first considered by Akira Hasegawa after participating in the Voyager 2 encounter with Uranus [1]. Hasegawa recognized that the inward diffusion and adiabatic heating that accompanied strong magnetic and electric fluctuations in planetary magnetospheres represented a fundamental property of strongly magnetized plasmas not yet observed in laboratory fusion experiments. For example, it is well-known that global fluctuations excited in laboratory fusion plasmas result in rapid plasma and energy loss. In contrast, large-scale fluctuations induced by sudden compressions of the geomagnetic cavity (due to enhancements in solar wind pressure) or by unsteady convections occurring during magnetic substorms energize and populate the energetic electrons trapped in the Earth’s magnetosphere [2]. The fluctuations induce inward particle diffusion from the magnetospheric boundary even when the central plasma density greatly exceeds the density at the edge. Hasegawa postulated that if a hot plasma having pressure profiles similar to those observed in nature could be confined by a laboratory dipole magnetic field, this plasma might also be immune to anomalous (outward) transport of plasma energy and particles...

Rest of White Paper is here...

.A White Paper for the Fusion Community