LDX Begins Plasma Physics Experiments

Friday, August 13, 2004

Today, the first plasma physics experiments were conducted using the Levitated Dipole Experiment (LDX). LDX was built at MIT's Plasma Science and Fusion Center as a joint research project of Columbia University and MIT. This major milestone for the project signifies the completion of the fabrication of the experimental device and the initiation of scientific studies.

The Levitated Dipole Experiment (LDX) is a first-of-its-kind experiment incorporating three superconducting magnets and exploring the physics of high-temperature plasma confined by magnetic fields that resemble those surrounding magnetized planets, like Earth and Jupiter. The goal of the experiment is to study the properties of the confined plasma and to determine whether larger dipole magnets could someday be used to create a source of fusion power.

In today's experiment, a large superconducting charging coil was used to inductively energize a compact, high-current superconducting ring to more than 750,000 amperes. After disconnecting all cyrogenic and diagnostic services from the superconducting ring, it was twice lifted to the center of a large 16-foot diameter ultra-high vacuum chamber where it maintained a strong dipole magnetic field for over four hours of scientific experiments.

Four dozen deuterium plasma discharges, each lasting from 5 to 10 seconds in duration, were formed with 10 second pulses of multi-frequency microwave heating up to 6.2 kW. Each plasma contained a large fraction of energetic and relativistic electrons that created a significant pressure that caused outward expansion of the magnetic field.

Many measurements were recorded including multi-cord x-ray spectroscopy that measures the energetic electron temperature profile, arrays of magnetic flux loops and sensors that measure the pressure-driven diamagnetic currents, visible video photography that measures the evolution of the plasma structure, microwave interferometry that measures plasma density, and electrostatic probes inserted to measure the parameters of the edge plasma. Detailed analysis of the measurements are just underway.

The experiments were conducted by a team of five graduate students, two undergraduate students, and several technicians, superconducting magnet engineers, and plasma scientists, and include Alex Boxer, Jennifer Ellsworth, Val Fishman, Darren Garnier, Alex Hansen, Ishtak Karim, Jay Kesner, Rick Lations, Scott Mahar, Mike Mauel, Phil Michael, Joseph Minervini, Eugenio Oritz, Austin Roach, Don Strahan, Alex Zhukovsky, and Michelle Zimmermann.