DIII-D (tokamak)

Template:Fusion devices

DIII-D is a tokamak that has been operated since the late 1980s by General Atomics (GA) in San Diego, USA, for the U.S. Department of Energy. The DIII-D National Fusion Facility is part of the ongoing effort to achieve magnetically confined fusion. The mission of the DIII-D Research Program is to establish the scientific basis for the optimization of the tokamak approach to fusion energy production.^[1]

DIII-D was built on the basis of the earlier Doublet III, the third in a series of machines built at GA to experiment with tokamaks having non-circular plasma cross sections. This work demonstrated that certain shapes strongly suppressed a variety of instabilities in the plasma, which led to much higher plasma pressure and performance. DIII-D is so-named because the plasma is shaped like the letter D, a shaping that is now widely used on modern designs, and has led to the class of machines known as "advanced tokamaks." Advanced tokamaks are characterized by operation at high plasma β through strong plasma shaping, active control of various plasma instabilities, and achievement of steady-state current and pressure profiles that produce high energy confinement for high fusion gain (ratio of fusion power to heating power).

The DIII-D program achieved several milestones in fusion development, including the highest plasma β (ratio of plasma pressure to magnetic pressure) ever achieved at the time (early 1980s) and the highest neutron flux (fusion rate) ever achieved at the time (early 1990s).

DIII-D is one of two large magnetic fusion experiments in the U.S. (the other being NSTX-U at PPPL) supported by the U.S. Department of Energy Office of Science. The program is focusing on R&D for pursuing steady-state advanced tokamak operation and supporting design and operation of the ITER experiment now under construction in France. ITER is designed to demonstrate a self-sustained burning plasma and with an energy gain of 10.

DIII-D Program

The DIII-D Program is a large international program, with over 600 users from more than 100 participating institutions. General Atomics operates the San Diego-based facility for the United States Department of Energy through the Office of Fusion Energy Sciences.^[2]

Research in DIII-D aims to elucidate the basic physics processes that govern the behavior of a hot magnetized plasma, and to develop a scientific basis for future burning plasma devices such as ITER and, ultimately, a fusion power plant. The tokamak consists of a toroidal vacuum chamber, surrounded by magnetic field coils which contain and shape the plasma. The plasma is created by applying a voltage to generate a large electrical current (more than one million amperes) in the chamber. The plasma is heated to temperatures ten times hotter than the sun by a combination of high-power neutral beams and microwaves. The plasma conditions are measured using instrumentation based on intense lasers, microwaves, and other precision plasma diagnostics.

History

History of DIII-D at General Atomics

In May 1974, AEC selected General Atomics to build the Doublet III magnetic fusion experiment based on the success of earlier Doublet I and II magnetic confinement experiments. In Feb 1978, the Doublet III fusion experiment achieved its first operation with plasma at General Atomics. The machine was later upgraded and renamed DIII-D in 1986. ^[3]