F or over four decades the federal government has supported research to develop reactors that harness fusion energy for commercial electric power production. However, even the most op-
timistic proponents of the U.S. Department of Energy's fusion energy program note that many
scientific, engineering, and economic challenges remain. Meeting these challenges suffi-
ciently to construct a prototype commercial fusion powerplant is expected to require tens of billions
of dollars in experimental facilities and research over the next several decades.
This background paper, responding to a request by the House Committee on Science, focuses on
the following two questions for the U.S. fusion energy program. First, what is the role of the Tokamak
Physics Experiment (TPX), an approximately $700 million fusion reactor currently awaiting a con-
gressional decision to begin construction? This paper examines the history of TPX planning; the an-
ticipated scientific, engineering, and institutional contributions; and the relationship between the
TPX and the next major planned tokamak facilities, the International Thermonuclear Experimental
Reactor (ITER), currently in the design stage, and the DEMO facility planned for operation in about
three decades, which would be the first fusion device to demonstrate production of electricity.