The purpose of this assessment of the fusion energy sciences program of the Department of Energy's (DOE's) Office of Science is to evaluate the quality of the research program and to provide guidance for the future program strategy aimed at strengthening the research component of the program. The committee focused its review of the fusion program on magnetic confinement, or magnetic fusion energy (MFE), and touched only briefly on inertial fusion energy (IFE), because MFE-relevant research accounts for roughly 95 percent of the funding in the Office of Science's fusion program. Unless otherwise noted, all references to fusion in this report should be assumed to refer to magnetic fusion. Fusion research carried out in the United States under the sponsorship of the Office of Fusion Energy Sciences (OFES) has made remarkable strides over the years and recently passed several important milestones. For example, weakly burning plasmas with temperatures greatly exceeding those on the surface of the Sun have been created and diagnosed. Significant progress has been made in understanding and controlling instabilities and turbulence in plasma fusion experiments, thereby facilitating improved plasma confinement-remotely controlling turbulence in a 100-million-degree medium is a premier scientific achievement by any measure. Theory and modeling are now able to provide useful insights into instabilities and to guide experiments. Experiments and associated diagnostics are now able to extract enough information about the processes occurring in high-temperature plasmas to guide further developments in theory and modeling. Many of the major experimental and theoretical tools that have been developed are now converging to produce a qualitative change in the program's approach to scientific discovery. The U.S. program has traditionally been an important source of innovation and discovery for the international fusion energy effort. The goal of understanding at a fundamental level the physical processes governing observed plasma behavior has been a distinguishing feature of the program.

Why has the clean, limitless energy promised by fusion always seemed just out of reach? Search for the Ultimate Energy Source: A History of the U.S. Fusion Energy Program, explains the fundamentals and concepts behind fusion power, and traces the development of fusion historically by decade—covering its history as dictated by US government policies, its major successes, and its prognosis for the future. The reader will gain an understanding of how the development of fusion has been shaped by changing government priorities as well as other hurdles currently facing realization of fusion power. Advance Praise for Search for the Ultimate Energy Source: “Dr. Dean has been uniquely involved in world fusion research for decades and, in this book, describes the complicated realities like few others possibly could.” -Robert L. Hirsch, a former director of the US fusion program, an Assistant Administrator of the US Energy Research and Development Administration (ERDA); an executive at Exxon, Arco, and the Electric Power Research Institute (EPRI); and lead author of the book The Impending World Energy Mess (Apogee Prime Books, 2009). “In this book, Dr. Dean provides the many reasons why fusion has progressed more slowly than many had hoped. Budget is usually cited as the culprit, but policy is equally to blame. Facilities have been closed down before their jobs were done—or in some cases, even started. It seems this situation has become endemic in fusion, and if one thinks about it, in other nationally important Science and Technology initiatives as well.” -William R. Ellis, a former scientist at Los Alamos National Laboratory, Associate Director of Research at the US Naval Research Laboratory, a vice president at Ebasco Services and at Raytheon, and chair of the US ITER Industry Council and the US ITER Industrial Consortium.