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This report was prepared in late 1965 at the request of the U.S. House-Senate Joint Committee on Atomic Energy (JCAE) to review its program on controlled thermonuclear research (CTR), now called just “fusion energy research.” It was transmitted to them on June 11, 1966 by then chairman of the U.S. Atomic Energy Commission (AEC) Glenn T. Seaborg. The AEC is the predecessor agency of the current U.S. Department of Energy (DOE). The report has previously only been available as AEC report TID-23277. This version of the report is complete except for the omission of lengthy discussions of the then current fusion research activities at various AEC sites. This paper includes, as does the original report, a copy of Seaborg’s June 11, 1966 transmittal letter and, as appendices, copies of a 1962 review of the fusion program by the AEC’s General Advisory Committee (GAC), a review of the Policy Paper by a special 1965 AEC committee, prior to its submittal to the JCAE, comments on the report by the GAC and the President’s Science Advisory Committee, and the charter for then newly established CTR Standing Committee.

The attenuation of (319\ifmmode\pm\else\textpm\fi{}4)-Mev photons in liquid hydrocarbons has been measured and has been used to infer the cross section for pair production in the field of the orbital electrons (triplet production).Targets of benzene (${\mathrm{C}}_{6}$${\mathrm{H}}_{6}$) and cyclohexane (${\mathrm{C}}_{6}$${\mathrm{H}}_{12}$) were used in good geometry. A pair spectrometer with three fast counter channels was used to measure the intensity of the transmitted photon beam. The synchrotron was monitored with a modified pair spectrometer that was sensitive only to the bremsstrahlung spectrum above 300 Mev.The total absorption cross sections in hydrogen and carbon at 319 Mev have been found to be 18.0\ifmmode\pm\else\textpm\fi{}1.8 mb per hydrogen atom, and 321.1\ifmmode\pm\else\textpm\fi{}2.8 mb per carbon atom, respectively.Subtraction of the theoretical nuclear pair and electron Compton cross sections and the experimental photomeson cross sections in hydrogen from the total hydrogen absorption cross section gives 6.8\ifmmode\pm\else\textpm\fi{}1.8 mb for the experimental triplet cross section, as compared with the theoretical value of 7.68 mb. Similarly, when one subtracts the cross sections for competing processes in carbon, one gets for the triplet cross section at 319 Mev the value 46.6\ifmmode\pm\else\textpm\fi{}6.4 mb, compared with the theoretical value of 44.4 mb. The large uncertainty in the carbon triplet cross section is due to uncertainties in the cross sections for the competing processes.