Journal of Microwave Power and Electromagnetic Energy (JMPEE)
TITLE	The Canadian Intense Neutron Generator [PDF]
AUTHORS	P.R. Tunnicliffe 1967 2 3 67-74
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Abstract Atomic Energy of Canada Ltd. has proposed construction of an Intense Neutron-Generator. The generator would produce uniquely-intense beams of thermal neutrons for solid-state and low-energy nuclear studies and would yield significant quantities of radioisotopes of both research and commercial value; it would also produce copious sources of mesons and energetic nucleons for use in intermediate-energy nuclear physics and in nuclear- structure studies. The primary neutron source of 10^19/sec would be generated by bombarding a heavy-element target with a continuous beam of 65 mA of I GeV protons. The target of circulating and cooled Pb-Bi eutectic would be surrounded by a tank of heavy water moderator yielding a maximum useful flux of 10^16 thermal neutrons/cm^2/sec in the region where neutron beams can be extracted. This high-energy spallation process for producing neutrons is nearly four times more efficient in producing neutrons per unit of thermal energy released in the neutron source compared with a fission reactor. Nevertheless, if energy costs for producing the 65 MW proton beam are to be within reason, the machine producing the beam must be efficient. A O.X, machine is in principle ideal but practical achievement of I GV is not likely within the time desired. An accelerator where the protons gain energy from radio-frequency fields is the most likely prospect. We have selected a linear accelerator as our reference design and detailed theoretical and experimental studies are in progress. The machine is based on the Los Alamos Meson Physics Facility design reoptimized for continuous rather than pulsed operation. It is approximately one mile long and is expected to achieve nearly 50 percent overall efficiency. There are two major portions, an 'Alvarez' section operating at 200 MHz accelerating the beam to about 150 MeV, followed by a 'Waveguide' section operating at 800 MHz. Protons are initially injected by an 0.75 MV D.C. accelerator. The Alvarez section consists of thirteen resonant high-Q tanks each requiring a 1.5 MW R.F. power supply; the 308 waveguide resonators are fed in pairs through a power divider from 0.5 MW R,F, units. The total R.F. power required is in excess of 90 MW C.W. Each R.F. unit is an amplifier fed from a common drive line; outputs have to be controlled to keep relative phase and absolute amplitude of the accelerator R.F. fields to within -1° and 1 percent respectively over a loading range of -5:1. Efficiency of R.F. generation is primarily determined by the final power-amplifier stage. While efficiency is a dominant requirement (80 percent A.C. to R.F. conversion is our objective), the amplifier must be capable of operating into a very narrowband load over a wide range of output with satisfactory control characteristics. It must moreover be reliable as indeed the whole amplifier chain must be. A crossed-field reentrant electron-beam device seems most suitable for the purpose and we have begun an experimental study of a possible 800 MHz tube. Pending review of the design frequencies we have chosen to study a superpower triode for the 200 MHz generator; it will enable us to gain experience with gridded tubes and give power for testing experimental accelerator structures.