Relative Probability of Ternary Fission with Emission of Long-Range Alpha Particles in the Thermal-Neutron Fission ofU235

The ratio of binary to ternary fission in $U^{235}$ has been measured using solid-state detectors and aluminum absorbers, for two reactor beams, having cadmium ratios of 30 to 1 and 200 to 1, and for incident neutron energies of 0.003, 0.0253, 0.08, and 0.3 eV. Furthermore, a new method of measuring this ratio without the use of absorbers is presented. The results obtained show that the binary-to-ternary fission ratio in ${\mathrm{U}}^{235}$ is a constant to a precision of 3% in the energy region between 0.003 and 0.3 eV. The measurements performed with the two reactor beams, having cadmium ratios of 30 to 1 and 200 to 1, gave for this ratio 518±13 and 512±14, respectively. The measurement performed without an absorber gave a value of 490±20 for the 30-to-1 cadmium-ratio beam. It is concluded that the binary-to-ternary fission ratio in ${\mathrm{U}}^{235}$ is a constant in the energy region considered to within the precision of the present experiment.