In order to measure the capture cross section of C13 at thelowest possible energy a scintillation detector in conjunction witha high current ion source was developed. Because of heat dissipationproblems the ion source was pulsed and suitable electronic circuitrywas developed to take advantage of the peak currents available.With this equipment it was found possible to obtain proton currentsof one milliampere and a detection efficiency of eight percent.
At 128 kilovolts the capture cross section is,
σ = 5.0 ± 1.0 x 10-33 cm2
Of the resulting radiation approximately eighty percent is 8 Mev inenergy while the remaining is either a two or three step cascadewith gamma ray energies between two and four million volts of energy.
In the equation,
σ = a/E e-b/E 1/2
b = 5.96 Mev1/2, and a = 10-2 Mev barn.
