A method for the measurement of total reaction cross-sections for charged particles

Abstract

A technique is described for the determination of total reaction cross-sections for charged particles by measuring the attenuation of the incident beam while traversing a thin target. By enclosing the target in a chamber which incorporates entry and exit ports to allow passage of the beam, most of the charged reaction products may be prevented from leaving the system. Absorption of a fraction of the incident beam due to nuclear reaction processes thereby results in a transfer of charge from the beam to the target system. Comparison of this charge with the total charge conveyed by the beam yields a direct determination of the attenuation and thence a measure of the reaction cross-section of the target nuclei. The method is readily adaptable to a range of incident particles and energies and is particularly suited to accelerators yielding average beam currents greater than 10 −4 μA. Results are presented for copper for a range of proton energies from 8.78 to 11.2 MeV. At 9.85 MeV, a total reaction cross-section of 790 ± 32 mb was obtained. Deuteron reaction cross-sections for nickel have also been measured, giving a value of 1460 ± 60 mb at 11 MeV.