Experimental measurements of neutron fluxes produced by proton beams (23–80 MeV) on Be and Pb targets

The “manganese bath” technique has been perfected to measure the total number of neutrons emitted when 23–80 MeV proton beams bombard a beryllium target. It consists in surrounding the neutron source with a large metallic cylinder filled with a manganese sulphate (MnSO4) solution. The neutrons are slowed down by water and partly captured by manganese (production of 56Mn; T 1 / 2 = 2.6 h ). The absolute calibration has been performed with a Ra–Be neutron source. Corrections have been applied for escaping neutrons in both cases. Our experimental results show that the total number of neutrons produced (S0) by the p+Be reaction, per second and per microampere of beam, can be approximated (for proton energy Ep between 23 and 80 MeV) by: S 0 = 5.58 × 1 0 8 (Ep[MeV])1.69. Some measurements have also been done with a lead target.