Experimental measurements of neutron fluxes produced by proton beams (23-80Â 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; T1/2=2.6h). 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: S0=5.58×108 (Ep[MeV])1.69. Some measurements have also been done with a lead target.