A combination of two 4π detectors for neutrons and charged particles.: Part I. The Berlin neutron ball—a neutron multiplicity meter and a reaction detector

Two 4π detectors for neutrons and charged particles have been combined for the investigation of GeV-proton and antiproton induced spallation reactions. It is a large neutron scintillator tank with a high-granularity charged-particle detector in its central vacuum chamber. Together they register the whole, neutral and charged, de-excitation cascade of the excited reaction complex as well as heavier reaction products, i.e. intermediate-mass and fission fragments and heavy residues. Part I of our communication describes the neutron detector Berlin neutron ball (BNB): Its spherical tank is filled with 1.5 m3 scintillator liquid, loaded with 0.4 wt% Gd. BNB recognizes each reaction in the target with a low inelasticity threshold of 2.5 MeVee and records event-wise the multiplicity of evaporated neutrons with ≈75% efficiency. Part II [12] describes the charged particle detector Berlin silicon ball (BSiB) assembled from 151 independent Si-detectors and six ancillary four-fold telescopes, considers its detection efficiency for various particle species and provides experience gained from the joint operation of both detectors, BNB and BSiB, as a filter on the excitation energy dissipated event-by-event in the spallation reaction.