backDesign of the spectrometer
Five of the 12 NEMUS polyethylene spheres are shown at the back of the picture. The supports, which are adapted to the individual spheres, ensure that the position of the central thermal detector is in every case at the same level, independently of the diameter of the sphere. Three spherical proportional counters (3.2 cm in diameter) filled with 3He gas are shown in the foreground, partly hidden by special polyethylene inserts.
The front of the picture shows parts of the modified spheres. Both the polyethylene and the lead (left) or copper (right) shells are fabricated as half-shells. The combination of spherical shells of different thickness allows different responses at high neutron energies with a small number of single components.
Response of the spectrometer
Response functions of the Bonner spheres of the NEMUS spectrometer. The response is based on Monte Carlo calculations which have been validated with calibration measurements carried out at PTB.