The single sphere neutron spectrometer (SP2) is a unique tool that allows performing active neutron spectrometry measurements by employing a single device instead of the usual multi-sphere Bonner spectrometers.


Nevertheless, it is characterized by the same high sensitivity and precision in determining the neutron flux over the entire energy range. It reduces at minimum any reproducibility uncertainty and, when employed with the on-line unfolding tool, it can perform real time measurements.

The SP2 core is constituted by 31 active 6LiF-covered Silicon neutron detectors installed over six concentric layers in the moderating assembly, so that they reproduce the spectrometric performance of a six-sphere Bonner sphere spectrometer. The signals are acquired by the built-in electronics and can either be analysed on-line or transmitted for the analysis to an external device for off-line unfolding.

SP2 can be used in a great number of activities related to scientific research, homeland security, cargo inspections, calibration laboratories, characterization of stray radiation fields for radiation protection purposes, periodical quality check of the neutron stray radiation field, and all applications involving the need of a fast and precise measurement of the neutron spectrum.

The SP2 is provided with its neutron response function, as a function of energy, calculated over the entire energy range. This has been validated via measurements performed with monochromatic neutron fields at different energies.

SP2 is the ideal device for performing active neutron spectrum measurements in every radiation environment, including mixed stray radiation fields, workplaces characterized by high gamma background and reference calibration laboratories.

Additional information

Main features:

Single sphere detector which provides a spectrometric performance equivalent to a six-sphere Bonner Sphere spectrometer
Radically innovative and unique device
Excellent photon rejection (completely insensitive to photon fields up to 50 mSv/h)
Extended-range active neutron spectrometer
Portable device with built-in signal processing electronics
Energy range from thermal neutrons up to 10 GeV
Isotropic response (max variability: ± 2% for neutron reference field of 241Am-Be source)
Typical sensitivity of 0.5 cps/µSv/h