A reference radiation facility for dosimetry at flight altitude and in space.

A reference facility for the intercomparison of active and passive detectors in high-energy neutron fields is available at CERN since 1993. A positive charged hadron beam (a mixture of protons and pions) with momentum of 120 GeV/c hits a copper target, 50 cm thick and 7 cm in diameter. The secondary particles produced in the interaction are filtered by a shielding of either 80 cm of concrete or 40 cm of iron. Behind the iron shielding, the resulting neutron spectrum has a maximum at about 1 MeV, with an additional high-energy component. Behind the concrete shielding, the neutron spectrum has a pronounced maximum at about 70 MeV and resembles the high-energy component of the radiation field created by cosmic rays at commercial flight altitudes. The facility is used for a variety of investigations with active and passive neutron dosimeters. Its use for measurements related to the space programme is discussed.