Neutron spectrum measurements inside a self-shielded cyclotron during 18F production using a single-cylindrical neutron spectrometer with gold and indium activation foils

The Single-Cylindrical Neutron Spectrometer (SCNS) is a single moderated spectrometer in the form of a cylinder with a diameter of 8 cm and a length of 16 cm. Seven Au activation foil type neutron detectors are installed on the moderator axis with varying distances. This spectrometer is used to measure the neutron spectrum in self-shielded cyclotron during 18F production using a proton of 11 MeV and a beam current of 25 µA for 70 min. The detector response was calculated using MCNPX 2.7. The measurement results obtained activity of 198Au and 116mIn and were validated with simulation using MCNPX. With the detector response values and detector activity from the measurements, a neutron spectrum was obtained using the unfolding technique using the UMG program. The neutron spectrum from measurements using SCNS with Au and In activation foil detectors has a difference of 8 %. Meanwhile, with the MCNPX calculation results, the measurement results using the Au foil are 1 % while with the In foil it is 10 %.