RESUMO
The potential of fiber-based sensors to monitor the fluence of atmospheric neutrons is evaluated through accelerated tests at the TRIUMF Neutron Facility (TNF) (BC, Canada), offering a flux approximatively 109 higher than the reference spectrum observed under standard conditions in New York City, USA. The radiation-induced attenuation (RIA) at 1625 nm of a phosphorus-doped radiation sensitive optical fiber is shown to linearly increase with neutron fluence, allowing an in situ and easy monitoring of the neutron flux and fluence at this facility. Furthermore, our experiments show that the fiber response remains sensitive to the ionization processes, at least up to a fluence of 7.1 × 1011 n cm-², as its radiation sensitivity coefficient (~3.36 dB km-1 Gy-1) under neutron exposure remains very similar to the one measured under X-rays (~3.8 dB km-1 Gy-1) at the same wavelength. The presented results open the way to the development of a point-like or even a distributed dosimeter for natural or man-made neutron-rich environments. The feasibility to measure the dose caused by the neutron exposure during stratospheric balloon experiments, or during outer space missions, is presented as a case study of a potential future application.
RESUMO
Solutions containing a high concentration (0.325-0.995 g/ml) of natural-abundance ammonium heptamolybdate tetrahydrate ((NH(4))(6)Mo(7)O(24))·4H(2)O were irradiated at 13 MeV on a proton-beam cyclotron using a standard liquid target. (94m)Tc was produced via the (94)Mo(p,n)(94m)Tc reaction with measured yields of 110±20 MBq for the highest concentrated solution using 5 µA proton beams for 60 min. Saturation yields of up to 40±6 MBq/µA were achieved. Pertechnetate was isolated from the target mixture with 70.9±0.7% efficiency using a solid-phase extraction resin.