  Radiation hardness is an important requirement for solid state readout
devices operating in high radiation environments common in particle physics
experiments. The MEGII experiment, at PSI, Switzerland, investigates the
forbidden decay $\mu^+ \to \mathrm{e}^+ \gamma$. Exploiting the most intense
muon beam of the world. A significant flux of non-thermal neutrons (kinetic
energy $E_k\geq 0.5 ~MeV$) is present in the experimental hall produced along
the beamline and in the hall itself. We present the effects of neutron fluxes
comparable to the MEGII expected doses on several Silicon PhotoMulitpliers
(SiPMs). The tested models are: AdvanSiD ASD-NUV3S-P50 (used in MEGII
experiment), AdvanSiD ASD-NUV3S-P40, AdvanSiD ASD-RGB3S-P40, Hamamatsu and
Excelitas C30742-33-050-X. The neutron source is the thermal Sub-critical
Multiplication complex (SM1) moderated with water, located at the University of
Pavia (Italy). We report the change of SiPMs most important electric
parameters: dark current, dark pulse frequency, gain, direct bias resistance,
as a function of the integrated neutron fluency.
