[en] Fast neutron irradiation has been performed at liquid argon temperature as a realistic evaluation test for experiments at the LHC Collider at CERN, Early results presented in this note have been obtained with fast charge preamplifiers SiJfet and GaAs Mesfet for white noise and 1/f noise increase with neutron fluence. We have observed a degradation of the transconductance in the case of SiJfet, but a smaller effect on GaAs Mesfet. Optical devices were also studied for light emission with unsatisfactory results, and optical fibres for light transmission showing a remarkable stability. (author). 7 refs., 4 figs