The multifunctional spectrometer (MFS) is a new radiation monitor that together with component technology test bed makes the European Space Agency Alphasat Environment and Effects Facility - Technology Demonstration Payload 8 (AEEF-TDP8). The two units are hosted in the X panel of the Alphasat satellite in orbit since July 2013. MFS is an instrument specifically designed to characterize the space radiation environment in geostationary orbit. The mission lifetime of AEEF/TDP8 will be at least three years and TDP8 is expected to be acquiring scientific data during the whole period. Before launch, MFS was submitted to proton and electron beam tests at the Paul Scherrer Institute in Switzerland in 2010. The main purpose was the validation and calibration of the MFS protoflight model together with the estimation of particle energy resolution and identification capability. A full Geant4 simulation with computer-aided design geometry exported to geometry description markup language description the MFS in-flight configuration was built. Ground test results were validated with Geant4 simulation. The measurements of MFS proton channels and MFS proton response functions are validated using comparisons with INTErnational Gamma-Ray Astrophysics Laboratory/INTEGRAL Radiation Environment Monitor data during the solar energetic particle event of January 2014. In addition, an artificial neural network (ANN) unfolding method was developed in order to unfold MFS data. Comparisons show that the derived ANN Alphasat/MFS fluxes are in remarkable agreement with INTEGRAL/IREM proton fluxes.