The recent discoveries in particle physics, the Higgs Boson and neutrino oscillations, voiced the need for new machines that can provide higher intensities, energy and precision. To study the neutrino oscillations in great details and to access new physics, a Neutrino Factory stands as an ultimate tool that offers a high intensity, well understood neutrino beam. On the other hand, a Muon Collider is indispensable for better understanding of a Higgs physics. Both machines share similar ingredients and one of them, that is essential to achieve high luminosity of the beams, is beam cooling. And the only feasible method to achieve cooling of a muons beam is based on ionization. An R&D project was established to verify a possibility of such a cooling, Muon Ionization Cooling Experiment (MICE). Its purpose is to build a cooling cell capable of cooling a muon beam by 10% and measure the effect (the cooling effect is attributed to a reduction of beam emittance) with an absolute precision of 0.1%. This is achieved by utilizing detectors of different technologies: scintillating fiber trackers, time-of-flight stations and calorimeters. One of the calorimeters, aimed to tag muons traversing the cooling cell without decay, is a fully active scintillator tracker-calorimeter. Construction and commissioning of this detector is the main subject of this thesis. Introduction and the first chapter are dedicated to physics motivation of Neutrino Factory and Muon Collider. The second chapter describes the Muon Ionization Cooling Experiment. And the last chapter constitutes the main part of the thesis containing the original work.