The micromaser, or one-atom maser, is a defining experiment in the fields of quantum optics and cavity quantum electrodynamics. In its natural operation, it deals with small numbers excitations of a single field mode and their interaction with single atoms. Previous incarnations of the experiment have produced a number of important results that have formed the foundation of experimental cavity quantum electrodynamics. This thesis describes the construction of a new micromaser system. We have incorporated a number of new technologies in the design that will enable us to perform experiments in an as yet unexplored region of parameter space. Particular attention is paid to the detectors, and a novel technique was developed and tested to optimise the system. Theoretical work has also been carried out into the application of the micromaser to ultra-high efficiency single microwave photon detection.