Mercuric Iodide is a preferred candidate material for truly room-temperature radiation detectors because of its large electronic bandgap (2.1 eV) and the high atomic numbs of its constituent elements, which results in a high photopeak efficiency. The spectroscopic performance of the detectors is determined by the electronic transport properties of the material which depends on the purity and the structural homogeneity of the single crystals from which the detectors are fabricated. Recent advances in purification and crystal growth have made it possible to fabricate routinely large,stable gamma ray and X-ray detectors and counters. The gamma ray detectors (25mm x 25mm x 3mm) with a spectral resolution better than 4% at Cs-137 are combined with a preamplifier and voltage filter in a stand-alone module which minimizes microphonic noise. This module can be incorporated in a portable spectrometer instrument with a total weight of less than 4 kg (batteries included). The counter detectors (25mm x 25mm x 5mm) are incorporated in a pocket-size radiation intensity counter with high sensitivity. A short description will be given of the methods used to synthesize and purify material to grow substantial single crystals up to 150 cubic centimeter in volume and to fabricate the detectors. The design and operation of the instruments will be discussed in more detail and performance characteristics will be presented. The operation of the instruments will be demonstrated if conditions permit.
