Interaction of gamma rays with material (solid and gas): Photoelectric effect, compton scattering and pair production. Scintillation principles, types of scintillator, scintillation mechanisms, organic molecules, fluorescence and phosphorescence, quenching, inorganic scintillators, band structure and activators. Types and properties of organic and inorganic scintillators. Light collection and photoelectron production. Photomultiplier tubes; Basic elements, photocathode, electron multiplication.Spectroscopy with scintillators. Semiconductor detectors; Types of semiconductor (silicon, germanium, cadmium telluride, cadmium zinc telluride, etc...) different types of detector geometry; Planar, coaxial.High resolution spectroscopy of X - rays and gamma rays. Properties of spectrometers including resolution, peak to total ration (photofraction) and efficiency (total, full - energy peak, single escape and double escape).