Sodium Activated Cesium Iodide as a Gamma Ray and Charged Particle Detector

Recently developed sodium activated cesium iodide crystals offer a number of unique advantages as scintillators. The sodium activator produces a relative pulse height of approximately twice that of thallium activated cesium iodide and the emission decay constant of the new material is half that of the CsI(Tl). The pertinent physical properties of CsI(Na), including refractive index, optical transmission, and fluorescent emission characteristics are summarized and the gamma-ray mass absorption coefficients calculated from elemental cross sections are presented. Single crystal ingots up to ten inch diameter have been grown and data obtained from these crystals are reported. These data include relative pulse heights, linearity of response, resolution as a function of gamma energy, emission decay constant, response to alpha and beta, and the relative pulse height as a function of temperature from -60° C. to +160° C.