Response of a Sodium - Iodide Scintillation Spectrometer to 10 - to 20 - Million - Electron - Volt Electrons and X - Rays

The response of a la rge-crystal sodium-iodide spectrometer was studied fo[' individual monoenergetic electrons extracted from a 50-million-electron-volt betatron operatcd between 1 a nd 20 Mev. The energy resolut ion with crystals 5 inches in diameter by 4 inches in length a nd 5 inches in diameter by 9 inches in length reaches its optimum value fo r electrons of 6 Mev where t he total width of t he pulse-height distribut ion at half max imum is 4 percent. Synthese~ of pulseheight distribu t ions for 11a nd 19-Mev monoenergetic X-ray photons a re made by using the experimental electron pulse-height distributions. The computed result compare favorably with the measured pulse-height distri butio ns for 11 .6and 17.6-Mev gamma ra.vs. Syntheses provide one of the few procedures for predicting spectrometer respo nse function s in t his X-ray energy range.