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An experimental study has been made of a number of factors that determine the pulse height resolution of Scintillation Counters. A statistical model is developed from which an analytic expression for the ideal line shape is obtained. Excellent agreement is found with observations using an artificial light pulser. An attempt to understand the noise spectra, exponential and non exponential under various conditions, has been made. A comparison is made between non crystalline organic scintillators and"sodium iodide crystals of similar sizes. It is shown that for gamma-ray detection an important contribution to the line width originates with variations in the light collection efficiency from different regions of the scintillators.

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A new experimental technique has been used to investigate the penetration of 1.88-MeV positrons and 1.77-MeV electrons in carbon, aluminum, copper, tin, lead, brass, Teflon, Plaskon, Lumarth, water, benzene, and toluene. These are the first such measurements for liquids. The results, which measure transmissions down to 2%, indicate greater transmission of positrons than electrons in solids and liquids, except in brass and Plaskon. The difference in transmission is 12% for Al, 35% for Pb, and 88% for toluene. The greater transmissions in aluminum and lead are in qualitative agreement with the scattering theory; however, there is at present no theoretical explanation for the measured differences in the rest of the solids and the liquids.