Detecting alpha radiation by scintillation in porous materials

This paper presents a study of some parameters essential to the development of a heterogeneous scintillation detector with improved alpha energy resolution and detection efficiency. Such a detector with better than 10% alpha energy resolution could provide in situ capability to identify and quantify important alpha-emitting radionuclides in dilute aqueous solutions. Nanoporous gel-silica is a potential scintillation matrix with the promise of improved energy resolution and 100% detection efficiency. Scintillating gel-silica made by a sol-gel process is under development. As a step toward realizing the system described, the dependence of alpha detection efficiency and intrinsic energy resolution in particulate and porous glass scintillation detectors is examined. The two main areas of this research are: 1) computer modeling of the geometric detection efficiency and energy dispersion in particulate and porous glass scintillation detectors and 2) experiments to test model predictions for detection of alphas in liquid-infiltrated porous glass structures. To confirm the predicted alpha energy deposition, we measured scintillation in nanoporous gel-silica infiltrated with an organic liquid scintillator. Results show that phase dimensions must be considered in constructing a heterogeneous detector for alpha spectroscopy. Nanometer-scale dimensions available in gel-silica essentially eliminate degradation of energy resolution due to energy dispersion of alpha particles within the liquid sample, while providing 100% detection efficiency.