Study of quenchable and unquenchable background for Packard Tricarb 2900TR liquid scintillation analyzer

Background study was carried out using two types of scintillators viz., dioxane and Optiphase Hisafe-3 that are being used in our laboratory. The difference in the background levels was also studied using different volumes of quenchers such as nitro methane, carbon tetra chloride and chloroform. The unquenchable background was found to lie in the 0-18 keV energy region, whereas the quenchable background lie in the 19-2000keV energy region. It was observed that the main contributor to the unquenchable part of the background is Cerenkov radiation, which is quenched by colour quencher but not by chemical quencher. (author)