Novel technique for ultra-sensitive determination of trace elements in organic scintillators

Abstract

A technique based on neutron activation has been developed for an extremely high sensitivity analysis of trace elements in organic materials. Organic materials are sealed in plastic or high purity quartz and irradiated at the HFIR and MITR. The most volatile materials such as liquid scintillator (LS) are first preconcentrated by clean vacuum evaporation. Activities of interest are separated from side activities by acid digestion and ion exchange. The technique has been applied to study the liquid scintillator used in the KamLAND neutrino experiment. Detection limits of <2.4×10 −15 g 40 K/g LS, <5.5×10 −15 g Th/g LS, and <8×10 −15 g U/g LS have been achieved.

Systematic study of trace radioactive impurities in candidate construction materials for EXO-200

“…NAA results using the same facility and essentially the same techniques have been reported in the past [17] in more detail. In Ref.…”

“…Due to the large resonance integral in the neutron capture cross-section of 238 U, this nuclide is quite sensitive to this detail. Results listed in Table 3 include a statistical NAA results using the same facility and essentially the same techniques have been reported in the past [17] in more detail. In Ref.…”

“…Specifically the preconcentration and chemical separation techniques used in Ref. [17] were not employed, with one exception described below, for measurements in the present work. When surveying a large number of samples, such specialized techniques are not practical.…”

“…We attempted to quantify the Th and U retention of the evaporation process by mixing organometallic standards [17] with the HFE-7000. These studies were unsuccessful, but indicated a very low solubility of actinides in HFE-7000.…”

Radioactive contamination of scintillators

“…The same can be said about 210 Pb, daughter of 238 U, one of the most troublesome contaminant radionuclides for dark matter experiments. A very high sensitivity to 40 K, 232 Th and 238 U on the level of nBq/kg was reached by using neutron-activation technique to measure contamination of liquid scintillator for the KamLAND experiment [181]. While neutron-activation analysis is very powerful tool to measure radioactive contamination in organic scintillators, the method is much less effective to examine inorganic materials due to possible activation of scintillation crystals matrix [182].…”