A new system for the Rn-222 and Ra-226 assay of water and results in the BOREXINO project

We describe a very sensitive system for the 222 Rn and 226 Ra assay of water that we have constructed within the framework of the B orexino solar neutrino experiment. The technique that is applied for 222 Rn measurements is based on concentration of radon from water samples followed by gas purification and subsequent alpha counting in low-background miniaturized proportional counters. The same technique is applied to measure the 226 Ra concentration by determining the amount of 222 Rn in equilibrium with the 226 Ra in the water. Sensitivities of ∼1 mBq/m 3 for 226 Ra and ∼100 μBq/m 3 for 222 Rn have been achieved. We present results of measurements illustrating the performance of the system as well as investigations of samples from the B orexino water plant and the shielding water of the Counting Test Facility (CTF, a test facility for the B orexino detector).

26.65.+t
29.40.Cs
82.80.Bg
B orexino
Proportional counter
Radon
Radium
Solar neutrino
Water
B orexino

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