XXth International Conference on Neutrino Physics and Astrophysics
C.Buck, B.Freudiger, G.Heusser, H.Simgen & G.Zuzel
Few Atom Measurements of 222-Radon
The radioactive noble gas nuclide 222-Radon represents a major
background source in most of the low energy low counting rate
experiments. In most cases the required low activity levels exceed
the sensitivities of standard measurement techniques by far. Therefore
highly sensitive techniques for the detection of radon in gases and
liquids as well as for the determination of radon emanation from
solids have to be developed. Moreover the dynamic behaviour of few
radon atoms has to be studied in order to develop efficient
purification procedures.
We present our approach to adress both items within the framework of
the BOREXINO solar neutrino experiment. 222-Radon is measured via the
alphas in its decay chain with miniaturized low background
proportional counters. Absolute sensitvities of 50 microBq have been
achieved. Concentration and purification procedures help to reduce
the specific sensitivities for certain samples in the sub-microBq
regime.
We have applied this powerful technique to test different cleaning
procedures used in BOREXINO and to investigate thoroughly many samples
that are used in the construction of the BOREXINO detector and major
subsystems of the detector. We present results that may be of great
relevance for future low count rate experiments.