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Precise radon measurements are a requirement for various applications, ranging from radiation protection over environmental studies to material screening campaigns for rare-event searches. All of them ultimately depend on the availability of calibration sources with a known and stable radon emanation rate. A new approach to produce clean and dry radon sources by implantation of 226 Ra ions into stainless steel has been investigated. In a proof of principle study, two stainless steel plates have been implanted in collaboration with the ISOLDE facility located at CERN. We present results from a complete characterization of the sources. Each sample provides a radon emanation rate of about 2 Bq, which has been measured using electrostatic radon monitors as well as miniaturized proportional counters. Additional measurements using HPGe and alpha spectrometry as well as measurements of the radon emanation rate at low temperatures were carried out., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The radium isotopes 226 Ra and 228 Ra can provide important data on the dynamics of deep-sea hydrothermal plumes that travel the oceans for decades and have great impact on the ocean chemistry. This study focuses on parameters important for obtaining low detection limits for 228 Ra using gamma-ray spectrometry. It is present at mBq-levels in samples collected during the US GEOTRACES 2013 cruise to the Southeast Pacific Ocean., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We present an investigation of the (222)Rn concentration in argon with ultra-low background proportional counters. Argon purification tests by means of cryo-adsorption of radon on activated carbon were performed. For gaseous argon the purification process was found to be very efficient. Also in liquid phase the (222)Rn concentration could be reduced significantly, however, the efficiency is lower than in the gas phase. We also have analyzed the initial (222)Rn concentrations in commercial liquid argon. It was found to be significantly higher than in liquid nitrogen.

Background estimations in neutrinoless double beta decay experiments (0nubetabeta) require reliable statistical limits on gamma-spectrometric low-level material screening measurements. For this purpose a custom method based on Bayesian statistics with reference to the international standard ISO 11929-7 is presented. The analysis combines the data from sample- and background spectra and comprises the physical knowledge of non-negative counting rates. It allows to incorporate multiple gamma lines of radionuclides. The confidence intervals pass continuously from two-sided intervals into single-sided upper limits.

An optimisation of the geometrical model of a p-type detector used for material screening was carried out to improve the accuracy of Monte Carlo simulations in reproducing spectrometric measurements. Gamma-ray sources were measured to determine the dimensions of the detector dead layer and borehole. An agreement between simulations and measurement within 3% was achieved at energies above 100 keV. In contrast, discrepancies on the order of 23% were encountered using the nominal parameters from the detector manufacturer.

The presented radon detection technique employs miniaturized ultra-low background proportional counters. (222)Rn samples are purified, mixed with a counting gas and filled into a counter using a special glass vacuum line. The absolute sensitivity of the system is estimated to be 40 microBq (20 (222)Rn atoms). For emanation investigations two metal sealed stainless steel vessels and several glass vials are available. Taking into account their blank contributions, measurements at a minimum detectable activity of about 100 microBq can be performed.

In present and future experiments in the field of rare events physics a background index of 10(-3) counts/(keV kg a) or better in the region of interest is envisaged. A thorough material screening is mandatory in order to achieve this goal. The results of a systematic study of radioactive trace impurities in selected materials using ultra low-level gamma-ray spectrometry in the framework of the GERDA experiment are reported.

Low background miniaturized proportional counters as developed for the GALLEX solar neutrino experiment can be applied to the detection of radioactive noble gas nuclides at very low activities. We have developed an apparatus that allows the activity of trace amounts of isotopes of the four noble gases Ar, Kr, Xe and Rn to be measured. The technique includes contamination-free chromatographic purification of raw gas samples and subsequent low-level counting. Minimum detectable activities of 100 microBq and below have been attained. The developed techniques can be used to determine the 222Rn and 85Kr concentration in nitrogen for the solar neutrino experiment BOREXINO. By applying efficient techniques to concentrate noble gases from nitrogen, minimum detectable activity concentrations below 1 microBq/m3 of nitrogen (STP) have been reached for both nuclides.

Among other radionuclides, 39Ar and 85Kr are potential background sources in the solar neutrino detector BOREXINO. The expected low event rate requires that the nitrogen used in the experiment needs to have lower concentrations than 0.5 microBq/m3 for 39Ar and 0.2 microBq/m3 for 85Kr, corresponding to volume concentrations in N2 of 0.4 x 10(-6)m3/m3 for Ar and 0.2 x 10(-12)m3/m3 for Kr. Applying gas mass spectrometry and special care in the sampling technique we succeeded in finding the required purity. In addition, we studied the possibility to purify nitrogen from Kr by the adsorption method.