N. Frodyma, K. Pelczar,  M. Wójcik

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http://dx.doi.org/10.1016/j.nima.2014.01.039

Abstract

The results of alpha spectrometric measurements of the activity of ²²²Rn daughters dissolved in liquefied nitrogen are presented. A direct detection method of ionized alpha-emitters from the ²²²Rn decay chain (²¹⁴Po and ²¹⁸Po) in a cryogenic liquid in the presence of an external electric field is shown. Properties of the radioactive ions are derived from a proposed model of ion production and transport in the cryogenic liquid. Ionic life-time of the ions was found to be on the order of 10 s in liquid nitrogen (4.0 purity class). The presence of positive and negative ions was observed.

²²⁶Ra, ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po deposition and removal from surfaces and liquids

M. Wójcik and G. Zuzel

Download: DOI: 10.1007/s10967-012-2180-5

Abstract

Deposition of 226Ra from water on nylon was investigated. Measurements performed for different pH and different radium concentrations in the water gave similar absolute activities deposited on the foil surface. Obtained results were used to estimate the amount of 226Ra plated-out on the nylon scintillator vessel in the solar neutrino experiment BOREXINO during filling of the detector. Another problem studied in the frame of BOREXINO was the removal of 210Pb from its organic liquid scintillator by applying distillation and water extraction. After several tests had been performed for both methods it was found that after the water extraction the initial lead content in the scintillator sample was reduced only accordingly to the ratio of the volumes of the applied liquids (simple dilution). In contrast to this, distillation was very effective providing in the best case a 210Pb reduction factor higher than 100. Removal efficiencies of the long-lived 222Rn daughters during etching from surfaces of standard and high purity germanium were investigated in the frame of the GERDA experiment, which aims to search for neutrino-less double beta decay of 76Ge. The standard etching procedure of Canberra used during production of high purity n-type germanium diodes was applied to germanium discs, which had been exposed earlier to a strong 222Rn source for its progenies deposition. In contrast to copper and stainless steel, 210Pb, 210Bi and 210Po was removed from germanium very efficiently. An evidence of a reverse process was also observed—the isotopes were transferred from the etchant to the clean germanium surface.

Volume 676, 1 June 2012, Pages 140–148

G. Zuzel a), M. Wójcik b)

a) Max Planck Institute for Nuclear Physics, P.O. Box 103 980, D-69029 Heidelberg, Germany
b) M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Kraków, Poland

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http://www.sciencedirect.com/science/article/pii/S0168900211022522

Abstract

Removal of the long-lived 222Rn daughters from copper and stainless steel surfaces was investigated. Etching and electropolishing were applied to discs exposed earlier to a strong radon source for 210Pb, 210Bi and 210Po deposition. Cleaning efficiency for 210Pb was tested with a n-type high purity germanium spectrometer, for 210Bi a beta spectrometer and for 210Po an alpha spectrometer was used. According to the performed measurements electropolishing removes very effectively all the isotopes from copper and stainless steel. Copper etching reduces efficiently lead and bismuth however for polonium the effect is negligible because of its fast re-deposition. For stainless steel, etching is much more effective compared to copper and it also works for 210Po.

Volume 676, 1 June 2012, Pages 149–154

G. Zuzel a), M. Wójcik b), B. Majorovits c), M.O. Lampert d), P. Wendling d)

a) Max Planck Institute for Nuclear Physics, P.O. Box 103 980, D-69029 Heidelberg, Germany
b) M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Kraków, Poland
c) Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany
d) Canberra-France, 1 Chemin de la Roseraie, B.P. 311, 67834 Tanneries Cedex, France

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http://www.sciencedirect.com/science/article/pii/S0168900211021929

Abstract

Removal and deposition efficiencies of the long-lived 222Rn daughters during etching from and onto surfaces of standard and high purity germanium were investigated. The standard etching procedure of Canberra–France used during production of high purity n-type germanium diodes was applied to germanium discs, which have been exposed earlier to a strong radon source for deposition of its progenies. An uncontaminated sample was etched in a solution containing 210Pb, 210Bi and 210Po. All isotopes were measured before and after etching with appropriate detectors. In contrast to copper and stainless steel, they were removed from germanium very efficiently. However, the reverse process was also observed. Considerable amounts of radioactive lead, bismuth and polonium isotopes present initially in the artificially polluted etchant were transferred to the clean high purity surface during processing of the sample.