Regensburg 2019 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
ST: Fachverband Strahlen- und Medizinphysik
ST 5: Dosimetry and MRI
ST 5.5: Vortrag
Mittwoch, 3. April 2019, 10:45–11:00, Kunsthalle
Ion-Implanted Ra-226 as a primary Rn-222 emanation standard — •Florian Mertes1, Stefan Röttger1, Annette Röttger1, Reinhard Heinke2, Tom Kieck2, Nina Kneip2, Dominik Studer2, and Klaus Wendt2 — 1Physikalisch-Technische Bundesanstalt, Braunschweig — 2Johannes Gutenberg-Universität, Mainz
The PTB investigated the use of ion-implanted Ra-226 as a primary standard for the generation of reference Rn-222 atmospheres. Ra-226 was implanted after laser-ionization at the RISIKO mass-separator of the Johannes Gutenberg-University Mainz. Implantation was carried out into tungsten and aluminum targets at 30 kV acceleration potential. Since the Rn-222 nucleus has a recoil energy of about 86 keV after the decay of Ra-226, a fraction of the generated Rn-222 can escape from the target. Absolute determination of implanted Ra-226 activity was carried out with defined solid-angle α-spectrometry. The fraction of escaping Rn-222, the emanation factor, was determined by γ-spectrometry with HPGe- and solid-state scintillation-detectors. Thereby, the implanted source was compared to a second implanted source that was sealed against Rn-222 escape. The emanation factor is directly calculated by comparing Rn-222 progeny and Ra-226 count rate ratios of the respective sources. The emanation factors appear to be unaffected by relative humidity and temperature changes. With these sources and an appropriate reference volume, stable Rn-222 activity concentrations in the regime below 300 Bq· m−3 can be generated at uncertainties not exceeding 3 % (k = 1).