Isobar suppression in AMS using laser photodetachment

Abstract We are investigating the possibility of using laser photodetachment of negative atomic and molecular ions as an additional isobaric selection filter in accelerator mass spectrometry. The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at AMS facilities. We will focus on the astrophysical relevant radionuclide 182Hf, which is one of the isotopes measured with the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator) at the University of Vienna. Laser-induced isobar suppression is also of importance for radioactive-beam facilities. The present detection limit for measuring the isotope ratio 182Hf…

First application of calorimetric low-temperature detectors in accelerator mass spectrometry

Abstract For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of 236U/238U for several samples of natural uranium, 236U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV 238U is ΔE/E=4–9×10−3, depending on the experimental co…

Uran aus deutschen Nuklearprojekten der 1940er Jahre – eine nuklearforensische Untersuchung

Wir berichten hier uber eine nuklearforensische Analyse verschiedener Uranmaterialien aus deutschen Nuklearprojekten der 1940er Jahre, bei denen Uranmetall in verschiedenen Geometrien verwendet wurde. Mithilfe des 230Th/234U-Isotopenverhaltnisses konnte fur das Metall ein Produktionszeitraum von 1940 bis 1943 bestimmt werden. Die geographische Herkunft des Urans wurde anhand des Spurengehalts an Seltenerdelementen und der Strontium-Isotopenverhaltnisse bestimmt. Die Ergebnisse zeigen, dass das bei den deutschen Nuklearprojekten verwendete Uran aus Minen in der Tschechischen Republik stammt. 236U und 239Pu wurden in Spuren nachgewiesen. Diese entsprechen in etwa der Haufigkeit dieser Isotope…

Precise dating of the Middle-to-Upper Paleolithic transition in Murcia (Spain) supports late Neandertal persistence in Iberia

Abstract The late persistence in Southern Iberia of a Neandertal-associated Middle Paleolithic is supported by the archeological stratigraphy and the radiocarbon and luminescence dating of three newly excavated localities in the Mula basin of Murcia (Spain). At Cueva Anton, Mousterian layer I-k can be no more than 37,100 years-old. At La Boja, the basal Aurignacian can be no less than 36,500 years-old. The regional Middle-to-Upper Paleolithic transition process is thereby bounded to the first half of the 37th millennium Before Present, in agreement with evidence from Andalusia, Gibraltar and Portugal. This chronology represents a lag of minimally 3000 years with the rest of Europe, where th…

Cover Picture: Uranium from German Nuclear Power Projects of the 1940s— A Nuclear Forensic Investigation (Angew. Chem. Int. Ed. 45/2015)

Titelbild: Uran aus deutschen Nuklearprojekten der 1940er Jahre – eine nuklearforensische Untersuchung (Angew. Chem. 45/2015)

Uranium from German Nuclear Power Projects of the 1940s— A Nuclear Forensic Investigation

Here we present a nuclear forensic study of uranium from German nuclear projects which used different geometries of metallic uranium fuel. Through measurement of the (230)Th/(234)U ratio, we could determine that the material had been produced in the period from 1940 to 1943. To determine the geographical origin of the uranium, the rare-earth-element content and the (87)Sr/(86)Sr ratio were measured. The results provide evidence that the uranium was mined in the Czech Republic. Trace amounts of (236)U and (239)Pu were detected at the level of their natural abundance, which indicates that the uranium fuel was not exposed to any major neutron fluence.