ArTTA-10mL: An instrument for 39Ar-dating of small ice and water samples

• Applicants: Professor Dr. Werner Aeschbach; Professor Dr. Markus Kurt Oberthaler
• Subject Area: Oceanography ; Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 326736714

• Final Report Year: 2021

Final Report Abstract

The radioisotope 39Ar with a half-life of 269 years is ideal for age dating of water and ice in a critical age range, but difficult to measure. The quantum technology Argon Trap Trace Analysis (ArTTA) enables sensitive and selective detection of single 39Ar atoms, drastically reducing the required sample size. The main objective of this project was to develop the analytical equipment from the prototype stage into a routine tool for scientific applications in the fields of oceanography, hydrogeology, and glaciology. A new and optimised sample preparation line for gas extraction from water followed by gas separation and argon purification was built in the first year of the project and further optimised in the second year. It now reaches argon yields of > 99% and purities of up to 99.7% within 1 - 2.5 h of processing time. Procedures and equipment for sampling, sample preparation, and data management for a wide range of applications (all types of water, ice, permafrost, and gases) have been developed and tested. Furthermore, a strong network of connections to scientific partners in the different fields of application has been established and several pioneering projects have been initiated and in part completed. Among others, the new preparation line was used to process samples from the Eastern Tropical North Atlantic and from Alpine glaciers. The successful analysis of these samples on the further improved prototype ArTTA machine represented the worldwide first applications of ArTTA. In parallel, a new ArTTA system was set up in a commercial container, ensuring a highly controlled environment and enabling future replication of the machine. Designing a new ArTTA machine building on the knowledge of the existing prototype also has led to new and compact solutions for the necessary advanced laser system, including compact fiber based spectroscopy of metastable argon, robust setups for light amplification and light frequency manipulation. By autumn 2018, 18 months after the start of the project, the first atom signal was detected in the vacuum system in the container. Many details had to be resolved before the first “single atom” signal was seen in the container by the end of 2019. The restrictions for laboratory work due to the corona pandemic have massively hindered the progress in optimizing the performance of the machine. Thus, the year 2020 has been used to design and build a new source with a very efficient liquid nitrogen management, program a datalogging system for all important parameters of the machine as well as a software preparing automatically a comprehensive summary of the measurement. The ArTTA laboratories at Heidelberg are now all set for the sample handling for most conceivable applications of 39Ar. The ArTTA analysis is possible on the prototype machine, which has led to first ground-breaking applications. The newly built ArTTA machine still requires further optimisation. While significant progress beyond the prototype stage has been achieved, further development and investment is needed to enable broad routine application of the method. Nonetheless, the technical advances made in the course of this project provide a strong basis for future projects making use of 39Ar dating. Our well-developed network of collaborations and several corresponding project proposals as well as about 100 samples waiting for analysis prove the high demand for the method. The innovative technology developed in this project and its first applications have attracted significant resonance in the media, e.g. Austrian newspapers and TV reporting on the dating of glacier ice.

Publications

• 2017. Bichromatic force on metastable argon for atom-trap trace analysis. Phys. Rev. A 96, 013424
  Feng, Z., S. Ebser, L. Ringena, F. Ritterbusch, M. K. Oberthaler
  
• 2018. 39Ar dating with small samples provides new key constraints on ocean ventilation. Nat. Commun. 9: 5046
  Ebser, S., A. Kersting, T. Stöven, Z. Feng, L. Ringena, M. Schmidt, T. Tanhua, W. Aeschbach, M. K. Oberthaler
  
• 2018. Argon purification system for 39Ar measurements with Argon Trap Trace Analysis (ArTTA), DPG Annual Meeting, Erlangen. E-Verhandl. DPG, UP 9.2.
  Rädle, V., P. Hopkins, A. Kersting, M. Schmidt, L. Ringena, Z. Feng, E. Mathouchanh, S. Ebser, M. K. Oberthaler, W. Aeschbach, and S. Beyersdorfer
  
• 2018. First 39Ar-dating of small ocean samples. 2018 Ocean Sciences Meeting, Portland, USA, CT11A-06
  Ebser, S., A. Kersting, Z. Feng, L. Ringena, M. Schmidt, S. Beyersdorfer, E. Mathouchanh, F. Ritterbusch, T. Tanhua, T. Stöven, W. Aeschbach, and M. K. Oberthaler
  
• 2018. The Heidelberg ArTTA: Pushing the sample volume limit for 39Ar dating, 3rd International Workshop on Tracer Applications of Noble Gas Radionuclides (TANGR2018), Hefei, China
  Ringena, L., A. Kersting, Z. Feng, S. Ebser, M. Schmidt, P. Hopkins, V. Rädle, W. Aeschbach, M. K. Oberthaler
  
• 2018. Ultrakalte Atome. Die Geschichte des Eises. Ruperto Carola 13/2018: 72–79
  Aeschbach, W., M. Oberthaler
  
• 2019. Application of quantum technology for radio-argon dating of glacier ice. International Symposium on Isotope Hydrology, IAEA, Vienna, Austria
  Feng, Z., P. Bohleber, S. Ebser, L. Ringena, M. Schmidt, A. Kersting, P. Hopkins, H. Hoffmann, A. Fischer, W. Aeschbach, and M. Oberthaler
  
• 2019. Dating glacier ice of the last millennium by quantum technology. Proc. Natl. Acad. Sci. USA, 116: 8781–8786
  Feng, Z., P. Bohleber, S. Ebser, L. Ringena, M. Schmidt, A .Kersting, P. Hopkins, H. Hoffmann, A. Fischer, W. Aeschbach, M. K. Oberthaler
  
• 2019. First Results and Potential of Ar-39 by Argon Trap Trace Analysis in the Tropical and Subpolar North Atlantic. Goldschmidt Conference 2019, Barcelona. Goldschmidt Abstracts, 2019, 1656
  Kersting, A., S. Ebser, Z. Feng, L. Ringena, M. Schmidt, J. Robertz, T. Stöven, T. Tanhua, D. Kieke, R. Steinfeldt, W. Aeschbach, and M. K. Oberthaler
  
• 2020. Argon Trap Trace Analysis: Radiometric dating of environmental samples with applied quantum technology, DPG Annual Meeting, Hannover. E-Verhandl. DPG, Q 44.7.
  Ringena, L., J. Robertz, M. Schmidt, N. Rigi-Luperti, F. Sandel, J. Gutekunst, A. Kersting, Y. Arck, D. Wachs, A. Kaiser, W. Aeschbach, and M. Oberthaler
  
• 2020. Evaluating 5 decades of atmospheric 85Kr measurements in the southern hemisphere to derive an input function for dating water and ice with implications for interhemispheric circulation and the global 85Kr emission inventory. J. Environ. Radioact. 225, 106451
  Kersting A., C. Schlosser, A. Bollhöfer, A. Suckow