A High-Tech Replacement for the Oeschger Counter

22 December 2010

More than 50 years ago, Hans Oeschger made science history with his invention of a device for 14C measurements at the University of Bern. Now, researchers are again at the forefront in developing a new 14C-analysis instrument in the Swiss capital. The research center that carries Oeschger's name is the driving force behind the project for a new radiocarbon dating system, which will be used jointly by different research groups.

Hans Oeschger never settled for second best: The nuclear physicist would not have used existing technology when he set about to build the first radiocarbon laboratory in Switzerland for his thesis. He did not hesitate to construct a new device from scratch. The fruit of his labor was an instrument so precise that scientists were able for the first time to measure even minute amounts of radioactivity. The device, now called an Oeschger counter, allowed researchers to explore new types of environmental archives including polar ice cores. And it was the analysis and interpretation of these drill cores from Greenland that brought Oeschger worldwide fame. The 14C Dating Laboratory was instrumental in building the reputation of climate research in Bern.

The instruments in the basement of the Physics Institute are steeped in history. Until now, they have provided precise radiocarbon measurements for samples aged up to 55,000 years. Still, the mere preparation of the samples requires considerable effort and the minimum unit of measurement is grams. Researchers in Bern, who have to process large numbers of samples and who seek accuracy to the milligram, increasingly have to go abroad. "The laboratory only manages to conduct a fraction of the required measurements in Bern, which corresponds to no more than about 300 samples per year," says Sönke Szidat, a lecturer for environmental radionuclides and nuclear dating. Szidat is one of the initiators of the 14C AMS project, together with Andreas Türler from the Laboratory of Radiochemistry and Environmental Chemistry and colleagues from the Oeschger Centre. The goal of the endeavor is to construct and operate a mass spectrometer for AMS (Accelerator Mass Spectrometry) at the University of Bern. It would be used for radiocarbon dating, tracing of environmental radioactivity and analysis of CO2 emissions.

User friendly and efficient

The project has just cleared its biggest hurdle: financing of the new facility is now assured. The University of Bern, the Swiss National Science Foundation and the Federal Office of Public Health agreed to fund the 1.8-million-Swiss-franc project. The University of Bern is building the instrument, called MIni radioCArbon DAting System (MICADAS), in cooperation with the ETH Zurich, which has gathered experience in the development of small-size accelerator mass spectrometers over the past years and is considered one of the worldwide leaders for this technique today.

The replacement of the now rather dated 14C Dating Installation in Bern has been discussed for quite some time, but the acquisition of a new facility only got underway when the Oeschger Centre launched a discussion among climate and environment researchers at the University of Bern. A survey showed that about a dozen research groups are in need of 14C dating for their projects and are thus interested in a user-friendly, efficient and low-priced new facility. The research projects range from the reconstruction of climate history over the study of the carbon cycle to the determination of sources of air-borne particulate matter. The interested parties formed a syndicate led by the Department of Chemistry and Biochemistry for the acquisition and operation of the MICADAS facility. This consortium has also been the driving force for fundraising. "This project is the perfect example of how the Oeschger Centre can pool strengths, use synergies and make even large projects become a reality," says Martin Grosjean, Director of the Oeschger Centre.

Strengthening its international position

The construction of the spectrometer will start at the beginning of 2011 in Zurich. Unlike a similar device that is already operational at the ETH Zurich, the new MICADAS system will be focused on exploring ultra-small samples. This way, the two 14C measuring facilities in Switzerland will complement each other perfectly. The system is scheduled to be operational in the middle of 2012. The top-notch facility will raise the profile of climate research in Bern, as did Hans Oeschger's 14C Dating Laboratory at that time. "The access to this facility will make the consortium's research groups attractive partners for international research projects," says Szidat, who leads the team operating the MICADAS. "This will strengthen our position and improve the competitiveness of the University of Bern as a whole."