T01_P08

LEA – A novel Low Energy Accelerator for Radiocarbon Dating under a long-term Performance Test

Ramsperger U¹,  De Maria D¹, Gautschi P¹, Maxeiner S², Müller A¹, Synal H¹, Wacker L¹

¹ETH Zurich, Zurich, Switzerland, ²ionplus, Dietikon, Switzerland

Based on MICADAS (Mini Carbon Dating System) technology the acceleration voltage at the gas stripper unit, where charge exchange of the negative ions takes place and interfering isobar molecules are dissociated, is further reduced from 200 kV for MICADAS to 50 kV for LEA (Low Energy Accelerator) system. By using He stripper gas at a local areal density of ≈ 0.5 μg/cm² molecular interferences can be destroyed at a particle energy of less than 100 keV without excessive beam losses that would impede reproducible measurements conditions. Detailed optimization of the acceleration stage hosting the stripper gas volume where necessary to balance molecule dissociation power and optical beam losses to enable measurement conditions suitable for routine high performance radiocarbon dating measurements. Basic elements such as the ion source, injection magnet, and the fast beam bouncing system are copies of the MICADAS design, whereas the mass spectrometer following the acceleration stage had been modified according to the reduced ion energy. After an initial testing phase of the LEA system it has been installed at ETHZ in a configuration suitable for routine radiocarbon dating measurements. Here, we present data of long-term measurements over several days with the LEA system and compare the results with data of the well-established MICADAS system, with an emphasis on stability and accuracy.