Comparison of detector systems for the separation of ³⁶Cl and ³⁶S with a 3-MV tandem

The possibility of detecting ³⁶Cl for geological exposure dating has been explored for several years at VERA (the Vienna Environmental Research Accelerator). First results on real samples were obtained with an ionization chamber (developed at the ETH/PSI, Zürich, Switzerland) with two anodes. To improve the suppression of ³⁶S, we equipped the ionization chamber with an exit window and added a Time-of-Flight (TOF) system with a double-sided silicon strip detector (50x50 mm²) as stop detector. We optimized the TOF setup by using silicon nitride foils to reduce scattering tails in the energy spectra.
At 3 MV terminal voltage, corresponding to a particle energy of 24 MeV of ³⁶Cl⁷⁺, we achieved a ³⁶S7+-suppression of 21500 (50% ³⁶Cl-detector-efficiency).