A spectrometer for low energy heavy ion ERDA

An ERDA detector telescope consisting of a time-of-flight (ToF) system combined with a gas ionization chamber (GIC) has been developed which is specialized for the identification of very low energy ions. Equipped with a large area patterned silicon nitride entrance window of 130 nm thickness, the GIC allows heavy ion detection well below 1 MeV with sufficient resolution for particle identification. The ToF system has a start detector with a diamond-like carbon (DLC) foil of only 0.5 mu g/cm(2), which warrants excellent energy resolution for depth profiling. The system has been tested with I-121, Au-197 and Ti-48 projectiles of energies between 1.5 and 12 MeV. In the low mass range (up to 30 amu) the mass resolution is better than 1 in 35 at a recoil energy of approximately 3 MeV. A depth resolution of 1.5 nm (FWHM) has been obtained at a TiO2 surface using 1.5 MeV 1271 projectiles. The spectrometer is well suited for high resolution near-surface ERDA analysis even at accelerators with very low beam energies. (c) 2006 Elsevier B.V. All rights reserved.