A TOF SPECTROMETER FOR ELASTIC RECOIL DETECTION

A time-of-flight spectrometer was built for the ERD-TOF (Elastic Recoi l Detection by Time Of Flight) and heavy ion RES (Rutherford Backscatt ering Spectrometry) experiments with a 1.7 MV tandem Van de Graaff acc elerator. The spectrometer consists of two time pick-off detectors and a SSB (Silicon Surface Barrier) detector with variable flight lengths . The time detector uses an electrode to accelerate and to focus the e lectrons from a thin carbon foil to a MCP (Micro Channel Plate). The a dvantage of this type of time detector is the good efficiency and no o bstacles in the beam path at the cost of a small uncertainty in the fl ight length. The efficiency of the spectrometer was measured for the i ons lighter than neon in the energy range of a few hundred keV to 7 Me V, and was better than 98% for the particles heavier than B. The intri nsic resolution of the time detector is about 220 ps. The time resolut ion of the spectrometer was measured as a function of incident particl e type and energy. The mass resolution is below 1 amu for the particle s of interest. (C) 1998 Elsevier Science B.V.