A TOF spectrometer for elastic recoil detection

Abstract

A time-of-flight spectrometer was built for the ERD-TOF (Elastic Recoil Detection by Time Of Flight) and heavy ion RBS (Rutherford Backscattering Spectrometry) experiments with a 1.7 MV tandem Van de Graaff accelerator. 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 electrons from a thin carbon foil to a MCP (Micro Channel Plate). The advantage of this type of time detector is the good efficiency and no obstacles in the beam path at the cost of a small uncertainty in the flight length. The efficiency of the spectrometer was measured for the ions lighter than neon in the energy range of a few hundred keV to 7 MeV, and was better than 98% for the particles heavier than B. The intrinsic resolution of the time detector is about 220 ps. The time resolution of the spectrometer was measured as a function of incident particle type and energy. The mass resolution is below 1 amu for the particles of interest.