A new detector for measuring three-dimensional momenta of charged particles in coincidence

A detector system for the study of the dissociation dynamics of molecular ions is described. The measurements of the time of flight and of the hit coordinates of the charged fragments on the detector are transformed into the three momentum components along Cartesian coordinates. The detector uses 2×32 independent channels which makes possible the simultaneous detection of several particles and a spatial resolution of 0.65 mm on a 40 mm diameter channel plate. The low dead time of this detector (≃1 ns) enables us to study the dissociation of homonuclear molecules and also the angular correlation and energy distribution between two electrons of very low kinetic energies. As an illustration of its possibilities, results obtained in the dissociation of charged molecular ions will be considered to illustrate the capacity of this detector for the identification of dissociation channels, the accurate kinetic-energy distribution, and the investigation of the dissociation kinematics.