A Time-of-Flight Chemical Accelerator for Low Center-of-Mass Energy Spreads

An apparatus to obtain high resolution of relative kinetic energy for collision experiments in the electron volt range is described. Because it is the center-of-mass system that is important in the interpretation of experiments, energy spreads in both the projectiles and the targets are considered. We achieve high resolution in a primary beam with a time-of-flight technique. The target particles are in the form of a crossed beam. Basically, the scheme consists of observing only those reaction products that are formed in a short range of primary-beam flight times. This means that good resolution may be obtained in spite of any inherent energy spread in the beam. The measured quantity is modeled mathematically to show the effect of the energy spreads that remain. These calculations may be used to arrive at the true velocity dependence of the center-of-mass cross sections.