Effect of Coulomb interaction on time of flight of cold antiprotons launched from an ion trap

Time‐of‐flight spectra for Maxwell–Boltzman (MB) distributions of antiprotons initially held in an ion trap and detected after being launched through a 50‐cm‐long shielding drift tube have been calculated. The distributions used are of temperature 0.4–40 K, cubic length 0.003–3.0 cm, and number 10–100 particles. The mutual Coulomb repulsion of the particles causes a reduction in the number of late arrival particles expected from the MB velocity distribution. The Coulomb energy is not equally divided among the particles during the expansion. The energy is transferred preferentially to the outer particles so that the reduction in the number of slow particles is not necessarily large. The reduction factor is found to be greater than unity when the potential energy of the trapped ions is greater than ∼5% of the ions’ kinetic energy and is ∼2 for the launch parameters of the Los Alamos antiproton gravity experiment.