Status of the pulsed photoelectron source for atomic and molecular collision experiments

For kinematically complete experiments on the fragmentation dynamics of atomic and molecular systems by electron impact, inherently cold and bunched electron beams at energies from some 10 eV up to keV are needed. A short-pulsed photoelectron source has been set up to meet the beam specifications required for these experiments. The gun is in operation and delivers short electron pulses using GaAs/AlGaAs heterostructure crystals. A quantum efficiency of 3% and a cathode lifetime of one week have been achieved. Planned future collision measurements require intense beams of cold and well-collimated electrons at low energy (<100eV). Design changes have been made to achieve this goal.