Ultra-cold photocathode electron beams
Introduction
With electrons produced from cold sources, in particular photoemitters, beams with very uniform particle velocities can be produced which, in their co-moving reference frame, present cold ensembles with internal temperatures amounting to only a few Kelvin. From GaAs photocathodes, cooled to liquid-nitrogen temperature, continuous electron beams with currents of 1 mA and more are produced whose internal beam temperatures have been observed to reach down to 5 K. Merged with stored ion beams in the TSR, such high-brilliance electron beams are used for collision experiments with correspondingly high energy resolution, focusing on Atomic and Molecular Quantum Dynamics. Moreover, for ion beams composed of heavy molecules with correspondingly small beam velocities, very efficient translational cooling - "electron cooling" - was recently observed, much faster than so far obtained with standard techniques.