GaAs Photo-Cathodes as Sources for Low-Velocity Electron Coolers
1 : 1 Max Planck Institute for Nuclear Physics, 69117 Heidelberg, Germany
(MPIK)
Photo-excited III/V semiconductors can be close-to-ideal sources of cold, continuous high-density electron beams. Since 2006, the experimental electron cooler of the Heidelberg TSR storage ring is operated using Negative Electron Affinity (NEA) emitters based on GaAs photo cathodes. Electron beam temperature is a crucial parameter for efficient application of an electron cooler in the context of singly-charged heavy ions. The low transverse electron beam temperature (~10 K) of our set-up has paved the way to strong electron cooling of slow (~0.01 c) molecular ion beams in a storage ring. The future electron cooler of the Cryogenic Storage Ring (CSR), presently in construction in Heidelberg, will be based on the same emitter cathode and will reduce the low-energy limit of the electron cooling technique even further, designed to operate at electron beam kinetic energies down to 1 eV. We give an overview of present and future applications of photo-cathode electron emitters in merged-beam experiments with atomic or molecular ions.
