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Abstract

In the present work a novel electron-ion merged-beam setup for electron cooling
and electron-ion recombination studies has been implemented in the electrostatic
cryogenic storage ring CSR and commissioned. The photocathode setup for cold
electron beams previously operating at the heavy ion storage ring TSR has been
integrated in the CSR electron cooler. After first tests of the electron beam transport,
realized by superconducting magnets in the cryogenic part of the storage
ring, systematic studies of electron cooling of stored keV ion beams were performed.
Efficient electron cooling of atomic ions F⁶⁺ and O⁺ as well as molecular
ions HeH⁺ and HD⁺ has been realized and investigated at low electron energies
down to about 10 eV and at low electron densities of only a few times 10⁵ cm^-3.
Electron cooling times in the range of only a few seconds and transverse beam
widths of cooled ion beams in the millimeter range have been shown. The blow-up
of the transverse beam widths and bunch lengths of electron cooled ion beams
due to diffusive heating processes like intrabeam-scattering has been measured by
varying the ion current. Furthermore, space charge effects of bunched ion beams
have been investigated in an electron cooled equilibrium.