Studies of electron cooling at DESY

A possibility to improve the luminosity in hadron colliders is to apply ele ctron cooling. For the e-p and possibly in the future for e-ion a cooling s cheme is proposed for the HERA collider which improves the brightness of th e hadron beam in two steps. In a first step the hadron beam is cooled at an energy of 15-20 GeV in the pre-accelerator PETRA. In a second step the had rons are cooled at top energy in HERA, mainly to maintain the beam quality. The first part of the cooler in PETRA consists of a thermionic gun which d elivers electron bunches of 120 keV. These bunches are then compressed so t hat they fit into a 208 MHz travelling wave linac where they are accelerate d to an energy of 10 MeV. Gun, compressor, and linac are surrounded by a so lenoid so that emittance growth is avoided especially at the low energy end . In order to reduce the energy spread of the electron beam and to lengthen it, the electrons run through a decompressor before they are brought toget her with the hadron beam in a 40 m long cooling section which is again surr ounded by a solenoid. In this paper a schematic layout of the system will b e presented and simulation results of the first part of the cooler will be shown. The cooler in HERA consists of a small electron storage ring with tw o long straight sections. It is shown that all requirements of such a ring running at an energy between 180 and 450 MeV can be met to fight emittance growth in case of light hadron beams (protons) and to cool heavy ions suffi ciently fast. (C) 2000 Elsevier Science B.V. All rights reserved.