Fedotov, A.V. Blaskiewicz, M. Fischer, W. Kayran, D. Kewisch, J. Seletskiy, S. Tuozzolo, J.E. JACoW Geneva, Switzerland 978-3-95450-180-9 10.18429/JACoW-NAPAC2016-WEA4CO05 English 867-869 WEA4CO05 ion electron cavity cathode emittance Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-NAPAC2016-WEA4CO05 https://jacow.org/napac2016/papers/wea4co05.pdf A Low Energy RHIC electron Cooler (LEReC) is presently under construction at BNL to improve the luminosity of the Relativistic Heavy Ion Collider (RHIC). The required electron beam will be provided by a photoemission electron gun and accelerated by a RF linear accelerator. As a result, LEReC will be first bunched beam electron cooler. In addition, this will be the first electron cooler to cool beams under collisions. The achievement of very tight electron beam parameters required for cooling is very challenging and is being addressed by a proper beam transport and engineering design. In this paper, we describe accelerator physics requirements, design considerations and parameters, as well as associated challenges of such electron cooling approach.