Fitterer, M. Bruce, R. Papadopoulou, S. Papotti, G. Pellegrini, D. Redaelli, S. Stancari, G. Valishev, A. Valuch, D. Wagner, J.F. JACoW Geneva, Switzerland 978-3-95450-180-9 10.18429/JACoW-NAPAC2016-WEA1CO04 English 651-654 WEA1CO04 ion simulation experiment emittance electron Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-NAPAC2016-WEA1CO04 https://jacow.org/napac2016/papers/wea1co04.pdf Collimation with hollow electron beams or lenses (HEL) is currently one of the most promising concepts for active halo control in HL-LHC. In previous studies it has been shown that the halo can be efficiently removed with a hollow electron lens. Equally important as an efficient removal of the halo, is also to demonstrate that the core stays unperturbed. In this paper, we present a summary of the experiment at the LHC and simulations in view of the effect of the HEL on the beam core in case of a pulsed operation.