Sulimov, A.A. Ermakov, A. Gresele, A. Thie, J.H. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-THPB068 English 1277-1278 THPB068 HOM damping cavity simulation dipole Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-THPB068 http://srf2015.vrws.de/papers/thpb068.pdf Some Higher Order Modes (HOM) pass bands were controlled during cryo-tests at DESY for the European XFEL cavities. The second monopole mode (TM011) showed most instabilities and suppression degradation. The authors will explain this phenomenon on the example of cavity CAV00553 and present the practical method of TM011 damping improvement.