Shashkov, Ya.V. Gusarova, M. Lalayan, M.V. Samarokov, N.Yu. JACoW Publishing Geneva, Switzerland 2673-5539 978-3-95450-240-0 10.18429/JACoW-RuPAC2021-WEPSC13 English 367-369 HOM cavity GUI impedance damping Contribution to a conference proceedings 2021 2021-10 https://doi.org/10.18429/JACoW-RuPAC2021-WEPSC13 https://jacow.org/rupac2021/papers/wepsc13.pdf Preliminary results on accelerating cavities for USSR-4 facility (also known as SYLA - SYnchrotron and free-electron LAser) project are presented. This facility is under development by collaboration hosted by National Research Center "Kurchatov Institute". SYLA is synchro-tron radiation facility based on injector linac and 6 GeV storage ring. Beam energy loss in storage ring is to be compensated by several modified pillbox cavities. Cavity geometry features, its operation frequency choice and induced HOM parameters are discussed. HOM damping technique using corrugated cylindrical waveguides were studied. Longitudinal impedance values of HOM are presented for initial accelerating cavity and structure with waveguides.