Alves, M.B. Liu, L. Resende, X.R. de Sá, F.H. JACoW Publishing Geneva, Switzerland 2673-5490 978-3-95450-227-1 10.18429/JACoW-IPAC2022-WEPOTK055 English 2186-2189 Contribution to a conference proceedings 2022 2022-07 https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK055 https://jacow.org/ipac2022/papers/wepotk055.pdf SIRIUS is the new storage ring-based 4th generation synchrotron light source built and operated by the Brazilian Synchrotron Light Laboratory (LNLS) at the Brazilian Center for Research in Energy and Materials (CNPEM). In ultralow emittance storage rings such as SIRIUS, the dominant contribution to the beam lifetime is due to large angle scattering between electrons within the same bunch, namely the Touschek effect. We used the strategy of storing two bunches simultaneously with different currents to measure their Touschek lifetime independently of other contributions, such as gas scattering. The measurements were carried out in different conditions of bunch current and RF voltage to compare the experimental results with those expected from theory and simulations for SIRIUS.