Sirius is a diffraction-limited storage ring synchrotron light source at the Brazilian Synchrotron Light Laboratory (LNLS) in Campinas, São Paulo State, Brazil. It has a circumference of 518.4 metres (1,701 ft), a diameter of 165 metres (541 ft), and an electron energy of 3 GeV. The produced synchrotron radiation covers the range of infrared, optical, ultraviolet and X-ray light.
Costing R$1.8 billion, it was funded by the Ministry of Science, Technology, Innovation and Communications (Brazil) and the São Paulo Research Foundation. Discussion started in 2008, and initial funding of R$2 million was granted in 2009. Construction started in 2015, and was finished in 2018. The first electron loop around the storage ring was achieved in November 2019. Its first experiments were made during COVID-19 pandemic at MANACÁ beamline, dedicated to macromolecular crystallography.
Sirius is the second synchrotron lightsource constructed in Brazil. The first one, UVX, was a second-generation machine operated by LNLS from 1997 to 2019.