The existing GSI ring accelerator SIS18, as the future SIS100, also contains a collimator system to control ionisation losses and to stabilize residual gas pressure. It consists of 10 pairs, which are located in beam direction behind the dipoles. (There are no collimators installed in section 6 and 10). Due to their gold-coating, the fixed blocks have a low desorption rate. They are mounted electrically insulated, so that electric current caused by the impinging ions can be measured.

Additionally, there are three movable collimators in SIS18. They are needed for machine protection of the septa and to control systematic losses.

Responsibility for the collimation system lies with the Synchrotrons Special Installations group.