A large evacuated toroidal ring forming a part of some particle accelerators. The rings are designed like synchrotrons, except that they do not accelerate the particles circling within them but supply just sufficient energy to make up for losses (mainly synchrotron radiation). The storage rings are usually built tangentially to the associated accelerator so that particles can be transferred accurately between them. At CERN in Geneva, two interlaced storage rings are used, containing protons rotating in opposite directions. At the intersections very high collision energies (up to 1700 GeV) can be achieved.