CERN — the European Organization for Nuclear Research

The TOTEM detectors: Roman pots

The Roman Pots (RPS) are special movable devices inserted directly into the beam vacuum pipe and supported by bellows, which are compressed as the pots are pushed towards the particles circulating inside the vacuum pipe. They are called 'Roman' because they were first used by a group of Italian physicists from Rome, in the early 1970s, to study similar physics at CERN's ISR (Intersecting Storage Rings). They are called 'Pots' because the delicate detectors, able to localize the trajectory of protons close to the beam within 1 mm (with a precision of around 20 micrometers), are housed in cylindrical vessels. In the TOTEM experiment, every Roman Pot station is composed of two units, separated by a distance of 4 meters, each unit consisting of two pots in the vertical plane approaching the beam from above and below, and one that moves horizontally. They are placed very far from the interaction point (about 147m and 220m), on both sides of the IP5 interaction point.