Time-of-Flight detector for the ATLAS Forward Proton system

In forward physics, properly pairing particles originating from the same
collision is a significant challenge, especially in the in high pile-up
conditions at the LHC. Due to a long lever arm (hundreds of meters from the interaction point), simple track extrapolation of the leading protons is not feasible, resulting in a significant pile-up driven background for many processes of interest.

Instead, the approach of precisely timing the arrival of these forward
protons presents itself. One such system is the AFP ToF, capable of timing resolution of few tens of picoseconds, resulting in spatial resolution of the vertex position along the beamline measured in millimeters.

The design, development and performance of this unique Cherenkov-based system will be presented and the ways in which it attempts to handle the very demanding environment just a few millimeters from the LHC beam will be discussed.