The Forward Proton Detector is a series of momentum spectrometers
which make use of machine magnets along with points measured on
the track of the scattered proton (or anti-proton)
to calculate its momentum
and scattering angle (
).
The points are measured using detectors located in Roman pots, which
are typically stainless steel pots or containers that allow the detectors
to function close to the beam.
Particles traverse thin steel windows at the entrance and exit of each pot.
The pots are remotely controlled and
can be moved close to the beam (within a few mm)
during stable beam conditions and retracted otherwise.