A time-of-flight (TOF) detector is a

particle detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nu ...

which can discriminate between a lighter and a heavier

elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions ( quarks, leptons, a ...

of same momentum using their

time of flight Time of flight (ToF) is the measurement of the time taken by an object, particle or wave (be it acoustic, electromagnetic, etc.) to travel a distance through a medium. This information can then be used to measure velocity or path length, or as a w ...

between two scintillators. The first of the scintillators activates a clock upon being hit while the other stops the clock upon being hit. If the two masses are denoted by

m_1

and

m_2

and have velocities

v_1

and

v_2

then the time of flight difference is given by :

\Delta t = L\left(\frac-\frac\right)\approx \frac(m_1^2-m_2^2)

where

L

is the distance between the scintillators. The approximation is in the relativistic limit at momentum

p

and

c

denotes the speed of light in vacuum.

See also