Particle identification using time of flight
This review will focus on the use of time-of-flight (TOF) techniques to identify particles emerging from high-energy particle interactions. The curvature of tracks of charged particles in a magnetic field depends on its momentum and charge. The momentum is the product of the mass × velocity; thus if the velocity is also measured, the mass can be calculated. TOF is essentially just this, the measurement of the velocity. We will consider recent advances within this field; this was brought on by the development of the multigap resistive plate chamber (MRPC). Since the MRPC has become the new standard technology in the field, a good part of this review will consider the operation of this detector. The ALICE TOF is a large array that makes use of the MRPC detector, thus this array will be used as an example and discussed, highlighting the choices made when designing the array. The MRPC has exceptional operation characteristics; in large part due to powerful space charge effects that are especially strong in small gas gaps. The electronics in use currently will be briefly covered, but this is a fast moving field so only some general comments will be made pointing towards development needed for a next generation of TOF arrays.