Also known as containment time.
The length of time for which particles are confined within the plasma, denoted by τ (the Greek letter tau). One of the three critical parameters for fusion plasmas, along with temperature and number density, that form the triple product. Typical current values at JET are on the order of a second, and at ITER should be around four seconds.
The confinement time should not to be confused with the length of a plasma pulse – during a single pulse many particles will be sucked into, circulated within and then escape from the plasma.