From the fusion triple product it is known that both temperature and energy confinement time of the fusion fuel must be high enough for fusion ignition. It was however found that that the energy confinement time scales inversely with applied power. Prior to the discovery of H-mode, all tokamaks operated in what is now called the L-mode, or low-confinement mode. The L-mode is characterized by relatively large amounts of turbulence, which allows energy to escape the confined plasma. The energy confinement time τ τ E for tokamak L-mode is given empirically by the ITER89-P scaling expression: