In tokamak experiments, the fusion triple product nTτE and a D-T equivalent Q in D-D reactions have reached record values 1.5×1021 keV.s.m-3 and 1.25 respectively in JT-60U. Successful D-T experiments have been carried out in JET and TFTR and a record of 16 Megawatts of fusion power has been produced for several seconds in JET. Figure 1 shows the progress of fusion research over the last four decades in terms of the fusion triple product and fuel temperature achieved.
Fusion has in fact had quite an impressive progress comparable to those of other research and development fields over the last few decades. Figure 2 shows a comparison of progress in fusion compared to development of semiconductor chips and accelerator physics over the same period. However, unlike the progress in semiconductor chips, the effect of which is quite visible to the society, fusion will be fruitful only when the reactors produce net extractable energy. ITER will be the first machine to produce power in substantial excess (10 times) of the input power.