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e approximated by Maxwellian distributions, we have{av) = 3.68 x l(T 12 7- 2/3 exp(-19.947" l/3 ) cm 3 /sec,COPPI ET AL.where T is the temperature of the plasma in kiloelectron volts.The power per cubic centimeter generated by the fusion reactions canbe expressed by the relationP„ = n Dnj (av)Q„, (3)where Q a = 3.52 MeV is the energy of the alpha particles at the momentof their generation.For a plasma temperature of 10 keV, we haveP„-6 x 10 29 n D n T W/cm 3 . (4)For a plasma of relatively high density (n > 10 14 particles/cm 3 ), one ofthe principal energy losses is through the emission of bremsstrahlung,which is produced when an electron collides with a nucleus of deuteriumor tritium and undergoes a change in the direction of its motion.The equation for the power per cubic centimeter radiated by thebremsstrahlung, which is valid for a deuterium and tritium plasma, isP btcm = 2.14 x 10 M n D n T T e,/2W/cm 3 , (5)where T e is the electron temperature in kiloelectron volts. It should benoted that P a and P brem show the same dependence on the density of thecomponents of the mixture.The conditions under which the energy deposited in the plasma by thealpha particles equals the energy lost by bremsstrahlung are establishedat a temperature greater than 4.2 keV (about 5 x 10' °C), which is thegiven ideal ignition temperature (see Fig. 2). As the temperatureincreases, the rate of fusion reactions increases more rapidly than therate of the bremsstrahlung emissions; in the absence of other types ofthermal energy losses, the temperature would continue to rise.Although the effective ignition of the plasma occurs at a temperaturehigher and less easy to define (because the mechanisms of energy loss ina plasma arc not well known), the achievement of an ideal ignitiontemperature in a D-T plasma that may have a sufficiently longenergy-confinement time (m > 10 14 , as required in a reactor) is afundamental objective. In fact, heating of the alpha particles in such aplasma would play an important role, and various phenomena that aredifficult to predict theoretically could be studied experimentally. There-