Calculations of Energy Losses due to Atomic Processes in Tokamaks with Applications to the ITER Divertor

摘要

Reduction of the peak heat loads on the plasma facing components is essentialfor the success of the next generation of high fusion power tokamaks such asthe International Thermonuclear Experimental Reactor (ITER) 1 . Many presentconcepts for accomplishing this involve the use of atomic processes to transferthe heat from the plasma to the main chamber and divertor chamber walls andmuch of the experimental and theoretical physics research in the fusion programis directed toward this issue. The results of these experiments andcalculations are the result of a complex interplay of many processes. In orderto identify the key features of these experiments and calculations and therelative role of the primary atomic processes, simple quasi-analytic models andthe latest atomic physics rate coefficients and cross sections have been usedto assess the relative roles of central radiation losses throughbremsstrahlung, impurity radiation losses from the plasma edge, charge exchangeand hydrogen radiation losses from the scrape-off layer and divertor plasma andimpurity radiation losses from the divertor plasma. This anaysis indicates thatbremsstrahlung from the plasma center and impurity radiation from the plasmaedge and divertor plasma can each play a significant role in reducing the powerto the divertor plates, and identifies many of the factors which determine therelative role of each process. For instance, for radiation losses in thedivertor to be large enough to radiate the power in the divertor for high powerexperiments, a neutral fraction of 10-3 to 10-2 and an impurity recycling rateof netrecycle of ~ 10^16 s m^-3 will be required in the divertor.