Global energy balance and density limit on CASTOR tokamak

Total radiative power losses have been measured by a pyroelectric detector on the CASTOR tokamak in a broad range of plasma parameters. It has been shown that while for the low density operation (n _e <10 ¹⁹ m ^–3 ) the most important channel of energy losses is a thermal conductivity, the high density regimes are radiation dominated. Using a simple analytic energy balance model, the connection between such a high level of radiation and shrinking of the current channel resulting in an enhanced MHD activity is discussed.The authors would like to thank Dr. R. Klíma for many helpful and stimulating discussions.