Energy Loss Processes in ZETA

The energy lost from ZETA discharges, in deuterium and argon by radiation, plasma particles and non-thermal electrons, has been investigated experimentally over a wide range of conditions. Two definite regimes of energy loss have been established. These regimes are determined principally by the pressure at which the machine is operated. At high pressures (5 microns) line radiation from impurities is the dominant loss process and under certain discharge conditions accounts for all the energy fed into the discharge. Theoretical considerations are presented to show that the observed impurity content of 10 11 atoms per cubic centimetre can account for the radiation loss. At lower pressures (0.5 micron) the energy is lost by particles, firstly by plasma which is not efficiently confined and secondly by fast electrons which are accelerated at the termination of the current pulse and strike the tube walls with about 8 kev of energy. The results reported are related to energy loss observations made by workers with other stabilized pinch devices.