Plasma end loss measurements in the Gas Dynamic Trap

The Gas Dynamic Trap (GDT) is an axisymmetric open trap with a large mirror ratio and a length greatly exceeding the ion mean free path of scattering into the loss cone. The authors studied axial energy and particles losses from the trap and their dependencies upon the plasma parameters inside the central cell. The main results of the experiments are the following: (1) the measured ion distribution function over energies in the expander (region behind the mirror) reasonably agrees with the model of the collisonless flow; (2) the energy flux in the expander is carried mostly by the ions, while the electron heat flux is considerably smaller; (3) the mean amount of energy carried outward by an ion-electron pair is 6.3 ± 0.1 of the electron temperature inside the trap, which is consistent with the measured total drop of the ambipolar potential 4.6 ± 0.1·Te; and (4) the measurements of axial temperature and potential profiles indicate that significant fraction of the trapped electrons may exist in the expander between the end wall and the mirror throat