Fast ion heating due to REB-induced plasma turbulence

Experimental investigation of the relativistic electron beam (REB) energy transfer to the ion plasma component in the REBEX machine is reported The presented estimates of the ion temperature are based on the intracavity laser spectroscopic measurements of the H a line profiles and on the time-of-flight analysis of fast charge-exchange neutrals. The results of optical diagnostics indicate that ions gain energy during the 100 ns REB injection, e.g. much faster than it would correspond to the collisional energy transfer from the REB-heated plasma electrons. The mean energy of the plasma ion component at the end of the beam injection is comparable or even higher than the electron temperature of the bulk. A turbulent mechanism which might be responsible for the observed fast ion heating is discussed