Measurement and control of end loss electrons from the GAMMA 10 tandem mirror

This paper describes characteristics of endless electrons (ELE's) from a ta ndem minor. Without electron cyclotron resonance heating (plug ECRH), ELE's issue from an ICRF heated hot ion plasma Their temperature increases with the hot ion diamagnetism. Drag heating of electrons on hot ions balances wi th axial loss due to Coulomb scattering. Landau damping of an Alfven ion cy clotron wave is also observed in this phase. On application of the plug ECR H, an intense loss flux of warm electrons is generated. The axial heat flow carried by the warm electrons significantly increases. Control of the axia l flux of the warm electrons is tried A highly transparent mesh is put up o ver an end plate and a bias voltage negative to the end plate is applied to the mesh. Then secondary electrons emitted from the end plate are suppress ed and the loss flux of the warm electrons decreases to about one third of that without the mesh bias. This reduction factor is much smaller than the value expected from the rate of ion plugging. A possible cause of this is a n ion current through a plasma behind the end plate.