Effect of the loss cone on confinement in toroidal helical devices

The paper present an analysis of the loss cone boundary in phase space for toroidal helical devices. The effects of the radial electric field and the modulation of the helical field ripple are taken into account. The minimum energy of particles entering the loss cone is calculated. Modulation of the helical ripple is not always effective in reducing the loss when a radial electric field is present. The particle loss due to the loss cone is estimated in the collisionless limit. The impact of the radial electric field on the loss cone is discussed. It is more difficult to find a solution in the case of a positive radial electric field, which is required for the high ion temperature mode. This difficulty is great for systems with a small helical field ripple.