Abstract
A numerical analysis of the classical loss mechanisms in the heliac TJ-II is presented. By using a guiding centre orbit code in flux co-ordinates, it is found that collisionless direct losses can be eliminated by electric drift effects for potentials of the order of the ion temperature. Neoclassical losses resulting from the interaction of collisions and complex orbits are calculated by solving the drift kinetic equation. When electric drifts are included, the resulting transport coefficients are comparable to those of a tokamak with the same aspect ratio and a rotational transform equal to the transform per field period in TJ-II. In the absence of auxiliary heating, the expected energy confinement time in TJ-II is 2.5 ms, and it decreases with increasing ion temperature.