Fast ion losses in the W7-AS stellarator

A new probe for the detection of fast escaping ions has been installed and operated at the W7-AS stellarator. Fast ions generated from neutral beam in jection or ion cyclotron heating were used to study the fast ion confinemen t properties of the partially drift-optimized magnetic field structure as w ell as losses induced by magnetohydrodynamic perturbations. The design of t he probe is based on the alpha -particle detectors of the Tokamak Fusion Te st Reactor using scintillator plates and allows the detection of co-and cou ntergoing ions simultaneously in a wide range of gyroradii and pitch angles . (C) 2001 American Institute of Physics.