DESIGN AND OPERATION OF THE PELLET CHARGE-EXCHANGE DIAGNOSTIC FOR MEASUREMENT OF ENERGETIC CONFINED ALPHA-PARTICLES AND TRITONS ON THE TOKAMAK FUSION TEST REACTOR

Radially resolved energy and density distributions of the confined a p articles in D-T experiments on the Tokamak Fusion Test Reactor (TFTR) are being measured with the pellet charge exchange (PCX) diagnostic. O ther energetic ion species can be detected as well, such as tritons pr oduced in D-D plasmas and H, He-3, or tritium rf-driven minority ion t ails. The ablation cloud formed by injected low-Z impurity pellets pro vides the neutralization target for this active charge exchange techni que. Because the cloud neutralization efficiency is uncertain, the PCX diagnostic is not absolutely calibrated so only relative density prof iles are obtained. A mass and energy resolving E parallel to B neutral particle analyzer (NPA) is used which has eight energy channels cover ing the energy range of 0.3-3.7 MeV for alpha particles with energy re solution ranging from 5.8% to 11.3% and a spatial resolution of simila r to 5 cm. The PCX diagnostic views deeply trapped ions in a narrow pi tch angle range around a mean value of upsilon parallel to/upsilon = - 0.048+/-10(-3). For D-T operation, the NPA was shielded by a polyethyl ene-lead enclosure providing 100X attenuation of ambient gamma radiati on and 14 MeV neutrons. The PCX diagnostic technique and its applicati on on TFTR are described in detail. (C) 1996 American Institute of Phy sics.