Alpha particle losses from Tokamak Fusion Test Reactor deuterium–tritium plasmas

D S Darrow,C E Bush,R F Heeter,E D Fredrickson,D A Spong,E J Strait,N J Fisch,R B White,R Majeski,C K Phillips,Z Chang,C Z Cheng,M H Redi,E F Jaeger,S S Medley,H H Duong,S J Zweben,M C Zarnstorff,J R Wilson,M Murakami,H W Herrmann,G Y Fu,W W Heidbrink,E Ruskov,G Taylor,S H Batha ,Jun Fang ,K L Wong ,Robert Fischer ,R Budny ,Mark Herrmann ,М П Петров ,K W Hill ,R A James

doi:10.1063/1.871983

Abstract

Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium–tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario.

Highlights

The Tokamak Fusion Test ReactorTFTR1 has been operating with deuterium–tritiumDTplasmas since December 1993.2 The higher fusion rates of the DT reaction have provided an abundant source of energetic alpha particles
Since the energy stored in the alpha population will total hundreds of megajoules in a reactor such as the International Thermonuclear Experimental ReactorITER,3,4 knowledge of alpha particle loss processes is vital to designing the plasma facing components so that they will not be damaged by energetic alpha particle losses
The alpha flux measured in the 90° detector from quiescent DT supershots in TFTR is in good agreement with the first orbit loss model over the entire range

Summary

INTRODUCTION

The Tokamak Fusion Test ReactorTFTR1 has been operating with deuterium–tritiumDTplasmas since December 1993.2 The higher fusion rates of the DT reaction have provided an abundant source of energetic alpha particles This population has afforded the chance to make measurements and understand the physics of alpha particles, their losses from the plasma. Radiofrequency wave-induced losses arise from interactions between plasma waves and the alphas Such losses result from wave-driven diffusion of alphas into existing loss cones, e.g. first orbit or stochastic ripple diffusion. These detectors are situated 90°, 60°, 45°, and 20° below the outer midplane.

CLASSICAL LOSSES

MHD AND COLLECTIVE LOSSES

RF WAVE-INDUCED LOSS

Findings

CONCLUSIONS AND FUTURE WORK