IV. Alpha-Particle Physics in BPX

Abstract

1V.A. INTRODUCTION A central part of the mission of the Burning Plasma Experiment (BPX) is to determine the alpha particle dynamics of self-heated fusion plasmas. While an increasing experimental and theoretical effort exists to simulate alpha-particle physics conditions, BPX will be the first fusion plasma in which the alpha power, P,, exceeds the auxiliary heating power, Pauz. A second critical condition realized in BPX will come from the existence of relatively large amounts (pa 2 0.2%) of alpha particles with ~11 2 VA&& capable of Cherenkov excitation of the Alfven spectrum of collective oscillations, which can affect fast alpha confinement. The exploration of this virgin territory can be expected to reveal unanticipated plasma physics phenomena favorably and unfavorably affecting overall performance, just as was the case when the tokamak program moved from ohmitally heated to neutral beam and radiofrequency (RF) heated plasmas. Thus, the range of alphaparticle physics results from BPX promises to be of fundamental importance for any subsequent Experimental Test Reactor (ETR). The list of currently conceptualized alphaparticle physics issues starts with the global questions of (a) what is the self-heating efficiency qa with which the alpha power at birth couples to the bulk plasma; (b) particularly in the regime pa > pauz, how does