Atomic collision processes limiting the efficiency of negative ion beam production relevant to fusion plasma heating

Details

Supervisors

Urbain, Xavier

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil physicien

Abstract

The International Thermonuclear Experimental Reactor (ITER) experiment aims to demonstrate the feasibility of fusion energy. To reach ultra-high temperatures required to overcome the Coulomb repulsion between nuclei and initiate their fusion, plasma confined in a tokamak is heated up by momentum transfer from a highly energetic neutral beam. This neutral beam is created by neutralization of electrostatically accelerated negative ions D-. This pushes the need for efficient negative ions sources. Inside these sources, a plasma is created in a Deuterium gas. This plasma is composed of many different compounds: neutrals (D, D2), anions (D-), cations(D+, D2+, D3+) all possibly in an excited state. This master thesis focuses on the mutual neutralization of D2+ with D- that happens in the plasma of negative ions source. The experimental spectrum of the kinetic energy released by this mutual neutralization reaction is compared to computational and theoretical results. The goal is to find out the dominant output channel between D2* + D and D2 + D*. Results tend to point out the dominance of the first one with the favored electronically excited states D2* being the singlets 3s 1Σg+(HHbar), 3d 1Σg+(GK) and 3p 1Σu+(B'). The output channel D + D + D has also been studied from measurements performed with a three-body detection system. Analysis of the experimental kinetic energy release spectrum reveals the passage by some triplet states of D2* which dissociates by radiative coupling to the dissociative state D2(b 3Σu+).