Studies of Fusion Protons from a 3He-D2 Plasma Focus using Nuclear Track Detectors

• Published in: AIP conference proceedings 2006-01, Vol.875 (1), p.35-40
• Main Authors: Springham, S V, Sim, T H, Lee, P, Rawat, R S, Shutler, P M E, Tan, T L, Patran, A, Lee, S
• Format: Article
• Language: English
• Subjects: DEUTERIUM TARGET; FUSION YIELD; HELIUM 3; HELIUM 3 BEAMS; HELIUM 3 REACTIONS; HELIUM 4; NUCLEAR PHYSICS AND RADIATION PHYSICS; PARTIAL PRESSURE; PLASMA DIAGNOSTICS; PLASMA FOCUS; PLASMA FOCUS DEVICES; PROTONS; SPATIAL DISTRIBUTION; TRITIUM
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.2405899

Protons from the fusion reactions D(3He,p)4He and D(d,p)3H have been observed in a small plasma focus device operated with a 3He-D2 gas mixture. The partial pressures of the 3He and D2 gasses were in the ratio of 2:1, corresponding to an atomic number ratio of 1:1. Two groups of protons with energies of approximately 16MeV and 3MeV arising from the D(3He,p)4He and D(d,p)3H reactions, were recorded simultaneously using a double-layer arrangement of CR-39 polymer nuclear track detectors (each of thickness 1000mum). As a result of the very different ranges of 16MeV and 3MeV protons, and the particle registration properties of CR-39, the D(d,p)3H protons were registered on the front-most CR-39 surface and the D(3He,p)4He protons were registered on the back-most surface of this double-layer configuration. A pinhole camera, containing the CR-39 detectors, was situated on the forward plasma focus axis in order to image the emission zones of protons for both fusion reactions. It was found that the D(3He,p)4He and D(d,p)3H proton yields were of similar magnitude, but their spatial distributions were very different. Results indicate that the D(3He,p)4He fusion was concentrated close to the plasma focus pinch column, while the D(d,p)3H fusion occurred at some distance from the pinch. Moreover, it appears that both the D(3He,p)4He and D(d,p)3H fusion yields are produced by beam-target mechanisms, with no significant thermonuclear contribution. To better understand the shape of the D(d,p)3H distribution, comparative experiments were performed with both a 4He-D2 gas mixture and pure D2 gas. The D(d,p)3H distributions obtained for the 3He-D2 and 4He-D2 cases were found to be very similar, but markedly different from that obtained with pure D2 gas. Possible explanations of these measured distributions are discussed.