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

Abstract

Coded aperture imaging of fusion source in a plasma focus operated with pure D2 and a D2-Kr gas admixture Time-integrated measurements of fusion-produced protons emitted from PF-facilities AIP Conf. Proc. 812, 237 (2006); 10.1063/1.2168831 A_ measurement of S_pin-T_R_ansfer coefficients I_n the fusion reaction D_(d⃗, p⃗)3H (ASTRID) at 55 keV AIP Conf.Abstract. Protons from the fusion reactions D( 3 He,p) 4 He and D(d,p) 3 H have been observed in a small plasma focus device operated with a 3 He-D 2 gas mixture. The partial pressures of the 3 He and D 2 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( 3 He,p) 4 He and D(d,p) 3 H reactions, were recorded simultaneously using a double-layer arrangement of CR-39 polymer nuclear track detectors (each of thickness 1000μm). 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) 3 H protons were registered on the front-most CR-39 surface and the D( 3 He,p) 4 He 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( 3 He,p) 4 He and D(d,p) 3 H proton yields were of similar magnitude, but their spatial distributions were very different. Results indicate that the D( 3 He,p) 4 He fusion was concentrated close to the plasma focus pinch column, while the D(d,p) 3 H fusion occurred at some distance from the pinch. Moreover, it appears that both the D( 3 He,p) 4 He and D(d,p) 3 H fusion yields are produced by beam-target mechanisms, with no significant thermonuclear contribution. To better understand the shape of the D(d,p) 3 H distribution, comparative experiments were performed with both a 4 He-D 2 gas mixture and pure D 2 gas. The D(d,p) 3 H distributions obtained for the 3 He-D 2 and 4 He-D 2 cases were found to be very similar, but markedly different from that obtained with pure D 2 gas. Possible explanations of these measured distributions are discussed.