Measurements of enhanced electron screening in d+d reactions under UHV conditions

Abstract

Observation of the enhanced electron screening in metallic environments is of fundamental importance for the understanding of strongly coupled astrophysical plasmas. Experimental screening energies determined by different groups for many metals are much larger than the theoretical predictions. However, a comparison between experimental and theoretical data is rather ambiguous because of the contributions of systematic errors in the experiments. One of the most important problems is the uncertainty resulting from the oxidation of the target surface during the measurements. Here, we present results of the first ultra-high vacuum (UHV) experiments studying d+d nuclear reactions in a deuterized Zr target for which the experimental discrepancies are especially large. The total cross sections and angular distributions of the 2 H(d,p) 3 H and 2 H(d,n) 3 He reactions have been measured using a deuteron beam of energies between 8 and 30 keV provided by an electron cyclotron resonance ion source with excellent long-term stability. The cleanness of the target surface has been assured by combining Ar sputtering of the target and Auger spectroscopy. In an on-line analysis method, the homogeneity of the implanted deuteron densities could be monitored also. The resulting screening energy for Zr confirms the large value obtained in a previous experiment under poorer vacuum conditions.

Material dependence of2H(d,p)3H cross section at the very low energies

“…In the usual case, Γ n and Γ p also do not depend on the target material as they are only proportional to the nuclear wave functions. The destructive interference could be also observed in the energy dependence of the enhancement factor obtained in the new UHV experiment on the Zr target [14]. The resonance contribution reduces the estimated screening energy by a constant factor, making it closer to the theoretical value.…”

Catalysis of Nuclear Reactions by Electrons

“…The effect is important in astrophysical scenarios, where almost all nuclear reactions happen at low energies and nuclei are not alone in the stellar plasma. The predicted effect was confirmed experimentally, but its measured magnitude was very often way above predictions [2][3][4][5][6][7][8][9][10][11]. Although the theory predicts an independence of electron screening on the nuclear surroundings, measurements of the same reactions in different environments gave different magnitudes of electron screening.…”

Negentropy in Many-Body Quantum Systems

“…Fusions in liquid metals and entropic correlations: the Tohoku group has measured a different effective screening potential in solid and liquid lithium, and we have recently proposed that the two-body correlation gives a negative contribution to the entropy that could explain the different screening between solid and liquid metal [38] (additional details and results from the experiments of interest can be found in [39][40][41][42][43]). …”