Screening and resonance enhancements of the ² H(d, p) ³ H reaction yield in metallic environments

Abstract

The reaction cross-section has been measured for deuteron energies below 25 keV in a deuterized Zr target under improved ultra-high-vacuum conditions and controlled target surface contamination. The increase of reaction enhancement factors towards lower energies is much weaker than that determined before and can result not only from the electron screening effect but also from a suggested 0+ threshold resonance in 4He. The cross-section calculations performed within the T-matrix approximation enable to estimate a coherent resonance contribution and explain the observed energy dependence of the enhancement factors. Additionally, indications for the increase of the screening energies due to impurities at the target surface could be found.

Electron Screening Effect in Nuclear Reactions in Metallic and Gaseous Targets

“…Using the screening energy U e as a single parameter in the fit, the value of (120 ± 7) eV was obtained. This value is much smaller than that determined previously for Zr and closer to the theoretical expectation of 80 eV [11]. However, precise data analysis shows that the energy dependence of the experimental enhancement factors is not well-described by a simple screening curve.…”

“…The low-energy points are underestimated, whereas high-energy points are overestimated. The lighter/red fit provides a χ 2 value of 1.6 per data point, at the confidence level of above 95%, which is two times smaller than 3.2 obtained for the darker/blue fit, without the resonance contribution [11].…”

“…where a and µ stay for the channel radius and the reduced mass, respectively, k is the wave number and dimensionless, reduced width |θ| 2 is equal to 1 for a single-particle resonance. The total cross section, including the interference effects with broad overlapping resonances, for which the phase shift can be kept constant, is given by [11] σ…”

“…Here, the 2 H(d, p) 3 H reaction cross section has been analysed for data collected in a deuterated Zr target under improved ultra-high-vacuum conditions [11]. Moreover, the influence of an additional 0 + threshold resonance state in 4 He compound nucleus is considered in analysis of cross-section enhancement for 2 H(d, p) 3 H reaction in both, metallic target experiments, mentioned above, as well as in gaseous target experiments performed over two decades ago [12].…”

Correlated states and nuclear reactions: An experimental test with low energy beams

“…Energy spread of either the target or impinging nuclei is deemed to be responsible for these effects, although the possible generating mechanisms, such as thermal motion, vibrations inside an atomic, molecular, or crystal system, or a finite beam energy width, seem quite negligible at energies down to ≈10 KeV. Other groups [2] have reported on a strong screening enhancement of the D-D fusion reactions in some metals, but the presence of narrow threshold resonances, as suggested by the authors, seems not a sufficient explanation. In particular, a team at the ECRIS facility of the University of Stettin is planning to make measurements at deuteron energies below 5 keV for a better understanding of the observed phenomena [3].…”