[Triumf-seminars] TRIUMF Seminar today at 14:00

[postmaster@admin.triumf.ca]

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Date/Time: Thu 2005-09-29 at 14:00

Location:  Auditorium          

Speaker:   Armin Huke (Technische Universitaet Berlin, Germany)

Title:     The d+d Reactions in Metallic Environments and their Relation to "Cold Fusion"

Abstract: An overview of our experiments and their results for the screening energies will be presented [1]. The measurements of the mirror reactions 2H(d,p)3H and 2H(d,n)3He were performed with a electrostatic accelerator at incident deuteron energies between 5 and 60 keV at different self-implanted target materials. The resulting screening energy values are about one order of magnitude larger compared to gas target experiments and exceed significantly the theoretical predictions. A thorough investigation of the processes in the targets under ion irradiation shows that there are multi-parameter collateral effects which are crucial for the correct interpretation of the observed enhancements. They mainly originate from target surface contaminations due to residual gases in the vacuum as well as from inhomogeneities in the deuteron density distribution in heterogeneous targets. For the special situation of deuterium in the metallic environment an adapted analysis method has been developed beyond the standard procedures. Experimental evidence for the influence of such effects and a mathematical model for their assessment are given and compared with the results of other groups. Aside the angular distributions and the neutron-proton branching ratio of the two mirror reactions have been investigated. Whereas the experimental results obtained for transition metals do not differ from those known from gas-target experiments, an enhancement of the angular anisotropy in the neutron channel and a quenching of the neutron-proton branching ratio have been observed for the (earth)alkaline metals Li, Sr and Na at deuteron energies below 20 keV. Both effects can be explained assuming an induced adiabatic polarization of the reacting deuterons in the crystal lattice.

We also present a first effort for a numerical model of the electron screening effect in metallic lattices based on an ab-initio Hartree-Fock simulation. An analytical model within an improved
dielectric function theory describes correctly the observed target material dependence of the screening energies [2], underestimating, however, the absolute values by about a factor of 2.

The consequences of our experimental results and theoretical calculations for the credibility and understanding of the meanwhile sustained "cold fusion" observations will be discussed.

Literature:
[1] Europhys. Lett. 54(2001)449
[2] Europhys. Lett. 68(2004)363



Stimulants available 15 minutes before the talk.

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