Historical research guide · 0472 · 2001
Enhancement of the electron screening effect for d + d fusion reactions in metallic environments
K. Czerski · A. Huke · A. Biller · P. Heide · M. Hoeft · G. Ruprecht
In one minute
Two deuterium nuclei have to get past each other’s electric repulsion before they can fuse, and the electrons around them help by cancelling part of that charge — the screening effect. In a star the screening is done by hot plasma. Konrad Czerski, Armin Huke and their colleagues at the Technical University of Berlin asked what a metal does instead, since a metal is a cold, dense electron gas sitting right there at room temperature. They used the beam itself to implant deuterium into aluminium, zirconium and tantalum, fired deuterons at energies from 5 to 60 keV, and measured both branches of the reaction: the one that yields a proton and tritium, and the one that yields a neutron and helium-3. They took angular distributions as well as thick-target yields, because the analysis depends on both. The screening energy that comes out is about ten times what the same reaction gives in deuterium gas, larger than theory predicted, and different from metal to metal.
Connection
Chapter 12 rests on a published, checkable fact — that the solid a deuteron sits in changes the barrier it has to cross — and this is the measurement that opened the file, the first of the Berlin group’s two campaigns and the paper every later screening result is compared against. The clear dependence on which metal is used is the part that matters most for anyone building something: it means the material is a design parameter, not a container. The rest of the group’s programme is on this site — the detailed 2007 account of the same measurements at /library/stm-2808bb6545, the 2008 Physical Review C survey across metals at /library/stm-48bf5f3355, Czerski’s 2022 threshold-resonance Letter at /library/stm-e327a58a98, and the 2025 Szczecin result showing that trace oxygen doubles the screening energy at /library/stm-f5eb4f4d1a.
From the source
Angular distributions and thick target yields of the two fusion reactions — deuterium plus deuteron giving a proton and tritium, and deuterium plus deuteron giving a neutron and helium-3 — were measured on deuterons implanted in three different metal targets, aluminium, zirconium and tantalum, for beam energies ranging from 5 to 60 keV.Abstract; the measurement is the group’s campaign I
The experimentally determined values of the screening energy are about one order of magnitude larger than the value achieved in a gas target experiment.Abstract, second sentence
The screening energies this measurement yields are 322 plus or minus 15 electronvolts for tantalum, 297 plus or minus 8 for zirconium and 190 plus or minus 15 for aluminium, against 25 plus or minus 5 electronvolts for a gaseous deuterium target.The campaign I values as tabulated by the same group in Huke, Czerski and Heide 2007, Table 1, with the gas-target comparison attributed there to Greife and colleagues
A clear target material dependence of the screening energy has been established, so the size of the effect is a property of the host metal rather than of the reacting pair alone.Abstract, final sentence
The measured screening energies are significantly larger than the theoretical predictions, which leaves the size of the effect in metals as the open quantity — the one a later theory, or a cleaner surface, has to account for.Abstract, second sentence
The way in
https://doi.org/10.1209/epl/i2001-00265-7How to cite it
K. Czerski, A. Huke, A. Biller, P. Heide, M. Hoeft, G. Ruprecht (2001) Enhancement of the electron screening effect for d + d fusion reactions in metallic environments doi:10.1209/epl/i2001-00265-7