Understanding the electron screening effect in the laboratory is critical for a correct interpretation of low-energy nuclear reactions in stars. A new measurement of this effect has been carried out at the 100 kV accelerator of the
Ruhr-Universität Bochum. The d(d,p)t reaction has been studied on 56 elements in total. For insulators and semiconductors Ue values in agreement with gas target were found, whereas Ue values much larger have been observed for metals. Experimental
results of anomalous enhancements have been interpreted in terms of the Debye plasma model applied to quasi-free metallic electrons.
Also the variation of hydrogen solubility in the samples as a function of temperature has also been measured, showing an anti-correlation with screening enhancement as expected. Within this model, the deduced number of valence electrons per metallic atom
also agrees with the corresponding number from the Hall coefficient.