Measurement of correlation-enhanced collision rates using pure ion plasmas

This paper presents the first direct experimental measurements of the Salpeter enhancement of collisions due to particle correlations. The perpendicular-to-parallel collision rate nu(perpendicular to parallel to) is measured in laser-cooled pure ion plasmas, spanning the regimes from weak to strong magnetization, and from weak to strong particle correlations. The abrupt suppression of collisions in the strongly magnetized regime of T less than or similar to 10(-3) eV is observed, mitigated by the Salpeter enhancement when correlation effects become significant. This nu(perpendicular to parallel to) enhancement due to correlations is directly analogous to the enhancement of fusion collisions in hot dense stellar plasmas. The measured collisional enhancement is approximately exp(Gamma), where Gamma is the correlation parameter, and this is quantitatively consistent with analytical estimates based on thermal equilibrium shielding and correlations. (C) 2010 American Institute of Physics. [doi:10.1063/1.3293131]