Three-dimensional simulations of ion dynamics in the plasma of an electron cyclotron resonance ion source

The ion production in an ECRIS is modelled using a particle-in-cell Monte-Carlo collision code in a three-dimensional geometry. Only the heavy particles (ions and atoms) are tracked, with the electron density determined from the requirement of quasi-neutrality, and the electron temperature is a free parameter. The electric fields in the plasma are assumed to be negligibly small, and the ion confinement due to a "potential dip" is neglected. It is found that experimentally observed features of ECRIS plasma are closely reproduced by the code, including the charge-state-distributions of extracted ion beams and sputtering patterns inside the source. The isotope anomaly is observed for the mixture of 20Ne + 22Ne isotopes, and some explanation for the effect is given. Possible connection between the wall-coating effect and parameters of the fast atoms created in collisions of the ions with the walls is discussed.Comment: 29 pages, 13 figure

Adiabatic spin transitions in polarized-proton sources

A detailed study of weak- and strong-field radio-frequency (RF) transitions used in polarized-proton sources to transfer electronic to nuclear polarization is presented. Generalized Landau-Zener theory is used to derive analytical expressions for the various transition efficiencies, which are compared to numerical solutions of the corresponding optical Bloch equations. (C) 2004 Elsevier B.V. All rights reserved

Radiocarbon in food: a non-problem of health effects

Recently it has come to our attention that a paper was published in this journal entitled ‘‘recycling greenhouse gas fossil fuel emissions into low radiocarbon food products to reduce human genetic damage’’. In this article, it is argued that food grown in a greenhouse is healthier for people, when the greenhouse is fertilised with CO2 prepared from fossil fuels. In this comment, however, we argue that the effect on human health is completely negligible.