While the purpose of geologic storage in deep salineformations is to trap greenhouse gases underground, the potential existsfor CO2 to escape from the target reservoir, migrate upward alongpermeable pathways, and discharge at the land surface. In this paper, weevaluate the potential for such CO2 discharges based on the analysis ofnatural analogs, where large releases of gas have been observed. We areparticularly interested in circumstances that could generate sudden,possibly self enhancing release events. The probability for such eventsmay be low, but the circumstances under which they occur and thepotential consequences need to be evaluated in order to designappropriate site-selection and risk-managementstrategies. Numericalmodeling of hypothetical test cases is suggested to determine criticalconditions for large CO2 releases, to evaluate whether such conditionsmay be possible at designated storage sites, and, if applicable, toevaluate the potential impacts of such events as well as designappropriate mitigation strategies.

Computer simulation studies of the stability and transport properties of trapped non-neutral plasmas require the numerical realization of a three-dimensional plasma distribution. This paper presents a new numerical method for obtaining, without an explicit model for physical collisions in the code, a low noise three-dimensional computational equilibrium distribution. This requires both the loading of particles into an idealized distribution and the relaxation from that distribution toward an approximate numerical equilibrium. The equilibrium can then be modified through a slow change of system parameters, to generate other equilibria. In the present work we apply this method to a UC Berkeley experiment on electron confinement in magnetic geometries appropriate for the ALPHA anti-hydrogen experiment, using the three-dimensional Particle-In-Cell code WARP. WARP's guiding center mover and its option to switch between different solvers during a simulation are highly valuable because they speed up the simulations; they enable the practical use of the new technique for generating numerical equilibrium states of trapped nonneutral plasmas.

We have measured the X-ray absorption and X-ray magnetic circular dichroism (XMCD) at the Mn L{sub 3,2} edges in ferromagnetic Ga{sub 1-x}Mn{sub x}P for 0.018 {le} x {le} 0.042. Large XMCD asymmetries at the L{sub 3} edge indicate significant spin-polarization of the density of states at the Fermi energy. The temperature dependence of the XMCD and moment per Mn of 2.67 {+-} 0.45 {mu}{sub B} calculated using sum rules are consistent with magnetometry values. The spectral shapes of the X-ray absorption and XMCD are nearly identical with those for Ga{sub 1-x}Mn{sub x}As indicating that the hybridization of Mn d and anion p states is similar in the two materials.