Ola Kenji Forslund

submitter : Positron Manipulation and Positronium Laser Excitation in AEgIS

Production of antihydrogen by using the charge exchange reaction, as proposed by AEgIS (Antimatter Experiment: gravity, Interferometry, Spectroscopy), requires the formation of a dense cloud of positronium atoms excited to Rydberg states. In this work, the recent advances in AEgIS towards this result are described. Namely, the manipulation of positrons to produce bunches containing more than 108 particles and the laser excitation of positronium to Rydberg states, using n=3 as intermediate level, are presented.

Scattering from dielectric frequency selective structures

A plane wave impinges on a laterally double-periodic inhomogeneous lossy dielectric structure. Using a wave splitting approach, and an expansion of the fields and permittivity in global and local basis functions, respectively, the scattered fields are determined via a propagator. The formulation is useful for a permittivity which varies abruptly as well as in a continuous fashion. A subdomain basis for the constitutive parameter is preferred to an entire domain basis. Calculated results are compared with experimental data for a slab with domains of a piecewise homogeneous permittivity. The agreement is good considering the error sources in the experiment. The results are in a special case also compared with results obtained by an entirely different method showing very good agreement. The method is also used on a pyramidal absorber-like structure. (Less)