Wiener, A. (2020). Designing a Coplanar waveguide to manipulate the scattering length in a caesium BEC [Diploma Thesis, Technische Universität Wien]. reposiTUm. https://doi.org/10.34726/hss.2020.75040
This work aims at implementing a proposal to manipulate the s-wave scattering length of caesium atoms with the magnetic component of a microwave eld via Fano-Feshbach resonances. This would open the possibility of controlling the attractive or repulsive properties of the atoms in a Bose-Einstein condensate. To implement the speci c polarized eld, which is needed to manipulate the scattering length, a coplanar waveguide (CPW) is designed which can produce the appropriate eld strength and orientation. This work outlines the process of designing and simulating the waveguide with the appropriate software as well as the testing of its behaviour. Additionally a short outlook on further developments and how the waveguide will be used in the experimental setup will be given. The general design of the waveguide takes the form similar to an keyhole with the central geometric element of a circle, which should produce a magnetic eld rotating in the plane parallel to the chips surface. The eective eld should mainly be a product of the near eld and be not radiated into the surroundings. Therefor two principle parameters are important to the design, the circular component of the magnetic eld as well as the S-parameter for transmission. Testing for the S-parameter is done conventionally with a vector network analyzer while the measurement of the magnetic eld requires a custom setup.
