Ghassan Yassin

Abstract:

Finlines are planar structures which allow broadband and low loss transition from waveguide to planar circuits. Their planar structure and large substrate makes them ideal for integration with other planar circuits and components, allowing the development of an on chip Polarimeter. We have developed a method of extending the employment of finlines to thick substrates with high dielectric constants by drilling or etching small holes into the substrate, lowering the effective dielectric constant. We present the results of scale model measurements at 15GHz and cryogenic measurements at 90GHz which illustrate the excellent performance of finline transitions with porous substrates and the suitability of this technique for extending the bandwidth of finline transitions.

Abstract:

We have fabricated TES bolometers with finline transitions for the C lOVER project. We have measured the optical response of C lOVER's first prototype 97-GHz detectors and find that they have a detection efficiency close to 100%. We have also investigated the effects of misalignment of the finline in the waveguide and of thinning the substrate. The prototype detectors have dark NEPs as low as 1.5 × 10^-17WZv-Hz and satisfy the requirement of photon-noise limited operation on C lOVER. We describe the optical tests of ClOVER's prototype 97-GHz detectors and discuss their implications for the design of the science-grade detectors.

Abstract:

CℓOVER is a multi-frequency experiment optimised to measure the Cosmic Microwave Background (CMB) polarization, in particular the B-mode component. CℓOVER comprises two instruments observing respectively at 97 GHz and 150/225 GHz. The focal plane of both instruments consists of an array of corrugated feed-horns coupled to TES detectors cooled at 100 mK. The primary science goal of CℓOVER is to be sensitive to gravitational waves down to r ∼ 0.03 (at 3σ) in two years of operations.

Abstract:

We present a novel design of a waveguide to microstrip or coplanar waveguide transition using a unilateral finline taper. The transition from the unilateral finline mode to the TEM microstrip mode is done directly, avoiding the antipodal finline tapers that have commonly been employed. This results in significant simplification of the design and fabrication, and shortening of the chip length, thereby reducing insertion loss. In this paper we shall present designs at 90 GHz that can be employed in superconducting tunnel junction mixers or Transition Edge Sensor bolometers, and scale-model measurements at 15 GHz.