Roland Hendrik den Hartog

High dynamic range interferometric observations of exozodiacal discs: performance comparison between ground, space and Antarctica

The possible presence of large amounts of exozodiacal dust around nearby main sequence stars represents a threat to the detection and characterisation of Earth-like extrasolar planets with future infrared space interferometers such as DARWIN or TPF. In this paper, we first review the current detection capabilities of ground-based infrared interferometers such as CHARA/FLUOR and the detections of hot dust that have been obtained so far around a few main sequence stars. With the help of realistic instrumental simulations, we then discuss the relative merits of various ground-based sites (temperate and Antarctic) versus space-based observatories for the detection of exozodiacal discs down to a few zodi by interferometric nulling as a preparation to future life-finding missions. In particular, we discuss the performance of four proposed nulling interferometers: GENIE, ALADDIN, PEGASE and FKSI. An optimised strategy for the characterisation of candidate DARWIN/TPF targets is finally proposed.

GENIE: High-Resolution Study of Debris Disks

Lep, using a variety of physical parameters. Both the thermal emission andthe scattered light are included in the model. Two types of grains have beenconsidered: smoothed astronomical silicates (Weingartner & Draine 2000)and cold-coagulation type grains (Li & Lunine 2003) with a porosity up to90% when the H

Quasiparticle diffusion and energy resolution in superconducting tunneling junctions

One of the factors that limits the energy resolution of superconducting tunnel junctions (STJs) as photon detectors is the spatial dependence of the response on the photoabsorption site. To assess the role of spatial inhomogeneities, we have analyzed quasiparticle (qp) diffusion processes in detail and developed a general analytical theory to describe the evolution of the qp density in an STJ. This theory accounts for (mild) non-linearity due to qp self-recombination, and includes the effects due to multiple qp tunneling, phonon coupling between the electrodes, diffusive losses into electrical connections and localized traps and losses at the edges. The theory does not require any assumptions about symmetry between base and counter electrode. We have derived an analytical model of the STJ response surface and the corresponding spectral lineshape, which allows the influence of the above features to be treated independently. We discuss two examples of the application of this model in practice and demonstrat...