Today, one of the major goals of modern astronomy is the search for other habitable worlds and the presence of life on them. Crucial in this search is the atmospheric characterisation of small, rocky planets orbiting in the habitable zone around solar type stars. The LIFE initiative will be able to perform atmospheric characterisation of a sizeable subset of these planets in the mid-infrared (mid-IR) wavelength regime (5-20 m). The mid-IR is an important bandwidth as it contains some important atmospheric biosignatures. Extremely sensitive and highly efficient detectors are required to detect the faint signal from these small exoplanets. Current state-of-the-art detectors based on semiconductor technology are unable to meet these requirements. Microwave Kinetic Inductance Detectors (MKIDs) are superconducting pair-breaking detectors able of single-photon detection with no readout noise or
dark current. This makes MKIDs a promising candidate for mid-IR detectors for the LIFE initiative. In this thesis we investigate what development is necessary to meet the detector requirements set by the LIFE initiative. We also investigate how the performance of MKIDs can be reliably measured in the mid-IR.

Currently, there are no single-photon counting MKIDs designed for the mid-IR. Measurements are done with two MKID devices that originally have been designed for the near- and far-IR bandwidths. Prior to this work the near-IR detector has shown single-photon counting 1545 nm and the far-IR detector at 38 m. In this work we show the single-photon counting ability of MKIDs 3.8 and 8.5 m. This is the first time that single-photon counting has been shown at 8.5 m. The resolving power (8/?8) at 8.5 m is found to be about 4. Experiments are planned at 18.5 m for which a setup has been designed with a cryogenic black-body radiator as the source. This is the longest wavelength required for the LIFE spectrometer. We also perform an optimisation of the near-IR detector geometry to see if a realistic device can be made that is sufficiently sensitive to 18.5 m radiation. The results show that a realistic design could in theory be made but this strongly depends on how the detector is limited by the noise.

Next steps are to design a dedicated MKID for the mid-IR to determine its efficiency and dark current. This will also require us to improve the current measurement setup as measurements show that we suffer from thermal background radiation which limits the detector performance.

The Wien filter is an important part in the multi-beam inspection microscope that is being developed at the Imaging Physics research group at the TU Delft. The multi-beam inspection microscope uses an array of 20x20 parallel beams with a pitch of 1mmthat scan the sample simultaneously. This way the low throughput of current scanning electron microscopes can be increased proportional to the number of parallel beams. The Wien filter uses a magnetic field to separate the array of primary beams from the secondary beams. A design for the Wien filter is described in [6] consisting of electric and magnetic deflection arrays. In this report a first model of the magnetic deflection array is presented and tested to investigate the uniformity of the magnetic field. The magnetic field strength was computed by measuring the deflection distance caused by the field. As predicted by theory, the field has been found to scale linearly with the applied current. Current optimization was done in simulations to find the most uniform distribution of the magnetic field. Experiments showed against expectation that the uniformity of themagnetic field between slits does not increase with increasing current on the auxiliary coil while current on the main coil is kept constant. An possible explanation is provided in this report. For the model presented in this report the current in the auxiliary coil should be
set to zero in order to obtain the most uniform magnetic field. It is proposed to provide every single winding
with its own power supply so that a better uniformity might be achieved by the individual optimization of the
currents applied.