Superconducting NbTaAlAlOxAl X-ray detectors with spatial resolution
Abstract Superconducting X-ray detectors based on SIS tunnel junctions offer potential for high spectral resolution and single photon efficiency. When used in a double junction geometry, they also offer spatial resolution needed for focal plane imaging. We are developing NbTaAlAlOxAl detectors for space-based X-ray astronomy applications. The design employs superconductor bandgap engineering for improved charge collection and adaptability for double junction geometries. For irradiation of a single junction device with 6 keV X-rays at a single location, the detectors have an energy resolution of 87 eV at 0.27 K. Initial studies of double junction detectors show a spectral resolution of 178 eV and an inferred spatial resolution of 4 μm over an effective length of 60 μm.
Superconducting Nb-Ta-Al-AlOx-Al tunnel junctions for x-ray detection
We report progress on the microlithographic fabrication of Nb-Ta-Al-AlOx-Al structures designed for x-ray detection. These structures use bandgap engineering both for quasiparticle trapping to increase the collection efficiency and to prevent quasiparticle diffusion out through the leads. Non-standard tunnel junction geometries are used to reduce the magnetic field needed to suppress the Josephson current for stable biasing. The performance of these devices as alpha particle detectors is presented.
Superconducting rhenium as absorber for thermal detectors
Abstract A preliminary unexpected result of investigations on superconductors as absorbers for composite bolometers is reported. The investigation is intended to evaluate the feasibility of a rhenium high resolution bolometer to study the β-decay spectrum of 187Re and set a limit to the antineutrino mass. 187Re, being the nuclide with the lowest known Q-value for β-decay is best suited for this purpose. The experimental results show that around 100 mK the heat capacity and the thermalization time in superconducting rhenium are incresed by a weak magnetic field. This last effect was unexpected and it is so far unexplained.