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.
Development of microcalorimeters for high resolution X-ray spectroscopy
We have been developing microcalorimeters for use in X-ray spectroscopy. These devices have very high spectral resolution (several eV) and high intrinsic quantum efficiency, making them particularly useful for astrophysical applications. Work has evolved over a 10 year period from simple proof-of-concept devices to functional arrays. An energy resolution of 7.3 eV at 6 keV has been demonstrated for the smallest absorbers used, and a resolution of ∼12 eV for devices with a pixel area of ∼1/4 mm2. Present work is focused on making 36 pixel monolithic arrays with individual pixel areas of up to ∼1 mm2. As the size of the absorbing area is increased, high spectral resolution is more difficult to achieve not only because of the increased heat capacity, but also because of problems with uniform thermalization. We have observed non-ideal effects in large absorbers that must be controlled and minimized before the fabrication of low noise, larger area microcalorimeters can be accomplished.
Reduction of Surface Flashover of the Beam Screen of the LHC Injection Kickers
The LHC injection kicker magnets include beam screens to shield the ferrite yokes against wake fields resulting from the high intensity beam. The screening is provided by conductors lodged in the inner wall of a ceramic support tube. Operation with increasingly higher bunch intensity, and narrow bunches, now requires improved ferrite screening. This will be implemented by additional conductors; however the good high-voltage behaviour of the kicker magnets must not be compromised by the supplementary screening. Extensive studies and optimisations have been carried out, to better satisfy the often conflicting requirements for low beam coupling impedance, fast magnetic field rise-time, high vacuum and good high voltage behaviour. A new configuration is proposed which reduces significantly the electric field associated with the screen conductors and the secondary electron yield of the surface of the ceramic tube. Results of high voltage test results are also presented.