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25 November 1999 Superconducting tunnel junctions as detectors for UV astronomy
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Superconducting tunnel junctions (STJ) have now reached a state of maturity where small arrays have for the first time been used in practical applications in ground based astronomy. Future generations of devices are now under construction to enhance the current capability. For example larger format arrays, higher readout speeds, and improved spectral resolution are all issues being addressed. In this paper we present specifically the performance at ultraviolet wavelengths from 100 - 500 nm of the current generation of STJ arrays based on tantalum. Recent results on such tantalum based photon counting superconducting tunnel junctions (STJ) which are now suitable for use as broad-band low resolution spectrometers for ultraviolet astronomy are presented. These STJs, operated at a temperature of approximately 0.3 K, have demonstrated a limiting resolution of approximately 8 nm at 200 nm. These devices can be designed to be extremely linear in response with photon energy while measuring the individual photon wavelength and arrival time. The quantum efficiency for single photons is over approximately 50% at approximately 200 nm. Such an STJ has been packaged into a small prototype 6 X 6 array and shown to have good uniformity of response across all pixels. Larger arrays are under development which could contribute significantly to many fields of ultraviolet astronomy being able to provide efficiently and simultaneously the broad band spectrum and photon arrival time history of every single object in the field over a very wide dynamic range. With lower energy gap superconducting materials the resolution should become higher and possibly for hafnium based devices as high as approximately 1 nm at 200 nm. Is such devices can be developed then imaging spectrometers which can simultaneously record the image and spectra of objects in a large field and therefore provide an object's red-shift may become a reality.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Peter Verhoeve, Anthony J. Peacock, Didier D. E. Martin, Nicola Rando, Abel Poelaert, and Roland H. den Hartog "Superconducting tunnel junctions as detectors for UV astronomy", Proc. SPIE 3764, Ultraviolet and X-Ray Detection, Spectroscopy, and Polarimetry III, (25 November 1999);

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