Abstract

The properties of Superconducting Tunnel Junctions (STJ) make them very suitable for low light level astronomical observations. STJ detectors could be used to improve the sensitivity of such a system to be implemented on ground based telescopes. We have developed a modified version of the "SNEP" fabrication process for making Nb/Al-AlO/sub x/-Al/Nb and Ta/Al-AlO/sub x/-Al/Ta/Nb STJ's. These junctions show a very low sub-gap leakage current at 0.1 K. They use a double thin aluminum trapping layer and a Nb or Ta absorber grown epitaxially on a R-plane sapphire substrate. A new experimental set-up has been completed to achieve photon counting performances for the X-ray and for optical-near infrared wavelengths. An original, room temperature, charge sensitive preamplifier has been built for this purpose and tested with a /sup 55/Fe X-ray source. The 6 keV peak of this source can be observed in the measured spectrum. Photon counting ability in the near infrared at 0.78 /spl mu/m is also demonstrated.

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