Investigation of radiation hardness of SIS junctions for space borne radio astronomy

Abstract

Submillimeter astronomy with SIS (Superconductor-Insulator-Superconductor) mixers in space offer access to new wavelength windows and unsurpassed sensitivity. However little is known about the behavior of these devices in space. The Heterodyne Instrument (HIFI) aboard ESA's cornerstone Herschel Space Observatory (formely FIRST) satellite, scheduled for launch in 2007, will be among the first instrument using SIS technology in space. Within this context it is important to study possible radiation damage effects in SIS tunnel junctions. The particular devices used for HERSCHEL-HIFI-Band 1 (480-640 GHz) were fabricated with a new process based on negative resist E-beam lithography and very high current densities (15 kA/cm 2 ). In this paper, we report on radiation hardness tests with 10 MeV protons on the described high current density Nb/Al-AlOx/Nb junctions.