The X-ray spectroscopy telescope Athena has been designed to implement the science theme "the hot and energetic universe", selected by the European Space Agency as the second large mission of its Cosmic Vision program. X-IFU, one of the two interchangeable focal plane instruments of Athena, is a high resolution X-ray spectrometer made of a large array of Transition Edge Sensors. Two options are under consideration for the X-IFU microcalorimeters: Ti/Au bilayers or Mo/Au bilayers. Here we report on our efforts to develop Mo/Au-based TES. The TES are made of high quality superconducting Mo/Au bilayers fabricated at room temperature on low stress Si₃N₄ membranes; Mo is deposited by RF magnetron sputtering and in-situ covered by a thin (15nm) Au layer deposited by DC sputtering; in a second step, the Au layer thickness is increased ex-situ by e-beam deposition, to obtain suitable resistance Rn and operation temperature values. Very sharp transitions (~few mK transition width) are obtained, with typically R_n~25mΩ and T_c~ 100-120mK for 65/215 bilayers. First simple TES designs are being tested. Also, Bi films several μm thick, intended to constitute the X-ray absorber, are fabricated by electrochemical deposition.

Date Published: 29 July 2014
PDF: 7 pages
Proc. SPIE 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 91445P (29 July 2014); doi: 10.1117/12.2056900

Published in SPIE Proceedings Vol. 9144:
Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray
Tadayuki Takahashi; Jan-Willem A. den Herder; Mark Bautz, Editor(s)