Large, Thin, and Corrugated Gold Absorbers for Transition Edge Sensor Microcalorimeters

Abstract

A sounding rocket mission studying the soft diffuse X-ray background ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; $</tex-math></inline-formula> 400 eV) needs high-resolution detectors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; $</tex-math></inline-formula> 2 eV FWHM) with a large collecting area ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) to reasonably achieve science goals. A practical number of readout channels coupled with the energy resolution requirements drives our goal to develop large (1 mm x 1 mm), thin (200 nm) gold absorbers. Our previous attempts at fabricating these absorbers showed that we needed a large number of support posts as far out as possible to keep the thin absorber from sagging and thermally shorting to the substrate. Support posts at the edge of the membrane could increase athermal phonon loss and introduce position dependence in the absorber. Both are detrimental to the detector energy resolution. Free-standing absorbers with support posts only in the center would be ideal, but these thin absorbers have an aspect ratio of a sheet of typing paper supported by 1 mm tall support posts in the center. We have been exploring adding corrugations to the absorber to mechanically stiffen it and decrease the number of support posts needed. Here, we show the results from our fabrication runs to make large, thin, corrugated absorbers and compare the efficacy of different corrugation patterns to keep a large, thin absorber flat.