Multiabsorber transition-edge sensors for x-ray astronomy

We are developing arrays of position-sensitive microcalorimeters for future x-ray astronomy applications. These position-sensitive devices commonly referred to as hydras consist of multiple x-ray absorbers, each with a different thermal coupling to a single-transition-edge sensor microcalorimeter. Their development is motivated by a desire to achieve very large pixel arrays with some modest compromise in performance. We report on the design, optimization, and first results from devices with small pitch pixels (<75 mu m) being developed for a high-angular and energy resolution imaging spectrometer for Lynx. The Lynx x-ray space telescope is a flagship mission concept under study for the National Academy of Science 2020 decadal survey. Broadband full-width-half-maximum (FWHM) resolution measurements on a 9-pixel hydra have demonstrated Delta E-FWHM = 2.23 +/- 0.14 eV at Al-K-alpha, Delta E-FWHM= 2.44 +/- 0.29 eV at Mn-K-alpha, and Delta E-FWHM = 3.39 +/- 0.23 eV at Cu-K-alpha. Position discrimination is demonstrated to energies below <1 keV and the device performance is well-described by a finite-element model. Results from a prototype 20-pixel hydra with absorbers on a 50-mu m pitch have shown Delta E-FWHM = 3.38 +/- 0.20 eV at Cr-K-alpha 1. We are now optimizing designs specifically for Lynx and extending the number of absorbers up to 25/hydra. Numerical simulation suggests optimized designs could achieve similar to 3 eV while being compatible with the bandwidth requirements of the state-of-the art multiplexed readout schemes, thus making a 100,000 pixel microcalorimeter instrument a realistic goal. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.