AAS 207th Meeting, 8-12 January 2006
Session 12 Con-X Instruments and Optics
Poster, Monday, 9:20am-7:00pm, January 9, 2006, Exhibit Hall

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[12.05] Multiplexed x-ray microcalorimeters with improved energy resolution for Constellation-X

K. D. Irwin, J. A. Beall, W. B. Doriese, W. D. Duncan, L. Ferreira, G. C. Hilton, C. D. Reintsema, D. R. Schmidt, J. N. Ullom, L. R. Vale, Y. Xu, B. L. Zink (NIST)

NIST is working with NASA/Goddard Space Flight Center (GSFC) to develop multiplexed x-ray microcalorimeter arrays optimized for the Constellation-X mission. These arrays are based on superconducting transition-edge sensors (TES) read out with multiplexed superconducting quantum interference device (SQUID) amplifiers. We present recent progress in improving the x-ray energy resolution through engineering the device geometry, and present recent results with 8- and 16-channel multiplexers.

In order to achieve the ambitious x-ray energy resolution goals for the Constellation-X microcalorimeters, we have conducted extensive investigations of the high-frequency unexplained noise in TES sensors as a function of operating resistance, current density, applied magnetic field, and device geometry. Using the measured dependencies of the unexplained noise, we have optimized the design of our TES x-ray sensors and achieved FWHM energy resolutions of 2.4 eV at the 5.9 keV Mn K\alpha complex, which is a significant step towards the Constellation-X resolution goal of 2 eV at 5.9 keV.

We also present progress in the development of time-division SQUID multiplexers for the readout of large x-ray calorimeter arrays. We present results from x-ray microcalorimeters in 8- and 16-channel multiplexers. We describe the constraints on the system architecture, and present a practical design for a 32-channel MUX to be used in a kilopixel array.

Finally, we have extended this work to develop TES microcalorimeters for higher energy applications, such as the study of Ti emission lines from supernova remnants, including high-resolution velocity diagnostics. We have obtained a spectral resolving power of 4300 (energy / half-energy width) at the 103 keV Gd \gamma-ray line using a TES with a Sn absorber.

We are grateful for technical support from the NASA/GSFC microcalorimeter group, and for financial support from NASA through the Constellation-X program and Grant NDPR S06561-G.

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