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When "Optimal Filtering" Isn't



Joseph Fowler, Bradley Alpert, W.Bertrand (Randy) Doriese, James P. Hays-Wehle, Young I. Joe, Kelsey Morgan, Galen O'Neil, Joel Ullom, Dan Schmidt, Daniel Swetz


The so-called ''optimal filter'' analysis of a microcalorimeter's x-ray pulses is statistically optimal only if all pulses have the same shape, regardless of energy. The shapes of pulses from a nonlinear detector can and do depend on the pulse energy, however. A pulse-fitting procedure that accounts for the energy dependence of the shape should therefore achieve superior energy resolution. We take a geometric view of the pulse-fitting problem and give expressions to predict how much the energy resolution stands to benefit from such a procedure. We also demonstrate the method with a case study of K-line fluorescence from several 3d transition metals. The method improves the resolution from 4.9 eV to 4.2 eV at the Cu K-alpha line (8.0 keV).
Proceedings Title
IEEE Transactions on Applied Superconductivity
Conference Dates
September 5-9, 2016
Conference Location
Denver, CO, US
Conference Title
Applied Superconductivity


Transition-edge sensors, x-ray detection, pulse analysis


Fowler, J. , Alpert, B. , Doriese, W. , Hays-Wehle, J. , Joe, Y. , Morgan, K. , O'Neil, G. , Ullom, J. , Schmidt, D. and Swetz, D. (2016), When "Optimal Filtering" Isn't, IEEE Transactions on Applied Superconductivity, Denver, CO, US, [online],, (Accessed July 18, 2024)


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Created December 7, 2016, Updated April 19, 2022