Abstract
Design of TES microcalorimeters requires a tradeoff between resolution and dynamic range. Often, experimenters will require linearity for the highest energy signals, which requires additional heat capacity be added to the detector. This results in a reduction of low energy resolution in the detector. We derive and demonstrate an algorithm that allows operation far into the nonlinear regime with little loss in spectral resolution. We use a least squares optimal filter that varies with photon energy to accommodate the nonlinearity of the detector and the non-stationarity of the noise. The fitting process we use can be seen as an application of differential geometry. This recognition provides a set of well-developed tools to extend our work to more complex situations. The proper calibration of a nonlinear microcalorimeter requires a source with densely spaced narrow lines. A pulsed laser multi-photon source is used here, and is seen to be a powerful tool for allowing us to develop practical systems with significant detector nonlinearity. The combination of our analysis techniques and the multi-photon laser source create a powerful tool for increasing the performance of future TES microcalorimeters.
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Acknowledgments
We would like to thank Sarah Busch, Simon Bandler, and Steve Smith for helpful discussions about nonlinear detector response, and Dan McCammon for a wide range of helpful discussions.
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Fixsen, D.J., Moseley, S.H., Gerrits, T. et al. Optimal Energy Measurement in Nonlinear Systems: An Application of Differential Geometry. J Low Temp Phys 176, 16–26 (2014). https://doi.org/10.1007/s10909-014-1149-x
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DOI: https://doi.org/10.1007/s10909-014-1149-x