Controlled Shifts of X-ray Emission Lines Measured with Transition Edge Sensors at the Advanced Photon Source

TL;DR

This paper presents a method using a synchrotron source and Transition Edge Sensors to precisely measure and characterize controlled shifts in X-ray emission lines, enhancing detector calibration and material analysis.

Contribution

It introduces a novel approach for inducing and measuring eV-scale shifts in X-ray lines using a TES array with fixed fluorescence lines for calibration.

Findings

Successfully tracked sub-resolution energy shifts in elastic scattering lines.

Demonstrated the method's applicability over a wide X-ray energy range.

Identified calibration as the current limiting factor for measurement precision.

Abstract

The measurement of shifts in the energy of X-ray emission lines is important for understanding the electronic structure and physical properties of materials. In this study, we demonstrate a method using a synchrotron source to introduce controlled eV-scale shifts of a narrow line in between fixed-energy fluorescence lines. We use this to characterize the ability of a hard X-ray superconducting Transition Edge Sensor (TES) array to measure line shifts. Fixed fluorescence lines excited by higher harmonics of the monochromatic X-ray beam are used for online energy calibration, while elastic scattering from the primary harmonic acts as the variable energy emission line under study. We use this method to demonstrate the ability to track shifts in the energy of the elastic scattering line of magnitude smaller than the TES energy resolution, and find we are ultimately limited by our calibration procedure. The method can be applied over a wide X-ray energy range and provides a robust approach for the characterization of the ability of high-resolution detectors to detect X-ray emission line shifts, and the quantitative comparison of energy calibration procedures.