Analysis of impedance and noise data of an X-ray transition-edge sensor using complex thermal models

TL;DR

This paper analyzes the impedance and noise data of an X-ray transition-edge sensor using a detailed three-block thermal model, revealing that excess noise originates from thermal fluctuations within the device.

Contribution

It introduces a comprehensive three-block thermal model to accurately explain impedance and noise data, clarifying the physical origin of excess noise in TES detectors.

Findings

A three-block thermal model fits the data better than a two-block model.

Excess noise is identified as thermal fluctuation noise within the device.

Equations for impedance and noise in the three-block model are provided.

Abstract

The so-called excess noise limits the energy resolution of transition-edge sensor (TES) detectors, and its physical origin has been unclear, with many competing models proposed. Here we present the noise and impedance data analysis of a rectangular X-ray Ti/Au TES fabricated at SRON. To account for all the major features in the impedance and noise data simultaneously, we have used a thermal model consisting of three blocks of heat capacities, whereas a two-block model is clearly insufficient. The implication is that, for these detectors, the excess noise is simply thermal fluctuation noise of the internal parts of the device. Equations for the impedance and noise for a three-block model are also given.