Mapping of the resistance of a superconducting transition edge sensor as a function of temperature, current, and applied magnetic field

Abstract

We have measured the resistance R(T, I, Bext) of a superconducting transition edge sensor over the entire transition region on a fine scale, producing a 4-dimensional map of the resistance surface. The dimensionless temperature and current sensitivities (α≡∂logR/∂logT|Iandβ≡∂logR/∂logI|T) of the TES resistance have been determined at each point. α and β are closely related to the sensor performance, but show a great deal of complex, large amplitude fine structure over large portions of the surface that is sensitive to the applied magnetic field. We discuss the relation of this structure to the presence of Josephson “weak link” fringes.

A Review of X-ray Microcalorimeters Based on Superconducting Transition Edge Sensors for Astrophysics and Particle Physics

“…This is partially due to the fact that the proximity effects discussed in Section 2.1 are strongly dependent on the device geometry, the transmissivity of the leads-TES interface and other parameters of the SNS structures, such as T c , and coherence length. In a series of very detailed experiments, it was shown, by Smith et al [34,110] and in later works [76,111], how the normal metal structures added to the TES, including the thermal coupling stems between TES and absorber, could dramatically change the resistive transitions shape and the current flow [112], as a complex interplay of proximity effects, non-equilibrium superconductivity, and self-induced magnetic field. An improved TES design was highly desired, in particular because the dc bias multiplexing schemes do not allow a single pixel bias optimization.…”

Mapping TES Temperature Sensitivity and Current Sensitivity as a Function of Temperature, Current, and Magnetic Field with IV Curve and Complex Admittance Measurements

“…The agreement is reasonably good for R TES > 0.3 R N . There is some scatter at small R TES /R N , but there is a great deal of structure in the derivatives there due to the interaction of self-generated B-fields and the weak-link oscillations, and these get smoothed over by the finite spacing of the IV curves, which were less densely sampled than in reference [7].…”

“…The temperature sensitivity α and current sensitivity β can be calculated from sufficiently densely-measured IV curves using measured G values to estimate the TES temperature at each point, making the necessary interpolations, and taking ratios of appropriate differences as described in reference [7]. Alternatively, we can derive α and β from fits to the complex admittance function, A(f), taken at a single operating point.…”

“…We are just starting this work, and have made maps of the R(T,I, B EXT ) surface of a small number of devices on a sufficiently fine scale that they can be differentiated everywhere to obtain α and β [7]. We are working on using complex admittance measurements instead to compute α and β more reliably without requiring such dense mapping.…”

Mitigation of the Magnetic Field Susceptibility of Transition-Edge Sensors Using a Superconducting Groundplane

“…The sensitivity to parallel magnetic fields is much smaller primarily due to the reduced cross section in this direction [15]. For perpendicular fields, only a few μT is enough to have significant impact on the individual device performance [16]. When looking at the full-array level, spatial variations of the magnetic field could be even more detrimental.…”