Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Delta E(sub FWHM) = 3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterized the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter

RESISTANCE NOISE IN HIGH-TC AND LOW-TC GRANULAR SUPERCONDUCTING FILMS

Measurements of the resistance noise in thick films of Y-Ba-Cu-0, in thick films of Bi-Sr-Ca-Cu-O, and in thin films of NbN, at the superconducting transition are reported. The transition to the R = 0 state was obtained by either changing the temperature at fixed currents or by lowering the current through the sample at fixed temperatures. In both kinds of experiments, we have observed the divergence of the power spectral density S(v)/V2 as the R = 0 state is approached. Our results are consistent with a percolative interpretation of the resistive transition of granular superconductors