X-ray photon detection using superconducting resonators in thermal quasi-equilibrium

TL;DR

This paper demonstrates that superconducting resonators can detect X-ray photons in a thermal quasi-equilibrium state, showing potential for X-ray microcalorimetry with distinct relaxation processes and measurable sensitivity.

Contribution

It introduces the use of superconducting resonators in a thermal quasi-equilibrium mode for X-ray detection, expanding their application beyond non-equilibrium methods.

Findings

Detection of X-ray induced temperature rise and decay times.

Identification of two distinct relaxation pulses.

Measured resonator sensitivity and energy resolution.

Abstract

Superconducting resonators have to date been used for photon detection in a non-equilibrium manner. In this paper, we demonstrate that such devices can also be used in a thermal quasi-equilibrium manner to detect X-ray photons. We have used a resonator to measure the temperature rise induced by an X-ray photon absorbed in normal metal and superconducting absorbers on continuous and perforated silicon nitride membranes. We observed two distinct pulses with vastly different decay times. We attribute the shorter pulses to non-equilibrium quasiparticle relaxation and the longer pulses to a thermal relaxation process. In addition, we have measured the temperature dependence of the X-ray induced temperature rise and decay times. Finally, we have measured the resonator sensitivity and energy resolution. Superconducting resonators used in a thermal quasi-equilibrium manner have the potential to be used for X-ray microcalorimetry.