Speaker
Description
Transition-edge sensors (TESs) are thin superconducting films operated close to their critical temperature, which have been employed as micro-calorimeters with excellent intrinsic energy resolution in the detection of single photons. Recent works have explored their potential for the detection of single electrons. This research could be highly valuable for the PTOLEMY collaboration, which plans to measure low-energy electrons with a TES array in order to detect the Cosmic Neutrino Background, and to measure the mass of the neutrino. To achieve both these objectives, the energy resolution requirement of PTOLEMY is a full-width half-maximum (FWHM) of ~120 meV on electrons with a kinetic energy of 10 eV, and TESs are considered one of the possible options. The experimental setup at INRiM (Istituto Nazionale di Ricerca Metrologica), in Italy, which uses a cold electron source based on field emission from vertically-aligned carbon nanotubes, coupled with bilayer gold/titanium TES devices with a critical temperature between 80 and 90 mK, have already demonstrated to detect single electrons in the 100 eV energy range with an energy resolution compatible with that of photons of the same energy. In our latest results, we have improved on the experimental conditions so as to drastically reduce partially-absorbed events, and achieving a FWHM about 20 times better than in previous measurements. This represents a major milestone in the development of high-precision spectroscopy for low-energy electrons with TES devices. We will further discuss the next steps towards lowering the electron energy and achieving the PTOLEMY resolution goal, given the promising performance obtained with TES devices so far.